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Multi-technique approach to rockfall monitoring in the Montserrat massif (Catalonia, NE Spain)
Abstract
Montserrat Mountain is located near Barcelona in Catalonia, in the northeast of Spain, and its massif is formed by conglomerate interleaved by siltstone/sandstone with steep slopes very prone to rockfalls. The increasing number of visitors in the monastery area, reaching 2.4 million per year, has highlighted the risk derived from rockfalls for this building area and also for the terrestrial accesses, both roads and the rack railway. A risk mitigation plan has been launched, and its first phase during 2014–2016 has been focused largely on testing several monitoring techniques for their later implementation. The results of the pilot tests, performed as a development from previous sparse experiences and data, are presented together with the first insights obtained. These tests combine four monitoring techniques under different conditions of continuity in space and time domains, which are: displacement monitoring with Ground-based Synthetic Aperture Radar and characterization at slope scale, with an extremely non-uniform atmospheric phase screen due to the stepped topography and atmosphere stratification; Terrestrial Laser Scanner surveys quantifying the frequency of small or even previously unnoticed rockfalls, and monitoring rock block centimetre scale displacements; the monitoring of rock joints implemented through a wireless sensor network with an ad hoc design of ZigBee loggers developed by ICGC; and, finally, monitoring singular rock needles with Total Station.
... Monitoring systems can use a single method (Boyd et al. 1973) or complex systems (Blahůt and Racek 2023, Chapter 1) use multiple monitoring methods (Janeras et al. 2017;Racek et al. 2021). Traditional methods are usually based on geotechnical in situ measurements. ...
... This application demands the use of reflective prisms. Total stations measuring campaigns are used within complex monitoring systems (Janeras et al. 2017;Corsini et al. 2013), and also Scherer and Lerma (2009) recorded an in-depth information of tachymetry. ...
... 60 m profile length (Osasan and Afeni 2010).When a profile is longer, outcomes can be biased by invar thermal expansion. When rockslide velocity is higher than wire thermal expansion bias, the profile can be longer (Janeras et al. 2017;Zangerl et al. 2010). Long profiles can be measured underground where the temperature is stable (Bhalla et al. 2005). ...
Rock mass characterization and rockfall/rock slope stability monitoring methods are one of the fastest evolving research areas in the field of geosciences. Traditionally, simple mapping, geodetical or geotechnical methods are used. The ongoing rapid development of monitoring methods is conditioned by engineering challenges when new infrastructure is nowadays being constructed in complicated geological conditions. These are represented by mountainous areas, deep gorges with steep slopes, or even active landslide sites. Traditional methods can be used within these monitoring demanding sites and bring high-quality monitoring results, sometimes with higher precision than modern state-of-art methods. This chapter reviews traditional rock slope stability monitoring methods and discusses their advantages, applicability, and strong/weak sides. Traditional methods are compared against newly introduced, modern state-of-art methods.
... Monitoring systems can use a single method (Boyd et al. 1973) or complex systems (Blahůt and Racek 2023, Chapter 1) use multiple monitoring methods (Janeras et al. 2017;Racek et al. 2021). Traditional methods are usually based on geotechnical in situ measurements. ...
... This application demands the use of reflective prisms. Total stations measuring campaigns are used within complex monitoring systems (Janeras et al. 2017;Corsini et al. 2013), and also Scherer and Lerma (2009) recorded an in-depth information of tachymetry. ...
... Monitoring of the crack displacements is a frequently-used method. It describes rock face or unstable rock slope element Spatio-temporal behavior (Bakun-Mazor et al. 2013;Janeras et al. 2017;Collins and Stock 2016). Generally, crack displacement monitoring can be used for rockfall event prediction (Zvelebil and Moser 2001;Arosio et al. 2009). ...
Landslide on a mountainous stretch of the National Highway is a serious concern because they hinder traffic. Anthropogenic activities in the large-scale excavation of the natural slope to expand the existing national highway can significantly alter the slope mass sliding properties. The present study examines the rock mass current geotechnical state and the locations of potential failures in the Imphal Jiribum national highway of (NH-37) in Manipur. Rock mass characterizations and uniaxial compression strength tests have been carried out for the entire study area. According to kinematic analysis and field observations, the study result reveals that the Nungkao landslide is unstable. Wedge collapses are dominant. The factor of safety for rock wedge failure mode has indicated stable conditions. Based on the plasticity index chart, soil samples collected from the site have lower moisture content, which indicates that the soil is of an inorganic origin. The negative (−ve) value of the liquidity index (−1.18) and the positive (+ve) value of the consistency index (3.03) infer that the slope materials remain in the solid-state or semi-solid state, which indicates the slope is stable. Safety factor calculation also shows stable soil slope conditions. However, frequent slides still occur in the area. Effective preventive measures are suggested to improve slope stability accordingly.
... Van Veen et al. [7] applied these methods to a hazardous slope that presents rockfall hazards to the CN Rail line in British Columbia, to build a database of rockfalls. Janeras et al. [20] quantified the frequency of small or even previously unnoticed rockfalls in Montserrat massif near Barcelona (NE Spain). Bonneau et al. [21] describe the rationale and consequences of measuring the dimensions of 3D rockfall objects obtained from successive point clouds, and introduce two unique algorithms to standardize the process. ...
... Section 2 exposes how these methods have been adapted to the proposed methodology, based on measuring new features that upgrade machine learning classifications. Section 3 shows the results of the study case of the Degotalls in the Montserrat massif (Barcelona, Spain), a rock cliff where the fracture pattern favors the rockfalls next to infrastructures [20]. ...
... In fact, this prior manual classification must guarantee a minimum number of clusters labeled as rockfalls. However, some scenarios in the training stage may present an imbalance between the number of clusters in each class due to the large number of "Unknown" clusters, such as in the case study of the Montserrat massif [20,57]. The number of items resulting from clustering differences, mostly consisting of the "Unknown" class (attributable to vegetation or edge effects), may range from tens to about one hundred times higher with respect to the validated "Candidate". ...
Rock slope monitoring using 3D point cloud data allows the creation of rockfall inventories, provided that an efficient methodology is available to quantify the activity. However, monitoring with high temporal and spatial resolution entails the processing of a great volume of data, which can become a problem for the processing system. The standard methodology for monitoring includes the steps of data capture, point cloud alignment, the measure of differences, clustering differences, and identification of rockfalls. In this article, we propose a new methodology adapted from existing algorithms (multiscale model to model cloud comparison and density-based spatial clustering of applications with noise algorithm) and machine learning techniques to facilitate the identification of rockfalls from compared temporary 3D point clouds, possibly the step with most user interpretation. Point clouds are processed to generate 33 new features related to the rock cliff differences, predominant differences, or orientation for classification with 11 machine learning models, combined with 2 undersampling and 13 oversampling methods. The proposed methodology is divided into two software packages: point cloud monitoring and cluster classification. The prediction model applied in two study cases in the Montserrat conglomeratic massif (Barcelona, Spain) reveal that a reduction of 98% in the initial number of clusters is sufficient to identify the totality of rockfalls in the first case study. The second case study requires a 96% reduction to identify 90% of the rockfalls, suggesting that the homogeneity of the rockfall characteristics is a key factor for the correct prediction of the machine learning models.
... A comprehensive review of remote sensing techniques for rockfall research is beyond the scope of this article, however, it is accessible in [8,10,[24][25][26]. Other remote sensing systems are reported in [24,[27][28][29][30][31]. ...
... The progressive failure at this point of the wall led to another rockfall in December 2008, which is the largest event captured by TLS (before and after scanners were available) until the present. As part of the mitigation plan, other local sites have been progressively added to the monitoring system [26], until there are currently twelve stations, from which the seven longest series are included in this study ( Figure 4). The most common period between surveys is about 6 months, although it was reduced to half for two years (2015-2016) looking for seasonal variations of rockfall activity, which was not clearly observed. ...
Quantitative hazard analysis of rockfalls is a fundamental tool for sustainable risk management, even more so in places where the preservation of natural heritage and people’s safety must find the right balance. The first step consists in determining the magnitude-frequency relationship, which corresponds to the apparently simple question: how big and how often will a rockfall be detached from anywhere in the cliff? However, there is usually only scarce data on past activity from which to derive a quantitative answer. Methods are proposed to optimize the exploitation of multi-source inventories, introducing sampling extent as a main attribute for the analysis. This work explores the maximum possible synergy between data sources as different as traditional inventories of observed events and current remote sensing techniques. Both information sources may converge, providing complementary results in the magnitude-frequency relationship, taking advantage of each strength that overcomes the correspondent weakness. Results allow characterizing rockfall detachment hazardous conditions and reveal many of the underlying conditioning factors, which are analyzed in this paper. High variability of the hazard over time and space has been found, with strong dependencies on influential external factors. Therefore, it will be necessary to give the appropriate reading to the magnitude-frequency scenarios, depending on the application of risk management tools (e.g., hazard zoning, quantitative risk analysis, or actions that bring us closer to its forecast). In this sense, some criteria and proxies for hazard assessment are proposed in the paper.
... Monitoring to understand the rockfall processes in their complexity must be composed of a wide range of sensors monitoring different variables. Such a system should be placed within active rockfall sites where continual information about the dynamic and activity is required and can be acquired (Jaboyedoff et al. 2011;Janeras et al. 2017). The first step in the final goal of understanding the rock slope destabilization process is to compare the rock slope dynamic with in-situ measured meteorological variables (D'Amato et al. 2016;Di Matteo et al. 2017 Maintenance requirements and the price of sensors can be time and financially demanding. ...
... Complex and expensive monitoring systems are deployed within known unstable rock slopes that pose a threat to critical infrastructure or urban areas. Examples of such monitoring can be Åknes rockslide in Norway (Jaboyedoff et al. 2011), Randa and Preonzo rockslides in Switzerland (Loew et al. 2012(Loew et al. , 2017, or Monsterrat rock in Spain (Janeras et al. 2017). There, the expenses for the construction and operation of the system are justified by lowering the risk of fatal failure. ...
Modern methods to characterise rock masses and monitor rockfalls and rock slope stability are evolving incredibly fast during the last decade. The rapid increase in new techniques, miniaturization, affordability, computational power, or remote sensing data availability allows deployment in more areas in higher amounts with higher frequency and accuracy of acquisition. The current rapid development of monitoring methods is also induced by engineering challenges when new infrastructures are being constructed in more complicated geological conditions, like mountainous areas or deep gorges with steep slopes. This chapter brings an overview of modern methods used for rock mass characterisation and rockfall monitoring and shows the basic needs for complex monitoring systems and data processing. Finally, it describes the main groups of monitoring methods based on cluster analysis and principal trends in research papers related to modern methods in rock mass characterisation and rockfall monitoring.
... Considering all of the available data (and newly recorded minor deformations and cracks developed during the period/process of field mapping from 2019 to 2022), future movements are expected in the Gajevo landslide area and a directly endangered area (critical zone) can be defined as the area in the vicinity of the existing head scarp, where the road and five houses are in the critical zone (house numbers [23][24][25][26][27][28][29][30][31]. This endangered area is~11,000 m 2 and encompasses both areas that are already in movement (landslide area) and the area without (major) signs of instabilities (landslide crown area). ...
... The h.r.e. from February 2014 with 85 mm of rain (in combination with snowmelt) was the main triggering factor of the Gajevo landslide. It is indicative that the other two extremes occurred when snow cover was not present, in the summer of 2016 (June, 85 mm of rain) and in the autumn of 2019 (September, 97 mm of rain), and "only" caused minor movements in the Gajevo landslide body: the measured deformations on houses on Gajevo Street were within centimetres range [23]. From the available data, it can be concluded that: (i) the frequency of h.r.e. and the amount of precipitation per event has increased, and extreme events are continuing to happen; (ii) the intensity and timing of these events cannotbe predicted; (iii) from the aspect of slope stability, extreme events are important; and (iv) it is reasonable to expect an extreme event to occur in combination with snowmelt in the coming years, i.e., the reactivation of the Gajevo landslide. ...
The Gajevo landslide is located in a hilly area of northern Croatia, where numerous landslides endanger and damage houses, roads, water systems, and power lines. Nevertheless, available landslide data are relatively scarce. Therefore, the Gajevo landslide location was chosen for detailed research and the development of a typical landslide model for this area. During initial research, the geographical and geological settings were reviewed and historical orthophotos were analysed. Due to the complexity and vulnerability of the area, the location required detailed investigations and the integration of multi-level data: remote (based on high-resolution LiDAR data) and field landslide mapping were performed and a map of the landslide area was developed. Precipitation data were reviewed, while shallow boreholes with material sampling and geophysical measurements provided information on material characteristics and 3D (depth) insight. As a result, knowledge was gained about material resistivity and composition along with the depth of sliding surfaces, and an engineering geological map of the Gajevo landslide area with the landslide and directly endangered areas marked was developed to be used by the local community in landslide risk assessment. As it is reasonable to expect that an extreme rainfall event will occur in combination with snowmelt in the coming years, resulting in the reactivation of Gajevo landslide, further research and continuous landslide monitoring are recommended.
... The joint systems present and their density, define the blocks susceptible to fall and therefore control the size of the blocks and the magnitude of the rockfalls. From lower to higher volume, it starts with the disaggregation of pebbles from the conglomerate (M3); as the second group (M2) we distinguish the slabs and plates related to physical weathering; and finally, monolithic rock masses delimited by widely spaced joints with very high persistence, (M1) (Janeras et al., 2017). ...
... The Montserrat massif is under progressive surveillance with a wide range of methods, which are described in Janeras et al., 2017. From manual and point-based techniques to automatic and continuous systems are in use in the whole area in order to manage the high geological risk over the infrastructures and the visitors. ...
Rockfalls are fast slope instabilities frequent in mountainous areas, which cause damage in infrastructures (roads and railways), buildings, vehicles and people. Nowadays, several continuous and discontinuous techniques are available to monitoring the prone areas in order to manage the associated risk. One side task is to detect changes in the source zones (rock cliffs with recurrent events) in order to assess the rockfall activity and calibrate the Magnitude-Frequency curves. Long range and high precision Terrestrial Laser Scanning (TLS) is currently used for this purpose, sometimes in combination with high-resolution pictures taken from UAV or from the ground (with a GigaPan setup, for instance). Some detected changes along time may correspond to precursory displacements while others are due to blocks detached from the cliffs. In our contribution, we present the use of the aforementioned geomatic techniques (TLS and GigaPan) within several algorithms /strategies (Cloud to Cloud, Cloud to Mesh and M3C2) inside some two commercial computer programs and open source program in order to detect and measure the differences along the successive field campaigns. This work has being carried out within the frame of the GeoRisk research project, with field data from the ICGC. In particular, we test the strategies in three sites in the Montserrat Massif (Spain)-Mirador de l'Oliver, Canal dels Aritjols and Mirador dels Apòstols-during four measuring epochs along 2019-2021. The results show that rock volumes as small as 0.001 m 3 can be detected in a regular basis.
... The rock slope stability is crucially influenced by both endogenous rock properties and exogenous factors (D'Amato et al., 2016, Selby 1980. The rock physical properties are well known and numerous laboratory experiments and theoretical works exist in the field, however, there are very few in-situ experiments that would deal with real-world time and space scales (Fantini 25 et al., 2016;Bakun-Mazor et al., 2013Janeras et al., 2017;Marmoni et al., 2020) Thermal expansion and frost action are the main exogenous physical processes of the mechanical weathering of the rock surface, which together with chemical weathering ultimately results into a weakening of the rocks slopes and lowering their stability (Gunzburger et al., 2005, Vespremeanu-Stroe andVasile, 2010;do Amaral Vargas et al., 2013;Draebing, 2020). The loss of stability, caused by repeated changes in the stress field inside the rock eventually leads to a rockfall, one of the fastest et al., (2010) presented a review of monitoring techniques for open-pit mine walls monitoring. ...
... To compute the radiation balance of a rock face, it is necessary to measure both incoming and reflected radiation. For this 140 purpose, a set of pyranometers is used (Gunzburger and Merrien-Soukatchoff, 2011;Janeras et al., 2017;Vasile and Vespremeanu-Stroe, 2017). Our monitoring system uses two pyranometers placed perpendicular to the rock face, one facing the rock surface while the other the sky hemisphere. ...
This article describes an innovative, complex and affordable monitoring system designed for joint observation of environmental parameters, rock block dilatations and temperature distribution inside the rock mass with a newly designed 3-meter borehole temperature sensor. Global radiation balance data are provided by pyranometers. The system introduces a novel approach for internal rock mass temperature measurement, which is crucial for the assessment of the changes in the stress field inside the rock slope influencing its stability. The innovative approach uses an almost identical monitoring system at different sites allowing easy setup, modularity and comparison of results. The components of the monitoring system are cheap, off-the-shelf and easy to replace. Using this newly designed system, we are currently monitoring three different sites, where the potential rock fall may endanger society assets below. The first results show differences between instrumented sites, although data time-series are relatively short. Temperature run inside the rock mass differs for each site significantly. This is very likely caused by different aspects of the rock slopes and different rock types. By further monitoring and data processing, using advanced modelling approaches, we expect to explain the differences among the sites, the influence of rock type, aspect and environmental variables on the long-term slope stability.
... The use of systems aimed at monitoring the slope stability is becoming a standard practice to assess and prevent geological and geotechnical hazards and plan effective actions for hazard analysis and risk mitigation. Several on-site cliff monitoring systems are operative in mountainous environments (Pecoraro et al., 2018), as for example in the Swiss Alps (Spillmann et al., 2007), Bohemia (Zvelebill and Moser, 2001), Spain (Janeras et al., 2017) and Northern Apennines (Salvini et al., 2015). These systems have the purpose of detecting and measuring small-scale rock deformations that can be regarded as precursors of slope failures. ...
... The direct result of heating rock is expansion, a process well studied and quantified in several environmental conditions (Chau and Shao, 2006;Collins and Stock, 2016;Eppes, 2016;Richter and Simmons, 1974). Cumulative fracture growth and opening can occur under typical present-day meteorological conditions in many settings (Eppes and Keanini, 2017;Lamp et al., 2017). Several diurnal and seasonal cycles of heating and cooling may lead to deformation and crack opening and propagation. ...
Along the coastline of the Phlegraean Fields volcanic district, near Naples (Italy), severe retreat processes affect a large part of the coastal cliffs, mainly made of fractured volcanic tuff and pyroclastic deposits. Progressive fracturing and deformation of rocks can lead to hazardous sudden slope failures on coastal cliffs. Among the triggering mechanisms, the most relevant are related to meteorological factors, such as precipitation and thermal expansion due to solar heating of rock surfaces. In this paper, we present a database of measurement time series taken over a period of ∼4 years (December 2014–October 2018) for the deformations of selected tuff blocks in the Coroglio coastal cliff. The monitoring system is implemented on five unstable tuff blocks and is formed by nine crackmeters and two tiltmeters equipped with internal thermometers. The system is coupled with a total weather station, measuring rain, temperature, wind and atmospheric pressure and operating from January 2014 up to December 2018. Measurement frequencies of 10 and 30 min have been set for meteorological and deformation sensors respectively. The aim of the measurements is to assess the magnitude and temporal pattern of rock block deformations (fracture opening and block movements) before block failure and their correlation with selected meteorological parameters. The results of a multivariate statistical analysis of the measured time series suggest a close correlation between temperature and deformation trends. The recognized cyclic, sinusoidal changes in the width (opening–closing) of fractures and tuff block rotations are ostensibly linked to multiscale (i.e., daily, seasonal and annual) temperature variations. Some trends of cumulative multi-temporal changes have also been recognized. The full databases are freely available online at: https://doi.org/10.1594/PANGAEA.896000 (Matano et al., 2018) and https://doi.org/10.1594/PANGAEA.899562 (Fortelli et al., 2019).
... Rock slope monitoring using terrestrial close-range remote sensing has undergone rapid development in the past decade as sensor technology and processing techniques have become more accurate and costefficient Eltner and Baumgart, 2015). Some directions of recent research have included the use of Light Detection And Ranging (LiDAR) and photogrammetric techniques to derive rockfall frequency-magnitude relationships (Guerin et al., 2013;Lato et al., 2015;Janeras et al., 2017;van Veen et al., 2017;Williams et al., 2018;Matsuoka, 2019;Gilham et al., 2019) and anticipate rockfalls by means of detecting precursor events (Royán et al., 2014;Kromer et al., 2015). Other emerging applications include automatic discontinuity set extraction (Santana et al., 2012;Ge et al., 2018;Zhang et al., 2018;Li et al., 2019) and semi-automated characterization of failure modes (Matasci et al., 2018). ...
... The CANUPO software (Brodu and Lague, 2011) implemented in Cloud-Compare (Girardeau-Montaut, 2018) offers an easy-to-use machine learning solution to the classification of point clouds based on their geometry characteristics. CANUPO has been used in rock slope monitoring studies (Janeras et al., 2017;Bonneau and Hutchinson, 2018) and in geomorphology and remote sensing applications more generally (Eltner and Baumgart, 2015;Magtalas et al., 2016). It is now common for an automatic classifier to be applied for vegetation, whether machine learning based or using some other filtering criteria (Williams et al., 2018), and manual tools are then used to remove other unwanted areas that are unable to be identified automatically. ...
High-resolution remote monitoring of slopes using terrestrial LiDAR and photogrammetry is a valuable tool for the management of civil and mining geotechnical asset hazards, but accurately classifying regions of interest in the data is sometimes a difficult and time-consuming task. Filtering unwanted areas of a point cloud, such as vegetation and talus, is often a necessary step before rockfall change detection results can be further processed into actionable information. In addition, long-term monitoring through seasonal vegetation changes and snow presents unique challenges to the goal of accurate classification in an automated workflow. This study presents a Random Forest machine learning approach to improve the classification accuracy and efficiency of terrestrial LiDAR monitoring of complex natural slopes. The algorithm classifies points as vegetation, talus, snow, and bedrock using multi-scale neighborhood geometry, slope, change, and intensity features. The classifier was trained on two manually labeled scans from summer and winter, then tested on three other unseen times. We find that F Score generally remains above 0.9 for talus and vegetation, and above 0.95 for bedrock and snow, indicating very high accuracy and an ability to adapt to changing seasonal conditions. In comparing this approach to CANUPO, an existing classification tool, we find our approach to be generally more accurate and flexible, at the expense of increased complexity and computation time. Comparisons with manual masking and a hybrid approach indicate that a machine learning solution is useful primarily in cases of rapidly changing rock slopes or in climates with significant seasonal variability and snow.
... rockfall) between sequential TLS scans. The location, volume and dimensions of rockfall on the slope can be calculated and populated into a database, as demonstrated by Rosser et al. (2007), Guerin et al. (2014), Tonini and Abellan (2014), van Veen et al. (2017), Janeras et al. (2017) and Williams et al. (2018). In several of these studies smaller magnitude rockfalls have been identified, which are often not observed during 15 field inspections performed from the base of the slope. ...
... ,Carrea et al. (2015),Janeras et al. (2017), van Veen et al. (2017 to semi-automatically identify rockfall locations and extract information related to the dimensions of each rockfall event is implemented. A generalized rockfall extraction process is illustrated in the flow chart inFig. 5. ...
Rockfall is a complex natural process that can present risks to the effective operation of infrastructure in mountainous terrain. Remote sensing tool and techniques are rapidly becoming the state of practice in the characterization, monitoring and management of these geohazards. The aim of this study is to address the methods and implications of how the dimensions of 3-dimensional rockfall objects, derived from sequential terrestrial laser scans (TLS), are measured. Previous approaches are reviewed, and two novel algorithms are introduced in an attempt to standardize the process. The approaches are applied to a set of synthetic rockfall objects generated in the open-source software package Blender. In addition, a database of close to 5000 rockfalls is presented derived from sequential TLS monitoring in the White Canyon, British Columbia, Canada. This study illustrates that the method in which the rockfall's dimensions are calculated has a significant impact on how the shape of a rockfall object is classified. This has implications for rockfall modelling as the block shape is known to influence rockfall runout.
... Seismic monitoring is a valuable tool for detecting and estimating the volume of rockfalls (Deparis et al., 2008;Feng et al., 2021;Hibert et al., 2017;Hibert et al., 2014;Hibert et al., 2011;Li et al., 2023;Saló et al., 2018;Vilajosana et al., 2008). Compared to techniques like terrestrial laser scanning, video imaging, and geographic information systems (Abellán et al., 2009;Janeras et al., 2017;Lan et al., 2007;Youssef et al., 2007), seismic monitoring enables nearly continuous detection regardless of weather conditions. This supports developing databases to improve understanding of rockfall behavior (Le Roy et al., 2019;Yan et al., 2019). ...
... In heavy rainfall conditions, the frequency and intensity of landslides and collapses on slopes are higher (Chen et al., 2023;Jones and Preston, 2012;Wang et al., 2015). Research on landslides and collapses mainly focuses on the mechanisms of their occurrence (Derbyshire, 2001;Zhang et al., 2018), the distribution characteristics of landslides under heavy rainfall Guo et al., 2019;Luo et al., 2023;McGuire et al., 2016;Tasser et al., 2003), the relationship of landslides and collapses with their influencing factors (De Rose, 2013;Zhou et al., 2016), the effects of landslides and collapses on watershed erosion, geomorphic features, and river sediment (Fan et al., 2021;Keefer and Larsen, 2007;Xu et al., 2017), and the monitoring and early warning of landslides and collapses caused by gravity erosion (Broeckx et al., 2020;Janeras et al., 2017;Tu et al., 2009). However, studies on soil clods and deposits generated by landslides and collapses are rare and mainly focus on the morphological characteristics of the accumulation body and their relationship with debris flows (Collins and Znidarcic, 2004;Ma et al., 2018;Ni et al., 2012;Peng et al., 2015;Tang et al., 2009) and aspects of the relationship between landslide accumulation and sediment connectivity (Yan et al., 2022). ...
The occurrence of a peculiar phenomenon called “soil balls” was observed in Dingbian County, northern Loess
Plateau, due to an extremely heavy rainstorm on July 10, 2022. Determining the distribution characteristics and
formation of these soil balls is crucial for enriching the knowledge and the precise prevention and control of soil
erosion on the Loess Plateau. This research is particularly significant in studying the off-site effects of soil erosion
caused by rainstorm and flooding disasters. This study conducted a comprehensive analysis through field
investigation and drone aerial photography in the three dam-controlled watersheds selected. The results showed
that the soil balls originated from the soil clods generated by landslides and collapses that occurred within the
watersheds during heavy rainstorms. Under the action of hyperconcentrated flows, the soil clods were transported
downstream. The size of the soil balls is mainly in the range of 20–60 cm in diameter, accounting for 81%
of the total soil balls in the dam lands, with significant differences in the morphology at different locations within
a dam land region. The average area density and volume density of soil balls in the dam lands of the watersheds
are 0.13–0.25 m2 m 2 and 0.05–0.11 m3 m 2, respectively. In each watershed, the area density and volume
density of the soil balls exhibit the following order: one-third of the dam land nearest from the dam wall > the
middle one-third of the dam land > one-third of the dam land furthest the dam wall. The total erosion intensity of
landslides and collapses in the three watersheds was 18,730, 5,213, and 9,879 m3 km 2, respectively. The
sediment transport ratio of landslides and collapses expressed by the soil balls in the dam land is at least 4–10%.
The study also indicated that the volume of landslides and collapses, the shape coefficient of the watershed, the
density of the confluence paths, and the peak discharge had a significant impact on the volume density distribution
of the soil balls in the dam lands. We recommend implementing certain measures in similar watersheds,
including converting steep slopes into terraced fields or grasslands, constructing water storage and drainage
facilities, building energy dissipation measures in channels, and reinforcing check dams, to reduce the risk of soil
ball events occurring under heavy rainstorm conditions, and protect the ecological environment on the Loess
Plateau.
... Multi-technological monitoring approaches can be beneficial for risk assessment. In [110], the authors presented a mixed system located in the Montserrat Massif, Catalonia, Spain. A large rocky wall is located above an inhabited area, posing a threat to the population. ...
Rockfalls and landslide events are caused by different factors among which are included geomorphological and climatic factors and also human interaction. Therefore, the economic and social impacts can be significant and the remote monitoring of such hazards has become an essential topic in various applications. Wireless sensor networks (WSNs) are well suited for the deployment of monitoring systems, benefiting from the different technologies and topologies that are available and evolving nowadays. This review paper aims to summarize and overview the up-to-date state of the art of rockfall and landslide monitoring systems based on WSNs. The implementation and methods were analyzed for each solution, along with the system architecture and relevant hardware aspects. All the retrieved data were used to analyze the current trends and future possibilities in the field of WSN geohazard monitoring.
... In the specific field of rockfall monitoring and management, the three-dimensional models obtained with all these techniques are used to identify potential rockfall sources (Albarelli et al., 2021), monitoring displacements to predict future events (Janeras et al., 2016) and quantifying rockfall activity for obtaining magnitude frequency curves (Williams et al., 2018). ...
When monitoring deformations in natural hazards such as rockfalls and landslides, the use of 3D models has become a standard. Several geomatic techniques allow the generation of these models. However, each one has its pros and cons regarding accuracy, cost, sample frequency, etc. In this contribution a fixed-location time lapse camera system for continuous rockfall monitoring using photogrammetry has been developed as an alternative to Light Detection and Ranging (LiDAR) and ground-based interferometric synthetic-aperture radar (GB-InSAR). The usage of stereo photogrammetry allows the obtention of 3D points clouds at a low cost and with a high sample frequency, essential to detect premonitory displacements. In this work the designed system consists of three digital single-lens reflex (DSLR) cameras which collect photographs of the rock slope daily controlled by a Raspberry Pi computer using the open-source library gPhoto2. Photographs are automatically uploaded to a server using 3G network for processing. This system was implemented at Castellfollit de la Roca village (Girona province, Spain), which sits on a basaltic cliff that has shown significant rockfall intensity in recent years. The 3D models obtained will allow monitoring rockfalls frequency, premonitory displacements, and calculate the erosion rate of the slope. All technical decisions taken for the design and implementation on this specific site are discussed and first results shown.
... Records from these devices are affected by temperature changes giving rise, due to material's thermal dilatancy, to opening-closing cycles in the time series that can mask significant and worrisome small irreversible displacements (Weber et al. 2017;Janeras et al. 2017;Mulas et al. 2020). To separate these reversible (elastic) components from the signals and quantify the irreversible (plastic) displacements, Weber et al. (2017) have proposed a linear fit method between temperature and fracture opening. ...
Long-term monitoring of structural movements in historic buildings and heritage sites allows assessing their stability and
recognizing damages that require intervention. The Punta Begoña Galleries, built in the earlier part of the twentieth century,
present pioneering techniques in the use of reinforced concrete in building construction. They stand directly over a coastal
cliff, and their recovery requires first to guarantee their stability, while maintaining their historic and patrimonial values.
Thus, with the goal of analyzing their global stability, as well as the extent of the observed damages, we implemented a
motion monitoring network that includes three boreholes for extensometric control, an inclinometer, and five crack gauges
(crackmeters). This monitoring was complemented with the recording of hydrometeorological variables at the surface and
in four piezometers. The spectral analysis of the signals of movements was performed by introducing the use of the Lomb-
Scargle (LS) periodogram, which is particularly well-suited for the analysis of unevenly spaced time series. This analysis
allowed us to differentiate the reversible seasonal elastic components of the records and to recognize the irreversible longterm
plastic displacements, which highlight the sectors with active instability. In our case, the identified damages are related
to two local problems of building support. Even though the irreversible component of the displacement after seasonal sinusoidal
detrending is small (with maximums up to 0.12 mm/year), it does imply a dynamic plastic deformation, which calls
for the need to adopt structural stabilization measures.
... The massif has stepped slopes where vertical cliffs alternate with steep slopes. The failure processes and mechanisms are described in [59]. This geometry combined with the large number of visitors (around 3.5 million per year) depicts a high-risk scenario. ...
In the last two decades, both the amount and quality of geoinformation in the geosciences field have improved substantially due to the increasingly more widespread use of techniques such as Laser Scanning (LiDAR), digital photogrammetry, unmanned aerial vehicles, geophysical reconnaissance (seismic, electrical, geomagnetic), and ground-penetrating radar (GPR), among others. Furthermore, the advances in computing, storage and visualization resources allow the acquisition of 3D terrain models (surface and underground) with unprecedented ease and versatility. However, despite these scientific and technical developments, it is still a common practice to simplify the 3D data in 2D static images, losing part of its communicative potential. The objective of this paper is to demonstrate the possibilities of extended reality (XR) for communication and sharing of 3D geoinformation in the field of geosciences. A brief review of the different variants within XR is followed by the presentation of the design and functionalities of headset-type mixed-reality (MR) devices, which allow the 3D models to be investigated collaboratively by several users in the office environment. The specific focus is on the functionalities of Microsoft’s HoloLens 2 untethered holographic head mounted display (HMD), and the ADA Platform App by Clirio, which is used to manage model viewing with the HMD. We demonstrate the capabilities of MR for the visualization and dissemination of complex 3D information in geosciences in data rich and self-directed immersive environment, through selected 3D models (most of them of the Montserrat massif). Finally, we highlight the educational possibilities of MR technology. Today MR has an incipient and reduced use; we hope that it will gain popularity as the barriers of entry become lower.
... Rockfall disaster are a great threat to people's lives and property due to its high energy, sudden occurrence, and early warning difficulties (Budetta and Santo, 1994;Janeras et al. 2017;Sun et al. 2021;Yan et al. 2022;Yu et al. 2018;Zhang et al. 2015;Zheng et al. 2018). Especially after Wenchuan earthquake, rockfall disaster had happened frequently in western China, making it the third major geological disaster area in terms of landslide and debris flow (Ji et al. 2009;Corominas et al. 2017;Mote et al. 2019;Pradhan and Fanos 2017). ...
Given the limited dissipating effect and high construction costs of traditional sand cushion in shed, this paper proposes to partially replace the sand with waste tennis balls to solve the problem of poor impact resistance of sand cushion. Tests of the impact of rockfall on the waste tennis ball-sand composite cushion were carried out exploring the dissipation effect controlled for the following: height of the rockfall, average gas content of the tennis balls, distribution density, whether the tennis ball gaps were filled with sand, and prevalence and position of tennis balls. According to the results, when a steel plate is added above the composite cushion to isolate the river sand and the tennis balls, the peak of reaction force and impact force decreased by 62% and 72%, respectively, and the dissipating effect of the composite cushion is significantly improved. More specifically, the energy dissipation of tennis cushion outperforms the traditional one with an increase of falling height, and the peak value of reaction force and impact force decrease by up to 23% and 14%, respectively. Moreover, under the same impact energy, the dissipating effect of the tennis ball-sand composite cushion gradually increases with the reduction of the gas content of the tennis ball and the distance between the tennis balls; 25% gas content and 5 cm distance have the best energy dissipation effect. The research results can provide new solutions for the structural design of cushion and the reuse of used tennis balls.
... The interest for this case is the rockfall risk on infrastructures and buildings to be managed according to natural and cultural heritage preservation besides the touristic activities. TLS available data cover more than 12 years of surveys in several scanner stations at different altitude and aspect of the mountain slopes (Table 1) (Janeras et al., 2017). The historical and observational inventory has 205 events recorded from 1546 to present, ranging from 0.001 to 2160 m 3 . ...
Hazard scenarios are defined by a representative event of a certain magnitude, which corresponds to a frequency of occurrence or annual probability. In rockfall, scenario magnitude is identified by the total volume detached. Therefore, in diffuse hazard assessment it is crucial to fit this relationship magnitude/frequency, called McF, where cumulated frequency is quoted in spatial & temporal terms. Inventories are the classical source of data to deal with this objective. Last decade, TLS or digital photogrammetry monitoring came to offer a complementary approach. The samples obtained by the two methods have a specific coverage and each has its own lack of information that can be compensated together.
... The integration of multi-technique results has proved to be an effective procedure for a comprehensive view of the geometry and kinematics of slope movements, as evidenced by recent works: e.g. Janeras et al. (2017); Peduto et al. (2021); Cenni et al. (2021). For our case of study, the selected techniques provided valuable information on the El Arrecife Landslide displacement rate at very different time scales. ...
When an active landslide is first identified in an artificial reservoir, a comprehensive study has to be quickly conducted to analyse the possible hazard that it may represent to such a critical infrastructure. This paper presents the case of the El Arrecife Landslide, located in a slope of the Rules Reservoir (Southern Spain), as an example of geological and motion data integration for elaborating a preliminary hazard assessment. For this purpose, a field survey was carried out to define the kinematics of the landslide: translational in favour of a specific foliation set, and rotational at the foot of the landslide. A possible failure surface has been proposed, as well as an estimation of the volume of the landslide: 14.7 million m3. At the same time, remote sensing and geophysical techniques were applied to obtain historical displacement rates. A mean subsidence rate of up to 2 cm/yr was obtained by means of Synthetic Aperture Radar Interferometry (InSAR) and Ground Penetrating Radar (GPR) data, during the last 5 and 22 years, respectively. The Structure-from-Motion (SfM) technique provided a higher rate, up to 26 cm/yr during the last 14 years, due to compaction of a slag heap located within the foot of the landslide. All of this collected information will be valuable to optimise the planning of future monitoring surveys (i.e. Differential Global Positioning Systems, inclinometers, ground drilling and InSAR) that should be applied in order to prevent further damage on the reservoir and related infrastructures.
... The integration of multi-technique results has proved to be an effective procedure for a comprehensive view of the geometry and kinematics of slope movements, as evidenced by recent works: e.g. Janeras et al. (2017); Peduto et al. (2021); Cenni et al. (2021). For our case of study, the selected techniques provided valuable information on the El Arrecife Landslide displacement rate at very different time scales. ...
[See the full-text in the following link: https://rdcu.be/cyFI0]. When an active landslide is first identified in an artificial reservoir, a comprehensive study has to be quickly conducted to analyse the possible hazard that it may represent to such a critical infrastructure. This paper presents the case of the El Arrecife Landslide, located in a slope of the Rules Reservoir (Southern Spain), as an example of geological and motion data integration for elaborating a preliminary hazard assessment. For this purpose, a field survey was carried out to define the kinematics of the landslide: translational in favour of a specific foliation set, and rotational at the foot of the landslide. A possible failure surface has been proposed, as well as an estimation of the volume of the landslide: 14.7 million m3. At the same time, remote sensing and geophysical techniques were applied to obtain historical displacement rates. A mean subsidence rate of the landslide around 2 cm/year was obtained by means of synthetic aperture radar interferometry (InSAR) and ground-penetrating radar (GPR) data, during the last 5 and 22 years, respectively. The structure-from-motion (SfM) technique provided a rate up to 26 cm/year during the last 14 years of a slag heap located within the foot of the landslide, due to compaction of the anthropical deposits. All of this collected information will be valuable to optimise the planning of future monitoring surveys (i.e. differential global positioning systems, inclinometers, ground drilling, and InSAR) that should be applied in order to prevent further damage on the reservoir and related infrastructures.
... The availability of adequate and relevant data is a prerequisite for developing a well-generalized and robust MLA. To date, research at the intersection of machine learning and rock engineering has included predicting: rock mass properties (Sklavounos and Sakellariou 1995;Song et al. 2015), constitutive behaviour (Millar and Clarici 2002;Kumar et al. 2013), slope stability (Kumar and Samui 2014;Janeras et al. 2017;Ferentinou and Fakir 2018), tunnel performance (Leu et al. 2001;Bizjak and Petkovšek 2004;Sun et al. 2018;Qi et al. 2018), rock bursts (Ribeiro et al. 2017;Pu et al. 2018), and blasting (Dong et al. 2011;Liu and Liu 2017). These studies have been completed using a variety of MLAs, including Artificial Neural Networks (ANNs), a variation of which will be used in the present research. ...
As underground instrumentation improves and the storage of large volumes of data becomes more cost effective, the rock engineering community has access to larger datasets than ever before. Machine learning algorithms (MLAs) present an opportunity to uncover nuanced rock mass deformation mechanics more efficiently than conventional data analysis tools, resulting in increased reliability of underground excavations. MLAs require appropriate pre-processing of inputs as well as ground truth validation of outputs. Convolutional Neural Networks (CNNs) are an MLA that allow for the preservation of spatial and temporal dependencies within a dataset. CNNs were developed for image recognition and segmentation, such as video processing, and are efficient at analyzing sequential snapshots of an excavation as the environmental and in-situ factors change. Herein a CNN is developed for Cigar Lake Mine, Saskatchewan, Canada, to predict tunnel liner yield. The mine experiences a complex time-dependent ground squeezing behaviour resulting from the poor geological conditions and the artificial ground freezing implemented to stabilize the ore cavities and to control ground water during the ore extraction process. A sensitivity analysis of the CNN training parameters, called hyperparameters, is completed to optimize the final CNN performance. Hyperparameters analyzed include: the amount of training data, the convolutional filter size, and the error weighting scheme. Two final models are developed, one balanced model able to accurately predict tunnel liner yield across all classes of severity, and one targeted model that is calibrated to predict the higher classes of tunnel liner yield particularly well. Model results demonstrate that the CNN is a promising tool for preserving the spatial and temporal dependencies between input variables, and for predicting tunnel liner yield. This is a novel approach for geomechanical datasets. In combination, the two final CNNs achieve a prediction precision of > 87% across all classes and a recall of up to 99.9% for the higher yield classes. The activation strengths of the inputs were studied, and it was determined that the primary installed support class is the most dominant predictor of tunnel liner yield.
... Therefore their impact energy and the associated hazard can reach very high values [7][8][9][10][11][12][13]. According to [14], along the Italian mountain ranges (Alps and Apennines), fast moving landslides such as rockfalls caused the largest number of deaths. As demonstrated in recent studies [15][16][17][18][19][20][21][22][23], surveying and monitoring activities play a key role in rockfall hazard assessment and are therefore of paramount importance for the preservation of human life. As rockfalls occur in very steep slopes sometimes showing limited precursor signals [24][25][26][27][28][29], their investigations, as well as their prediction and stabilisation, could face many difficulties [30]. ...
Nowadays the use of remote monitoring sensors is a standard practice in landslide characterization and monitoring. In the last decades, technologies such as LiDAR, terrestrial and satellite SAR interferometry (InSAR) and photogrammetry demonstrated a great potential for rock slope assessment while limited studies and applications are still available for ArcSAR Interferometry, Gigapixel imaging and Acoustic sensing. Taking advantage of the facilities located at the Poggio Baldi Landslide Natural Laboratory, an intensive monitoring campaign was carried out on May 2019 using simultaneously the HYDRA-G ArcSAR for radar monitoring, the Gigapan robotic system equipped with a DSLR camera for photo-monitoring purposes and the DUO Smart Noise Monitor for acoustic measurements. The aim of this study was to evaluate the potential of each monitoring sensor and to investigate the ongoing gravitational processes at the Poggio Baldi landslide. Analysis of multi-temporal Gigapixel-images revealed the occurrence of 84 failures of various sizes between 14–17 May 2019. This allowed us to understand the short-term evolution of the rock cliff that is characterized by several impulsive rockfall events and continuous debris production. Radar displacement maps revealed a constant movement of the debris talus at the toe of the main rock scarp, while acoustic records proved the capability of this technique to identify rockfall events as well as their spectral content in a narrow range of frequencies between 200 Hz to 1000 Hz. This work demonstrates the great potential of the combined use of a variety of remote sensors to achieve high spatial and temporal resolution data in the field of landslide characterization and monitoring.
... The actual installation depends not only on the site, but also on the level of risk and the available budget. [26], systems are classified according to their continuity in the Spatial and Temporal domain. Distributed Fiber Optics is in red because it has not yet been applied. ...
Works carried out to monitor the displacements of the Vallcebre landslide (Pyrenees range, NE of Spain) since 1987 are presented. The landslide, which extends over an area of about 0.8 km2 and affects more than 20 × 106 m3, has experienced displacements of up to one meter per year in some points and periods. It has been periodically monitored since 1987, using a wide range of surface and in-hole techniques: triangulation with theodolite, Terrestrial Photogrammetry, Electronic Distance Measurement, GNSS-GPS, inclinometers, wire extensometers, piezometers, DInSAR (satellite) and GBSAR (terrestrial). The results obtained using new techniques are compared with those obtained with GNSS-GPS and a wire extensometer, and checked against fixed stable points. From this comparison, we conclude that even though wire extensometers and inclinometers may have the highest precision, in practice, all systems play potentially valuable roles in providing meaningful data for monitoring at different study stages. In the near future, we envisage the installation of a Distributed Fiber Optic array to monitor the risk with a certain space and time continuity. After the evaluation of the precision and advantages of the different methods, the complementary use of some of them is strongly recommended.
... In the long term, thermal dilatation can lead to irreversible movements and block destabilization (Bakun Mazor et al. 2013;Collins and Stock 2016). The temperature effect is usually measured directly using temperature sensors placed on the rock surface, or meteorological stations placed near the rock slope, whether dilatations of blocks are measured on discontinuities that limit the particular blocks (Boyd et al. 1973;Fantini et al. 2016;Janeras et al. 2017). However, this approach is limited to single-point measurement of rock temperature and there is no information on its spatial distribution over the whole rock mass. ...
Results from a 24-hour time-lapse IR camera monitoring experimental study performed on a rock mass in the city of Prague are presented. The thermal images were processed and analysed. Acquired temperatures were coupled with information from crack meters monitoring of an unstable block. It has been shown that it is feasible to directly observe the thermoelastic wave on the monitored block. Correlations of movements with monitored temperatures showed that the rock surface temperature is not the only variable that influences thermally-induced movements. The movements are probably controlled more by the overall air/rock mass temperature rather than maximum and minimum peaks. However, for better understanding of this phenomena, we suggest monitoring for a longer period including measurement of temperatures inside the rock mass.
... e instability and failure of the rock slope is a progressive process [5], and the precursory indicators that existed before the rupture enable the assessment of the stability and to forecast the failure [6]. Many researchers have reported by using extensometer, photogrammetry, global positioning system (GPS), light detection and ranging (LiDAR), ground-based interferometry synthetic aperture radar (GBInSAR), and other technical approaches to observe displacement (or strain) to locate hazardous rocks [7][8][9][10][11][12][13]; however, in general, hazardous rock collapses at low strain and tertiary creep develop very rapidly [14], which makes it difficult to use displacement (or strain) to monitor the strength deterioration in a rock mass and to predict its tendency towards stability development [15]. ...
This paper explores a new approach for assessing the stability of a hazardous rock block on a slope using vibration feature parameters. A physical model experiment is designed in which a thermally sensitive material is incorporated into the potential failure plane of the hazardous rock, and the complete process of hazardous rock collapse caused by strength deterioration is simulated by means of constant-temperature heat transfer. Moreover, the vibration response of the hazardous rock is monitored in real time by laser vibrometry. The experimental results show that five vibration feature parameters, including the mean frequency, the center frequency, the peak frequency, the mean frequency standard deviation, and the root mean square frequency, are well-correlated with rock stability. Furthermore, through principal component analysis, the five vibration feature parameters are synthesized into a principal component factor (PCF) as a representative assessment parameter. The results of the analysis demonstrate that the variation in the PCF exhibits three characteristic stages, i.e., “stationary-deviation-acceleration,” and can effectively identify the stability evolution trend and collapse precursor behavior of hazardous rock block.
... Rock slope failure leading to rockfall is a dynamic erosional process that controls the evolution of many landscapes and, in particular, steep bedrock formations (Varnes 1978;Hutchinson 1988;Evans and Hungr 1993;Hungr et al. 1999;Rosser et al. 2005;Rabatel et al. 2008;Stock and Uhrhammer 2010;Krautblatter et al. 2012;Janeras et al. 2017). The identification of potential rockfall sources and the detection of deformations prior to failure are crucial for improving rockfall hazard assessment (Terzaghi 1962;Saito 1969;Fukuzono 1985;Zvelebill and Moser 2001;Crosta and Agliardi 2003;Corominas et al. 2005). ...
A growing body of research indicates that rock slope failures, particularly from exfoliating cliffs, are promoted by rock deformations induced by daily temperature cycles. Although previous research has described how these deformations occur, full three-dimensional monitoring of both the deformations and the associated temperature changes has not yet been performed. Here we use integrated terrestrial laser scanning (TLS) and infrared thermography (IRT) techniques to monitor daily deformations of two granitic exfoliating cliffs in Yosemite National Park (CA, USA). At one cliff, we employed TLS and IRT in conjunction with in situ instrumentation to confirm previously documented behavior of an exfoliated rock sheet, which experiences daily closing and opening of the exfoliation fracture during rock cooling and heating, respectively , with a few hours delay from the minimum and maximum temperatures. The most deformed portion of the sheet coincides with the area where both the fracture aperture and the temperature variations are greatest. With the general deformation and temperature relations established, we then employed IRT at a second cliff, where we remotely detected and identified 11 exfolia-tion sheets that displayed those general thermal relations. TLS measurements then subsequently confirmed the deformation patterns of these sheets showing that sheets with larger apertures are more likely to display larger thermal-related deformations. Our high-frequency monitoring shows how coupled TLS and IRT allows for remote detection of thermally induced deformations and, importantly, how IRT could potentially be used on its own to identify partially detached exfoliation sheets capable of large-scale deformation. These results offer a new and efficient approach for investigating potential rockfall sources on exfoliating cliffs.
... These could help understand the failure mechanism, propose a reliable warning threshold, and improve the accuracy of landslide early warning and prediction (Kamai, 1998;Sassa et al., 2009;Xu, 2012;Dong et al., 2015;Chae et al., 2017). The multitechnique approach has been used to monitor the stability of slopes and make great perfection and automation in recent years (Janeras et al., 2017;Broeckx et al., 2020), including manual markers , low-altitude photogrammetry (James et al., 2017), persistent scatterer Q. Xu, et al. Engineering Geology 278 (2020) 105817 interferometric synthetic aperture radar (PS-InSAR) (Wasowski and Bovenga, 2014;Liu et al., 2018), and Global Navigation Satellite System (GNSS) (Malet et al., 2002), etc. ...
... Rock block is formed by the intersecting discontinuities, which has great effect on the deformation and failure of the rock slope (Priest 2012;Fanti et al. 2013;Curtaz et al. 2014;Zhou et al. 2016a). Rock slope deformation is resulted from the relative sliding or rotation of unstable rock blocks (Crosta et al. 2014;Janeras et al. 2017;Zhou et al. 2017). A detailed geological survey and rock block movement monitoring are useful to mastery the stability state of the rock slope, to better understand its sensitivity to environmental triggers, and to early warning (Rose and Hungr 2007;Havaej et al. 2016). ...
Local topography and structural features of discontinuities have a great effect on the movement characteristics and failure mechanisms of the unstable rock blocks of the rock slope. By taking full advantage of the geometric information contained in the multi-temporal terrestrial laser scanning (TLS) point clouds, a technique based on a roto-translation method has been developed to track and monitor the movement behavior of blocks in unstable rock slopes. The technique can be completed in three stages: (a) a preliminary change detection is used to distinguish the unstable area by means of a shortest distance (SD) algorithm; (b) an automatic discontinuity identification algorithm is implemented to visually identify the discontinuity sets and to exactly delineate rock blocks in unstable areas; and (c) finally a roto-translation movement monitoring method is applied to track and monitor the unstable rock blocks. This technique permits the user to visually identify the discontinuity sets and to determine their orientation, and therefore provides detailed information of geometric compounding relationships between the slope and joint systems as well as the forming rock blocks which are the key impacts to stability of the rock slope. It permits the user to exactly and visually delineate the rock blocks in the unstable area, and thus the completely tracking and monitoring of lock block movement in unstable rock slopes can be effectively conducted. It overcomes the limited precision of the single TLS points and provides an actual 3D movement measuring method for the blocks rather than a shortest distance. The technique was first used in the movement behavior monitoring of the unstable rock blocks in a post-earthquake high rock slope. The results show that the rock block movement monitoring technique is well suited for providing high-quality data in the assessment of rock failure hazards.
... rockfall) between sequential TLS scans. The location, volume and dimensions of rockfall on the slope can be calculated and populated into a database, as demonstrated by Rosser et al. (2007), Guerin et al. (2014), Tonini andAbellán (2014), van Veen et al. (2017), Janeras et al. (2017) and Williams et al. (2018). In several of these studies, smaller magnitude rockfalls have been identified, which are generally not observed during field inspections performed from the base of the slope. ...
Rockfall is a complex natural process that can present risks to
the effective operation of infrastructure in mountainous terrain. Remote
sensing tools and techniques are rapidly becoming the state of the practice in
the characterization, monitoring and management of these geohazards. The aim
of this study is to address the methods and implications of how the
dimensions of three-dimensional rockfall objects, derived from sequential
terrestrial laser scans (TLSs), are measured. Previous approaches are
reviewed, and two new methods are introduced in an attempt to standardize
the process. The approaches are applied to a set of synthetic rockfall
objects generated in the open-source software package Blender. Fifty
rockfall events derived from sequential TLS monitoring in the White Canyon,
British Columbia, Canada, are used to demonstrate the application of the
proposed algorithms. This study illustrates that the method used to
calculate the rockfall dimensions has a significant impact on how the shape
of a rockfall object is classified. This has implications for rockfall
modelling as the block shape is known to influence rockfall runout.
... Allen and Huggel (2013) highlighted a potential link between rockfall events and preceding warm periods in high-mountain areas. Janeras et al. (2017) seized thermally induced movements linked to cyclic daily and yearly temperature fluctuations by using crackmeters in the Montserrat cliffs, highlighting the existence of recoverable displacements associated with the thermo-elastic behaviour of the massif, and of irreversible displacements that could be considered precursors of rockfalls. A clear distinction between reversible and irreversible displacements across fractures was also observed by Weber et al. (2017) in the Matterhorn massif. ...
Temperature changes affect crackmeters monitoring on a daily and a seasonal basis. This is due to rock mass thermal dilatancy and to instrumental matters. The consequent widening closing cycles can mask small irreversible displacements that might be precursors of rock failures. Recently, Weber et al. (Cryosphere 11:567–583, 2017) have proposed a linear fit method between temperature and fracture opening in order to compute the irreversibility index as a metrics to rank irreversible displacements. However, such an approach requires temperature sensors coupled to crackmeters. In order to overcome these limits, we propose an alternative method for deriving a normalised Z-score irreversibility index. It is based on sinusoidal wave fit of cracks opening time series only; thus, it does not require temperature monitoring. The methodology has been tested using data recorded by a wireless sensor network installed at La Pietra di Bismantova rock slab composed of 14 crackmeters and thermometers monitoring potentially unstable rock masses. A comparison of results obtained using the method of Weber et al. (Cryosphere 11:567–583, 2017) and the sinusoidal approach shows that the latter is much less sensitive to the duration of the moving window used to derive the irreversibility index, making it a much more flexible tool for indexing irreversible displacements over short time periods. Moreover, as rapid high–magnitude temperature changes can also be the causal factor of irreversible displacements, their statistical relation with peaks of the Z-score irreversibility index has been investigated. Results have shown that, depending on which crack is examined, correlations between irreversibility peaks and antecedent extreme temperature variations are more or less relevant. In conclusion, we believe that the Z-score sinusoidal wave fit irreversibility index (ZSFI) can represent a useful metrics for indexing irreversible displacements in unstable blocks using crackmeters’ datasets affected by temperature cycles at the daily and seasonal scale.
... After the data acquisition, the points were reclassified using the software CANUPO (Brodu and Lague, 2012), in order to remove the vegetation. Then, the point clouds were merged and registered (Janeras et al. 2017). After the point cloud registration, the multi-temporal comparison can be done (figure 9), taking one of them as a reference. ...
Rockfalls are slope instabilities very frequent and harmful in mountainous areas. They cause damage in infrastructures (roads and railways), buildings, vehicles and people. Several tests were carried out to understand better these events. The field activities comprised real scale tests and the characterization of natural events in the N-E of Spain, mainly in the Pyrenees range. Moreover, in order to understand the behaviour of the blocks during the fall real scale tests were carried out. We dropped a total of 124 rock blocs under controlled conditions. Prior to the block release and during their propagation downslope, several geomatic techniques were used to monitor the volumes, shapes and trajectories of the original blocks and their fragments (due to breakage); it is worth to highlight the videogrammetry to determine the trajectories of the blocks. In order to survey the natural rock walls, source of the rockfalls, the so-called massive data capture by photogrammetry (both terrestrial and UAV-drone with image and video) and Terrestrial Laser Scanning (TLS) have been used, in this way the different techniques can be compared. Finally, for the monitoring of some rock cliffs, with recurrent rockfalls, the TLS was used, trying to catch some precursory displacements that may help in the risk management of the areas at the bottom. In our contribution, the aforementioned geomatic techniques (videogrammetry, photogrammetry-terrestrial or aerial-, and TLS) are combined and compared, highlighting the pros and cons of the different methods and their applications according to environmental conditions.
... Moreover, the whole data collection and post-processing are simple and convenient, making GBSAR an effective supplement to spaceborne SAR and conventional geodetic monitoring instruments. At present, GBSAR is primarily used to monitor landslides [2,[4][5][6], slopes [7], Volcanic activity [8], and glaciers [9], as well as the deformation of large buildings such as dams [9][10][11][12] and towers and bridges [7,13,14]. Antonello et al. employed the InGrID-Lisa GBSAR system to monitor the Stromboli Volcano and through the radar measurement it has been possible to assess the deformation field over a large portion of the target area and to differentiate different processes [15]. ...
In this paper, aiming at the limitation of persistence scatterers (PS) points selection, a new method for selecting PS points has been introduced based on the average coherence coefficient, amplitude dispersion index, estimated signal-to-noise ratio and displacement standard deviation of multiple threshold optimization. The stability and quality of this method are better than that of a single model. In addition, an atmospheric correction model has also been proposed to estimate the atmospheric effects on Ground-based synthetic aperture radar (GBSAR) observations. After comparing the monitoring results before and after correction, we clearly found that the results are in good agreement with the actual observations after applying the proposed atmospheric correction approach.
... The challenges posed by this singular place of natural and cultural heritage, where hazard and exposure meet, require research work beyond the strict protection projects. Several terrain models obtained from different technologies (Table 1) have been tested for the ongoing rockfall hazard analysis (Janeras et al., 2017a). (Soler et al., 2016) are mounted and operated. ...
KeyWordsCloud: rockfall; monitoring; Lidar; SfM; photogrammetry; 3D model; risk management; mountain terrain; airborne; terrestrial; oblique; TLS; RPAS drone; geomatics
Recently, many IoT sensors are available at low cost. It is possible to acquire various data by combining appropriate sensors according to the items we want to measure and using control devices equipped data recording device such as Arduino and Raspberry Pi. On the other hand, there are high-precision measuring instruments for indoor experiments in the laboratory. By combining these with IoT technology, it is possible to improve the accuracy of field observation. Here, we introduce examples of field observation at a historical site that have continued since 2018 by performing such a combination. The historical site located in Saitama Prefecture are cave tombs dug in soft tuffaceous rock. On the surface of the slope facing southwest, many open fractures are formed by the intrusion of tree roots, then creates a rock block separated by fractures. There is a risk of rockfall. Therefore, the movement of the rock block is decided to monitor by real-time monitoring of the change in the fracture aperture. The purpose of the observation is to confirm whether the dangerous situation is getting worse. In this report, we introduce the know-how on the measurement technique leading to data acquisition and the knowledge obtained from the acquired data by real-time monitoring.
An automated, fixed-location, continuous time-lapse camera system was developed to analyze the existence of rockfall precursory movements and quantify volume changes after detachments. It was implemented to monitor the basaltic formation on which Castellfollit de la Roca village is built. Due to the geometrical conditions of the area, the camera system consists of three digital cameras managed by a control unit that contains a Raspberry Pi 4 microprocessor. Images taken every day are sent to a server for processing. A workflow has been developed to work with a set of images with an irregular time interval to detect precursor movement. The first step consists of matching the images with a reference master image and filtering the vegetation to improve the process using a mask obtained by a green leaf index (GLI) index. Then, the adjusted images are used for a forward-backward correlation process carried out to detect movements. If movement is detected, a 3D model is built using structure from motion (SfM) to quantify the movements. The system has been working since September 2021. During this period, movements from 0.01 to 0.5 m and several rockfalls of a small volume have been detected.
Rockfall is a common hazard along US Interstate Highway 70 in Glenwood Canyon, Colorado. While natural rock slopes source a substantial number of rockfalls, there remains a need to better understand typical rockfall frequencies from these slopes and to relate these frequencies to available rockfall records. In addition, the 2020 Grizzly Creek Fire in the area presents an opportunity to characterize the post-wildfire response of granitic rock slopes. To address these needs, we monitored 4 natural rock slopes of different lithologies and burn severities from 6 to 18 months after the start of the fire using an Unpiloted Aerial Vehicle and Structure from Motion photogrammetry. A total of five rockfalls (0.08–0.68m3) were detected during the monitoring interval at two slopes, while the other two showed no rockfalls. While overall rockfall activity is relatively low, the observed activity is in good agreement with results of previous study in the area, rockfall records for the highway, and analysis of a historical photo of one slope. No increase in rockfall due to the fire was observed during the monitored period, implying that the fire did not significantly affect the studied slopes or that any increase in activity had already returned to background levels by the start of monitoring. Four of the five rockfalls detected were spatially correlated with seeps in the slope, and three were temporally correlated with late winter snowfall and spring thawing, highlighting the importance of water as a consideration in selecting rock slopes for hazard monitoring and mitigation.
La revolución experimentada por el uso creciente de la geoinformación 3D en la ingeniería geológica, gracias a los avances tecnológicos, que progresivamente han facilitado una disponibilidad de técnicas de adquisición de datos y de herramientas para su análisis. Junto a los avances experimentados en la disponibilidad de recursos de computación y almacenamiento en la nube, han impulsado la expansión de numerosas aplicaciones que permiten la difusión de la geoinformación 3D en la web. A pesar de estos avances científico-técnicos, es común ver los datos 3D simplificados en imágenes estáticas 2D, perdiendo parte su potencialidad comunicativa. El objetivo de esta comunicación es presentar el diseño y las funcionalidades de unos visores web 3D de código abierto como una herramienta de sencilla utilización con la que interactuar y visualizar los resultados. Así mismo, estamos ensayando las posibilidades de la realidad mixta como una experiencia plenamente inmersiva para lograr una mejor comunicación de la geoinformación 3D.
Power laws fit to rockfall frequency-magnitude distributions are commonly used to summarize rockfall inventories, but uncertainty remains regarding which variables control the shape of the distribution, whether by exerting influence on rockfall activity itself or on our ability to measure rockfall activity. In addition, the current literature lacks concise summaries of background on the frequency-magnitude distribution for rockfalls and power law fitting. To help address these knowledge gaps, we present a new review of rockfall frequency literature designed to collect the basic concepts, methods, and applications of the rockfall frequency-magnitude curve in one place, followed by a meta-analysis of 46 rockfall inventories. We re-fit power laws to each inventory based on the maximum likelihood estimate of the scaling exponent and the cutoff volume and used Analysis of Variance and regression to test for relationships between 11 independent physical and systematic variables and the scaling exponent, applying both single-predictor and 2-predictor models. Notable relationships with the scaling exponent were observed for rockmass condition, geology, and maximum inventory volume. Higher scaling exponent values were associated with higher quality rockmasses, sedimentary rocks, and with smaller maximum rockfall volumes. Climate, data collection frequency, and data collection method also appear to have some influence on the scaling exponent, since higher scaling exponents were associated with temperate climates and inventories with shorter temporal extent and methods that involved few or no revisits to the slope. Relationships between the scaling exponent and slope angle, slope aspect, number of rockfalls in the inventory, record length, and minimum inventory volume are more ambiguous due to the noise inherent in comparing many studies together. In line with previous work, this study reinforces that sampling large volumes is important to obtaining an accurate distribution, and that the spatial scale of the inventory affects the likelihood of obtaining these measurements. We conclude with discussion of the results and recommendations for future work.
This contribution summarizes challenges in the implementation of a standardised procedure for rock fall hazard zoning in Austria. The discussion focuses on the impact of mapping strategy applied to rock size distributions and the frequency of rock fall, the applicability of different 3D rock fall simulation models for hazard zoning in different topographic and geologic envi�ronments, and the cartographic presentation of results.
This paper describes a newly designed, experimental, and affordable rock slope monitoring system. This system is being used to monitor three rock slopes in Czechia for a period of up to 2 years. The instrumented rock slopes have different lithology (sandstone, limestone, and granite), aspect, and structural and mechanical properties. Induction crackmeters monitor the dynamic of joints, which separate unstable rock blocks from the rock face. This setup works with a repeatability of measurements of 0.05 mm. External destabilising factors (air temperature, precipitation, incoming and outgoing radiation, etc.) are measured by a weather station placed directly within the rock slope. Thermal behaviour in the rock slope surface zone is monitored using a compound temperature probe, placed inside a 3 m deep subhorizontal borehole, which is insulated from external air temperature. Additionally, one thermocouple is placed directly on the rock slope surface. From the time series measured to date (the longest since autumn 2018), we are able to distinguish differences between the annual and diurnal temperature cycles of the monitored sites. From the first data, a greater annual joint dynamic is measured in the case of larger blocks; however, smaller blocks are more responsive to short-term diurnal temperature cycles. Differences in the thermal regime between the sites are also recognisable and are caused mainly by different slope aspect, rock mass thermal conductivity, and colour. These differences will be explained by the statistical analysis of longer time series in the future.
In this article, we are elaborating an example of predictive rockfall assessment by using Terrestrial Laser Scanning (TLS) in monitoring a road cut, hosted in flysch rock formation, near Ljig in Serbia. A sequence of rockfall events from 2013-2019 is presented, while the cut has been more broadly investigated in our earlier work. Beside occasional rockfalls which are routinely detected by annual TLS monitoring, it was possible to track the pre-failure deformations preceding a series of rockfalls, reaching 0.3 m ³ in volume with 0.5 annual reoccurrence probability. Monitoring enabled identification of subtle displacements of about 1 cm after the first event in 2014 and keeping track of its progression. After a series of events in the following years, we were able to define the pre-failure threshold which can be applied to the adjacent rock blocks, assuming a similar block volume. It also enabled us to anticipate and simulate the event before it happens. This approach allows planning, prevention and protection, and there is a great deal of interest to standardize it for high-risk slopes and cuts in rock masses.
Nowadays, the 3D modelling of surfaces is widely used to provide point clouds in geosciences. To study the evolution of landslides, many point clouds are available but post-processing can be very computationally demanding, especially to analyze their dynamics. This paper proposes automatic tools to identify areas with continuous motion and those with non-continuous motion using a new continuous motion indicator. Displacements of continuously moving areas are computed by two “displacements” methods (the image correlation method and the Gefolki differential optical flow method), which are compared. The evolution of non-continuous motion areas is quantified by a distance metric. The developed method is applied on two sites with different deformation mechanisms and evolution speeds to test the ability to show the 3D spatial evolution of landslides. The comparison with instrumental data shows a good concordance between the calculated data and the reference data. The Gefolki differential optical flow method is considered as a relevant option for the image correlation method with the new continuous motion indicator.
Nowadays, the 3D modelling of surfaces is widely used to provide point clouds in geosciences. To study the 15 evolution of landslides, many point clouds are available but post-processing can be very computationally demanding, 16 especially to analyze their dynamics. This paper proposes automatic tools to identify areas with continuous motion and 17 those with non-continuous motion using a new continuous motion indicator. Displacements of continuously moving areas 18 are computed by two displacements methods (the image correlation method and the Gefolki differential optical flow 19 method), which are compared. The evolution of non-continuous motion areas is quantified by a distance metric. The 20 developed method is applied on two sites with different deformation mechanisms and evolution speeds to test the ability to 21 show the 3D spatial evolution of landslides. The comparison with instrumental data shows a good concordance between 22 the calculated data and the reference data. The Gefolki differential optical flow method is considered as a relevant option 23 for the image correlation method with the new continuous motion indicator. 24
Amongst mass wasting events, rockfalls remain the most unpredictable and the most frequent hazard in the alpine region. In a context of growing urbanization in mountainous regions, rockfalls represent an increasing risk for local communities and infrastructures. This thesis aims to develop an association of relevant methods for rockfall monitoring. One objective of this thesis is to associate topography measurement and seismological monitoring in order to improve significantly in understanding rockfalls dynamics. This work was mainly carried out in the Chartreuse massif (Isère, French Alps), and in particular two cliffs, Mount Saint-Eynard and Mount Granier. Using photogrammetry, we acquired diachronic Digital Elevation Models (DEMs) of the cliffs. Such monitoring enables us to carry out rockfall inventories and occurrence frequency analysis. It also provides us information on rockfall locations and their structural configurations. Combining DEMs and rockfall seismic monitoring allowed us to study relations between rockfall properties (location, volume, geometry, propagation, etc.) and the induced seismic signal. Characteristics of the seismic signal (duration and energy, frequency content, envelope shape) vary depending on the event propagation mode (mass-flow, free-fall, sliding, bouncing …). Selecting events with the same propagation type provides a more accurate characterization of rockfalls properties than when mixing different types of events. For free-falling rockfalls, we analyze the seismic signal of the detachment phases and first impacts. We found relations between seismic signals parameters and rockfalls potential energy, free-fall heights, and volumes. For mass-flow type events, we found a scaling law between rockfalls seismic energy and their volumes. By coupling DEMs and seismic records, we can reconstruct rockfall sequence with accurate timing and correct volume estimations. Controlled block releases were realized in laboratory and on-site to widen our observations on rockfall events.
Machine learning methods for data processing are gaining momentum in many geoscience industries. This includes the mining industry, where machine learning is primarily being applied to autonomously driven vehicles such as haul trucks, and ore body and resource delineation. However, the development of machine learning applications in rock engineering literature is relatively recent, despite being widely used and generally accepted for decades in other risk assessment-type design areas, such as flood forecasting. Operating mines and underground infrastructure projects collect more instrumentation data than ever before, however, only a small fraction of the useful information is typically extracted for rock engineering design, and there is often insufficient time to investigate complex rock mass phenomena in detail. This paper presents a summary of current practice in rock engineering design, as well as a review of literature and methods at the intersection of machine learning and rock engineering. It identifies gaps, such as standards for architecture, input selection and performance metrics, and areas for future work. These gaps present an opportunity to define a framework for integrating machine learning into conventional rock engineering design methodologies to make them more rigorous and reliable in predicting probable underlying physical mechanics and phenomenon.
The decrease in strength of potential slip surface after an earthquake and heavy rainfall, is one of the main causes of rock failures. However, fundamental natural frequency can demonstrate the changes in physical and mechanical parameters and support a real-time quantitative assessment of the safety of rocks. This study applied Laser Doppler Vibrometry in an experiment called Frozen-Thawing Test (FTT) in which the entire collapse process caused by strength degradation is simulated. The results show that the safety factor calculated by fundamental natural frequency can give us a new method for stability assessment of unstable rocks. Therefore, the method can satisfy real-time safety evaluation of unstable rocks and will offer a foundation for better responses to rock collapse.
As a typical abrupt geological hazard, rockfalls are widely distributed and occur frequently. It is often difficult to predict the occurrence, and therefore record and monitor the whole failure process of rockfalls. In this study, with the combined use of terrestrial laser scanning (TLS) and ground-based radar interferometry (GB-InSAR) technologies, a typical small collapse in the Hongshiyan post-earthquake rock slope was monitored. An accurate TLS three-dimensional (3D) rock slope model of the study area was established with high-resolution geometry and morphology information, the discontinuity sets and their orientations and distributions were visually identified and analyzed by means of an automatic discontinuity identification algorithm. A perspective view of the whole dynamic failure process of the small collapse was achieved; the displacement behavior during critical sliding stage was revealed by integrating the high-accuracy (millimetric) GB-InSAR monitoring results into the TLS 3D model. It can be used for a complete analysis of the failure behavior and stability assessment of the rock slope during a phase of emergency. The unstable rock block on the slope exhibited a rapid growth of displacement. The dynamic failure process of the rock block underwent three obvious accelerating periods. There was a correspondence between the spatial expansion of the moving area and the process of cracking propagation of rock bridges. The stability of the perilous rock above the tafoni was controlled by the connectivity of rock bridges. Thanks to monitoring, early warning and preventive measure were taken, which avoided a possible undesirable event. This typical case study can provide a reference for the monitoring of an unstable rock slope and the understanding of the evolution of rock block kinematics before collapse.
A rockfall risk mitigation plan is currently under development in the Montserrat Massif (Catalonia, NE Spain). The Degotalls cliff is a place where the risk for the main access infrastructures to a highly visited area has been revealed recently. Several tests on monitoring techniques have been carried out to improve the knowledge on precursory displacements as indication of rock block instability.
Rockfalls are a recurrent phenomenon in the mountain of Montserrat (central Catalonia). The rock wall of the Monastery of Montserrat, wich dominates a religious and touristic complex, suffered a rockfall in December, 2010 wich damaged one of the buildings of the Abat Cisneros Hotel. This proves the extent of geological risk this complex is exposed to. The present study proposes a method of analysis in order to determine the rock fall susceptibility of the main blocks and boulders that make up the relief of the rock wall. This analysis has been carried out by means of a detailed inspection, and with the caracterization of several potencial instability indicators observed in each of the studied blocks and boulders. A detailed mapping of previous rockfalls has also been completed, based on geomorphological and colour indicators of the rockfall area, as well as a mapping of historic rockfalls based on documented events and witnesses of these phenomena.
In this study we present the results of the monitoring carried out in several conglomerate cliffs of Montserrat Mountain (Catalonia, Spain) using a Terrestrial LiDAR instrument. Rockfalls are a remarkable risk for visitors, transportation and buildings of Montserrat Monastery. The monitoring carried out is based on the multi-temporal comparison of point clouds acquired with a long-range Terrestrial LiDAR (Ilris 3D, Optech). In order to detect in detail the rockfalls on the analyzed cliffs, a process based on cluster recognition was applied. A total of 451 rockfalls with volumes between 0.001 and 891 m3 were detected. The exact location of detached areas has allowed the determination of the most active rockfall zones in the different rock faces. Thus, in this work we have obtained more detailed rockfall inventories that those collected with classical observational methods. These inventories have allowed magnitude-frequency computations, allowing future hazard and risk estimations with greater accuracy.
The field of Wireless Sensor Networks (WSNs) is now in a stage where serious applications of societal and economical importance are in reach. For example, it is well known that the global climate change dramatically influences the visual appearance of mountain areas like the European Alps. Very destructive geological processes are triggered or intensified, affecting the stability of slopes and possibly inducing landslides. Up to now, however, the interactions between these complex processes are poorly understood. To significantly advance the knowledge of these interactions, we advocate the use of wireless sensing technology as a new scientific instrument for environmental monitoring under extreme conditions. Large spatio-temporal variations in temperature and humidity, mechanical forces, snow and ice coverage, and unattended operation play a crucial role in long-term, high-altitude deployments. Despite these challenges, we argue that in order to reach the set out goals it is inevitable that WSNs be created as a high-quality scientific instrument with known and predictable properties, rather than as a research toy delivering average observations at best. In this paper, we present key techniques for achieving highly reliable, yet resource-efficient WSNs based on our longstanding experience with productive WSNs measuring permafrost processes in the Swiss Alps.
En este artículo se presenta la metodología desarrollada para el análisis del grado de exposición a escala 1:25.000 y los resultados obtenidos de aplicar esta propuesta a una parte importante del Parque Natural de la Montaña de Montserrat para los vehículos que circulan por carretera considerando o no los ocupantes. El desarrollo de esta propuesta forma parte de un estudio en curso de mayor calado que se centra en el análisis de la exposición al riesgo por desprendimientos de roca a diferentes escalas y en diferentes contextos naturales y sociales.
La montaña de Montserrat está situada a 50 km al noroeste de Barcelona entre las comarcas de la Anoia, del Baix Llobregat y del Bages. En esta montaña se sitúa el santuario y monasterio benedictino dedicado a la Virgen de Montserrat. El acceso al Monasterio y a las distintas instalaciones del recinto se puede realizar por carretera, por tren cremallera, por teleférico o caminando. Geológicamente, el macizo de Montserrat forma parte de la cuenca del Ebro, y está situado en su extremo SE, adosado a la cordillera prelitoral de las Cadenas Costeras Catalanas. Las rocas que constituyen la montaña son conglomerados, intercalados con lutitas y areniscas.
Las laderas del Parque Natural de la Montaña de Montserrat se encuentran afectadas por caídas de rocas, cuyo volumen suele superar los 1000 m3 por desprendimiento. Este fenomeno constituye un riesgo geológico importante para las infraestructuras existentes y para todos los visitantes de la montaña. Durante los últimos cinco años se han producido desprendimientos de rocas en zonas muy frecuentadas por los visitantes.
Los desprendimientos rocosos son uno de los fenómenos geomorfológicos más comunes en escarpes montañosos (Copons y Vilaplana, 2008) [6]. Es un fenómeno muy frecuente y se considera el movimiento de ladera que alcanza mayores velocidades (Varnes, 1978) [7], llegando a registrar energías de impacto muy elevadas (Agliardi y Crosta, 2003 y 2009) [8 y 9].
El objetivo principal del trabajo pretende evaluar y cartografiar la exposición a los desprendimientos de roca de los elementos vulnerables en el Parc Natural de la Muntanya de Montserrat (PNMM).
La metodología que se propone para el cálculo del grado de exposición se basa en seis fases:
1- Identificación, clasificación e inventario de los elementos potencialmente amenazados.
2- Zonificación de la frecuencia de ocurrencia del fenómeno en la zona de estudio.
3- Diseño de la función de exposición específica para el elemento en estudio.
4- Obtención del índice de exposición que es el producto de la frecuencia de ocurrencia del fenómeno por la función de exposición del elemento vulnerable mediante análisis SIG con el programa ArcGis 10.0 de ESRI.
5- Obtención del grado de exposición agrupando en categorías los valores numéricos del índice de exposición.
6- Realización del mapa de zonificación de la exposición.
Las tipologías de elementos vulnerables considerados en la globalidad del estudio son: Vehículos en movimiento, Personas en vehículos en movimiento, Personas en caminos, Elementos permanentes y Personas en edificios. Cada tipología definida agrupa todos aquellos elementos que reúnen las mismas características y se ha diseñado una función de exposición para cada una de ellas. Para el cálculo de la exposición se ha considerado separadamente el conjunto de elementos primero sin tener en cuenta las personas que los ocupan o utilizan y en una fase posterior estos mismos elementos con personas.
La frecuencia de ocurrencia de un fenómeno peligroso puede expresarse cartográficamente mediante mapas de zonificación de frecuencia, de manera que se delimitan zonas geográficas y se clasifican en grados según la frecuencia de ocurrencia del fenómeno. La asignación de las frecuencias de ocurrencia se ha realizado en base a la metodología aplicada en la confección del MPRG25M, la información de campo recopilada por Geocat, los conocimientos de la zona y las observaciones “in situ”. En base a esta asignación se obtiene un mapa de zonificación de frecuencia de ocurrencia donde se definen 4 grados: bajo, medio, alto y muy alto. Estos grados son relativos entre sí y no están cuantificados. Para el cálculo del índice de exposición se ha asignado a cada categoría de frecuencia un valor numérico (Frecuencia Muy Baja: 1, Baja: 2, Media: 4 y Alta: 8). Adoptar la zonificación de frecuencias a partir de un trabajo previo ha condicionado la aplicación de la metodología desarrollada. También ha definido los límites de grado de exposición de los elementos evaluados ya que asumen unas condiciones de partida preestablecidas: la zonificación de peligrosidad definida en el MPRG25M.
La función de exposición, f(ev) es única para cada tipología de elemento. f(ev) tiene en cuenta las características propias del elemento que se quiere estudiar, como pueden ser la velocidad en que el elemento puede cruzar la zona afectada por un fenómeno peligroso o el número de vehículos que circulan por una vía. En este proyecto se ha propuesto una función de exposición para cada elemento vulnerable evaluado.
Considerando los valores obtenidos con la f(ev) y la frecuencia se ha obtenido el índice de exposición IE, el cual permite definir 4 categorías de grado de exposición: Bajo, Medio, Alto y Muy Alto. Cada una de ellas equivale a un orden de magnitud de índice de exposición. Estos resultados se presentan en forma de cartografías a escala 1:25.000.
La lectura de los mapas de zonificación del grado de exposición a los desprendimientos, permite visualizar la problemática en base a dos tipos de información fundamentales (una areal y otra lineal). Por un lado la coloración general de base del mapa nos informa sobre las zonas clasificadas con distintos grado de frecuencia de ocurrencia de los desprendimientos, esto se puede considerar como una aproximación a la peligrosidad. Por otro lado la coloración de los distintos segmentos o tramos de las carreteras analizadas nos indican el grado de exposición a los desprendimientos. En este caso estamos aproximándonos a la estimación del riesgo geológico.
En este artículo se presenta una parte de las aplicaciones realizadas en la totalidad del estudio. Se muestra el resultado de aplicar la metodología desarrollada para los vehículos en movimiento con o sin personas en 3 escenarios del PNMM (A-mínimos, B-habitual y C-máximos).
El análisis del grado de exposición de vehículos en carreteras se presenta cartográficamente por tramos de carreteras. Se distinguen 26 tramos potencialmente afectados por desprendimientos con una longitud total de 13.91 km en su proyección horizontal.
Para este elemento vulnerable los grados alto y muy alto representan más del 85% de la longitud en los tres escenarios, estos altos porcentajes indican que la mayor parte de trazado de las carreteras de acceso a la montaña tiene un alto nivel de exposición. Es importante destacar que el grado de exposición muy alto en los escenarios A y B se observa exclusivamente en la carretera C-55, ubicada en el fondo de valle del Llobregat, debido a la elevada circulación de la vía. Mientras que en la carretera BP-1121 de acceso al monasterio de Montserrat desde Monistrol y para el escenario C se obtienen tramos de grado de exposición muy alto. Estos se ubican donde los desprendimientos tienen frecuencia de ocurrencia del fenómeno media o alta y en condiciones de tráfico abundante. Mientras que la carretera que da acceso al monasterio desde el Bruc (BP-1103) el máximo grado de exposición que presenta es alto. La carretera BP-1103 no cruza la zona de frecuencia alta de desprendimientos y la circulación de vehículos es menor que en la BP-1121 y muchísimo menor que en la C-55.
Grado de exposición al riesgo de desprendimientos de Personas en vehículos en carreteras. Esta parte del análisis de la exposición es esencial para tener una buena instantánea del riesgo geológico debido a la elevada vulnerabilidad humana que integran los elementos analizados. En este caso se han obtenido 11 tramos de carretera con una longitud total de 9.03km en proyección horizontal de las carreteras BP-1103 y BP-1121, las cuales dan acceso al monasterio de Montserrat desde Monistrol y el Bruc respectivamente.
El grado de exposición de personas en vehículos que circulan por carreteras tiene unos resultados a tener muy en cuenta, ya que la suma del grado alto y muy alto en todos los escenarios representa como mínimo el 97.3 % de la longitud total de carretera expuesta. Estos resultados representan una buena aproximación de la estimación al riesgo de desprendimientos en las carreteras estudiadas.
La propuesta metodológica desarrollada es capaz de reflejar la realidad del territorio frente a la exposición a los desprendimientos en escenarios definidos pero es necesario ser crítico en los resultados obtenidos, y así, mejorar su aplicación y aumentar el grado de confianza.
Durante el transcurso de la aplicación de la metodología se han confirmado las diferentes hipótesis de partida realizadas, constatando que el grado de exposición varía en un territorio según los elementos expuestos y los escenarios que se plantean, y se ha ratificado que los datos de partida y la escala de trabajo condicionan y limitan los resultados.
Este es un primer trabajo general y sintético de la exposición a los desprendimentos de la montaña de Montserrat. Es importante recordar que los cálculos del grado de exposición se han realizado a partir de los datos de peligrosidad natural no protegida por obras de defensa. Así pues en las zonas donde se han realizado actuaciones para la mitigación de los desprendimientos se debería esperar que la exposición actual fuera menor que la calculada. La cuantificación de lo que podríamos llamar “exposición protegida” necesitaría de un estudio específico a la escala adecuada, donde se partiera de la peligrosidad residual existente en las zonas con obras de defensa.
Los resultados de este trabajo nos llevan a reflexionar sobre cuales serían las mejores estrategias para mitigar el riesgo de desprendimientos de roca en el PNMM. Está claro que, aparte de las necesarias obras estructurales de defensa que en algunos de los casos ya se han ejecutado, la implementación de estrategias de defensa no estructural es, a medio y largo plazo la mejor política de mitigación del riesgo. En el caso de PNMM, replantearse la gestión de la movilidad en el acceso a la montaña y, en especial al monasterio, ayudaría a alcanzar, sin lugar a dudas, una minimización del riesgo geológico.
En el décimo aniversario de la entrada en servicio del ferrocarril de Cremallera de Montserrat (Barcelona) se analizan aspectos de la peligrosidad de caída de rocas para valorar la labor de mitigación del riesgo conseguida en este tiempo. Se analiza de forma semi-cuantitativa la evolución desde la situación previa o estado natural de peligrosidad, a la consecución de un estado de protección homogéneo y coherente en la situación actual. Se detectan los focos prioritarios donde centrar la atención en los próximos años, más allá del ámbito propio de competencia del ferrocarril, en una visión global de toda la ladera que involucra también a los accesos por carretera al Monasterio de Montserrat.
Ground vibration in blasting works for shallow tunnels may induce some effects on unstable blocks on the surface of jointed rock mass. This fact can be critical in cases such as Vall de Núria rack railway, where tunneling works are the main measure for rock fall risk mitigation, especially when the service must remain fully operational and safe during the excavation phase. Newmark displacement theory can articulate a complete and useful method to take account of these effects during the design and tunneling process. Most relevant results obtained in both phases are presented and related considerations are discussed about data collection and processing, geological tracing observed or expected, ground effects and, in summary, the monitoring work capabilities for this kind of situations.
In this poster it is summarized the current state of works related to rockfall risk for Montserrat sanctuary area. Relevant protection works have been carried out during the last 10 years, but a global perspective over the problem is needed to reach a reasonable solution. For the rack railway, since 2001 rockfall problems have been taken into account. A great investment effort has been done for protective measures inside his own domain in the slope. For autumn 2011 is planned to complete a linear protection with homogeneity and continuity along railway. For the roads, after big rockfalls since 2007, intensive protection works have been done locally. The preventive extension of risk mitigation to the whole context with related studies is contained in an approved intervention plan, but it is stopped at present due economical situation. Therefore is good time to reconsider the role that shall play the access by road. Special consideration is needed for parking place, where the exposure is higher due the vehicles permanence and the presence of people walking or staying for longer time. The high cliffs above parking also imply danger to railway, because it runs in a lower level inside the high probability run-out zone. After big rockfall events, intensive protection work is completed in about 30% of parking area extension. A possibility to be evaluated for reducing global exposure is to restrain access by road only to the services, supplies and maintenance, conducting visitors to the public transport systems combining terrestrial and aerial: the rack railway and a fully renovated cable-way can perfectly achieve enough transportation capacity at rush hour, providing good backup one for the other under hazardous situations or any incident. For sanctuary buildings area at the present time a study is being carried out to get inventory and mapping of starting zones that deals into a prioritization of future interventions. In this sense, it is planned an historical data analysis to assess more carefully the frequency term in hazard quantification. In conclusion, Montserrat is an interesting case due its particular terrain conditions prone to rockfall activity together with the human facilities, both transport infrastructure and buildings, located at mid slope; but also the present situation is specially interesting in terms of defining the future strategy that might achieve a fairly and sustainable risk mitigation.
For the rack railway of Montserrat a hazard assessment has been performed to evaluate rockfall protection degree after the intensive protecting works carried out during the last 10 years. A qualitative analysis has been done to determine the hazard in 39 initiation areas defined by levels and basins, considering the rockfall propagation in the basis of reach angle method to be implemented in GIS. Despite all constraints of such type of approach, an overview on risk along the railway is obtained to assess the protection level obtained thanks to the protective investment done by the railway office, and also to prioritize the remaining hazard focus.
Montserrat Mountain is located near Barcelona in Catalonia, at the north-east corner of Spain, and its massif is formed by conglomerate interleaved by siltstone/sandstone with steep slopes very prone to rock falls. The increasing visitor's number in the monastery area, reaching 2.4 million per year, has pointed out the risk derived from rock falls for this building area and also for the terrestrial accesses, both roads and rack railway. A risk mitigation plan is currently been applied for 2014-2016 that contains monitoring testing and implementation as a key point. The preliminary results of the pilot tests carried out during 2014 are presented, also profiting from previous sparse experiences and data, and combining 4 monitoring techniques under different conditions of continuity in space and time domains, which are: displacement monitoring with Ground-based Synthetic Aperture Radar and characterization at slope scale, with an extremely non uniform atmospheric phase screen because of the stepped topography and atmosphere stratification; Terrestrial Laser Scanner surveys quantifying frequency for unnoticed activity of small rock falls, and monitoring rock block displacements over 1cm; monitoring of rock joints with a wireless net of sensors; and tentative surveying for singular rocky needles with Total Station.
Data transfer and communication systems are first priority for further development of geotechnical monitoring. This paper describes a Wireless Sensor Network (WSN) for communication and monitoring systems based on ZigBee technology in underground mines. Wireless sensor networks (WSNs) have been widely employed in industries and the military with multiple applications to monitor environment, track target and telecommunicate data. Recently, WSNs have also been used for communication and monitoring systems in underground mines. In this study, a proposed WSN system of ZigBee network as one of the WSNs is investigated in underground mines regarding communication and monitoring systems to resolve operational challenges such as safety and gathering geotechnical information. Developed ZigBee wireless network system was installed in Paddington Gold Underground Mine (managed by Norton Gold Fields Limited). In this research, the intensity of received signal strength indication (RSSI) between wireless nodes within ZigBee network was investigated. Also, the optimal arrangement of ZigBee wireless nodes on the basis of radio wave attenuation and possibility of stable wireless communications which will be used for gathering some significant geotechnical information such as seismic, deformation and pressure were investigated. The experimental results indicate that a secure and stable ZigBee wireless network can be developed to overcome mentioned operational challenges in underground mining. It is obvious that this proposed system helps further progress in rock mechanics and geotechnical fields
Urban subsidence and landslides are among the
greatest hazards for people and infrastructure safety and they
require an especial attention to reduce their associated risks. In
this framework, ground-based synthetic aperture radar (SAR)
interferometry (GB-InSAR) represents a cost-effective solution
for the precise monitoring of displacements. This work presents
the application of GB-InSAR techniques, particularly with the
RiskSAR sensor and its processing chain developed by the Remote
Sensing Laboratory (RSLab) of the Universitat Politècnica de
Catalunya (UPC), for the monitoring of two different types of
ground displacement. An example of urban subsidence monitoring
over the village of Sallent, northeastern of Spain, and an
example of landslide monitoring in El Forn de Canillo, located
in the Andorran Pyrenees, are presented. In this framework, the
key processing particularities for each case are deeply analyzed
and discussed. The linear displacement maps and time series
for both scenarios are showed and compared with in-field data.
For the study, fully polarimetric data acquired at X-band with a
zero-baseline configuration are employed in both scenarios. The
displacement results obtained demonstrate the capabilities of GBSAR
sensors for the precise monitoring of ground displacement
phenomena.
Ground-based synthetic aperture radar (SAR)
(GB-SAR) sensors represent an effective solution for the monitoring
of ground displacement episodes. Initially, the most GB-SAR
sensors were based on vector network analyzers (VNA). This type
of solution, characterized by a slow scanning time comparable
to the decorrelation of the troposphere medium, compromised
in many cases the quality of final products for the application
of persistent scatterer interferomerty (PSI) techniques. The
development of GB-SAR sensors based on the use of stepped
linear frequency modulated continuous wave (SLFMCW) signals
has led to significant improvements during the last years. They
have allowed fulfilling the need of temporal homogeneity of the
troposphere during the acquisition time and, moreover, they have
favored the acquisition of reliable polarimetric SAR (PolSAR)
measurements without drastically increasing the scanning time.
This fact has boosted the inclusion of polarimetric SAR interferometry
(PolInSAR) algorithms in PSI processing chains, which
are demonstrating to outperform classical single-polarimetric
performances. The objective of this paper is twofold. On the one
hand, a general overview of the polarimetric RiskSAR sensor,
developed by the Universitat Politècnica de Catalunya (UPC), is
put forward as an example of SLFMCW GB-SAR system implementation.
On the other hand, a complete theoretical description
of ground-based SAR (GB-SAR) interferometry (GB-InSAR)
techniques for PSI purposes is widely discussed. The adaptation of
the Coherent Pixels Technique to obtain the linear and nonlinear
components of ground displacement phenomena is proposed. In
the second part of this paper, the displacement maps and time
series over two very different scenarios are presented in order to
show the feasibility of GB-SAR sensors for terrain displacement
monitoring applications.
The landslide of El Forn de Canillo in the Principality of Andorra is one of the largest in the
Pyrenees. In 2007 a monitoring system (boreholes equipped with inclinometers, extensometers
and piezometers) was set up. Between 2010 and 2011, surface displacements were measured
using differential interferometry techniques (GB-SAR and DInSAR). The interferograms of
both radars have yielded mutually consistent results, compatible with the inclinometric
measures. Furthermore, the observations with TerraSAR-X, with greater spatial coverage,
have shown that the displacements are significantly higher in the upper part of the slope (up to
4 cm/year). Field surveys evidenced the presence of activity indicators (open tension cracks,
ground disturbance and structural damages) that confirm the existence of these movements. In
El Forn landslide, the combined use of radar techniques with conventional instrumentation
allows for a more complete and representative interpretation of the behavior of the slope.
Abstract—In this paper, a new model-based technique for the
compensation of severe height-dependent atmospheric artifacts,
using ground-based synthetic aperture radar (SAR) data over
mountainous regions, is proposed. The method presented represents
an extension of already existing techniques, but now taking
into account the effect of steep topography in the atmospheric
phase screen compensation process. In addition, the technique is
adapted to work with polarimetric SAR data, showing, in that
case, a noticeable improvement in the compensation process. The
method is validated in the mountainous environment of El Forn de
Canillo, located in the Andorran Pyrenees, where there is a slowmoving
landslide that nowadays is being reactivated coinciding
with strong rain episodes. In this framework, ten zero-baseline
fully polarimetric data sets have been acquired at X-band during
a one-year measurement campaign (October 2010–October 2011)
with the GB-SAR sensor developed at the Universitat Politècnica
de Catalunya. First, the impact of the severe atmospheric fluctuations
among multitemporal GB-SAR measurements is carefully
studied and analyzed. Hence, the need to correctly estimate and
compensate the resulting phase differences when retrieving interferometric
information is put forward in the frame of differential-
SAR-interferometry applications.
We present a long-term spatio-temporal analysis of rock slope evolution using a Terrestrial LiDAR aiming to improve our understanding of the link between pre-failure deformation and the spatial prediction of rockfalls. We monitored the pilot study area located at the Puigcercós cliff (Catalonia, Spain) over a period of 1,705 days and detected the deformation of nine different cliff regions together with a high rockfall activity. An exact match was observed between the progressively deformed areas and the regions recently affected by three of the highest magnitude rockfall events, demonstrating a causal relationship between pre-failure deformation and rockfall occurrence. These findings allowed us to make a forward spatial prediction of future failures, hypothesizing a high probability of failure in the six remaining regions. We observed an exponential acceleration of the deformation close to failure, in accordance with tertiary creep theory. However, the temporal analysis of the deformed areas showed a complex and variable behavior, so no exact prediction of the date of failure can yet be made. Our findings have broadened our understanding of the pre-failure behavior of rockfalls and have clear implications for the future implementation of early warning systems.
Rockslides in alpine areas can reach large volumes and, owing to their position along slopes, can either undergo large and rapid evolution originating large rock avalanches or can decelerate and stabilize. As a consequence, in particular when located within large deep-seated deformations, this type of instability requires accurate observation and monitoring. In this paper, the case study of the La Saxe rockslide (ca. 8 × 106 m3), located within a deep-seated deformation, undergoing a major phase of acceleration in the last decade and exposing the valley bottom to a high risk, is discussed. To reach a more complete understanding of the process, in the last 3 years, an intense investigation program has been developed. Boreholes have been drilled, logged, and instrumented (open-pipe piezometers, borehole wire extensometers, inclinometric casings) to assess the landslide volume, the rate of displacement at depth, and the water pressure. Displacement monitoring has been undertaken with optical targets, a GPS network, a ground-based interferometer, and four differential multi-parametric borehole probes. A clear seasonal acceleration is observed related to snow melting periods. Deep displacements are clearly localized at specific depths. The analysis of the piezometric and snowmelt data and the calibration of a 1D block model allows the forecast of the expected displacements. To this purpose, a 1D pseudo-dynamic visco-plastic approach, based on Perzyna’s theory, has been developed. The viscous nucleus has been assumed to be bi-linear: in one case, irreversible deformations develop uniquely for positive yield function values; in a more general case, visco-plastic deformations develop even for negative values. The model has been calibrated and subsequently validated on a long temporal series of monitoring data, and it seems reliable for simulating the in situ data. A 3D simplified approach is suggested by subdividing the landslide mass into distinct interacting blocks.
In the present study we analysed a series of terrestrial LiDAR point clouds acquired over a cliff in Puigcercos (Catalonia, Spain). The objective was to detect and extract individual rockfall events occurred during a time span of six months and to investigate their spatial pattern distribution. To this end local and global cluster algorithms were applied. First we used the Nearest Neighbour Clutter Removal (NNCR) method in combination with the Expectation–Maximization (EM) algorithm to separate feature points from clutter; then a density based algorithm (DBSCAN) allowed us to isolate the single cluster features which represented the rockfall events. Finally we estimated the Ripley’s K-function to analyse the global spatial pattern of the identified rockfalls. The computations for the cluster analyses were carried out using R free software for statistical computing and graphics. The local cluster analysis allowed a proper identification and characterization of more than 600 rockfalls. The global spatial pattern analysis showed that these rockfalls were clustered and provided the range of distances at which these events tend to be aggregated.
http://www.josis.org/index.php/josis/article/view/123/108
In this paper all the phases for the realization of the early warning system for the rockslide of Torgiovannetto in Central Italy are described. The landslide consists in a 182,000 m3 rock wedge threatening two roads which are important for local transportation. The present work encompasses all the components of an early warning system, including the geological knowledge, the risk scenarios, the kinematic characterization of the landslide, the choice and installation of the monitoring system, the setting of appropriate alarm levels
and the definition of plans of civil protection. The focus is on practical and logistical issues met in all these phases and the counter-measures adopted.
At present the system consists in 13 wire extensometers, 1 thermometer, 1 rain gauge and 3 cameras. Should a velocity threshold be exceeded by two or more sensors, the attention level would be entered, causing improved monitoring and surveillance. In case the behavior of the landslide changes and, by using expert judgment and forecasting methods, an imminent failure is hinted, then an alarm is issued and the upper road is closed.
This paper can provide ideas and solutions for a landslide earlywarning systemthat aims to be simple, flexible, versatile and with a low probability of giving false alarms.
Geophysical applications of radar inter-ferometry to measure changes in the Earth's surface have exploded in the early 1990s. This new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture radar at two distinct times. The resulting interferogram is a contour map of the change in distance between the ground and the radar instrument. These maps provide an unsurpassed spatial sampling density (100 pixels km 2), a competitive pre-cision (1 cm), and a useful observation cadence (1 pass month 1). They record movements in the crust, pertur-bations in the atmosphere, dielectric modifications in the soil, and relief in the topography. They are also sensitive to technical effects, such as relative variations in the radar's trajectory or variations in its frequency standard. We describe how all these phenomena contribute to an interferogram. Then a practical summary explains the techniques for calculating and manipulating interfero-grams from various radar instruments, including the four satellites currently in orbit: ERS-1, ERS-2, JERS-1, and RADARSAT. The next chapter suggests some guide-lines for interpreting an interferogram as a geophysical measurement: respecting the limits of the technique, assessing its uncertainty, recognizing artifacts, and dis-criminating different types of signal. We then review the geophysical applications published to date, most of which study deformation related to earthquakes, volca-noes, and glaciers using ERS-1 data. We also show examples of monitoring natural hazards and environ-mental alterations related to landslides, subsidence, and agriculture. In addition, we consider subtler geophysical signals such as postseismic relaxation, tidal loading of coastal areas, and interseismic strain accumulation. We conclude with our perspectives on the future of radar interferometry. The objective of the review is for the reader to develop the physical understanding necessary to calculate an interferogram and the geophysical intu-ition necessary to interpret it.
Sheeting joints are extensive fractures that typically develop parallel to natural slopes. Embryonic sheeting joints initially
constitute channels for water flow and then become the focus for weathering and sediment infill accompanied by progressive
deterioration and dilation. Slabs of rock fail along them periodically because of their adverse orientation and long persistence.
They are however rough and wavy and these characteristics contribute highly to their shear strength and improve their stability.
This paper reviews several landslide case histories and on the basis of these provides guidelines for characterising sheeting
joints and determining their shear strength. Engineering options for stabilising sheeting joints in natural and cut slope
configurations are then examined with reference to case examples.
KeywordsSheeting joint origins–Shear strength–Landslides–Engineering measures–Roughness characterisation
Distributed environmental monitoring with wireless sensor networks (WSNs) is one of the most challenging research activities faced by the embedded system community in the last decade. Here, the need for pervasive, reliable and accurate monitoring systems has pushed the research towards the realization of credible deployments able to survive in harsh environments for long time. Design an effective WSN requires a good piece of engineer work, not to mention the research contribution needed to provide a credible deployment. As a matter of fact, to solve our application, we are looking for a monitoring framework scalable, adaptive with respect to topological changes in the network, power-aware in its middleware components and endowed with energy harvesting mechanisms to grant a long lifetime for the network. The paper addresses all main aspects related to the design of a WSN ranging from the -possible- need of an ad-hoc embedded system, to sensing, local and remote transmission, data storage and visualization; particular attention will be devoted to energy harvesting and management aspects at the unit and network level. Two applications, namely monitoring the marine environment and forecasting the collapse of rock faces in mountaineering areas will be the experimental leitmotiv of the presentation.
Sedimentation of the Montserrat fan-delta occurred during Bartonian/Priabonian times as a response to basement uplift due to transpressive faulting in the Catalan Coastal Ranges. The sediments are heavily fractured as a result of post-Middle Eocene tectonism associated with subsequent movements along the Catalan Coastal Ranges. By use of cross-cutting relations, mineralisation, fracture morphologies and kinematic indicators, relative dating of the fracture sets, and correlation to regional tectonic stresses have been performed. NNE-SSW-oriented fractures (Set A) are suggested to initiate during Rupelian time, as a system of sub-vertical (Mode I) and conjugate (Mode II) fractures, which indicate vertical SZ = σ1 and WNW-ESE-oriented Sh = σ3. During Middle to Late Oligocene times several episodes of fracturing occurred within the Montserrat fan-delta. Reactivation of Set A (NNE-SSW) fractures by sinistral oblique displacement, was associated with shift in principal stress from vertical SZ = σ1 to a horizontal N-S-oriented stress SH = σ1. Conjugate fractures (Set BNE and Set BNW oriented, respectively, NE-SW and NW-SE) developed as a response to a sub-horizontal approximately N-S-oriented SH = σ1. Set C fractures (oriented WNW-ESE) characterize orthogonal fracture patterns with Set A fractures, suggesting that Set C represents the younger generation. Observations of Set C fractures in the southeasternmost part of the Montserrat fan-delta prove reverse displacement, and transport towards the north-northeast, indicating a horizontal NNE-SSW-oriented SH = σ1, east-westerly-oriented Sh = σ2, and vertical SZ = σ3. Changing stress situations in the Montserrat fan-delta during Oligocene times correspond with successive change in the regional stress. A second phase of reactivation of Set A occurred during latest Oligocene-Early Miocene times. Hanging-wall blocks faulted down-to-the-east propose vertical SZ = σ1 and WNW-ESE-oriented Sh = σ3 during this phase, which is most likely to be correlated with the regional latest Oligocene-Early Miocene extension in NE Spain.