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Impact performance of unreinforced and geogrid-reinforced rockfall protection embankment
Abstract
This study designs and analyzes a Rockfall Protection Embankment (RPE) for an unstable slope in the Indian state of Mizoram. Initially, an in-depth trajectory analysis of the site is conducted to determine impact velocity, bounce height, and kinetic energy of falling rocks. Subsequently, the dimensions of three RPE variants-unreinforced, primary geogrid-reinforced, and secondary geogrid-reinforced configurations are determined based on literature and guidelines. Dynamic analyses are performed on these RPE variants using three-dimensional Finite Element software, PLAXIS 3D. The assessments consider multiple direct impacts and rebound impacts involving the maximum evaluated kinetic energy. Performance is assessed by examining maximum and residual deformations, mobilized tensile forces within geogrid layers, and the number of impacts the RPEs can withstand before reaching a deformation threshold. The results show that the reinforced RPE configurations exhibit significantly enhanced performance, withstanding nearly 20-43 times more impacts than unreinforced ones under both direct and rebound impact conditions. The inclusion of reinforcement layers notably improves the RPEs' ability to mitigate deformations by providing a confining effect to the soil mass and dissipating a part of the impact energy through the geosynthetics' strain and frictional resistance, thus making them more effective for rockfall protection.
... At the end of the 1980s, advancements led to the development of geosynthetic-reinforced earth structures capable of absorbing higher impact energies, reaching levels of up to 100 MJ (Morino and Grassi 1990;Descoeudres 1997). The inclusion of geosynthetics in these earth structures enhances their shock-absorption capability and extends their design life (Peila et al. 2007;Maheshwari et al. (2024a;2024b). ...
... Kundu et al. (2022) identified a comparable trend in their examination of realscale studies on RPEs (Burroughs et al. 1993;Yoshida 1999;Peila et al. 2000Peila et al. , 2002Peila et al. , 2007Ronco et al. 2009Ronco et al. , 2010Maegawa et al. 2011;Peila 2011;Lambert et al. 2014;Korini et al. 2021). This trend is depicted in Fig. 7. Furthermore, Maheshwari et al. (2024a;2024b) compiled the design steps for establishing the necessary size of the RPE, drawing upon recommendations from IS: 14,458 (Part-1) (1998), IRC: HRB (2014), UNI (2012), and an extensive review of the literature. These design steps, depicted as a flow chart in Fig. 8, include checks for the efficacy of the RPE section based on criteria recommended by IRC: HRB (2014) and Lambert and Kister (2018), focusing on block interception height and the energy absorption capability of the RPE. ...
... Figure 17 indicates that the RPE responses at 60 kJ, 100 kJ, and 500 kJ energy levels align well with the trends observed in the literature. A similar trend was noted when plotting the RPE response reported in a previous study by the authors (Maheshwari et al. 2024a). However, at the higher energy level of 1000 kJ, comparatively lower normalized deformation values are observed. ...
Rockfall is a significant hazard in the Himalayan regions of India, threatening lives and property. Rockfall Protection Embankments (RPE) offer a solution by intercepting falling rocks. This study provides a comprehensive performance assessment of a geosynthetic-reinforced Rockfall Protection Embankment designed for a rockfall-prone slope along National Highway-44 in Jammu and Kashmir, India. This particular segment of the arterial road, located in the lesser Himalayan region, is renowned for its high susceptibility to rockfall events. Slope geometry and material parameters are determined through site and laboratory characterization. These data are then utilized to estimate rockfall impact forces using statistical rockfall trajectory analyses. For the estimated trajectories and impact forces, the RPE is designed following available guidelines and insights from reported real-scale impact studies. The RPE's response to rockfall impacts of varying energies and different impact locations is then investigated using dynamic analyses through the three-dimensional finite element platform, PLAXIS 3D. The results demonstrate that the RPE can effectively withstand not only the estimated site-specific impact energy but also substantially higher energy levels. The presence of geogrid reinforcement efficiently localizes deformations and resulting stresses within the impacted zone, limiting damage to the remaining portion of the RPE. Reinforced RPE sections also exhibit the capability to regain stability after being impacted. Impact location is identified as a critical factor, with the top-third portion posing the greatest risk to the structural integrity of the protection structure. The RPE is 100% effective at preventing rock blocks from reaching highways and is significantly more cost-effective than other measures like catchment ditches and flexible barriers. This study provides valuable insights for the site-specific design and performance of rockfall protection embankments.
... For soil, the values of E 50ref , ϕʹ, cʹ, and γ are derived from laboratory tests conducted on the local soil (refer Table 3). The E oedref at p ref of 50 kPa is considered equal to E 50ref , and E urref is taken twice of E 50ref [53,54]. The dilation angle of the soil, ψ, is determined as the difference between the peak and residual friction angles obtained from shearing tests. ...
This study presents a site-specific design for a cushioning system in a rock-shed tunnel proposed for the Udhampur-Ramban section of National Highway 44 in Jammu and Kashmir, India. Located in the lesser Himalayas, the region is highly vulnerable to rockfall events. Slope and rock properties were characterized through site investigations and laboratory testing, and these data were used to estimate rockfall impact energies using statistical trajectory analyses. Two cushion systems were evaluated: a local soil-based cushion and a combined expanded polystyrene (EPS) geofoam-local soil cushion, using dynamic finite element analyses. Laboratory tests determined the properties of local soil and EPS at densities of 16, 20, and 30 kg/m³. These parameters were then input into numerical simulations to assess the performance of the cushioning systems and determine the optimal configuration that would limit roof-slab deformation within serviceable limits. The results show that a soil-only cushion is insufficient to prevent slab deformation under rockfall impacts. Increasing soil thickness reduces deformation but adds excessive dead load. The most effective solution was a 2 m layer of EPS (30 kg/m³) combined with a 0.3 m soil layer. These findings offer valuable insights into cushioning system performance, aiding the design of rock-shed tunnels in rockfall-prone areas.
... Up to now, the induced variability in response of rockfall protection structures has mainly been addressed focusing on their deformation or deflection, load transmission and failure (Breugnot et al. 2016;Mentani et al. 2016;Bourrier et al. 2016;Toe et al. 2018;Previtali et al. 2021;Lambert et al. 2021;Douthe et al. 2022;Qi et al. 2022;Maheshwari et al. 2024). It is here proposed to address the variability in structure response in terms of energy dissipation. ...
This article focuses on the key issue of energy dissipation in passive rockfall protection structures when exposed to impact by a rock block. As an application case, a structure consisting of a wall made of interconnected concrete blocks is considered. A Non-Smooth Contact Dynamics (NSCD) model of this structure was previously developed and calibrated with respect to the spatio-temporal impact response obtained from real-scale impact experiments. The NSCD model accounts for energy dissipation due to friction between the system bodies and to plastic strain at contacts. The energy dissipation computation method is detailed and its exactness is demonstrated considering two impact cases. The evolution with time of energy dissipation by each dissipative mechanism provides insights into the global structure response with time in terms of displacement and contact force amplitude. The influence of the model parameters on the contribution of these two dissipative mechanisms is evaluated. A ratio between energy dissipation by friction to energy dissipation by plastic strain is proposed as a criterion for structural response evaluation. The variability in energy dissipation varying the impact conditions is addressed. In the end, this study reveals the benefits derived from a precise quantification of energy dissipation in passive rockfall protection structures. Beyond the considered application case, such an approach focusing on energy dissipation opens up promising prospects for improving the design of all passive rockfall mitigation structures.
This study assesses rockfall risk and the effectiveness of passive protection measures using trajectory analyses on a vulnerable Himalayan slope along the Manali–Leh Highway in Northern India. Trajectory analyses employ two methods: The rigorous ‘rigid body’ approach, considering rock shape and size, and the simplified ‘lumped mass’ approach, treating rock blocks as a single spherical mass. Using RocFall 2D, the analyses assess 15,500 potential rockfall paths to determine translational velocities, kinetic energies, and bounce heights. These results are then used to evaluate hazard levels on the considered section of the highway and for the dimensioning and positioning of protective measures. The findings of the trajectory analyses reveal that the degree of sphericity of rock shapes significantly influences runout distances, rotational velocities, and associated kinetic energies. Higher sphericity, observed in circular and hexagonal-shaped rocks, corresponds to increased runout distances, rotational velocities, energies, and subsequent hazards to the roadway. Moreover, bounce height is not only contingent on shape but also on intricate interactions involving slope parameters, rotational and translational velocities, and block orientation upon impact. Consequently, this study emphasizes the vital role of considering rock shape when interpreting trajectory analysis results. Using critical values derived from trajectory analyses, the study formulates designs for two passive rockfall protection measures: rockfall protection embankment (RPE) and flexible barriers, following relevant standards and literature. Given the absence of standardized RPE designs, an extensive review of experimental studies on RPEs guided the development of a design methodology aligned with IRC: HRB (2014) recommendations. A thorough evaluation of the two countermeasures shows that both RPEs and flexible barriers effectively protect against rockfall risk. However, RPEs prove less practical due to space constraints at the slope’s base. These study findings will assist designers and industry practitioners in adopting suitable methodologies for planning and designing passive rockfall protection measures.
To evaluate the ultimate capacity of the ground reinforced embankments, most of the research have been focused on high levels of impact energy. However, many existing embankments have been impacted by several blocks without collapsing. The residual characteristics and efficiency of post-impact embankments under low-energy impact are researched in this paper. Model tests of two types of embankments are compared to investigate the deformation performance and damage evolution of embankments. A simplified analytical approach, based on the test results and the energy method, is proposed to assess the residual efficiency of the post-impact embankments. Furthermore, the adverse impact conditions are analyzed by numerical simulation. The results show that the damage evolution of the embankments goes through three phases, uphill face compression, downhill face displacement, and collapse. Compared with experimental data, the stability calculation method is proved to be feasible. It is also found that the impact location and inclination of the blocks affect the deformation and stability of the embankments significantly. These points should be beneficial to the design of ground reinforced embankments.
In this study, an optimization method based on numerical rockfall simulation is proposed to determine the layout design of a protection embankment, including its position and length on a construction site. Stopping rockfalls farther away from the slope toe requires a lower embankment since the movement of the rockfall decreases with the runout distance and, at the same time, a longer embankment due to the lateral deviation from the central rockfall path. This complicated relation makes the layout design difficult. The proposed method mainly focuses on two design parameters: the distance from the slope toe and the embankment length. With regard to these two decision variables, an optimization problem is formulated, with the aim of minimizing the installation cost of an embankment, which is subject to the global performance requirement for arresting rockfalls. Solving this problem leads to the identification of an optimal layout plan for an embankment at the site of interest. The optimization result is objective and quantitative; therefore, it allows us to choose the best one from several embankment types with different design conditions and costs. To evaluate the performance of the proposed method, an application example was conducted using a virtual rock-slope model. In this application, we employed the discrete element method for the rockfall trajectory simulations. The optimization process was then conducted on 50 different groups of computed trajectories to determine the most economical and stable construction plan among several embankment types and all possible layouts. The reliability of the result was also supported by the fact that the variations in the optimal solutions were reduced with the increase in the sample size.
This article presents a numerical model coupling the finite difference method and discrete element methods (FDM, DEM) for simulating the response of cellular geostructures to impacts. DEM is used in the vicinity of the impacted area while FDM is used far away. The continuity between the DEM and FDM domains is insured using the edge-to-edge method. The numerical parameters are calibrated based on compression and impact experiments conducted on elementary cells. Numerical simulations at the structure scale are compared with real-scale experimental data. The response of the structure is addressed varying the impact conditions. The projectile shape and the position of the impact point appear to be the most influential parameters.
This paper deals with geogrid-reinforced artificial barriers used as mitigation works against debris avalanches. Deformable Geosynthetic-Reinforced Barriers (DGRB) can be made of coarse-grained materials reinforced by high tenacity polyester (PET) geogrids, wrapped around the facing and arranged in layers. The peak dynamic impact pressure is here calculated as the sum of a landslide velocity-related component and a static component dependent on landslide height. Dynamic analyses are carried out through the commercial Finite Differences Method code (FLAC, Itasca) capable of adequately reproducing small and large displacements of the impacted barrier. The soil is modeled as elastic perfectly-plastic non-associative granular soil, the geogrids are simulated as traction-resistant, and the iron mesh framework is modeled as beam elements resistant to both traction and bending. Frictional interfaces are considered at soil-geosynthetic contacts. The displacements of specific control points and the global behaviour of the barriers are computed versus time. Tensile stresses in the geosynthetics are evaluated for different combinations of materials. Out of three geometries of the barrier, the more massive with the steeper impact front is outlined as the best choice. More deformable geosynthetics appear to be more effective in dissipating the impact energy inside the barrier.
This paper deals with geosynthetics-reinforced barriers conceived as protection works against debris avalanches, which are a dramatic threat for human life and structures. This kind of barrier is intended to be deformable under the impact and is here analysed for various cases of landslide velocity, impact duration and peak impact pressure. The latter is the sum of a dynamic component (velocity-dependent) and a static component (height-dependent). The barrier is conceived as a multilayered embankment, reinforced by geogrids wrapped around the facing. Both static and dynamic stress–strain analyses are performed through a commercial FEM code (Plaxis v. 8.5) to simulate the deformation mechanisms and the ultimate limit states. Four geometries of the barrier and four combinations of the materials are considered. The core of the barrier is made of coarse-grained material modelled as elastic-perfectly plastic with a non-associative Mohr–Coulomb yield criterion. The facing is 60° to 80° steep and sustained by an iron mesh here simulated as an elastic beam element. The geogrids are modelled as elastic traction-resistant elements. Frictional interfaces are considered at the soil–geogrid and the soil facing contacts. The displacements of the inner points and the global behaviour of barriers are evaluated over time. Out of four newly defined deformation mechanisms, local, global, combined or compound, only three principal scenarios are outlined: i) a global displacement along the base of the barrier, ii) a local yielding of soil combined with a global displacement of the barrier, or iii) a shifting of the reinforced layers along the geogrids with an acceptable performance of the whole barrier. Such results are discussed in relation to the geometry and the materials of the barrier, also taking into account the features of the impact loading.
This study investigates the mechanism of rockfall impact against a granular soil buffering layer above a concrete/rock shed via numerical simulations by discrete element method (DEM). The soil buffering layer is modeled as a loose packing of polydisperse spherical particles, while the bottom concrete/rock shed is simulated by a layer of fixed particles. The rock blocks of various ellipsoidal shapes are represented by an assembly of densely packed and bonded spherical particles. The DEM model was employed to investigate the dynamic interaction between the rock block and the soil buffering layer, including the impact force, penetration depth and bottom force. During the rockfall impact, the force chains occur immediately at the impact area and then propagate radially downward into the soil buffering layer. The force waves vanish gradually as most of the impact energy was absorbed and dissipated by the loose buffering soil particles. The numerical results show that the maximum impact force acting on the rock block increases, while the corresponding penetration depth decreases linearly with the block sphericity. The maximum force acting on the bottom concrete/rock shed is approximately twice the maximum impact force acting on the rock block, showing apparent force amplification of the soil buffering layer. The ratio between these two forces is almost independent of the rock block sphericity. These findings can finally contribute to the design of effective soil buffering layer for concrete/rock sheds.
Rockfall poses risk to people, their properties and to transportation ways in mountainous and hilly regions. This catastrophe shows various characteristics such as vast distribution, sudden occurrence, variable magnitude, strong fatalness and randomicity. Therefore, prediction of rockfall phenomenon both spatially and temporally is a challenging task. Digital Terrain model (DTM) is one of the most significant elements in rockfall source identification and risk assessment. Light detection and ranging (LiDAR) is the most advanced effective technique to derive high-resolution and accurate DTM. This paper presents a critical overview of rockfall phenomenon (definition, triggering factors, motion modes and modeling) and LiDAR technique in terms of data pre-processing, DTM generation and the factors that can be obtained from this technique for rockfall source identification and risk assessment. It also reviews the existing methods that are utilized for the evaluation of the rockfall trajectories and their characteristics (frequency, velocity, bouncing height and kinetic energy), probability, susceptibility, hazard and risk. Detail consideration is given on quantitative methodologies in addition to the qualitative ones. Various methods are demonstrated with respect to their application scales (local and regional). Additionally, attention is given to the latest improvement, particularly including the consideration of the intensity of the phenomena and the magnitude of the events at chosen sites.
Rockfall is an extremely rapid process involving long travel distances.
Due to these features, when an event occurs, the ability to take evasive
action is practically zero and, thus, the risk of injury or loss of life
is high. Damage to buildings and infrastructure is quite likely. In many
cases, therefore, suitable protection measures are necessary. This
contribution provides an overview of previous and current research on
the main topics related to rockfall. It covers the onset of rockfall and
runout modelling approaches, as well as hazard zoning and protection
measures. It is the aim of this article to provide an in-depth knowledge
base for researchers and practitioners involved in projects dealing with
the rockfall protection of infrastructures, who may work in the fields
of civil or environmental engineering, risk and safety, the earth and
natural sciences.
Models can be useful tools to assess the risk posed by rockfall throughout relatively large mountainous areas (>500 km 2), in order to improve protection of endangered residential areas and infrastructure. Therefore the purpose of this study was to summarize existing rockfall models and to propose modifications to make them suitable for predicting rockfall at a regional scale. First, the basic mechanics of rockfall are summarized, including knowledge of the main modes of motion: falling, bouncing and rolling. Secondly, existing models are divided in three groups: (1) empirical models, (2) process-based models and (3) Geophysical Information System (GIS)-based models. For each model type its basic principles and ability to predict rockfall runout zones are summarized. The final part is a discussion of how a model for predicting rockfall runout zones at a regional scale should be developed. A GIS-based distribution model is suggested that combines a detailed process-based model and a GIS. Potential rockfall source areas and falltracks are calculated by the GIS component of the model and the rockfall runout zones are calculated by the process-based component. In addition to this model, methods for the estimation of model parameters values at a regional scale have to be developed.
Non-linear time domain site response analysis is widely used in evaluating local soil effects on propagated ground motion. This approach has generally provided good estimates of field behavior at longer periods but has shortcomings at relatively shorter periods. Viscous damping is commonly employed in the equation of motion to capture damping at very small strains and employs an approximation of Rayleigh damping using the first natural mode only. This paper introduces a new formulation for the viscous damping using the full Rayleigh damping. The new formulation represents more accurately wave propagation for soil columns greater than 50 m thick and improves non-linear site response analysis at shorter periods. The proposed formulation allows the use of frequency dependent viscous damping. Several examples, including a field case history at Treasure Island, California, demonstrate the significant improvement in computed surface response using the new formulation.
Among the different natural hazards, rockfall has an important place even though other natural hazards could affect more people or have greater consequences. The phenomenon may be further classified according to the size of the largest blocks and the total rock mass involved. The risk management procedure can be divided into (i) hazard identification and description, (ii) hazard assessment and (iii) risk management and treatment. Initiation zones of rockfall are identified and characterized by using geodetic, geomorphic, geotechnical and historical data. Trajectories are analyzed and boulder impacts are modeled to identify endangered areas. A variety of methods exist to estimate the frequency of rockfall events. Finally, hazard maps are produced that indicate the hazard level based on the intensity and probability of rockfall events. Together with indications on the occupancy and vulnerability of buildings and infrastructure, risks can be calculated and compared with acceptable values for new projects and tolerable ones for existing assets. The most effective countermeasure is land-use planning to avoid dangerous areas. If this is not possible or existing assets have to be protected, geotechnical and structural mitigation measures are justified. They cover measures in the initiation zone, along the propagation path and in the deposit zone. The types of structure used are flexible barriers, galleries, embankments and dams, depending on the position of the protective measure and the available space, the energy to be absorbed and other functions the structures should fulfill. Structures are dimensioned to withstand the impact of a design block, taking into account the damping effect of a possible cushion layer and the dynamic response of the structure itself.
The prediction of the effects of rockfall on passive protection structures, such as reinforced ground embankments, is a very complex task and, for this reason, both full-scale tests and numerical dynamic modelling are essential.
A systematic set of numerical FEM models, developed in the dynamic field, has been implemented in this work to evaluate the conditions of an embankment that has been subjected to the impact of rock blocks of various sizes at different speeds. These analyses have permitted design charts to be obtained. Furthermore, a simplified analytical approach, based on an equilibrium analysis, has been proposed and its results are compared with numerical data in order to assess its feasibility. A good correspondence between the results has been obtained.
This chapter discusses the kinematics of a rockfall which forms the framework for the selection of mitigation strategies. It is followed by a detailed discussion of various mitigation strategies used to arrest or divert the falling rock and reduce the economic damage and loss of lives in mountainous regions. The mitigation strategies of rockfall protection can broadly be categorised into active and passive measures. Mitigation practices using draped meshes, anchors, and grouting are active measures, while practices using embankments, flexible barriers, rock sheds, catch ditches, and forests are categorised under passive measures. The various design approaches typically used for analysing and designing these mitigation measures are also discussed briefly in this chapter. A concise discussion of the limitations of these measures is also provided to aid the practitioners in selecting an adequate mitigation strategy. The primary objective of this chapter is to provide a thorough understanding of the rockfall and current mitigation practices employed in the field for the practitioners involved in hilly infrastructure projects. The comprehensive discussion on the current rockfall mitigation practices could also serve as a potential framework for future improvements in their respective design.
This paper presents an experimental investigation of the effectiveness of longitudinal and transverse members of bitumen-coated polyester-yarn geogrids under low normal stress using large-scale pullout apparatus. The tests first compare the pullout behavior of a geosynthetic sheet with that of the geogrid. It then compares the pullout behavior of geogrids with different spacing of longitudinal and transverse members. The results show that under low normal stresses, the behavior of the sheet and the geogrid is comparable. The spacing between transverse ribs displays very little influence on peak pullout resistance of the geogrids under low normal stress. Increase in spacing between longitudinal ribs reduces the interaction between them. As a result, after the critical spacing of 70 mm determined for present test conditions, the total pullout resistance of the geogrid specimens is the product of the pullout resistance per rib with the number of longitudinal ribs in the respective specimens.
Rockfall hazard in mountainous areas requires the construction of protective structures for the buildings or transport facilities. Reinforced soil embankments can be effective protections against rockfalls due to the combination of the damping characteristics of the soil and the tensile resistance of the reinforcements. Following the advances in soil reinforcements, the research is ongoing for this type of structures aiming to optimize their shape and reinforcement design. In order to study the influence of the different geosynthetics design, two reinforced soil embankments are tested experimentally. The embankments had vertical facings and a slenderness ratio of two with the purpose to reduce the footprint of the conventional trapezoidal shape. Embankment 1 had two vertical layers of geogrids that divided its cross section in three equal parts, while Embankment 2 had multiple geogrid strips installed horizontally close to the front facing. Horizontal impact tests are performed on the two embankments using reinforced concrete blocks as impactors with the aid of a pendulum device. Several instruments and sensors are used to monitor the behavior of the embankments, namely accelerometers, pressure sensors, strain gauges, rapid cameras and a laser scanner. During the tests, the two embankments experienced local shearing at the impact position and overall backward leaning. Moreover, a waves' propagation effect is observed during the first moments of the impact at the sensors installed in the embankments. The speed of the propagation of these waves appears to be influenced by the reinforcement design of the embankments. After the tests, Embankment 2 was less deformed than Embankment 1, which is attributed to their different reinforcement design. According to the strain gauges measurements, the geogrids of Embankment 2 were better mobilized in the vicinity of the impact compared to the ones of Embankment 1. These tests showed that the geogrids installed in horizontal position close to the front facing are more efficient compared to the ones installed vertically and deeper in the embankment.
Rockfall is a critical problem in the hilly regions. The Lengpui-Aizawl highway has witnessed many rockfalls and other types of landslide events in the past few years. This highway is imperative to the area as it links the Lengpui airport with the city. Most of the rock slopes along this highway are prone to rockfall, thus requires proper investigation. In this study, an investigation into the rockfall hazard was carried out on the nine rock slopes using the rockfall hazard rating system (RHRS) approach along NH-44A. Based on an extensive field investigation, the analysis shows that two out of nine slopes are more hazardous than the others as the RHRS score for these slopes is higher than 500. Furthermore, rockfall simulations were performed for hazardous slope to quantify the risk in terms of bounce height, velocity, kinetic energy and maximum reach of falling rock blocks. The simulation result reveals that vehicles on the roadway are under continuous threat. The potential falling blocks have a kinetic energy of 196 kJ which is enough to damage the buildings, vehicles and fatalities.
Roadways are the lifeline for any city, especially in hilly regions. The increase in population and road constructions has led to the destabilization of the slopes resulting in mass movement. Anisotropic rockmass, whose behaviour is largely dependent on the planes of weakness, was simulated using 3DEC. The three-dimensional discontinuum modelling technique provides the most rigorous analysis of the failure process and deformation in the anisotropic rock. However, due to the limited capacity of the software, it is impossible to include all the discontinuities implicitly in numerical simulation. This paper provides a methodology for the application of Ubiquitous-Joint models on a field scale to include the anisotropic behaviour of rockmass. After identifying the failure-prone area using rigorous 3DEC slope stability analysis, rockfall analysis was also carried out to identify the maximum run-out, bounce height and total kinetic energy of falling rock blocks in the same section of the slope. 3DEC results show the maximum total displacement of 2.6 cm with a maximum velocity of 0.25 m/s, which confirms the instability in the slope. The rockfall simulation reveals that the falling rock blocks can hit the vehicle on the roadway with the kinetic energy of 58.5 kJ that makes this roadway unsafe.
Three-dimensional finite-element analyses of the inclined pullout behavior of geogrids embedded in three types of anchors (run-out, I-type, and L-type) are presented in this paper. The soil behavior is represented by the elastic–perfectly plastic Mohr–Coulomb (MC) model and the geogrid behavior with linear-elastic plate elements. The geogrid is modeled using the geometrical and index properties of the geogrid used in model tests. The predicted results from the finite-element analyses are compared with the corresponding model test results. The peak pullout force values for different values of inclinations and types of anchors are predicted with reasonable accuracy by the present numerical model. However, the results show that the post-peak response for run-out and I-type anchors and the stiffness in the case of I-type and L-type anchors are not satisfactorily modeled.
This paper proposes a 3D model for analyzing the rockfall trajectory within the framework of contact mechanics and rigid body dynamics, focusing on arbitrary shapes of the falling rock and terrain. Firstly, the sphericity and the concavity and convexity are defined to quantitatively describe the overall shape and local appearance of often-observed falling rocks, respectively. A generation algorithm is then proposed to generate falling rock and terrain with arbitrary shapes. The surfaces of the generated falling rock and terrain model are both meshed by triangular elements. A contact searching algorithm as well as a bilinear model for contact collision are presented to solve the interaction between the falling rock and terrain. Validated by available field test data, it is demonstrated that the proposed approach could simulate the four motion modes of rockfall such as falling, bouncing, rolling and sliding, as well as the transition between them.
This paper presents the details of an experimental investigation using large-scale inclined pullout apparatus on sheet geosynthetic and geogrid embedded in run-out, I-type, and L-type anchors. The influence of the type of sand on the behaviour of the sheet and the geogrid is also investigated. The results show that in both the sheet and the geogrid, I-type anchor provides approximately 50% and L-type anchor provides 90% higher pullout force than the run-out anchor. The maximum pullout force increases by more than 20% as the inclination of pullout force increases from 0° to 30° for both the sheet and the geogrid.
Stability of geosynthetics along slopes in covers and liners of landfills depends partly on their tensile strength and partly on the efficiency of anchors holding the geosynthetics at berms or top of the slope. The pull induced in these geosynthetics is in an inclined direction parallel to the slope. But due to difficulty in modelling of inclined pullout behaviour experimentally, very few studies have so far been conducted on geosynthetics embedded in anchor trenches. This paper presents details of a device that can perform inclined pullout tests on geosynthetics at variable inclinations. Since geogrids are widely used as veneer reinforcement, inclined pullout tests are conducted on geogrids embedded in run-out, I-type and L-type anchors in sand. The maximum pullout force in geogrid increases by more than 20% as the pull inclination increases from 0° to 20° in all the three types of anchors. The geogrids exhibit markedly different force-displacement behaviour for the three types of anchors, though the length of reinforcement remains the same. The peak pullout force for I-type anchor was 1.6-1.7 times higher, and L-type anchor was 2 times higher than that of run-out anchor at all pullout inclinations.
Urban traffic characteristics are examined along with the various available current approaches to controlling traffic efficiently at signalized intersections. Fixed-time, central, and distributed real-time control approaches are considered. It is determined that the best method of control varies with network and flow conditions. It is concluded that for smooth traffic and uncomplicated networks that provide good opportunity for progression, a centralized quasi-real-time model such as the split, cycle, and offset optimization technique (SCOOT) is appropriate. However, when faced with significant demand fluctuations or interference from transit or emergency vehicles, a distributed real-time model will be required. The paper recommends use of a fully distributed model to deal with such conditions, at least for the foreseeable future until appropriate hierarchical models can be developed.
This article first proposes a literature-based criterion for evaluating the capacity of protection embankments in resisting rockfall-induced impacts. The criterion is intended to help stakeholders and public authorities expediently evaluate the strength of existing embankments. It is intentionally kept simple so that it can be applied to any type of embankment and even in those lacking design documentation. The criterion was developed based on available data from real-scale impact experiments conducted worldwide on various types of embankments. It relates the embankment downhill face deformation to the block-incident kinetic energy, differentiating reinforced and non-reinforced embankments. This criterion is then applied to a set of ninety-eight embankments built in France and Switzerland. While the dynamic loading was seldom considered for their design, it appears that >50% of these embankments meet the criterion. This held evaluation, more importantly serves to identify the nearly one-third of this set for which the application of this criterion suggests an excessive downhill deformation, inviting further investigations with respect to their impact strength and performance expectations
en In the course of several research projects carried out at the Lucerne University of Applied Sciences and Arts, the effect of block rotation on impact on protection embankments has been investigated. The occasion for these experimental studies was the conflicting statements in the literature about the influence of block rotation on impact and the different and mostly very simple models for the design and sizing of such structures. Considering this, both small‐scale quasi‐2D tests and half‐scale 3D tests were performed and evaluated. The test results show that block rotation, which has until now been neglected in the design and sizing of rockfall protection embankments, is actually of great significance. Three rules for the geometry of such structures could be derived from the test results.
Abstract
de An der Hochschule Luzern wurde im Rahmen von mehreren Forschungsprojekten der Einfluss der Blockrotation beim Impakt auf einen Schutzdamm untersucht. Anlass für diese Untersuchungen waren zum einen die widersprüchlichen Aussagen in der Literatur im Hinblick auf den Einfluss der Blockrotation beim Impakt und zum anderen unterschiedliche, meist sehr einfache Modelle für den Entwurf und die Bemessung von solchen Bauwerken. Vor diesem Hintergrund wurden sowohl kleinmaßstäbliche Quasi‐2D‐Versuche als auch halbmaßstäbliche 3D‐Versuche durchgeführt und ausgewertet. Die Versuchsergebnisse zeigen auf, dass der Blockrotation, die bisher beim Entwurf und der Bemessung von Steinschlagschutzdämmen vernachlässigt wurde, eine große Bedeutung zukommt. Aus den durchgeführten Versuchen konnten drei Regeln für die Geometrie solcher Bauwerke abgeleitet werden.
The applicability of shredded tire as an economical alternative for conventional granular soil backfill for retaining walls was investigated by conducting geotechnical and structural designs as well as finite element simulations. A literature survey was conducted to compile and document the engineering properties of shredded tire. It was found that the key geotechnical engineering properties vary significantly with shred size and shredding method. Then, a gravity-cantilever retaining wall was designed for dynamic loading conditions considering seismic design parameters corresponding to the Charleston, SC area. Geotechnical design revealed a longer toe compared to heel for shredded tire backfill to maintain stability; however, a shorter footing was needed to maintain overall stability compared to that of granular backfill. Conventional designs and finite element simulations showed significant reductions in computed horizontal deflection at the tip of the wall, structural demand in terms of maximum shear force and bending moment, and construction cost in terms of excavation and material when shredded tire was used as the backfill. Upper and lower bound curves of maximum shear force and maximum bending moment in the stem were also produced based on the results of parametric studies conducted by varying the friction angle and cohesion of shredded tire, and the amplitude and mean period of the input motion.
Für die Bemessung von Steinschlagschutzdämmen gibt es derzeit keine dem Stand der Technik entsprechenden und in der Praxis anwendbaren Methoden. Häufig werden für Steinschlagschutzprojekte mit hohen Bemessungsenergien Steinschlagschutzdämme errichtet, nachdem die mittels Eignungstests nachgewiesene Energieaufnahmekapazität von Steinschlagschutznetzen derzeit auf 8.000 kJ beschränkt ist. Der erdstatische Nachweis einer dynamischen Einwirkung auf Dammbauwerke ist mit statischen Methoden derzeit nicht möglich, da geeignete Methoden zur Ermittlung einer statischen Ersatzkraft fehlen. Die bestehenden empirischen Ansätze zur Ermittlung von statischen Ersatzkräften bei Steinschlagbelastungen bauen auf Impaktversuchen in Dämpfungsschichten über biegesteifen Stahlbetonkonstruktionen auf und können nicht auf reine Erdbauwerke übertragen werden. Um einen praxistauglichen Bemessungsansatz für solche Erdbauwerke zu erstellen, die teilweise großen dynamischen Belastungen ausgesetzt sind, wurden Modellversuche an Dämmen verschiedener Bautypen und Dammgeometrien im Maßstab 1:33 durchgeführt. Dabei konnten die durch den dynamischen Stoß verursachten Bruchkörper bei verschiedenen Lastfällen bestimmt werden. Basierend auf den Ergebnissen der Modellversuche wird eine Methode entwickelt, mit der in Abhängigkeit von geometrischen Parametern eines Entwurfsdamms unter Berücksichtigung verschiedener Bautypen (Erddämme und bewehrte Erde) eine statische Ersatzkraft ermittelt werden kann. Mit dieser statischen Ersatzkraft kann in weiterer Folge mit klassischen Nachweisverfahren ein Tragfähigkeitsnachweis für einen konkreten Lastfall eines Bemessungs-Steinschlagereignisses (Bemessungssituation BS 3 gemäß EC 7 – ÖNORM B 1997-1-1) geführt werden.
This paper considers the mechanics of rock boulders impacting on granular strata. The study is aimed at improving the numerical methods devoted both to describing boulder trajectories along slopes and designing preventive structures in mountain regions. The problem is analysed by using a simplified approach inspired by the lumped mass method. This is based on (a) the macro-element concept, (b) the definition of generalised stresses and displacements, and (c) delayed plasticity theory. Both vertical and inclined impacts on horizontal strata and vertical impacts on inclined slopes are discussed. The numerical results are obtained by using a finite difference numerical discretisation to integrate, over time, a coupled system of two-dimensional differential equations. Most of the input data requested by the model are basic and geotechnically meaningful, and comparison of the numerical results with the experimental data seems to be quite promising.
In Japan, slope disasters occur due to earthquakes, abnormal weather and inappropriate land development. It is important to identify safe and economical countermeasures against rockfall disasters. We developed a simple, long-lasting and low-cost structure with maximum impact dissipative action when stopping rockfall. In order to simulate rockfall impact, various energies of falling rocks were made to collide with real-scale protection structures. The new type of protection wall against rockfall using a ductile cast iron panel is an efficient barrier and has an effective dissipative function. It also has very good permeability. The structure is flexible and the design and construction can take into account of the natural environment and topographic features.
Infrastructures such as roads and railways as well as urbanised areas, in mountainside regions, can frequently be endangered
by rockfalls and, therefore, need to be protected against the impact of rolling blocks. Among the various protection works
that can be used, ground reinforced embankments can be considered a feasible technique. A set of full-scale tests on embankments
made of ground reinforced by geogrids are presented and discussed. The experiments were performed in a specifically designed
and constructed test facility, where concrete blocks up to 9,000kg in weight were thrown onto a geogrid reinforced embankment
at a speed of about 30m/s. Several embankments made of different geogrid types, different soils and construction layouts
were tested at different impact energy levels, permitting a quantitative assessment of the resistance impact of these structures.
The experimental results were compared with those obtained from a dynamic finite element method numerical model, and a good
agreement was obtained.
Reinforced soil structures can be used to protect infrastructures against rockfalls. An innovative way to implement such protection is to construct the front face using a cellular assembly. This paper focuses on the cellular scale, with the cell a complex heterogeneous material, composed of a wire netting box filled with rocky particles. The behaviour of a single cell was modelled using the discrete element method, thus accounting for the interaction between the rocky particles and the interaction between the box and the rocky particles. A constitutive model was developed and calibrated along confined compression loading paths, then preliminary elements of validation were obtained from the simulation of unconfined compression tests.
Rockfalls are a major threat to settlements and transportation routes in many places. Although the general protective effect of forests against rockfalls is currently not questioned, little is known about the ideal properties of a forest stand that provides good protection. Therefore, in this study the question was assessed of how mountainous forests may influence rockfalls of single boulders. An actual rockfall trajectory was measured, recorded, analysed and simulated with a rockfall model. Rockfalls into different forest scenarios were also modelled for the site. Results showed that the actual rockfall event can be well simulated. Furthermore, a completely forested slope reduces velocity and energy of the falling blocks much better than a sparsely forested slope. For the profile discussed in this paper, the largest effect upon falling 3 m 3 blocks was obtained with a high forest containing 350 trees per ha. The results confirmed common assumptions on ideal properties of a protective forest stand against rockfalls.
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