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... Landslides are the most critical type of geological disaster and have the characteristics of a wide distribution area, high frequency of occurrence, fast movement speed, and severe losses. Because of the uplift of the Qinghai-Tibet Plateau, the internal and external dynamic geological processes are enormously intertwined, and creating complex geological conditions and intense dynamic valley processes; these processes bring more uncertainty to the occurrence of landslides in the Yunnan-Tibet traffic corridor (Peng et al., 2004;Peng et al., 2020). Frequent landslides not only cause heavy casualties and property losses but also seriously affect the construction and safe operation of Yunnan-Tibet highways and planned corridors and restrict the development of the regional economy. ...
... The study area is located at the southeastern edge of the collisional extrusion zone between the Eurasian and Indian plates, and the regional tectonic line is spreading north-south under solid extrusion. In addition, the neotectonic movements are intense (Peng et al., 2004). The active fault zones mainly include the Dêqên-Zhongdian fault zone, the Batang fault zone, the Jinsha fault zone, the Lancang fault zone, and the Nujiang fault zone (Chai et al., 2021). ...
... The development of landslide hazards is affected by plate movement. The continuous uplift of the Qinghai-Tibet Plateau has created deep and steep river valley landforms, and the river valleys are often distributed along faults, resulting in the fragmentation of the bank slope rock mass and the development of fissures (Peng et al., 2004). In addition, the runoff on the bank slope surface is large. ...
The Yunnan–Tibet traffic corridor runs through the Three Rivers Region, southeastern Tibetan Plateau, which is characterized by high-relief topography and active tectonics, with favourable conditions for landslides. It is of great significance to identify the key predisposing factors of landslides and to reveal the landslide susceptibility in this area. A total of 2,308 landslides were identified as learning samples through remote sensing interpretation and detailed field surveys, and four machine learning algorithms involving logistic regression (LR), random forest (RF), naïve Bayes (NB) and multilayer perceptron (MLP) were compared to model the landslide susceptibility. Through the multicollinearity test, 13 influential factors were selected as conditioning factors. The area under the curve (AUC) values of LR, RF, NB and MLP models are .788, .918, .785 and .836 respectively, indicating that the four models have good or very good prediction accuracy in landslide susceptibility assessment along the Yunnan–Tibet traffic corridor. In addition, the elevation, slope, rainfall, distance to rivers, and aspect play a major role in landslide development in the study area. The susceptibility zoning map based on the best RF model shows that the areas with high susceptibility and very high susceptibility account for 12.24% and 6.72%, respectively, and are mainly distributed along the Jinsha River, the Lancang River and the G214 highway.
... Furthermore, other scholars have studied the time and space distribution characteristics of the ancient landslides from the upper reaches of the Yellow River, explained the root cause of this situation from the aspect of climate (Zhou 2010), and summarized the relationship between the ancient landslide blocking event and the evolution of the Yellow River (Guo 2017). Other findings have suggested that most of China's large-scale ancient landslides are distributed in the periphery of the Tibetan Plateau (Peng et al. 2004). Especially, the northeast margin is one of the areas where the ancient landslide is most developed. ...
... Therefore, the deep deformation of the regional crust is dominated by the overall uplift, supplemented by fold uplift. After the formation of the Yellow River and connection with the Longwu River system, the erosion of the broad Ushaped valley was dominated by oscillating lateral erosion supplemented by incisive erosion (Peng et al. 2004;Yin et al. 2013). Steep slopes with a height of 300-400 m were formed in this area. ...
The northeastern Tibetan Plateau exhibits steep topography and strong internal or external dynamic geological effect and is frequently subjected to strong earthquakes and heavy rainfall. The geological evolution has resulted in a wide distribution of ancient landslides, which has become a hotspot for studying ancient landslide formation and reactivation. In recent decades, several ancient landslides on both banks of the Longwu River, Qinghai Province, China were reactivated, causing serious economic losses and casualties. This study conducted remote sensing interpretation and ground surveys on these ancient landslides. Totally 59 ancient landslides were identified, and the formation mechanism, evolution process, and resurrection mechanism of the Longwu Xishan No.2 ancient landslide were analyzed by means of a detailed field geological survey, drilling, and series of experimental tests such as the particle size distribution test, the X-ray diffraction test and the mechanical properties test. The results show that the formation of these ancient landslides is closely associated with the uplift of the Tibetan Plateau and the erosion of the Longwu River. Firstly, the intermittent uplift of the Tibetan Plateau lead to the diversion and downcutting of the Longwu River basin, which forms the alternate slope topography with steep and slow slopes, thereby providing favourable topography and slope structure conditions for the formation of landslides. Secondly, 34.5% clay-mineral content in the Neoproterozoic mudstone with 32.7% particle size less than 0.005 mm, and the corrosion and softening effects of the Neogene mudstone with high clay mineral content under the erosion of water provides favourable material conditions for the formation of landslides. Thirdly, rainfall and human activities are the primary triggering factors for the revival of this ancient landslide group. It is revealed that the evolution process of the ancient landslides on both banks of the Longwu River can be divided into five stages namely tectonic rapid uplift slope formation, river erosion creep-sliding deformation, slope instability critical status, landslide failure-movement-accumulation, and slope reactivation under rainfall erosion and engineering excavation.
... The YR successively flows through the Tibetan Plateau, which is the youngest and fastest rising plateau in the world; the Chinese Loess Plateau, which is the only plateau that is growing and suffering strong erosion; and the North China Plain, which has dense population and severe subsidence ( Figure 1). The YRB is characterized by active tectonics, strong interior and exterior geological dynamics, peculiar geomorphological evolution processes, and complex disaster development patterns, leading it to be one of the areas with the most complex geological environments and most vulnerable ecological environments in China (Su and Yang, 1996;Peng et al., 2004Peng et al., , 2020. Moreover, the YRB is a complex system; the disasters in the YRB are "presented in rivers, formed in areas, and derived on land" . ...
... (2) This section discusses revealing the constraints of tectonic uplifts on geomorphology in the YRB. The uplifts of the Tibetan Plateau and neotectonic activities in the upper reach of the YR have not only significantly influenced river formations and geomorphological evolution but are also closely related to geological disasters in the basin (Peng et al., 2004;Xu et al., 2017). The northeastern Tibetan Plateau is characterized by strong tectonic deformations, densely distributed active faults, and frequent earthquakes (Wang, 2002;Zhang P Z et al., 2013;Lan et al., 2016). ...
The Yellow River Basin (YRB) is characterized by active geological and tectonic processes, rapid geomorphological evolution, and distinct climatic diversity. Correspondingly, major disasters in the YRB are characterized by varied types, extensive distributions, and sudden occurrences. In addition, major disasters in the YRB usually evolve into disaster chains that cause severe consequences. Therefore, major disasters in the YRB destroy ecologies and environments and influence geological and ecological safety in the basin. This paper systematically reviews research on geological and surface processes, major disaster effects, and risk mitigation in the YRB, discusses the trends and challenges of relevant research, analyzes the key scientific problems that need to be solved, and suggests prospects for future research based on the earth system science concept. Themes of research that should be focused on include geological, surface and climatic processes in the YRB and their interlinking disaster gestation mechanisms; formation mechanisms and disaster chain evolutions of giant landslides in the upper reach of the YRB; mechanisms and disaster chain effects of loess water-soil disasters in the middle reach of the YRB; occurrence patterns and amplifying effects of giant flood chains in the lower reach of the YRB; and risk mitigations of major disasters in the YRB. Key scientific problems that need to be solved are as follows: how to reveal the geological, surface and climatic processes that are coupled and interlinked with gestation mechanisms of major disasters; how to clarify the mutual feedback effects between major disasters and ecology; and how to develop a human-environmental harmony-based integrated risk mitigation system for major disasters. Prospects for future studies that follow the earth system science concept include the following: highlighting interdisciplinary research to reveal the interlinked disaster gestation mechanisms of the geology, surface and climate in the YRB in the past, present, and future; forming theories to clarify the regional patterns, dynamic mechanisms, and mutual-feedback effects between disaster chains and ecology in the YRB on land and in rivers in the region; solving technological bottlenecks to develop assessment models and mitigation theories for integrated risks in the YRB by following the human-environment harmony concept; and finally, establishing a demonstratable application pattern characterized by “whole-basin coverage” and “zonal controls”, thereby guaranteeing ecological and geological safety in the basin and providing scientific support for ecological conservation and high-quality development of the YRB.
... The upper reaches of the Yellow River, affected by the strong uplift of the Qinghai-Tibet Plateau, has become one of the regions where geological hazards are most severe in China . Many ancient large-scale and unstable landslides are distributed on both sides of the Yellow River, which pose a great threat to local residents . ...
Interferometric synthetic aperture radar (InSAR) technology has become one of the mainstream techniques for active landslide identification over a large area. However, the method for interpreting anomalous deformation areas derived from InSAR data is still mainly manual delineation through human–computer interaction. This study focuses on using a deep learning semantic segmentation model to identify the boundaries of anomalous deformation areas automatically. We experimented with the delineation results based on an InSAR deformation map, hot spot map, and different combinations of topographic datasets to build the optimal model. The result indicates that the hot spot map, aspect, and Google Earth image as input features based on the U-Net model can achieve the best performance, with the precision, recall, F1 score, and intersection over union (IoU) being 0.822, 0.835, 0.823, and 0.705, respectively. Our method promotes the development of identifying active landslides using InSAR technology automatically and rapidly at a regional scale. Moreover, applying a new method for automatically and rapidly identifying potential landslides in susceptible areas is necessary for landslide hazard mitigation and risk management.
... The Tibetan Plateau, as the third pole of the Earth, is a zone of rapid topographic change characterized by plate collision and active tectonics . The eastern part of the plateau, in particular, is marked by complex topography, active plate tectonics and extremely high seismic intensity. ...
The current deformation and stable state of slopes with historical shatter signs is a concern for engineering construction. Suspected landslide scarps were discovered at the rear edge of the slope of the Genie in the Sichuan-Tibet transportation corridor during a field investigation. In order to qualitatively determine the current status of the surface deformation of this slope, this paper uses high-resolution optical remote sensing, airborne LiDAR and InSAR technologies for comprehensive analysis. The interpretation of high-resolution optical and airborne LiDAR data revealed that the rear edge of the slope exhibits three levels of scarps. However, no deformation was detected with the D-InSAR analysis of ALOS-1 radar images from 2007 to 2008 or with the Stacking-InSAR and SBAS-InSAR processing of Sentinel-1A radar images from 2017 to 2020. A geological model of the slope was established in combination with field investigation stipulating that the slope is composed of steep anti-dip layered dolomite limestone and that the scarps at the rear edge of the slope were caused by historical shallow toppling. Further research is recommended to determine the extent of toppling deformation and evaluate the slope stability under the disturbance of tunnel excavation.
... Debris flows are one of the geomorphic agents carrying large amounts of solid material. Because of sudden initiation and complicated formation processes, debris flows have strong destructive power to cause casualties (Peng et al., 2004;Zhang et al., 2016). The Linxia Basin in Gansu Province China is located at the transitional region between the Tibetan Plateau and the Loess Plateau, where debris flows are highly developed (Li and Zeng 1982). ...
The Linxia Basin is located in the transition zone between the Qinghai–Tibet Plateau and the Loess Plateau in China. Collapse–landslide–debris flow geological disasters are particularly prevalent in this region. Taking a debris flow that occurred in Zhangjiayuan gully, Dongxiang County, as an example, the characteristics and formation mechanism were studied through field investigation and remote sensing interpretation methods. The hazard zoning and influence range of the debris flow were analysed under different precipitation conditions using numerical simulations. The results show that the debris flow in Zhangjiayuan gully experienced medium-to small-scale, rapid and catastrophic viscous mud flows, with activity frequencies ranging from medium to low. Because large numbers of landslides, collapses and overland flows developed on the gully bank slope, material sources for debris flows were abundant but were supplied intermittently. Induced by heavy rainfall, the landslides on the bank slipped into the gully, and then the landslide mass blocked the channel and formed a weir dam. As water converged in the gully, the dam body softened to mud, seepage deformation occurred, and the dam then burst to form a debris flow. This disaster mode represents a kind of rainfall-type landslide–blockage–debris flow disaster chain. Under varying conditions in which heavy rainfall occurs once every 10 years or once every 50 years, debris flows may break out in Zhangjiayuan gully, and the Zheda highway and the associated tunnels located below the gully are in medium–high debris flow danger zones. When a debris flow rushes out of the gully mouth and cannot be discharged in time, it accumulates and buries the highway and tunnels. Therefore, attention should be given to preventing such small-scale sudden debris flow disasters and strengthening the early warning capacity of debris flow prevention to ensure the safe operation of highway.
... To date, the Yellow River Basin remains one of the most vulnerable watershed systems in the world (Hamblin & Christiansen, 2004). The uplift of the Qinghai-Tibet Plateau and neotectonic movements have not only had a serious impact on river formation and geomorphological evolution (Pan, Li, Cao, & Chen, 1996), but they are also closely linked to geological hazards in the river basin (Peng, Ma, Lu, Li, & Shao, 2004). The problem of the Yellow River is reflected from the river, formed in the region and rooted in the land. ...
The drainage basin of the upper reaches of the Yellow River from Lagan Gorge to
Liujia Gorge, which spans Gonghe, Guide, Jianzha, Xunhua and Linxia basins, is
located in the transition zone between the Qinghai–Tibet Plateau and the Loess Plateau,
northwestern China. Its evolution is controlled by the northeastward growth
and uplift of the Qinghai–Tibet Plateau. To characterize and quantify the response of
surface processes to deep geological mechanisms and to investigate the types of Late
Cenozoic tectonic deformation in the study area and the relationship with large geological
hazards, we analysed various geomorphological indicators, combined with field
observations and the estimated incision rates and established a reasonable tectonic
deformation model. The results demonstrate that the variations in the geomorphic
indices are highly consistent with active tectonics. Higher hypsometric integral (HI),
higher normalized stream length-gradient index (SLK), higher basin asymmetry factor
(AF), higher drainage basin shape (BS) and lower ratios of valley floor width to valley
height (VF) indicate higher tectonic uplift rate in the Jianzha-Xunhua basins compared
to other basins where there are many giant landslides. These giant landslides
occurring there can probably be correlated with the vigorous tectonic activity, thus
generating a great significance in geological hazard prevention and control along the
upper Yellow River.
... Landslides have presented considerable challenges to the engineering and construction of traffic arteries and water conservancy facilities as well as the social and economic development of towns and villages in mountain areas worldwide with increasingly affected ecological and geological environments (Guo et al., 2019;Chen and Li, 2020). Due to the complex geological conditions and strong tectonic activities along the eastern margin of the Qinghai-Tibet Plateau, the internal and external dynamic geological processes in this region are very active, leading to alpine valleys with steep terrain and abundant loose materials for landslides (Peng et al., 2004;Pan et al., 2012;Zou et al., 2017a;Yang et al., 2018). In particular, unstable slopes are prone to the occurrence of landslides triggered by rainfall or seismic activity, resulting in extensive casualties and economic losses (Crosta and Frattini, 2007;Zhang et al., 2013;Huang and Li, 2014;Chen et al., 2018). ...
Susceptibility assessments are crucial in identifying hazards in densely populated mountain areas featuring active internal and external dynamic geological processes. A comprehensive analysis of the interactions among ecological, hydrological, and geotechnical factors was performed to develop a quantitative method for assessing regional landslide susceptibility based on slope failure and landslide formation mechanisms. Using slope geomorphic units (SGUs) that can sufficiently describe the comprehensive features of landforms and hazard-forming factors related to landslides, an integrated model was built to analyze potential slip planes and slope stability by considering the different reinforcement effects of roots on soil, the root anchoring capacities of various vegetation types, and the corresponding vegetation weight loads. Using this SGU-based method, the occurrence possibility of regional-scale landslides was determined by analyzing the propagation directions and maximum moving distances of landslide materials in unstable areas. Taking the landslides in the Dadu River Basin, China, as a case study, a landslide susceptibility map was obtained and validated by conducting a field study and remote sensing interpretation of actual landslides; the assessment results were in accordance with the actual disaster situation. The distributions of zones with high or very high susceptibility (i.e., high-altitude valleys with steep slopes, abundant rainfall, and severe soil erosion) are closely correlated with the slope topography and stability. These findings suggest that the proposed assessment methodology can provide scientific support for preventing or mitigating landslide hazards and may serve as pertinent guidance for regional landslide susceptibility assessments in the Dadu River Basin and beyond.
... Due to the strong uplift in history, tectonic movement of Qinghai-Tibet Plateau is forceful. Added with the action of bad climatic conditions, various geological hazards including slope collapse, landslide, debris flow, etc., are all frequent and large-scale, making Qinghai-Tibet Plateau become one of the regions with serious geological disasters in China (Peng et al., 2004). Superimposed statistical data of disaster cases and corresponding epoch strata indicate that most geological disasters in Qinghai-Tibet Plateau take place in the Quaternary Strata (Jiang et al., 2005). ...
Most landslides in Qinghai-Tibet Plateau take place in the Quaternary strata. Reasonable deformation mechanism, analyses method and controlling measures are proposed to treat colluvial landslides in this paper. Combined with the regional geological conditions of a colluvial landslide located at Road S101 Line of Qinghai Province, distinctive influencing factors were analyzed, including adverse physical and mechanical properties, geometrical structure, coupled fluid and thermal process. Slope stability was simulated by finite difference method. Displacement and shear strain in the lower part of sliding body are both higher than the upper part in saturated condition, consistent with the actual sliding characteristics. According to the geological comprehensive analyses and numerical simulation, the deformation mechanism, temporal and spatial evolutionary processes were summarized. The results show that freeze-thaw cyclic process of stagnant water during winter and spring make shallow deposits creep continuously and slide ultimately. Saturated condition caused by rainstorm in summer or autumn makes the slope slide integrally, and draws the mudstone at back to slide subsequently. The suitability and practical feedback of various kinds of controlling measures applied to colluvial landslides in cold regions were discussed. Micropile has significant elastic flexibility and unloading ability, and so can adapt to the mechanical change and sliding process of slope during freeze-thaw process. Both practical application and numerical calculation indicate that micropile is an appropriate choice against colluvial landslides in Qinghai-Tibet Plateau.
Mapping potential landslides is crucial to mitigating and preventing landslide disasters and understanding mountain landscape evolution. However, the existing methods to map and demonstrate potential landslides in mountainous regions are challenging to use and inefficient. Therefore, herein, we propose a method using hot spot analysis and convolutional neural networks to map potential landslides in mountainous areas at a regional scale based on ground deformation detection using multitemporal interferometry synthetic aperture radar. Ground deformations were detected by processing 76 images acquired from the descending and ascending orbits of the Sentinel-1A satellite. In total, 606 slopes with large ground deformations were automatically detected using hot spot analysis in the study area, and the extraction accuracy rate and the missing rate are 71.02% and 7.89%, respectively. Subsequently, based on the high-deformation areas and potential landslide conditioning factors, we compared the performance of convolutional neural networks with the random forest algorithm and constructed a classification model with the area under the curve (AUC), accuracy, recall, and precision for testing being 0.75, 0.75, 0.82, and 0.75, respectively. Our approach underpins the ability of interferometric synthetic aperture radar (InSAR) to map potential landslides regionally and provide a scientific foundation for landslide risk management. It also enables an accurate and efficient identification of potential landslides within a short period and under extremely hazardous conditions.
A large proportion (~80%) of the Indian subcontinent’s precipitation comes from the Indian summer monsoon (ISM), which influences one-fifth of the world’s population. A long-term reliable proxy for ISM is fundamental to understanding previous global climate change. We establish a mass-wasting-inferred proxy to examine the paleohydrogeology (river undercutting history) of the Southeast Tibetan Plateau and reconstruct the variability of ISM intensity (precipitation) in the past 130,000 years. Our data suggest that mass-wasting events, which provides us sufficient samples for paleoclimate research, are prone to dramatic climate changes, especially extreme climate environments. The Southeast Tibetan Plateau was subjected to at least four distinct ISM intensity phases in the past 130,000 years. We conclude that ISM intensity has a cyclicity featured by the Earth’s orbit with obliquity, and that ISM intensity transformation lags the global ice volume (sea level) change by 8–15 kyrs.
Numerous damming landslides have occurred at the southeastern margin of the Tibetan Plateau due to intense tectonic activities, strong river erosion, and extreme climate change. A Late Pleistocene paleo-landslide damming event has been detected in the Induba area in the upstream reaches of the Jinsha River, preserving various river-blocking phenomena, such as landslide dammed deposits and fluvial and paleo-dammed lacustrine sediments. Based on remote sensing and field investigations, we determined that the damming landslide originated from the inclined counter rock mass and experienced intense fragmentation, forming rock avalanches, which were possibly triggered by paleo-earthquakes or a combination of paleo-earthquakes and rainfall. To better understand the evolution of dam breaching and river valley landforms, optically stimulated luminescence (OSL) dating of lacustrine sediments was attempted. The results show that the landslide damming occurred ∼79.30 ka ago and formed a dammed lake upstream, which existed at least ∼20.86 ka before the dam breaching. The horizontal fluvial layers adhered to relict landslide deposits on the left bank, indicating that the process of dam breaching was conducted under the multiple circulations of lake water overtopping, fluvial deposition, and river undercutting. This study enriches our understanding of the formation of old dammed landslides and the evolution of river valley landforms in this region.
Affected by Qinghai-Tibet Plateau tectonic structures, numerous accumulations slides which have the characteristics of multiple formation types, complex mechanism, sudden occurrence, difficult to predict the developing trend, huge damage, etc., are distributed in Southwest China. Among of them, Jiaju landslide, which locates at the upper reach of Dadu River, is a typical ancient one with dramatically thick depth and localized resurrection tendency. A comprehensive monitoring system including GPS, InSAR and Inclinometer has been carried out to monitor both surface displacement and deep displacement. The result shows that Jiaju landslide nowadays is at an evolutionary stage with accelerating deformation in the surface and slow deformation in the deep body. And further analysis of the monitoring results indicates the deformation and failure modes are the combination of sliding and compression cracking in the surface and fracturing in the deep position. In order to testify the monitoring results, FLAC3D numerical simulation method is adopted and the stress field, distribution of displacement and plastic zone in the dynamic deformation process for Jiaju landslide are all simulated; and simulation results are consistent with monitoring results.
The continuous and periodic uplift of the Qinghai-Tibet Plateau since the Cenozoic is an important geological and environmental event during the evolution of the Earth. Especially the accelerated uplift of the plateau since the Late Cenozoic has made the Qinghai-Tibet Plateau and its peripheral areas become the highest step of continental China. The paper focuses on the uplift mechanism of the plateau through a detailed study of the composition and geometric and kinematic features of the Yulong-Haba block-a typical Quaternary rapidly and differentially uplifted area on the southeastern margin of the Qinghai-Tibet Plateau, and on that basis, the paper further studies the effect of the rapid uplift on geological hazárds (e.g. earthquakes, avalanches, landslides and mudflows) and its controls on the occurrence and development of geological hazards. In the last, it is concluded that there exits a coupling relationship between the Earth's endogenic geological processes (rapid differential block uplift) and the exogenic geological processes (major geological hazards).
Based on the field survey data and exploration results, this paper comprehensively e-laborated the landslide distribution, structure, type, size and the history of deformation. In addition, factors that may lead to or influence the control of landslide were also thoroughly analyzed, which include the topography, geological structure and earthquake, stratum lithology, precipitation, hydrological geological conditions and human economic activities. According to the slope of typical geological section, transfer coefficient method was applied to calculate and analyze the landslide stability. The result shows that landslide is in a less stable or unstable state under the current situation, while rainfall and earthquake conditions will make the landslide unstable. Finally, landslide project management ideas and solutions were proposed, with a view to be used for the landslide government in similar regions.
In order to explore the relationship between the geological settings and the development of the slides, and mechanisms of landslides induced by evolution of the Yellow River terrace in Lanzhou, the development phase characters of the Yellow River valley evolution in Lanzhou, control effect of the valley evolution to landslides and landslide formation model are studied in this paper based on extensive analysis of regional engineering geology data, combined with Quaternary geomorphology and engineering geology. It is found that: (1) the control effect of landslides in Lanzhou induced by the Yellow River valley evolution shows phase in time and zonation in space. The landslides have different development modes and formation mechanisms in different phases of river valley evolution. (2) The major inducing factors of terrace landslides are intense neotectonics uplifting, strong incision of the Yellow River and relative moisture paleoclimate during the terraces formed. The weak intercalated layers formed in Tertiary mudstone stratum may induce large scale loess-mudstone landslides while it may develop small-middle scale landslides and collapses in the loess layer. The landslides may lead to the deficiency of partial terraces during the river valley evolution.
According to the distribution and movement of Xi'an ground fissure, combining the trend of metro tunnel No.2 in Xi'an, a geological model has been built, and then the effects of the ground fissure on the metro tunnel have been studied. The experimental results show that the tunnel is in tension and compression states, and behaviors as a cantilever elastic foundation beam under the environment of ground fissure. The tensile parts mainly distribute in the range between 20 and 80 cm away from the fissure in fixed block, and the compressive parts distribute between 20 cm away from the fissure in declined block and 80 cm away from the fissure in fixed block. At the same time, the movement of the ground fissure greatly increases the vertical pressure of surrounding rock at the top of tunnel and reduces the vertical pressure of surrounding rock under the bottom of tunnel in the decline block. Under the environment of ground fissure, the failure mode is mainly circumferential crack; the secondary fissures are controlled by tension-shear areas, and step and y-shaped fissures are mainly induced. Based on the experimental results, the section and position where countermeasures should be taken are put forward when the metro tunnels cross the ground fissure region.
The 21st century shall be a century of accelerated development of tunnel construction in China. But until now, what have been
frequently stated in reports about influence of tunnels on environment are basically negative. In fact, this is not true.
Tunnels, especially those extend across sensitive areas do exert some positive functions on improving environment and preventing
local slope hazards. These positive effects, being new phenomena, are found and put forward by the authors after a series
of careful observations have been carried out and in-depth analysis performed the first time. Meanwhile, it is a positive
evaluation that the authors made upon tunnels. Many important phenomena and data are cited as evidence and their causative
factors are analyzed in this paper as well.