Most Cited Articles

(The cited data comes from the whole network and is updated monthly.)
1
A magnitude 7.0 earthquake struck Jiuzhaigou on August 8th, 2017 in Sichuan province, which is another strong earthquake happened in Sichuan province after the 2008 great Wenchuan earthquake and the 2013 Lushan earthquake. In order to provide scientific evidence for on-the-spot rescue work and geologic hazard prevention after the earthquake, the author arrived quickly on the field and finished geologic hazard interpretation and review work in the earth-stricken areas based on high resolution remote sensing images before and after the earthquake. As a result, 1833 earthquake-induced geohazards have been obtained in the study area of 840km2, which are mainly medium-scale and small-scale shallow landslides and collapses. In terms of the results of the interpretation, the spatial distribution patterns and control factors in the cosesmic geohazards (distance from the fault, PGA, elevation, slope, aspect etc.) are analyzed, the research shows that the geohazards triggered by earthquake have the features of zonal distribution mainly distributed along north-west and east-south, especially along the roads and valleys. The width of strong development zone along the field inferred seismogenic fault is about 2km, showing a distinct faulting effect, but the spatial correlation betweem geohazards and Tazang fault is weak. Based on the above-described analysis, logistic regression model is taken quick comments and divisions of geologic hazard susceptibility are made. After statists and testing, the accuracy of this model has reached 0.851, a comparatively high precise data. A magnitude 7.0 earthquake struck Jiuzhaigou on August 8th, 2017 in Sichuan province, which is another strong earthquake happened in Sichuan province after the 2008 great Wenchuan earthquake and the 2013 Lushan earthquake. In order to provide scientific evidence for on-the-spot rescue work and geologic hazard prevention after the earthquake, the author arrived quickly on the field and finished geologic hazard interpretation and review work in the earth-stricken areas based on high resolution remote sensing images before and after the earthquake. As a result, 1833 earthquake-induced geohazards have been obtained in the study area of 840km2, which are mainly medium-scale and small-scale shallow landslides and collapses. In terms of the results of the interpretation, the spatial distribution patterns and control factors in the cosesmic geohazards (distance from the fault, PGA, elevation, slope, aspect etc.) are analyzed, the research shows that the geohazards triggered by earthquake have the features of zonal distribution mainly distributed along north-west and east-south, especially along the roads and valleys. The width of strong development zone along the field inferred seismogenic fault is about 2km, showing a distinct faulting effect, but the spatial correlation betweem geohazards and Tazang fault is weak. Based on the above-described analysis, logistic regression model is taken quick comments and divisions of geologic hazard susceptibility are made. After statists and testing, the accuracy of this model has reached 0.851, a comparatively high precise data.
2
An increase in the number of rock slope instability case that was characterized with "toppling" movement was found in the practice of engineering geology in west China in the past decade. The significance of the potential threats caused by toppling failure has arguably moved abreast of that induced by the conventional slope movement type commonly known as "sliding", and thus it has become a more pronounced challenge faced by engineering geologists and geotechnical engineers. The critical issue in the study of toppling failure is that the current analytical and/or empirical models are primarily based on the hypothetical slide of rock slopes without considering other forms of movement. The paper analyzes the deformation and failure process of toppling movement in light of the field data obtained from a large number of engineering projects. The study of toppling movement presented here constructed engineering geology models to depict the deformation at various stages and divided the movement into the types of toppling-falling, toppling-slipping, toppling-cracking, and toppling-loosening, which provides systematic qualitative descriptions and quantitative thresholds for the characteristics of each movement type. The study aims at unifying the understanding of geological significance, static and dynamic mechanics, and slope stability analysis to provide means of evaluating the stability of rock slopes prone to toppling failure. The slope stability evaluating criteria are primarily based on deformation process compare to the previous criteria utilizing strength to assess the stability of slope subject to sliding movement. An increase in the number of rock slope instability case that was characterized with "toppling" movement was found in the practice of engineering geology in west China in the past decade. The significance of the potential threats caused by toppling failure has arguably moved abreast of that induced by the conventional slope movement type commonly known as "sliding", and thus it has become a more pronounced challenge faced by engineering geologists and geotechnical engineers. The critical issue in the study of toppling failure is that the current analytical and/or empirical models are primarily based on the hypothetical slide of rock slopes without considering other forms of movement. The paper analyzes the deformation and failure process of toppling movement in light of the field data obtained from a large number of engineering projects. The study of toppling movement presented here constructed engineering geology models to depict the deformation at various stages and divided the movement into the types of toppling-falling, toppling-slipping, toppling-cracking, and toppling-loosening, which provides systematic qualitative descriptions and quantitative thresholds for the characteristics of each movement type. The study aims at unifying the understanding of geological significance, static and dynamic mechanics, and slope stability analysis to provide means of evaluating the stability of rock slopes prone to toppling failure. The slope stability evaluating criteria are primarily based on deformation process compare to the previous criteria utilizing strength to assess the stability of slope subject to sliding movement.
3
Heifangtai is located in Yongjing County, Gansu province. The loess landslide is very developed due to irrigation. One of the most typical landslides is the gradual retreat of the loess landslide caused by long-term irrigation. This paper compares the Google images and the field survey of representative landslide occurred in recent years. It shows that the loess landslides have the characteristics of gradual recession. It further investigates and analyze the water content of the loess landslide profile. It finds that the main reason for loess landslide occurred continuously are soft base effect formed by long-term soaking of groundwater. The arc groove of the landslide often becomes the concentration of groundwater and drainage points. The residual landslide accumulation in slide source area rises the local underground water. It is the main reason to make the same position more and more gradual retreat type landslide. Heifangtai is located in Yongjing County, Gansu province. The loess landslide is very developed due to irrigation. One of the most typical landslides is the gradual retreat of the loess landslide caused by long-term irrigation. This paper compares the Google images and the field survey of representative landslide occurred in recent years. It shows that the loess landslides have the characteristics of gradual recession. It further investigates and analyze the water content of the loess landslide profile. It finds that the main reason for loess landslide occurred continuously are soft base effect formed by long-term soaking of groundwater. The arc groove of the landslide often becomes the concentration of groundwater and drainage points. The residual landslide accumulation in slide source area rises the local underground water. It is the main reason to make the same position more and more gradual retreat type landslide.
4
The large and professional unmanned aerial vehicle based remote sensing (UAVRS) system has been widely used for the emergency survey of the wide range of geo-hazards. In this paper, the more simple and flexible micro-UAVRS method for the emergency survey of individual geo-hazard is put forward, based on a number of successful practices of emergency survey for geo-hazards in the Three Gorges Reservoir in recent years. The method includes: assembling a multi-rotor micro-UAVRS system that is more applicable for the emergency survey of the individual geo-hazard; developing the specific implementation process; and elaborating some crucial technologies and methods such as the arrangement and measurement of ground control points, the design of flight plan according to the features of geo-hazard, the control of the micro-UAVRS' flight and photos acquisition, and the image processing, etc. Practice shows that, using the micro-UAVRS method for the emergency survey of individual geo-hazard is useful, and capable of achieving the goal of fast & efficient, because the method can not only greatly reduce the work time, strength and risks, but also provide the high-precision remote sensing results and data. The large and professional unmanned aerial vehicle based remote sensing (UAVRS) system has been widely used for the emergency survey of the wide range of geo-hazards. In this paper, the more simple and flexible micro-UAVRS method for the emergency survey of individual geo-hazard is put forward, based on a number of successful practices of emergency survey for geo-hazards in the Three Gorges Reservoir in recent years. The method includes: assembling a multi-rotor micro-UAVRS system that is more applicable for the emergency survey of the individual geo-hazard; developing the specific implementation process; and elaborating some crucial technologies and methods such as the arrangement and measurement of ground control points, the design of flight plan according to the features of geo-hazard, the control of the micro-UAVRS' flight and photos acquisition, and the image processing, etc. Practice shows that, using the micro-UAVRS method for the emergency survey of individual geo-hazard is useful, and capable of achieving the goal of fast & efficient, because the method can not only greatly reduce the work time, strength and risks, but also provide the high-precision remote sensing results and data.
5
The seismic fault and source rupture tectonic dynamics mechanism of Jiuzhaigou MS7.0 Earthquake were studied in this paper based on the combination of geological investigation, test and source tectonic dynamic theoretical analysis. This earthquake occurred at the intersection of the northern margin of the Minshan uplift belt and the south of Wenxian-Maqin fault in the south margin of the West Qinling trough, where is under sinistral shear stress with high law stress. There are two tectonic ruptures with NW trending fissure zone along the line of "Jiuzhaigou Paradise"-epicenter-Wuhuahai and Shangsizhai Village-Zhongcha-Bimang, which is ground coseismic rupture caused by "hidden" earthquake fault, former is the structure controlling this earthquake, the later is the sub-coseismic resurrection and extension of the NW-trending fault; the displacement of source fault in this earthquake is strike-slip shear fracture dominated by deep angle fault with strike NW331ånd dip angle ∠87°, and the aftershock activity is controlled by two NW-trending faults, the shear fracture at both ends of the fault showed continuous expansion trends. The source tectonic dynamic mechanism is actually sinistral cutting "protrusion" along NW in the deep of crust. The continuous expansion of rupture at both ends of seismic fault will produce the gradual breakthrough of the crustal "protrusion". The seismic fault and source rupture tectonic dynamics mechanism of Jiuzhaigou MS7.0 Earthquake were studied in this paper based on the combination of geological investigation, test and source tectonic dynamic theoretical analysis. This earthquake occurred at the intersection of the northern margin of the Minshan uplift belt and the south of Wenxian-Maqin fault in the south margin of the West Qinling trough, where is under sinistral shear stress with high law stress. There are two tectonic ruptures with NW trending fissure zone along the line of "Jiuzhaigou Paradise"-epicenter-Wuhuahai and Shangsizhai Village-Zhongcha-Bimang, which is ground coseismic rupture caused by "hidden" earthquake fault, former is the structure controlling this earthquake, the later is the sub-coseismic resurrection and extension of the NW-trending fault; the displacement of source fault in this earthquake is strike-slip shear fracture dominated by deep angle fault with strike NW331ånd dip angle ∠87°, and the aftershock activity is controlled by two NW-trending faults, the shear fracture at both ends of the fault showed continuous expansion trends. The source tectonic dynamic mechanism is actually sinistral cutting "protrusion" along NW in the deep of crust. The continuous expansion of rupture at both ends of seismic fault will produce the gradual breakthrough of the crustal "protrusion".
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In this paper, two concepts are proposed—namely, the ground sensing system and the ground sensing engineering. First, the basic composition, sensing requirements and related techniques of the ground sensing system is discussed based on the characteristics of geological media and geological materials. Then, the distributed fiber optic sensing technique is highlighted and introduced, and its technical system, sensing principles, and advantages and disadvantages are summarized. Finally, the meaning of the ground sensing engineering is elaborated, followed by corresponding installation techniques, and some issues to be addressed in this field. The implications of this paper may be of great importance for structuring of ground sensing system, geoengineering monitoring, and prevention and treatment of a variety of geological hazards. In this paper, two concepts are proposed—namely, the ground sensing system and the ground sensing engineering. First, the basic composition, sensing requirements and related techniques of the ground sensing system is discussed based on the characteristics of geological media and geological materials. Then, the distributed fiber optic sensing technique is highlighted and introduced, and its technical system, sensing principles, and advantages and disadvantages are summarized. Finally, the meaning of the ground sensing engineering is elaborated, followed by corresponding installation techniques, and some issues to be addressed in this field. The implications of this paper may be of great importance for structuring of ground sensing system, geoengineering monitoring, and prevention and treatment of a variety of geological hazards.
7
The loess is loose, and contains numerous large pores and vertical joints inside, which provides channels for the rapid infiltration of rainfall. The shallow loess landslides have caused significant casualties and economic losses. In order to effectively reduce the social and economic impact of landslides induced by rainfall, it is of great realistic significance to carry out the laboratory experimental study on rainfall-induced landslides. The purpose of this paper is to study the effects of different rainfall pattern and different slope structure on the deformation and failure process of loess slope. Three groups of indoor physical model experiments are designed and conducted. They include loess slope with continuous heavy rainfall, loess slope containing a vertical joint with continuous heavy rainfall, and loess slope with intermittent heavy rainfall. Three kinds of sensors including volume moisture sensors, matric suction sensors and pore water pressure sensors are buried to record the internal changes in each loess slope. Analyzing the changing readings of sensors and experimental phenomenon, and comparing the experimental procedures and results under the different experimental conditions disclose the deformation and failure law of shallow loess landslide under rainfall condition. The failure mode and triggering mechanism of this kind of landslides are summarized. The experimental results show that, in the early stage of the experiments, the matric suction of the loess decreased gradually and maintained stable in the end, therefore the strength reduced, with the continuous increases of volume moisture. In the later stage, the upper loess of the slope reached the saturation stage, excess pore water pressure generated by the slope deformation and poor drainage of the loess decreased the effective stress and the strength of the loess, and as a result, the strength reached the minimum, which resulted in landslides. And meanwhile, the influence of slope structure on slope stability is greater than that of rainfall pattern. The loess is loose, and contains numerous large pores and vertical joints inside, which provides channels for the rapid infiltration of rainfall. The shallow loess landslides have caused significant casualties and economic losses. In order to effectively reduce the social and economic impact of landslides induced by rainfall, it is of great realistic significance to carry out the laboratory experimental study on rainfall-induced landslides. The purpose of this paper is to study the effects of different rainfall pattern and different slope structure on the deformation and failure process of loess slope. Three groups of indoor physical model experiments are designed and conducted. They include loess slope with continuous heavy rainfall, loess slope containing a vertical joint with continuous heavy rainfall, and loess slope with intermittent heavy rainfall. Three kinds of sensors including volume moisture sensors, matric suction sensors and pore water pressure sensors are buried to record the internal changes in each loess slope. Analyzing the changing readings of sensors and experimental phenomenon, and comparing the experimental procedures and results under the different experimental conditions disclose the deformation and failure law of shallow loess landslide under rainfall condition. The failure mode and triggering mechanism of this kind of landslides are summarized. The experimental results show that, in the early stage of the experiments, the matric suction of the loess decreased gradually and maintained stable in the end, therefore the strength reduced, with the continuous increases of volume moisture. In the later stage, the upper loess of the slope reached the saturation stage, excess pore water pressure generated by the slope deformation and poor drainage of the loess decreased the effective stress and the strength of the loess, and as a result, the strength reached the minimum, which resulted in landslides. And meanwhile, the influence of slope structure on slope stability is greater than that of rainfall pattern.
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Simulations of landslide run-out can avoid the limit of experiment and instrumentation. It can observe the movement processes in detail. It is essential to the quantitative hazard assessment for landslide. for the simulation of landslide movement, the primary work is to establish a landslide model. Although the Particle Flow Code (PFC) is one of the most widely used program for landslide modeling, it is weak in the pre-processing of building the landslide model. This limits its application to landslide modeling. As for this, this paper illustrates the applicability, advantages and disadvantages of the Ball-Ball and Ball-Wall methods for model building. The way to determine the boundary of sliding mass and sliding bed is presented. It is based on the digital elevation map and the Brick filling method. It takes the earthquake-induced Red Rock Landslide as an example. Four steps are presented to build 2D & 3D landslide model with PFC.The four steps are obtaining topographic data, determining the boundary of both sliding mass and sliding bed, building the geometry of both sliding mass and sliding bed, filling the geometry with particles. By this way, the 2D and 3D landslide model can be easily and quickly built with PFC.The presented method will be helpful to the simulation of landslide movement with PFC. Simulations of landslide run-out can avoid the limit of experiment and instrumentation. It can observe the movement processes in detail. It is essential to the quantitative hazard assessment for landslide. for the simulation of landslide movement, the primary work is to establish a landslide model. Although the Particle Flow Code (PFC) is one of the most widely used program for landslide modeling, it is weak in the pre-processing of building the landslide model. This limits its application to landslide modeling. As for this, this paper illustrates the applicability, advantages and disadvantages of the Ball-Ball and Ball-Wall methods for model building. The way to determine the boundary of sliding mass and sliding bed is presented. It is based on the digital elevation map and the Brick filling method. It takes the earthquake-induced Red Rock Landslide as an example. Four steps are presented to build 2D & 3D landslide model with PFC.The four steps are obtaining topographic data, determining the boundary of both sliding mass and sliding bed, building the geometry of both sliding mass and sliding bed, filling the geometry with particles. By this way, the 2D and 3D landslide model can be easily and quickly built with PFC.The presented method will be helpful to the simulation of landslide movement with PFC.
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In the platform of FLAC3D software, how to build the three-dimensional models of complex geological bodies is always a difficulty encountered by many numerical simulation operators. On the other hand, the three-dimensional laser scanning technique presents a unique advantage in obtaining the fine spatial data of complex objects. Therefore, by the aid of reverse engineering, a new modeling method of complex geological bodies in FLAC3D platform is proposed. The accurate spatial and geometric information of complex geological bodies is firstly obtained by employing three-dimensional laser scanning technique. The point cloud data describing surface characteristics of complex geological bodies is processed and its surface model is then reconstructed in CAD format. Using the formidable geometry cleanup and mesh generation function of Hypermesh software, the surface model is transformed into three-dimensional finite element model. The node and element information can be translated into the format which can be received by FLAC3D. According to the above processes, the model data for FLAC3D is generated and the refined model of complex geological bodies is created in the pre-processing of FLAC3D.the feasibility and practicability of this approach is verified by combining practical project. In the platform of FLAC3D software, how to build the three-dimensional models of complex geological bodies is always a difficulty encountered by many numerical simulation operators. On the other hand, the three-dimensional laser scanning technique presents a unique advantage in obtaining the fine spatial data of complex objects. Therefore, by the aid of reverse engineering, a new modeling method of complex geological bodies in FLAC3D platform is proposed. The accurate spatial and geometric information of complex geological bodies is firstly obtained by employing three-dimensional laser scanning technique. The point cloud data describing surface characteristics of complex geological bodies is processed and its surface model is then reconstructed in CAD format. Using the formidable geometry cleanup and mesh generation function of Hypermesh software, the surface model is transformed into three-dimensional finite element model. The node and element information can be translated into the format which can be received by FLAC3D. According to the above processes, the model data for FLAC3D is generated and the refined model of complex geological bodies is created in the pre-processing of FLAC3D.the feasibility and practicability of this approach is verified by combining practical project.
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Due to the collapsibility, porous and water sensitivity of loess, geological disasters are widely distributed in loess area in northwest of China and show the characteristic of disaster chains. In this paper, several typical geological disasters in loess area are analyzed and the developmental states of geological disasters are concluded. Furthermore, the structures of two typical disaster chains are well described. In the geological disaster chains, the scale amplification is obvious, which is elaborated according to the 7.23 debris flow in Dagou gully in Tianshui City, Gansu Province. According to current research progress in geological disasters, three key issues are concluded and then the research ideas are given respectively. The research on risk assessment and chain scission about disaster chains should pay more attention to the future research. All and all, the preliminary research on geological disaster chains would be provide scientific reference to the future study. Due to the collapsibility, porous and water sensitivity of loess, geological disasters are widely distributed in loess area in northwest of China and show the characteristic of disaster chains. In this paper, several typical geological disasters in loess area are analyzed and the developmental states of geological disasters are concluded. Furthermore, the structures of two typical disaster chains are well described. In the geological disaster chains, the scale amplification is obvious, which is elaborated according to the 7.23 debris flow in Dagou gully in Tianshui City, Gansu Province. According to current research progress in geological disasters, three key issues are concluded and then the research ideas are given respectively. The research on risk assessment and chain scission about disaster chains should pay more attention to the future research. All and all, the preliminary research on geological disaster chains would be provide scientific reference to the future study.
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Much of relevant materials of 463 old landslides which had significant deformation in Three Gorges Reservoir Area are collected from June 2003 to June 2015. This paper studies the evolution models and slip-surface shapes of some typical old landslides. It concludes that there are 4 typical slip-surface shapes of circular, polyline, rectilinear and chair shape. Results of macroscopic analysis of wading extent and deformation time distribution can be summarized as follows. (1) The hydrodynamic pressure has obvious effect on the stability of the circular and rectilinear slip-surface landslides. Most of these two types of landslides deform at the lowering stage of water level when the front or middle is waded, especially after the first time to the highest water level. (2) A small part of the rectilinear slip-surface landslides is deformed at the stage of low water level after the drop because of lags in response. (3) The deformation occurs in the chair-shaped and polygonal line slip-surface landslides at the increasing stage of water level owing to effect of buoyancy weight loss, especially to the first 135m and 175m storage. Most of the chair-shaped slip-surface landslides are deformed when the front is waded as well as the rear wading extent of the polygonal line slip-surface landslides is higher than other 3 types. At last, the research results have a certain reference meaning for wading old landslides prevention in Three Gorges Reservoir Area. Much of relevant materials of 463 old landslides which had significant deformation in Three Gorges Reservoir Area are collected from June 2003 to June 2015. This paper studies the evolution models and slip-surface shapes of some typical old landslides. It concludes that there are 4 typical slip-surface shapes of circular, polyline, rectilinear and chair shape. Results of macroscopic analysis of wading extent and deformation time distribution can be summarized as follows. (1) The hydrodynamic pressure has obvious effect on the stability of the circular and rectilinear slip-surface landslides. Most of these two types of landslides deform at the lowering stage of water level when the front or middle is waded, especially after the first time to the highest water level. (2) A small part of the rectilinear slip-surface landslides is deformed at the stage of low water level after the drop because of lags in response. (3) The deformation occurs in the chair-shaped and polygonal line slip-surface landslides at the increasing stage of water level owing to effect of buoyancy weight loss, especially to the first 135m and 175m storage. Most of the chair-shaped slip-surface landslides are deformed when the front is waded as well as the rear wading extent of the polygonal line slip-surface landslides is higher than other 3 types. At last, the research results have a certain reference meaning for wading old landslides prevention in Three Gorges Reservoir Area.
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DEM numerical models based on PFC2D contact bond model are performed to probe the impact of stone content variation to shear properties of soil-rock mixture(S-RM).The micro parameters of unbound granular materials are calibrated with lab large-scale direct shear tests. Then the shear properties of S-RM of different stone content under different normal stress are studied. The result shows that for S-RM under the same normal stress, the high stone content would result in the high peak shear stress, the high shear strain at peak shear stress, the high post-softening strength, the stronger dilatation behavior, the more shear "leap" behavior. The friction angle of the S-RM increases and the cohesion decreases with the increase of the stone content. The cohesion keeps almost constant after stone content exceeds 50%. For S-RM with the same stone content, the high normal stress would have the high peak shear stress and the stronger strain-softening behavior. The shearing process of S-RM mainly overcomes the friction energy and strain energy are overcome whilst the change of the kinetic energy is almost zero. DEM numerical models based on PFC2D contact bond model are performed to probe the impact of stone content variation to shear properties of soil-rock mixture(S-RM).The micro parameters of unbound granular materials are calibrated with lab large-scale direct shear tests. Then the shear properties of S-RM of different stone content under different normal stress are studied. The result shows that for S-RM under the same normal stress, the high stone content would result in the high peak shear stress, the high shear strain at peak shear stress, the high post-softening strength, the stronger dilatation behavior, the more shear "leap" behavior. The friction angle of the S-RM increases and the cohesion decreases with the increase of the stone content. The cohesion keeps almost constant after stone content exceeds 50%. For S-RM with the same stone content, the high normal stress would have the high peak shear stress and the stronger strain-softening behavior. The shearing process of S-RM mainly overcomes the friction energy and strain energy are overcome whilst the change of the kinetic energy is almost zero.
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Chun'an county is located in southeast China, where is a typical region with extensive occurrence of rainfall-triggered landslides. Based on the results of detailed field investigation of geohazard in Chun'an county, this study applies GIS and Certainty Factor (CF) method to analyze the susceptibility of 9 landslide controlling factors. They include elevation, slope gradient, aspect, curvature, lithology, distance to fault, distance to roads, land use and vegetation. The results from CF analysis show that (1) stratigraphy of Cambrian, Sinian, Carboniferous and Cretaceous, and lithology of the intrusive rock group, red sandstone rock group, carbonatite mixed clasolite rock group, and carbonatite rock group are more susceptible to landslide. The affection of fault to landslide susceptibility in this study area decreases with the increasing of the distance to fault.(2) the areas relatively more susceptible to landslide occurrence include the areas with slope gradient between 10°~35°, aspects of south-facing in south and southeast direction, elevation between 100 and 200m, concave slope and straight slope, vegetation with non-forest, economic forest, tea and bamboo forest. The quantity of occurred landslides reaches to its peak in areas with slope gradient in a range from 30°and 35°.(3) the land use types with extensive anthropogenic activities such as residential land, cultivated land, transportation land and garden are prone to landslides. The controlling factor of distance to roads has less influence on landslide susceptibility and there is no significant correlation between them. This study will facilitate determination of categories with associated numerical intervals of each controlling factor, which is the fundamental in rainfall-triggered landslide susceptibility assessment and spatial prediction. Chun'an county is located in southeast China, where is a typical region with extensive occurrence of rainfall-triggered landslides. Based on the results of detailed field investigation of geohazard in Chun'an county, this study applies GIS and Certainty Factor (CF) method to analyze the susceptibility of 9 landslide controlling factors. They include elevation, slope gradient, aspect, curvature, lithology, distance to fault, distance to roads, land use and vegetation. The results from CF analysis show that (1) stratigraphy of Cambrian, Sinian, Carboniferous and Cretaceous, and lithology of the intrusive rock group, red sandstone rock group, carbonatite mixed clasolite rock group, and carbonatite rock group are more susceptible to landslide. The affection of fault to landslide susceptibility in this study area decreases with the increasing of the distance to fault.(2) the areas relatively more susceptible to landslide occurrence include the areas with slope gradient between 10°~35°, aspects of south-facing in south and southeast direction, elevation between 100 and 200m, concave slope and straight slope, vegetation with non-forest, economic forest, tea and bamboo forest. The quantity of occurred landslides reaches to its peak in areas with slope gradient in a range from 30°and 35°.(3) the land use types with extensive anthropogenic activities such as residential land, cultivated land, transportation land and garden are prone to landslides. The controlling factor of distance to roads has less influence on landslide susceptibility and there is no significant correlation between them. This study will facilitate determination of categories with associated numerical intervals of each controlling factor, which is the fundamental in rainfall-triggered landslide susceptibility assessment and spatial prediction.
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China is a country with many mountains. The risk assessment of rockfall has gained more attention due to the increase of rockfall hazard in mountainous areas. Rockfall risk analysis is inherently complex and difficult. Such difficulties are due to many factors. They include high uncertainties of rockfall occurrence and transport, lack of historical data, strongly site-specific nature of rockfall, difficulty in quantifying and modelling spatial rockfall distribution, quantifying the heterogeneity of vulnerability of different elements at risk and variability in temporal vulnerability, These factors lead many limitations in quantitative risk assessment. Rock falls in Luojiaqinggangling, Sichuan Province are a scarce example to study risk assessment quantitatively due to the complete field data and rich historical data. Based on the engineering geological investigation, topographical survey and statistic analysis, this paper confirms the provenance, accumulation area, maximum transport distance, annual probability of occurrence and four potentially unstable blocks A-D. Rockfall risk for exposed people in Luojiaqinggangling is estimated by the product of three conditional probabilities (annual probability of occurrence, reach probability and temporal-spatial probability) and vulnerability. Based on the rich statistical data of historical rockfall, the annual probability of occurrence is derived from a magnitude-cumulative frequency (MCF) distribution of rockfall events. Considering the size statistical characteristics of the historical rockfall and the position uncertainties of unstable blocks in provenance, this paper conducts the inversion analysis of slope restitution and friction coefficients. It uses the two-dimensional simulation software Rockfall. On these basis, the arrival probabilities of unstable blocks A-D were obtained after numerous random simulation and statistical analysis. Pedestrians and residents that are confirmed as the affected body based on field investigation, temporal-spatial probability depends on the mobility of the exposed elements. It is calculated using empirical equation according to the movement feature of affected body. The vulnerability was determined combining the kinetic energy of rockfall and the location of affected body. According to the product of occurrence probability, arrival probability, temporal distribution probability and vulnerability, the quantitative risk assessment of this rockfall is achieved. The results show that the risk values of block A and D are in a unacceptable risk range, and the risk values of blocks B and C are in a warning range. Those unstable blocks could threaten the life safety of the residents, therefore, it is essential to take appropriate measures for the disaster prevention and mitigation. China is a country with many mountains. The risk assessment of rockfall has gained more attention due to the increase of rockfall hazard in mountainous areas. Rockfall risk analysis is inherently complex and difficult. Such difficulties are due to many factors. They include high uncertainties of rockfall occurrence and transport, lack of historical data, strongly site-specific nature of rockfall, difficulty in quantifying and modelling spatial rockfall distribution, quantifying the heterogeneity of vulnerability of different elements at risk and variability in temporal vulnerability, These factors lead many limitations in quantitative risk assessment. Rock falls in Luojiaqinggangling, Sichuan Province are a scarce example to study risk assessment quantitatively due to the complete field data and rich historical data. Based on the engineering geological investigation, topographical survey and statistic analysis, this paper confirms the provenance, accumulation area, maximum transport distance, annual probability of occurrence and four potentially unstable blocks A-D. Rockfall risk for exposed people in Luojiaqinggangling is estimated by the product of three conditional probabilities (annual probability of occurrence, reach probability and temporal-spatial probability) and vulnerability. Based on the rich statistical data of historical rockfall, the annual probability of occurrence is derived from a magnitude-cumulative frequency (MCF) distribution of rockfall events. Considering the size statistical characteristics of the historical rockfall and the position uncertainties of unstable blocks in provenance, this paper conducts the inversion analysis of slope restitution and friction coefficients. It uses the two-dimensional simulation software Rockfall. On these basis, the arrival probabilities of unstable blocks A-D were obtained after numerous random simulation and statistical analysis. Pedestrians and residents that are confirmed as the affected body based on field investigation, temporal-spatial probability depends on the mobility of the exposed elements. It is calculated using empirical equation according to the movement feature of affected body. The vulnerability was determined combining the kinetic energy of rockfall and the location of affected body. According to the product of occurrence probability, arrival probability, temporal distribution probability and vulnerability, the quantitative risk assessment of this rockfall is achieved. The results show that the risk values of block A and D are in a unacceptable risk range, and the risk values of blocks B and C are in a warning range. Those unstable blocks could threaten the life safety of the residents, therefore, it is essential to take appropriate measures for the disaster prevention and mitigation.
15
The safety and durability of the soil slope can be threatened when the strength of soil is deteriorated due to wetting-drying cycles. Experimental studies are undertaken on an undisturbed residual soil from southeast of Fujian area. It aims to discuss the variation of shear strength with the change of water contain and the cyclic number under wetting-drying cycles. It is shown that the cohesion of granite residual soil decreases in different degrees with increasing number of cycles and finally reaches to a constant state. However, the friction angle of granite residual soil keeps a stable with little influence of the wetting-drying effects. On the basis of the relationship between the amount of strength attenuation and cyclic number, the S-shaped function is adopted for fitting. The results show that the S-shaped function can well describe the attenuation rules of cohesion with the change of cyclic number. The results also have an important reference value for further reveal the influence of wetting-drying cycles on deterioration mechanism of granitic residual soil and long-term stability of residual soil slope in southeast of Fujian. The safety and durability of the soil slope can be threatened when the strength of soil is deteriorated due to wetting-drying cycles. Experimental studies are undertaken on an undisturbed residual soil from southeast of Fujian area. It aims to discuss the variation of shear strength with the change of water contain and the cyclic number under wetting-drying cycles. It is shown that the cohesion of granite residual soil decreases in different degrees with increasing number of cycles and finally reaches to a constant state. However, the friction angle of granite residual soil keeps a stable with little influence of the wetting-drying effects. On the basis of the relationship between the amount of strength attenuation and cyclic number, the S-shaped function is adopted for fitting. The results show that the S-shaped function can well describe the attenuation rules of cohesion with the change of cyclic number. The results also have an important reference value for further reveal the influence of wetting-drying cycles on deterioration mechanism of granitic residual soil and long-term stability of residual soil slope in southeast of Fujian.
16
Prediction model for movement distance of rock avalanches has important theoretical significance and practical significance due to the characteristic of difficult detection, complex mechanism and high risk of gully-type rock avalanches. This study selects 38 typical rock avalanches induced by Wenchuan earthquake, and obtains their basic data based on the remote sensing and GIS technology combining with field investigation. Through correlation analysis, the results indicate that the influence factors of the maximum horizontal movement distance of rock avalanches (L) are landslide volume (V), the maximum vertical movement distance H, the elevation difference of slip source area (Hs), and the mean slope angle of the lower channel (β). Then a stepwise regression method is adapted to build optimal multiple regression model for the prediction of L. The validation shows that the multiple regression model is suitable for predicting rock avalanche hazardous zones in Wenchuan earthquake areas. The optimal multiple regression model and other internationally common-used prediction models are compared for the movement distance of landslides and debris flows. The result indicates that the forecast index system is suitable for the rock avalanches risk assessment in mountainous areas. The system considers the volume, drop height, the mean slope of the channel, with better goodness of fit index and physical meaning. Prediction model for movement distance of rock avalanches has important theoretical significance and practical significance due to the characteristic of difficult detection, complex mechanism and high risk of gully-type rock avalanches. This study selects 38 typical rock avalanches induced by Wenchuan earthquake, and obtains their basic data based on the remote sensing and GIS technology combining with field investigation. Through correlation analysis, the results indicate that the influence factors of the maximum horizontal movement distance of rock avalanches (L) are landslide volume (V), the maximum vertical movement distance H, the elevation difference of slip source area (Hs), and the mean slope angle of the lower channel (β). Then a stepwise regression method is adapted to build optimal multiple regression model for the prediction of L. The validation shows that the multiple regression model is suitable for predicting rock avalanche hazardous zones in Wenchuan earthquake areas. The optimal multiple regression model and other internationally common-used prediction models are compared for the movement distance of landslides and debris flows. The result indicates that the forecast index system is suitable for the rock avalanches risk assessment in mountainous areas. The system considers the volume, drop height, the mean slope of the channel, with better goodness of fit index and physical meaning.
17
From October 13 to 21, 2016, the 10th National Engineering Geological Conference is successfully held in Chengdu, Sichuan Province. In the opening ceremony, the author delivered a keynote presentation entitled "Engineering Geology: Review and Prospect of Past Ten Years". The author was the Chairman of the Eighth and Ninth Engineering Geology Committee. So this paper is his work review over past ten years. The author sums up with three phrases for the development of Engineering Geology in China over past ten years. They are a) Founding super engineering projects, b) Protecting people's well-being, c) Promoting the development of academic disciplines. Over the past ten years, Engineering Geology in China closely integrated with the national strategic demands and scientific and technical problems in engineering, provided the technical supports for the national super project construction, greatly reduced the death toll caused by the geological disasters through the theoretical innovation and the technological development, and made a large number of representative theoretical and technological results. The author also expresses his great expectation that China's Engineering Geology will reach the world's top level. From October 13 to 21, 2016, the 10th National Engineering Geological Conference is successfully held in Chengdu, Sichuan Province. In the opening ceremony, the author delivered a keynote presentation entitled "Engineering Geology: Review and Prospect of Past Ten Years". The author was the Chairman of the Eighth and Ninth Engineering Geology Committee. So this paper is his work review over past ten years. The author sums up with three phrases for the development of Engineering Geology in China over past ten years. They are a) Founding super engineering projects, b) Protecting people's well-being, c) Promoting the development of academic disciplines. Over the past ten years, Engineering Geology in China closely integrated with the national strategic demands and scientific and technical problems in engineering, provided the technical supports for the national super project construction, greatly reduced the death toll caused by the geological disasters through the theoretical innovation and the technological development, and made a large number of representative theoretical and technological results. The author also expresses his great expectation that China's Engineering Geology will reach the world's top level.
18
This paper is to further explore the mechanical effects of plants in slope protection in cold and arid environments. It selects five kinds of native herbs and shrubs as the test samples. They are suitable for the local climate conditions. They are planted in the self-built test area in this research. The single tensile tests are carried out to systematically analyze the strength characteristics of plant roots of the five kinds of herbs and shrubs. The results show the follows. The single root tensile resistances increases with the diameter increasing. Power relations exist between single root tensile resistances and root diameters of the herbs and shrubs respectively. Meanwhile, the single root tensile strengths increase with the diameter decreasing. Power relations exist between single root tensile strengths and root diameters of five kinds of herbs and shrubs respectively. The single root tensile strength of Elymus nutans Griseb is bigger than that of Agropyron trachycaulum(Linn.) Gaertn, while the sequence of the single tensile strengths of shrubs from big to small is Caragana korshinskii Kom,Zygophyllum xanthoxylon(Bunge) Maxim. and Nitraria tangutorum Bobr. Besides, some phenomena are shown by comparing and analyzing the stress-strain relationship curves of tensile tests of three kinds of shrubs in the vegetative period of 1a and 2a. That is,in the early single root tensile test of shrubs, there is a linear relationship between stress and strain, which shows the elastic material properties. Until the middle and late stage of the test, the relationship between stress and strain is nonlinear and shows the elastic-plastic material properties. Further research shows a downward trend of the largest elongation of the shrub single root with the increasing of vegetative period. The results of the study have a theoretical researching and practical guiding significance in the prevention and treatment of geological disasters such as shallow landslide and soil erosion in the study area and in the protection of the regional ecological geological environment. This paper is to further explore the mechanical effects of plants in slope protection in cold and arid environments. It selects five kinds of native herbs and shrubs as the test samples. They are suitable for the local climate conditions. They are planted in the self-built test area in this research. The single tensile tests are carried out to systematically analyze the strength characteristics of plant roots of the five kinds of herbs and shrubs. The results show the follows. The single root tensile resistances increases with the diameter increasing. Power relations exist between single root tensile resistances and root diameters of the herbs and shrubs respectively. Meanwhile, the single root tensile strengths increase with the diameter decreasing. Power relations exist between single root tensile strengths and root diameters of five kinds of herbs and shrubs respectively. The single root tensile strength of Elymus nutans Griseb is bigger than that of Agropyron trachycaulum(Linn.) Gaertn, while the sequence of the single tensile strengths of shrubs from big to small is Caragana korshinskii Kom,Zygophyllum xanthoxylon(Bunge) Maxim. and Nitraria tangutorum Bobr. Besides, some phenomena are shown by comparing and analyzing the stress-strain relationship curves of tensile tests of three kinds of shrubs in the vegetative period of 1a and 2a. That is,in the early single root tensile test of shrubs, there is a linear relationship between stress and strain, which shows the elastic material properties. Until the middle and late stage of the test, the relationship between stress and strain is nonlinear and shows the elastic-plastic material properties. Further research shows a downward trend of the largest elongation of the shrub single root with the increasing of vegetative period. The results of the study have a theoretical researching and practical guiding significance in the prevention and treatment of geological disasters such as shallow landslide and soil erosion in the study area and in the protection of the regional ecological geological environment.
19
Liquid CO2 phase transition characteristics and coal to gas phase CO2 and CH4adsorption regularity are researched. Experiment finds out that under different coal quality, temperature and equilibrium pressure, the adsorption ability of CO2 in coking coal and anthracite coal is as 1.8~2.4 times to that of CH4. The volume of CO2 phase transition expands to 794 times instantaneously within 0.2 s. Theoretical studies are carried out to establish a mathematical model for the non-coupling fracturing under the condition of blasting hole initial shock pressure peak, fissured circle effective radius and blasting induced cracking borehole three main blasting parameters. Blasting machine is used and has 200MPa outlet pressure when the liquid CO2 phase transition instantaneously. According to on-site experiment research of the coal seam, its permeability improvement leads to bursting. The control hole has 2m and 3m distance to the blasting hole. After blasting the one drilling gas extraction from scalar increases up to 6 times and 4 times, the one drilling gas extraction concentration up to 5 times and 4 times. The one drilling gas extraction concentration is in 35%~55%.The control hole has 4m distance from the blasting hole after five days, the gas extraction effect attenuates to the level before blasting. The field test shows that under the initial impact pressure peak value of 200MPa and the borehole diameter of 0.094m, the effective radius of the fracture zone of the coal seam is 3m. Liquid CO2 phase transition characteristics and coal to gas phase CO2 and CH4adsorption regularity are researched. Experiment finds out that under different coal quality, temperature and equilibrium pressure, the adsorption ability of CO2 in coking coal and anthracite coal is as 1.8~2.4 times to that of CH4. The volume of CO2 phase transition expands to 794 times instantaneously within 0.2 s. Theoretical studies are carried out to establish a mathematical model for the non-coupling fracturing under the condition of blasting hole initial shock pressure peak, fissured circle effective radius and blasting induced cracking borehole three main blasting parameters. Blasting machine is used and has 200MPa outlet pressure when the liquid CO2 phase transition instantaneously. According to on-site experiment research of the coal seam, its permeability improvement leads to bursting. The control hole has 2m and 3m distance to the blasting hole. After blasting the one drilling gas extraction from scalar increases up to 6 times and 4 times, the one drilling gas extraction concentration up to 5 times and 4 times. The one drilling gas extraction concentration is in 35%~55%.The control hole has 4m distance from the blasting hole after five days, the gas extraction effect attenuates to the level before blasting. The field test shows that under the initial impact pressure peak value of 200MPa and the borehole diameter of 0.094m, the effective radius of the fracture zone of the coal seam is 3m.
20
The precise calculation of landslide volume seems simple but difficult actually. The Loess Plateau has a few characteristics which include sparse vegetation, high degree exposure of rock and soil, and landslide susceptibility. It has occurred many landslides. Compared with the traditional calculation method, such as remote sensing and 3D laser scanning, digital close-range photogrammetry is little affected by all kinds of factors and has the features of flexible operation, high efficiency and high precision products. This paper uses Dangchuan 2# loess landslide in Heifangtai tableland as an example. It uses high resolution close-range photogrammetry data to analyze topography change between pre-sliding and post-sliding. Based on the field investigation and carrying out fine mapping of the landslide, this paper realizes the digital landslide. The detailed study consists of landslide influence, landslide area, landslide volume, loose coefficient of landslide volume and the local dry density change. The results are shown the follows.(1) It covers a total area of 105216m2, with 217m in north-south direction, and 176m in west-east direction. The average thickness of the landslide is about 20m (slip source area), with sliding 782m, trailing 122m in altitude from the landslide crown to landslide top.(2) According to the characteristics of the sliding and accumulation of each part of the slope, it is divided into the collapse zone, the main sliding zone, the sliding zone, the circulation accumulation area, the shovel winding accumulation area, the extrusion and accumulation area, the two accumulation area and the dust accumulation area.(3) According to high resolution DEM, the sliding volume is 31.72×104m3 and accumulating volume is 49.96×104m3. (4) The overall loose coefficient of the landslide is 1.411. The local dry density has great difference, which has close relationship with the development characteristics and the movement process of the landslide. The precise calculation of landslide volume seems simple but difficult actually. The Loess Plateau has a few characteristics which include sparse vegetation, high degree exposure of rock and soil, and landslide susceptibility. It has occurred many landslides. Compared with the traditional calculation method, such as remote sensing and 3D laser scanning, digital close-range photogrammetry is little affected by all kinds of factors and has the features of flexible operation, high efficiency and high precision products. This paper uses Dangchuan 2# loess landslide in Heifangtai tableland as an example. It uses high resolution close-range photogrammetry data to analyze topography change between pre-sliding and post-sliding. Based on the field investigation and carrying out fine mapping of the landslide, this paper realizes the digital landslide. The detailed study consists of landslide influence, landslide area, landslide volume, loose coefficient of landslide volume and the local dry density change. The results are shown the follows.(1) It covers a total area of 105216m2, with 217m in north-south direction, and 176m in west-east direction. The average thickness of the landslide is about 20m (slip source area), with sliding 782m, trailing 122m in altitude from the landslide crown to landslide top.(2) According to the characteristics of the sliding and accumulation of each part of the slope, it is divided into the collapse zone, the main sliding zone, the sliding zone, the circulation accumulation area, the shovel winding accumulation area, the extrusion and accumulation area, the two accumulation area and the dust accumulation area.(3) According to high resolution DEM, the sliding volume is 31.72×104m3 and accumulating volume is 49.96×104m3. (4) The overall loose coefficient of the landslide is 1.411. The local dry density has great difference, which has close relationship with the development characteristics and the movement process of the landslide.
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