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1
2018, 26(6): 1534-1551.
Abstract
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A large-scale landslide occurred in Baige village, at the border between Tibet Autonomous Region and Sichuan Province, on October 11, 2018. The sliding mass detached from a high-elevation mountain ridge, then dammed the Jinsha River impounding a barrier lake. This initial lake drained naturally. Afterwards, on November 3, a second landslide involved with a large mass of loose material from the first event blocked the river again, inducing a 50 m high dam and a barrier lake with a capacity of 500 million cubic meters. In order to alleviate the dangers of potential dam-breach flood, the artificial spillway was constructed allowing controlled breaching until November 13. However, downstream flooding still cause a major loss of property and damage, covering a large area of Sichuan Province and Yunnan Province. Extensive on-site investigation, combined with historical satellite images interpretation, InSAR monitoring, UAV aerial photography and ground deformation monitoring techniques, was conducted in this paper, to analyze the historical deformation of the study area and the evolutional characteristics of these two events. Based on that, the emergency measurements after each event have been developed, and the implementation of spillway was secured by monitoring and early-warning work at site. The successive landslides damming the Jinsha River presents a good example to study the emergency response and mitigation plan for similar cases in the future.
A large-scale landslide occurred in Baige village, at the border between Tibet Autonomous Region and Sichuan Province, on October 11, 2018. The sliding mass detached from a high-elevation mountain ridge, then dammed the Jinsha River impounding a barrier lake. This initial lake drained naturally. Afterwards, on November 3, a second landslide involved with a large mass of loose material from the first event blocked the river again, inducing a 50 m high dam and a barrier lake with a capacity of 500 million cubic meters. In order to alleviate the dangers of potential dam-breach flood, the artificial spillway was constructed allowing controlled breaching until November 13. However, downstream flooding still cause a major loss of property and damage, covering a large area of Sichuan Province and Yunnan Province. Extensive on-site investigation, combined with historical satellite images interpretation, InSAR monitoring, UAV aerial photography and ground deformation monitoring techniques, was conducted in this paper, to analyze the historical deformation of the study area and the evolutional characteristics of these two events. Based on that, the emergency measurements after each event have been developed, and the implementation of spillway was secured by monitoring and early-warning work at site. The successive landslides damming the Jinsha River presents a good example to study the emergency response and mitigation plan for similar cases in the future.
2
2014, 22(4): 684-691.
Loess Plateau is one of the birthplaces of the Chinese nation. It is also the youngest plateau and has been rising ceaselessly in our world. Besides,it had been recorded the information of global change in detail during the Pleistocene epoch,especially in the aspects of climate changes and geological hazards. According to the statistics of geological hazards in China,there are almost one third of cases in this area. These geological hazards caused great loss of life and properties. Hence,the mitigation of geological hazards in Loess Plateau is urgent and necessary. This paper summarizes geological hazards in Loess Plateau. Moreover,according to the results of previous research and engineering geological investigation,the critical issues and creative concepts,such as the couple analysis of soil mechanics and engineering geology,triggering and evolution mechanism,early warning system and so on,are suggested to mitigate the geological hazards in loess area.
Loess Plateau is one of the birthplaces of the Chinese nation. It is also the youngest plateau and has been rising ceaselessly in our world. Besides,it had been recorded the information of global change in detail during the Pleistocene epoch,especially in the aspects of climate changes and geological hazards. According to the statistics of geological hazards in China,there are almost one third of cases in this area. These geological hazards caused great loss of life and properties. Hence,the mitigation of geological hazards in Loess Plateau is urgent and necessary. This paper summarizes geological hazards in Loess Plateau. Moreover,according to the results of previous research and engineering geological investigation,the critical issues and creative concepts,such as the couple analysis of soil mechanics and engineering geology,triggering and evolution mechanism,early warning system and so on,are suggested to mitigate the geological hazards in loess area.
3
2018, 26(2): 340-347.
Wenchuan earthquake induced a large amount of geological disasters such as landslides and collapses. Besides, the earthquake also caused a lot of the loose and broken rock mass. Those loose rock mass can produce large amounts of secondary geological disasters under the rainfall and other factors, which has great danger. Therefore, it has very important practical significance for geological disaster susceptibility evaluation of Wenchuan country. Based on GIS raster data model, this paper selects nine factors including elevation, gradient, slope direction, relief amplitude, gully density, the engineering rock group, fault, drainage and roads. It adopts the information, logistic and information-logistic coupling models for assessment of geological hazards. The results show that the coupling model is more reasonable and has higher precision. High and very high susceptibility of geological hazard areas are concentrated in the water extension area and fault concentration area. Susceptibility partition map of the calculation results is consistent with the actual situation of the study area and can play an important reference role in the geological hazard risk assessment.
Wenchuan earthquake induced a large amount of geological disasters such as landslides and collapses. Besides, the earthquake also caused a lot of the loose and broken rock mass. Those loose rock mass can produce large amounts of secondary geological disasters under the rainfall and other factors, which has great danger. Therefore, it has very important practical significance for geological disaster susceptibility evaluation of Wenchuan country. Based on GIS raster data model, this paper selects nine factors including elevation, gradient, slope direction, relief amplitude, gully density, the engineering rock group, fault, drainage and roads. It adopts the information, logistic and information-logistic coupling models for assessment of geological hazards. The results show that the coupling model is more reasonable and has higher precision. High and very high susceptibility of geological hazard areas are concentrated in the water extension area and fault concentration area. Susceptibility partition map of the calculation results is consistent with the actual situation of the study area and can play an important reference role in the geological hazard risk assessment.
4
2017, 25(4): 1151-1164.
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.
5
2018, 26(1): 223-240.
A large scale of mountain rock avalanche occurred in Pusa village, Zhangjiawan town, Nayong county, Guizhou Province at about 10:30 on August 28, 2017. The rock mass with the volume of 49.1×104 m3 moved down and scraped the original loose deposits and finally formed deposits of 82.3×104 m3, which destroyed parts of Pusa village, resulted in the death of 26 persons and missing of 9 persons. Based on site investigation, unmanned aerial vehicle(UAV)photography and ground based synthetic aperture radar(GBSAR)monitoring and other technologies, this paper provides a detailed description on the characteristics and a comprehensive analysis on the dynamic process and failure mechanism of the rock avalanche. The preliminary study suggested that the rock masses of the source area were shattered due to the underground mining activities. The shattered rock masses suffered long-term effects of gravity, which eventually resulted the failure of the rock masses. The movement of the rock avalanche lasted for 7 minutes and 21 seconds in which the main rock masses failure lasted for only 26 seconds with the long runout of 788 m and the maximum speed of 43.83 m·s-1, belonging to typical high speed and long runout rock avalanche. There will be a big attribution if such case can be studied further. It can provide the significant experience on dealing with this kind of rock masses failure and how to provide advice on early warning and remediation project on similar cases in southwestern mountain areas of China.
A large scale of mountain rock avalanche occurred in Pusa village, Zhangjiawan town, Nayong county, Guizhou Province at about 10:30 on August 28, 2017. The rock mass with the volume of 49.1×104 m3 moved down and scraped the original loose deposits and finally formed deposits of 82.3×104 m3, which destroyed parts of Pusa village, resulted in the death of 26 persons and missing of 9 persons. Based on site investigation, unmanned aerial vehicle(UAV)photography and ground based synthetic aperture radar(GBSAR)monitoring and other technologies, this paper provides a detailed description on the characteristics and a comprehensive analysis on the dynamic process and failure mechanism of the rock avalanche. The preliminary study suggested that the rock masses of the source area were shattered due to the underground mining activities. The shattered rock masses suffered long-term effects of gravity, which eventually resulted the failure of the rock masses. The movement of the rock avalanche lasted for 7 minutes and 21 seconds in which the main rock masses failure lasted for only 26 seconds with the long runout of 788 m and the maximum speed of 43.83 m·s-1, belonging to typical high speed and long runout rock avalanche. There will be a big attribution if such case can be studied further. It can provide the significant experience on dealing with this kind of rock masses failure and how to provide advice on early warning and remediation project on similar cases in southwestern mountain areas of China.
6
2016, 24(6): 1088-1095.
Landslide is a critical geological disaster that has drawn general concern of the society. Earthquakes, rainfalls, reservoir operations and construction activities frequently induce large movements of high slopes and even trigger landslides or debris flows, which poses a significant threat to human lives and properties. In recent years, the monitoring technologies of slope deformation have been rapidly developed and played an increasingly important role in ensuring slope stability, verifying the effect of reinforcing measures, enhancing early warning of landslides, et al. This paper briefly introduces the conventional slope deformation monitoring technologies and their shortcomings. The latest development and applications of slope deformation monitoring technologies at home and abroad in the past few decades are presented in detail, followed by a comparison of the features of these technologies, especially the distributed fiber optic sensing technology. Finally, some research suggestions are proposed for future development of slope deformation monitoring technologies.
Landslide is a critical geological disaster that has drawn general concern of the society. Earthquakes, rainfalls, reservoir operations and construction activities frequently induce large movements of high slopes and even trigger landslides or debris flows, which poses a significant threat to human lives and properties. In recent years, the monitoring technologies of slope deformation have been rapidly developed and played an increasingly important role in ensuring slope stability, verifying the effect of reinforcing measures, enhancing early warning of landslides, et al. This paper briefly introduces the conventional slope deformation monitoring technologies and their shortcomings. The latest development and applications of slope deformation monitoring technologies at home and abroad in the past few decades are presented in detail, followed by a comparison of the features of these technologies, especially the distributed fiber optic sensing technology. Finally, some research suggestions are proposed for future development of slope deformation monitoring technologies.
7
2018, 26(1): 112-128.
Expansive soil is considered as a problematic soil in engineering, because it usually results in various engineering geological problems and disasters. According to the published results on the engineering geological characteristics of expansive soil in recent years, the advances on swelling-shrinkage behavior, desiccation cracking, overconsolidation, strength, permeability and microstructure of expansive soil were summarized, and the following main knowledge was obtained. (1)The swelling-shrinking characteristics are mainly related to the fraction of expansive clay minerals, hydro-mechanical boundary conditions and initial state. Irreversible volumetric deformation would occur when the expansive soil is subjected to wetting-drying cycles. Until now, there is still not a uniform viewpoint on the intrinsic mechanism on swelling-shrinking behavior. (2)Desiccation cracking is one of the salient features to distinguish expansive soil from other soils. The presence of cracks in soil can significantly undermine the overall structure of the soil, greatly weaken the mechanical properties and lead to many engineering geological problems directly or indirectly. The formation of desiccation cracks is related to expansive soil mineral composition, microstructure and the development of internal stress during drying. (3)Overconsolidation makes expansive soil has a greater structural strength and horizontal stress. Stress-release cracks are easy to occur when the expansive soil slope is excavated, which can damage the overall structure of the soil and promote landslide.(4)In terms of strength, most of studies focused on the effect of wetting-drying cycles. Generally, the strength decreases gradually with increasing wetting-drying cycles and eventually reaches stabilization. The wetting-drying cycle induced presence of cracks and microstructure arrangement are the two factors responsible for the corresponding strength changes. (5)The hydraulic conductivity is largely controlled by cracks. It is therefore important to consider the crack effect when performing permeability test in laboratory.(6)Microstructure of the expansive soil reflects the formation conditions and stress history. It is a fundamental factor controlling the macro-physical and mechanical behavior. Microstructure analysis is also the important way and theoretical basis to explore the intrinsic mechanisms of the observed macroscopic properties. Furthermore, as for as expansive soil engineering treatment technology, this article focused on the physical treatment technology for embankment filled with expansive soil and flexible supporting technology for expansive soil cut slope. Based on the above understanding and current research shortages in this field, some important research topics that should be well investigated in future were proposed, including anisotropic behavior of swelling-shrinking, mechanism of the desiccation cracking, quantitative relationship between geometrical parameters of cracks and the indicators of macro engineering properties, the coupling of macro-micro mechanical model and the hydro-mechanical response characteristics of expansive soil under multi-field coupling condition, et al.
Expansive soil is considered as a problematic soil in engineering, because it usually results in various engineering geological problems and disasters. According to the published results on the engineering geological characteristics of expansive soil in recent years, the advances on swelling-shrinkage behavior, desiccation cracking, overconsolidation, strength, permeability and microstructure of expansive soil were summarized, and the following main knowledge was obtained. (1)The swelling-shrinking characteristics are mainly related to the fraction of expansive clay minerals, hydro-mechanical boundary conditions and initial state. Irreversible volumetric deformation would occur when the expansive soil is subjected to wetting-drying cycles. Until now, there is still not a uniform viewpoint on the intrinsic mechanism on swelling-shrinking behavior. (2)Desiccation cracking is one of the salient features to distinguish expansive soil from other soils. The presence of cracks in soil can significantly undermine the overall structure of the soil, greatly weaken the mechanical properties and lead to many engineering geological problems directly or indirectly. The formation of desiccation cracks is related to expansive soil mineral composition, microstructure and the development of internal stress during drying. (3)Overconsolidation makes expansive soil has a greater structural strength and horizontal stress. Stress-release cracks are easy to occur when the expansive soil slope is excavated, which can damage the overall structure of the soil and promote landslide.(4)In terms of strength, most of studies focused on the effect of wetting-drying cycles. Generally, the strength decreases gradually with increasing wetting-drying cycles and eventually reaches stabilization. The wetting-drying cycle induced presence of cracks and microstructure arrangement are the two factors responsible for the corresponding strength changes. (5)The hydraulic conductivity is largely controlled by cracks. It is therefore important to consider the crack effect when performing permeability test in laboratory.(6)Microstructure of the expansive soil reflects the formation conditions and stress history. It is a fundamental factor controlling the macro-physical and mechanical behavior. Microstructure analysis is also the important way and theoretical basis to explore the intrinsic mechanisms of the observed macroscopic properties. Furthermore, as for as expansive soil engineering treatment technology, this article focused on the physical treatment technology for embankment filled with expansive soil and flexible supporting technology for expansive soil cut slope. Based on the above understanding and current research shortages in this field, some important research topics that should be well investigated in future were proposed, including anisotropic behavior of swelling-shrinking, mechanism of the desiccation cracking, quantitative relationship between geometrical parameters of cracks and the indicators of macro engineering properties, the coupling of macro-micro mechanical model and the hydro-mechanical response characteristics of expansive soil under multi-field coupling condition, et al.
8
2016, 24(2): 167-180.
A small scale of loess landslide occurred at Heifangtai in Dangchuan village of Yongjing county. Its occurrence is at 7:50 of April 29, 2015. The site is at the edge of the loess plateau. The instability of loess has a volume of 5104m3. It runs from the forth terrace to the second terrace of the Yellow river. After 3 hours later, however, a large scale of mudstone occurred at this place. Its volume is of 3.5105m3. The mudstone deposit is 780meters long, 100meters wide and the largest thickness of deposit is 17meters. The landslide is one of the few catastrophic landslides. This paper examines the sliding displacement monitoring and the crack distribution. Such examinations are combined with site geological investigation, low-altitude photogrammetry, site engineering geological survey and site moisture content test. This paper analyses the basic characteristics of the landslide and the formation and reasons of landslide by preliminary understanding. The results show that:(1)There are two sliding cases at Dangchuan 2# landslide from the time. There is only one sliding case time in first time sliding and three sliding cases in second times landslide from sliding mode and deposit characteristic. Dangchuan 2# landslide has four times sliding cases in all. (2)The area of the first sliding is 8396m2. Deformation distribution area is only at the edge of plateau and is smaller compared with the sliding area. The long-term creep deformation at the bottom of loess is the inducing factors of the first time landslide. (3)The area of the second sliding is 27422m2. There is rarely any crack at this part and the crack has no obvious deformation before the second times sliding. The liquefaction of the loess at the bottom of landslide plays a very important role in the second times sliding. The landslide has the characteristics such as sudden occurrence, movement long distance and destructive stronger. (4)The Dangchuan section begins to start mass type static liquefaction loess landslide and the boundary of landslide is the sinkholes, which is of great significance that is the research about other section of early recognition of loess landslide and monitoring and early warning of loess landslide.
A small scale of loess landslide occurred at Heifangtai in Dangchuan village of Yongjing county. Its occurrence is at 7:50 of April 29, 2015. The site is at the edge of the loess plateau. The instability of loess has a volume of 5104m3. It runs from the forth terrace to the second terrace of the Yellow river. After 3 hours later, however, a large scale of mudstone occurred at this place. Its volume is of 3.5105m3. The mudstone deposit is 780meters long, 100meters wide and the largest thickness of deposit is 17meters. The landslide is one of the few catastrophic landslides. This paper examines the sliding displacement monitoring and the crack distribution. Such examinations are combined with site geological investigation, low-altitude photogrammetry, site engineering geological survey and site moisture content test. This paper analyses the basic characteristics of the landslide and the formation and reasons of landslide by preliminary understanding. The results show that:(1)There are two sliding cases at Dangchuan 2# landslide from the time. There is only one sliding case time in first time sliding and three sliding cases in second times landslide from sliding mode and deposit characteristic. Dangchuan 2# landslide has four times sliding cases in all. (2)The area of the first sliding is 8396m2. Deformation distribution area is only at the edge of plateau and is smaller compared with the sliding area. The long-term creep deformation at the bottom of loess is the inducing factors of the first time landslide. (3)The area of the second sliding is 27422m2. There is rarely any crack at this part and the crack has no obvious deformation before the second times sliding. The liquefaction of the loess at the bottom of landslide plays a very important role in the second times sliding. The landslide has the characteristics such as sudden occurrence, movement long distance and destructive stronger. (4)The Dangchuan section begins to start mass type static liquefaction loess landslide and the boundary of landslide is the sinkholes, which is of great significance that is the research about other section of early recognition of loess landslide and monitoring and early warning of loess landslide.
9
2017, 25(5): 1165-1181.
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.
10
2018, 26(6): 1648-1656.
In the northwest, a lot of multi-stage high slopes with loess have been encountered in the construction of basic engineering. Slope engineering belongs to permanent project. So it is unavoidable to meet the conditions of rainfall. Under rainfall infiltration, the degree of saturation and mass of soil slope increase, which can further cause the change of slope matric suction and effective stress. As a result, the stability of the slope can be greatly influenced. In this paper, the coupling calculation model of seepage field and stress field is established. It considers the changes of the matrix suction as the rain water infiltration at the different depths of the slope body. Then, the stability of the multi-stage high slope with loess under the condition of rainfall infiltration can be analyzed. Then, according to an actual engineering and using the PLAXIS 3D geotechnical finite element software, the calculation model of slope stability is established. By setting the variation function of rainfall with the time and boundary condition, the stability calculation of multi-stage high slope with loess is carried out under the condition of rainfall infiltration. And then, The numerical calculation results are compared with the theoretical calculation results. According to the numerical calculation results, the changes of the deformation, matrix suction, effective stress, potential slip surface and safety factor of the multi-stage high slope with loess under the condition of rainfall infiltration are obtained. And the stability of the multi-stage high slope with loess under the condition of rainfall infiltration are analyzed. The study results can provide some guidance for the design of the multi-stage high slope with loess under the rainfall infiltration.
In the northwest, a lot of multi-stage high slopes with loess have been encountered in the construction of basic engineering. Slope engineering belongs to permanent project. So it is unavoidable to meet the conditions of rainfall. Under rainfall infiltration, the degree of saturation and mass of soil slope increase, which can further cause the change of slope matric suction and effective stress. As a result, the stability of the slope can be greatly influenced. In this paper, the coupling calculation model of seepage field and stress field is established. It considers the changes of the matrix suction as the rain water infiltration at the different depths of the slope body. Then, the stability of the multi-stage high slope with loess under the condition of rainfall infiltration can be analyzed. Then, according to an actual engineering and using the PLAXIS 3D geotechnical finite element software, the calculation model of slope stability is established. By setting the variation function of rainfall with the time and boundary condition, the stability calculation of multi-stage high slope with loess is carried out under the condition of rainfall infiltration. And then, The numerical calculation results are compared with the theoretical calculation results. According to the numerical calculation results, the changes of the deformation, matrix suction, effective stress, potential slip surface and safety factor of the multi-stage high slope with loess under the condition of rainfall infiltration are obtained. And the stability of the multi-stage high slope with loess under the condition of rainfall infiltration are analyzed. The study results can provide some guidance for the design of the multi-stage high slope with loess under the rainfall infiltration.
11
2014, 22(3): 474-481.
Landslides are the most common geohazards in mountainous terrains and can cause extraordinary landscape changes and destruction of people's lives and properties. So assessing landslide hazards is significant and can provide valuable information to planners,developers and engineers. This paper examines some landslides at a hilly area of western China,Guizhou province. The purpose is to generate a landslide susceptibility map using the weights of evidence. It is based on the GIS technology and combined with landslides inventory and environmental factors. The causal factors include lithology,tectonic,elevation,slope,aspect,relief,distance from road and distance from stream. The weight of each causal class is calculated in a GIS software ArcGIS 10. Then the landslide hazard index of each unit is produced and divided into four classes: very high hazard,high hazard,medium hazard and low hazard. Finally,a success rate curve is built to detect the capability rate of the method. The study area under the curve is 0.71.A hazard zonation map is produced and the predictive power of the map is tested on the basis of landslides inventory. The evaluation results are in line with the landslides distribution. The weights of evidence are effective to assess the landslides hazard in regional scale.
Landslides are the most common geohazards in mountainous terrains and can cause extraordinary landscape changes and destruction of people's lives and properties. So assessing landslide hazards is significant and can provide valuable information to planners,developers and engineers. This paper examines some landslides at a hilly area of western China,Guizhou province. The purpose is to generate a landslide susceptibility map using the weights of evidence. It is based on the GIS technology and combined with landslides inventory and environmental factors. The causal factors include lithology,tectonic,elevation,slope,aspect,relief,distance from road and distance from stream. The weight of each causal class is calculated in a GIS software ArcGIS 10. Then the landslide hazard index of each unit is produced and divided into four classes: very high hazard,high hazard,medium hazard and low hazard. Finally,a success rate curve is built to detect the capability rate of the method. The study area under the curve is 0.71.A hazard zonation map is produced and the predictive power of the map is tested on the basis of landslides inventory. The evaluation results are in line with the landslides distribution. The weights of evidence are effective to assess the landslides hazard in regional scale.
12
2014, 22(4): 557-585.
Daguangbao landslide with an area of 7.12km2 and a volume of 1.159 billion m3 is the largest landslide triggered by the Wenchuan MS8.0 Earthquake occurred on May 12th,2008,and also is the largest one in China and one of the few giant landslides more than one billion m3 in the world. It is located in the hanging wall of the seismogenic fault of the Wenchuan earthquake,and 3.0～4.5km away from it. The authors' team has conducted a engineering geological survey including mapping,geophysical exploration,pitting and boreholes with a scale of 1:2000 since 2011. According to the data,we finished a series of geological maps including a comprehensive plane map and 25 sections. The spatial shape of the landslide,pre- and post-failure structures,slip surface and its characteristics were further investigated and a set of quantitative data about Daguangbao landslide features was obtained. We found it was a hugewedge failure with a strike slipping sliding along a bedded shear fault. According to the description of witnesses and structures of the accumulation,we rebuilt the experience of the slope failure and sliding process during the strong quaking. Basically,it can be divided into five stages:shattering-tensile cracking,cutting through of the front locking section,suddenly braking and napping motion,detaching sliding on both sides of the accumulation and finally secondary sliding of the scarp cliff. The accumulation can be divided into three area and ten sub-areas. They are the main scarp area,the accumulation area,and the back depression area,which corresponding to three,four and three sub-areas respectively.
Daguangbao landslide with an area of 7.12km2 and a volume of 1.159 billion m3 is the largest landslide triggered by the Wenchuan MS8.0 Earthquake occurred on May 12th,2008,and also is the largest one in China and one of the few giant landslides more than one billion m3 in the world. It is located in the hanging wall of the seismogenic fault of the Wenchuan earthquake,and 3.0～4.5km away from it. The authors' team has conducted a engineering geological survey including mapping,geophysical exploration,pitting and boreholes with a scale of 1:2000 since 2011. According to the data,we finished a series of geological maps including a comprehensive plane map and 25 sections. The spatial shape of the landslide,pre- and post-failure structures,slip surface and its characteristics were further investigated and a set of quantitative data about Daguangbao landslide features was obtained. We found it was a hugewedge failure with a strike slipping sliding along a bedded shear fault. According to the description of witnesses and structures of the accumulation,we rebuilt the experience of the slope failure and sliding process during the strong quaking. Basically,it can be divided into five stages:shattering-tensile cracking,cutting through of the front locking section,suddenly braking and napping motion,detaching sliding on both sides of the accumulation and finally secondary sliding of the scarp cliff. The accumulation can be divided into three area and ten sub-areas. They are the main scarp area,the accumulation area,and the back depression area,which corresponding to three,four and three sub-areas respectively.
13
USE OF UNMANNED AERIAL VEHICLE FOR PRECISE INVESTIGATION OF GEOLOGICAL HAZARD IN STRONG SEISMIC ZONE
2016, 24(4): 713-719.
This paper aims to investigate geological hazard precisely in strong seismic zone. It uses unmanned aerial vehicle based low-altitude photographic system. The system can obtain high-precision, high-resolution and high-altitude remote sensing image, and has the advantage of flexibility and freedom from complex topography. This paper applies the system to the precise investigation of geological hazard, the precise investigation procedure of geological hazard in strong seismic zone. The application of results are discussed. The paper takes the application in the Laohuzui landslide zone as an example. It describes the remote sensing image extraction and the method of DEM,DOM and three-dimensional real space scene. It focuses on introducing the qualitative and quantitative analysis of the geological hazard and the precise description. The practice results show that:(1) compared with the conventional remote sensing investigation method, this method not only obtains higher-resolution and higher-precision basic data for the precise investigation of the geological hazard, but also improves its efficacy and reliability; (2) three-dimensional real space scene of the geological hazard breaks through the traditional two-dimensional interpretation method, improves the precision and accuracy of the geological hazard. The system can be applied to the precise investigation of geological hazard in strong seismic zone.
This paper aims to investigate geological hazard precisely in strong seismic zone. It uses unmanned aerial vehicle based low-altitude photographic system. The system can obtain high-precision, high-resolution and high-altitude remote sensing image, and has the advantage of flexibility and freedom from complex topography. This paper applies the system to the precise investigation of geological hazard, the precise investigation procedure of geological hazard in strong seismic zone. The application of results are discussed. The paper takes the application in the Laohuzui landslide zone as an example. It describes the remote sensing image extraction and the method of DEM,DOM and three-dimensional real space scene. It focuses on introducing the qualitative and quantitative analysis of the geological hazard and the precise description. The practice results show that:(1) compared with the conventional remote sensing investigation method, this method not only obtains higher-resolution and higher-precision basic data for the precise investigation of the geological hazard, but also improves its efficacy and reliability; (2) three-dimensional real space scene of the geological hazard breaks through the traditional two-dimensional interpretation method, improves the precision and accuracy of the geological hazard. The system can be applied to the precise investigation of geological hazard in strong seismic zone.
14
2019, 27(2): 415-425.
On October 11, 2018, a massive landslide occurred in Baige Village, Boluo Town, Jiangdacounty, Changdu city, Tibet. About 3, 165×104 cubic meter of a mountain mass rushed into the Jinsha River at a high speed, thus forming a barrier dam. At 9:00 on October 13, the body of the barrier dam was washed away by natural aerial drainage and the threat of forming a barrier lake was resolved. On November 3, only 23 days later, the high slip mass of 215×104 cubic meter at the back edge of the landslide occurred sliding failure again. The high-speed slip mass scraped the slope along the way and then rushed into the Jinsha River, forming a barrier dam again. This paper held the view that the landslide happened in Baige Village was thought to be mainly controlled by the next branch margin thrust fault f2, then finally generated buckling failure of the overall instability of the landslide with the influence of a long-term gravity unloading, rainfall and repeated infiltration of groundwater. The process of slip deformation and failure can be divided into five stages:trailing creep and settlement under the fault phase(Ⅰ), slope crack development, penetration stage(Ⅱ), overall launch of the "locking-fix end" cutting stage(Ⅲ), a stage with high moving speed(Ⅳ), collided, crushing and dam accumulation stage(Ⅴ). The failure mode of the first-stage deformation and failure mechanism can be summed up as creep-slip type-down fault type-shearing type-ski-jump type, and the failure mode is shown as the thrust type. In the later stage, the free surface condition of the slope is better, and the traction type can remain as the main failure mode. On this basis, combined with the residual strong deformation block(K1, K2, K3) and morphological characteristics and deformation signs of the surrounding influence zone, this paper predicted and analyzed the deformation and failure characteristics and development trend of the block, deeming that strong deformation areas can be destroyed by gradual disintegration. And these research findings can provide some reference for the monitoring, survey and governance of the future plan making and implementation.
On October 11, 2018, a massive landslide occurred in Baige Village, Boluo Town, Jiangdacounty, Changdu city, Tibet. About 3, 165×104 cubic meter of a mountain mass rushed into the Jinsha River at a high speed, thus forming a barrier dam. At 9:00 on October 13, the body of the barrier dam was washed away by natural aerial drainage and the threat of forming a barrier lake was resolved. On November 3, only 23 days later, the high slip mass of 215×104 cubic meter at the back edge of the landslide occurred sliding failure again. The high-speed slip mass scraped the slope along the way and then rushed into the Jinsha River, forming a barrier dam again. This paper held the view that the landslide happened in Baige Village was thought to be mainly controlled by the next branch margin thrust fault f2, then finally generated buckling failure of the overall instability of the landslide with the influence of a long-term gravity unloading, rainfall and repeated infiltration of groundwater. The process of slip deformation and failure can be divided into five stages:trailing creep and settlement under the fault phase(Ⅰ), slope crack development, penetration stage(Ⅱ), overall launch of the "locking-fix end" cutting stage(Ⅲ), a stage with high moving speed(Ⅳ), collided, crushing and dam accumulation stage(Ⅴ). The failure mode of the first-stage deformation and failure mechanism can be summed up as creep-slip type-down fault type-shearing type-ski-jump type, and the failure mode is shown as the thrust type. In the later stage, the free surface condition of the slope is better, and the traction type can remain as the main failure mode. On this basis, combined with the residual strong deformation block(K1, K2, K3) and morphological characteristics and deformation signs of the surrounding influence zone, this paper predicted and analyzed the deformation and failure characteristics and development trend of the block, deeming that strong deformation areas can be destroyed by gradual disintegration. And these research findings can provide some reference for the monitoring, survey and governance of the future plan making and implementation.
15
2014, 22(6): 1135-1146.
In recent years, due to the change of natural environment and the influence of human engineering activities, the occurrence probability of geological disasters such as soil erosion and landslides have been increasing. These geological disasters bring some damages to people's living and productive activities. Methods of soil fixation and slope protection by vegetation can prevent and control the geological disasters. The soil fixation and slope protection by vegetation can be mainly reflected in two aspects: hydrological effect by the stems and leaves of plants and the mechanical effect by the root of plants. Hydrological effect includes rainfall interception effect and rainfall reallocation effect by plant stems and leaves, effect of reduction in raindrop splash erosion by foliage, and plant residues and surface runoff retardation effect by plant above-ground residues. The mechanical effect includes reinforcement effect by fibril roots, anchorage effect by taproots, and traction effect by horizontal roots. The paper highlights the research status of hydrological effect and mechanical effect. For hydrological effect, content such as rainfall interception effect and rainfall reallocation effect by plant stems and leaves, effect of reduction in raindrop splash erosion by foliage and so on are the key contents. For mechanical effect, the theoretical models for the additional cohesion force due to the presence of roots, the interaction between plant roots and the surrounding soil matrix and the numerical simulation methods for the mechanical effect of the slope protection by vegetation are emphasized. In addition, the development tendency of soil fixation and slope protection by vegetation has been predicted. For hydrological effect, a further investigation on the influence of water migration among atmosphere-soil-plant on slope stability is desirable. For the theoretical models of root-soil composite system, a further exploration on the working conditions for which the Wu-Waldron-Model and Fiber-Bundle-Model can be suitable, is necessary. For the numerical simulation methods, effort is needed to explore a model that meet the real condition. With the establishment of numerical model, the parameters such as the root architecture features, root length and so on, as well as these parameters influencing on the calculation results should be taken into account systematically. For the engineering practice, a further study on the application of slope protection by vegetation should be performed to explore the application and maintenance of slope protection by vegetation in different geological and climatic conditions to ensure that slope protection by vegetation can play an eminent role in engineering practice as well as embodying the combination of hydrological effect, mechanical effect and landscape effect.
In recent years, due to the change of natural environment and the influence of human engineering activities, the occurrence probability of geological disasters such as soil erosion and landslides have been increasing. These geological disasters bring some damages to people's living and productive activities. Methods of soil fixation and slope protection by vegetation can prevent and control the geological disasters. The soil fixation and slope protection by vegetation can be mainly reflected in two aspects: hydrological effect by the stems and leaves of plants and the mechanical effect by the root of plants. Hydrological effect includes rainfall interception effect and rainfall reallocation effect by plant stems and leaves, effect of reduction in raindrop splash erosion by foliage, and plant residues and surface runoff retardation effect by plant above-ground residues. The mechanical effect includes reinforcement effect by fibril roots, anchorage effect by taproots, and traction effect by horizontal roots. The paper highlights the research status of hydrological effect and mechanical effect. For hydrological effect, content such as rainfall interception effect and rainfall reallocation effect by plant stems and leaves, effect of reduction in raindrop splash erosion by foliage and so on are the key contents. For mechanical effect, the theoretical models for the additional cohesion force due to the presence of roots, the interaction between plant roots and the surrounding soil matrix and the numerical simulation methods for the mechanical effect of the slope protection by vegetation are emphasized. In addition, the development tendency of soil fixation and slope protection by vegetation has been predicted. For hydrological effect, a further investigation on the influence of water migration among atmosphere-soil-plant on slope stability is desirable. For the theoretical models of root-soil composite system, a further exploration on the working conditions for which the Wu-Waldron-Model and Fiber-Bundle-Model can be suitable, is necessary. For the numerical simulation methods, effort is needed to explore a model that meet the real condition. With the establishment of numerical model, the parameters such as the root architecture features, root length and so on, as well as these parameters influencing on the calculation results should be taken into account systematically. For the engineering practice, a further study on the application of slope protection by vegetation should be performed to explore the application and maintenance of slope protection by vegetation in different geological and climatic conditions to ensure that slope protection by vegetation can play an eminent role in engineering practice as well as embodying the combination of hydrological effect, mechanical effect and landscape effect.
16
The monitoring of ground fissures plays an important role in the prevention and control of the ground fissure hazard. In this paper, BOTDR-based distributed monitoring technology is used to monitor the development process of ground fissures. The principle of distributed optical fiber sensing technology and the distributed monitoring method are introduced. The field monitoring of ground fissures located in Wuxi is studied. The results show that BOTDR-based distributed monitoring technology can be effectively used to the deformation monitoring of ground fissures. Its monitoring accuracy and measuring range can be improved by the fixed-point layout of optical fiber. The monitoring accuracy can reach 0.1mm and the measuring range can raise 30mm. The multiple ground fissures within a certain area can be monitored by the gridded laying of optical fiber. The positioning accuracy of the ground fissure monitoring can be improved by setting up the different lengths between two fixed-points along the same direction.
The monitoring of ground fissures plays an important role in the prevention and control of the ground fissure hazard. In this paper, BOTDR-based distributed monitoring technology is used to monitor the development process of ground fissures. The principle of distributed optical fiber sensing technology and the distributed monitoring method are introduced. The field monitoring of ground fissures located in Wuxi is studied. The results show that BOTDR-based distributed monitoring technology can be effectively used to the deformation monitoring of ground fissures. Its monitoring accuracy and measuring range can be improved by the fixed-point layout of optical fiber. The monitoring accuracy can reach 0.1mm and the measuring range can raise 30mm. The multiple ground fissures within a certain area can be monitored by the gridded laying of optical fiber. The positioning accuracy of the ground fissure monitoring can be improved by setting up the different lengths between two fixed-points along the same direction.
17
2015, 23(2): 287-300.
When the ultrasonic wave propagates in rock and soil, it carries lots of information related to the physical and mechanical properties of geotechnical medium. The information can be integrated and reflected in change of a series of acoustic parameters including ultrasonic velocity, attenuation coefficient, waveform, frequency, frequency spectrum and amplitude. Based on these parameters, the physical and mechanical properties of rock mass and mesoscopic structure characteristics can be investigated indirectly, so as to solve a series of geotechnical engineering problems. In this paper, the geotechnical problems which can be resolved by ultrasonic nondestructive testing are summarized. A systematic review is performed on the progresses of ultrasonic testing in soil and rock, which include the work of soil strength parameters, the microstructure of soil parameters, the obtaining of rock strength parameters by ultrasonic test, the rock fracturing mechanism, the application of ultrasonic wave attenuation in rock materials, the anisotropy of ultrasonic velocity and attenuation and research of ultrasonic test in flow test. Finally, the ultrasonic test is broadened in the research field of rock and soil aggregate. Wave velocity and attenuation law with specimens of different rock percentage are discussed. Also during compressive test, the meso-damage characteristics are analyzed with acoustic parameters, to illustrate that the rock and soil aggregate which is not only different from soil but also different from rock. Based on the above research, the development tendency of ultrasonic test is also prospected.
When the ultrasonic wave propagates in rock and soil, it carries lots of information related to the physical and mechanical properties of geotechnical medium. The information can be integrated and reflected in change of a series of acoustic parameters including ultrasonic velocity, attenuation coefficient, waveform, frequency, frequency spectrum and amplitude. Based on these parameters, the physical and mechanical properties of rock mass and mesoscopic structure characteristics can be investigated indirectly, so as to solve a series of geotechnical engineering problems. In this paper, the geotechnical problems which can be resolved by ultrasonic nondestructive testing are summarized. A systematic review is performed on the progresses of ultrasonic testing in soil and rock, which include the work of soil strength parameters, the microstructure of soil parameters, the obtaining of rock strength parameters by ultrasonic test, the rock fracturing mechanism, the application of ultrasonic wave attenuation in rock materials, the anisotropy of ultrasonic velocity and attenuation and research of ultrasonic test in flow test. Finally, the ultrasonic test is broadened in the research field of rock and soil aggregate. Wave velocity and attenuation law with specimens of different rock percentage are discussed. Also during compressive test, the meso-damage characteristics are analyzed with acoustic parameters, to illustrate that the rock and soil aggregate which is not only different from soil but also different from rock. Based on the above research, the development tendency of ultrasonic test is also prospected.
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