Most Cited Articles

(The cited data comes from the whole network and is updated monthly.)
1
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.
2
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.
3
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.
4
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.
5
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.
6
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.
7
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.
8
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.
9
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.
10
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.
11
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.
12
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.
13
Many landslides in the Three Gorges Reservoir area have large deformation during the drawdown of reservoir water level every year. In order to study the dynamic deformation mechanism, stability and development trend of landslide during drawdown of reservoir water level, this paper takes Baishuihe landslide as an example. Based on the field geological survey, detailed geological exploration, and full use of monitoring data of more than ten years, the deformation characteristics, mechanism, influence factors and stability of landslide are analyzed in detail, and the deformation trend of landslide is predicted. Analysis results show that, during the drawdown of reservoir water level, underground water can not be discharged in time due to the landslide soil permeability is poor. Because decline speed of groundwater is much slower than that of reservoir water, increasing the seepage force in the landslide body apparently, and then further reduces the slope stability. The landslide deformation rate increases with the increasing of decline speed of reservoir water level, and the landslide deformation shows dynamic characteristic of step type. Many landslides in the Three Gorges Reservoir area have large deformation during the drawdown of reservoir water level every year. In order to study the dynamic deformation mechanism, stability and development trend of landslide during drawdown of reservoir water level, this paper takes Baishuihe landslide as an example. Based on the field geological survey, detailed geological exploration, and full use of monitoring data of more than ten years, the deformation characteristics, mechanism, influence factors and stability of landslide are analyzed in detail, and the deformation trend of landslide is predicted. Analysis results show that, during the drawdown of reservoir water level, underground water can not be discharged in time due to the landslide soil permeability is poor. Because decline speed of groundwater is much slower than that of reservoir water, increasing the seepage force in the landslide body apparently, and then further reduces the slope stability. The landslide deformation rate increases with the increasing of decline speed of reservoir water level, and the landslide deformation shows dynamic characteristic of step type.
14
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.
15
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
Monitoring and early warning have become the important means of preventing geohazards with rapid development in technology. A great deal of financial, manpower and physical resources have been adopted to work on landslide monitoring and early warning. However, some technical and managerial personnel have misunderstandings in landslide monitoring and early warning, which seriously affects the geohazards prevention and mitigation effects. Based on research results and lessons learned in practice over recent years, this paper discusses on some basic issues in terms of landslide monitoring and early warning. Main points include:(1)It is not that more monitoring locations and methods are better. The landslide monitoring plan should highlight pertinence, practicability and purpose, and its design and content mainly provide the basis for landslide early warning; (2)The occurrence for many landslides is sudden, and monitoring equipment with self-adaptive data acquisition function should be used to get entire deformation data, especially the accelerated creep stage, to guarantee scientific alert. (3)Monitoring is just a means to an end, while early warning is the end goal. Much attention should be paid on landslide early warning, like regional-scale meteorological early warning and slope-scale landslide early warning; (4)The commonly used early warning models with thresholds have a high rate of false and missing alarms. The study on statistical analysis of historical data, early warning models based on key parameters of deformation, underground water level and precipitation, become a high priority to improve the accuracy and practicality of landslide early warning. Monitoring and early warning have become the important means of preventing geohazards with rapid development in technology. A great deal of financial, manpower and physical resources have been adopted to work on landslide monitoring and early warning. However, some technical and managerial personnel have misunderstandings in landslide monitoring and early warning, which seriously affects the geohazards prevention and mitigation effects. Based on research results and lessons learned in practice over recent years, this paper discusses on some basic issues in terms of landslide monitoring and early warning. Main points include:(1)It is not that more monitoring locations and methods are better. The landslide monitoring plan should highlight pertinence, practicability and purpose, and its design and content mainly provide the basis for landslide early warning; (2)The occurrence for many landslides is sudden, and monitoring equipment with self-adaptive data acquisition function should be used to get entire deformation data, especially the accelerated creep stage, to guarantee scientific alert. (3)Monitoring is just a means to an end, while early warning is the end goal. Much attention should be paid on landslide early warning, like regional-scale meteorological early warning and slope-scale landslide early warning; (4)The commonly used early warning models with thresholds have a high rate of false and missing alarms. The study on statistical analysis of historical data, early warning models based on key parameters of deformation, underground water level and precipitation, become a high priority to improve the accuracy and practicality of landslide early warning.
17
In order to better provide a theoretical basis for the treatment and prevention of the covered karst collapse(CKGC),according to the differences of material composition, geological structure, physical and mechanical properties of overburden on karst, for the first time, CKGC is divided into three types of mechanism, which are respectively called by hourglass type collapse, soil-cave type collapse and soft soil flow type collapse. In the distribution area of sandy soil, hourglass type collapse is caused by sand particles loss to the karst channels and karst caves because external factors triggering. Gravity and effective space provided by karst are necessary conditions for the occurrence of hourglass type collapse, and the role of groundwater accelerates the occurrence and shortens the process of hourglass type collapse. The ground subsidence phenomenon caused by soil-cave roof arching failure is called soil-cave type collapse occurring in clay and dense sand soil. The natural soil-cave is formed by three ways of the surface and groundwater erosion action, sand loss and soft soil flow. The roof of soil-cave is stable in the period of the formation and development of soil-cave, and ground subsidence occurs when the cave roof arching failure by triggering of external factors. The soil-cave type collapse has the characteristics of concealment and burst. The ground subsidence phenomenon caused by the soft soil flow is called as soft soil flow type collapse, is the result of the soft soil loss through karst channel and cave. The triggering factors of CKGC include groundwater action(vertical and horizontal seepage and underground water level frequent fluctuation at the soil/rock interface),external load(dynamic load and static load) and soil-cave roof resistance reduction(strength and thickness decrease and structure destruction of the roof).These external factors trigger the occurrence of CKGC. In order to better provide a theoretical basis for the treatment and prevention of the covered karst collapse(CKGC),according to the differences of material composition, geological structure, physical and mechanical properties of overburden on karst, for the first time, CKGC is divided into three types of mechanism, which are respectively called by hourglass type collapse, soil-cave type collapse and soft soil flow type collapse. In the distribution area of sandy soil, hourglass type collapse is caused by sand particles loss to the karst channels and karst caves because external factors triggering. Gravity and effective space provided by karst are necessary conditions for the occurrence of hourglass type collapse, and the role of groundwater accelerates the occurrence and shortens the process of hourglass type collapse. The ground subsidence phenomenon caused by soil-cave roof arching failure is called soil-cave type collapse occurring in clay and dense sand soil. The natural soil-cave is formed by three ways of the surface and groundwater erosion action, sand loss and soft soil flow. The roof of soil-cave is stable in the period of the formation and development of soil-cave, and ground subsidence occurs when the cave roof arching failure by triggering of external factors. The soil-cave type collapse has the characteristics of concealment and burst. The ground subsidence phenomenon caused by the soft soil flow is called as soft soil flow type collapse, is the result of the soft soil loss through karst channel and cave. The triggering factors of CKGC include groundwater action(vertical and horizontal seepage and underground water level frequent fluctuation at the soil/rock interface),external load(dynamic load and static load) and soil-cave roof resistance reduction(strength and thickness decrease and structure destruction of the roof).These external factors trigger the occurrence of CKGC.
18
Numerous wading landslides formed in Three Gorges Reservoir. Water level cyclical fluctuations causes the changes of properties of the rock-soil bank landslides, also make the changes of seepage field and the stability of the landslides. This paper studies the response of the wading landslides stability induced by water level fluctuation. It analyses the hydrodynamic pressure landslide using the classification of significant wading landslide in Three Gorges Reservoir. It takes the Zigui Shuping Landslide as a case study. The SEEP and SLOPE modules Geo-studio software are used to model the process of seepage field and calculate the stability, analyzes the law of effect hydrodynamic pressure landslide under different permeability coefficients of the landslide and the water level rate. The results show that the groundwater level has a concave phenomenon and the stability coefficient increases when the reservoir water level rises. The groundwater level has a convex phenomenon and the stability coefficient obvious decreases when the reservoir water level reduces for hydrodynamic pressure landslide. The reservoir water level fluctuation has the larger rate, and the permeability coefficient is smaller. The reservoir water level fluctuation has more obvious effect on the seepage and stability of the landslide. Numerous wading landslides formed in Three Gorges Reservoir. Water level cyclical fluctuations causes the changes of properties of the rock-soil bank landslides, also make the changes of seepage field and the stability of the landslides. This paper studies the response of the wading landslides stability induced by water level fluctuation. It analyses the hydrodynamic pressure landslide using the classification of significant wading landslide in Three Gorges Reservoir. It takes the Zigui Shuping Landslide as a case study. The SEEP and SLOPE modules Geo-studio software are used to model the process of seepage field and calculate the stability, analyzes the law of effect hydrodynamic pressure landslide under different permeability coefficients of the landslide and the water level rate. The results show that the groundwater level has a concave phenomenon and the stability coefficient increases when the reservoir water level rises. The groundwater level has a convex phenomenon and the stability coefficient obvious decreases when the reservoir water level reduces for hydrodynamic pressure landslide. The reservoir water level fluctuation has the larger rate, and the permeability coefficient is smaller. The reservoir water level fluctuation has more obvious effect on the seepage and stability of the landslide.
19
Bailong river basin is one of the four regions with high incidences of landslide and debris flow in China. Thus it is of vital importance to carry out hazard mapping of the landslides in this region to provide references for disaster management and construction planning. Using slope units as the basic assessment units, this research firstly gets the 6most contributing factors of landslides by means of principal component analysis and independence test. Then, the methods of Logistic Regression(LR) and Support Vector Machine(SVM) are conducted for landslide hazard mapping. Results show that (1) both LR and SVM can effectively evaluate the hazards of landslides in the region; (2)the SVM has a better ability in classification, predicting accuracy and model stability. According to the results of the two models, the study area are classified into five categories,i.e., very high dangerous zone, high dangerous zone, moderate dangerous zone, low dangerous zone and very low dangerous zone, taking an area proportion of 38.76%、14.48%、9.40%、11.28%、26.07% and 13.49%、21.61%、8.17%、26.70%、30.04%,respectively. Bailong river basin is one of the four regions with high incidences of landslide and debris flow in China. Thus it is of vital importance to carry out hazard mapping of the landslides in this region to provide references for disaster management and construction planning. Using slope units as the basic assessment units, this research firstly gets the 6most contributing factors of landslides by means of principal component analysis and independence test. Then, the methods of Logistic Regression(LR) and Support Vector Machine(SVM) are conducted for landslide hazard mapping. Results show that (1) both LR and SVM can effectively evaluate the hazards of landslides in the region; (2)the SVM has a better ability in classification, predicting accuracy and model stability. According to the results of the two models, the study area are classified into five categories,i.e., very high dangerous zone, high dangerous zone, moderate dangerous zone, low dangerous zone and very low dangerous zone, taking an area proportion of 38.76%、14.48%、9.40%、11.28%、26.07% and 13.49%、21.61%、8.17%、26.70%、30.04%,respectively.
20
This paper uses scanning electron microscope and optical digital microscope to analyzes the relationship between the structure changes of surface micro-area on loess sample and its collapsibility, the soil samples microstructures at different depths influenced by both water and load before and after loess collapse. The image of microstructure is studied by image processing software. The number variation of large pores, medium pores, small pores and micro-pores before and after the loess collapses are analyzed. The results show that after collapse of the loess, the micro pores increase by 31.18%, small pores increase by 54.07%, medium pores decrease by 30.49%, large pores decrease by 90.14%.This shows that with increasing of pressure, the pores of loess are gradually compressed. The numbers of medium pores and large pores gradually decrease while the numbers of small pores and micro-pores gradually increase, which provide sufficient space for collapsible deformation of loess. The contribution of the four types of porosity to loess collapsibility is discussed to comprehensively analyze the formation mechanism of loess collapsibility form the micro perspective. This paper uses scanning electron microscope and optical digital microscope to analyzes the relationship between the structure changes of surface micro-area on loess sample and its collapsibility, the soil samples microstructures at different depths influenced by both water and load before and after loess collapse. The image of microstructure is studied by image processing software. The number variation of large pores, medium pores, small pores and micro-pores before and after the loess collapses are analyzed. The results show that after collapse of the loess, the micro pores increase by 31.18%, small pores increase by 54.07%, medium pores decrease by 30.49%, large pores decrease by 90.14%.This shows that with increasing of pressure, the pores of loess are gradually compressed. The numbers of medium pores and large pores gradually decrease while the numbers of small pores and micro-pores gradually increase, which provide sufficient space for collapsible deformation of loess. The contribution of the four types of porosity to loess collapsibility is discussed to comprehensively analyze the formation mechanism of loess collapsibility form the micro perspective.
  • First
  • Prev
  • 1
  • 2
  • 3
  • 4
  • 5
  • Last
  • Total:65
  • To
  • Go