2021 Vol. 32 No. 5
Abstract：
The Jinshajiang suture zone is a high-incidence area of landslide disasters and has a greater threat of river jamming. In this paper, the Sela landslide with high risk of blocking rivers was taken as the research object, and the Sentinel-1A/B images were selected and processed by MSBAS InSAR technology to obtain the surface deformation of the landslide. We used the Sentinel-1A/B images from different orbits to obtain the two-dimensional dynamic deformation of the Sela landslide from 2018 to 2020. Deformation time series characteristics of typical points are analyzed. The results show that the cumulative deformation in the east-west direction of Sala landslide reached a maximum of 165 mm, and the cumulative deformation in the vertical direction reached −102 mm from January 2018 to April 2020. We studied the deformation trend of the landslide, and the accuracy of the landslide monitoring results was verified by the field survey results.
The Jinshajiang suture zone is a high-incidence area of landslide disasters and has a greater threat of river jamming. In this paper, the Sela landslide with high risk of blocking rivers was taken as the research object, and the Sentinel-1A/B images were selected and processed by MSBAS InSAR technology to obtain the surface deformation of the landslide. We used the Sentinel-1A/B images from different orbits to obtain the two-dimensional dynamic deformation of the Sela landslide from 2018 to 2020. Deformation time series characteristics of typical points are analyzed. The results show that the cumulative deformation in the east-west direction of Sala landslide reached a maximum of 165 mm, and the cumulative deformation in the vertical direction reached −102 mm from January 2018 to April 2020. We studied the deformation trend of the landslide, and the accuracy of the landslide monitoring results was verified by the field survey results.
Abstract：
Under the background of global warming, glaciers in southern Tibet continue to retreat and glacier lakes continue to expand, resulting in a series of geological disasters. In this paper, based on the object-oriented classification method, the area of glaciers and glacier lakes in Shisha Pangma peak region of South Tibet from 1994 to 2018 were extracted by using band ratio method and NDWI index. The results show that the net glaciers in Shisha Pangma peak region continue to retreat, with an overall rate of (1.28 ± 0.32)%per year, and the expansion rate of the glacier lakes are about (1.88 ±1. 07) %per year. At the same time, glaciers with an area of less than 1 km2 retreat seriously, up to 33.25%. Secondly, the meteorological reanalysis data show that the increase of summer temperature and precipitation may be important reasons for the accelerated retreat of net glaciers in the region, and jointly promote the expansion of glacier lakes, greatly increasing the risk of glacier lakes outburst in the region.
Under the background of global warming, glaciers in southern Tibet continue to retreat and glacier lakes continue to expand, resulting in a series of geological disasters. In this paper, based on the object-oriented classification method, the area of glaciers and glacier lakes in Shisha Pangma peak region of South Tibet from 1994 to 2018 were extracted by using band ratio method and NDWI index. The results show that the net glaciers in Shisha Pangma peak region continue to retreat, with an overall rate of (1.28 ± 0.32)%per year, and the expansion rate of the glacier lakes are about (1.88 ±1. 07) %per year. At the same time, glaciers with an area of less than 1 km2 retreat seriously, up to 33.25%. Secondly, the meteorological reanalysis data show that the increase of summer temperature and precipitation may be important reasons for the accelerated retreat of net glaciers in the region, and jointly promote the expansion of glacier lakes, greatly increasing the risk of glacier lakes outburst in the region.
Abstract：
Moraine dams are widely distributed in high and very high mountainous areas around the world. In order to investigate the breaching process of end-moraine dams and to understand the evolution of the breaches during the breaching process of end-moraine dams, this paper designed in situ experiments for simulating the process of moraine lake overtopping breakage with the Jialongcuo as the prototype. The experimental results show that: (1) According to the phenomenon of the breach process, the moraine dam breach process is divided into four stages: downstream slope scour, “headcut erosion”, undercutting of the outlet and widening of the breach. (2) The upstream lake collapse body excited by the surge will cause the instantaneous flow in the breach to increase several times, thus making the “headcut erosion” process under the conditions of surge and no surge in two forms of undercutting, which is steep hills and slopes. (3) By analyzing the undercut erosion process of the breach, it is found that the undercut erosion process of the breach is mainly influenced by the void ratio and fines content of the dam body, and there is a linear relationship between the erosion rate at the midpoint of the breach and the water flow shear stress, which is consistent with the linear erosion model. Through the analysis found that the erodible coefficient of Jialongcuo end-moraine dam is 0.051, the critical starting stress is 237.64 Pa, compared with the landslide dams, the erodible coefficient is smaller, while the critical shear stress is larger.
Moraine dams are widely distributed in high and very high mountainous areas around the world. In order to investigate the breaching process of end-moraine dams and to understand the evolution of the breaches during the breaching process of end-moraine dams, this paper designed in situ experiments for simulating the process of moraine lake overtopping breakage with the Jialongcuo as the prototype. The experimental results show that: (1) According to the phenomenon of the breach process, the moraine dam breach process is divided into four stages: downstream slope scour, “headcut erosion”, undercutting of the outlet and widening of the breach. (2) The upstream lake collapse body excited by the surge will cause the instantaneous flow in the breach to increase several times, thus making the “headcut erosion” process under the conditions of surge and no surge in two forms of undercutting, which is steep hills and slopes. (3) By analyzing the undercut erosion process of the breach, it is found that the undercut erosion process of the breach is mainly influenced by the void ratio and fines content of the dam body, and there is a linear relationship between the erosion rate at the midpoint of the breach and the water flow shear stress, which is consistent with the linear erosion model. Through the analysis found that the erodible coefficient of Jialongcuo end-moraine dam is 0.051, the critical starting stress is 237.64 Pa, compared with the landslide dams, the erodible coefficient is smaller, while the critical shear stress is larger.
2021, 32(5): 29-39.
DOI: 10.16031/j.cnki.issn.1003-8035.2021.05-04
Abstract：
The upper reaches of Jinsha River are typical high mountain canyon areas with strong terrain cutting and deep valleys. Affected by the Jinsha River fault zone, the slope integrity is poor and the rock mass is fragmented, which makes the mountain landslide prone to occur on both sides of the river. According to the hue, plane shape, deformation sign and microtopography of landslide hazards in remote sensing images, we establish the remote sensing interpretation signs. A total of 87 landslide were identified in Zhimenda-Shigu section of Jinsha River, including 40 large and 47 super-large ones. Based on the characteristics of regional geography and geological environment, we analyse the basic characteristics and spatial distribution of landslide. The landslide in the study area have obvious chain characteristics, including landslide –blocking river disaster chain, collapse – landslide – blocking river disaster chain, landslide – debris flow – blocking river disaster chain. Taking Sela landslide, Wangbuding landslide and Tange landslide as examples, the deformation characteristics and chain characteristics are analyzed in detail based on optical remote sensing technology. From the geographical view, the Jinshajiang fault zone obviously controls the plane distribution of the Zhimenda-Shigu section of the Jinsha River. The neotectonic movement has strong activity, faster strain accumulation and relatively frequent seismic action in the middle and southern sections of the fault zone, which provides a favorable regional geological environment background for the occurrence of river blocking landslide in the favorable slope areas on both sides of the Jinsha River.
The upper reaches of Jinsha River are typical high mountain canyon areas with strong terrain cutting and deep valleys. Affected by the Jinsha River fault zone, the slope integrity is poor and the rock mass is fragmented, which makes the mountain landslide prone to occur on both sides of the river. According to the hue, plane shape, deformation sign and microtopography of landslide hazards in remote sensing images, we establish the remote sensing interpretation signs. A total of 87 landslide were identified in Zhimenda-Shigu section of Jinsha River, including 40 large and 47 super-large ones. Based on the characteristics of regional geography and geological environment, we analyse the basic characteristics and spatial distribution of landslide. The landslide in the study area have obvious chain characteristics, including landslide –blocking river disaster chain, collapse – landslide – blocking river disaster chain, landslide – debris flow – blocking river disaster chain. Taking Sela landslide, Wangbuding landslide and Tange landslide as examples, the deformation characteristics and chain characteristics are analyzed in detail based on optical remote sensing technology. From the geographical view, the Jinshajiang fault zone obviously controls the plane distribution of the Zhimenda-Shigu section of the Jinsha River. The neotectonic movement has strong activity, faster strain accumulation and relatively frequent seismic action in the middle and southern sections of the fault zone, which provides a favorable regional geological environment background for the occurrence of river blocking landslide in the favorable slope areas on both sides of the Jinsha River.
Abstract：
Due to the development of geological structure, frequent seismic activity, strong valley cutting, high steep and narrow bank slope, extremely broken rock mass, there have been many large-scale landslides blocking the Jinshajiang River in history.
Taking the two river blocking events of Baige landslide (October 11, 2018 and November 3, 2018) as an example, this paper uses the multi-phase and Multi-source Satellite remote sensing data sources from December 4, 2009 to October 16, 2020 to analyze the deformation characteristics of the slope before sliding, the accumulation characteristics of the slope after sliding and the residual deformation characteristics of the slope after sliding by means of remote sensing identification and comparative analysis The analysis of telemotional states. According to the multi-stage remote sensing images, the deformation characteristics of Baige landslide are divided into five areas: early sliding deformation stage (2009-2011), stable deformation stage (2011-2015), rapid deformation stage (2015-2017), severe deformation stage (2017-2018) and deformation failure stage (after 2018). According to the deformation and failure characteristics of the landslide, the landslide is divided into sliding source area, scraping area, accumulation area and tensile fracture deformation area. According to the deformation and failure characteristics of the landslide after the second sliding, the landslide is divided into the secondary landslide source area, the secondary landslide accumulation area (weir body), the secondary scraping (accumulation) area, the secondary scraping affected area and the tensile fracture deformation area. Based on the above research results, this paper summarizes and analyzes the chain characteristics of Baige landslide disaster, which provides a reference for the research on the chain characteristics of long range and high position landslide disasters in Jinsha River junction zone.
Abstract：
Scissors peak bank slope is located in the left bank of Wushan gorge in the Three Gorges Reservoir area, with a total length of 2.1 km. Influenced by Shennv peak box anticline in the north and Shennv Xi-Guandukou syncline in the south, the bank slope is steeply sloping bedding rock bank slope. The slope of the bank is 45°～89°, and the whole is a composite landform of steep slope and steep cliff.The quaternary strata exposed on the bank slope are mainly cluvial gravel soil, and the exposed bedrock contains the strata of the 3rd and 4th members of the Triassic daye formation and the 1st to 4th members of the Jialingjiang formation. The strata are diversified.The rock groups are mainly hard rock group composed of carbonate lute of Daye formation and Jialingjiang formation and soft rock group composed of karst breccia of the second member of Jialingjiang formation. The rock mass structure ranges from very thin layer to very thick layer, and the slope topography, stratum, rock group and structure are complex. Within a range of 2.1 km from upstream to downstream of the bank slope, the slope structure changes greatly, the deformation and failure characteristics of the bank slope vary greatly, and the formation mechanism and failure modes differ greatly. According to the different geological conditions and characteristics of the slope, it can be divided into 6 large sections and 6 sub-sections.Based on the characteristics of the macroscopic deformation and failure of the bank slope, the current deformation and failure of the bank slope are summarized into four aspects: "structural cutting and unloading", "local fracturing, sliding", "surface dissolution", and "rock mass deterioration in the subsidence zone", and the failure modes of each section are analyzed from the perspective of the formation mechanism of the bank slope. In addition, this study also analyzed the deterioration characteristics of rock mass in the bank slope above the reservoir water level and the reservoir water level fluctuation area, and proposed four types of rock mass deterioration and failure types from the perspective of rock mass deterioration: progressive release slip along the plane, collapse slip along the weak interlayer, X-type joint slip, and toppling collapse along the plane.
Scissors peak bank slope is located in the left bank of Wushan gorge in the Three Gorges Reservoir area, with a total length of 2.1 km. Influenced by Shennv peak box anticline in the north and Shennv Xi-Guandukou syncline in the south, the bank slope is steeply sloping bedding rock bank slope. The slope of the bank is 45°～89°, and the whole is a composite landform of steep slope and steep cliff.The quaternary strata exposed on the bank slope are mainly cluvial gravel soil, and the exposed bedrock contains the strata of the 3rd and 4th members of the Triassic daye formation and the 1st to 4th members of the Jialingjiang formation. The strata are diversified.The rock groups are mainly hard rock group composed of carbonate lute of Daye formation and Jialingjiang formation and soft rock group composed of karst breccia of the second member of Jialingjiang formation. The rock mass structure ranges from very thin layer to very thick layer, and the slope topography, stratum, rock group and structure are complex. Within a range of 2.1 km from upstream to downstream of the bank slope, the slope structure changes greatly, the deformation and failure characteristics of the bank slope vary greatly, and the formation mechanism and failure modes differ greatly. According to the different geological conditions and characteristics of the slope, it can be divided into 6 large sections and 6 sub-sections.Based on the characteristics of the macroscopic deformation and failure of the bank slope, the current deformation and failure of the bank slope are summarized into four aspects: "structural cutting and unloading", "local fracturing, sliding", "surface dissolution", and "rock mass deterioration in the subsidence zone", and the failure modes of each section are analyzed from the perspective of the formation mechanism of the bank slope. In addition, this study also analyzed the deterioration characteristics of rock mass in the bank slope above the reservoir water level and the reservoir water level fluctuation area, and proposed four types of rock mass deterioration and failure types from the perspective of rock mass deterioration: progressive release slip along the plane, collapse slip along the weak interlayer, X-type joint slip, and toppling collapse along the plane.
2021, 32(5): 62-69.
DOI: 10.16031/j.cnki.issn.1003-8035.2021.05-07
Abstract：
Danxia landform is an area with high incidence of geological disasters in China. The exposed near-horizontal red sandstone and conglomerate steep cliffs are the most important identification elements. Under the internal and external dynamic action of geological structure, including chemical dissolution, physical weathering, gravity and biology, the rock mass of steep cliff is often extremely broken, and the disaster of dangerous rock collapse and slide is particularly prominent, the deformation mode is complex, the destructive power is strong, and because of the complex slope structure, the engineering investigation is difficult. So, with a deformation dangerous rock mountain scenic area as an example, this paper proposes a high-location and steep broken should based on the technology of unmanned aerial vehicle to the exploration of supergene field quickly identify methods for joint, and the accurate grasp the dangerous rock mass on the surface of the control structure on the basis of the spatial distribution characteristics of breakage of dangerous rock is established in Danxia landform high three-dimensional random fracture network model.It is expected to provide theoretical guidance for the stability evaluation and prevention of dangerous rock in the region.
Danxia landform is an area with high incidence of geological disasters in China. The exposed near-horizontal red sandstone and conglomerate steep cliffs are the most important identification elements. Under the internal and external dynamic action of geological structure, including chemical dissolution, physical weathering, gravity and biology, the rock mass of steep cliff is often extremely broken, and the disaster of dangerous rock collapse and slide is particularly prominent, the deformation mode is complex, the destructive power is strong, and because of the complex slope structure, the engineering investigation is difficult. So, with a deformation dangerous rock mountain scenic area as an example, this paper proposes a high-location and steep broken should based on the technology of unmanned aerial vehicle to the exploration of supergene field quickly identify methods for joint, and the accurate grasp the dangerous rock mass on the surface of the control structure on the basis of the spatial distribution characteristics of breakage of dangerous rock is established in Danxia landform high three-dimensional random fracture network model.It is expected to provide theoretical guidance for the stability evaluation and prevention of dangerous rock in the region.
Abstract：
The study area is located in Xiabao Town, Wuxi County, Chongqing City. It belongs to the mountainous area on the edge of the Yudong Basin. It has strong topography, complex geological environment and frequent geological disasters. In order to study the development and distribution of geological hazards and risk zoning in high and steep canyons, this paper selects factors such as elevation, slope, aspect, engineering geological rock group, distance from water system, and distance from folds as the influencing factors for the assessment of geological hazard susceptibility, based on ArcGIS The platform uses the information model to quantitatively evaluate the susceptibility of high-level geological hazards in the high and steep gorge area of Wuxi Ningqiao area. The evaluation model has a high degree of correspondence with the distribution of geological hazards, and the evaluation results have a high degree of credibility. Combined with the vulnerability assessment, the geological disaster risk assessment of the study area was carried out, and finally the geological disaster risk assessment model of the study area was obtained. It provides a scientific basis for the prevention and control of geological disasters in the region, and at the same time has reference significance for the risk assessment of geological disasters and the prevention and control of geological disasters in similar high and steep canyons..
The study area is located in Xiabao Town, Wuxi County, Chongqing City. It belongs to the mountainous area on the edge of the Yudong Basin. It has strong topography, complex geological environment and frequent geological disasters. In order to study the development and distribution of geological hazards and risk zoning in high and steep canyons, this paper selects factors such as elevation, slope, aspect, engineering geological rock group, distance from water system, and distance from folds as the influencing factors for the assessment of geological hazard susceptibility, based on ArcGIS The platform uses the information model to quantitatively evaluate the susceptibility of high-level geological hazards in the high and steep gorge area of Wuxi Ningqiao area. The evaluation model has a high degree of correspondence with the distribution of geological hazards, and the evaluation results have a high degree of credibility. Combined with the vulnerability assessment, the geological disaster risk assessment of the study area was carried out, and finally the geological disaster risk assessment model of the study area was obtained. It provides a scientific basis for the prevention and control of geological disasters in the region, and at the same time has reference significance for the risk assessment of geological disasters and the prevention and control of geological disasters in similar high and steep canyons..
2021, 32(5): 79-85.
DOI: 10.16031/j.cnki.issn.1003-8035.2021.05-09
Abstract：
This paper studied the characteristics of geomorphology, fire behavior, unconsolidated source material volume, runoff and sediment production related to post-fire debris flow formations, field investigation in the burned area and rainfall simulation experiment were adopted to study the post-fire debris flow in Huayanzi gully, Mianning County, Sichuan Province occurred on 4 July 2019. The associated ash layer, water repellency and permeability experiments were also conducted. The results suggest that (1) the runoff charge shows a positive correlation with water repellency in burned area. (2) the sediment yields in severely burned area are conspicuously larger than that in moderate and slight burned areas. (3) the water repellency in burned area is approximately positively correlated with fire severity, while the permeability presents the negative correlation. This study revealed the evolution process of post-fire debris flow, and provided theoretical basis for the prevention and early warning of post-fire debris flows.
This paper studied the characteristics of geomorphology, fire behavior, unconsolidated source material volume, runoff and sediment production related to post-fire debris flow formations, field investigation in the burned area and rainfall simulation experiment were adopted to study the post-fire debris flow in Huayanzi gully, Mianning County, Sichuan Province occurred on 4 July 2019. The associated ash layer, water repellency and permeability experiments were also conducted. The results suggest that (1) the runoff charge shows a positive correlation with water repellency in burned area. (2) the sediment yields in severely burned area are conspicuously larger than that in moderate and slight burned areas. (3) the water repellency in burned area is approximately positively correlated with fire severity, while the permeability presents the negative correlation. This study revealed the evolution process of post-fire debris flow, and provided theoretical basis for the prevention and early warning of post-fire debris flows.
2021, 32(5): 86-91.
DOI: 10.16031/j.cnki.issn.1003-8035.2021.05-10
Abstract：
Tracing erosion is the strongest dynamic geological action in loess hilly areas. It often causes the head of the ditch to retreat and the toe of the slope to be eroded, which in turn leads to collapse. Based on the statistical analysis of collapse disasters in the study area, this paper determines that the typical type of collapse caused by the traceable erosion effect is tension-toppling type. This type of collapse is characterized by steep back wall, rough wall, large scale, widespread, wide damaging range, and high potential risk. The formation of this type of collapse is mainly due to the transformation of the three areas in horizontal direction such as the tensile stress distribution area, the shear stress distribution area and the strong hydraulic erosion area under the action of surface water erosion and gravity. the collapse of slope undergone three stages: the increase and scope expansion of the tensile stress, the change of the shear stress state and the concentration of the scope, and the collapse of the collapsed body under the coupling action of the slope top tension and pore water pressure. The stability analysis can be carried out by the moment balance method. The three factors that affect the stability of the tension-toppling loess collapse include: slope geometric characteristics, soil physical and mechanical parameters and water pressure in the cracks. Theoretical analysis illustrates that with the increase of soil moisture content, the depth of tensile cracks on the top of the slope deepens, the depth of erosion grooves deepens, and the collapse stability coefficient gradually decreases.
Tracing erosion is the strongest dynamic geological action in loess hilly areas. It often causes the head of the ditch to retreat and the toe of the slope to be eroded, which in turn leads to collapse. Based on the statistical analysis of collapse disasters in the study area, this paper determines that the typical type of collapse caused by the traceable erosion effect is tension-toppling type. This type of collapse is characterized by steep back wall, rough wall, large scale, widespread, wide damaging range, and high potential risk. The formation of this type of collapse is mainly due to the transformation of the three areas in horizontal direction such as the tensile stress distribution area, the shear stress distribution area and the strong hydraulic erosion area under the action of surface water erosion and gravity. the collapse of slope undergone three stages: the increase and scope expansion of the tensile stress, the change of the shear stress state and the concentration of the scope, and the collapse of the collapsed body under the coupling action of the slope top tension and pore water pressure. The stability analysis can be carried out by the moment balance method. The three factors that affect the stability of the tension-toppling loess collapse include: slope geometric characteristics, soil physical and mechanical parameters and water pressure in the cracks. Theoretical analysis illustrates that with the increase of soil moisture content, the depth of tensile cracks on the top of the slope deepens, the depth of erosion grooves deepens, and the collapse stability coefficient gradually decreases.
2021, 32(5): 92-97.
DOI: 10.16031/j.cnki.issn.1003-8035.2021.05-11
Abstract：
The granite residual soil in southeast coast area is selected as the representative soil sample and the simulation test schemes of rainfall triggered landslide are designed with the slope gradient and the rainfall intensity as their control variables. Then the heavy rainfall simulation experiment of slope models with four different gradients are performed under four kinds of different conditions, i.e. heavy rain, rainstorm, heavy rainstorm, extreme rainstorm, and the influence characteristics of rainfall intensity and slope gradient on slope slumping destruction are studied. The results show that the greater rainfall intensity is, the larger the slide block size of collapse is and the more concentrated the scope of damage is, while more obvious the trend of deep or shallow overall damage of slope. In addition, the extent of slope damage is enhanced and the less time needed for soil cracks appear and slope slumping destruction at the same time. With the slope gradient increases, the failure modes of slope gradually become scattered collapse from landslide sliding and the rainfall duration of slope sliding damage is reduced. The research results have important theoretical and practical significance for disclosing the rule of residual soil landslides and other geological disasters triggered by heavy rainfall.
The granite residual soil in southeast coast area is selected as the representative soil sample and the simulation test schemes of rainfall triggered landslide are designed with the slope gradient and the rainfall intensity as their control variables. Then the heavy rainfall simulation experiment of slope models with four different gradients are performed under four kinds of different conditions, i.e. heavy rain, rainstorm, heavy rainstorm, extreme rainstorm, and the influence characteristics of rainfall intensity and slope gradient on slope slumping destruction are studied. The results show that the greater rainfall intensity is, the larger the slide block size of collapse is and the more concentrated the scope of damage is, while more obvious the trend of deep or shallow overall damage of slope. In addition, the extent of slope damage is enhanced and the less time needed for soil cracks appear and slope slumping destruction at the same time. With the slope gradient increases, the failure modes of slope gradually become scattered collapse from landslide sliding and the rainfall duration of slope sliding damage is reduced. The research results have important theoretical and practical significance for disclosing the rule of residual soil landslides and other geological disasters triggered by heavy rainfall.
Abstract：
The extremely difficult area has the characteristics of extremely rugged terrain, complex geographical environment and sparse permanent scatterers. Therefore, an improved SBAS-InSAR technology is designed to monitor the surface deformation. In this paper, the candidate permanent scatterers are obtained from the coherence, amplitude dispersion index and deformation rate, and then the final permanent scatterers are selected by optical images, which are introduced into the SBAS-InSAR calculation process as orbit refining control points, and finally the surface deformation monitoring in the study area is completed. By comparing and analyzing the conventional PS-InSAR technology and SBAS-InSAR technology, the technology has good application value in extremely difficult areas.
The extremely difficult area has the characteristics of extremely rugged terrain, complex geographical environment and sparse permanent scatterers. Therefore, an improved SBAS-InSAR technology is designed to monitor the surface deformation. In this paper, the candidate permanent scatterers are obtained from the coherence, amplitude dispersion index and deformation rate, and then the final permanent scatterers are selected by optical images, which are introduced into the SBAS-InSAR calculation process as orbit refining control points, and finally the surface deformation monitoring in the study area is completed. By comparing and analyzing the conventional PS-InSAR technology and SBAS-InSAR technology, the technology has good application value in extremely difficult areas.
Abstract：
In this paper, the Jianchuandong dangerous rock mass in the Three Gorges Reservoir area is taken as an example to study the failure mode and protection of submerged thick-layer dangerous rock mass. Based on field investigation and the monitoring data, it was found that the degradation of the base rock mass under the dry-wet cycles is the main factor to accelerate the deformation of the dangerous rock mass. Its failure mode is determined as slip collapse. According to the deformation and failure characteristics of the dangerous rock mass, the corresponding treatment measure is divided into two parts, inculding the reinforcement of the weak base rock mass, and anchor cable in the upper part of the dangerous rock mass. By comparing the displacement field and the stress field before and after protection, it is found that the prestressed reinforcement of the upper dangerous rock mass can effectively control the deformation of the rock mass, and the reinforcement of base rock mass can effectively control the maximum shear stress of the dangerous rock mass. The comprehensive protection effect is significant to ensure the stability of dangerous rock mass. The protection method can provide important reference for the treatment of submerged dangerous rock mass in the reservoir area.
In this paper, the Jianchuandong dangerous rock mass in the Three Gorges Reservoir area is taken as an example to study the failure mode and protection of submerged thick-layer dangerous rock mass. Based on field investigation and the monitoring data, it was found that the degradation of the base rock mass under the dry-wet cycles is the main factor to accelerate the deformation of the dangerous rock mass. Its failure mode is determined as slip collapse. According to the deformation and failure characteristics of the dangerous rock mass, the corresponding treatment measure is divided into two parts, inculding the reinforcement of the weak base rock mass, and anchor cable in the upper part of the dangerous rock mass. By comparing the displacement field and the stress field before and after protection, it is found that the prestressed reinforcement of the upper dangerous rock mass can effectively control the deformation of the rock mass, and the reinforcement of base rock mass can effectively control the maximum shear stress of the dangerous rock mass. The comprehensive protection effect is significant to ensure the stability of dangerous rock mass. The protection method can provide important reference for the treatment of submerged dangerous rock mass in the reservoir area.
2021, 32(5): 113-120.
DOI: 10.16031/j.cnki.issn.1003-8035.2021.05-14
Abstract：
Geological disasters in mining areas have become more and more serious in recent years. For accurate monitoring of surface subsidence with complex topography of tailings dam, based on the monitoring data of UAV(Unmanned Aerial Vehicle) low-altitude photogrammetry, the UAV original POS(Position and Orientation System) data error were improved, data from the error correction model was used to correct the original POS model and 7 kinds of control point layout were designed, high resolution evaluation was conducted on the orthogonal projection as well as the DEM(Digital Elevation Model) accuracy. The results show that when the number of image control points is 8, the data error can be controlled within 3 mm. The settlement map of the mining dam is generated by overlaying the ground model with the difference values of the two DEM data, and the profiles with Y=350 m, Y=100 m and X=60 m were made respectively. The measurement results indicated that the tailing dam has been subsided as a whole, and the southern mining dam has the largest subsidence area, which is within 0.16 m. This application verifies that the accuracy of UAV low altitude photogrammetry in mining dam surface monitoring is reliable. The high-precision mapping method of UAV is used to monitor the deformation of tailing dam, which plays a certain early warning role in the ecological disaster terrain of the oasis area and the surrounding rivers and lakes which may be caused by the emergency response of dam break and the safe production of mining area.
Geological disasters in mining areas have become more and more serious in recent years. For accurate monitoring of surface subsidence with complex topography of tailings dam, based on the monitoring data of UAV(Unmanned Aerial Vehicle) low-altitude photogrammetry, the UAV original POS(Position and Orientation System) data error were improved, data from the error correction model was used to correct the original POS model and 7 kinds of control point layout were designed, high resolution evaluation was conducted on the orthogonal projection as well as the DEM(Digital Elevation Model) accuracy. The results show that when the number of image control points is 8, the data error can be controlled within 3 mm. The settlement map of the mining dam is generated by overlaying the ground model with the difference values of the two DEM data, and the profiles with Y=350 m, Y=100 m and X=60 m were made respectively. The measurement results indicated that the tailing dam has been subsided as a whole, and the southern mining dam has the largest subsidence area, which is within 0.16 m. This application verifies that the accuracy of UAV low altitude photogrammetry in mining dam surface monitoring is reliable. The high-precision mapping method of UAV is used to monitor the deformation of tailing dam, which plays a certain early warning role in the ecological disaster terrain of the oasis area and the surrounding rivers and lakes which may be caused by the emergency response of dam break and the safe production of mining area.
2021, 32(5): 121-129.
DOI: 10.16031/j.cnki.issn.1003-8035.2021.05-15
Abstract：
Focus on theslope geological hazard of Xiangli expressway, systematic study was carried out to find the main types, development characteristics and distribution of slope geological hazards on the basis of detailed road engineering survey.A complete information evaluation index of linear engineering of expressway, including basic geological conditions, natural induced factors, human engineering activities and historical records of slope disasters, was put forward. The susceptibility evaluation model of slope geological hazards of linear engineering was established through the combination of Analytic Hierarchy Process (AHP), expert investigation method and factor accumulation method. The susceptibility zoning of the slope geological hazards in Xiangli expressway was completed, in terms of the GIS platform, which provided an important basis for the risk evaluation and scientific prevention of geological hazards in Xiangli expressway.This paper plays a certain demonstration role and provides reference for the research and practice of slope geological hazard assessment of linear engineering such as mountainious roads.
Focus on theslope geological hazard of Xiangli expressway, systematic study was carried out to find the main types, development characteristics and distribution of slope geological hazards on the basis of detailed road engineering survey.A complete information evaluation index of linear engineering of expressway, including basic geological conditions, natural induced factors, human engineering activities and historical records of slope disasters, was put forward. The susceptibility evaluation model of slope geological hazards of linear engineering was established through the combination of Analytic Hierarchy Process (AHP), expert investigation method and factor accumulation method. The susceptibility zoning of the slope geological hazards in Xiangli expressway was completed, in terms of the GIS platform, which provided an important basis for the risk evaluation and scientific prevention of geological hazards in Xiangli expressway.This paper plays a certain demonstration role and provides reference for the research and practice of slope geological hazard assessment of linear engineering such as mountainious roads.
2021, 32(5): 130-136.
DOI: 10.16031/j.cnki.issn.1003-8035.2021.05-16
Abstract：
Gansu section of the Yellow River basin is the most concentrated area of geological disasters in Gansu Province. By the end of 2019, 12829 potential geological hazard points have been identified, accounting for 70.83% of the total number of disasters in Gansu Province. According to the distribution characteristics of water system, Weihe River basin, Jinghe River basin and the Yellow River basin are the most developed, followed by other water systems. According to the spatial distribution characteristics, it can be divided into three sections: the northern Yongdeng—Jingyuan debris flow area, the central and northern landslide debris flow concentrated section, the central and southern collapse landslide debris flow section, and the southern Maqu—Luqu geological disaster development section. In terms of time distribution, there are two high frequency periods: freezing and thawing period from February to May and main flood season from July to September. Geological disasters have the characteristics of small disaster and huge loss, mass damage and chain type huge loss. Single disaster is easy to form huge loss. The mass geological disaster caused by rainfall and earthquake often causes huge loss. At the same time, the risk of dammed lake formed by landslide flow blocking river channel often occurs.
Gansu section of the Yellow River basin is the most concentrated area of geological disasters in Gansu Province. By the end of 2019, 12829 potential geological hazard points have been identified, accounting for 70.83% of the total number of disasters in Gansu Province. According to the distribution characteristics of water system, Weihe River basin, Jinghe River basin and the Yellow River basin are the most developed, followed by other water systems. According to the spatial distribution characteristics, it can be divided into three sections: the northern Yongdeng—Jingyuan debris flow area, the central and northern landslide debris flow concentrated section, the central and southern collapse landslide debris flow section, and the southern Maqu—Luqu geological disaster development section. In terms of time distribution, there are two high frequency periods: freezing and thawing period from February to May and main flood season from July to September. Geological disasters have the characteristics of small disaster and huge loss, mass damage and chain type huge loss. Single disaster is easy to form huge loss. The mass geological disaster caused by rainfall and earthquake often causes huge loss. At the same time, the risk of dammed lake formed by landslide flow blocking river channel often occurs.
Abstract：
The study of landslide susceptibility evaluation is of great significance to both zoning of geological disasters and disaster prevention strategies. Taking Wenchuan and two surrounding counties (Li County and Mao County), which are prone to landslides, as an example, K-means cluster information model for landslide susceptibility mapping is proposed. After seven impact factors, i.e., slope angle, elevation, aspect, distance from the structure, distance from the water system, formation lithology and the land usage, are selected, the secondary classification for factors is carried out. The former five impact factors mentioned above were classified separately by K-means cluster analysis according to 159 landslide samples. At the sametime, the traditional isometric classification was also presented to compare with the K-means clustering method. The latter two impact factors were classified qualitatively. According to the differences of the above secondary classification methods and whether the landslide sample considers the area factor, the information model is subdivided into four categories (model a: K-means clustering quantitative model, model b: isometric classification quantitative model, model c: K-means clustering area model, and model d: isometric classification area model). The information of each secondary index was calculated separately, and the information distribution of the study area was obtained through spatial overlay analysis of ArcGIS. Then, the landslide susceptibility of the study area was divided into five grades by natural breakpoint method. Taking the principle of increasing susceptibility and Area Under Curve (AUC) as the accuracy evaluation indicators, three results were obtained. First, the overall effect of K-means clustering models (model a and model c) is better than that of isometric classification models (model b and model d). Second, the area models (model c and model d) are generally better than the quantitative models (model a and model b) under the same classification method. Third, With the above two advantages, the evaluation accuracy of model c is significantly improved compared with model b, and its AUC value is increased from 80.46% to 87.25%.
The study of landslide susceptibility evaluation is of great significance to both zoning of geological disasters and disaster prevention strategies. Taking Wenchuan and two surrounding counties (Li County and Mao County), which are prone to landslides, as an example, K-means cluster information model for landslide susceptibility mapping is proposed. After seven impact factors, i.e., slope angle, elevation, aspect, distance from the structure, distance from the water system, formation lithology and the land usage, are selected, the secondary classification for factors is carried out. The former five impact factors mentioned above were classified separately by K-means cluster analysis according to 159 landslide samples. At the sametime, the traditional isometric classification was also presented to compare with the K-means clustering method. The latter two impact factors were classified qualitatively. According to the differences of the above secondary classification methods and whether the landslide sample considers the area factor, the information model is subdivided into four categories (model a: K-means clustering quantitative model, model b: isometric classification quantitative model, model c: K-means clustering area model, and model d: isometric classification area model). The information of each secondary index was calculated separately, and the information distribution of the study area was obtained through spatial overlay analysis of ArcGIS. Then, the landslide susceptibility of the study area was divided into five grades by natural breakpoint method. Taking the principle of increasing susceptibility and Area Under Curve (AUC) as the accuracy evaluation indicators, three results were obtained. First, the overall effect of K-means clustering models (model a and model c) is better than that of isometric classification models (model b and model d). Second, the area models (model c and model d) are generally better than the quantitative models (model a and model b) under the same classification method. Third, With the above two advantages, the evaluation accuracy of model c is significantly improved compared with model b, and its AUC value is increased from 80.46% to 87.25%.
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