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2
Abstract：
Check dams play a pivotal role in debris flow prevention and control engineering. However, their disaster prevention and mitigation capacity gradually decrease over service time due to repeated debris flow impacts. The study was carried out in 15 ditches and 55 check dams within Wudu District, Longnan City, Gansu Province. Seven key evaluation factors were selected for effectiveness and safety: reservoir siltation ratio, slope stability, drainage hole blockage, dam body damage, dam foundation damage, dam shoulder damage, and safety. The evaluation model of the serviceability of the indivusual dam and the comprehensive serviceability of the single trench of the barrage was established by using hierarchical analysis and fuzzy comprehensive evaluation method, and the serviceability was divided into four grades: excellent, good, medium and poor. The evaluation results show that the serviceability rating of individual dams is predominately "poor", accounting for 34.5%. Similarly, the collective serviceability rating of single trench dams for debris flow is predominately "poor", at 33.3%. The results of the evaluation are consistent with the fieldwork observations, providing a valuable reference for predicting the service performance and service life of barrage dams.
Check dams play a pivotal role in debris flow prevention and control engineering. However, their disaster prevention and mitigation capacity gradually decrease over service time due to repeated debris flow impacts. The study was carried out in 15 ditches and 55 check dams within Wudu District, Longnan City, Gansu Province. Seven key evaluation factors were selected for effectiveness and safety: reservoir siltation ratio, slope stability, drainage hole blockage, dam body damage, dam foundation damage, dam shoulder damage, and safety. The evaluation model of the serviceability of the indivusual dam and the comprehensive serviceability of the single trench of the barrage was established by using hierarchical analysis and fuzzy comprehensive evaluation method, and the serviceability was divided into four grades: excellent, good, medium and poor. The evaluation results show that the serviceability rating of individual dams is predominately "poor", accounting for 34.5%. Similarly, the collective serviceability rating of single trench dams for debris flow is predominately "poor", at 33.3%. The results of the evaluation are consistent with the fieldwork observations, providing a valuable reference for predicting the service performance and service life of barrage dams.
4
2023, 34(2): 53-60.
DOI: 10.16031/j.cnki.issn.1003-8035.202202041
Abstract：
Tianjin has a long history of land subsidence, which has gone through six different stages since 1923. Although as of 2020, the land subsidence in a large area of Tianjin has been mostly controlled, there are still serious subsidence areas with an annual subsidence of over 50mm. From large-scale treatment to precise prevention and control of small areas, the distribution characteristics of ground subsidence in Tianjin have shown a new situation, and the prevention and control of land subsidence is also facing new requirements. To accurately grasp the development law of ground subsidence and implement precise policies under the new situation, this paper summarizes the distribution characteristics and evolution rules of severe land subsidence areas in Tianjin by collecting and analyzing the data of ground subsidence leveling, groundwater level, and groundwater extraction in Tianjin from 2010 to 2020. The results show that the land subsidence of Tianjin has experienced three periods during the ten years from 2010 to 2020: a fluctuation period in subsidence from 2010 to 2012, a steady improvement period from 2013 to 2016, and a rapid slowdown period from 2017 to 2020. During these periods, the average amount of land subsidence dropped by 37%, and the area of severe subsidence decreased by 67%. The changes in subsidence were closely related to the amount of groundwater extraction. As of 2020, five severe subsidence areas are concentrated in the southwest of Tianjin, with a distribution range that is similar to the groundwater funnel of the deep water-bearing group.
Tianjin has a long history of land subsidence, which has gone through six different stages since 1923. Although as of 2020, the land subsidence in a large area of Tianjin has been mostly controlled, there are still serious subsidence areas with an annual subsidence of over 50mm. From large-scale treatment to precise prevention and control of small areas, the distribution characteristics of ground subsidence in Tianjin have shown a new situation, and the prevention and control of land subsidence is also facing new requirements. To accurately grasp the development law of ground subsidence and implement precise policies under the new situation, this paper summarizes the distribution characteristics and evolution rules of severe land subsidence areas in Tianjin by collecting and analyzing the data of ground subsidence leveling, groundwater level, and groundwater extraction in Tianjin from 2010 to 2020. The results show that the land subsidence of Tianjin has experienced three periods during the ten years from 2010 to 2020: a fluctuation period in subsidence from 2010 to 2012, a steady improvement period from 2013 to 2016, and a rapid slowdown period from 2017 to 2020. During these periods, the average amount of land subsidence dropped by 37%, and the area of severe subsidence decreased by 67%. The changes in subsidence were closely related to the amount of groundwater extraction. As of 2020, five severe subsidence areas are concentrated in the southwest of Tianjin, with a distribution range that is similar to the groundwater funnel of the deep water-bearing group.
5
Abstract：
Building sites are created by leveling hills and creating land in the hilly mountainous areas of collapsible loess. The deformation characteristics of the high slopes of excavation and filling and the internal properties of the soil at the exposed position of the boundary line are the key aspect of slope stability evaluation. To investigate the stability of the collapsible loess high slope for the Tongxin Miaoling transformer station from the important hub of the West-East power transmission project, this study conducted field detection tests using professional ground-penetrating radar (GPR) of model pulseEKKO PRO, Survey lines with lengths of 416 m and 372 m were laid at the top of the slope in the excavation area and the fill area. Meanwhile, survey lines of 15 m and 20 m in length were laid on both sides of the excavation and filling boundary. GPR is used to carry out detection work on all survey lines at 0.5 m intervals. The results show that the wave spectrum characteristics image of the high excavation slope is consistent with the soil distribution at the same location in the geological survey results. Meanwhile, its reflected wave is messier, which indicates that there are unloading cracks and sporadic fracture zones inside the slope. There is no abnormal reflective wave surface such as cracks and local subsidence on the high fill slope, and its filling soil is uniform. The original soil in the high fill slope area is self-weight collapsing loess, thus the soil of the high fill slope has potential risks. The boundary area of excavation and filling has a more obvious boundary line of excavation and filling, which has a slow slope and uniform transition. The detection waveform on the side of the boundary line is complex, with many types of lithology, and high soil compactness, while the right side has regular waveforms, single soil properties, low soil compactness, and differences in soil properties between excavation and filling.easily lead to unenen settlement. These results could provide a reference for the design and construction of the high side slope of the cutting hills to the backfill ditch project.
Building sites are created by leveling hills and creating land in the hilly mountainous areas of collapsible loess. The deformation characteristics of the high slopes of excavation and filling and the internal properties of the soil at the exposed position of the boundary line are the key aspect of slope stability evaluation. To investigate the stability of the collapsible loess high slope for the Tongxin Miaoling transformer station from the important hub of the West-East power transmission project, this study conducted field detection tests using professional ground-penetrating radar (GPR) of model pulseEKKO PRO, Survey lines with lengths of 416 m and 372 m were laid at the top of the slope in the excavation area and the fill area. Meanwhile, survey lines of 15 m and 20 m in length were laid on both sides of the excavation and filling boundary. GPR is used to carry out detection work on all survey lines at 0.5 m intervals. The results show that the wave spectrum characteristics image of the high excavation slope is consistent with the soil distribution at the same location in the geological survey results. Meanwhile, its reflected wave is messier, which indicates that there are unloading cracks and sporadic fracture zones inside the slope. There is no abnormal reflective wave surface such as cracks and local subsidence on the high fill slope, and its filling soil is uniform. The original soil in the high fill slope area is self-weight collapsing loess, thus the soil of the high fill slope has potential risks. The boundary area of excavation and filling has a more obvious boundary line of excavation and filling, which has a slow slope and uniform transition. The detection waveform on the side of the boundary line is complex, with many types of lithology, and high soil compactness, while the right side has regular waveforms, single soil properties, low soil compactness, and differences in soil properties between excavation and filling.easily lead to unenen settlement. These results could provide a reference for the design and construction of the high side slope of the cutting hills to the backfill ditch project.
9
2023, 34(2): 11-20.
DOI: 10.16031/j.cnki.issn.1003-8035.202201006
Abstract：
At 7:50 on April 29, 2015, a large-scale landslide occurred in Heifangtai, Yongjing County, Gansu Province, with a landslide volume of 126.88 × 104 m3, destroying 14 houses and three factories, resulting in a direct economic loss of 54.6 million yuan. Based on a large number of geological investigations on the disaster site, combined with comprehensive investigation means such as remote sensing, three-dimensional laser scanning and on-site video monitoring data, this paper evolution and sliding characteristics of Luojiapo landslide in detail, and analyzes the high-speed remote mechanism of the landslide. The results show that Luojiapo landslide has gone through five stages and five sliding forms from the timeline: loess staggered debris flow, loess mudstone debris flow, loess debris flow, loess mudflow and loess staggered sliding. The landslide movement mode can be divided into two types: block debris flow and loess mud flow. The high-speed and long-distance formation mechanism of block debris flow is closely related to the “concave bed filling effect” of the previous landslide and the underlying surface soil with high water content. The research results have positive guiding significance for further deepening the understanding of the formation mechanism and risk control of high-speed and long-distance landslides in the Heifangtai area.
At 7:50 on April 29, 2015, a large-scale landslide occurred in Heifangtai, Yongjing County, Gansu Province, with a landslide volume of 126.88 × 104 m3, destroying 14 houses and three factories, resulting in a direct economic loss of 54.6 million yuan. Based on a large number of geological investigations on the disaster site, combined with comprehensive investigation means such as remote sensing, three-dimensional laser scanning and on-site video monitoring data, this paper evolution and sliding characteristics of Luojiapo landslide in detail, and analyzes the high-speed remote mechanism of the landslide. The results show that Luojiapo landslide has gone through five stages and five sliding forms from the timeline: loess staggered debris flow, loess mudstone debris flow, loess debris flow, loess mudflow and loess staggered sliding. The landslide movement mode can be divided into two types: block debris flow and loess mud flow. The high-speed and long-distance formation mechanism of block debris flow is closely related to the “concave bed filling effect” of the previous landslide and the underlying surface soil with high water content. The research results have positive guiding significance for further deepening the understanding of the formation mechanism and risk control of high-speed and long-distance landslides in the Heifangtai area.
10
2023, 34(2): 156-166.
DOI: 10.16031/j.cnki.issn.1003-8035.202112035
Abstract：
There are a large number of rock landslide disasters developed in the first section of the Three Gorges Reservoir area, many of which are very hidden and have not been identified. In this paper, taking the left bank of Xietan River in the first section of the Three Gorges Reservoir as the study area, taking the only bedding rock landslide in Kamenziwan as an example, the failure mode of bedding rock landslide in this area is summarized on the basis of analyzing its genesis mechanism. Nine evaluation index factors, including elevation, slope aspect, slope, relief, plane curvature, profile curvature, formation lithology, distance from river and distance from road, as well as suspected hidden danger points of landslide disaster are determined. These hidden danger points are taken as landslide samples. Automatic Landside Susceptibility Assessment Model (ALSA) was used to carry out landslide Susceptibility zoning in the study area. Finally, ROC curve and field review were used to verify the reliability of the evaluation results. The prediction results show that the extremely high and highly prone areas of bedding rock landslides in the study area are distributed in a plane shape, mainly concentrated in the middle Jurassic Upper Shaximiao Formation purplish red mudstone intercalated sandstone, and the northwest slope direction near the reservoir bank area. Field verification shows that the results of prone zoning are consistent with the distribution law of landslide failure mode, indicating that the landslide susceptibility results obtained by selecting landslide samples based on landslide failure mode can also reflect the spatial distribution law of landslide probability in the study area on the whole, and can be used as a substitute scheme in the absence of accurate landslide samples. The above research results provide theoretical support and scientific basis for selecting landslide samples to carry out vulnerability assessment based on landslide failure mode.
There are a large number of rock landslide disasters developed in the first section of the Three Gorges Reservoir area, many of which are very hidden and have not been identified. In this paper, taking the left bank of Xietan River in the first section of the Three Gorges Reservoir as the study area, taking the only bedding rock landslide in Kamenziwan as an example, the failure mode of bedding rock landslide in this area is summarized on the basis of analyzing its genesis mechanism. Nine evaluation index factors, including elevation, slope aspect, slope, relief, plane curvature, profile curvature, formation lithology, distance from river and distance from road, as well as suspected hidden danger points of landslide disaster are determined. These hidden danger points are taken as landslide samples. Automatic Landside Susceptibility Assessment Model (ALSA) was used to carry out landslide Susceptibility zoning in the study area. Finally, ROC curve and field review were used to verify the reliability of the evaluation results. The prediction results show that the extremely high and highly prone areas of bedding rock landslides in the study area are distributed in a plane shape, mainly concentrated in the middle Jurassic Upper Shaximiao Formation purplish red mudstone intercalated sandstone, and the northwest slope direction near the reservoir bank area. Field verification shows that the results of prone zoning are consistent with the distribution law of landslide failure mode, indicating that the landslide susceptibility results obtained by selecting landslide samples based on landslide failure mode can also reflect the spatial distribution law of landslide probability in the study area on the whole, and can be used as a substitute scheme in the absence of accurate landslide samples. The above research results provide theoretical support and scientific basis for selecting landslide samples to carry out vulnerability assessment based on landslide failure mode.
11
2023, 34(5): 32-42.
DOI: 10.16031/j.cnki.issn.1003-8035.202302030
Abstract：
This study focuses on Dege County as the research area, and carries out terrain analysis and processing with 7m DEM. A landslide hazard database for Dege County is establishing using relevant survey data. With the support of GIS technology, this research employs the information quantity model (I), analytic hierarchy process model (AHP), and deterministic coefficient model (CF) coupling to evaluate the hazard sensitivity within the study area based on seven selected indicators: mic peak acceleration, fault zone, water system, slope, slope direction, elevation, and lithology. Subsequently, an assessment of hazard is conducted for the entire county domain by considering factors related to landslide activity frequency. The results are categorized into four zones: high risk, relatively high risk, moderate risk, and low risk. The high and relatively high-risk zones collectively cover 2.23% of the total area, with landslides accounting for 42% of the overall hazards. The evaluation results align well with the actual survey findings, providing technical support for predicting, forecasting, and implementing safety measures against landslide disasters in areas that without field investigation. Furthermore, it can serve as a theoretical guide and technical reference for the risk assessment of landslide hazard in other regions.
This study focuses on Dege County as the research area, and carries out terrain analysis and processing with 7m DEM. A landslide hazard database for Dege County is establishing using relevant survey data. With the support of GIS technology, this research employs the information quantity model (I), analytic hierarchy process model (AHP), and deterministic coefficient model (CF) coupling to evaluate the hazard sensitivity within the study area based on seven selected indicators: mic peak acceleration, fault zone, water system, slope, slope direction, elevation, and lithology. Subsequently, an assessment of hazard is conducted for the entire county domain by considering factors related to landslide activity frequency. The results are categorized into four zones: high risk, relatively high risk, moderate risk, and low risk. The high and relatively high-risk zones collectively cover 2.23% of the total area, with landslides accounting for 42% of the overall hazards. The evaluation results align well with the actual survey findings, providing technical support for predicting, forecasting, and implementing safety measures against landslide disasters in areas that without field investigation. Furthermore, it can serve as a theoretical guide and technical reference for the risk assessment of landslide hazard in other regions.
12
Abstract：
Taking the Wapo collapse area in Yuan’an County as an example, a three-dimensional model was established by drone aerial photography, geological survey and field mapping. Based on Rockfall Analyst (RA) analysis software, a large number of three-dimensional rockfalls in the Wapo collapse area were studied. The motion path, height, energy and other factors in the space were simulated to explore the three-dimensional motion characteristics of rockfalls. The risk assessment of rockfalls in the collapsed area was carried out to guide the prevention and control of the rockfalls. The research results showed that the main failure form of the dangerous rock was the toppling, and it was in an under-stable state at present; the three-dimensional motion trajectory of the simulated rockfall basically coincided with the existing rockfall point which indicating the simulation results were in good agreement with the actual situation; The mode of motion of the rocks were collision, bounce and free fall. Rockfalls were mainly concentrated in the gullies and roads but a few rocks reached residential areas. Therefore, the roads, gullies and the right side of the collapse area were in high risk area; Dangerous rock mass and boulders removal and passive protective nets were adopt as the prevention engineering,two passive protection nets which were 5 m high and 3 m high respectively were set on the inner side of the road and below the slope, and a net with an impact resistance of 2 000 kJ could effectively intercept falling rocks.
Taking the Wapo collapse area in Yuan’an County as an example, a three-dimensional model was established by drone aerial photography, geological survey and field mapping. Based on Rockfall Analyst (RA) analysis software, a large number of three-dimensional rockfalls in the Wapo collapse area were studied. The motion path, height, energy and other factors in the space were simulated to explore the three-dimensional motion characteristics of rockfalls. The risk assessment of rockfalls in the collapsed area was carried out to guide the prevention and control of the rockfalls. The research results showed that the main failure form of the dangerous rock was the toppling, and it was in an under-stable state at present; the three-dimensional motion trajectory of the simulated rockfall basically coincided with the existing rockfall point which indicating the simulation results were in good agreement with the actual situation; The mode of motion of the rocks were collision, bounce and free fall. Rockfalls were mainly concentrated in the gullies and roads but a few rocks reached residential areas. Therefore, the roads, gullies and the right side of the collapse area were in high risk area; Dangerous rock mass and boulders removal and passive protective nets were adopt as the prevention engineering,two passive protection nets which were 5 m high and 3 m high respectively were set on the inner side of the road and below the slope, and a net with an impact resistance of 2 000 kJ could effectively intercept falling rocks.
13
Abstract：
Pingshan County, Hebei was affected by topography, geological structure, ecological environment and other factors, geological disasters such as landslides occurred frequently. Nine evaluation factors including topographic relief, slope, aspect, river network density, fault zone density, stratigraphic lithology, NDVI, land use type and geological disaster point density were selected. The weights of each evaluation factor were calculated by AHP and catastrophe theory, and the combination model of AHP and catastrophe theory was established and applied according to the minimum information entropy weight method. The results of geological disaster risk assessment in Pingshan County based on three methods were compared. The results show that the evaluation results of the combined model have higher accuracy and are in line with the development characteristics of geological disasters in this area. Combined model method combines subjective and objective, considering the influence of factors, the evaluation results are reliable. This study provides a new attempt and method for geological disaster risk assessment in Pingshan County and similar areas.
14
Abstract：
In order to study the slope deformation law during and after the construction of the sandstone bed-cut high slope support project and the effect of the treatment project, this paper relies on a slope support project in Beijing to analyze the axial force of the anchor cable and the slope during the construction process. The slope displacement is monitored and analyzed, and the results show that the change of the axial force of the anchor cable is mainly divided into the acceleration loss stage, the fluctuation stage and the continuous stable trend stage; the change of the axial force of the anchor cable can well reflect the change of the internal force of the slope; the change of horizontal displacement and vertical settlement can reflect the change law of the deep displacement of the slope and the stability of the slope, has a better support effect. The finite element analysis software was used to simulate the excavation and support process of the sandstone-layered high slope. It was found that with the excavation of the slope, the displacement of the slope developed along the slope angle of the weak sliding surface, and the stability of the slope decreased. The monitoring results and the simulation results are compared and analyzed, and it is found that the change trends of the two are basically the same, which proves that the slope support system can effectively control the deformation of the slope. The research results can provide reference for the design and construction of similar slopes in the future.
In order to study the slope deformation law during and after the construction of the sandstone bed-cut high slope support project and the effect of the treatment project, this paper relies on a slope support project in Beijing to analyze the axial force of the anchor cable and the slope during the construction process. The slope displacement is monitored and analyzed, and the results show that the change of the axial force of the anchor cable is mainly divided into the acceleration loss stage, the fluctuation stage and the continuous stable trend stage; the change of the axial force of the anchor cable can well reflect the change of the internal force of the slope; the change of horizontal displacement and vertical settlement can reflect the change law of the deep displacement of the slope and the stability of the slope, has a better support effect. The finite element analysis software was used to simulate the excavation and support process of the sandstone-layered high slope. It was found that with the excavation of the slope, the displacement of the slope developed along the slope angle of the weak sliding surface, and the stability of the slope decreased. The monitoring results and the simulation results are compared and analyzed, and it is found that the change trends of the two are basically the same, which proves that the slope support system can effectively control the deformation of the slope. The research results can provide reference for the design and construction of similar slopes in the future.
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