Investigation And Stability Evaluation Of Slope Toe Excavation In Rural Areas Of Loess District

The basic engineering of our country is in the process of constant development,the number of artificial slope produced by human activities also gradually increase with the development of the foundation engineering,slope rock and soil under the disturbance of human activities of the collapse,landslide and other kinds of geological disasters will bring unimaginable loss to people’s life and property safety.With the implementation of various strategies such as poverty alleviation and rural revitalization,more and more attention has been paid to the quality of life and production of rural residents.The country is also making efforts to improve the living environment and living conditions of rural residents.Housing as the basis of rural residents’ life,the safety of housing and the rationality of building is particularly important.At the present stage,the geological conditions in most rural areas are more complex than those in cities,and land use control is not well perfected and implemented.In the process of building construction,many villagers choose to excavate slopes to increase the building area,and the resulting high and steep artificial slopes bury hidden dangers to the occurrence of geological disasters such as landslides.It is a threat to villagers’ life and property safety.Based on the geological hazard risk investigation project in Jingyuan County,Gansu Province,this paper conducts statistical analysis of geological hazards in the county,classifies landslide and collapse hazard points in the area by different factors,and evaluates the stability of landslide and collapse hazard points in the field according to field investigation specifications;The actual investigation found that most of the landslide and collapse disaster points were caused by human building activities.Therefore,417 slope cutting and building sites were taken as the research object,and local engineering geological data were obtained through comprehensive on-site investigation,drilling survey,and other means.After that,various parameters of the slope were obtained based on indoor geotechnical tests.Based on the obtained data,slope models under different excavation conditions are established and three-dimensional numerical simulation is conducted using FLAC3 D software to discuss the impact of different excavation conditions and conditions on the stability of the excavation slope.Qualitative analysis is conducted on the impact of various parameters on slope stability after excavation based on field investigation data.Based on the simulation results of various models,the excavation conditions that have the smallest impact on slope instability are analyzed and calculated,and combined with the qualitative analysis results,with a view to providing a feasible excavation and building plan with minimum risk for slope cutting and building engineering activities,reducing the possibility of disasters caused by slope cutting and building,and effectively improving the protection of villagers’ life safety.Through this study,the main results are as follows:(1)Based on the field investigation and statistics of geological disasters in the area,the stability and risk of potential geological hazards such as landslides and collapses in the area were evaluated.The stability of landslides and collapses developed in the area is mainly "relatively stable" and "unstable".According to the investigation and analysis,Jingyuan County has complex topographic and geomorphic conditions,and geological disasters such as landslides,debris flows,and collapses are very developed.(2)For 417 households with slope cutting and building,314 slope cutting and building sites were verified and checked for statistical analysis and stability evaluation of on-site conditions.Qualitative statistical analysis is conducted on the stability of excavation and cutting slopes under the influence of different factors,mainly including excavation width,excavation height,slope after excavation,slope direction,original slope height,and original slope gradient.Statistical analysis is conducted on the percentage of basic stability and instability of each gradient.According to the variation trend,as the excavation width increases,the slope stability after excavation has a slow deterioration trend;With the increase of excavation height,the stability of the slope after excavation has a significant trend of deterioration;With the increase of slope after excavation,the stability of the slope after excavation has a significant trend of deterioration;With the change of slope direction,there is no significant change in the stability of the slope after excavation;As the original slope height increases,the stability of the slope after excavation tends to improve;As the original slope gradient increases,the stability of the slope after excavation has a significant trend of deterioration.(3)Conduct numerical simulation based on various factors divided during slope cutting and house building statistics.The main choices are excavation width,excavation height,slope after excavation,original slope height,and original slope slope for model establishment and numerical simulation.By analyzing the numerical simulation results and mainly comparing the displacement values and stress distribution of the observation points set on the slope after excavation in the calculation results,the following conclusions can be drawn: As the excavation width increases,the local stability of the slope after excavation has a slow deterioration trend;With the increase of excavation height,the local stability of the slope after excavation has a significant trend of deterioration,especially the displacement change at the excavation edge;With the increase of slope after excavation,the local stability of the slope after excavation has a significant trend of deterioration;With the increase of the original slope height,the local stability of the slope after excavation has a significant trend of deterioration;As the original slope gradient increases,the local stability of the slope after excavation has a significant trend of deterioration.(4)Comparing the actual survey data and numerical simulation results,it can be found that the impact trend of each factor in the actual survey on the stability of the excavated slope is basically consistent with the impact trend of each factor in the numerical simulation results on the stability of the excavated slope.For the original slope height,there are differences between numerical simulation and statistical analysis.The main reason is that during statistical analysis,the number of four gradient samples with an original slope height greater than 60 m is too small,affecting the overall percentage change trend.By analyzing the four gradients with an original slope height of less than 60 m,it can be found that the change trend in the percentage of basically stable and unstable slopes is not obvious,mainly due to subjective factors.(5)Combining the qualitative analysis results and numerical simulation results of actual survey and statistical data,it can be found that when the excavation body meets the requirements of less than 45 m in width,less than 60 ° in slope after excavation,and less than 9m in excavation height;At the same time,select the original slope with smaller height and slope for excavation and building.The smaller the slope and height,the smaller the risk after excavation.Meeting the above plans can effectively reduce the risk of slope excavation and reduce the possibility of disasters caused by slope cutting and building.