Prediction Of Failure Conditions And Failure Probability Of Typical Unstable Slope In Chenxi County,Hunan Province

The prediction of failure conditions and failure probability about shopes is one of the main tasks in the field of hydraulic engineering and geological engineering.Landslide disaster is a direct result of the slope failure.Based on the investigation and analysis of landslide disaster,it is the foundation of preventing disaster and the basis of make countermeasures to prevention and control landslide disaster that choice suitable calculation model to predict the failure conditions and failure probability of slope.Because of its special natural geography and geological environment,chenxi county is one of the areas that landslide disaster happens frequently in hunan province.Based on the survey result of landslide disaster and potential landslide in chenxi county,hunan province,this paper takes engineering rock mass,Slope type,macroscopic stability and threat object into consider to choice two typical unstable slopes as the research object.These two unstable slopes are Xizhuangping 16th group unstable slope and Youzhuang unstable slope.In this paper,SEEP/W module and SLOPE/W module in GeoStudio software are coupled and used to analyze stability and its change rules,internal mechanism and to predicte failure probability under different rainfall conditions.According to the analysis results,the I-D curve?intensity-duration curve?of unstable state is fitted and the approximate accumulative rainfall threshold of unstable state is preliminarily judged.Based on the sensitivity of slope stability to geotechnical parameters and variation range of parameter range,monte-carlo analysis method is used to predict the failure probability of Xizhuangping16th group unstable slope under different rainfall codition,evaluate its dangerous state.Based on the analysis result of failure probability,the I-D curves with the probability of failuer greater than 0 and 50%were respectively fitted and the cumulative rainfall threshold with the probability of failuer greater than 0 and 50%were preliminarily judged.Research findings:?1?Landslides and hidden dangers of red-layer overburden layer and landslides of limestone residual soil are the major landslide hazards and hidden dangers in chenxi county,respectively accounting for 58.6%and 24.1%of the total number of landslide disasters and hidden dangers,and its main influencing factors are rainfall and human engineering activities.?2?For Xizhuangping 16th group unstable slope:?1?During the condition of maximum daily rainfall in 50 years and maximum daily rainfall in 100 years,its minimum factor of stability is 1.093 and 1.080respectively,it is always in stable state and basicstable state,its maximum probability of failure is 7.05%and 11.15%,its safety level is low risk state.?2?In the condition of continuous rain?25mm/d?,continuous heavy rain?50mm/d?,continuous rainstorm?100mm/d?,and continuous heavy rainstorm?200mm/d?,the time that it enter to the unstable state is the 20th day,the 9th day,the5th day and the 3th day respectively.In this time,the probability of failure is 57.65%,77.85%,86.75%and 87.30%respectively,and in medium risk state,high risk state,high risk state and high risk state respectively.?3?Its I-D curve equation of unstable state is I=611.21D^-1.092,the cumulative rainfall threshold of unstable state is approximately 500 mm.?4?The Sensitivity which stability to the saturated unit weight,saturated cohesion,and saturated internal friction angle of the silty clay is 0.2719,0.0530,0.0324respectively.The Sensitivity which stability to the saturated unit weight,saturated cohesion,and saturated internal friction angle of the Strong weathering argillaceous siltstone is 0.2719,0.0530,0.0324 respectively.?5?There has a good relationship between factor of stability and probability of failure:the factor of stability is greater than 1.15,equal to 1.10,1.05 and 1.00corresponding to probability of failure is 0%,5%,20%and 50%respectively.?6?The I-D curve equations of the slope that the failure probability greater than 0and 50%based on the analysis of failure probability are:I=195.44D^-0.883?I=611.21D^-1.092;the cumulative rainfall threshold of the slope that the failure probability greater than 0 and 50%is approximately 250 mm,450 mm respectively.?3?For Youzhuang unstable slope:?1?During the condition of maximum daily rainfall in 50 years and maximum daily rainfall in 100 years,its minimum factor of stability is 1.061,it is always in stable state and basicstable state.?2? In the condition of continuous rain ?25mm/d?, continuous heavy rain ?50mm/d?,continuous rainstorm?100mm/d?,and continuous heavy rainstorm?200mm/d?,the time that it enter to the unstable state is the 13th day,the 5th day,the3th day and the 2th day respectively.?3?Its I-D curve equation of unstable state is I=333.69D^-1.061,the cumulative rainfall threshold of unstable state is approximately 300 mm.