Analysis Of Landslide Stability And Research On Reasonable Pile Spacing Based On Reliability

The stability analysis and treatment of landslides have always been a hot spot in the study of landslides.The traditional stability analysis method takes the stability coefficient of the landslide as the only measurement index,and all the influences caused by unknown factors and uncertainties are compensated by increasing the safety factor.This method cannot objectively reflect the degree of real security of the landslide.Anti-slide piles have been widely used in landslide treatment projects,and the pile spacing is an important parameter in the design of anti-slide piles.The existing pile spacing algorithm does not consider the influence of the variability of the calculation parameters,so it cannot truly reflect the reliability of the anti-slide piles to strengthen the landslide.The reliability analysis method can fully take the abovementioned uncertain factors into consideration.The use of reliability analysis is of great importance in reasonably evaluating the stability of landslides and guiding the design of the pile spacing of anti-slide piles.This thesis studies the application of Monte-Carlo reliability analysis method in landslide stability analysis and anti-slide pile spacing design.Firstly,a Monte-Carlo-based reliability analysis is carried out on the stability of Dazigou No.3 landslide,combined with the calculation results of the transfer coefficient method,comprehensively evaluates the stability of the landslide;then combined with engineering examples,the Monte-Carlo reliability analysis method is used to study the variation of reliability with pile spacing for different parameter variability.Finally,the optimal and reasonable pile spacing that can meet the reliability design requirements is given for the project example.The main research results obtained in this thesis are as follows:(1)Firstly,relying on Dazigou No.3 landslide,based on the calculation principle of the transfer coefficient method,a reliability analysis model for analyzing the stability of the landslide with the Monte-Carlo method is established,and then the stability of each profile under three different conditions is calculated and evaluated using the transfer coefficient method and the Monte-Carlo analysis method respectively.By combining the evaluation results of the two methods,it can be seen that Dazigou No.3 landslide is in an overall stable state under natural conditions;it is in a basically stable to stable state under full water conditions;and it is in a basically stable to unstable state under full water and earthquake conditions.(2)By comparing the evaluation results of the traditional safety factor method and the Monte-Carlo analysis method,it is found that the conclusions obtained from the evaluation of the stable state of the landslide based on the stability factor value of the traditional method and the average value of the Monte-Carlo analysis method are consistent.When evaluating the stable state of a landslide by failure probability,only the two conditions of saturated and seismic conditions of section ?-?' and saturated conditions of section ?-?' are different from the evaluation results of traditional methods.The evaluation results of Monte-Carlo method in these two special cases are relatively conservative.The Monte-Carlo reliability analysis method gives the mean value of the stability coefficient along with the potential instability risk of the landslide as a reference,thus providing a basis for engineering decisions from a risk analysis perspective.(3)Based on the previous studies on the effect of soil arch between anti-slide piles and the critical pile spacing,this thesis establishes a limit state functional function for the spacing of anti-slip piles based on the Mohr-Coulomb damage criterion,and then uses the Monte-Carlo method to calculate the reliability under different pile spacing and different parameter variability by combining with engineering examples.The research results show that as the pile spacing increases,the corresponding failure probability also increases;at the same time,the variability of geotechnical parameters has a greater impact on the reliability of the anti-slide pile spacing.When the parameter variability is low,the failure probability under the corresponding pile spacing is lower;when the parameter variability is high,the failure probability under the corresponding pile spacing is higher.Therefore,in order to ensure sufficient stability of the soil arch between the piles,the influence of the variability of geotechnical parameters on the value of the pile spacing needs to be considered when designing the pile spacing.(4)The recommended values of reasonable pile spacing obtained by Monte-Carlo analysis are compared with those obtained by other conventional algorithms,and it is found that the recommended values of pile spacing obtained by conventional algorithms do not necessarily meet the conditions of reliability design.From the point of view of the reliability of landslide pile reinforcement,it is more practical to adopt the Monte-Carlo reliability analysis method to guide the design of the pile spacing of anti-slide piles than other methods in this thesis.