Study On Parameter Variability Under Different Reliability Analysis Method

The classical problem in soil mechanics has always been the problem of slope stability,from qualitative analysis,quantitative analysis to the finite element method and uncertainty analysis method using software,and the slope stability analysis method is also more and more suitable and perfect.In order to eliminate the uncertainties not considered in the deterministic analysis,the uncertain analysis method based on the deterministic analysis method came into being,but often ignores the spatial variability of soil parameters.In this paper,Monte Carlo simulation method,response surface method and Rosenbluth method were used to analyze the reliability of homogeneous and heterogeneous slopes,and the differences between the three reliability methods and the influence of soil parameter variability on slope reliability were compared.When calculating slope reliability by using different reliability methods,the differences between the three reliability methods under the same slope safety state function function are compared.When constructing functional functions of different slope safety states,the differences between different functional functions under the same reliability method are compared,and the calculations are all under the condition that the parameters conform to the normal distribution.In order to understand the differences more comprehensively and accurately,the homogeneous slope,heterogeneous slope and engineering examples were analyzed separately.The main work is as follows:1.Systematically introduce and classify various uncertainties,and compare various commonly used reliability analysis methods;On the basis of the limit equilibrium method,different slope state functions are established to compare the differences.The coefficient of variation of soil parameters was changed on the same slope state function,and the change of slope reliability index was analyzed when soil parameters changed.The double variation and single variation of soil parameters were studied separately,and the influence of soil parameter variability on reliability was further analyzed,and the changes of each parameter on slope stability and the differences between different methods were more comprehensively understood.2.Considering the influence of various factors on slope stability,the following conclusions can be obtained through calculation and comparison:(1)If the slope state function is established by different limit equilibrium methods,the reliability index obtained by different state functions is different.The reliability of the slope obtained by the Fellenius method is the smallest,and the reliability index obtained by the Bishop method and the M-P method is close to that of the Monte Carlo method,so the influence of the slope state function cannot be ignored when performing reliability analysis.(2)Under the same slope state function of different reliability methods,taking Monte Carlo method simulation 5000 calculation reliability index as the benchmark,the reliability index calculated by Rosenbluth method is closer than that of the center point method and the verification point method,so for general engineering,the reliability of Rosenbrus method calculation can meet the calculation accuracy.(3)Study the influence of parameter variability on reliability index,when the coefficient of variation of soil parameters changes,regardless of parameter double variation or single variation,the increase of the coefficient of variation decreases the reliability index of the slope,and further research finds that the coefficient of variation of friction angle in soil φ increases,and the decrease rate of reliability index decreases faster than with the increase of cohesion C coefficient of variation,so it can be considered that the reliability index is more sensitive to the change of φ.