Stability Analysis Of Abandoned Dreg Sites Based On The Random Field Theory

As one of the typical geological hazards,landslide poses a serious threat to human's activities all over the world.With the development of infrastructure in China,a large number of abandoned dreg fields are constructed in the middle and west parts of China,which destroy the local environment and threaten the safety of people's life and property.Therefore,the evaluation of abandoned dreg fields stability through correct and reasonable methods has significantly high practical value and social benefits.Currently,the deterministic method to obtain a constant safety factor is used to evaluate the stability of abandoned dreg fields.However,the uncertainty of soil parameters is not considered in the solving process,which is not reasonable.In order to analyze the influence of the spatial variability of shear strength parameters on the abandoned dreg fields stability,the Karhunen-loeve expansion method and improved Cholesky decomposition technique for the random field discretization are developed,and non-intrusive stochastic method for slope reliability is used.The main contents and results of this study are as follows:(1)The theoretical system of reliability analysis of heterogeneous slope stability through the random field theory was introduced.The shear strength parameters of rock and soil are random field variables and the modified Cholesky decomposition method was used to spread the random field.The non-intrusive stochastic finite element method was used to analysis the slopes with different spatial distribution of shear strength parameters.The limit equilibrium analysis was performed to analysis the slope stability with the consideration of spatial variability of rock and soil shear strength parameters.The calculation and programming of the method are simple.The discrete random variables correspond to the finite elements.(2)The analysis of a slope example shows that with the consideration of spatial variability of the soil and rock shear strength parameters,the average safety factor is close to the result obtained through the mean parameter.The guarantee rate of stability safety factor is about 50%,and the slope failure is still possible.The failure probability is related to the parameter variability.With the increase of variation coefficients of the rock and soil friction angle and cohesion force,the probability of slope failure increases.With the increase of vertical fluctuation range,the slope safety factor increases,but the failure probability of slope increases.With the increase ofabsolute negative correlation coefficient of shear strength parameters,the slope failure probability decreases significantly.(3)Stability analysis was performed on an actual abandoned dreg site.The safety factor method was used to analyze the typical waste slag slopes in natural conditions.However,in some conditions(storms or earthquakes),safety probability was too small.After the cutting of slopes and decrease of load,the stability requirements were met.However,with the consideration of spatial variability of the shear strength parameters,the guarantee rate of single safety factor of the typical section of dreg site is only 39%,and the stability probability is only 76.7%.Therefore,the reliability analysis results of slope stability should be taken into consideration and the corresponding safety protection measures should be taken to ensure the stability of abandoned dreg site.