| In this paper,the engineering of the local secondary landslide of Dongjiaxiang ancient landslide is taken as an example.After site investigation and survey,information on the regional geological conditions of the site is collected,the boundary of Dongjiaxiang ancient landslide is identified,and the boundary of the overall ancient landslide and the local secondary landslide is divided,and the relationship between the overall ancient landslide and the local secondary landslide is inferred.An improved landslide prediction theory of folded slip surface is proposed.On the basis of physical-mechanical tests,indoor direct shear tests and creep tests of slip zone soils were conducted,and the data of direct shear creep tests of slip zone soils were processed by using Young’s loading method with graded incremental loading,and the full course curves of creep under all levels of positive stress and the direct shear creep curves of strain-time relationship under all levels of horizontal shear stress were obtained,and the peak strength parameters and long-term strength parameters were determined to derive the creep The parameters of the creep equation were determined.Using kinetic theory and limit equilibrium theory,the acceleration equation of the landslide was determined,and numerical simulation was conducted by FLAC3 D to verify the stability of the landslide and propose the prediction time.The reliability of the folded slip surface theory was verified based on the landslide displacement data that had occurred.The main research work and results are as follows:(1)From a macroscopic point of view,combining the signs of surface deformation and topographic features of the Dongjiaxiang landslide,it is inferred that the local secondary landslides in the two deformation zones are not directly related to the overall ancient landslide of Dongjiaxiang.A calculation method is proposed to predict the time of landslide occurrence based on the theory of folded slip surface.The method is derived from the fundamental equations of limit equilibrium theory and dynamics,and establishes the relationship between long-term intensity parameters and acceleration during landslide occurrence.(2)The peak strength of the slip zone soil of the Dongjiaxiang local secondary landslide was determined by using the comprehensive analysis of the indoor direct shear test and the physical mechanics test data,and the long-term strength parameters were derived from the direct shear creep test of the slip zone soil,and the Maxwell and Kelvin unit shear moduli in the Burger body under different positive and shear stresses were derived by fitting the curve with ORIGIN and viscous coefficient.(3)Numerical simulations of creep of the overall value of viscoplastic parameters and creep of the segmental value of viscoplastic parameters were carried out for the Dongjiaxiang ancient landslide using FLAC3 D to obtain the displacement change curve with time and the prediction time when the landslide is unstable,and then the prediction time of landslide occurrence was analyzed by the theoretical analysis of plane slip surface and folded slip surface respectively,and the creep values of both were compared and analyzed.The simulation results and the theoretical analysis results were compared to verify the accuracy and reliability of the application methods of numerical simulation and theoretical analysis of folded slip surface by segmental processing.(4)Based on the actual monitoring data and numerical simulation results of the landslide in Baishi Township,the displacement-time curves of both were compared with the actual monitoring data to verify the effectiveness of the segmented linear slip surface theory and the segmented numerical simulation method.The overall trend of the displacement-time curve during the actual monitoring process is similar to the numerical simulation,and the results of the accelerated creep phase of the sliding body during the actual monitoring process are also similar to the numerical simulation results.Therefore,the reliability of landslide prediction is verified. |
