Simulation Of Landslide Dynamic Process Using The Material Point Method

Simulation of landslide dynamic process is a primary task in the research of geological disaster.The goal of slope analysis was to evaluate the stability of the slopes without considering their motion process.With the researches on slopes moving forward,the dynamic process of slope failure has been paid more and more attention.The material point method has great advantages over traditional numerical simulation method in solving large-deformation problems.Based on the porous media theory,this paper constructed the formula of the coupled material point method and compiled the program.Some specific problems regarding the simulation of slope dynamic process by the material point method were discussed,and some actual cases were simulated.Then the following conclusions have been drawn.(1)Three calculation schemes of the coupling material point method were suggested:MUSL-p,USF-p,and USL-p,in which USF-p scheme has the highest computation efficiency,and the MUSL-p scheme has the highest computation one.When the simulated domain has an irregular shape and the background grid is affected by only one node,USL-p sheme can cause a matter point explosion,leading to a calculation failure while the MUSL-p and USL-p scheme can maintain a good stability.(2)By using Janmann stress rate,calculating stress matrix from strain matrix,the effect of the rigid rotation on the trial stress was consider,and the simulation of large deformation on the basis of the Mohr-Coulomb model was carried out,thus the material point explosion can be avoided in the simulation of a three-dimensional grain collapse through the material point method.(3)The peak plastic strain has an effect on the initiation of a landslide.A smaller peak plastic strain causes a wider local failure zone,and a landslide occurs more easily.The residual strength parameters have an effect on the slide length and the crack on the top of the slope,and the location of the shear band.A smaller residual inner friction angle means a greater slide length,and tensile cracks on the top of slope occur more easily.The random peak strength parameters are helpful in the development of local failure.The random parameters cause a lower shear band when compared with deterministic parameters.(4)The lateral spread slide initates from a local failure at the front of a slope;then the failure zone propagates into the slope,leading to a failure plane and forming unique grabens and horsts.With the development of deformation,the second order of grabens and horsts occur because of the tension within the first order of grabens..(5)The landslide dynamic processis affected not only by the internal strength parameters of slope mass,but also by the slide contact between different rock masses.A saturated contact algorithm is proposed based on the traditional contact algorithm,which allows a relative slip between two saturated media.The waste in the Shenzhen landslide provides driving force and forms a local failure zone in the rear.Meanwhile,a local failure zone occurs in the front.These two local failure zones spread towards the inner slope and form a continuous shear band.The contact action between waste and bedrock affects the slide length of the landslide.