Numerical Simulation Study Of Tri-axial Experiment For Soil-Rock Mixture Based On CT Scanning

Soil-rock mixture is a kind of special geological material and has a wide spread in nature.Different from ordinary soil,it is comprised of rock blocks,fine soil particle and pore which is filled in.With the rise and development of all kinds of large-scale engineering construction,geological disasters related to soil-rock mixture has seriously affected the engineering construction and social development.Thus,it is important to figure out the deformation and failure mechanism of soil-rock mixture.In this paper,the cut images of soil-rock mixture based on the indoor tri-axial experiments were obtained by CT scanning.The true three dimensional models of soil-rock mixture under different stone content were reconstructed applying the technique of digital image processing,reverse engineering and numerical grid division.Using FLAC3D for numerical calculation,the deformation characteristics of soil-rock mixture under different stone content and confining pressure and the space motion of gravel in the process of tri-axial shear were studied.The main research and results are as follows:(1)The research status,research methods and the existing main problems of soil-rock mixture were summarized.And the importance of soil-rock mixture research was pointed out.This paper indicated the ideas,methods and content of this research.(2)According to the soil-rock mixture tri-axial test under different stone content which is 20%and 30%and different confining pressure which is 200kPa,400kPa and 600kPa,CT scanning was used to obtain the section images of each sample.The edge information of each gravel was extracted utilizing digital image processing technique.(3)According to point cloud data of each gravel,the true three dimensional model of gravel was reconstructed using Geomagic Studio.The model of soil-rock mixture was established by Boolean operation of ANSYS.With the help of ANSYS ICEM CFD,the grid model of soil-rock mixture was accomplished and imported to FLAC3D at last.(4)Based on the numerical model of soil-rock mixture,the influence of stone content and confining pressure on the deformation characteristics was studied.The results showed that,the compressive strength of rock-soil mixture under a certain stone content increased with confining pressure increasing.But the deformation and failure mode of the mixture didn't changed.Volume stone content was a kind of important factor which controlled the deformation and failure of soil-rock mixture.The strength of soil-rock mixture increased as stone content increased.However,soil acted as a skeleton when the volume stone content was low.The difference of deformation and failure mode of soil-rock mixture was small.(5)The formation and extension of shear belt of soil-rock mixture was mainly affected by gravel.Because of the high strength of gravel,a phenomenon of bypassing gravel during the formation process of shear belt was appeared.(6)The movement of gravel in the mixture mainly came from the extrusion of surrounding soil.The vertical displacement of upper gravel of the model is the largest.The lateral displacement of gravel close to outside of the model is generally greater than the gravel in the middle.However,the lateral displacement of gravel is relatively small in the area of more gravels and higher stress.(7)The gravels of soil-rock mixture rotated during the tri-axial shear process.And the angle of rotation is related to the size,shape,space position and stress state of gravel.The quantitative description of spatial movement of the gravel can be achieved through ICP algorithm.