Research On Influence Factors Of Mechanics Charateristics And Charateristics Failure Mechanism Of Soil-rock Mixture

Soil-rock-mixture(SRM) is the main component of accumulation landslides,it isa kind of special geology material, which is different from the general homogenyizingsoil and the fractured rock mass.The compositions of SRM are betweenhomogenyizing soil and the fractured rock mass,it consists of different sized soil andstone piece.The mechanical properties of SRM are special,so that,the developmentalpatterns and deformation characteristics of accumulation landslide are different fromhomogeneous soil or rock mass slopes.At present,there are few studies on the themechanical properties of SRM and its factors, As a foundation that valuating andcontrolling the stability of slopes with SRM, how to understanding the mechanicsproperties of SRM has become an urgent research. For these reasons,the paper putsforward the method of loading and unloading true triaxial tests and controling processand the ways of determining the mesomechanics parameters of patticles based on thethree-dimensional micromechanics particle flow theory.By means of these tests, thepaper researches the mechanical properties of SRM under different stresspaths.Through numerical simulation tests,the paper aims to studying the laws ofmechanical properties of SRM,changing with the components of fragment stone, theseepage pressures and the stress paths,it is helpful to deepen and expand theunderstandings about this new geotechnical engineering geological materials.In the sum, the main works and research results are as follows.1. Based on the systematic summary of present research situation of soil-rock,researching methods,main outcomes,and analysing the exsisting problems,this paperpresents its major research contents and methods, and simulation test plans.2. Analysing the methods of modeling in PFC3D, common model parameters andthe steps of researching.Based on discussing the sensitivity of mesoscopicparameter ,it establishes the corresponding relationship between particle parametersand the macro parameters of material. Lots of test results indicate that the relationshipparticle contact rigidity with initial tangent modulus of materials is linearity, theparticle contact rigidity is more stronger and the initial tangent modulus is morebiger.The poisson's ratio of materials are the relationship between normal stiffness andtangent stiffness of particles.the micofrictions of particles are bigger,the peak strengthof materials are stronger and the strain softening phenomenons are more obvious.3.Through the numerical simulation triaxial tests,the paper studies the stress-strain curves and destruction features of SRM ,changing with the componentsof fragment stone. It presents that the strength and deformation characteristics displaybviously divisional.In the first region the components of fragment stone is less thanthe value 30% , the characteristics of SRM are determined by the properties of soil.Inthe second region the components of fragment stone are between the value 30% and70%,the characteristics of SRM are jointly determined by the properties of soil andfragment stone.In the third region the components of fragment stone is more than thevalue 70% ,the characteristics of SRM are determined by the properties of fragmentstone.4.Research the fluid-solid coupling theory of three-dimensional micromechanicsparticle flow and the calculation processes of fluid-solid coupling, the paterdiscusseses the fluid-solid coupling characteristics of SRM,it studies the deformationcharacteristics of SRM with different seepage pressures,the results show that the morecomponents of fragment stone,the permeability of SRM is more powerful,and it isincrease with increasing the seepage pressures .The seepage pressures have obvioussoftening effect to the binding parameter of SRM,the values of cohesion underseepage condition are one fifth under no seepage condition,however, under differentseepage pressures,the change of the internal friction Angle of SRM is not notable.5.Based on the three-dimensional micromechanics particle flow theory, the paperpreliminarily puts forward the method of loading and unloading true triaxial tests andcontroling process,it accomplishes the studying of the mechanical properties of SRMunder different seepage pressures,the test results show that the failure mode of SRM isShear failure under the load condition,however,there exists lots of tension fissureunder the unload condition. The value of cohesion is reduced by 20% and the internalfriction angle is increased by 30-40% under the unload stress path.