Research On Normal Deformation Of Rock Joints Based On Three-Dimensional Topography

The jointed rock mass will produce corresponding deformation under the action of load.The deformation mainly includes the deformation of the complete rock material and the joint deformation,and the joint deformation plays a major control role.The joints are deformed,and the size,distribution and connectivity of the internal contact area and void area also change accordingly,which in turn affects the mechanics and permeability characteristics of the joints.Therefore,joint deformation is one of the hot issues in rock mechanics research,and it is also a key concern in various rock engineering.Based on the three-dimensional morphology of the joints,this paper proposes a theoretical model for studying the normal deformation of rock joints.This model assumes that the joint micro-protrusions and surrounding rocks exhibit linear elasticity.The deformation of any point on the joint surface is caused by all actions on the joints.Caused by the force.Considering the interaction between the asperities,the deformation consists of three parts:one is the deformation caused by the asperity compression,and the other is the deformation of the upper and lower half of the asperity caused by the force acting on the asperity.The third is the deformation of the upper and lower half spaces of the asperity caused by the force acting on all other asperities.After all the deformation components are given,the flexibility matrix of the theoretical model can be defined,the equations about force and deformation can be obtained,and the joint surface deformation can be solved by the principle of system energy minimization.The artificial joints are obtained through direct shear experiments,and the morphology information of the joints is obtained by using a three-dimensional scanner.Then the theoretical model is used to obtain the stress-deformation curves of the joints under normal loads,and nonlinear fitting is used to establish the joints in the normal direction.Constitutive model under stress.Finally,indoor experiments verify the accuracy of the theoretical model.The main conclusions of this paper are as follows:(1)The joint deformation increases rapidly with the increase of the normal stress,and the stress-deformation curves are all concave upwards.As the stress increases,the stress-deformation curve becomes steeper and steeper,which also shows that the joints are gradually closed.When the stress reaches a certain level,the deformation hardly increases,indicating that the joints are basically closed at this time.(2)The joint deformation always increases with the increase of the stress,but the increase of the closure amount decreases with the increase of the stress(the normal stiffness increases with the increase of the stress),and the normal deformation of the joint is nonlinear Characteristics,joint normal stress and deformation present a power function relationship.(3)From the perspective of deformation,as the stress gradually increases,the number of asperities in contact with each other gradually increases,and the normal stiffness of the joints also gradually increases at this time.The increasing speed of joint stiffness is related to the increasing speed of the contact number of asperities.When the stress reaches a certain level,the deformation hardly increases,that is,the number of asperities in contact no longer increases,and the joint stiffness appears to be a constant.