The Shear Deformation Characteristics Of The Joint By Considering The Three-dimensional Morphology

The deformation and failure of rock mass during shearing often occurs along joints,which indicates that the shear behaviors are closely related to the morphology of joint plane.Therefore,it is necessary to study the shear deformation behaviors of joint by considering its morphology characteristics.In this paper,three-dimensional laser scanning technology and fractal theory was applied to study the sampling precision of joint plane morphology information and the spatial distribution characteristics of roughness.Moreover,a three dimensional morphological model was proposed.By considering the morphology characteristics of joint plane,the physical models of joints were prepared by using 3D printing technology for shear tests.A stiffness characterization model was proposed to describe the deformation characteristics of the structure plane,and the experimental verification was carried out in combination with the rock mass constitutive model.The main research contents and conclusions are as follows:?1?The sampling precision of joint morphology information and distribution characteristics of joint roughness coefficient?JRC?were studied.The interval effect of the sampling points on the section line and the section line on the joint plane was studied during the JRC calculation process.According to the fluctuation of JRC value at different sampling intervals,the concept of critical interval value was put forward to describe the interval effects.It was found that the critical interval value of section line is about 4mm,while the critical interval value of the sampling point has a negative exponential relationship with JRC value.On the basis of sampling precision determination,the roughness anisotropy of the collected31 joints were studied,and it was found that the JRC value in the same direction obeys lognormal distribution.?2?A new morphology parameter was proposed and a three dimensional morphology parameter representation model was established.On the basis of the study of morphology information sampling precision and JRC distribution characteristics,a new three dimensional parameterG_?^3D was proposed by considering undulating angle,undulating height and climbing path parameters.Then a three dimensional morphology model was established,and its reasonability was verified by the shear strength parameters obtained from the direct shear test of joint.?3?A stiffness representation model was established to describe the deformation characteristics of joint.3D printing technology was used to restore the joint morphology,and pouring physical joint models with three materials strength were used for shearing tests in eight directions.The tangential stiffness model was established by considering morphological parameter,rock strength of joints and the normal stress.The normal stiffness model was established by considering the normal stress and rock strength of joint.Combining the tangential stiffness model and the normal stiffness model,the joint stiffness characterization model is constructed.?4?The stiffness representation model was verified by experiments.By using the stiffness representation model and combining with the constitutive relation of rock mass,the theoretical formula for calculating the elastic modulus was derived.The cylinder samples with specific morphological joints were prepared,and the uniaxial compression tests on cylinder samples with single joint with different dips were carried out to obtain the elastic modulus.There is little difference between theoretical values and experimental values of rock mass elastic modulus.With the change of inclination angle,the modulus obtained from the two methods have the same change rule,and with the increase of material strength,the error of elastic modulus between calculated value and experimental value gradually decreases,which reflects the reasonability of stiffness representation models.?5?According to research results mentioned above,it can be seen that when the related joint morphology parameters,stress state and rock mass material strength have been obtained,the complicated tests can be saved,and the joint stiffness parameters can be obtained by directly using the joint stiffness representation model.Thus,it is more convenient to describe the deformation behavior of joint.