Study On The Shear Mechanical Properties Of The Joint Of The Multi Occurrence Rock

In the process of deep geotechnical engineering implementation and stability evaluation,it is necessary to study the mechanical properties of joint rock mass with various occurrence,especially the mechanical and failure properties under shear load.In this paper,high strength gypsum is used as material to cast rough joint samples for direct shear test,and then to study the evolution law of the strength parameter cohesion,internal friction Angle and deformation parameter dilatancy angle.The shear failure characteristics of intermittent and rough jointed rock mass were further studied by using PFC.The main research results are as follows:(1)Through the direct shear test of the rough joint sample made of gypsum under 5 normal stresses:The relationship between peak strength(?m),residual strength(?r),peak displacement(u,n),shear and normal stiffness(ks kn)with JRC and normal stress under different working conditions was studied;Based on the mohr-coulomb theory,the evolution law functions of cohesion,internal friction Angle on roughness and plastic shear displacement are established:c=0.171+0.385·JRC+(0.0611+0.175·JRC)e-2.769up/?=0.8775+14.06·JRC+18.86·e-0.689up and the evolution law function of dilatancy Angle on normal stress,plastic shear displacement and roughness:?=3.222+[(8.695+1.295·JRC)+(-1.292-0.1545·JRC)?n]e(0·0074JRC-0.341)up;and according to the established evolution law,the shear stress-displacement curve and the dilatancy curve are respectively calculated and compared to the original test curve,so the correctness of the evolution function was verified.(2)Based on PFC particle flow numerical simulation software,three kinds of intermittent joint samples(A/B/C)were established and direct shear simulation tests were carried out.It has been discovered that:the Shear stress-displacement curve of kind B was easy to be effected by the angle of middle joint(?),especially in the case of 60°90°120°,the post-peak stage is prone to large fluctuations or even secondary peaks;The variation law of crack initiation stress(?k),peak strength(?m),peak displacement(um)and shear(ks)stiffness and the evolution law of microcrack and macroscopic crack were analyzed;And also the mechanism of crack propagation and failure is revealed by the trend of particle displacement and the microscopic Angle of local stress.(3)Based on the smooth joint bond model,the stress displacement curve and strength deformation characteristics of shear test specimens with different JRC joints are studied,and the crack evolution law of specimens is analyzed.The stress displacement curve and shear expansion curve characteristics of shear test specimens with the same joint under different normal stress are studied,and the growth trend and final failure mode of the number of two kinds of microcracks are also studied In addition,the influence of different joint forms of the same JRC on the characteristics of stress displacement curve and dilatancy curve in shear test and the failure characteristics of j oint specimens are also studied.There are 66 figures,13 tables and 93 references in the thesis.