Research On The Expansion And Penetration Of Rock Masses With Non-coplanar And Non-penetrating Joints

Non-coplanar non-penetrating jointed rock mass samples were prepared by rock-like method,model test was carried out by rmt-301 rock and concrete mechanics experimental system,and numerical software was used to simulate the shear behavior of non-coplanar non-penetrating jointed rock mass.The deformation,strength,failure mechanism and connection form of coplanar non-penetrating jointed rock mass were studied.The main research results are as follows:(1)Based on the selection principle of rock properties and similar materials,the conch composite Portland cement 325 R was used as the cementing material.After screening,the graded continuous seven-eye sand was used as the particle aggregate to make rock-like materials.The basic mechanical properties were similar to those of shale.(2)Direct shear tests of non-coplanar incoherent jointed rock masses under 56 working conditions were carried out.The penetrating failure path of noncoplanar incoherent jointed rock mass under different normal stresses is studied and the characteristics of shear curve are analyzed.The strength variation of rock mass with different inclinations and quantities of noncoplanar incoherent joints under the same normal stress is studied.The results show that the shear stress-strain curve can be divided into four stages:linear elastic stage,crack initiation stage,rock bridge connection stage and residual friction stage.The inverse shear strength is greater than the forward shear strength.The number of joints has a great influence on the shear strength.The less the number of joints,the greater the shear strength.The peak shear strength of incoherent jointed rock mass varies trigonometric with the Angle of jointing..(3)The joint Angle has an important influence on the failure mode of non-coplanar non-penetrating jointed rock mass.When the Angle of joint Angle issmall,the failure path shows that the upper tip of joint cracks and laps to the lower tip of adjacent joints.When the joint Angle is large,the failure penetration path is manifested as cracking on the upper tip of the joint,overlapping on the middle and upper part of the adjacent joints,or cracking from the tip,and tensile failure on the upper and lower part of the sample.In particular,when the joint Angle is 0°,the failure mode is shear failure along the shear plane.(4)The penetrating failure of non-coplanar non-penetrating jointed rock mass is firstly caused by the tensile crack at the joint tip.With the increase of shear stress,the tensile failure is restrained,and the shear failure gradually occurs.Finally,the rock bridge is connected by shear failure.The shear strength of non-coplanar non-penetrating jointed rock mass is related to the length of bridging failure.(5)Numerical simulation was carried out for direct shear test of non-coplanar non-penetrating jointed rock mass.Firstly,32 orthogonal experiments were designed to study the macroscopic mechanical response of the mesoscopic parameters of the parallel bonding model,and the results were verified by the conventional triaxial compression test in the laboratory.The mesoscopic parameters were applied to the direct shear numerical simulation under different working conditions,and the simulation results were in good agreement with the laboratory test results.From the microscopic perspective(monitoring and measuring circle,fabric analysis),the normal and tangential contact forces between particle systems were analyzed,the transmission law of force chain was studied,and the whole process of macroscopic shear mechanics behavior change was explained.