Strength Test And Numerical Simulation Of Rocks With Different Roughness

Under the long-term effect of the tectonic stress,joints and faults occur in rock mass,which eventually produces an anisotropic structure.At the same time,the rock instability is caused by cracks in rock mass,which easily produces a through sliding surface.Roughness is an important factor that affects the mechanical properties of rock joints,and it is also one of the key factors controlling the stability of rock engineering such as slopes and underground chambers.Because it is difficult to obtain jointed rock samples in nature,this paper uses similar materials to simulate the mechanical properties of jointed rock.In addition,combined with laboratory tests and numerical simulations,the deformation and failure characteristics and crack evolution of jointed rock mass were studied,and the deformation and failure mechanism of stepped joint slope with roughness was further analyzed.The main research results are as following:?1?The uniaxial compression test showed that the influence of the Joint Roughness Coefficient?JRC?on the sample strength is mainly reflected in two aspects:one is the peak intensity,the peak intensity increases with the increase of JRC;the other is the residual intensity,which shows a stepwise downward trend with the increase of JRC.In addition,as JRC gradually increase,the failure mode of the specimen is gradually changed from shear failure to shear-split mixed failure.?2?The results of the double-joint rock direct shear test indicate that the load-displacement curve of the sample is divided into four stages:ascending stage,descending stage,rebound stage,stable friction stage.In addition,as the JRC increases,the peak stress of the sample increases,and shear crack growth rate of the prefabricated crack tip slow down,and the shear slip failure occurs at the center of the sample.The peak stress of the sample decreases as the joint inclination increases.The increase in the macro cracks is more likely to cause instability and failure.The peak stress of the sample increases with the increase of the inclination of the rock bridge,and the overlapping of shear cracks decrease.?3?Based on the particle flow software Particle Flow Code^2D(PFC^2D),the macro mechanical parameters were calibrated,and the numerical analysis was carried out on indoor samples.The failure states of the numerical samples and the tests of the samples were compared and analyzed,and the evolution result of the microscopic force chain of the microcracks in the model with the macroscopic mechanical strength was studied.The results show that the shear crack near the tangential load develops faster when the joint inclination angle is greater than 30°.The rock bridge will not penetrate when the rock bridge inclination angle is greater than 90°.?4?The PFC^2D model of stepped joint slope with roughness was established,and the gravity increase method was used to study the deformation and failure of slopes in different structural planes.Taking a slope model as an example,the evolution of slope stress and crack was analyzed.The results show that the stepped joint slope with roughness mainly produces topple-slip mixed failure.When the rock bridge in the middle and upper part of the slope penetrates,the crack of the slope increases sharply,and the slope enters the critical stage of shear-slip failure.