Macro-micro Analysis Based On The Damage Characteristics Of Standard Joint Shear Test

The formation of rock determines the complex material properties of the rock.Under the complex geological action in nature,the formation of different geological structural surfaces with different properties and different scales makes the rock's failure characteristics and mechanical properties complex.With the rapid development of the economy,the geotechnical problems encountered during the production and construction process have become increasingly complicated.Based on the previous experiments and theoretical results of rock joints,this paper determines the research variables and analyzes the deformation characteristics and strength of joints and multi-joined rock mass from both meso-macro perspectives through laboratory and numerical simulations.The following work:(1)In this paper,the similarity ratio of rock materials is determined by orthogonal test,and then the test piece mold is made based on JRC curve,and then the test piece is prepared.The various mechanical material parameters of similar materials are determined by direct shear test and uniaxial compression test.(2)The shearing characteristics of the specimens were investigated to study the shear behavior of the specimens.The fracture morphology and shear strength of the jointed rock mass under different confining pressures and roughness were studied.The results show that the influence of confining pressure on the shear strength of the joint surface is obvious.The greater the confining pressure,the greater the shear strength.The roughness of different joint surfaces and the shear rate have a significant effect on the shear characteristics of the joint surface.(3)The micro-failure mechanism of joints in shear process is analyzed by using finite element software ABAQUS.In order to better study the distribution of random cracks and micro-failure around joints in shear process,the zero-thickness cohesive force element is embedded in batches between the elements by using ABAQUS mesh generation to simulate the chemical bonding between rock particles,which makes it more accurate to mention.The generation and propagation of meso-cracks in existing rock block specimens.Comparing the simulation results with the experimental data,the results show that they are in good agreement.(4)Based on the single joint numerical model,the multi-joint rock mass is simulated,and the effects of joint surface roughness,shear rate and confining pressure on shear strength under two parallel joints are studied.The simulation results show that the peak shear stress of double-jointed rock mass decreases due to the failure of interlayer in jointed rock.In the shear process,the peak shear strength of jointed rock mass with higher roughness also does not show a significant positive correlation.From the whole shear process,the change of shear displacement-stress of double-jointed rock mass under direct shear is roughly the same as that of single-jointed rock mass,but there is no significant sudden drop of multi-joints in the residual shear stage.