Numerical Simulation Of Mechanical Characteristics Of Rock Mass By Geometric Parameters Of Joints

With the growth of national economy,rock mass engineering occupies more and more proportion in infrastructure construction,which requires that the mechanical properties of rock mass should be fully grasped and applied.However,rock mass is a kind of complex,anisotropic and heterogeneous discontinuum.At present,the research on mechanical properties of jointed rock mass is not comprehensive,which makes collapse and other accidents often occur in rock mass engineering.The mechanical properties of rock mass are mainly affected by the geometric parameters of joints,so it is very important to study the influence of the geometric parameters of joints on the mechanical properties of rock mass.In this paper,PFC2 D software was used to establish a synthetic rock mass model.Through single factor analysis and orthogonal experimental analysis,the influences of joint dip angle,joint length,rock bridge length,joint spacing and joint step angle on the mechanical characteristics of rock mass were discussed and analyzed.The main research work is as follows:(1)Establishment and calibration of a synthetic rock mass model(SRM).The two dimensional synthetic model of rock mass was established,and the mesoscopic parameters of the complete rock mass and structural plane were calibrated by comparing the physical experiments.The calibration results were in good agreement with the experiments.At the same time,the failure mode of the model is compared with the physical experiment,and it is found that the failure mode is basically the same.(2)The influence of joint geometric parameters on mechanical characteristics of jointed rock mass was analyzed by single factor method.The influence of single joint geometry on the mechanical characteristics of rock mass was studied by controlling other factors and changing one of the joint geometric parameters.(3)The significance of the geometrical parameters of joints on the mechanical strength index of jointed rock mass was analyzed by orthogonal experiment.Orthogonal experiment can randomly combine the geometric parameters of joints,which makes the experimental results more reliable.It is found that when the joint inclination angle between 10° and 50°,the joint length,joint inclination angle,joint spacing and rock bridge length have significant effects on the uniaxial compression strength and elastic modulus of rock mass.When the joint inclination angle is between 50° and 90°,the influence of the length of rock bridge on the uniaxial compression strength and elastic modulus of rock mass is not obvious.The joint step angle has no significant effect on the uniaxial compression strength and elastic modulus of rock mass in the whole range of joint dip angle.(4)The relationship between the elastic modulus of rock mass and the strength of uniaxial compression is discussed by using regression fitting method.In the end,the regression fitting method is used to fit the relationship between the strength of uniaxial compression and the elastic modulus of rock mass when the inclination anngle is 10°?50° and 50°?90°.