Study On Anisotropic Yield Criterion Of Jointed Rock Mass And Its Application

The rock mass is a composite structure made up of rock and various geological joints. Many joints with variant trace length distributed in the rock mass produced by geological structure made the mechanical properties of rock mass discontinuous,heterogeneous and strong anisotropic.The joints affected and controlled the mechanical deformation properties of rock mass and failure of rock mass engineering because of instability.In practice,It is necessary to get the comprehensive mechanical parameters of rock mass by some scientific method.Take into account of the data of joints statistic and technique of joints network simulation, the comprehensive shear strength parameters of rock mass are obtained.The anisotropic criterion is established in this paper.In order to take the research results of the paper into use in numerical simulation of rock mass engineering,some promotion is made for ABAQUS. The main research works and conclusions are summed up as followed.(1)The numerical simulation analysis method,the technique of joints network and the theory of anisotropic yield criterion are summarized in this paper.The analysis on development and main difficulties of above are made.On the basis of the above summary and analysis,the research emphasis and study methods of paper are presented.(2)Base on the analysis of position relation of finite plane area,limit line and plane point, the Fortran program is developed to generated two-dimensional joints network simulation graph by Monte Carlo method.In order to get comprehensive shear strength parameters of rock mass in every dimension,the Fortran program of searching the failure path associated with minimal shear resistance is made by dynamic programming method.(3)The theory and methods of anisotropic yield criterion is studied by using comprehensive shear strength parameters of rock mass obtained by network simulation and considering Rankine criteria on the base of isotropic Mohr-Coulomb yield criterion. The above theory and methods are applied to establish anisotropic yield criterion and to analyze the way to introduce it into the numerical analysis.In order to introduce the anisotropic yield criterion into ABAQUS,the codes are developed by using the Fortran language.Theoretical anslysis and numerical anslysis indicate that the maximum shear stress plane can not be the same of yield plane in orthotropic matericals.lt can improve the shortcomings of overestimating the material tensile strength by combining Rankine and Mohr-Coulomb criteria. The anisotropic yield criterion can simulate the destruction of the rock mass reflected by the relationship between resistance and response.(4)The research results of anisotropic criterion are applied to numerical simulation for the typical gravity dam. On the basis of the numerical simulation results,the Fortran program is established searching for the deep foundation sliding surface.And,the minimum safety factor is calculated to evaluate dam stability.