Study On Anisotropy Of Deformation And Strength Of Layered Rock Mass

The heterogeneity,discontinuity and anisotropy of layered rock mass are more obvious than other rock masses of structural type.The mechanical properties are not only affected by physical parameters such as joints density and joints occurrence,but also the influence of the external environment such as the confining pressure.Therefore,it is necessary to make a deeper analysis of the basic mechanical properties of the layered rock mass and recognize its anisotropic variation,for sake of providing a theoretical basis for the engineering practice.Based on the stress-strain relationship and strength theory of statistical rock mechanics,combined with numerical simulation analysis,we mainly do research on the effects of the occurrence,density of the joints and confining pressure on the anisotropy characteristics of the layered rock mass.Based on the paper-square tunnel,the case analysis was carried out and corresponding support measures were proposed.The main research results and conclusions include the following aspects:(1)the stress-strain relationship and failure criterion of layered rock mass derived from principle of statistical mechanics of rock mass,along with the calculation program of rock mass mechanical parameters compiled by C# language,provides a new and reliable way to select the mechanical parameters in engineering practice.Furthermore,the accuracy of the theoretical formula of the relevant mechanical parameters and the reliability of SMRM program are verified on the basis of test data of the Linxi River Hydropower Station,(2)Due to the control effect of the joints in the layered rock mass,it has significant anisotropy characteristics.After a large number of program calculations,it is found that the increase of the joints density will exhibit the anisotropy characteristics and weakening of the layered rock mass.The change of the inclination will control the deformation and strength parameters of the rock mass;the deformation and strength characteristics of the layered rock mass will increase with the increase of the confining pressure,and the corresponding anisotropic characteristics will gradually weaken until it disappears completely.(3)A series of cylindrical test models were established by MIADAS modeling software and numerical simulation analysis was carried out in FLAC3 D.According to the monitoring data obtained from the simulation software,it can be seen that the strength parameters will increase with the inclination of the structural plane;and the increase of the density of the structural surface and the decrease of the confining pressure will lead to the weakening of parameters such as rock deformation and strength.(4)Depending on the theoretical analysis and the numerical simulation of the anisotropic variation law,in the case of Zhifang tunnel of the Sichuan-Yunnan Railway in Northwest China,the reinforcement method of the layered surrounding rock tunnel is proposed.The reinforcement method can strictly control the non-uniform deformation and anisotropic characteristics,so that the secondary lining of the tunnel can be smoothly carried out,which is suitable for the design and construction of surrounding rock of various types of layered tunnels.