Study On Strength Parameters Of Mixed Rock Mass

The random distribution of joint fissures inside rock mass is an important reason for the uncertainty of rock mass strength,and the determination of rock mass strength is the basis of rock mass engineering design.In this paper,the mixed rock slope of the southwestern part of the Dagushan Iron Mine is taken as the research object.The indoor test,particle flow numerical analysis and Hoek-Brown strength criterion are used to explore the method of quantifying the strength of jointed rock mass.The main research results as follows:(1)Based on the indoor single and triaxial compression tests,the mechanical properties of the mixed rock are analyzed from three aspects: strength,deformation and macroscopic failure characteristics.The results of single and triaxial compression tests show that the mechanical parameters of the mixed rock have a certain degree of dispersion.The Mohr-Coulomb strength criterion is used to obtain the cohesive force of the mixed rock c = 14.01 MPa and the internal friction angle ? = 45.35 °.The failure mode of rock has a certain relationship with the confining pressure.With the increase of confining pressure,the failure mode of mixed rock is gradually changed from tensile failure to tensile shear failure.(2)Based on the principle of orthogonal experiment,32 sets of numerical experiments of different meso-mechanical parameters were designed,and the degree of influence of meso-mechanical parameters on macro-parameters was discussed;combined with the BP neural network,mixed rock macros under complex stress conditions were established.An inversion model of mechanistic parameters and verified the reliability of the inversion model.(3)The results of field joint investigation show that there are two groups of dominant joints in the survey area,the occurrence of joints follow normal distribution,and the joint spacing,linear density and trace length follow lognormal distribution.A 3D joint network model of migmatite rock mass is established by 3D joint network simulation technology.(4)Based on Hoek-Brown strength criterion,the GSI value of the jointed rock mass in the footwall of Dagushan Iron Mine is 58.7,and the strength of jointed rock mass of migmatite in the footwall of Dagushan Iron Mine under different disturbance coefficients is given.(5)The triaxial numerical model of jointed migmatite rock mass is established by PFC3 D.The strength of jointed rock mass under different confining pressure conditions is analyzed and compared with the strength of jointed rock mass estimated by Hoek-Brown strength criterion.The results show that the strength of jointed rock mass is the closest when the number of numerical results is 0.6 and the overall error is small.It is determined that the cohesive force of the mixed rock mass is 6.53 MPa and the internal friction angle is 31.96 °.