Study On Compressive Strength Of Fractured Rock Mass

The rock mass is composed of rock blocks and structural planes.Affected by the structural plane,the rock mass exhibits characteristics of heterogeneity,discontinuity and anisotropy.At the same time,due to the influence of tectonic stress and various environmental factors,an effective theory is urgently needed to determine its strength and deformation.Based on the theory of statistical rock mass mechanics and particle flow numerical simulation,this paper focuses on the strength of rock masses with multiple groups of randomly distributed fractures,and carries out engineering applications.The main research results and conclusions include:(1)Based on the statistical theory of fracture mechanics rock mass,the principal stress form of fractured rock mass is deduced.Through the strength criterion formula,it can be seen that the compressive strength of fractured rock mass is not equal to the compressive strength of rock mass.The compressive strength of the rock mass is controlled by the structural plane,and the minimum value should be taken among the strength of the rock block,the strength of the weakest structural plane and the tensile strength of the rock block.The mechanical properties of a fractured rock mass controlled by structural planes are mainly determined by the geometric and mechanical properties of the structural planes(distribution of structural planes,friction angle of structural planes,and cohesion of structural planes,etc.).(2)In this study,the macro-mechanical parameters of the rock block are determined by the PFC triaxial experiment,and the numerical rock mass model composed of the rock block and the joint plane is constructed on the basis of consulting related literature.Through the analysis of different confining pressures(2 MPa,5 MPa,8MPa,10 MPa and 13 MPa),the compressive strength of rock masses with multiple groups of random joints are found to drop sharply from more than 100 MPa in rock masses to 8.3 MPa,16.1 MPa,14.7 MPa,19.17 MPa and 20.32 MPa respectively.This obviously plays a key role in the structural aspect.In addition,it is found through comparison that the numerical calculation results are in good agreement with the theoretical calculation results,regardless of the compressive strength or the elastic modulus,and the average deviation is about 12.89% and 30.09%.The results verify the correctness of the theoretical formula of compressive strength of fractured rock mass.(3)The theory of fractured rock mass compressive strength is applied to the fractured rock mass of a certain slope in Hanshan Mountain Scenic Area,Shanlian Town.Using the geological compass to measure the occurrence of the structural surface of the slope,the rock samples collected in the field are classified and marked,and the friction angle of the structural plane is measured in the laboratory.On the basis of processing a large number of measured data,the anisotropic behavior of the compressive strength and elastic modulus of the rock mass is analyzed by theoretical calculation and rock mass engineering software,and the feasibility of the theory of the compressive strength of fractured rock mass in engineering is verified.