MECHANICAL PROPERTIES AND FAILURE MODES OF COMPOSITE ROCK MASS CONSIDERING UNCOORDINATED DEFORMATION

This paper aims at the uncoordinated deformation phenomenon of composite rock mass in metal mine contact zone. It carries out the uniaxial compression test of physical similar samples. It studies the influence of the difference of mechanical properties of different media on the mechanical properties and failure modes of composite samples in combination with the theoretical analysis. The test results show that the uniaxial compressive strength(UCS) and elastic modulus of the composite samples are smaller than the larger values of UCS and elastic modulus of the two media. The reduction amplitude increases with the increase of the difference degree of the mechanical properties of the medium(λ). Meanwhile,with increase of the degree of difference(λ),the composite samples gradually change from single incline plane shear failure to complex lateral tensile failure. Theoretical analysis shows that the uncoordinated deformation at the contact surface is caused by the difference of Poisson ratio(Δv) in different media. The mechanical properties of composite samples are weaken by the formed lateral constraint stress. The correlation between the degree of uncoordinated deformation and Δv is quantified by introducing the uncoordinated deformation coefficient α. The expression of elastic modulus and axial stress-strain constitutive relation of composite samples determined by the mechanical parameters of two kinds of media was constructed. The results can provide a theoretical basis for further analysis of the uncoordinated deformation and failure of the contact zone composite rock mass.