Numerical investigation on the fracture and mechanical behaviors of marble containing two parallel fissures under triaxial compression conditions using FDEM

This paper aims to investigate the fracture and mechanical behaviors of fissured marble under triaxial compression. The two-dimensional models of marble with two parallel fissures and various rock bridge angles were established, and then the numerical simulations considering the effect of confining pressure were performed with the finite-discrete element method. The brittle-ductile transition and stress multi-peak characteristics are presented with the increase of the confining pressure. The characteristic strain, stress, and elastic strain energy exhibit various trends with the increment of the rock bridge angle, whilst increasing trend with the increment of the confining pressure. The cohesion presents the variation of first increasing and then decreasing with the increase of the rock bridge angle, and the friction angle presents the opposite trend to the cohesion. The proposed strength model can reflect the evolutions of the cohesion and the friction angle considering the effect of confining pressure and rock bridge angle. The elastic strain energy has the trends of nonlinear increase and fluctuation in the pre-peak and post-peak phases, respectively. The variation of kinetic energy is induced by the internal local fracture during the progressive failure. The failure pattern transforms from the tensile failure to the shear failure with the increase of the confining pressure. The coalescence behavior of cracks at the rock bridge can be classified into four modes.