A micro-macro model of pore pressure effect on shear fracture in brittle rocks under compression

A micro-macro model is presented for predicting the high pore pressure effect on shear failure properties of brittle rocks under triaxial compressive loadings. This model is established by the use of the improved microcrack growth model considering the pore pressure effect, the established micro-macro damage relation, and the Mohr-Coulomb failure model. The improved model of microcrack growth introduces the pore pressure weakening effect on the normal stress acting on the initial crack plane and the pore pressure strengthening effect on the tensile force acting on the newly generated wing crack surface. The reasonability of suggested stress-strain curves under different pore pressures is verified by comparing with the experimental results. The influences of pore pressure and confining pressure on the axial peak strength, axial peak strain, shear failure plane angle, shear strength, cohesion, and internal friction angle are discussed. The peak compressive strength, peak axial strain, peak crack length, shear failure plane angle, shear strength, cohesion, and internal friction angle all descend nonlinearly with an increment of pore pressure.

Automated summary

A micro-macro model is proposed to predict the effect of high pore pressure on shear failure properties of brittle rocks under triaxial compressive loadings. The model takes into account the pore pressure effect on microcrack growth, and combines the damage relation and the Mohr-Coulomb failure model. The results show that both pore pressure and confining pressure significantly influence the axial peak strength, axial peak strain, shear failure plane angle, shear strength, cohesion, and internal friction angle of the rocks, all of which decrease non-linearly with increasing pore pressure.