Multi-peak deformation behavior of jointed rock mass under uniaxial compression: Insight from particle flow modeling

• Rock mass has multi-peak deformation behaviors related to joint configurations.
• Joint strength mobilization dominates multi-peak deformation behavior of rock mass.
• A method is proposed to study nonlinear response of rock mass by smooth joint model.

Evaluation of mechanical properties of jointed rock mass is very important for geological engineering problems related to underground opening, slope stability, dam foundation and hydraulic fracturing, etc. It is generally known that both strength and deformability of rock mass may change with joint geometry and arrangement. By PFC (Particle Flow Code) modeling, this paper aims at understanding the damage mechanism of the multi-peak deformation behavior of jointed rock mass with different joint orientations and continuity factors under uniaxial compression observed in the physical model tests. With the smooth joint contact model, not only has the inherent roughness in conventional joint model been avoided, but also we can monitor the joint aperture, number of closed joints, and forces acting on the joints during the damage process. It is shown that mobilization of joint strength plays an important role in the multi-peak deformation behavior of rock mass. If the joint strength is slightly mobilized or immobilized (i.e., most joints keep open) during the test, strain softening occurs. However, if the joint strength is significantly or fully mobilized, yielding platform or strain hardening may happen.