Effect of Low Pore Pressure Zone at Crack Front on Rock Fracture Toughness Available to Purchase

In rock mechanics pore pressure is a crucial factor and many researchers have considered the influence of uniform pore pressure on fracture toughness. However, few studies concentrate on the influence of non-uniform pore pressure on fracture properties. A three-point bend test device that can independently control the pore pressure and confining pressure is designed and manufactured. Three-point bending tests are performed on homogeneous rock specimens under different pore pressure conditions, and a 2D fluid-solid coupling FEM model is also established. Crack opening displacement measured by LVDT and strain distribution at the crack tip monitored by DIC are used to verify and calibrate the established finite element model and the distribution of non-uniform pore pressure near the tip is obtained during crack propagation. The results show that there is a low pore pressure zone at front of the crack tip during rock fracture process; and this low-pore pressure zone causes a non-uniform pore pressure distribution near the crack tip, causing the rock mode I fracture toughness larger than that of a uniform pore pressure mode I fracture. The increase in the mode I fracture toughness is positively correlated with the pore pressure gradient in the low pore pressure zone.