Fig.10

Many researches have focused on deformation mechanism of fractured rock, but the destruction mechanics of bifurcated fractures with unstable structures were still unclear. A bifurcated fracture divides the rock sample into three parts, including the intermediate rock block and the two sides of the split fractures. Displacement tests were performed on rocks with bifurcated fractures to study the displacement forms and the damage characteristics of bifurcated fractures under confining pressure. Fracture change process of the rock has been suggested by theoretical equations. The results showed that the different structures and characteristics of the rock blocks on both sides of the bifurcated fracture caused the different bearing capacities. Rock blocks on both sides bent under confining pressure. When the confining pressure surpassed the bending limit of the rock block, the rock has undergone tensile failure. Tensile fracture is concentrated near the fracture intersection. Displacement of intermediate rock at the initial stage is mainly due to the closure of the rock block on both sides. After the rock bending fracture, fractured part contacted and extruded the intermediate rock block, which was subjected to a combination of normal and shear stresses. The proposed equation can well express the deformation of rock under pressure.