含裂隙充填节理岩体的压剪断裂机制研究

Joints and weak layers are the key factors for possible rock mass failure or sliding, within which the heterogeneous infilled materials in joints strongly influence the shear mechanical behavior of rock mass and then its shear failure. Considering the effect of crack in infilled materials on the fracture characteristic of pre-existing jointed rock mass under compression-shear stress state, mortar infilled jointed rock mass specimens including various artificial lengths were prepared, and uniaxial compressive tests were carried out to investigate their compression-shear fracture mechanisms and the effect of pre-cracks sizes on fracture modes and fracture energy of jointed rock mass. The experimental results show that: (1) under uniaxial compression, the failure process of infilled jointed rock mass can be divided into two stages: fracture stage and friction stage. The former was the process of initiation, propagation and coalescence of cracks. The load bearing capacity was rapidly reduced after the peak load, and then gradually increased due to the increasing friction force. Finally, it failed when the shear stress reached its shear strength. (2) With the increasing pre-existing crack length in infilled jointed rock mass, the peak load of specimens was decreased linearly, while the fracture process was more brittle. (3) For the infilled jointed specimens without pre-crack, multiple micro-cracks were generated throughout the infilled joint during the fracture. However, for the pre-cracked specimens, they cracked from the tips and propagated to the adhesive surface of infilled mortar and joint. The stress-induced cracks concentrated with relatively low density in the infilled joint. (4) The volume of ligament in joint V _jc was used to modify the formula of fracture energy G _f-V . Based on the fracture mechanism of the infilled joint, the front boundary effect model, whose local fracture energy g _f-V was bilinear distribution along the ligament, was proposed. It explained the reason why the average fracture energy G _f-V decreased with the increasing of pre-crack length, and then it was well verified by the experimental data.