花岗岩卸荷损伤演化及破裂前兆试验研究

Experimental Study on Damage Evolution and Fracture Premonition of Granite

采用双轴伺服试验系统,开展花岗岩卸荷试验,借助RFPA3D-Engineering数值模拟软件和声发射监测技术对花岗岩卸荷损伤演化及破裂失稳过程进行深入研究。研究结果表明,花岗岩卸荷损伤可分为弹性变形阶段和塑性变形阶段,弹性变形阶段有小尺度裂纹产生,塑性变形阶段岩石内部裂纹不断扩展、贯通,最终形成大尺度裂纹导致岩石破裂;根据花岗岩卸荷损伤过程中声发射事件率、能量变化特性,可将声发射事件率平静期和能量的快速释放作为岩石破裂失稳前兆。花岗岩卸荷损伤演化过程中,轴向应力边界与卸荷边界相交处易出现破裂区域,并最终形成"V"形宏观破裂带,整个过程以剪切破坏模式为主。

The granite unloading tests were carried out by bi- axial servo test system. With the help of RFPA3^-Engineer- ing numerical simulation software and AE monitoring tech- nology, the evolution of the unloading damage and the process of fracture instability were studied on granite. The results showed that granite unloading damage could be divid- ed into elastic deformation and plastic deformation stages. E- lastic deformation stage produced small-sized cracks. In the plastic deformation stage, the cracks expanded and penetra- ted to the large-scale crack, and eventually caused rock frac- ture. According to the AE events rate and energy change in the process of unloading, the quiet period of AE events rate and the fast release of energy were regarded as the failure premonition of granite. During the damage evolution of gran- ite unloading, the interface between the axial fixed stress boundary and the unloading boundary were prone to rupture, and eventually formed ＂ V＂ shape of macroscopic rupture zone. The whole process mainly presented shears failure mode.