In order to understand the time-dependent characteristics of stimulation behaviors during hydraulic fracturing, the self-developed hydraulic fracturing monitoring system under triaxial loading was employed to investigate the cracks' propagation under shale-fluid coupling process. The results reveal that with different duration of fracturing fluid invasion, the pressurization rate of fluid pressure and breakdown pressure (BP) value are obviously varied, and the tensile crack is the dominant crack type, the amounts of shear cracks change accordingly, as well as the failure mode's evolution includes radial split, oblique shear, and combination of oblique shear and radial split. Moreover, the stress regime evolution rules around the cracks are obtained based on the Mohr-Coulomb criterion. This investigation will provide theoretical support for the fracturing's implement in the field, also can be as the laboratory evidence for the interpretation of microseism induced by long-term hydraulic fracturing.

为了理解水力压裂过程中增产行为的时变特征，采用自行开发的三轴荷载作用下的水力压裂监测系统研究了页岩-流体耦合过程中裂缝的扩展。结果表明，随着压裂液侵入时间的延长，流体压力的升压速率和破裂压力（BP）值发生明显变化，拉伸裂缝为主要裂缝类型，剪切裂缝的数量也相应变化。破坏模式的演变包括径向分裂，斜向剪切以及斜向剪切和径向分裂的组合。此外，基于Mohr-Coulomb准则获得了裂纹周围的应力状态演化规则。