High Energy Gas Fracturing (HEGF) technology can produce self-supporting crack network in rocks of oil and gas reservoirs under a large number of high temperature and high pressure explosive shock wave caused by explosive detonation. It is expected that the reservoir conductivity will be improved by generating the new crack channels for oil and gas flow, so as to achieve the goal of increasing oil and gas production. However, the numerical study on the crack initiation, extension and propagation of rock under blast loading is still insufficient, which plays a vital role in better understanding the mechanical performance of rocks in the HEGF process. In the present study, taking the typical shale gas demonstration area in Sichuan province as an example, the shale crack model is established, the mechanical properties of shale rock with cracks under explosive loading are studied, the evolution laws of crack propagation are analyzed, and the damage characteristics of crack tip are considered.

Marine geological disasters, such as seabed liquefactions, submarine landslides, debris flows and turbidity currents, are all closely related to the accumulation of wave-induced excess pore pressure in the seabed. Due to the limitations of physical model experiment and in-situ observations, numerical analysis has become an important method to explore the microscopic mechanism of the accumulation of excess pore pressure. Based on the discrete element porous density flow method, we simulated the changing process of excess pore pressure in seabed sediment in this study, comparing with laboratory flume experiment. The simulation results reproduce the changing process of excess pore pressure in the laboratory flume experiment. The excess pore pressure occurs in the surface of seabed and gradually transfers to the deep layer, tending to a stable value. Thus, the discrete element porous density flow method is well suitable for simulating the accumulation of wave-induced excess pore pressure. Furthermore, the method constitutes a promising tool to study the microscopic mechanism of seabed liquefaction.

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