岩体水力压裂应力-渗流耦合近场动力学模拟

Peridynamics Simulation of Stress-Seepage Coupling in Hydraulic Fracturing of Rock Mass

摘要:

裂隙岩体应力-渗流耦合机制是油气开采、地应力测量与地质灾害防控等岩土工程活动的理论基础。基于近场动力学非局部作用思想提出了物质点双重覆盖理论模型，通过将近场动力学在模拟固体材料变形损伤与地下水渗流两方面的优势相结合，采用“混合”时间积分方案，构建了流体压力驱动条件下裂隙岩体应力-渗流耦合的常规态型近场动力学模拟方法，并将其应用于空心圆柱体注水试验模拟，揭示了水力裂隙起裂、扩展和贯通的作用机制，通过与室内试验及传统数值方法计算结果对比验证了模拟方法的有效性。模拟结果显示，空心圆柱体注水试验过程中岩体的变形和破坏完全是由水力驱动的，水力裂隙的产生是随机的，不需要指定裂隙扩展路径，并且水力压裂过程中致使试件破裂的能量存在积蓄-释放过程，应用近场动力学方法可以较好地捕捉该现象。

Abstract:

The stress-seepage coupling mechanism of fractured rock mass is the theoretical basis of geotechnical engineering activities such as oil and gas exploitation， in-situ stress measurement， and geological hazard prevention and control. In this paper， based on peridynamics nonlocal effects， a material points double repeat cover theoretical model was proposed. Combining the advantages of peridynamics in simulating the solid material deformation and damage and groundwater seepage， a peridynamics simulation method of fluid pressure driven stress-seepage coupling in fractured rock mass was established by using a hybrid time integration scheme and applied to the simulation of water injection test of hollow cylinder to reveal the mechanism of initiation， propagation， and connection of hydraulic fractures. The effectiveness of the simulation method was verified by comparing the results of laboratory tests with traditional numerical methods. The simulation results show that the deformation and failure of rock mass in the hollow cylinder water injection test are completely driven by hydraulic power， and the generation of hydraulic fractures is random. Therefore， there is no need to specify the fracture propagation path. In addition， the energy causing the fracture of the specimen in the process of hydraulic fracturing has a process of accumulation and release， which can be well captured by peridynamics.