热-力耦合作用下岩石破裂过程的近场动力学-有限元耦合数值模拟

NUMERICAL SIMULATION OF ROCK RAPTURE PROCESSES UNDER THERMO-MECHANICAL COUPLING USING THE HYBRID PERIDYNAMIC AND FEM MODEL

  • 摘要: 热冲击导致的岩石破裂现象常出现于地热和油气资源开发、深部矿物开采和地下核废料处置等岩石工程中,研究其破裂机制对指导资源的高效、安全开发和进行工程结构稳定性评价具有重要意义。近场动力学方法是一种热门的非局部数值理论,克服了传统连续介质力学理论在求解破裂问题时的奇异性与网格依赖性缺点,十分适合模拟材料破坏与断裂问题;但其非局部特性也导致了模型求解计算量较大的缺陷。为了减少计算量,该文介绍了一种近场动力学与有限元耦合计算模型,用于模拟岩石在热-力耦合作用下的变形和破坏行为。对含预制裂纹平板的热传导问题进行了模拟,验证模型描述裂纹导致的温度场不连续现象的有效性和精确性;对端部受到低温冲击的高温弹性平板变形问题进行模拟,采用不同离散参数对耦合模型的收敛性进行分析,为离散参数的选取提供了定量依据;对不同初始温度的高温岩石试件受到单边低温冲击的破裂过程进行了模拟,初始温度为200 ℃的模拟结果与唐世斌等的模拟结果很吻合,进一步验证该模型模拟热-力耦合作用下的岩石破裂问题的准确性。对比不同初始温度下岩石破裂过程的模拟结果发现:随着初始温度的升高,在相同的边界低温冲击下,热应力引起的裂纹数量显著增多,该现象与淬火试验中观测的规律相同,说明该耦合模型可合理模拟热冲击作用下的岩石破裂过程。该文的工作为使用数值模拟手段研究岩石在热-力耦合作用下的破坏过程提供了新方法。

     

    Abstract: Thermal shock induced fractures often occur in rock mass in the projects of geothermal, of oil and gas resource development, of deep mineral mining and, of underground nuclear disposal. Study on its rupture mechanism is of great significance for guiding the efficient and safe development of resources and for evaluating the stability of engineering structures. The Peridynamics (PD) method, a widely used non-local numerical approach in recent years, addresses the singularity and mesh-dependency issues inherent in traditional continuum mechanics when solving fracture problems. It is particularly well-suited for simulating material failure and fracture. Due to its non-local nature, PD involves a relatively high computational cost. To mitigate this computational burden, this study presents a hybrid Peridynamic/Finite element model (PD-FEM) for simulating the deformation and failure behavior of rocks under thermo-mechanical coupling effects. The heat conduction problem of a pre-cracked plate is simulated, verifying the effectiveness and accuracy of the model in describing the discontinuity in the temperature field. The deformation of a high-temperature elastic plate subjected to low-temperature impact at the ends are solved. Convergence analysis is performed to provide quantitative criteria for the selection of discretization parameters. The rupture phenomena in high-temperature rock specimens with different initial temperatures subjected to unilateral low-temperature impact are simulated. The numerical results with initial temperature of 200 ℃ agree well with those reported by Tang et al., further verifying the capability of the model in simulating fracturing in rocks under thermo-mechanical coupling. The comparison of results for rock fracture at different initial temperatures shows that as the initial temperature increases, the number of cracks caused by thermal stress significantly increases under the same boundary low-temperature impact. This observation is consistent with the findings observed in quenching experiments, demonstrating the accuracy of coupled model in simulating the rock fracture process under thermal shock. This work provides a novel method for studying rock failure processes under thermo-mechanical coupling through numerical simulations.

     

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