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应力–渗流耦合下含裂隙砂岩力学特性研究

Study on mechanical properties of fractured sandstone under stress-seepage coupling conditions

  • 摘要: 随着资源开采深度增加, 高应力、高渗透压和工程扰动对岩石的力学行为影响更为复杂, 尤其是复杂环境下形成的裂隙岩石, 其力学行为关系到工程安全。针对深部资源开采工程中常见裂隙发育的含水层砂岩, 通过室内力学试验模拟裂隙形成应力过程, 制备了能够反映裂隙形成应力环境的含裂隙砂岩, 并对其开展应力–渗流耦合试验, 揭示含裂隙砂岩变形、强度及渗透特征, 结果表明: 含裂隙砂岩的变形和强度均表现出显著的围压强化效应和水压弱化效应, 在低渗透压条件下, 含裂隙砂岩的抗剪强度由黏聚力c和内摩擦因数f共同提供, 而随着渗透压升高, 抗剪强度仅由内摩擦因数f提供; 渗透率随围压升高呈降低趋势, 随渗透压升高呈指数函数增大的规律; 同时考虑围压和渗透压的影响, 提出了在围压σ3≤16 MPa, 渗透压Pw≤15 MPa条件下含裂隙砂岩弹性模量随围压和渗透水压变化的预测模型。

     

    Abstract: With the increase of mining depth of resources, the influence of high stress, high pore pressure and engineering disturbance on the mechanical behavior of rocks is more pronounced. This is particularly true in fractured rock formed under complex conditions, affecting the engineering safety. Focusing on fracture-developed aquifer sandstone commonly encountered in deep resource extraction, laboratory tests were conducted to simulate the stress process of fracture formation. Fractured sandstone specimens replicating the in-situ fracture-forming stress environment were prepared. Stress-seepage coupling tests were then performed on these specimens to investigate their deformation, strength, and permeability characteristics. The results show that both the deformation and strength of the fractured sandstone exhibit significant confining pressure strengthening effects and water pressure weakening effects. Under the low seepage pressure, the shear strength of fractured sandstone is determined by cohesion c and internal friction coefficient f, while with the increase of the seepage pressure, the shear strength is mainly determined by the internal friction coefficient f only. The permeability decreases with the increase of the confining pressure and increases exponentially with the increase of the seepage pressure. Considering the influence of confining pressure and seepage pressure, a prediction model of elastic modulus of the fractured sandstone is proposed under the conditions of σ3≤16 MPa and Pw≤15 MPa.

     

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