桥梁桩基周围形成局部冲刷坑时会导致桩基有效埋深减小，增大工程结构的安全隐患。目前研究的冲刷坑模型多为对称形态，而工程实际中的冲刷坑多为非对称形态，使得桩基处于更不利状态。合理计算桩周形成非对称冲刷坑后土体的应力变化是评价桩基承载力的关键之一，目前尚没有严格的理论计算方法。针对该问题，根据试验实测的非对称冲刷坑形态提出了三维非对称冲刷坑的简化模型。将冲刷坑最大深度以上土体重度看做荷载并基于Boussinesq点荷载方程在半无限空间中的应用，推导得到了非对称局部冲刷坑内土体垂直及水平有效应力计算方法。采用有限元中“生死单元法”模拟了半无限空间地基中冲刷坑的形成，并将有限元计算结果与理论计算方法所得结果进行对比，验证了理论计算方法的正确性。基于理论计算方法考虑了冲刷坑内存在桩基的影响，并与有限元计算结果进行了对比，对比结果表明了理论计算方法的可行性。在此基础上，设计了一系列工况，对三维非对称冲刷坑简化模型中的参数进行了敏感性分析，得到了非对称冲刷坑条件下桩周土体的垂直及水平有效应力差的变化规律。

When the local scour hole is formed around the pile foundation, the effective buried depth of the pile foundation will be reduced, which increases the safety hazard of the engineering structure. The scour models in the current research are mostly symmetrical, but the scour holes in engineering practice are asymmetric, which makes the pile foundation in a more unfavorable state. How to calculate the stress change of the soil caused by scour reasonably is pivotal for evaluating the bearing capacity of the pile foundation. However, there is still no strict theoretical calculation method. This paper aims to propose a simplified three-dimensional asymmetric scour hole model based on the asymmetric scour hole shape measured in the experiment. Which is based on the application of Boussinesq's equation in a semi-infinite space and regard the soil above the depth of the scour hole as a load. The calculation method of the vertical and horizontal effective stress of the soil in the asymmetric scour hole is derived. The "active and deactive element" in the finite element method is used to simulate the formation of scour holes in the semi-infinite space foundation, and the FEM results are compared with those obtained from the theoretical calculation method, which verifies the correctness of the theoretical calculation method in this study. Subsequently, based on the theoretical calculation method, the influence of the pile foundation is considered, and compared with the FEM results. The comparison results indicate that the theoretical calculation method in this research is feasible. Based on this, the sensitivity analysis of the parameters in the simplified model of the three-dimensional asymmetric scour hole was carried out, and the changes of the vertical and horizontal effective stress difference of the soil around the pile under the condition of the asymmetric scour hole were obtained.

TU473.1

国家自然科学基金（51978105）；重庆市技术创新与应用发展专项面上项目（cstc2019jscx-msxmX0107）