王增亮 周航 丁选明 吴岱峰 蔡汝一 肖治微

摘 要：橋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，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，但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，推导得到非对称局部冲刷坑内土体垂直及水平有效应力。采用有限元中“生死单元法”模拟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方法计算结果进行对比，验证了理论计算方法的正确性。基于理论计算方法，考虑了冲刷坑内桩基的影响，并与有限元计算结果进行对比，对比结果验证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敏感性分析，得到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。

关键词：局部冲刷;应力计算;非对称冲刷坑;简化模型;Boussinesq解

Abstract： 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 hole models in the current research are mostly symmetrical， while the scour holes in engineering practice are mostly 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 at present. This paper aims to propose a simplified three-dimensional asymmetric scour hole model based on the asymmetric scour hole shape measured in the experiment. The soil weight above the maximum depth of the scour hole is regarded as a load and is based on the application of Boussinesqs equation in a semi-infinite space. The calculation method of the vertical and horizontal effective stress of the soil in the asymmetric local scour hole has been derived.The "dead-live unit method" in the finite element method is used to simulate the formation of scour holes in the semi-infinite space foundation. Andthe finite element calculation results are compared with those obtained by the theoretical calculation method， which verifies the correctness of the theoretical calculation method.Subsequently， based on the theoretical calculation method， the influence of the pile foundation in the scour hole is consideredand compared with the FEM results. The comparison results indicate that the theoretical calculation method in this research is feasible. On this basis， a series of working conditionshas been designed， and the sensitivity analysis of the parameters in the simplified model of the three-dimensional asymmetric scour hole are carried out. Through the analysis， the change law of the vertical and horizontal effective stress difference of the soil around the pile under the condition of the asymmetric scour hole is obtained.

Keywords： local scour; stress calculation; asymmetric scour hole; simplified model; Boussinesq solution

桥梁作为供公路、渠道、铁路、管线等跨越库区、山谷、河流等其他交通线最常用的工程结构，在经济建设和社会发展中发挥着举足轻重的作用。……