软粘土和硬粘土中水平多向受荷桩的工作性状研究

Laterally loaded piles have been widely used in the structures such as harbor wharfs, offshore oil platform and foundations for offshore wind turbines, part of which are embedded in sites consisting of clay. In the last fifty years, extensive research has been performed on the behavior of laterally loaded piles in clay. However, most of the research considered the lateral loading along one horizontal direction only, and neglected the multidirectional characteristics of some lateral loads. Our previous study shows that the lateral resistance of pile in sand is lower under the multidirectional lateral paths than under the unidirectional lateral paths. It has been also observed that the direction of the force increment vector is generally non-coaxial with the direction of the displacement increment vector under the multidirectional paths.The results from tests with the laterally loaded pile embedded in the medium-stiff clay indicate that the cyclic degradation of resistance is more significant under the multidirectional loading than under the unidirectional loading. This project will focus on the influence of the multidirectional paths on the pile lateral resistance in clay, and cyclic degradation of the resistance under the multidirectional cyclic lateral loadings. Mechanism for multidirectional clay-pile interaction will also be studied through numerical analyses. Finally, a multidirectional elasto-plastic p-y model, which can take into account the clay-pile interaction under both the monotonic and cyclic lateral loadings, will be proposed and verified.

水平受荷桩在港口码头、海洋采油平台和海上风机基础等构筑物中广泛应用，而且相当一部分位于粘土场地中。近五十年来，国内外研究者和工程人员对粘土中水平受荷桩的研究主要集中在单向水平荷载下的桩基响应方面。申请人前期的研究表明，砂土中的单桩在多向加载条件下的水平承载力要显著低于单向加载条件下的水平承载力，且存在荷载增量矢量与位移增量矢量非共轴等现象；而中硬粘土中水平受荷单桩的初步试验研究表明，在多向循环加载路径下的水平承载力退化更为显著。本项目将对粘土中水平多向受荷桩的工作性状进行较系统的研究：（1）通过室内模型试验，研究多向加载路径对软粘土和硬粘土中桩基水平承载力和桩身响应的影响，及水平多向循环加载路径下的承载力退化规律；（2）借助数值分析手段，进行水平多向荷载作用下粘土与桩相互作用的机理分析和参数研究；（3）建立并验证能描述在单调和循环水平多向荷载作用下，粘土与桩相互作用的弹塑性多向p-y模型。

水平受荷桩在港口码头、桥梁基础、海洋采油平台和海上风机基础等构筑物中广泛应用，而且相当一部分桩基位于粘土场地中。波浪荷载、风荷载或地震荷载联合作用产生的水平荷载通常具有多方向性的特点。本项目基于室内模型试验、三维有限元数值分析和理论分析，研究了：（1）不同水平多向单调加载路径下粘土中单桩的响应研究；（2）粘土中单桩在单向循环加载后，沿不同水平方向加载后的响应研究；（3）水平多向循环荷载作用下粘土中单桩的响应研究；（4）粘土场地中水平单向和多向受荷单桩和群桩的响应研究（数值研究）；（5）水平多向荷载作用下粘土与桩相互作用的弹塑性多弹簧p-y模型。项目研究成果揭示了多向加载路径对软粘土和硬粘土中桩基水平承载力和桩身响应的影响，以及水平多向循环荷载作用下桩基承载力的退化规律；建立和开发了适用于粘土与桩多向相互作用的多弹簧p-y模型，并编制了可用于水平单向和多向荷载作用下粘土中桩基响应分析的计算程序。.依托本研究项目发表学术论文共15篇，申请发明专利共8项（含美国专利2项），获批发明专利3项，实用新型专利4项。