基于沉降控制的竖向下压循环荷载作用下的桩基设计方法

Design method for piles subjected to cyclic axial loading for control of permanent accumulated settlement

低幅值、大周次竖向循环荷载作用下桩基发生累积沉降及承载力弱化,影响到风机塔架、高速铁路路基等沉降敏感结构物的服役性能。首先总结了竖向循环荷载作用下桩基设计要求及若干设计关键问题。基于模型试验结果,分析了竖向循环荷载作用下的桩基承载力和累积沉降演化规律;定义了3种桩顶累积沉降发展模式及对应的循环荷载比和静荷载比组合,建立了桩基循环累积沉降分析图,提出了组合循环荷载作用下的桩基循环加载性状简化判定公式。提出了针对竖向循环荷载作用下桩基的设计方法及设计流程,并给出了设计实例。

The pile capacity degrades and the permanent settlement of pile accumulates when the pile is subjected to low-amplitude and long-term axial cyclic loading. The degradation of the pile capacity and the permanent accumulated settlement of the pile will greatly influence the service ability of settlement-sensitive superstructures, such as high-speed railway tracks, wind turbines and so on. The general design requirements of piles under cyclic axial loading and the key issues that are of great interest to the designers are introduced. The behaviors of piles under axial cyclic loading are presented and the main factors influencing them are discussed. The definitions of load ratios are given. The criteria for assessing pile response based on the limit cyclic loading ratio are proposed. The idea of a cyclic interaction diagram is developed. The design method and procedure for piles under cyclic axial loading are proposed. Finally, a case is given to verify the proposed design approach.