桩长对桩-土复合地基变形稳定性的影响

Effect of pile length on deformation stability of pile-soil composite foundation

摘要

桩基是大型建筑物和基础设施的基础部分，其安全性能直接影响到整个结构的安全性。采用数值分析方法构建三维桩-土体模型，模拟其在不同荷载作用下的力学响应，分析了地基沉降行为、桩身轴向应力分布及桩土应力比的变化规律。结果表明：(1)随着桩长度的增加，桩顶沉降量呈现递减趋势，尤其当桩长达到33.4 m并嵌入到承载力较强的泥岩层时，桩端嵌固效应显著增强，导致桩顶沉降减少。筏板中心点沉降与桩顶面沉降的差异随桩长增加而增大，揭示了褥垫层的重要荷载调节作用。(2)桩长较短时，轴向应力最大值位于桩顶下方一定距离处，并随着荷载增加而沿桩身扩散；而对于较长的桩，桩底轴向应力较大，且最大轴应力点随荷载增加逐渐上移。当桩端嵌入强风化泥岩层中时，轴应力分布呈“W”形模式，反映了桩端与岩石间嵌固效果的重要性。(3)随着桩长增加，桩基在较大荷载下仍能保持较高的承载能力，但超过一定阈值后，其增长速率逐渐减缓，表明桩基承载能力存在上限。

Abstract

Pile foundation is the foundation part of large buildings and infrastructure, and its safety performance directly affects the safety of the whole structure. In this paper, a three-dimensional pile-soil model is constructed by numerical simulation to simulate its mechanical response under different loads. The settlement behavior, axial stress distribution of pile body and the change law of pile-soil stress ratio are analyzed. The result show that:(1) With the increase of pile length, the pile tip settlement shows a decreasing trend, especially when the pile length reaches 33.4 m and is embedded into mudstone layer with strong bearing capacity, the pile tip embedding effect is significantly enhanced, resulting in a decrease in pile tip settlement. The difference between the settlement of raft center point and pile top surface increases with the increase of pile length, which reveals the important load regulation function of mattress layer.(2) When the pile length is short, the maximum axial stress is located at a certain distance below the top of the pile, and spreads along the pile body with the increase of load; For longer piles, the axial stress of pile bottom is larger, and the maximum axial stress point gradually increases with the increase of load. When the pile end is embedded in the strongly weathered mudstone layer, the axial stress distribution shows a “W” shape pattern, which reflects the importance of the embedment effect between the pile end and the rock.(3) With the increase of pile length, pile foundation can still maintain a high bearing capacity under large loads, but its growth rate will gradually slow down after exceeding a certain threshold, indicating that there is an upper limit of the bearing capacity of pile foundation.

关键词

桩-土相互作用 / 桩长 / 数值模拟 / 荷载 / 位移

Key words

pile-soil interaction / pile length / numerical simulation / load / displacement

Author summay

张庆传(1990—), 男, 高级工程师, 副总经济师, 学士, 从事工程项目管理、造价管理及相关研究。E-mail: [e-mail]

基金资助

湖南省重点研发计划(2022SK2082)

国家自然科学基金项目(42277175)