桩间距对桩筏基础结构性能影响的模型试验研究

MODEL TEST STUDY OF STRUCTURAL PROPERTIES OF PILED-RAFT FOUNDATION AFFECTED BY PILE SPACING

为研究桩间距对桩筏基础结构性能的影响,设计并进行不同桩间距的桩筏基础系列模型试验。结果表明,设置不同的桩间距可调配群桩基础中桩与筏板的分担作用,调整桩筏基础的受力性能。常规桩距桩筏基础以桩为承载主体,地基土的荷载分担次之;当桩间距大于6倍桩径后,桩较早进入塑性支承状态,地基土分担荷载能力增强,桩与筏板荷载分担的主次作用发生转换,筏板逐渐转换为基础的承载主体。随着桩间距增大,筏板内力分布由整体弯曲过渡到以局部弯曲为主。桩筏基础桩顶荷载分布规律受桩间距的影响,随着桩间距增大,桩顶荷载由角桩最大逐渐转化为中间桩最大。建议桩筏基础设计方法应考虑桩间距设置对筏板与桩土体系相对刚度、筏板内力和桩顶荷载不均匀特征的影响。

In order to study the influence of pile spacing on the structural properties of piled-raft foundation, model tests of piled-raft foundation with different pile spacings had been investigated. The results indicate that the effect of loading share ratio between pile and subsoil could be adjusted by different pile spacings. Then the mechanical properties of piled-raft foundation are regulated. The piles are mainly bearing body of piled-raft foundation being in conventional pile spacing, and the subsoil takes the second place. As the pile spacing is over 6 times of pile diameter, the shared-load effect of subsoil increases; piles go at plastically bearing capacity status earlier. Then the raft becomes the main bearing body of piled raft foundation as loading increases. With pile spacing increasing, the internal force distribution properties of raft transfer from wholly bending status to locally bending status. The uneven loading distribution regulation on pile-raft tops is affected by pile spacing. The maximal loading of pile under raft transfers from comer pile to middle pile with the pile spacing increasing. It is suggested that the effect of pile spacing on relative stiffness of raft-pile-soils and mechanical properties of piled raft foundation, such as raft bending moment and uneven distribution characteristics of piles loading, should be considered in design of piled-raft foundation.