摘要
The addition of basement beneath existing building changes the underpinning pile from fully embedded to partially embedded,and thus influences the mechanical properties of pile.In the past,scholars paid attention to the change in the bearing capacity of pile but neglected the difference of dynamic characteristics before and after construction,and potential changes in stress history of remaining soil are also ignored.In this work,a calculation model is built to investigate the influence of excavation on dynamic impedance of underpinning pile considering the effect of stress history.The soil is simulated by the dynamic Winkler foundation,which is characterized by springs and dashpots.Properties of remaining soil after excavation are updated to consider the effect of stress history through modifying the initial shear modulus and related parameters.The dynamic impedance of pile after excavation is obtained based on the transfer matrix method.The parameter study is carried out to evaluate the dynamic impedance with various excavation depths,considering or ignoring stress history effect,and various element lengths.The results show that shallow soil plays an important role to dynamic impedance,and overestimated dynamic impedance is obtained if not considering the stress history effect.
在既有建筑物下增设地下室会使得托换桩从完全埋入状态变为部分埋入状态,从而改变桩基的力学性能。过去学者们主要研究桩的承载力变化,而对施工造成的动力特性变化关注较少,也没有考虑土体开挖造成深层土的应力历史变化。本文建立了能够考虑应力历史效应的开挖后桩基动力阻抗计算模型,并研究了土体开挖的影响。在动力Winkler地基上用弹簧和阻尼器模拟土体。通过计算初始剪切模量和其他相关参数,对开挖后残余土体的力学参数进行修正,以考虑应力历史的影响。基于传递矩阵法获得了开挖后桩的动力阻抗。随后对开挖深度、应力历史以及分段长度等参数进行了分析。结果表明,浅层土体的约束作用对动阻抗起到了重要作用,如不考虑应力历史可能会高估动力阻抗。
作者
LIANG Fa-yun
CAO Ping
QIN Hong-yu
梁发云;曹平;秦红玉(Department of Geotechnical Engineering,Tongji University,Shanghai 200092,China;College of Science and Engineering,Flinders University,Adelaide 5001,Australia)
基金
Projects(51878487,41672266)supported by the National Natural Science Foundation of China。
