考虑扰动影响的地基非线性沉降分层总和分析方法

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摘 要：为预测工程地基土体沉降，针对受到施工扰动影响的地基土，基于扰动状态概念分别以抗剪强度和相对密实度为扰动参量建立扰动因子函数，从而提出能够考虑扰动影响的地基土修正Duncan-Chang模型.首先，考虑地基土实际应力状态，将地基土沉降变形视为由附加静水压力和附加偏应力引起的两部分变形之和，建立地基土沉降变形分析模型；其次，考虑地基土的应力历史并采用分级加载分析方法，给出了不同埋深地基土初始变形模量的确定方法；然后，基于虎克定律和修正Duncan-Chang模型并采用分级加载分析方法分别建立由附加静水压力和附加偏应力作用下的地基沉降变形计算模型，给出了考虑附加应力影响的地基土变形模量的确定方法；最后，将本文方法应用于工程实例并进行了沉降变形分析.研究结果表明：本文方法在反映地基土扰动程度、应力状态和应力历史等方面具有一定的优越性和可行性，其计算结果符合沉降预测规律.

关键词：地基沉降；分级加载；扰动；应力状态；应力历史

中图分类号：TU44 文献标志码：A

文章编号：1674-2974（2017）03-0113-07DOI：10.16339/j.cnki.hdxbzkb.2017.03.014

Abstract：For the ground foundation influenced by the construction disturbance， the disturbance factor functions taking the shear strength and relative density as the disturbed parameters， respectively， were proposed based on the disturbed state concept. By using this function， a modified Duncan-Chang model considering the influence of disturbance was developed to provide a reference for the settlements prediction of ground foundation. Firstly， considering the stress state of ground soil， the analytical model for ground soil was established by idealizing the ground settlement to be the summation of one part caused by additional hydrostatic pressure and the other part by additional deviatory stress. Secondly， considering the stress history of ground soil， the determination method for initial deformation modulus of ground soil at different depths was provided by using the step-loading analysis method. Based on the Hooke’s law and modified Duncan-Chang model， the models to evaluate the settlement of ground foundation caused by additional hydrostatic pressure and of that by additional deviatory stress were then developed， respectively， by using the step-loading analysis method. The determination method for deformation modulus of ground soil was also given considering the additional stress effect. Finally， the proposed method was applied to a practical project case， and the corresponding settlement analysis was carried out. The results show that the proposed method has superiority and feasibility in the aspects of reflecting disturbance degree， stress state and stress history. The calculated results agree well with the prediction rule of settlement.

Key words： foundation settlement； step-loading； disturbance； stress state； stress history effects

目前普遍采用傳统分层总和法[1]对地基沉降进行分析计算，但是如何准确反映工程地基实际沉降的问题一直未得到很好的解决.因为在施工过程中地基土体不可避免地会受到扰动，使得土体的变形和强度特性发生改变，若采用基于传统分层总和法即通过室内试验获取的土体物理力学参数来预测施工过程中及其后土体变形和强度等特性，则势必造成较大误差，因此，有必要对地基沉降分析即分层总和法作进一步研究.

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