层状各向异性固结流变软土中桩筏基础的时变行为研究

The natural saturated soft soil is widely distributed in coastal areas and areas near rivers or lakes of our country, which is characterized by stratified, anisotropic and other complex features. This subject is aimed at studying the consolidation-rheology coupling effect of anisotropic saturated soft soils as well as the time-dependent behavior of the piled raft foundation and the layered anisotropic saturated soft soils according to theoretical derivations, numerical analyses and centrifuge modeling investigations, and it covers the following researches: (1) Based on the Biot consolidation theory, the classical viscoelasto and viscoelasto-plastic model and laboratory experiments, the viscoelastic and viscoelasto-plastic consolidation and rheology models for the three-dimensional anisotropic saturated soft soils are built. (2) With the application of extended precise integration method and finite element method, the viscoelastic and viscoelasto-plastic layered anisotropic saturated soft soil foundation is computed and analyzed, and the time-dependent mechanism of the soil deformation subjected to external loads is also revealed. (3) With the aid of coupled method of FEM and BEM and the finite element method, the piled raft foundation embedded in the saturated soft soil is investigated. The influences of the foundation stiffness, pile spacing and layering and anisotropic parameters on the time-dependent behavior of piled raft foundation are taken into consideration as well. (4) Combined with the project measured data and centrifuge modeling experiment results, the theoretical model is verified, and the further study on the time-dependent mechanism between the saturated soft soils and piled raft foundation is carried out.

天然饱和软土广泛分布于我国沿海和其它内陆水系附近区域，并具有层状及各向异性等复杂工程特性。本项目拟通过理论研究、数值分析及离心模型试验等手段，开展层状各向异性饱和软土的固结流变耦合效应及其与桩筏基础共同作用的时效研究，主要工作有：(1)基于Biot固结理论、经典粘弹/塑性地基模型及室内试验，建立三维各向异性饱和软土固结流变计算模型；(2)采用扩展的精细积分法和有限元法对粘弹/塑性层状各向异性饱和软土地基进行求解和分析，揭示层状饱和软土地基受力变形的时变机理；(3)采用有限元-边界元耦合法及有限元法求解分析饱和软土中的桩筏基础，探讨基础刚度、桩距及地基分层和各向异性等参数对桩筏基础时变行为的影响；(4)结合工程实测资料和离心模型试验结果，校验理论分析模型，并深入研究饱和软土与桩筏基础共同作用的时变机理。

桩筏基础作为一种常见的高层建筑深基础形式，广泛被应用于天然软土地区，以减小差异沉降，并提高地基承载力。本项目通过理论研究、数值分析及离心机模型试验等手段，开展了层状各向异性饱和软土的固结流变效应及其与桩筏基础共同作用的时效研究，主要的研究内容及成果包括：(1) 基于Biot固结理论、经典粘弹/塑性地基模型及室内试验，建立了一套三维各向异性饱和软土固结流变计算模型；(2) 采用扩展的精细积分法和编写的有限元UMAT子程序，对粘弹/塑性层状各向异性饱和软土地基模型进行求解和分析，揭示层状饱和软土地基受力变形的时变机理；(3) 采用有限元-边界元耦合法及有限元法求解分析饱和软土中的桩筏基础，探讨了基础刚度、桩距及地基分层和各向异性等参数对桩筏基础时变行为的影响；(4) 结合工程实测资料和离心模型试验结果，校验理论分析模型，建立一套分析饱和软土与桩筏基础共同作用的时效分析理论，为软土地区桩筏基础长期性能的评估与预测提供科学依据。