深基坑降水中组合土层逆回弹与渐进释水压缩耦合沉降机理研究

In the process of deep underground space development, high construction risk and engineering ground settlement are the direct problems brought by deep foundation pit dewatering. However, the calculation theory of groundwater seepage and ground settlement has been far behind the needs of engineering practice..This project focuses on the respective law of deformation development and the spatio-temporal coupling mechanism under reverse rebound and gradual compression during deep foundation pit dewatering in layered soils. Physical model tests of transparent soil will be carried out for the analysis of water head loss in the process of groundwater seepage, then an improved 3D calculation model of groundwater seepage can be established. The seepage field and stress field evolution process of layered soils driven by the change of groundwater seepage field will be analyzed, then a fully coupled calculation model of them can be established. A quantitatively described set of indexes for reverse rebound will be established, then a calculation method for the settlement attenuation will be presented. Finally, based on the three models above, a 3D calculation model for settlement analysis in layered soils will be established to reveal the coupling mechanism under reverse rebound and gradual compression, a simplified coupling analysis method will be proposed..This coupling settlement mechanism is of great significance for engineering ground settlement predicting and implementing environmental protection during foundation pit dewatering. And the simplified coupling analysis method will provide important support for the design of deep foundation pit dewatering.

沿海软土城市深层地下空间开发中，直接面临的问题就是深基坑降水带来的高施工风险及工程性地面沉降，然而地下水渗流和地面沉降相关理论方法已经远远落后于工程实践需要。.本项目围绕深基坑降水组合土层逆回弹协调变形与渐进释水压缩两类沉降模式各自变形发展规律及其时空耦合机理展开研究。开展组合土层透明土地下水渗流物理模型试验，分析地下水越流渗透水头损失规律，改进地下水三维渗流计算模型；分析地下水渗流场变化驱动下组合土层渗流场与应力场演化过程，建立二者完全耦合计算模型；构建可定量化描述的逆回弹协调变形控制性指标集，提出沉降衰减量计算方法。基于前三者构建组合土层耦合沉降分析三维计算模型，揭示逆回弹与渐进释水压缩时空耦合机理，提出耦合简化理论分析方法。.拟开展研究提出的基坑降水耦合沉降机理，对预测工程性地面沉降、实施有效环境保护措施具有重大意义，提出的耦合简化理论分析方法将为深基坑工程降水设计提供重要科学支撑。

沿海软土城市深层地下空间开发中，直接面临的问题就是深基坑降水带来的高施工风险及工程性地面沉降，然而地下水渗流和地面沉降相关理论方法已经远远落后于工程实践需要。本项目针对深基坑工程降水过程中组合土层沉降的时空效应问题，采用室内试验、模型试验、理论分析、数值模拟等方法，揭示了深源减压上覆土层逆回弹分异沉降和弱透水层渐进水力边界释水压缩的耦合沉降机理与时空发展规律。通过将透明土渗流试验方法引入基坑降水分析领域，基于局部非达西扰流叠加放大效应提出了最优帷幕-井群空间关系和基坑承压水灾害控制方法，建立了弹性、粘弹性组合土层渗透、应力与变形的关系方程，通过渗透变形模量修正实现了组合土层水位降深与沉降精准计算。研究成果对预测工程性地面沉降、实施有效环境保护措施具有重大意义，提出的耦合简化理论分析方法将为深基坑工程降水设计提供重要科学支撑，可广泛应用于沿海软土地区深基坑工程降水设计和地面沉降控制。.