多层结构含水层系统土体变形机理和地面沉降预测

Land subsidence disasters have become one of important factors affecting the regional economic and the sustainable social development. In order to curb the deteriotion of land subsidence effectively and to achieve the scentific cure for land subsidence disasters, the land subsidence due to groundwater withdrawal during the enigneering construction processes will be studied in this project, the multiple approaches including theoretical analysis,physical experiments and numerical simulation are used to investigate the deformation mechanism of soil in multi-aquifer system caused by groundwater withdrawal and also to build a land subsidenc prediction method which considers the coupling of the flow and deformation. Aim at reveal the laws of soil deformation induced by groundwater changes, the stress path laboratory testes will be carried out to simulate the soil stress state in multi-aquifer system. Based on the physical model test of the multi-layer aquifer systems, the distribution mode of its soil deformation and the interaction law between soil and water in multi-layer aquifers are explored. A three-dimensional semi-analytical numerical analysis method for modeling the groundwater flow and coupled flow and deformation in multi-aquifer system is presented to investigate the law of groundwater flow and soil deformation in multi-aquifer system under the action of multi-field. A simplified subsidence analysis method which can reflect the law of soil deformation in multi-aquifer system will be developed, this can provide a theoretical guidance and technical support for scientific regulation and reasonable evaluation of the subsidence disaster caused by the groundwater withdrawal.

地面沉降灾害已成为影响区域经济社会可持续发展的重要因素之一，为有效遏制地面沉降的恶化趋势，实现地面沉降灾害的科学防治，本课题以工程建设中多层结构含水层系统地下水引起的地面沉降为研究对象，综合运用理论分析、物理实验、数值模拟相结合的方法，开展地下水引起含水层系统土体变形机理和流固耦合作用下地面沉降预测方法的研究。旨在通过对含水层系统土体应力状态的分析，开展真实反映含水层土体应力路径的室内试验，揭示地下水位变化诱发土体变形的规律；开展多层结构含水层系统物理模型试验，探究多层结构含水层系统中土体变形的分布规律和水土相互作用机理；提出含水层系统地下水流和流固耦合地面沉降计算模型的三维半解析数值分析法，系统揭示多场作用下含水层系统的地下水流动规律和土体变形规律；建立符合多层结构含水层系统土体变形规律的地面沉降简化计算方法，为地下水引起的地面沉降灾害的科学调控与合理评价提供理论指导和技术支持。

针对多层结构含水层系统中水土相互作用引起的地面沉降地质灾害，系统研究了含水层系统土体的变形特性和地面沉降计算方法。主要研究工作和成果：.1.开展了符合抽注水作用下土体应力状态和应力路径的含水层砂土变形特性试验，探讨了不同级配含水层砂土变形的非线性和时效性特征；发现了注水强度小于或等于抽水强度时，含水层砂土呈现的压缩变形现象；提出了抽水作用下考虑抽水速率和抽水强度的砂土应力-应变-时间归一化经验公式。.2.开展了孔压梯度作用下土的压缩性和渗透性试验，探讨了孔压梯度作用下土体非线性变形和渗透特性，建立对数坐标下土的孔隙比e与渗透系数k的近似线性关系，采用参数α表述了土的非线性固结特性，为合理描述含水层系统中弱透水层土体的渗透特性和变形特性提供了依据。.3.提出了黏土掺碳的人工制斑的方法，实现了PIV技术对黏土位移场有效测量。研制并开展了多层结构含水层模型试验，探讨了抽注水作用下含水层系统的土体变形规律，得到了抽水作用下含水层系统土体以塑性变形为主、注水作用下土体回弹变形较小及土体变形增量随着抽、注水过程的增加而明显减小的变形规律，揭示多层结构含水层系统的土体变形规律和水土相互作用机理。.4.设计并开展了土体变形扩散传播模型试验，探讨了深部土体变形的扩散传播规律和上覆土体体积变化规律。建立了能够考虑上覆土体变形扩散和体积变化特征的土体变形扩散传播的地面沉降简化计算模型。提出了模型参数B和参数N与土体密度ρ的经验公式，为评价含水层抽水、隧道开挖等工程活动引起的地面沉降提供了一种新的方法。.5.提出考虑潜水流动的层状多层结构含水层系统地下水流半解析数值方法，完善地下水三维非稳定流问题的有限层方法。建立了考虑土体层状非均质、各向异性、孔隙流体可压缩性等因素的三维流固耦合地面沉降半解析数值模型，实现了地面沉降计算模型中土体变形和地下水水位的同步求解，为地下水流动和地面沉降的三维分析提供了一条新的途径。