软黏土地层中地铁施工与运营引起的渐进环境效应评价与控制

The construction and operation of the subway in soft clay give rise to a series of environmental effects. It is of great significance to investigate the environmental effect and provide effective countermeasures. The project will carry out the rheological tests and consolidation tests of the soft clay under complex stress path. On the basis of the test results, the rheological characteristics and the damage evolution of the soft clay with complex stress paths under static or dynamic loads are revealed; and a rheological elastic-viscoplastic damage model is established. Coupling this model and the consolidation equation, a nonlinear settlement model considering the rheological damage and consolidation of the soft clay is deduced. By a series of the model tests and numerical calculations, the short-term deformation caused by the disturbance of the subway construction and the long-term deformation caused by train load are calculated, the prediction method for the progressive deformation of the subway in soft clay is proposed. Based on the shear tests of the interface between the structure and soft clay, the mechanism of nonlinear interaction in the interface of soil-structure is revealed. The progressive passive response of the structures under the nonlinear interface effect is discussed and the useful evaluation method is proposed. The control effects of various preventing measures and technical parameters on progressive deformation disaster are investigated. The preventing and controlling techniques and design criteria of progressive deformation of the subway are established during the process of construction and operation of subway in soft clay. The achievements in this project can greatly improve the construction of subways in soft soil region of China.

软黏土地层中地铁在施工与运营期会引起一系列的环境问题，研究其对环境的影响规律并采取有效的防控措施具有重要意义。本项目拟开展复杂应力路径下的流变与固结试验，揭示静动载复杂应力路径下软黏土流变机制，引入结构性损伤变量，建立复杂应力路径下软黏土弹黏塑性流变损伤本构模型。将该模型与固结方程耦合推导非线性损伤流变固结沉降模型，并结合室内模型试验与数值模拟，计算软黏土地铁施工短期扰动变形与列车荷载下长期附加变形，提出软黏土地层地铁短长期渐进变形预测方法。通过开展软黏土-结构面剪切试验，揭示软黏土-结构非线性相互作用机理与时间效应。结合数值模拟研究软黏土-结构面非线性作用下地铁开挖引起的既有构筑物渐进被动响应并建立实用评价方法。考察不同防控体系和防控技术参数对渐进变形灾害的控制效果，建立软黏土地层地铁施工与运营引起的渐进变形灾变防控技术及其设计准则。研究成果对提高我国软土地区地铁建设水平具有重要意义。

在软黏土地层中进行地铁隧道与深基坑的建设，是当今城市轨道交通发展中所面临的关键性技术难题之一。软黏土地层中地铁施工与运营所引起的短长期环境效应影响不可忽略，因此研究其环境效应发展规律，提出准确的环境效应评价方法与准则具有重要意义。基于此，采用两阶段法分析了软土流变特性对隧道施工期与运营期的环境效应影响，引入了可应用于隧道长期流变沉降预测的折减因子，基于CVISC模型提出一种新的变形弹黏塑性理论解，并验证了理论解的准确性。研究结果表明：在隧道运营期，桩基沉降增大，轴力增长明显，需要对周围桩基的承载力进行校核以保证工程安全。基于Hoek-Brown屈服准则得出了不同工况理想弹塑性岩土体的纵向变形曲线，得到了修正的纵向变形曲线拟合公式，并探讨了不同条件下的位移释放率及其影响因素。研究结果表明：原拟合公式对变形的预测缺乏准确性，会高估位移释放率，低估施加于支护上的荷载，相应支护设计偏于不安全。结合圆孔扩张理论和弹性-黏弹性对应性原理，推导了考虑体积变形的变形黏弹塑性解，提出了考虑流变特性的虚拟支护力和支护抗力计算方法，与收敛约束法结合，得到了考虑掌子面空间效应和支护作用影响的变形解析解。项目研究所提出的基本方法可运用于评价软黏土地层中地铁开挖引起的短长期环境效应，为软黏土地层中地铁建设所引起各项变形的控制提供设计指导。