人工冻结环境冻胀卸荷作用多场耦合力学响应与失效预控研究

It is believed that frozen envelope technique can not only make special aquifer to be frozen soil curtains with excellent waterproof and non-contamination but also complement and perfect to the traditional excavation technology. However, the frost-heaving force and deformation have great influences on retaining structures and surrounding environment, and theoretical research was seriously lagging behind the need of engineering practice. Currently lack such system design methods and codes of frozen retaining structure. Frost-heaving and unloading properties and failure-precontrol mechanism are the theoretical basis of design and construction safely in frozen-retain engineering..Based on the theory of frozen soil constitutive and multi-field coupling model and the characteristics of stress-strain in artificial frozen soil, the constitutive model of frozen soil and interface between frozen soil and retaining structures were modified in this project, and primarily, three-dimensional nonlinear finite element analysis(FEA) model and the calculation parameters to simulate the behavior were also developed. All the constitutive models and multi-field FEA model were verified through kinds of experiments..By the means of multi-field coupling FEA model analysis and test validation of.frozen retaining structure during frost heaving and unloading, the temperature-field characteristics of frozen-soil curtain and the interaction mechanism of retaining structures and frozen soil, the influence laws of failure modes by the effect of frost heaving and releasing, the features of load versus deformation curve of components and multi-field coupling effect were understood in this study through the whole process of step-by-step excavation. Based on the mechanisms and parametric analysis, local damage and failure evolution, distribution of stress and strain, force transfer mechanisms in structural components etc. are clarified, and the limit state evaluations, failure precontrol and optimization calculation method of frozen support structure were proposed, which may provide theoretical foundation and scientific method of technological design and construction, disaster prevention and control of artificial freezing engineering. It also has important scientific and practical significance on theory development of frozen retaining engineering in China.

人工冻结围护是在特殊含水土层形成严格防水和无污染冻土帷幕，是传统技术的补充和完善，但冻胀变形对围护结构及周边环境影响甚大，目前缺乏这类冻结围护系统设计方法，理论研究还滞后工程实践需要，冻胀卸荷力学机理与失效预控是冻结围护设计、施工安全的理论基础。本研究拟根据冻土本构和多场耦合模型理论，分析人工冻土应力应变特性，明确冻土本构模型及其与围护结构界面接触，构建冻结围护结构非线性有限元模型和计算参数并实验研究检验。通过分步开挖全过程冻结围护结构多场耦合分析和试验测试验证，探明冻土冻胀卸荷性状及其与围护结构相互作用机理、围护结构全过程荷载变形特征、失效模式及其影响规律，揭示局部损伤和失效演化、应力应变分布和结构构件传力机制等受力机理，提出冻结围护结构失效极限状态评价和预控机制及优化计算方法，为冻结围护技术设计、施工和灾害防治提供理论基础和科学方法，对发展我国冻结围护工程理论具有重要的科学和现实意义。

冻结围护工程中，冻胀卸荷力学机理与失效预控是冻结围护设计、施工安全的理论基础。探明冻土冻胀卸荷性状及其与围护结构相互作用机理、围护结构全过程荷载变形特征、失效模式及其影响规律，才能为冻结围护技术设计、施工和灾害防治提供理论基础和科学方法。项目采用室内试验、理论分析、模型试验、数值计算、现场实测等多种分析手段相结合，开展了以下研究：.（1）系统进行滨海地层区域人工冻土试验了冻土物理力学性能、强度性能与材料本构试验，获得了不同因素对冻土物理力学性能影响敏感程度，建立区域人工冻土材料本构模型；.（2）构建区域人工冻土环境的冻结围护结构三维非线性有限元理论模型，获得冻结围护结构与人工冻土帷幕温度场宏观模型和界面接触模型，验证冻土帷幕多场耦合非线性三维模型的正确性；.（3）开展人工冻结围护冻胀卸荷全过程多场耦合力学响应与失效机理研究，获得冻土帷幕厚度、埋深荷载、冻胀变形等参数对冻结围护结构承载能力和失效模式的影响规律以及该类围护结构典型失效模式；冻胀卸荷作用人工冻结围护结构典型荷载-变形曲线特征，冻胀卸荷效应等因素对变形发展和应力应变分布等的影响规律等；.（4）研究冻胀卸荷作用冻结围护结构构件承载力影响公式、冻土帷幕整体稳定控制和结构构件剪力计算公式，获得冻胀卸荷作用人工冻结围护结构与冻土帷幕极限状态描述与评价；.（5）分析多场耦合条件下冻土帷幕及周围环境土层的应力分布和变形特性、冻土帷幕优化计算方法和破坏控制理论和结构构件荷载-变形关系曲线，获得冻胀卸荷作用冻结围护结构与冻土帷幕发展特征、优化计算方法和控制理论。.本项目研究对进一步认识区域人工冻土物理力学性能及其本构模型、建立冻结围护三维非线性模型、优化设计冻土帷幕厚度、研究冻胀卸荷全过程多场耦合力学响应与失效机理、发展冻土帷幕优化计算方法和破坏控制理论等都具有重要的理论和现实意义，研究成果对地铁过程建设冻结加固提供借鉴和参考。