地铁隧道水平冻结施工的水热力耦合机理及其环境影响控制技术

With the construction of metro entering a high-speed development period in urban China, there are many metro lines located in soft stratum surrounded by the complex environment of constructions and buildings. The special geological environment and surrounding buildings lead to the construction security of many metro tunnels such as connecting passage, turn-round track, transition line, pump house and so on facing serious threat. The subject of study is horizontal artificial freezing technology for metro tunnel. In order to establish a more reasonable three-dimensional numerical model for coupled of moisture, heat and stress fields in artificial freezing stratum and an integration analysis model about frost heave and thaw settlement, the study will carry out the following research: the coupling mechanism of moisture, heat, and stress fields and frost heave and thaw settlement in artificial freezing stratum, the interaction between frost heave and thaw settlement and surrounding constructions environment, typical frost heave and thaw settlement control technology and key parameters of artificial freezing design, and so on. Thus the three fields coupling distribution characteristics of ground with horizontal artificial freezing and its dynamic development law will be revealed as well as the characteristics of interaction between frost heave and thaw settlement and surrounding constructions. At last, the typical frost heave and thaw settlement control technology will be formed, and the key parameters of artificial freezing design will be optimized, so as to promote the artificial freezing technology to develop in the direction of high efficiency, environment protection, safety and reliability.

我国城市地铁建设已步入高速发展时期，有大量城市地铁位于软质地层当中，其周边建构筑物环境复杂。软土地质和城市建构筑物环境，导致大量联络横通道、折返线、渡线以及泵房等地铁隧道的施工安全面临着巨大威胁。本项研究以城市地铁水平人工冻结技术为研究对象，开展水平人工冻结地层水热力耦合机理、冻胀融沉机理、冻胀融沉与建构筑物环境的相互作用、典型冻胀融沉防治技术以及人工冻结关键设计参数等的研究，以期构建更加合理的人工冻结水热力三场耦合三维数值模型和冻胀融沉统一分析模型、从而揭示水平人工冻结三场耦合分布特性及其动态发展规律、冻胀融沉对建构筑物环境的影响特性，最终形成典型的冻胀融沉防治技术，优化人工冻结的关键设计参数，从而推动城市人工冻结技术向高效环保、安全可靠的方向发展。

近年来人工冻结法施工在国内外地铁隧道工程建设中的应用日益广泛。人工冻土帷幕冻融全过程动态扩展特性的研究不仅关系到冻结施工效果的准确评估，而且还能为预防控制施工过程中伴随的冻胀融沉等不良工程现象提供重要的分析依据。本报告采用理论分析、室内试验、数值模拟以及现场监测相结合的研究方法，围绕软土地层地铁隧道人工冻结施工冻土帷幕动态扩展的研究主题，对人工冻结施工全程的温度场和位移场时空变化规律以及冻土帷幕三维动态扩展特征进行了深入的研究，提出了适用于人工冻结帷幕动态力学性质评估的新型智能传感监测方法。论文的主要研究内容及成果归纳如下：（1）基于采用压电陶瓷传感器，系统开展了室内试验研究，论证了应力波传播主动传感技术与力电阻抗测试技术实时监测软土冻融状态的可行性和合理性。（2）基于压电弹性力学理论，建立了压电片−冻土的力电阻抗耦合分析模型，推导出了考虑压电片−冻土耦合系统实际电学和力学边界条件的阻抗解析表达式，并开展了相关试验研究，验证了所提出模型的可靠性。（3）基于考虑土体冻融冰水相变潜热、弹塑性变形以及热力耦合作用，模拟了冻土帷幕的动态扩展过程，重点分析了积极冻结期−维护冻结期−自然解冻期各阶段瞬态温度场和位移场变化规律。（4）基于冻土温度场计算理论，建立了冻结管温度场计算的二维数值模型，重点对不同间距和布置方式下冻结管周围土体冻结过程的温度场变化过程进行了数值模拟。（5）系统研究了埋深、间歇冻结模式、注浆效果、台阶法开挖等对砂卵石地层人工冻结施工地表融沉的影响。