人工地层冻结法风险预控

Risk prevention and control of artificial ground freezing(AGF)

人工地层冻结法作为一种特殊工法,已有近160 a工程应用历史,仍是当前解决地下工程建设所面临"水、软、变形难以预测"3大难题的一种灵活、可靠、绿色技术方案。采用人工制冷方法将地层中的水冻结成冰是地层冻结法核心,但也正是由于维系冻土强度的冰的存在及其特殊性质,人工冻土与冻土结构更具有易变性和敏感性,也使得人工地层冻结法工程应用存在一定风险。基于冻土中水的相变过程及其动态平衡、冻结土体水分迁移、冻土内部联结作用的基本原理,分析了冻土特点及人工地层冻结法工程风险的物理本质,进而结合人工地层冻结法施工流程,从严格设计输入数据可靠关、严把冻结系统各关键环节质量关、严守冻结和开挖全过程安全运行维护关3方面提出了人工地层冻结法工程风险的预控方法与技术,为其在今后地下工程建设中的推广应用提供指引。

The artificial ground freezing method(AGF),a special construction method,has a history of almost 160 years.It is still a flexible,and reliable environment-protection geotechnical-support method to solve the three difficulties of groundwater,soft soils,and unpredictable deformation encountered in underground engineering.It is the core of AGF to freeze the water in stratum into ice by artificial refrigeration.However,it is the existence of ice that maintains the strength of frozen soils and leads to frozen soils being much more changeable and sensitive,which makes the AGF have some risks in engineering.In this study,the characteristics of artificial frozen soils and the corresponding risk of AGF engineering are elucidated based on the basic principles of the phase change process and dynamic balance of water in frozen soils,water migration during soil freezing,and the internal connection of frozen soils.Then,based on the AGF construction process,the risk prevention and control method of AGF are put forward from three aspects:strictly controlling the reliability of design input data,strictly controlling the quality of freezing system,strictly controlling the safe operation and maintenance during the whole processes of freezing and excavation,which will provide a new guidance for the application of the AGF in underground engineering construction in the future.