渐冻隧道的演化及灾变控制方法研究

Permafrost covers 22.4% of mainland area in China. For tunnels built in isolated permafrost zone and unfrozen soil that distributes in the district with annual average temperature below zero, the original unfrozen soil around the tunnels will develop into permafrost during operation period. Consequently, the tunnels turn into so-called “frost penetration tunnels” and severe disasters, such as waterproof and drainage system failure and lining frost cracks, will occur. Decades later, due to global warming, the newborn permafrost around the tunnels will melt, which leads to surrounding rock instability and other damages. Given this, key scientific problems are urgently to be solved for tunnel construction and operation in cold regions, including the formation mechanism, formation condition and evolution regularity of frost penetration tunnel, the disaster formation mechanism and disaster control methods of frost penetration tunnel, and global-warming-caused melting tunnel. This project will use theoretical analysis, numerical simulation, physical model experiment, field monitoring, and detection methods to analyze formation mechanism and formation condition of frost penetration tunnel in cold regions with annual average temperature below zero. On this basis, the frost penetration tunnels freezing evolution regularity, melting evolution regularity caused by global warming, and engineering measures influence on the evolution regularity will be revealed. Furthermore, disaster types and formation mechanism in frost penetration tunnels and the global warming-caused melting tunnel will be figured out. An entire life-cycle disaster control method for frost penetration tunnels will be presented. In summary, this project will greatly improve the theoretical and technical level of design, operation and maintenance of tunnels in cold regions, which has a broad application prospect.

我国多年冻土区面积约占国土面积的22.4%。负年平均气温区的局部多年冻土隧道和非多年冻土隧道在贯通运行后其非冻土段围岩会逐渐冻结产生新生多年冻土，引起隧道渐冻而形成渐冻隧道。隧道渐冻后将导致防排水系统失效、衬砌冻胀开裂等灾变，数十年后因全球变暖又会产生渐融而引发围岩失稳等灾变。因此，渐冻隧道的形成机理和形成条件及其演化规律、渐冻隧道和全球变暖渐融后隧道的灾变形成机理和控制方法是高寒地区隧道工程建设和运行中迫切需要解决的关键科学问题。本项目拟采用理论分析、数值模拟、物理模拟试验、现场监测与探测等方法，在弄清负年平均气温区渐冻隧道形成机理和形成条件的基础上，探明渐冻隧道的渐冻演化规律和全球变暖后的渐融演化规律，以及工程措施对其演化规律的影响，揭示渐冻隧道和全球变暖渐融后的灾变类型及形成机理，提出渐冻隧道全寿命灾变控制方法，以大幅度提高高寒地区隧道设计和运行维护的理论和技术水平，应用前景广阔。

我国多年冻土区面积约占国土面积的22.4%，年平均气温是负温的地区则更广，负年平均气温地区的隧道在贯通运行后其非冻土段围岩会逐渐冻结而产生新生多年冻土，引起隧道渐冻而形成渐冻隧道。本项目弄清了渐冻隧道的形成机理和形成条件，探明了渐冻隧道的渐冻演化规律和全球变暖后的渐融演化规律，揭示了渐冻隧道的灾变类型及形成机理，提出了渐冻隧道全寿命周期灾变控制方法。推导了考虑复杂气候影响的隧道对流—导热温度场相似模拟试验相似关系，研制了渐冻隧道演化模拟试验系统，得出了负年平均气温条件下渐冻隧道的形成条件及其径向和纵向的渐冻演化规律。基于全周期隧道温度场计算模型，分析了局部多年冻土隧道的纵横向渐冻及渐融演化规律，探明了负年平均地区隧道的灾变类型及其致灾机制，结果表明：负年平均气温地区的隧道在贯通运行后其冻结圈会在横断面上向围岩径深发展，并逐渐沿着隧道纵向推进，隧道非冻土段会逐年冻结并发展成工程多年冻土。但考虑气候变暖后，随着年平均气温的上升，新生工程多年冻土会退化为工程季节冻土，最大冻结深度也逐年减小，隧道表现出渐融的现象。提出了寒区隧道排水系统分段设计及各分段间的衔接技术，并根据隧道渐冻渐融的演化规律对寒区隧道防排水系统设计进行了优化。提出了寒区隧道新型维护型防排水系统，实现了衬砌段及接缝处防排水系统全寿命周期的可维护性能。研究了含裂隙岩体的非各向均匀冻胀性及冻胀变形，求得了考虑非轴向对称荷载和围岩非均匀冻胀性的寒区隧道冻胀力和衬砌承载力解析解。提出了主动通风的寒区隧道冻害灾变控制方法，分别针对隧道全断面、离壁式保温结构及排水系统提出了对应的正积温通风调控方法。研究成果将是渐冻隧道建设-维护全寿命设计的重要理论基础和技术依据，对建立负年平均气温的高寒地区隧道的设计和运行维护理论和设计方法具有重要的科学意义，在广大高寒地区隧道建设中有很好的应用前景，也是加强国防建设、推动基础设施建设的迫切需要。