泛北极多年冻土及重大线性工程稳定性状况

泛北极是中国“一带一路”倡议的主要合作示范区域,已有的重大线性工程及新的基础设施建设均面临着与多年冻土相关的冻融灾害及工程病害问题。在全球气候变暖及人类活动增强的背景下,泛北极多年冻土主要呈现地温升高、活动层厚度增加趋势,且低温多年冻土地温升高更加明显,20世纪70年代以来年平均地温(MAGT)升温最高可达3 ℃; 自北向南多年冻土活动层厚度增加,且增厚趋势趋于明显,在俄蒙边境地区活动层厚度增速为3～5 cm·年^-1。多年冻土退化诱发系列与热喀斯特过程相关的地质灾害,主要包括热喀斯特滑坡与热喀斯特湖,且灾害数量急剧增加,如加拿大Banks Island地区1984～2015年热喀斯特滑坡数量增加了约60倍。在多年冻土退化、热稳定性降低的背景下,泛北极铁路、公路和管道等重大线性工程出现了沉陷、裂缝等不同类型、不同程度的病害,整体上多年冻土区道路工程病害率大于30%。热融灾害及工程病害的发育均与气候及岩土、冻土条件相关,但工程病害还与工程运营期限、工程结构形式密切关联。对比泛北极道路、管道等线性工程状况及其与工程结构的关系,以及病害特征和防治措施效果,表明基于保护冻土的“主动冷却”设计原则依然是多年冻土区工程设计的主导思想。

Permafrost and Stability of the Major Linear Engineering in the Pan-Arctic Region

The pan-Arctic region is one of the cooperative demonstration areas of the “Belt and Road” initiative. The local linear engineering faces serious challenges of permafrost-thawing hazards and corresponding engineering problems. Under the background of the climate warming and human activity increasing, permafrost in the pan-Arctic region has been undergoing continuous degradation, showing as increasing of the mean annual ground temperature(MAGT), thickening of the active layer and general decreasing of the thermal stability. The low-temperature permafrost has been developing more obvious increase in ground temperature, since the 1970s, the MAGT has increased up to 3 ℃, and the active layer thickness of the permafrost has increased from north to south, and the trend of thickening is obvious. The series of geological hazards induced by the permafrost degradation is related to thermokarst processes, mainly including thermokarst landslides and thermokarst lakes. The number of the landslide hazard increases seriously, shown by a 60-fold increase in numbers between 1984 and 2015, as more than 4 000 thermokarst landslides are initiated in Banks Island, Canada. Under the background of permafrost degradation and decrease of thermal stability, the major linear engineering projects, such as railways, highways and pipelines in the pan-Arctic region, appear various types and degrees of problems such as settlement and cracks. With the decrease of the thermal stability of permafrost and the increase of susceptibility of the thawing-induced hazards, the engineering problems would continue to develop. Compared with the thawing-induced hazards, the development of engineering problems is not only related to the climate, geotechnical and frozen soil conditions, but also closely related to the engineering operation period and engineering structures. On the whole, the disease rate of road engineering in the permafrost regions is more than 30%. After assessing the current status, along with the configure structures of the main linear engineering projects, including roadway, pipeline, etc., in the pan-Arctic region, it is confirmed that the “active cooling” design principle based on the protection of frozen soil is still the dominant method of engineering design in the permafrost regions.