The characteristics of expansive soil, such as overconsolidation, multi fissure and shrinkage cracking due to water expansion and water loss, are called hidden disasters by the geotechnical engineering community. Its damage mechanism has become an important technical problem that the underground space engineering must face and solve. The expansive soil is mainly distributed in the eastern region in Chengdu. According to the investigation, the soil collapse between the supporting piles often occurs in the construction of the deep foundation pit of the subway station in the eastern region, causing safety accidents such as personal injury or equipment damage. In this paper, taking the stability of soil between piles of deep foundation pit excavation and support piles of the East extension line station of phase II of Chengdu rail transit line 17 as the research object, the instability characteristics of soil between piles of deep foundation pit excavation and support piles of railway stations on expansive land in Chengdu area are systematically studied by means of field investigation, field measurement analysis, instability characteristics analysis and calculation and derivation of soil stability between piles, and the characteristics and causes of soil instability between piles of deep foundation pit excavation and support piles of railway stations on expansive land are proposed, and put forward prevention measures and suggestions.

With the expansion of engineering activities, numerous major projects are gradually emerging in frozen soil regions. However, due to the unique engineering properties of frozen soil, various frozen soil engineering di-sasters have occurred or accelerated under the conditions of global warming, posing a serious threat to the project operation, environmental and ecological protection, and humanity development. This paper summarizes the formation conditions of frozen soil engineering disasters from the perspectives of thermal, hydraulic, and mechanical factors based on existing research. The definition, development trend and characteristics of thawing disaster, frost heaving disaster and freeze-thaw disaster are generalized. The main prevention measures are summarized based on the thermal, hydraulic, and mechanical conditions that cause frozen soil engineering di-sasters. Research suggestions on frozen soil engineering disasters including the engineering disaster mechanism under the frozen soil degradation and multi-hazard risk assessment are proposed. It may provide some references for the harmonious coexistence and sustainable development of engineering construction and geological envi-ronment in frozen soil area.