Research on the Crystallization Distribution and Evolution Law of the Waterproofing and Drainage System in High Geothermal Tunnels

To explore the influence pattern of high temperature on the crystallization amount of the waterproofing and drainage system, and to analyze the distribution characteristics of crystallization on the waterproofing and drainage board, a large-scale model test device for the crystallization of the high-temperature tunnel waterproofing system was designed and developed by replacing the circumferential drainage pipe with the waterproofing and drainage board. The gradient condition simulation of hot water temperature was realized. The test results show: (1) The crystallization adheres to the surface of the waterproofing and drainage board in two ways: strip-like and planar. The blocking degree at the lower part is more severe than that at the upper part. (2) With the increase of the circulating water temperature, the crystallization amount of the waterproofing and drainage system significantly increases. (3) In response to the high-temperature conditions and the severe blocking at the lower part of the waterproofing and drainage board, engineering suggestions are proposed to prioritize strengthening waterproofing and moderately reducing the number of convex shells at the lower part of the waterproofing and drainage board. The applicability of conventional crystallization disposal measures under high temperature is also discussed. In actual engineering, high-temperature-resistant equipment materials need to be selected, and the optimal solution should be adopted according to the time, local conditions, and segmented needs.