Influence of Ground Temperature on Shotcrete-to-Rock Adhesion in Tunnels

Table 1

Disaster cases of tunnel construction worldwide in highly geothermal environments.

Tunnel name	Project overview	Thermal damage
China–Nepal railway tunnel	The railway planning route runs through two geothermal activity zones in the Yarluzangbu river and the Yarluzangbu river valley. The hot springs along the line are extremely frequent, with water temperatures up to 88°C. A total of 45 tunnels are planned across the line, with a total length of approximately 272 km	Deteriorating the construction work environment, reducing labor productivity and threatening the health and safety of workers. The additional temperature stress generated by the high ground temperature will cause initial tunnel support and secondary lining cracking, which will affect structural safety and durability [15, 16]
Anfang Tunnel in Japan	During the construction of the tunnel, the tunnel encounters severe hot water problems and high-temperature area problems. The maximum temperature of the hot water flowing out of the tunnel can reach 73°C, and the temperature of some rock mass exceeds 50°C. The volcanic gas exists in the tunnel, which seriously affects the tunnel working environment	Due to the terrestrial heat, the temperature of the rock mass is very high, and the concrete hydration heat is not easily released, resulting in excessive temperature difference between the exterior and the interior of the concrete, and there may be cracks, which seriously affect the adhesion between the concrete and the surrounding rock [15]
Tokaanu Tunnel in New Zealand	New Zealand’s Tokaanu hydropower station and Tokaanu Tunnel were built in a high-temperature site. Through years of borehole investigation, it was found that there was a large amount of high-temperature underground hot water (some temperatures exceeding 100°C), and the front of the tunnel face was affected by geothermal energy. The tunnel temperature measured in the pilot hole of the tunnel wall is too high	The high temperature seriously affects the safety of the tunnel structure. Excessive rock temperature will cause the concrete to deteriorate and crack; at the same time, the high-temperature heat flow will pose a threat to people’s lives and property [17, 18]