Geothermal anomalies in the Xianshuihe area: Implications for tunnel construction along the Sichuan-Tibet Railway, China

This study presents a comprehensively analysis of geothermal characteristics in the Xianshuihe geothermal area along the Sichuan-Tibet Railway, using temperature logging, temperature monitoring and thermal conductivity measurement, and regional geothermal geological survey data. The research focuses on the geothermal background, geothermal field, and their potential impact on the surrounding tunnels. The investigation reveals that the average heat flow value in the study area is approximately 73.0 mW/m², significantly higher than the average terrestrial heat flow in mainland China (​​62.5 mW/m²). This high terrestrial heat flow signifies a distinct thermal background in the area. In addition, geothermal anomalies in the area are found to be closely associated with the distribution of hot springs along NW faults, indicating a strong control by the Xianshuihe fault zone. The study concludes that the region's favorable conditions for geothermal resources are attributed to the combination of high terrestrial heatflow background and water-conducting faults. However, these conditions also pose a potential threat of heat damage to the tunnels along the Sichuan-Tibet Railway. To evaluate the risk, the research takes into account the terrestrial heat flow, thermal conductivity of the tunnel surrounding rocks, characteristics of the regional constant temperature layer, as well as the distribution of hot springs and faults. The analysis specifically focuses on the thermal damage risk of Kangding 1^# tunnel and 2^# tunnel passing through the study area. Based on the findings, it is determined that Kangding 1^# tunnel and 2^# tunnel have relatively low risk of heat damage, as they have avoided most of the high temperature anomaly areas. However, several sections of the tunnels do traverse zones with low to medium temperatures, where surface rock temperatures can reach up to 45°C. Therefore, these regions should not be neglected during the construction and operation of the tunnel project, and mitigation measures may be necessary to address the potential heat-related challenges in the area.