Chain-generation mechanisms and risk control of thermal disasters in high geotemperature tunnels Ⅰ——Thermal disaster effect and geological features

Addressing the limitations of current research on tunnel thermal disasters, which primarily focuses on managing high rock temperatures and ambient temperatures during construction while neglecting heat source mechanisms and accompanying disasters such as high-temperature water inrush and harmful gases, this study systematically deconstructs the formation mechanisms and disaster effects of tunnel thermal disasters by constructing a novel cognitive system termed “heat source-gas source-response-disaster.” Firstly, based on thermal phenomena observed in geothermal anomaly zones and extensive engineering practices related to thermal disasters, tunnel thermal disasters are redefined to collectively encompass high rock temperature, high-temperature water, and harmful gas inrush. Secondly, through a statistical analysis of 87 global cases of tunnel thermal disasters, thermally-induced disasters in geothermal anomaly zones are classified into five types: high rock temperature, hazardous gas, high rock temperature combined with high-temperature water inrush, high rock temperature combined with hazardous gas, and high rock temperature combined with both hazardous gas and high-temperature water inrush. This classification reveals a strong correlation with surface thermal anomalies and the formation lithology. Thirdly, the effects of tunnel thermal disasters are systematically categorized, illustrating their detrimental impacts on the tunnel’s temperature and humidity environment, exacerbation of surrounding rock deformation and failure, induction of cascading failures in support structures, and triggering of multi-dimensional gaseous disaster cascades. Building upon this, the Qinghai—Tibet Plateau is examined as a case study to investigate the origins, sources, and conduction mechanisms of heat and gas in typical geothermal anomaly zones. This establishes a theoretical paradigm for the synergistic genesis of thermal disasters, involving crustal, mantle, or crust-mantle heat and gas generation, coupled with tectonic heat and gas conduction. Finally, the reliability of the research findings is validated through an analysis of a typical tunnel thermal disaster case. This study provides a theoretical foundation for further exploration of disaster-prone patterns, identification of hazard structures, and formulation of prevention and control measures for tunnel thermal disasters.