Correction of heat storage temperature Mg²⁺ and analysis of heat damage mechanism of hydrothermal system in central and eastern Tibetan Plateau

Tunnel is an important engineering form of railway crossing the middle and eastern part of the Qinghai-Tibet Plateau.It is necessary to discuss the influencing factors of tunnel thermal disaster.The methods of tunnel heat damage prediction are comprehensive, among which the hydrogeochemical method is widely used because of its easy implementation and high cost performance.Heat storage temperature is an important parameter in the study of hydrothermal system.Due to the complexity of the heat storage system, it is difficult to fully consider the geochemical process in the calculation of heat storage temperature, and deviation may take place in heat storage temperature calculation.The Mg²⁺ correction of heat storage temperature is affected by the rock type, migration rate and structural conditions of heat storage under the action of hot water.Therefore, the Mg²⁺ correction can be used to assist the analysis of multi-type hydrothermal cycling mechanism.Based on this, the characteristics of heat damage encountered by the tunnel through the hydrothermal system can be identified.The Na-K-Ca triangle diagram of equilibrium judgment of Mg-rich system was constructed by using the equilibrium theory of temperature scale.Based on the geological background of hydrothermal system action, the equilibrium sample points were combed to discuss the relationship between the correction characteristics of Mg²⁺ and the influencing factors in the typical hydrothermal system in western Sichuan and eastern Tibet.The various types of hydrothermal cycling conditions, water-rock interaction, heat and mass transfer mechanism in central and eastern Qinghai-Tibet Plateau were analyzed and compared, which can assist in the analysis of hazards such as high rock temperature, hot water inrush and surrounding rock cracking caused by geothermal in engineering.This method is a methodological discussion about hydrogeochemical prediction of engineering heat damage, and can also provide a theoretical basis for heat damage prevention and control in the middle and eastern part of the Qinghai-Tibet Plateau and in the future.