Prediction and verification of virgin rock temperature in deep-buried tunnels in complex mountainous areas

Active faults are prominent in the Gaoligong Mountain deep-buried tunnel, presenting significant geological challenges such as high geothermal heat, high-pressure and high-temperature water, and high ground stress. Accurate prediction of the virgin rock temperature is crucial for ventilation and cooling design during tunnel construction and operation. To better solve the problem of predicting the temperature field and virgin rock temperature of deep-buried tunnels in complex mountainous areas, this paper integrates key technical data from such regions, including complex undulating terrain, geological structures, high-temperature water, surface temperature variations, borehole temperature measurements, and rock thermal properties. This study examines the coupled heat transfer mechanism between groundwater and underground rocks in mountainous areas. It also investigates the analysis principles and calculation methods for predicting the temperature field and virgin rock temperature of deep-buried tunnels under nonlinear hydrothermal coupling, scale effects, and complex boundary and initial conditions. Building on this, a digital-twin geothermal analysis and inversion system for complex mountainous areas were developed and validated against measurements from the Gaoligong Mountain tunnel. The system demonstrated excellent agreement, with absolute errors of −0.91 to +0.71 °C and relative errors of −2.4% to +1.88%. This validates the predictive theory, calculation methods, and formulation of boundary and initial conditions for deep-buried geothermal fields and virgin rock temperatures in mountainous areas. The research provides accurate predictions of the temperature field and virgin rock temperature in deep-buried tunnels within complex mountainous regions, offering crucial technical support for railway route selection and for designing effective ventilation and heat-damage prevention strategies during tunnel construction and operation.