Theoretical and experimental investigation on the thermal penetration depth in the surrounding rock of a deeply buried high-temperature tunnel

Abstract

Deeply buried tunnels that traverse geothermal areas tend to experience elevated temperatures. It is crucial to accurately predict the thermal penetration layer within the rock to address thermal damage in high-temperature tunnels. However, accurately predicting the thermal penetration layer is complicated due to its dependence on ventilation parameters and the thermal properties of the surrounding rock. In this study, the analytical solution of the temperature field of the surrounding rock was derived via the Laplace transformation and then nondimensionalized. Based on this, the correlation equation of the dimensionless radius of the thermal penetration layer (RTPL) was developed for two ranges of Biot numbers: 1 ≤ Bi ≤ 10 and 10 < Bi ≤ 1000. The dimensionless RTPL was found to be a segmented function of Bi and Fo, with Bi = 10 serving as the boundary point. To validate the correlation equation of the dimensionless RTPL, a scaled model experiment was designed and conducted. The obtained results exhibit a remarkable level of agreement. Additionally, the correlation equation is applied to three practical engineering cases. This research provides a valuable theoretical foundation for effectively managing thermal damage in high-temperature tunnels.