Thermal‐Mechanical Solution of Saturated Soft Soil around a Semi‐Permeable Tunnel Considering Internal Heat Effects

Abstract

Urban tunnels operate for decades under complex service conditions where mechanical loading and thermal disturbance are invariably intertwined. In practice, long‐term train operation, ventilation and air‐conditioning systems, energy‐tunnel heat exchange, and even accidental fire scenarios continuously inject heat into tunnel linings and the surrounding saturated ground. These realities create a coupled thermo‐hydro‐mechanical environment around tunnels that is far more complex than what is captured by classical consolidation theories, and the long‐term implications for ground deformation and tunnel serviceability remain insufficiently understood. To address this gap, this study develops an analytical model for the thermo consolidation of soils surrounding tunnels by extending the Terzaghi–Rendulic consolidation framework to incorporate heat diffusion, temperature‐dependent permeability, and soil viscous effects. On the basis of the derived closed‐form solution, the study systematically explores the roles of tunnel boundary temperature, thermal conductivity, tunnel depth and radius, tunnel permeability, and soil viscosity on temperature fields, excess pore‐water pressure evolution, and settlement response. The results reveal that tunnel‐induced thermal effects predominantly reshape pore‐pressure dissipation pathways and consolidation timescales by altering the spatiotemporal distribution of permeability. Geometric parameters act in a unified manner on both heat transfer and consolidation by modifying the effective overburden thickness. Tunnel permeability emerges as a key control on the consolidation rate, whereas the soil viscosity coefficient dictates whether settlements exhibit persistent, rheology‐driven long‐term development. By providing a tractable yet physically enriched analytical framework, this work offers a theoretical basis for evaluating the long‐term performance of tunnels subjected to combined operational thermal loads and sudden surcharges.