Hydro-thermo-mechanical transient response for a cylindrical unlined tunnel in poroelastic medium based on multi-dual-phase-lag heat conduction model

The dynamic coupled hydro-thermo-mechanical behavior of the unlined structure in the saturated porous structure under extreme geotechnical and geology engineering (e.g., underground explosion, laser thermal rock breaking) has aroused extensive research interests in the constitutive modeling and transient dynamic responses prediction. Despite the current hydro-thermo-mechanical models that have been historically proposed, the model construction is still based on the classical thermoelastic coupling theory (Fourier heat conduction model). In the study of coupled heat transfer in extreme environments, the heat flux at a certain point is not only affected by the instantaneous heat source but also depends on the temperature gradient at that point and the effect of its historical heat flow. To address this deficiency, this work aims to construct a new hydro-thermo-mechanical coupling model by introducing the multi-dual-phase lag heat conduction law. The proposed model is applied to investigate the transient structural dynamic hydro-thermo-mechanical response of a cylindrical unlined tunnel in the poroelastic medium by applying the Laplace transformation approach. The influences of the parameters of heat flux lag and temperature lag on the wave propagation as well as the dimensionless responses of temperature, displacement, stress, and pore water pressure were evaluated and discussed.