Temperature-dependent evolution of permeability and pore structure of marble under a high-temperature thermo-hydro-mechanical coupling environment

Seepage represents a primary factor leading to rock instability, endangering the safety of subterranean structures. Given its prevalence in underground engineering, a comprehensive investigation of marble's permeability and pore structure is imperative. The coupled thermo-hydro-mechanical (THM) problem often encountered by marble in underground environment has not been studied. The permeability evolution of marble under a wide range of temperature (25-600 degrees C) and triaxial stress (hydrostatic pressure = 25 MPa) was studied by a high-temperature and high-pressure THM coupling universal testing machine. The changes of pore and fracture properties of marble under different conditions were evaluated by microcomputer tomography and mercury injection. The results show that the changes of pore and fracture properties of marble under THM coupling condition are different from those under high-temperature heat treatment condition. In the THM coupling environment, because of the low confining pressure (25 MPa), there is little difference between the microparameters of the marble rock under THM and HTO (high-temperature-only) conditions. Our findings provide a basis for theoretical approaches that assess the related risks to constructions subjected to high temperatures in the underground environments.