Mechanical properties and damage constitutive model of silty mudstone under heating and water-cooling cycles

Understanding the deformation and damage behaviors of soft rocks under temperatures and water–rock interactions is crucial for designing rock engineering structures and for assessing geotechnical disasters. Hence, the physical–mechanical characteristics and damage mechanisms of silty mudstone under heating and water-cooling cycles were determined by a series of laboratory tests. The results indicate that heating and water-cooling treatments prompt crack development within silty mudstone, observable through volume augmentation along with reductions in mass, density, and P-wave velocity. The interconnections between the decrease of mechanical properties such as elastic modulus, cohesion, and internal friction angle of silty mudstone and the factors including temperatures and cycle number are explicitly established. The deterioration of the physical–mechanical properties of silty mudstone primarily arises from the thermal expansion, dehydration, and hydrolysis of mineral constituents. Furthermore, a new damage constitutive model for silty mudstone considering temperature and the number of heating and water-cooling cycles is established based on lognormal distribution and the Mohr–Coulomb criterion. Additionally, the model parameters S₀ and F₀ characterize the homogeneity and average strength, enabling a quantitative assessment of the damage degree of rocks.