Mechanical properties and damage modeling of unloaded marble under freezing and thawing with different temperature ranges

Abstract

The seasonal freeze-thaw environment is a primary factor contributing to the deterioration of manually excavated disturbed rock masses on reservoir bank slopes in highland alpine areas. To investigate the mechanical properties and damage deterioration mechanism of excavation-unloading rock under seasonal freeze-thaw environment in cold region, the freeze-thaw cycle tests with different temperature difference levels (−10–10 °C, −15–25 °C, −20–40 °C) and different cycle times (0,10,20,30) were simulated for the triaxial unloading damaged marble. Then, the mechanical parameters of unloaded marble after freezing and thawing were obtained by uniaxial compression and triaxial compression tests, and the influence laws of temperature ranges, number of freezing and thawing cycles and confining pressure on the mechanical properties of unloaded marble were analyzed. Finally, the damage model of unloaded marble considering freeze-thaw action was established. The results show that the strength of unloaded marble is significantly weakened under the combined effect of F-T (freezing and thawing) and loading, and that the deterioration effect of the number of F-T cycles is stronger than that of the temperature ranges. The increase in the confining pressure increased the compressive strength and elastic modulus of the unloaded marble, and suppressed the damage of the unloaded marble after the freeze-thaw treatment. The porosity of the unloaded marble developed gradually and increased exponentially with the increase of the number of freeze-thaw cycles, the compressive strength and elastic modulus had a negative exponential relationship with the number of freeze-thaw cycles, and the shear strength parameter had a quadratic polynomial relationship with the number of freeze-thaw cycles. In addition, the softening mechanism of unloaded marble by natural water plays a key role in the process of freeze-thaw cycle, and the damage model considering freeze-thaw is established, and the theoretical curves are well matched with the experimental results. The outcomes of this study hold significant theoretical and engineering importance for evaluating the stability of excavated unloaded rock in highland alpine regions.