Freeze–thaw–induced microstructural alterations and deterioration of physicomechanical properties in rocks from the Himalayan ranges (Pakistan)

This study investigates in detail the impact of freeze-thaw cycles on the physical and mechanical properties of a variety of rock types, including granulite, amphibolite, limestone, sandstone, granitic gneiss, quartzite, rhyolite, dolerite, and gabbronorite. The selected rock samples underwent several freeze-thaw cycles at temperatures ranging from 25°C to -40°C. After these cycles, tests were performed to assess the response of the rocks to varying temperatures. Destructive tests (uniaxial compressive strength, point load index) and non-destructive testing (specific gravity, ultrasonic pulse wave velocity, porosity, and water absorption) were carried out. The density of the induced fractures in each type of rock under investigation was calculated. The fracture density in the samples increased as the number of cycles increased. After fifty cycles, the fracture density of selected rocks increased as follows: 1.12% for sandstone, 1.06% for limestone, 0.59% for rhyolite, 0.48% for gabbronorite, 0.57% for quartzite, 0.76% for granitic gneiss, 0.46% for amphibolite, and 0.43% for granulite. The extent and strength of the fractures increased further with continued cycles. After 100 freeze-thaw cycles, the fracture densities rose to 1.47%, 1.44%, 1.22%, 1.05%, 1.14%, 1.31%, 1.03%, and 1.02%, respectively. Similarly, porosity and water absorption levels showed an increased trend. However, as the freeze-thaw process continues, the results indicate a decrease in uniaxial compressive strength (UCS), specific gravity, ultrasonic pulse velocity (UPV), and point load strength. These findings highlight how freeze-thaw conditions deteriorate rocks and change their physico-mechanical characteristics, with significant implications for the mining and building sectors.