Effect of Freeze-Thaw and Heating-Cooling Processes on Permeability of Lushan Sandstone

Rocks are usually exposed to freeze-thaw and/or heating-cooling conditions in many environments. In this research, sandstone specimens of Lushan area were used and investigated the impact of number of freeze-thaw cycles and the effect of temperature in the heating-cooling process on sandstone permeability. The freezing temperature of -16°C was considered to study the effect of number of cycles. In this state, the tests were carried out on the specimens withstood 1, 5, 10, and 20 freeze-thaw cycles. To study the effect of heating-cooling, the tests were conducted on the specimens that withstood one heating-cooling cycle. The specimens withstood temperatures of 60, 100, 200, 400, 600, 800, and 1000 °C at the heating process and then cooled in the laboratory environment. Results indicated that permeability rate reduced after one cycle of freeze-thaw cycles the reduction continued to 5 cycles. Permeability increased slightly in 10 cycles and the increase was significant in 20 cycles. Sandstone permeability reduced up to 100 °C and then increased with the temperature increasing at the heating-cooling process. Permeability changes in the heating-cooling process were consistent with the variations of velocity of longitudinal waves, dry unit weight, and effective porosity.