Effect of chemical erosion and freeze-thaw cycling on the physical and mechanical characteristics of granites

摘要

Rocks in nature are very often subjected to weathering processes. The physical and mechanical properties of granites exposed to chemical erosion and frost attack were investigated experimentally. Granite specimens were immersed in water, NaOH solution and HNO3 solution for 90 days to simulate the chemical processes. Thereafter, frost attack simulated by cyclic freeze-thaw was conducted at different numbers of freeze-thaw cycles (0, 10, 25, 50, 75, and 100). The specimens were then tested under the uniaxial compressive loading condition. Changes in characteristics, including uniaxial compressive strength, axial strain, P-wave velocity, porosities and Young's modulus were recorded. Microscope images of surface microstructure and surface fracture morphology were also taken and analyzed. It was found that more cycles resulted in a rougher surface of the fracture. Granites immersed in HNO3 solution has a rougher surface of the fracture than those dipped into water and NaOH solution (for a fixed number of cycles). Furthermore, the degradation of the granite caused by weathering processes was evaluated by a damage variable determined in terms of porosity. It is obvious that deterioration of the granites increases steadily with an increasing number of freeze-thaw cycles. The biggest effect of chemical processes and cyclic freeze-thaw on the physical and mechanical properties of granite was observed in HNO3 solution.