Effect of wetting-drying cycles on mode I and mode II fracture toughness of sandstone in natural (pH=7) and acidic (pH=3) environments

Factors such as rainfall and its diffusion into the ground and the subsequent drying cause alternating water-stone interactions leading to loosening of stones in long periods and catastrophic events such as landslides. Accordingly, the effect of these factors on the mode I and mode II fracture toughness of sandstone was investigated. Experiments were conducted on centrally cracked Brazilian disc (CCBD) specimens (chevron notch). The specimens were tested after 0, 1, 4, 8, 16 and 20 wetting-drying cycles (in the neutral (pH = 7) and acidic (pH = 3) environments). In addition to the effect of wetting-drying cycles in the natural environment (pH = 7), the effects of salt weathering and chemical weathering (caused by acidic environment) on the fracture toughness were also investigated. The acidic solution consisted of water, hydrochloric acid and sodium sulfate. The mode I and mode II fracture toughness of the sandstone decreased in both natural and acidic environments with increasing the number of wetting-drying cycles. The sandstone was also evaluated in terms of effective porosity and mineralogy to compare the natural and acidic environments. The results showed the insignificant impact of the acidic environment on the sandstone specimen. The effective porosity of the sandstone specimens also increased with increasing the number of cycles.