Alteration of Mesoscopic Properties and Mechanical Behavior of Sandstone Due to Hydro-Physical and Hydro-Chemical Effects

The hydro-physical and hydro-chemical interactions between groundwater and a rock mass can lead to changes in the mineral composition and structure of the rock (e.g., generation of voids and dissolution pores and an increase in the porosity), thereby altering the macroscopic mechanical characteristics of the rock mass. Sandstone specimens were saturated with distilled water and five aqueous solutions characterized by various ion concentrations and pH values for several months, and their porosity was measured in real time. Simultaneously, the concentration and pH of each aqueous solution were monitored every 30 days. The results indicate that after immersion in the aqueous solutions for 180 days, the porosity of the sandstone specimens and the ion concentrations and pH of the aqueous solutions tended to stabilize. Then, the immersed sandstone specimens were analyzed in thin section and subjected to computerized tomography scanning. It turns out that the mineral composition and structure of the specimens had all changed to various degrees. Finally, the uniaxial compression tests were conducted on the sandstone specimens to analyze the effects of the hydro-physical and hydro-chemical alteration on the macroscopic mechanical characteristics of the rock (e.g., the stress–strain relationship, elastic modulus, and peak strength). The results of this study can serve as a reference for investigations into theories and applications of water–rock interactions and for research in related fields.