Effects of temperature and acid solution on the physical and tensile mechanical properties of red sandstones.

Recent infrastructure development in China and other developing countries has attracted global attention. As a control project of traffic engineering, tunnels also have rapidly increased. However, fire accidents induced by traffic accident or gas explosion frequently occur in tunnels, causing irreversible damage to the tunnel rocks. Moreover, the corrosive effects of acid rain or polluted groundwater have a long-term effect on the tunnel and surrounding rocks. In this paper, physical and thermophysical properties tests as well as Brazilian splitting test were conducted on red sandstone specimens after heating at a variety of different temperature and acidic solution erosion. The responses of surface features, mass, P wave velocity, porosity and thermal conductivity, and the tensile strength of the red sandstone were compared and analyzed. In addition, the effects of high temperature (25-1000 °C) and acidic solution on microscopic structures, defect morphology, and mineral reaction of the red sandstone were observed and analyzed. The experimental results show that high temperature and acidic chemical solution significantly affects the physical and mechanical properties of the rock mass. The typical parameters, such as surface features, mass and P wave velocity, porosity, thermal conductivity, and tensile strength, are closely affected by acidity. In addition, we observed that the physical properties of red sandstones change with temperature and can be divided into three stages, and at 300-800 °C stage, they significantly declined. The results provide a basis for rock damage and failure induced by fire and acidic groundwater seepage in tunnels.