Experimental Study on Long-Term Mechanical Properties of Red Sandstone under Hydrochemical Effect

Serious environmental pollution exacerbates the extent of water-rock interaction. The physical and mechanical properties as well as microstructure of engineering rock mass are changed due to the water-rock interaction, having a significant effect on the long-term stability of rock engineering. Creep characteristic of rock plays an important role in analyzing and evaluating the long-term stability of rock mass engineering. In order to investigate the creep mechanical behavior and hydrochemical corrosion mechanism of red sandstone under water-rock interaction, the red sandstone from Taoyuan hydropower station in Hunan province was taken as the research object, and then a series of triaxial compression creep tests were performed on the red sandstone after immersing into salt solutions with different ion concentrations and pH values. The results show that: The water-rock chemical corrosion damage of red sandstone is closely correlated to the ion concentration and pH value of salt solution. The stronger the acid-base property and the higher the ion concentration are, the greater the secondary porosity and the bigger the volumetric expansion deformation is. Meanwhile, the creep deformation and instantaneous deformation increase. Nevertheless, the long-term strength shows a decreasing tendency when the ion concentration increases or the pH value decreases. The sensitivity of red sandstone to chemical solution is as follows: acidic salt solution＞alkaline salt solution＞neutral salt solution＞distill water. The curves of axial steady-state creep strain rate versus deviatoric stress all exhibit a “S”-shaped characteristic. The relationship of axial steady-state creep strain rate with deviatoric pressure can be well described by an exponential function. Based on the experimental results, the hydrochemical corrosion mechanism on creep behavior of red sandstone is preliminarily discussed.