Experimental research on damage characteristics of red sandstone under the combined action of temperature, water and stress

Abstract

In order to study the damage properties of red sandstone under combined action of temperature, water and stress, the uniaxial compression test was carried out for red sandstone after immersing in water for 0.5 hours, 1 hour and 3 hours at 25℃, 55℃, 85℃ and 95℃, the mechanical properties, characteristic stress points, acoustic emission RA-AF parameters and failure forms of red sandstone were analyzed, the damage constitutive equation was established, and the damage properties of red sandstone were studied. The results showed: (1) Temperature could significantly improve the saturated water content percentage of red sandstone. With the increase of temperature, the saturated water content percentage showed a trend of increase first and then decrease, and was the largest at 55℃; with the increase of temperature, the mechanical parameters (peak intensity, elasticity modulus, and stress at start point of expansion) decreased first and then increased, and was the smallest at 55℃; (2) The ratio of crack initiation stress to peak stress (σci/σf) increased first and then decreased at the same time of immersing in water as temperature increased, and decreased first and then increased as the time of immersing in water increased at the same temperature; (3) Acoustic emission RA-AF signals are primarily found in the stable and unstable crack extension stages, with most signals concentrated in the tensile areas. As immersion time increases, there is a gradual decrease in the total number of signals, while the proportion of signals in the shearing areas significantly increases. This is relatively consistent with the patterns of failure observed in red sandstone experiments; (4) The damage of temperature, water and stress on red sandstone is categorized into initial damage and load damage, and the damage constitutive equation of red sandstone under the joint action of temperature-water-load is established, which is applicable to red sandstone in water-saturated state below 100℃, The research results can provide certain theoretical references for practical engineering.