Abstract
In the process of tunnel construction in western China, high ground temperatures and rich groundwater are frequently encountered. To find out the damage and failure characteristics of sandstone under temperature and water effects, uniaxial compression tests were conducted at different temperatures (25°C, 55°C, 85°C, 95°C) and immersion durations (0.5 h, 1 h, 3 h). Analysis of acoustic emission (AE) signals and energy evolution during the damage and failure processes provided insights into sandstone's damage characteristics and failure mechanisms. The following conclusions were drawn: (1) The increase in immersion time led to higher water content in sandstone, enhancing its plastic deformation capacity and reducing brittleness. The maximum water content occurred at 55°C, and after 3 hours of soaking, AE signal values were lowest across all temperatures. (2) As temperature increases, under conditions of 0.5-hour and 1-hour immersion, the maximum acoustic emission (AE) ringing counts and maximum AE energy at first rise with temperature, then decrease, and later increase again. Meanwhile, cumulative AE ringing counts show a gradual upward trend. After 3 hours of immersion, at each temperature condition, the maximum AE ringing counts, maximum energy, and cumulative ringing counts show an increasing trend with rising temperature. (3) The mechanical energy profile of sandstone varied with temperature and immersion duration. Total energy and elastic energy showed non-monotonic trends relative to temperature, with minimal values recorded at 55°C. Dissipation energy exhibited a characteristic increase and subsequent decrease, peaking before the ultimate failure point at 55°C. Notably, sandstone displayed diminished energy absorption capacity after 3 hours of immersion at any temperature. (4) Damage mechanisms were predominantly influenced by immersion time and temperature. Tensile damage was identified as the primary mode, with longer immersion times notably promoting shear crack development, while elevated temperatures facilitated the propagation of tensile cracks.