Creep behaviour of sandstone under different water conditions and its response to varying impact energy

Creep deformation and failure of immersed sandstone under mining disturbances are critical factors driving water inrush and goaf collapse. This study employed a specialized creep-impact testing system capable of simultaneous water immersion and mechanical loading, conducting uniaxial compression and creep-impact tests on sandstone samples in three moisture states: dry, saturated, and freshly immersed. The results show that as moisture content increases, both compressive strength and elastic modulus decline significantly. The most notable reductions occurred within the first 2 hours of immersion, with strength and modulus dropping by 55.7% and 70.1%, respectively. Under creep-impact conditions, increasing the impact energy from 14.7 J to 24.5 J caused accelerated creep failure in saturated samples, shortening failure time by 25.2% and increasing the creep rate to 1.32–1.64 times the initial value. In contrast, immersed samples exhibited both accelerated creep and abrupt failure, shortening failure time by 20% but increasing the creep rate more sharply to 2.11–6.04 times the initial value. Post-failure analysis revealed more pronounced fragmentation and a more violent failure process in immersed samples compared to dry or saturated counterparts. These findings offer valuable insights for deep mining operations and the prevention of water inrush disasters.