Failure characteristics and mechanisms of uniaxial compressed red sandstone in non-uniform water distribution environment: Effects of immersion height and duration

To investigate the influence of non-uniform water distribution on the mechanical properties and failure behavior of red sandstone, we designed five immersion heights and durations to achieve varying non-uniform water distribution states. Uniaxial compression tests were conducted on red sandstone under these conditions. The effects of non-uniform water distribution on deformation, failure, strength, and energy characteristics of red sandstone were analyzed. The impact of non-uniform water distribution on the intensity of rock failure was discussed, and the failure mechanism under non-uniform water distribution was revealed. The hazards of low immersion heights on underground rock structures were analyzed. The results demonstrate that peak strength and elastic modulus of red sandstone exhibit high sensitivity to immersion height, with reductions of 38% and 23% respectively even at L =1/50 H . Water immersion reduces both energy storage capacity and energy dissipation capability of red sandstone. The immersion height and duration influence the failure mode of red sandstone by controlling the migration and separation of dry-wet interfaces. Low immersion height poses significant risks to underground rock structures (e.g., a 38% strength reduction when L =1/50 H ), and the concentration degree of water non-uniform distribution is the key factor in assessing the weakening effect of water on rocks.