Deformation and Failure Characteristics of Uniaxial Compression Prestressed Red Sandstone Under Short‐Term Immersion Conditions

To study the impact of short‐term water immersion on rock structures during water inrush or storage, a series of water immersion uniaxial compression (UC) tests were conducted on prestressed red sandstone. The effects of prestress levels (0, 0.5 σ c0 , 0.7 σ c0 , and 0.8 σ c0 ; σ c0 is the uniaxial compressive strength) and immersion heights (0, 1/8 H , 1/4 H , 1/2 H , and H ; H is the specimen height) on the deformation, strength, and failure characteristics of red sandstone were analyzed. Furthermore, recommendations for treating underground rock structures affected by short‐term water immersion were proposed. The results indicate that: during the prestress immersion stage, the deformation of the specimen with 0.5 σ c0 tends to stabilize; the specimen with 0.7 σ c0 maintains slow deformation and no failure; and immersion can cause failure to the specimen with 0.8 σ c0 . The strength of red sandstone first increases and then decreases with the increase of prestress, reaching its maximum at 0.5 σ c0 . The strength of red sandstone decreases with the increase of immersion height. Partially immersed specimens demonstrate nonuniform failure characteristics, with cracks and surface spalling preferentially occurring in wetted regions. Moreover, as immersion height increases, the spalling area before specimen failure expands. An optimal prestress range exists for red sandstone under short‐term immersion, within which the weakening effect of water on strength is minimized.