Influence of moisture content and intermediate principal stress on cracking behavior of sandstone subjected to true triaxial unloading conditions

•True triaxial unloading tests were performed on sandstone with various moisture contents.•Slabbing is more prone to occur in higher moisture conditions for a constant σ2 level.•Moisture contents and σ2 may affect the failure intensity and fragmentation degree of sandstone.•The cracking mode was evaluated via AE features and microscopic morphological characteristics.•The cracking mechanism of immersed sandstone was revealed under true triaxial unloading condition.