Influence of Water on the Mechanical Properties and Failure Behaviors of Sandstone Under Triaxial Compression.

Water is a crucial factor that influences the mechanical behavior of rock and can induce failure. The aim of this study was to investigate the effects of water content and water distribution on the mechanical behavior of sandstone subjected to triaxial compression. Sandstone samples under different water states, including dry, unsaturated, saturated, and long-term saturated, were prepared. Some saturated samples were dried in air for different periods to prepare samples that were dry on the outside but remained wet on the inside. The triaxial compression tests were performed on the samples under four confining pressures: 5, 10, 15 and 25 MPa. The results indicated that the water state of a sandstone sample can be characterized by its water content, soaking time, water distribution, and long-term saturation. The different water states can affect remarkably the strength, deformation, and failure pattern of the sandstone samples subjected to triaxial compression. Several empirical equations were established to describe the evolution of the mechanical behavior of sandstone with increasing water content and soaking duration. The nonuniform distribution of water promotes the generation of tensile cracks, while increasing confining pressure promotes the development of shear cracks. The strength of sandstone samples with dry outside and wet inside are lower than that of samples with wet outside and dry inside. What is more, a long-term saturated state increases the strain-softening of the sandstone samples, thereby increasing their deformation and lowering their strength. Highlights: Influence of water state including water content and water distribution on sandstone is comprehensively investigated by triaxial experiments. A series of predictive empirical equations are established to describe the evolutions of the mechanical properties of sandstone with water content/soaking duration. The strengths of the sandstone samples in the dry outside but wet inside state are smaller than those of samples in the wet outside but dry inside state. A long-term saturated state increases the softening of the rock, thereby increasing the deformation and lowering the strength. Water especially nonuniformly distributed water promotes the propagation of tensile cracks near the surface of the rock. [ABSTRACT FROM AUTHOR]