Experimental Investigation on the Influence of Water Content on Mechanical Properties and Failure Characteristics of Tuff

In order to explore the influence of water content on the mechanical properties and failure characteristics of tuff, uniaxial compression experiments are conducted for tuff with different drying times. The tuff samples are divided into three groups by different drying time named group #, group H and group G, with the drying time increasing in turn. The change rate of water content (WCR) in group H increases linearly with drying time, while that in group G increases steeply first and then slowly, and finally tends to be stable with the mean of WCR at 2.58%. The WCR of tuff is negatively correlated with the mechanical parameters such as the uniaxial compressive strength, and is directly proportional to the coefficient CV of the discreteness in mechanical parameters for each group samples, which means that the lower the WCR, the higher the tuff strength, and the smaller the discreteness in mechanical parameters of same group rock samples. The coincident degree of the stress–strain curves of rock samples in group # and group H is high at the fracture compaction stage, while the difference is obvious in the curves of tuff sample for group G. The rock samples of group # are affected by the pore water pressure, and the microscopic tensile failure characteristics are significant. The specimens of group # show a “shear-tension” mixed failure, and the samples in group H and group G are affected by the localized defects to appear shear failure.