Establishing Empirical Relationships for the Effects of Water Content on the Mechanical Behavior of Gosford Sandstone

A comprehensive set of empirical relationships for the effects of water content on the mechanical properties of Gosford sandstone was established. Gosford sandstone forms a unit within the massive Triassic Hawkesbury sandstone of the Sydney Basin, New South Wales, Australia. In this study, a number of experiments were performed on samples of Gosford sandstone including uniaxial compressive, point-load and Brazilian tests according to International Society for Rock Mechanics (ISRM). The rock samples were homogenous and free of any coloring or macroscale defects. The uniaxial compressive tests were nominally conducted under drained condition where the samples were not jacketed. However, during the experiment some water may remain far from the pressure equilibrium at the center of the sample since the imposed strain rate may be too fast compared to the time scale of pressure diffusion. It was observed that all the mechanical parameters decreased with an increase in water content. The role of water content can be explained through its effects on some intrinsic strength parameters of rock samples such as friction coefficient, fracture toughness and initial damage which all contribute to micromechanical and macroscale failure of rock. Also, it was found that the axial point loading on the partially saturated Gosford sandstone samples leads to invalid test results.