Evaluation of the water weakening coefficient of sandstones by using non-destructive physical parameters

Introduction The presence of water significantly reduces the mechanical strength of rocks and induces various engineering geological hazards. The water weakening coefficient K p is used to quantify this effect, defined as the ratio of wet uniaxial compressive strength to the dry value. Methods A comprehensive physico-mechanical test was conducted on fifteen sandstones under dry and saturated conditions to predict the water weakening coefficient using easily obtainable physical parameters. Multiple linear regression was employed to establish the relationship between these parameters and the saturated water weakening coefficient. Results The saturated water weakening coefficient decreases with increasing porosity and increases with higher Primary wave velocity (P-wave velocity). Rocks with higher porosity but lower P-wave velocity typically absorb more water. The P-wave velocity and clay mineral content were identified as the best predictors of the saturated water weakening coefficient ( R 2 = 0.82). Unsaturated water weakening coefficients at any water saturation level were well estimated using a previous exponential function. Discussion The roles of different clay minerals and P-wave velocity in the water weakening process of rocks are comprehensively discussed. This study enhances the understanding of the water weakening mechanism and provides an improved evaluation model for the water weakening coefficient of sandstones using physical parameters.