Vipulanandan Models to Predict the Mechanical Properties, Fracture Toughness, Pulse Velocity and Ultimate Shear Strength of Shale Rocks

Abstract

This study was focused on investigating the correlations between the physical and mechanical properties and geostatistical analysis of the shale rock based on the experimental data and the data collected from various research studies. In this study, over 250 data were used to characterize the shale rock behavior. The compressive strength and tensile strength of the shale rock investigated varied up to 200 and 13 MPa respectively. The shale rock was characterized based on the density, modulus of elasticity, fracture toughness and tensile strength and correlating the properties to compression strength and pulse velocity. Based on the statically analysis, the density of shale was in the range of 1.70–2.78 gm/cm3. Vipulanandan correlation model was effective in relating the modulus of elasticity, pulse velocity, fracture toughness with the compressive strength of the rocks. There was no direct correlation between the compressive strength and density or tensile strength and density of the shale rock. The new Vipulanandan failure model has been used to not only better quantify the tensile strength but also to predict the maximum shear stress of the rock. The prediction of the Vipulanandan failure model for shale rock type was also compared to the Mohr–Coulomb failure model. The Vipulanandan failure model has a maximum shear stress limit were, as the Mohr–Coulomb failure model did not have a limit on the maximum shear stress. Based on the Vipulanandan failure model the maximum shear stresses produced by the shale was 103 MPa. Based on the coefficient of determination (R2) and the root mean square error values, the Vipulanandan failure model predicted the results better than the Mohr–Coulomb model.