Interface Properties of Synthetic Rock Specimens: Experimental and Numerical Investigation

Abstract

Abstract To support the development of centrifuge models to simulate seismic rock slope failures, potential model materials were subjected to direct shear tests to characterize the properties of the interfaces. Three synthetic rock materials were investigated: blocks cast out of a commercially available gypsum cement, blocks cast out of a Nevada sand/gypsum mix, and rock blocks with sandpaper glued to the shear surfaces. The materials were evaluated primarily on the consistency of the measured properties and the observed shear failure behavior. The laboratory direct shear tests were modeled numerically with the software package UDEC to observe how well the numerical results using joint constitutive models available in the software compare to the experimental results. The Coulomb slip joint model predicts the interface behavior well for the gypsum and sand/gypsum materials, which displayed basic elastic-plastic behavior during shear, and the Coulomb slip with residual strength model captured the peak to residual behavior observed in the tests on the sandpaper interfaces. The use of a different joint shear stiffness value for each simulation, corresponding to the measured laboratory value associated with each applied normal stress, clearly contributed to this excellent match; more general models utilizing a constant joint shear stiffness value applied to blocks that are subjected to different normal stresses may not display such close agreement with observed behavior.