Discrete Element Modelling of the Vibratory Unconfined Compression Tester (VUCT) for Cohesive Solids

Abstract

In a previous study, McGlinchey et al. [1] developed the Vibratory Unconfined Compression Tester (VUCT) as a tool to study materials under vibration. The testing machine (Figure 1) was based on a conventional unconfined axial compression system where the only inertial effects were at the axial boundaries to the sample. Vertical vibrations were imposed upon the base of the sample with controlled applied frequency and acceleration. Simultaneous axial compression was applied from the top during the vibration and rapid data collection systems were used. A cylindrical sample of a material was mounted on the vibrator base and then surmounted by a top cap mass. The compression was applied via a piston descending on a spring resting on the top cap mass at a constant rate. The process of controlled compression and simultaneous vibration continued until the sample failed. Vertical displacements of the spring, top cap mass and base, radial displacement of the sample at mid-height, and accelerations of the top cap mass and the base were measured. From these measurements the top cap stress, axial, radial, volumetric and shear strains, and the work done by the top cap mass were calculated. The test was applied on wet sand samples of length 76 mm and diameter 38 mm. We conducted a preliminary study using the discrete element method (DEM) to replicate some of McGlinchey et al.’s experiments. In this short communication a qualitative comparison between the simulations and the experiments is presented. We used DMX, DEM software developed by Asmar et al. [2,3] to conduct the studies. The contact forces considered in the model are elastic, cohesion, friction and