Failure regimes of single wet granular aggregate under shear

The behaviour of a single cluster aggregate made up of sticky wet granulates inside a Couette cell under constant shear has been numerically studied with the help of a Lattice Boltzmann model. Cluster composition and ratio of shear to capillary force present in the clusters have been found to be the two important factors in determining cluster behaviour. Clusters having size below a critical value are found to exhibit rigid translational and rotational movement; above this critical value the cluster breaks. Two broad failure regimes have been identified based on the relative magnitude of shear and capillary forces. For low values of the ratio the clusters are seen to undergo ductile failure either by thinning at the middle or due to severe coiling-recoiling action. At very high force ratios the clusters cannot withstand any shear and almost immediately breaks to form debri-like structures. Failure in these clusters is found to bring down the stress levels in the fluid. Increase in mass, less hysteresis in capillary forces, shear thinning base fluid and intrinsic voidage present in the clusters are found to make cluster-aggregates more susceptible to breakage.