Mechanical behaviour of unsaturated kaolin (with isotropic and anisotropic stress history). Part 2: performance under shear loading

Validation of a framework for unsaturated soil behaviour has frequently resulted in disagreement with basic propositions. A primary reason for this disparity is considered to be attributable to the anisotropic properties of the soil specimens tested as a result of preparation using one-dimensional compaction. As part of the work presented, comparison is made between tests on samples of unsaturated kaolin prepared at identical specific volumes and specific water volumes using isotropic compression and one-dimensional compression. The suctions in the samples were reduced to predefined values by wetting under low isotropic loading in a triaxial cell. The samples were then taken through various stress paths to failure, defined as the critical state strength, while the suctions were held constant. Stress path tests were also performed on samples without reducing the suction to predefined values. In the latter, constant water mass tests, the suctions were allowed to vary and were measured using a psychrometer. The results of the tests at critical state are compared with the propositions of Wheeler and Sivakumar. The shear strengths of samples with isotropic previous history are shown to be significantly greater than those of samples with one-dimensional stress history when plotted against the mean net stress. The normal compression lines, critical state lines and yield characteristics are also shown to be significantly influenced by the previous stress history and are shown to be different for isotropically and one-dimensionally prepared samples.

Effect of batch size on mechanical properties of granules in high shear granulation

The flow patterns in a high shear granulator depend on the fill volume. For example, DEM simulations reported by Terashita et al. [1] show that fill volume affects the velocities and kinetic energies of the particles. It also influences the granule size distribution [2]. Here the effects on the properties of the granule are described. The total mass of the granulate material was varied without changing the other variables such as impeller speed, granulation time and liquid to solid ratio. The resulting mechanical properties, such as strength, yield stress and Young's modulus, of the granules were measured. For the materials studied in the current work, increasing the fill factor (batch size) increased the values of these material parameters. This could be explained by the relative increase in the number and intensity of collisions between the particles, when the size of a batch was increased, leading to smaller porosities. (c) 2010 Elsevier B.V. All rights reserved.