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Influence of density on suffusion behaviour of binary granular packings Suffosion is a hydromechanical process that describes a rearrangement and transport of fine particles in soil as a result of water flow. In order to understand the effects of material loss due to suffosion on material behaviour, the influence of density on the mass of material loss, volumetric deformation and the change in permeability was investigated. For this purpose, the structure (contact and contact force distribution) of a soil susceptible to suffosion was qualitatively simulated and analysed with help of DEM. The effects of different densities were investigated experimentally by means of laboratory tests under isotropic load and constant flow. A decrease in material loss, a decrease in deformation and a decrease in permeability due to suffosion with increasing material density were found. In order to be able to describe the change in mechanical behaviour, drained triaxial tests were carried out on non‐eroded and eroded samples, respectively. It was shown that the drained shear strength mainly depends on the void ratio of the coarse material before shearing, regardless of whether this was created artificially or as a result of flow. [ABSTRACT FROM AUTHOR]

The behaviour of granular materials, such as sands, is controlled by the interaction of particles. This interaction can be described geometrically by orientations and statically by forces. Using x‐ray μ‐tomography and image analysis, it is possible to determine the geometrical fabric at the grain‐scale, whereas the forces still remain inaccessible in natural granular materials. This article shows how the fabric can be accessed using standard and recently proposed advanced image analysis techniques and elaborates which problems arise when describing the fabric quantitatively. These techniques were applied to a triaxial compression test on Hostun sand. The results are described in terms of a fabric tensor, a coordination number and an anisotropy and then related to the macroscopic behaviour of the sample. [ABSTRACT FROM AUTHOR]

Comparative study on the compressibility and shear parameters of clay from oedometer and direct-shear tests. Results of oedometer and direct shear tests, which were performed in several laboratories, are compared and analysed. In order to obtain homogeneous and reproducible samples, a clayey soil was remolded and pre-consolidated. The handling of the soil specimens and detailed testing procedures were described and communicated to each participating laboratory. The evaluated soil properties scatter in a relatively wide range. The analysis of the results shows that a large part of the scatter originates from the testing conditions. [ABSTRACT FROM AUTHOR]

Experimental determination of the non-linearity of failure criteria in the low stress range. Earlier research has shown that the Mohr-Coulomb shear parameters φ' und c' are no material constants but state dependent parameters. Consequently, the failure criterion of overconsolidated soils exhibits non-linearity, particularly under low confinement stresses, in the shape of a more or less pronounced curvature of the envelope towards the origin. With the help of experimental investigations, the evolution of the effective shear parameters as a function of mean stress and preconsolidation stress has been analysed. Soil samples of silty clay were preloaded to different overconsolidation ratios and stresses and sheared along unconventional stress paths in order to explore the low stress range, which is difficult to investigate by conventional triaxial compression tests. The experimental series has proven that especially the soil's maximum load influences the degree of non-linearity of the failure criterion: the higher the preconsolidation pressure, the more intense the curvature. The overconsolidation ratio on the other hand has a stronger impact on the stiffness of the soil, indirectly indicating a link between the volumetric response and the stress path followed. [ABSTRACT FROM AUTHOR]

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