Some studies on morphology of the coarse-grained soils

Soil is a particulate material and its engineering properties are mainly controlled by the particle size and shape (i.e., morphological characteristics). In this context, earlier researchers have demonstrated dependence of soil specific parameters like permeability, shear strength, electrical conductivity, thermal conductivity and dielectric characteristics on particle morphology. It has been observed that to establish the morphology of soil particles, state-of-the-art techniques like confocal microscopy, 3-D laser microscopy and laser obscuration time method have been developed and adopted. By employing these techniques, parameters like particle size, roundness, sphericity and roughness, which are indicators of the particle morphology, have been established. However, it has been realized that each of these techniques exhibit several limitations, mainly due to the presence of a wide range of particle sizes in the soil mass. This necessitates a systematic study of the data obtained from these techniques, on the same material, to select the best technique for determining soil morphology. With this in view, morphology of different coarse-grained materials (sands and fly ash cenospheres) was investigated by employing the abovementioned techniques and the results of these tests are compared.

► Relationship between the grain size and morphology has been established.
► Three state-of-the-art techniques have been employed to determine S, R and ξ.
► A critical commentary on techniques for determining morphology of coarse grained soils
► A ‘look up table’ highlighting the pros and cons of techniques has been developed