Effect of particle characteristics on the strength and volume change behaviour of selected granular deposits of Bangladesh

Abstract

Granular soils from the river beds of Teesta, Jamuna and Meghna were collected from Rangpur, Tangail and Dhaka respectively. A sample of Dhaka sand was also collected from an excavated pond at Rajarbagh in Dhaka. The particle characteristics of these soil samples were determined from their sphericity, elongation and flakiness. The effect of their shape parameters on limiting densities, shear strength and volume change behaviour and critical void ratio were also studied. Drained triaxial tests were performed to determine the strength parameters for these soils. The ranges of sphericity, elongation and flakiness for the sands studied are 0.30 to 0.63, 1.12 to 1.55 and 2.25 to 9.18 respectively. The dry density of these soils ranges from 78 pcf at a void ratio of 1.36 to 106 pcf at a void ratio of 0.57. The angle of internal friction of these soils lies between 30° and 380 for relative density ranges between 0 and 80 percent. The critical void ratios lie between 0.68 to 1.02. From the analysis of the results of tests on above mentioned granular soils it is found that for any relative density the angle of internal friction increases with increasing elongation and flakiness of the particles but decreases with increasing sphericity of the particles and the higher the relative density the greater is the effect of shape of the particles on angle of internal friction. Also it is observed that sands with flaky and elongated particles undergo smaller change in volume during shear compared to sands with spherical particles. The critical void ratio of sands appeared to be smaller for sands with spherical particles. The maximum and minimum densities for sands with spherical particles are found to be lower than that for sands with elongated and flaky particles. The effect of shape on limiting void ratios are reverse.