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.
