Analysis of sand gradation effects on relative density

Abstract

The relative density is a better indicator for specifying the compaction of granular cohesionless soils i.e. coarser soil as compared to relative compaction. It has been also found that sands are a more preferred material for use as filling in foundation/base material because of its affinity to be less affected by pore moisture content as compared to cohesive soils. Practically it is very difficult to obtain homogeneous sands during various cut and fill operations or other purposes of construction. This leads to procuring sand from different sources, which result in heterogeneous properties in the sample used. From the literature survey carried out, it has been found that there has not been an appropriate effort to establish a relationship between relative density, bearing capacity and gradation of sand, i.e. the different proportions of coarse, medium and fine sand. Hence, an effort is being made to carry out an experimental study regarding the relation between the two and conclude with an empirical relation between the two. Erstwhile, sieve analysis and specific gravity test were carried out for the samples from the four sources to find out the natural proportion. After establishing the empirical relation between relative density and sand gradation, steps have been taken to carry the experiment further and relate the bearing capacity of the sample with the relative density for its easier application in the field. Finding the internal angle of friction from the direct shear test, the bearing capacity has been calculated in accordance with IS 6403:2002. The relation between relative density and internal angle of friction has been found in accordance with the Meyerhof’s relation, with an allowable error of ± 5 % from the ideal values.