Developing an Empirical Correlation between DCPT Test Results and Relative Compaction for Sandy soils

Abstract

The dynamic cone penetrometer (DCPT) is a simple portable in-situ testing instrument. It is usually used to measure the resistance of cohesionless granular soil. An attempt has been made to find a correlation between the DCPT results and the in-situ dry density for local Tripoli sand. Laboratory and fieldwork were carried out to investigate the relationship between the dry and wet densities and DCPT blow count (N10, Blows/100). In this study, the relationships between laboratory N10 and dry density were developed and verified. The work was conducted in two stages; in the first stage the samples were tested normally, while in the second stage the tests were conducted using surcharge load discs. Due to the lack of confinement at shallow depths, surcharge load disc was used on soil sample surface to evaluate the effect of the unconfinement on the results of the DCPT at the shallow depth (i.e. 250 mm to 300 mm). The test results in the first stage showed a good impression for the dry density of sandy soil (SP-SM) at depths greater than 250 mm. As results, the aid of the surcharge discs showed better trends. The validity of the proposed correlations was verified using test results on soils at new sites. The obtained results gave a more representative and reliable correlation. Measured densities versus estimated ones were plotted, shown the ability of the proposed correlation in estimating dry density from DCPT at proposed site. The proposed correlations are useful tools to help engineers in the practice to use in geotechnical investigation and to assess the dry density of soils.