Correlation of sampling effect in Hong Kong

Laboratory simulation of the field sampling process in the current practice and the investigation on the effect of sampling disturbance on the soils in terms of the dry densities employing two sampling tubes of different wall thickness are presented. Two types of residual soils most commonly found in Hong Kong, namely, decomposed granite and decomposed volcanics, were tested in the remoulded state under a wide range of moisture contents. The disturbed soil densities from the driven sampling tubes were compared with the soil densities prepared by different compaction operations. The results demonstrate that the sampling process yields very good samples of medium dense soils, but tends to densify loose soils and loosen dense soils. Correlation of dry densities were derived under different moisture contents, thicknesses of the sampling tube and degrees of compaction, which are useful in evaluating site investigations to truly reflect the subsurface soil properties.