Soil Classification Through Penetration Tests

The Newcastle Dilatometer (NDMT) developed by Akbar in 2001 has a distinctive feature that it loads the soil with a rigid piston in place of flexible membrane as in the Marchetti Dilatometer (MDMT). Based on the previous research works carried out using the NDMT in normally consolidated soils, it has been found that the material and dilatometer indices from the NDMT data can be used to classify the soils based on Marchetti and Crapps (1981) chart. However, in overconsolidated soils, the Marchetti and Crapps (1981) chart for soil classification sometimes shows disagreement with other methods in the prediction of soil type based on the NDMT data. This is also true with the Cone Penetrometer (CPT) data. These findings are based on extensive testing carried out in alluvial soil deposits at Kala Shah Kaku campus of the University of Engineering and Technology, Lahore. These testing comprised particle size analysis in the laboratory in conjunction with the NDMT and CPT testing in the field. This paper presents the data of penetration tests along with laboratory soil classifications and explores the possible causes of disagreement in the prediction of true soil type based on penetration tests in overconsolidated soils.