Development of a correlation between Dynamic Cone Penetration Index and Level of Compaction for lateritic soil

Abstract

Quality control of compacted soil relies on the principle of determining the field dry density first followed by a comparison with the maximum dry density so as to determine the achieved level of compaction. This achieved level of compaction has to fulfill the minimum required specification standard for approvals to be made. However, the process of obtaining field dry density using sand replacement method is always delayed because of the long time needed during its process. This process can be simplified by the Dynamic Cone Penetrometer (DCP) because of its simplicity and capability of giving results faster. It is noted from the existing literature that the use of DCP is supported because of its different correlations but none of its correlation model is reliable in terms of determining the achieved level of compaction. This is because most of these correlations do not consider the effect of water content. The main objective of this study was to develop a correlation model that relates the level of compaction to Dynamic Con Penetration Index and water content. The soils used were collected from Namanve and Wakiso – Mende borrow pits. These were first tested and classified as G7 and G3 materials. Focus was put on the effect of water content on DCP test results and a linear model that relates level of compaction to Dynamic Cone Penetration Index and water content was developed using regression analysis. This model had an R2 value of 0.67 and has a component of water content which needs to first be determined such that DCP tool produces faster results. This study further looked for a quicker way of determining in-situ water content so as to solve the problem of water content parameter needed in the model. The speedy moisture tester is one of the quicker tools used to determine in-situ water content but this is challenged by the fact that its correlation charts that relates oven water content to speedy water content do not capture the effect of particle size and distribution (grading) for the sample being tested. Therefore, a correlation model that relates oven water content values to speedy water content values was developed with the consideration of effect of particle size distribution and this had an R2 value of 0.9869. These two models can be used in tandem to determine the level of compaction achieved when DCP tool is used for Quality Control of compacted soil.