Development and performance evaluation of a method to determine the maximum dry density of lateritic soils using specific gravity.

Abstract

Laboratory determination of Maximum Dry Density of soil is both time consuming and costly. Therefore, it is useful to develop simple correlation equations to estimate it using relatively easier index property tests. The aim of this study was to develop a method of determining the Maximum Dry Density of lateritic soils using Specific Gravity and to evaluate its performance. Based on the results of fourteen lateritic soil samples compacted using the Modified Proctor test following BS1377-1990 Part 4 and the Specific Gravity test determined as specified in BS1377-1990 Part 2, Maximum Dry Density was correlated with Specific Gravity. The tested samples were classified as clayey sand soils and clayey gravel soils using Particle Size Distribution and Atterberg Limits. Microsoft Excel was used to perform a Linear Regression Analysis in order to determine the numerical relationship between Maximum Dry Density and Specific Gravity. The coefficient of determination (R2) observed was 0.5459. The predictive performance of the relationship was assessed using five lateritic soil samples by comparing the MDD determined using the Proctor test and the MDD obtained from the numerical relationship. The accuracy of performance was observed as 94%. When data sets sourced from other researchers were used, the accuracy of performance was observed to be 88%. According to this study, Maximum Dry Density of a clayey coarse lateritic soil can be determined using a numerical relationship given by 𝑀𝐷𝐷 = 0.9343𝐺𝑠 − 0.6494. Since the relationship has an accuracy of performance of 94% on the samples sourced from Uganda, it can be applicable for subgrade of G3 and G7 material type given that they require a minimum attainment of Maximum Dry Density of 90% and 93% respectively according to the Ministry of Works and Transport General Specifications for Roads and Bridges, 2005.