Estimation of swelling potential of Enugu Shale using cost effective methods

Abstract

The behavior of swelling soils is mainly governed by its mineralogical composition as well as its environmental factors and stress history. Enugu Shale is one of these shales that assessment of its soil swelling potential cannot only be based on its mineralogical composition alone. The identification of its clay mineral types is basic to understand the roles of other factors of swelling in the soils. The results of particle size distribution indicated that Enugu Shale is dominated by fine-grains with average mean of 69.65, 23.68 sands and 6.67% gravels. While the Atterberg’s limit values are moderate to high, with liquid limit ranging from 22-66%, plastic limit 0-39% and plasticity index 0-39%, abundance of major elemental oxides show that SiO2 (50.4-88.1%), Al2O3 (6.29-28.23%) and Fe2O3 (0.98-12.25%) constitute over 90% of the bulk chemical compositions of the studied area. The studied area is dominated by A-7 soils and low plasticity clay soils according to AASHTO and USCS classification system. The results of free swell ratio range from 1.02-1.45 which indicates that studied area is dominated by mixture of swelling and non-swelling clay minerals. The Van der Merwe’s charts shows low to medium swelling potential. These results show that the study area is dominated by low to medium swelling soils which need to be modified and upgraded before it can be used as subgrade material. Key words: Swelling potential, Enugu Shale, free swelling ratio, correlation and Van der Merwe’s chart.