Effects of Soldier-Ant Mound (SAM) on the Strength Characteristics of Lateritic Clay Soils

Abstract

The aim of this work is to investigate the effect of Soldier-Ant Mound (SAM) on the strength characteristics of lateritic clay soils in order to improve their poor geotechnical properties for road pavement construction. Three soil samples were collected from a burrow pit along the Lagos-Ibadan Expressway, Lagos, Nigeria. The samples were mixed with Soldier-Ant Mound in various proportions (0%, 2%, 4%, 6%, 8% and10% by weight) and subjected to soil strength tests: Compaction tests, California Bearing Ratio (CBR) and Unconfined Compressive Strength tests at the University of Lagos, Nigeria between June 2012 and July 2013. Results obtained were compared with the natural soil and standard values. The Atomic Absorption Spectroscopy, AAS, gave the exchangeable cations present in the Soldier-Ant Mound as: Calcium (Ca2+), Magnesium (Mg2+), Sodium (Na+), Potassium (K+) and Aluminium (Al3+). The plasticity index decreased with increase in SAM content which signifies a reduction in any swelling and deformation that may take place. The maximum dry density, soaked CBR and Unconfined Compressive Strength all increased with increase in SAM content. The addition of 10% SAM content reduced the plasticity index by 7.5% (from 25.8% to 23.9%) and increased the maximum dry density of the clay soil from 1660kg/m3 to 1750kg/m3 which is considered satisfactory to excellent. The Optimum moisture content of the clay soil was reduced by about 15%. The addition of 10% SAM increased the soaked CBR by 85% (from 10.43% to 19.35%) while the unconfined compressive strength of the Lateritic Clay Soil increased by 122% (from 40.32kN/m2 to 89.36kN/m2). Soldier-Ant Mound significantly improved the engineering properties of Lateritic Clay Soil. The results indicate that there is a potential in the use of Soldier-Ant Mound for improving the strength characteristics of lateritic soils for road pavement construction and other earth works.