Evaluation of Geotechnical Properties of Black Cotton Soil Reinforced with Sisal Fibre for Waste Containment Application

Abstract

Compacted Black Cotton Soils (BCS) used in geotechnical constructions such as dams and clayey liners in waste containment facilities can suffer from cracking due to swelling and shrinking during wet and dry seasons respectively. In order to reduce the shrinkage of the clayey soil, discrete fibre reinforcement such as the Sisal Fibre (SF) technique was used. An experimental study was carried out on the natural and the modified properties of the soil which include Atterberg limits, compaction, Unconfined compressive strength UCS (i.e., for varying Moulding Water Content (MWC) relative to Optimum Moisture Content (OMC); OMC-2, OMC, OMC+2, OMC+4) and Volumetric Shrinkage Strain (VSS) at MWC relative to OMC; (OMC-2, OMC, OMC+2, OMC+4) were determined, for different percentages inclusion of sisal fibre (0, 0.5, 1, 1.5 and 2% SF). Results obtained show that the liquid limit and plasticity index of the natural soil are 44.47% and 18.65% which increased with an increase in the sisal fibre content. OMC increased from a value of 19% for the natural soil to a peak value of 24.5% at 1.5% of sisal fibre and thereafter decreased. The natural soil has a Maximum Dry Density (MDD) of 1.55 Mg/m³ which decreased to 1.5 Mg/m³ at 1.5% additive. The VSS of the modified soil significantly decrease compared to the natural soil and it continually decreased as the percentage of sisal fibre increased. The lowest VSS values were observed at 2% SF, having values of 2.85, 3.5, 4.75, and 5.5% for OMC-2, OMC, OMC+2, and OMC+4, respectively. The UCS initially increased and thereafter decreased. Based on the results, soil optimally treated with a maximum of 0.5% sisal fibre and compacted with OMC-2 significantly improved the soil and is recommended for use in waste containment applications.