Reinforcement of clay soil using sisal fibre to improve subgrade soil strength

Abstract

This final year project report presents an investigation into the reinforcement of clay soil using sisal fiber. The objectives of the study were to compare the mechanical properties of sisal fiber before and after chemical treatment, determine the engineering properties of clay soils, and establish the optimum sisal fiber length and content required to improve soil strength properties Soils with a CBR value of 3%, PI of 31.1%, UCS of 0.33Mpa and a liquid limit of 52.8% exhibited inadequate properties according to the general specifications for roads and bridge works requirement. In this study, sisal fiber underwent chemical treatment with sodium hydroxide to investigate its impact on the mechanical properties of the fiber, the engineering properties of the clay soil, such as CBR, PI, UCS, MDD and liquid limit were also determined to establish a baseline for comparison. To address the inadequate properties of the clay soil, various proportions of sisal fiber with different lengths were added to the soil samples and the mechanical tests conducted. The results demonstrated the significant improvement in soil properties achieved through the addition of sisal fiber, leading to enhanced stability and strength Based on the findings, it is recommended to add a minimum of 3% sisal fiber to effectively stabilize fine-grained soils, achieving a UCS of 0.56 MPa that conforms to the General Specifications for road and bridge works. The recommended minimum sisal fiber length is 10mm, while the maximum length is 30mm, resulting in a CBR of 13% and 16%, respectively, meeting the minimum California bearing ratio of 7% for lower subgrade (G7) Further more, further research is recommended to explore the impact of aspect ratio of sisal fiber in soil stabilization and investigate the use of crushed sisal fiber as an alternative reinforcement method.