Reinforcement of clay soil using sisal fibre to improve subgrade soil strength
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Date
2023-07-15Author
Nitusiima, Lucy
Yiga, Sharif Muhammad
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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.