Study on Pavement Soil Subgrade Properties with Reinforced Fibres

Abstract

The present examination researches the advantages of strengthening the subgrade soils in flexible pavements where two different types of fibres (jute and polypropylene fibre) were used and were randomly mixed with soil. Proctor test, unconfined compression test, California bearing ratio (CBR) test and triaxial test were conducted to evaluate the compressive and shear strength of subgrade soil. Both the fibres were added at various percentages (0.5–1.5%) by dry weight of soil for improving soil strength. The prime point of this examination is to assess the usefulness of fibres as soil reinforcement and to evaluate the effect of various percentages of fibre contents on the compressive strength and stiffness of subgrade soil. It is found from the results that maximum dry density decreases and optimum moisture content increases with an increase in fibre content. It is seen that the CBR value increases with an increase in fibre content up to a specific increment of fibre, yet diminishes with additional inclusion of fibre in soil. The maximum CBR value and compressive strength are found at 0.75% jute fibre and 1.0% polypropylene fibre content. The CBR value of the soaked unreinforced soil is 4.17%, which has increased to 8.97% and 10.61% for 0.75% jute fibre and 1.0% polypropylene fibre, respectively. Including of fibre improves the CBR value of soil which reduces the thickness of the pavement structure and in turn reduces construction cost of pavement structure.