OPTIMUM USE OF POLYPROPYLENE FIBERS IMPROVES SOIL PROPERTIES

ABSTRACT Soil being the cheapest and readily available construction material has been popular, even though it suffers from being poor in mechanical properties. It has been the constant endeavor of research workers to put forth innovative ideas to improve its mechanical properties to suit the requirements of engineering structures, Vidal in 1968 postulated the new oriented concept of reinforced earth technique. Reinforced earth is a construction material composed of soil fill, strengthened by inclusion of rods, bars, fibers or nets that interact with the soil by means of frictional resistance and act as a coherent mass. It is used in a variety of applications such as retaining structures, embankment, stabilization of subgrade and improvement of soil beneath pavements and footings. Fiber reinforcement technique permits use of natural as well as synthetic fibers for soil reinforcement. In Maharashtra black cotton soil is found in abundance which is highly expansive soil. In present study an attempt has been made to investigate the use of polypropylene fibers for improving properties of locally available soil. The comparison of properties of soil with addition of varying percentages of fibers by dry weight of soil and having different aspect ratios is also carried out. The addition of polypropylene fibers resulted in increase in optimum moisture content and decrease in maximum dry density. Direct shear tests conducted on soil shows increase in value of cohesion and decrease in value of angle of internal friction. With the inclusion of the fibers increase in C. B. R. value and unconfined compressive strength is observed.