EFFECT OF FIBRE LENGTH ON POLYESTER FIBRE REINFORCED SOIL

Abstract

Economy has always been a top consideration factor before carrying out construction of any kind. Achieving higher value of the strength parameters, with a controlled increase in cost of the foreign material leading to an overall decrease in the net construction cost, is always a sign of development. In the case of geotechnical engineering the idea of inserting fibrous materials in a soil mass in order to improve its mechanical behavior has become very popular. The concept of earth reinforcement is an ancient technique and demonstrated abundantly in nature by animals, birds and the action of tree roots. This reinforcement resists tensile stress developed within the soil mass thereby restricting shear failure. The reinforcement interacts with the soil through friction and adhesion. To improve the mechanical properties of soils, a variety of materials are used for reinforcement e.g. metallic elements, Geo-synthetics etc. Majority of geo-synthetics used in civil engineering application are polymeric in composition. In this investigation Recron 3s polyester fibre manufactured by Reliance India Ltd., has been used. Polyester Fibres are engineered Micro Fibers with a unique “Triangular” Cross-section shape. In this study 6 mm and 12 mm length polyester fibres were used. Test specimens were prepared with varying percentages of 6 mm and 12 mm polyester fibre (non-reinforced, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% and 1.0%) by the weight of dry soil.Two types of soil, Sandy and Clayey were used in the investigation. 42 modified proctor compaction tests and 129 California Bearing Ratio tests were carried out. Experimental investigations were undertaken to study the effect of polyester fibre on California Bearing Ratio value of soil. The fibre reinforcement significantly changes and improves the CBR value. The study has shown that there was a gain in California Bearing Ratio value for both types of soil and for both length of fibres. Mathematical Relations were derived using curve-fitting method between percentage gain in California Bearing Ratio value and Amount of polyester fibre added in percentage. A computer program has been prepared in Visual Basic .Net using Microsoft Visual Studio 2010 which gives us the percentage requirement of fibre addition to obtain to desired gain in California Bearing Ratio Value.