THE USE OF NATURAL GEOTEXTILES IN REINFORCING THE UNPAVED ROADS

The performance of unpaved and paved roads are improved with the inclusion of the geosynthetics. Many design procedures are developed to quantify the improvement and cost effectiveness. High cost of geosynthetics and unavailability of product makes the synthetic geotextile an overburden for the rural economy. The environmental impacts and disposal difficulties of the geosynthetics enforces for an alternative nature product, which is readily available and cost effective too. In this paper, the effect and advantages of natural geotextiles in reinforcing the subgrade of unpaved roads for improved performance will be discussed. 1 INTRODUCTION Substantial portion of Indian road network comprise of rural roads. The state of these roads defines the rural population's life quality. As per the World Bank report, in the year of 2011, it is estimated that 46.2 percent of total road network are unpaved roads. Unpaved roads are structurally supported by layer of sand or base aggregate placed over the subgrade without a bituminous wearing course. The major issues related to the rural roads are, most of them are constructed in weak subgrade. Even though the traffic flow is low, the proximity of these roads to the agricultural field, poor drainage system and infiltration of rain water through comparatively porous surface finish, softens the subgrade which causes large deformation/ rutting along the wheel paths. The loss of macadam into the soft subgrade through mud pumping will reduces the necessary minimum thickness of sub base/ base course layer accelerating the rutting phenomenon. The pavement performance of both paved and unpaved roads can be improved with the inclusion of geosynthetics. It is a quicker and easier solutions compared to traditional alternatives due to the ease of installation. Unavailability, high cost of geosynthetics, and stringent environmental protection requirement make it important to explore alternative natural products to make the constructions cost efficient and eco-friendly. Many efforts are done to utilize the geotextile made from natural fibers readily available in Indian sub- continent for reinforcing the unpaved roads. India and Srilanka shares the 90% of the world's production of coir and India is the largest jute producing country in the world. The usage of these materials can bring down the cost. This paper gives an overview of the effectiveness of usage of these natural geotextile products in reinforcing the unpaved roads. 2 MECHANISM OF GEOSYNTHETICS IN REINFORCING SUBGRADE The improvement in the performance of the unpaved roads using geosynthetics are due to the functions like separation, filtration, drainage and reinforcement action of the geosynthetics. The migration of fine particles from the subgrade into the base course causing the deterioration of the quality of the base course resulting the performance of the road. Geotextiles can be used as a separator as well as a filtrate to restrict the movement of the soil particles from the subgrade to the adjacent base coarse. The function of geotextile as separator, it must survive the construction procedure. The serviceability of the geotextile products during construction depends upon the subgrade condition, quality of the base coarse material and the construction equipment. The influence of geotextile as filtrate depends upon the parameter called permittivity and transmittivity. Permittivity evaluates the rate of water flow through the geotextile perpendicular to the plane of geotextile while the later evaluated the rate of water flow inplane to the geotextile. For retaining the fine aggregate the Apparent Opening size of the geotextile