Effect of the Position of Geotextiles on the Strength Characteristics of Subgrade Soil in Bituminous Pavements

Abstract

In the past 20 years, many new road improvement techniques have revolved around the use of geosynthetics. Geosynthetics may be used in those areas where the soil remains saturated part of the year or over clay and moist silty weak subgrade soils. The quality and life of pavement is greatly affected by the type of subgrade, subbase and base course materials. Subgrade soil is the bottom most layer of the pavement whether it is rigid or flexible. The function of the subgrade is to give adequate support to the road crust and to support the traffic in the form of foundation. The California bearing ratio (CBR) of these subgrade soils has very low, resulting in more thickness of the road crust. Replacing of these existing weak subgrade soil may not be good option, thus it is required to stabilize these weak subgrade soil with suitable stabilizer. Geosynthetics have been found to be a cost effective alternative to improve the weak subgrade soils in adverse locations. In this study, firstly the various properties of soil sample like grain size analysis, liquid limit, plastic limit, plasticity index and identification of soil has been evaluated and then CBR values of the soil have been improved using geotextiles. Nonwoven geotextiles are placed at different layers of various soil samples, and then a series of CBR tests were conducted to evaluate the strength of the subgrade soil. From this study, single layer of nonwoven geotextiles is introduced at the depth of 0.85H from the bottom of the mould shows better performance than those samples with the geotextiles layer are placed at other depths.