Effect of the Position of Geotextile on the Strength Characteristics of Subgrade in Bituminous Pavements

Abstract

In the past 20 years, many new road improvement techniques have revolved around the use of geosynthetics. In India, most of the flexible pavements are need to be constructed over weak sub-grade having low modulus values. The California bearing ratio (CBR) of these sub-grade 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 & identification of soil has been evaluated and then CBR values of these soils have been improved using geotextiles. Non-Woven geotextiles are placed at different layers of various soil samples, and then a series of California Bearing Ratio (CBR) tests were conducted to evaluate the strength of the subgrade soil. It was observed that the CBR value increases, when the non-woven geotextile are placed at different layers of various soil sample. From this study, single layer of non-woven 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. In this study, the flexible pavement have been designed for both fatigue and rutting life of 100MSA at 90% and 80% reliability, when the non-woven geotextile are placed at three different depths of subgrade soil samples. The critical strain value for both fatigue and rutting life are analysed by programme IITPAVE software and are less than the allowable strain values as computed by IRC: 37-2012.