Experimental Investigation on the Behaviour of Glass Fibre-Reinforced Cohesive Soil for Application as Pavement Subgrade Material

Proctor compaction and California bearing ratio (CBR) tests were performed on glass fibre-reinforced cohesive soil to investigate its suitability as a subgrade material. The effects of varying fibre content, fibre length, compacted moisture content and soaking period on CBR and secant modulus were investigated. The test results indicate marginal variation of MDU and OMC with glass fibre reinforcement. Unsoaked CBR test was conducted on specimens compacted at optimum moisture content (OMC) and at 2% wet and dry sides of OMC, whereas soaked CBR test was conducted only on specimens compacted at OMC. CBR value increases with penetration depth up to 5.08 and 7.62 mm under unsoaked and soaked conditions, respectively. Both CBR and secant modulus increase with fiber content and fiber length at any compacted state. They decrease on either side of OMC, and also with increasing soaking period. The reinforcement benefit increases with increasing fiber content up to 0.75% for any fiber length and testing condition. The maximum enhancement in CBR are 2.77 and 2.85 times with 0.75% fibre reinforcement of 20 mm length, under unsoaked and soaked conditions, respectively. Using the glass fibre-reinforced soil in the subgrade may cause reduction of pavement thickness up to 25% even for a traffic value of 150 msa.