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Bearing ratio of a fine soil reinforced with geosynthetics: influence of the reinforcement type and the soil water content

This paper reports an investigation on the effects of reinforcing a fine soil with three different geosynthetic solutions and their behaviour under loading. The effectiveness of the reinforcement was investigated through California Bearing Ratio, CBR, tests. The reinforcement solutions tested were: geogrid (GGR), geocomposite (GCR), association of geogrid and geotextile (GGR + GTX). The response of the unreinforced fine soil was compared to those of the same soil with one layer of reinforcement. The influence of the initial water content of the soil on the bearing capacity was analysed using five different values (11.9%; 13.9% (optimum); 15%; 17% and 19%). Including a layer of reinforcement improved the bearing capacity ratio and the stiffness of the samples. The best improvement in bearing capacity was found for GGR, followed by GGR + GTX and then GCR, and can be explained by the differences in stiffness and structure of the reinforcements. The mobilisation of the reinforcement depended on the type of reinforcement, the initial water content of the sample and the penetration induced to the sample. The soil initial water content affected the response significantly. Higher initial water contents lead to lower CBR values, for both unreinforced and reinforced samples. However, the effectiveness of each reinforcement varied with the initial water content; for GGR and GGR + GTX an initial water content of 17% lead to the higher bearing capacity ratio, while for GCR this occurred for the lowest value of the initial water content considered (11.9%).