Tensile behaviour analysis of compacted clayey soil reinforced with natural and synthetic fibers: effect of initial compaction conditions

Abstract

In this paper, the technique of soil reinforcement using short and randomly distributed fibres was proposed in order to evaluate its effect on tensile behaviour of compacted clayey soil. For that purpose, a new test method was developed using a specially designed direct tensile test apparatus. The device allows an inside compaction without any soil disturbance, suited particularly for sensitive samples with high-water contents. The efficiency of natural and synthetic fibres on improving tensile-strain characteristics of compacted-reinforced clay were first evaluated by varying fibre length and content. Pull-out tests were carried out on the different types of fibres, then SEM and EDS analysis were used to identify the interaction nature of the fibre and the soil matrix. The effect of initial water content and dry density was then investigated. The results indicated that, for some range of initial water content and dry density, short fibres can significantly improve tensile-strain characteristics of the reinforced soil by delaying crack initiation and reducing its propagation velocity. Moreover, longer natural fibres were found more effective than synthetic ones in restraining tensile cracks. Various fibre avoidance mode of crack growth were analysed and associated mechanisms were discussed.