Desiccation Characteristics and Desiccation-Induced Compressive Strength of Natural Fibre-Reinforced Soil

In this study, desiccation characteristics of natural fibre-reinforced soil were investigated. The soil was mixed with sisal fibres (25 mm) at the fibre content of 0.5% and 1%. The effects of soil thickness on the desiccation characteristics were investigated using specimens with thickness of 6, 12 and 24 mm. Digital image analysis was used to study variation of crack morphology, width, surface crack area ratio, crack growth rate and shrinkage strain of the desiccated soil. The gravimetric measurements of moisture content were used to investigate rate of moisture loss and evolution of cracks with change in moisture. The effects of saturation and desaturation on the compressive strength of the soil were investigated by subjecting the compacted soil to wet and dry cycles. The results showed that crack morphology of the reinforced soil was characterised by small cell areas of irregular shapes, short and thin cracks and non-orthogonal crack intersections. Specimens with fibre content of 0.5% showed lower rate of moisture loss than unreinforced soil. This was attributed to the reduction of free moisture caused by fibre moisture absorption. Specimens with fibre content of 1% indicated higher rate of moisture loss than unreinforced soil due to an increase in the volume of water pathways. Crack width and surface crack area ratio showed reduction of 74% and 35%, respectively, with 1% fibre content. The crack growth rate and shrinkage strain significantly reduced with fibre inclusion. Increase in the soil thickness caused an increase in crack width and evaporation for both reinforced and unreinforced soil. Increasing number of wet and dry cycles up to 15 caused compressive strength degradation of 41% and 66% for compacted reinforced and unreinforced soil, respectively. Natural fibre inclusion can effectively be applied to control desiccation cracking of the soil which is beneficial in maintaining integrity of soil for various civil engineering applications.