Interface shear behaviour of coir geotextiles and sand using large-scale direct shear tests

Dharmesh Lal, N. Sankar and S. Chandrakaran


The practice of soil reinforcement using natural products is attaining widespread acquiescence in developing countries due to its availability, cost effectiveness and also due to its ability in effectively replacing synthetic reinforcing elements. Coir is an eco-friendly, biodegradable, organic material which has high tearing strength, stiffness, and durability compared to other natural reinforcement materials. Frictional characteristics of geotextiles were analyzed through large-scale direct shear tests to knock out boundary effects and to reproduce the results in prototype scale. Detailed parametric study was conducted by varying the particle size, normal stress and type of geotextile. The improvement due to the provision of coir geotextiles is expressed in terms of a non-dimensional parameter called friction angle efficiency. The results indicate that coir geotextile inclusions enhance the peak shear strength, angle of internal friction and ductility of sand. Also, geotextiles with small mesh openings and higher tensile strength provide better performance in terms of increasing the shear strength of sand.