Experimental investigations on tensile and pullout behaviour of woven coir geotextiles

Results of an experimental programme to investigate the tensile and interface properties of woven coir geotextiles are presented. Tension tests were conducted on coir fibres, yarns and woven geotextiles at different gauge lengths and strain rates. Based on statistical analysis, a gauge length of 150 mm and a strain rate of 5%/min was adopted for the purpose of characterization of tensile properties. Tensile strength of woven coir geotextile was expressed as a function of fibre strength, yarn properties and weaving pattern. Pullout test and modified direct shear test were conducted on geotextiles in granular soils of different grain sizes. At low normal stress, bond resistance of coir geotextile–sand interface obtained was more than shear strength of soil. But consistent values of bond resistance were not obtained at higher normal stresses. The opening size of mesh relative to the soil grain size influenced the pullout interaction between soil and geotextile. For closely woven geotextiles, the pullout resistance did not vary much in soils of different grain sizes, whereas for geotextiles with open meshes, pullout resistance obtained was more in fine sand compared to coarse sand.