Novel Natural Fibre-Based Composite-Structured Geotextiles for Protection of River-Bank – A Case Study

Bank erosion causes inconceivable damage to the human habitation and property every year. Looking into the perennial problem and non-availability of indigenously produced geotextiles for specific use, a set of novel geotextile fabrics using jute and jute-coconut fibre blended yarn separately (in cross direction) and polyolefin tape yarn (in machine direction) has been developed. Some composite structured/layered-structured geotextiles have also been developed. The fabric samples contain more than 70% (wt/wt) natural fibre. The production viability of the developed geotextiles has been tested through continuous production of the geotextile fabrics using commercial-scale machines at NIRJAFT laboratory. The performance of the fabric samples were evaluated following ASTM standard test methods. The composite structured geotextiles having much balanced property parameters are durable, more effective than both 100% natural and 100% synthetic fabrics and much cheaper than 100% imported synthetic geotextile fabrics. In addition, the developed geotextiles offers excellent drapability and anti-slip property. At the same time it helps to maintain the flora and fauna of the soil, which is not achieved when 100% synthetic geotextiles are used. A successful field trial was conducted for protection of a part of the bank of Mayurakshi River (rain-fed river) at West Bengal using the developed geotextiles based on the principle of using geotextiles as reinforcing material for stable grass-turfing. The vertical height and angle of gradient of the bank were approximately 9.0 m and 60° respectively. All the materials used for execution of laying-work of geotextiles were procured from adjacent locality. The work-force was also appointed from the nearby villages. A total shower (till laying of geotextiles) during monsoon was recorded as nearly 140 cm and then at the end of full monsoon period, even after release of stored water from Massanjore dam through Tilpara barrage @ 1,25,000 cusec (plus additional 35,000 cusec from local catchments due to a spell of spear-headed shower for continuously three days during the same period), no change (deformation), and zero erosion of the part of the river-bank under trial was observed. Vegetation had been established. While, on the rest of the part (where geotextile was not been used), signs of major soil erosion including rain-cuts (Number of rain-cut – 64/100 m length of river-bank) were clearly visible. In case of all-PP geotextiles, patchy grass vegetation, slipped/washed-out soil cover and torn-off places due to cow hooves were observed.