Design, Manufacturing and Application of Natural-Synthetic Composite Geotextiles for Protection of River-Bank

Abstract

Bank erosion has become a serious problem in many rivers. Generally occurring in the monsoon season, when the rivers are in spate, bank erosion causes inconceivable damage to the human habitation and property. Looking into the perennial problem and non-availability of indigenously produced geotextiles for specific use, a set of novel geo textile fabrics using jute and jute-coconut fibre blended yarn separately (in cross direction) and polyolefin tape yam (in machine direction) has 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 blended fabrics 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. A successful field trial was conducted for protection of a part of the bank of Mayurakshi River (rained 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 under NREGS. 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 spearheaded 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. 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.