Behaviour of a square model footing on loose sand reinforced with braided coir rope

The effectiveness of horizontally placed braided coir rope reinforcement on the strength improvement and settlement reduction of loose sand is investigated for modeling footings using plate load tests in the laboratory. The influence of parameters such as depth of reinforcement embedment, length, number of layers and number of plies of braided coir rope was examined. The model test results indicate that up to about a six-fold improvement in strength and about ninety percent reduction in settlement (vertical displacement) can be achieved through the use of the proposed reinforcing method. The optimum value of embedment depth of a single layer of braided coir rope reinforcement was identified as 0.4 times the footing width. It was also found that optimal benefit was realized for a length ratio equal to about 3 and by reinforcing the zone of soil directly beneath the model footing upto a depth equal to about 0.6 times the width of footing. Increase in the number of layers within the significant depth leads to a proportionate increase in strength improvement ratio, while the optimal settlement reduction is realized with three layers of braided coir rope reinforcement. Regression analysis carried out with limited experimental data suggests the possibility of developing a predictive model to quantify the strength improvement.