Laboratory Evaluation of Permeability Characteristics of Cocologs

Cocologs, which are made out of coir fibers, have proven to be an erosion control product along river banks. Cocologs are densely packed coconut fibers wrapped in coir net. This paper presents the laboratory experimental results on the permeability characteristics of cocologs. The permeability of cocologs is a critical parameter in the design of cocolog-stabilized geostructures. In this study, the experiments to determine the permeability of cocologs were carried out in a modified permeability test apparatus using clear water as the permeating medium. The effect of different parameters such as the density of cocolog, opening size (d) of outer cover and orientation of cocologs on the permeability of cocolog was investigated. It was found that the permeability of cocologs increases from 20 mm/s to 85 mm/s when density decreases from 220 kg/m3 to 100 kg/m3. The opening size of the outer net covering of cocologs should not be reduced below a d/L (opening size to the length of cocologs) ratio of 0.0075. It is concluded that the density of cocolog is the only governing parameter which has a significant influence on the permeability of cocologs. Furthermore, an empirical relationship was developed to determine the permeability of cocologs considering the effect of different parameters.