Utilization of coir dust to partially replace sand in vertical drains for soft ground improvement.

Abstract

As a developing country, Sri Lanka has already launched major development projects such as highways, new airport projects, harbour expansion projects and other larger construction projects, therein utilizing undesirable grounds is unavoidable due to limited usable land. Normal practices like removing and replacing of soil as well as pile foundation in overcoming undesirable conditions of the soft ground may not be economically and environmentally feasible for a developing country like Sri Lanka. At the same time, solid waste management has become a major concern all over the world as it appears with many issues. Waste reduction, reuse and recycle have become major issues in recent days. As a major coconut producing country in the world, Sri Lanka produces annual net waste of coir dust around 527,800 tons. Having considered the means of reducing and reusing the coir waste in a useful manner, the applicability of ground improvement with an introduction of coir dust in the vertical drains as a filling material with sea sand was studied in this research. Permeability characteristics of mixed materials of coir dust and sea sand and sea sand alone were analyzed and consolidation behaviour of high plasticity clay with vertical drains under three conditions, vertical drain filled with sea sand alone and the drain filled with mixed materials as well as without vertical drains were discussed. The results of consolidation tests showed that the soil improved with vertical drains consist of coif dust accelerate the consolidation process compared to the unimproved soil. It was observed that the coefficients of permeability of mixed samples were within the range of 10·2 (cm/s), which is a typical value for sand drains. The optimum percentage of coir dust to be used in vertical drains was figured out as the final result by considering permeability and consolidation characteristics as well as the cost analysis for practical applications.