Laboratory Investigation in the Improvement of Subgrade Characteristics of Expansive Soil Stabilised with Coir Waste

Soft soils form problematic subgrade for pavements due to its low bearing capacity and strength. Pavement loads coming on the soft subgrade soil may cause detrimental pumping actions when they are located in areas with high water table which causes both construction and in-service performance problems. The common solutions on encountering such problems include excavation and replacement of soil, lime treatment or chemical stabilization. Excavation and replacement of soil becomes very expensive especially when usable soils have to be hauled to significant distance. Stabilization using various additives can improve the properties of soft soils. A recent trend in stabilization is to utilize locally available industrial wastes to improve the properties of soft soils. This method has the dual advantage of increasing the strength of soil and a solution for the problematic disposal of such wastes. Coir waste consisting of coir pith and coir fibre is a by-product of coir manufacturing industry obtained from coconut husk during the extraction of coir fibre. The pollution caused due to the polyphenol leaching and the resistance to degradation due to the stable lignin structure makes the coir waste a potential threat to the land resources. This paper presents an investigation on the behavior of soft soil stabilized with varying percentages of coir pith (0-3%) and coir fibre (0-1%) by carrying out Standard Proctor, Static Triaxial test and California Bearing Ratio(CBR) tests. The test results showed that stabilization with coir waste had a significant effect on the compaction, Elastic modulus as well as CBR characteristics.