Studies on Effect of Different Environmental Conditions on CBR of Black Cotton Soil Reinforced with Coir Fibre

Expansive soil covers nearly 20 percent of the land mass in India. These soils are known to possess weak properties due to the presence of clay minerals known as “Montmorillonite�. Typical behaviour of soil results in the failure of structures, in form of settlements, cracks etc. Thus it is important to remove the existing weak soil and replace it with non expansive soil or to improve the properties of weak soil by stabilization. Soil reinforcement is a technique that can be used to improve the engineering characteristics of expansive soils. Use of natural fibres to reinforce soil is an old and ancient idea. Randomly distributed fibre reinforced soil have recently attracted growing attention in geotechnical engineering. The present dissertation aims to study the effect of different environmental conditions on performance of coir fibres included in black cotton soil to enhance its strength and reduce the swelling behaviour. Coir fibre is known as a biodegradable material that tends to decay under extreme environmental conditions such as in contaminated and polluted water, in getting contact with the leachate, in alternate cycles of wetting and drying, also in alternate cycles of freezing and thawing and so on. In general, life of coir fibre in soil is expected to 8-10 years. Therefore under different environmental condition it may degrade fast. The gain in soil strength or decrease in swelling might be lost. This aspect is not studied so far. Hence in this work this is attempted. The work in the project is experiment based, California bearing ratio of soil is an important soil strength parameter used in design of pavements. Effect of some different possible environmental conditions on CBR of expansive soil improved by coir fibre reinforcement will be studied experimentally in the present work.