Effect of Coir Fiber on the Stress–Strain Behavior of a Reconstituted Fine-Grained Soil

Abstract

The heterogeneous nature of the soil poses great challenge as well as opportunity to geotechnical engineers all over the world. As the availability of good sites is becoming difficult, active research is going on throughout the world to improve the engineering properties of the soft soils. Among all the ground improvement techniques, the soil reinforcement is emerging as an attractive alternative. Addition of natural fiber to the soil is a very good soil-reinforcement technique in the context of sustainable development. Coir fiber can be effectively used to tackle many short-term stability issues in geotechnical engineering related to shear strength, permeability, etc. In the present study, comprehensive experimental work has been conducted to investigate the effect of coir fiber on the stress–strain characteristics of a reconstituted cohesive soil. Laboratory model studies are conducted to study the effect of length and amount of fiber on the shear strength of soil. Tests were carried out using fiber contents varying in the range of 0%–2% by dry weight of the soil. The unconfined compressive strength of soil is significantly increased when coir fiber is added to it. The increase is directly proportional to the quantity of the fiber used. The peak compressive strength of the fiber-reinforced soil with 1.5% fiber content is more than twice that of the un-reinforced soil. Mixing of fiber of length 15 mm is found beneficial from laboratory experiments on 38-mm (diameter) × 76-mm (height) samples. Triaxial compression tests results showed that the fiber content in the range of 1.5%–2% is highly beneficial to enhance and strength of the fine-grained soil. Also, it is observed that peak deviator stress increases with increase in fiber content for all confining pressures. A remarkable increase in cohesion and friction angle values has been observed with the addition of fiber, and they increases nonlinearly with the fiber content. Moreover, the stiffness and ductility of the soil are quite improved with the use of natural fiber.

Keywords:

• coir fiber
• kaolin
• stress-strain behavior
• fiber dosage
• fiber length

ACKNOWLEDGMENTS

The work reported in this paper is supported by the Indian Institute of Technology Bombay through Seed Grant Project No. 07IR036. The authors would like to thank IIT Bombay authorities for their support.