The strength law of coir fiber-reinforced soil based on modified Duncan-Chang model

A large diameter triaxial sample of 61.9 mm was made by adding coir fiber into red clay. The range of confining pressure was 50-200 kPa; fiber content was 0.1%-0.4%; and fiber length was 10-40 mm. By varying the confining pressure, fiber content and fiber length, the unconsolidated and undrained triaxial tests were used to study the shear strength variation law of coir fiber-reinforced soil. The experimental data were processed to establish a linear model of the segmental elastic modulus, and linear analysis was used to determine the model fitting parameters and to improve the Duncan-Chang model by combining the concept of damage ratio. The modified Duncan-Chang model fits the stress-strain relationship of coir-reinforced soil. The results show a clear dividing line for the effect of fiber length and fiber content on the strength of the samples, which is about 30 mm and 0.3%, respectively. At the same time, the modified model can fit the stress-strain relationship of coir fiber-reinforced soil and reflect the stress-strain curve characteristics of coir fiber-reinforced soil.