Experimental and numerical analysis on shear behavior of coir geotextile reinforced granular subbase-subgrade system

This paper presents the results of an investigation aimed at studying the shear force–displacement behavior of coir geotextile reinforced granular subbase-subgrade systems using a large-scale direct shear apparatus. Three different soil types and two types of woven coir geotextiles are employed to assess the shear strength of the coir geotextile reinforced composite system. The motivation behind this research lies in the increasing need for sustainable and effective ground improvement techniques in geotechnical engineering. The objective of this study is to enhance our understanding of these systems by investigating the shear behavior under varying soil conditions and coir geotextile densities. Through this analysis, we aim to elucidate the interface shear parameters and overall performance of the system, ultimately contributing to the development of more effective ground improvement methodologies. Strength increase, shear and volumetric deformation of reinforced soil, and interface friction coefficient were studied under direct shear conditions. The experimental results demonstrate that coir geotextile reinforcement at the interface significantly improves the shear parameters. A shear strength improvement factor of 1.14–1.37 is achieved using the denser 700 gsm geotextile for various subgrade soils, while a factor of 1.02–1.27 is noted with the lesser 400 gsm density. The findings can be applied in the design of pavement systems where coir geotextiles reinforce the subgrade, improving load distribution and enhancing roadway longevity, particularly in weak or expansive soils. The validity of the Finite Element Method (FEM) calculations was verified, and it was concluded that the results from the FEM analysis align well with the experimental data, affirming the efficacy of the proposed methodologies in geotechnical applications.