Interface Behavior of Granular Soils Reinforced with Surface-Modified Coir Geotextiles

Abstract

The paper presents the effect of using cashew nut shell liquid (CNSL), a low-priced agro by-product and a renewable resource, to treat coir geotextiles. Large-scale direct shear tests were performed on sands reinforced with untreated and treated coir geotextiles at different normal stresses (50 kPa, 100 kPa, and 150 kPa). Sands of three different particle sizes (coarse, medium, and fine) were used for the study. The shear strength parameters of reinforced soil samples were measured in terms of interface friction angle, apparent cohesion, and interface coefficient. The experimental investigations revealed that cashew nut shell liquid-treated coir geotextiles improved the interface shear strength parameters for all sand fractions. The tensile strength of CNSL-treated coir geotextile was also improved by 13%. Two-dimensional finite element simulations of large-scale direct shear tests using PLAXIS 2D were also carried out to study the mechanism in detail. Mohr’s circles were drawn using the data from numerical analyses, and the plane strain friction angles obtained were compared with the direct shear friction angles obtained from experimental studies. The plane strain friction angle was higher for soil reinforced with treated coir geotextile than soil reinforced with untreated coir geotextile, indicating the shifting of the failure envelope.

Keywords

• sand
• coir geotextile
• cashew nut shell liquid
• interface
• friction angle
• mohr circle