Mechanics of Fiber Reinforcement in Sand

TLDR

Direct shear tests on dry sand reinforced with natural, synthetic fibers and metal wires were compared to a force‑equilibrium model of fiber‑reinforced sand. Fiber reinforcement raised peak shear strength and limited post‑peak reductions, with the model accurately predicting strength gains proportional to fiber concentration, optimal at 60° orientation, and similar effects in loose and dense sands, informing slope, dune, and root‑reinforced soil stability.

Abstract

Direct shear tests were run on a dry sand reinforced with different types of fibers. Both natural and synthetic fibers plus metal wires were tested. Experimental behavior was compared with theoretical predictions based on a force equilibrium model of a fiber reinforced sand. Test results showed that fiber reinforcement increased the peak shear strength and limited post peak reductions in shear resistance. The fiber reinforcement model correctly predicted the influence of various sand‐fiber parameters through shear strength increases that were: (1) Directly proportional to concentration or area ratio of fibers; (2) greatest for initial fiber orientations of 60° with respect to the shear surface; and (3) approximately the same for a reinforced sand tested in a loose and dense state, respectively. The findings of this study are relevant to such diverse problems as the contribution of roof reinforcement to the stability of sandy, coarse textured soils in granitic slopes, dune and beach stabilization by pioneer plants, tillage in root permeated soils, and soil stabilization with low modulus, woven fabrics.