Interface Shear Stress Properties of Geogrids with Mixtures of Fly Ash and Granulated Rubber

In recent times, alternative ways to dispose various wastes generated, namely, fly ash, scrap tires, steel or iron slag, and foundry sand, are on the rise. Owing to low unit weight and good hydraulic conductivity properties of waste tires, they are found to be a competent alternative fill material for geotechnical applications. Likewise, fly ash is an accepted foundation as well as a backfill material. In the present study, reinforcing composite material made up of fly ash and granulated waste rubber of a nominal size equal to 9.5 mm is explored for use as a reinforced fill material or as a foundation bed material. Accordingly, the interface shear stress properties of a geosynthetic reinforcement with this new composite fill material are obtained using an interface shear box of dimensions equal to $305\times 305\times 204\mathrm{mm}$ ($\mathrm{length}\times \mathrm{width}\times \mathrm{depth}$). Two different types of geogrids, uniaxial and biaxial geogrids made up of polyester and polypropylene, are used as a reinforcing material. The granulated rubber contents in the mixtures are varied as 0%, 9%, 23%, 37%, 50%, and 100% to study its effect on the interfacial shear strength of geogrid and mixture. In addition, the effects of the type of the geogrid, tensile strength of the geogrid, and area of aperture opening within the grid are studied for a given mix of fly ash and granulated rubber ($50:50$ by total weight of the mixture). The effects of the type of geogrid and tensile strength of the geogrid on the interfacial shear strength are found to be insignificant, while a geogrid with a higher aperture opening area ratio is found to exhibit a high interfacial shear strength. The interaction coefficients of uniaxial and biaxial geogrids with fly ash and granulated rubber mixtures are found to range from 0.74 to 1.16 and 0.74 to 1.18, respectively.