Behavior of Reinforced-Stone Dust Walls with Backfill at Varying Relative Densities

The metal-aggregate industry is a dominating and unorganized industrial sector in India. The production of this aggregate is enormous to meet the ever-increasing demands of the construction industry. During crushing of stone aggregates in quarries, waste is generated, which is termed stone dust or quarry waste. The proper utilization or environment-friendly disposal of this stone dust is of concern. This paper presents the results of model walls with reinforced-stone dust as backfill, tested under strip loading with backfill compacted at varying relative densities of 17, 38, 59, and 73%. The model-wall facing was comprised of segmental blocks of concrete, and backfill was reinforced with bamboo-grid strips with a length-of-reinforcement-to-height-of-wall ratio ($L/H$) as 0.2, 0.3, 0.4, 0.5, and 0.6. The consequence of reduced-relative density of backfill (stone dust) on the facia displacement, settlement of backfill, and failure surcharge was studied. The results show that unreinforced-stone dust model walls collapse without much resistance when tested at a backfill relative density of 59% and lower. Stone dust is found to be a very effective material as a reinforced backfill and gives considerably good results with respect to facia displacement, failure surcharge pressure, and backfill settlement for a relative density at 59 and 73% with a minimum length of reinforcement $L/H$ as 0.5. The model walls constructed with a relative density at 38 and 17% display higher facia displacements and fail at low-surcharge values compared with the walls constructed with a relative density of backfill at 59 and 73%. This study helps in understanding the response of reinforced-stone dust walls corresponding to the range of relative densities used in experimental work and also helps to bring about an optimum effect without much wastage of material. With a view to further improving the performance of these model walls, expanded polystyrene geofoam blocks were placed behind each facia unit, and the wall behavior and performance was checked for geofoam densities of 0.12, 0.15, and $0.20\mathrm{kN}/{\mathrm{m}}^3$ with thickness variation as 5, 15, and 20 mm. Geofoam inclusion improves the overall behavior in terms of reduced-facia displacements, backfill settlements, and increased values of failure surcharges.