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Shear Strength Behaviors of Tire Shred-Dune Sand Admixtures
Elmootassem, Ruba A.
Elmootassem, Ruba A.
Description
A Master of Science thesis in Civil Engineering by Ruba A. Elmootassem entitled, “Shear Strength Behaviors of Tire Shred-Dune Sand Admixtures”, submitted in January 2024. Thesis advisor is Dr. Magdi El-Emam. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).
Abstract
The use of discarded tires in civil engineering applications has been shown to be an effective tire waste management technique. Scrap tires also act as a soil stabilizer capable of improving shear strength parameters, bearing capacity, and overall stability of soil. While dune sand is abundantly available naturally in the UAE, its potential for use in geotechnical engineering applications is often underutilized because of its poor engineering properties. Mechanical stabilization of sand with the inclusion of tire shreds has been shown to improve its shear strength properties for use as backfill material. While studies have evaluated the effects of tire shred content and size using large-scale direct shear (LSDS) tests, the available literature provides inconsistent results in terms of optimum scrap tire content and size for maximum shear strength improvement. The objective of this research is to assess the suitability of using tire shred-dune sand admixtures as backfill material by evaluating the shear strength behaviour of the soil matrices at different tire shred/dune sand ratios and tire shred sizes. This isolates the optimum tire shred-dune sand mixing ratio and suitable tire shred length for use as backfill. The major soil parameters investigated were admixture shear strength, friction angle, and stiffness. A large-scale direct shear (LSDS) apparatus was designed and manufactured for use at AUS geotechnical engineering lab. The apparatus was used to test 45 tire shred-dune-sand samples, with tire shred contents of 0, 5, 10, 15, and 20% by weight, and tire shred lengths of 30-50mm, 50-70mm, and 70-100mm. The results showed that the inclusion of tire shreds in dune sand can increase peak shear strength by up to 77% as compared to pure dune sand. The optimum tire shred size was concluded to be 50-70mm as it produced the highest peak and residual shear strength and friction angles. TS contents between 15 and 20% consistently produced the highest shear strength parameters, with a peak friction angle of 39.5o achieved at optimum conditions. The highest residual friction angle of 40.8o was achieved at TS content of 10%. The results also showed that increasing TS content and length decreases stiffness for most tested samples. These findings provide major insight into the feasibility of using tire shreds as a dune sand stabilizer, specifically in the UAE, and can be used to further develop sustainable engineering practices in the region.