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Direct shear behavior of gravel-granulated tyre rubber mixtures
| Content Provider | Semantic Scholar |
|---|---|
| Author | Chiaro, Gabriele Palermo, Alessandro Banasiak, Lukasz Granello, Gabriele |
| Copyright Year | 2019 |
| Abstract | The objective of the work presented in this paper is to investigate the direct shear strength of gravel and granulated tyre rubber (GTR) mixtures for possible use as seismic-isolation foundation systems for low-rise buildings. Specimens of gravel, GTR, and selected mixtures (10%, 20%, 30% and 50% GTR % by mass) were tested in the direct shear apparatus under three normal stress levels of 25, 50 and 60 kPa. The addition of GTR significantly influenced the shear strength and volumetric response of the mixtures. In particular, it is observed that the mechanical behaviour of the mixtures progressively changed from gravel-like (i.e. strain-softening/dilative) to rubber-like (i.e. strain-hardening/contractive), the transition occurring for GTR content between 20% and 35%. Importantly, although a progressive decay of the peak shear strength with GTR content is observed, the friction angle at failure is found to be equal to or greater than 39 for all mixtures. A uniformly-graded grey pea gravel (D50 = 6 mm) and shredded tyres in the form of GTR (D50 = 0.9 mm) have been employed. The GTR is composed of waste tyres that had been mechanically shredded using multiple shredding steps and sieved to be of approximately uniform size. The tests were carried out on gravel-GTR mixtures with different gravimetric percentages of GTR (0%, 10%, 20%, 30%, 50% and 100%) the gravimetric percentage of GTR is defined as the ratio of the mass of GTR to the total mass of gravel and GTR. The particle size distribution curves of the pea gravel, GRT and selected mixtures are shown in Figure 1. The gravel has rounded-shape grains (Fig. 2a) and its specific gravity was measured as 2.66. The GTR (shredded tyres currently commercially available in New Zealand) are shown in Figure 2b. The specific gravity of GTR was measured as 1.15. This is within the range of the specific gravities of scrap tyres (1.02 to 1.30) reported by different investigators (e.g., Edil & Bosscher 1994, Foose et al. 1996, Ghazavi & Sakhi 2005, Mashiri et al. 2015). Figure 1. Particle size distribution curves for tested materials. Figure 2. (a) Pea gravel; and (b) GTR used in this study. The gravel and GTR specimens were prepared by thoroughly mixing and placing three equal-mass layers of gravel and GTR in the shear box. Each layer of gravel-GTR mixture was compacted in the shear box to achieve the required gravel matrix unit weight. Particular care was required while preparing the specimens to avoid any possible segregation between gravel and rubber. As summarised in Table 1, a total of 18 tests were carried out on dry specimens subjected to three normal stress levels of 25, 50 and 60 kPa. The specimens were sheared at a constant horizontal displacement rate of 1 mm/min. For completeness, the dry density measured just before the shearing process (i.e. after the application of the normal stress) is also reported in Table 1, along with the corresponding void ratio and the specific gravity of each mixture. Table 1. Direct shear tests carried out in this study and specific gravity of tested materials Test GTR (%) Specific gravity Normal stress (kPa) Dry density* (kg/m) Void ratio* |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://ir.canterbury.ac.nz/bitstream/handle/10092/16860/Chiaro%20G-ANZ2019-Final.pdf?isAllowed=y&sequence=2 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
