Investigating the static and cyclic undrained behavior of the tire-sand mixture

In recent years, the mixture of sand and rubber particles has been used in various fields of civil engineering, such as the stability of roofs, retaining walls, and drainage materials in landfills, due to its durability, cost-effectiveness and solving environmental problems. The purpose of this study is to investigate the effect of tire crumb on the shear strength and dilation in a static state and the liquefaction resistance in a dynamic state. In this regard, in this research, a static and dynamic undrained triaxial test was performed on a mixture of Babolsar sand and tire crumb (size between 1 and 8 mm) under constant confining pressure. The effect of parameters such as the amount of different tire crumbs (0, 5, 10, 20 and 30% by weight) and different relative densities on the static and dynamic behavior of the mixture of sand and rubber crumb and the created pore water pressure was investigated. In the static (consolidated-undrained) triaxial test, the relative densities of the sand–tire mixtures were 45, 60 and 80 percent. The tests were carried out on the specimens at 100 kPa cell pressure. Also, the specimen was loaded under a strain rate of 0.30% per minute, for all the tests until the axial strain reached 20%. In cyclic triaxial tests, the relative density of the sand–tire mixtures was 45 percent and the confining pressure of 100 kPa was used in the experiments. The sinusoidal waveform was applied to the specimen with a frequency of 0.5 Hz. To accuracy evaluation, the behavior of the sand-tire mixture, corrections such as membrane penetration corrections, membrane force and cross-sectional area were applied. The results showed that adding tire crumb to sand reduces the shear strength and dilation of sand. Also, the ratio of the mean diameter of tire particles to the mean diameter of sand particles affects the behavior of shear resistance and dilation of the sand-tire mixture. As the ratio of the mean diameter of tire particles to the mean diameter of sand particles increases, the shear strength and dilation of the sand-tire mixture increases. Also, increasing the amount of tire crumb in sand reduces the excess pore water pressure and as a result reduces liquefaction potential in cyclic loading. This behavior can be attributed to the compressible nature due to the low elastic modulus of the tire crumb.