To study the effect of crumb sizes of worn tires in shear strength parameters of Sandy soil

Due to spread of automotive industry the worn tires are being consider as a one of the Environmental pollutants in recent decades because of the lack of decomposition in nature. The use of tires crumb with mixed soil is provided as a one of the solutions to prevent environmental hazards caused by tires burial. According to the tires properties, such as elastic behavior, low water absorption and the appropriate cost to use it in the form of crushed, they can be used in arming and improving the properties of earth materials. In this article, the optimal percentage of tires crumb in the sand to increase its shear strength parameters as well as the effects of adding tires crumb on Displacement-load curve by using large-scale direct shear test (box 30x30 cm) has been studied. For this purpose, sand with different percentages of tires crumb and various value of normal stresses in direct shear has been tested and the percentage of optimal tires crumb which the shear strength is maximum for it determined. Since the shear strength of soils is because of angle of internal friction and viscosity, the effect of tires crumb on each of these parameters is studied. Results shows that adding tires crumb cause to increase the capacity of plasticity, viscosity, angle of internal friction and therefore to increase the shear strength of the sand.