R Poursalimi - 1. M.Sc Student in Geotechnics, School of Civil Engineering, The University of Guilan
N Jamshidi Chenari - Assistant Professor, School of Civil Engineering, The University of Guilan

Lightweight materials are commonly used for backfilling retaining structures so as to reduce the inertia force induced by seismic events. They also cause to decrease induced structural damages by suffering greater deformations showing larger damping. In this paper, shear modulus and damping parameters of sandy soils mixed with tire crumbs (as a commonly used light weight material) are evaluated using large scale cyclic direct shear apparatus. For this aim, a cyclic large scale direct shear apparatus was fabricated and designed to perform experiments. Repeatability of test results was first checked and compared with a standard small scale direct shear device. In this regard, rubber powders are mixed with loose sand in different fractions (0, 5% and 10%) and variations in their shear strength parameters are evaluated. Stiffness degradation and hysteretic behavior of the materials are evaluated and discussed accordingly. Based on the tests, it was observed that increasing the powder content will result in a decrease in the damping ration of the mixture by showing enlarged hysteresis loops in comparison to plain model. Moreover, shear modulus of the mixture is shown to decrease with the tire crumbs inclusion by producing flatter loops when tested in cyclic direct shear apparatus.

Tire crumbs ، cyclic direct shear ، Shear modulus ، Damping ratio ،