Resonant Column Tests on Mixtures of Different Sands with Coarse Tyre Rubber Chips

Abstract

The dynamic behaviour of unsaturated sand rubber chips mixtures at various gravimetric contents is evaluated through an experimental study comprising resonant column tests in a fixed-free device. Chips were irregularly shaped with dimensions ranging from 5 to 14 mm. Three types of sand with different gradation have been considered. Relative density amounted to 0.5 for all specimens. Due to the large size of the chips, the diameter of the specimens had to be equal to 100 mm, which in turn required a re-calibration of the device assuming a frequency-dependent drive head inertia. The effects of confining stress, rubber chips content, and sand gradation on shear modulus and damping ratio are determined over wide ranges of the shear strain. At small strains, as known for sands, increasing the confining stress stiffens the mixtures. Increasing the rubber chips content reduces significantly the shear modulus and increases the damping ratio. At higher strains, increasing the confining stress or the rubber content flattens the reduction of the shear modulus with strain. Damping at high strains does not show any appreciable dependence on rubber content. Unloading–reloading sequences are used to assess shear modulus degradation and threshold strains. Finally, design equations are derived from the test results to predict the dynamic response of the composite material.

Configuration of a gravel-rubber geotechnical seismic isolation system from laboratory and field tests

“…Based on a series of resonant column tests, they 78 showed that the small strain dynamic stiffness (G 𝑜 ) de-79 creases and the initial damping (D 𝑜 ) rises with increas-80 ing rubber content due to the increased number of con-81 tacts between the rubber particles. Similar results were re-82 ported by Banzibaganye and Vrettos (2022) Anastasiadis and proposed strain-dependent 90 shear modulus degradation and damping ratio curves derived 91 from cyclic triaxial and resonant column tests over a wide 92 range of strain amplitudes of SRM and GRM specimens of 93 a wide range of rubber content per mixture weight. Granulated rubber or tire chips have been studied numer-95 ically or experimentally as a lightweight backfill material of 96 retaining walls (Youwai and Bergado, 2004;Hazarika, Ko-97 hama and Sugano, 2008;Tsinaris, Anastasiadis and Pitilakis, 98 2018) and bridge abutments (Argyroudis, Palaiochorinou, 99 Mitoulis and Pitilakis, 2016) or as a drainage layer (Edil 100 and Bosscher, 1994).…”