NUMERICAL AND EXPERIMENTAL INVESTIGATION OF LOOSE SAND-SCRAP TIRES MIXTURE STIFFNESS

Abstract

Rubber-sand mixtures have many applications in geotechnical engineering. Considerable
literature exists on the mechanical behavior of dense sand shredded rubber mixtures, but up to the author’s
knowledge, there are no such studies on sand-filled used whole car tires. The latter is ubiquitously used in
developing countries to create cheap and quick backfill. The paper presents results from three-dimensional
finite element models and plate load tests on layers of loose sand and whole tire mixtures in a steel tank. The
finite elements program ANSYS is used to compare between a true 3D realization of the tire shape and a
homogenized representation of the mixture. Numerical and laboratory results show how interpreted stiffness
values depart from literature and physical laws of mixing soft and stiff components because the whole tire is
used instead of shredded chips. The paper applies the equivalent thickness method to interpret the plate load
test results and compute mixture stiffness for different thicknesses and shows good agreement with numerical
back analysis. The application of plate load tests in the field and using the proposed approximate method is
recommended to assess mixture stiffness rather than using assumed values from the literature. The paper
presents an empirical correlation between the normalized layer thickness and the mixture stiffness for firstorder predictions.