Static and dynamic behavior of sand-rubber chips mixtures

Editor’s Foreword
During the last decades, chipped and shredded scrap tires mixed with soil have
found a wide range of innovative civil engineering applications including the
use as highway embankment fill, retaining walls and bridge abutment backfill,
for liquefaction mitigation, for seismic isolation of building foundations, as
barrier for vibration protection, or to reduce swelling of expansive clays.
Several studies have addressed the behaviour of the composite material with
respect to compressibility, shear strength, or liquefaction susceptibility. The
degree of improvement depends on the size and shape of the rubber particles
as well as the gradation of the rubber and the sand. Most investigations
hitherto dealt with rubber granulate or small-size chips.
The present experimental work focuses on the behaviour of large, irregularly
shaped rubber chips mixed with different sands. Extensive static, cyclic and
dynamic laboratory tests have been carried out in order to enhance our
understanding about the complex interactions between the two constituents,
capture the pertinent properties of the composite material at various rubber
contents, and identify the optimal mixing ratio in dependence of the loading
pattern. The behaviour of pure sand, inferred from the respective laboratory
tests, serves as a benchmark for the quality of the tests and point of reference
for the assessment of the mechanical properties of the sand-rubber mixtures.
Of great interest are the findings for cyclic drained or undrained loading. The
equations for shear modulus and damping derived from the wide range
resonant column tests can directly be used in design.
The dissertation provides a valuable insight into the behaviour of this
particular type of composite granular medium, and can be used as a starting
point for the investigation of mixtures with other rubber chips geometries and
soils types, aiming at optimizing the application in geotechnics.
Christos Vrettos