3275
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
1
Road foundation construction using lightweight tyre bales
Construction des assises de routes à l'aide de balles de pneus légères
M.G. Winter
Transport Research Laboratory (TRL), Edinburgh, United Kingdom
ABSTRACT: Road construction over soft ground presents considerable technical challenges. Such roads often serve remote
communities and carry low levels of traffic; construction and maintenance must be achieved within very limited budgets. There are
two main approaches to such construction: above ground (floating) and below ground (buried) construction. Floating construction is
generally used where a relatively stiff material, such as fibrous peat, overlies a less competent material, such as amorphous peat.
Buried construction is generally used in more competent materials, or in soft materials of shallower depth such that removal is viable.
In both cases lightweight construction materials are desirable but can be costly. This paper describes tyre bales as a lightweight
construction material and specifically addresses issues in relation to their use as a foundation material for roads over soft ground.
RÉSUMÉ : La construction de routes sur sol meuble présente des défis techniques considérables. Ces routes desservent souvent des
collectivités éloignées et connaissent de faibles niveaux de trafic ; leur construction et leur entretien doivent respecter des budgets très
serrés. Il existe deux méthodes principales pour ce type de construction : au-dessus du sol (construction flottante) et en dessous du sol
(construction enterrée). La construction flottante est généralement employée lorsqu'un matériau relativement rigide, comme la tourbe
fibreuse, repose sur un matériau moins compétent, tel que la tourbe amorphe. La construction enterrée est généralement privilégiée en
présence de matériaux plus compétents, ou de matériaux souples moins profonds dont l’élimination est viable. Dans les deux cas, il
est utile d’employer des matériaux de construction légers, qui peuvent cependant s'avérer coûteux. Cet article décrit les balles de
pneus comme matériau de construction léger et traite spécifiquement des problématiques liées à leur utilisation comme matériau
d’assise des routes sur sol meuble.
KEYWORDS: Sustainability, reuse, recycling, foundations, tyres, bales.
1 INTRODUCTION
The construction of roads over soft ground, such as peat,
presents considerable technical challenges. Many such roads
serve remote communities, carry only low levels of traffic, and
must be constructed and maintained within limited budgets.
Where the depth of soft soil is significant, the approach to
construction generally involves ‘floating’ the road on the
existing subsoil. This may also involve the use of temporary
surcharging and/or reinforcement at the base of the construction
to help spread the load. If the depth of peat or other soft material
is shallow then removal may be an option. The excavated
material is then replaced by more competent materials.
However, this does leave the issues of disposing of the
excavated material and of preventing the adjacent material from
flowing into the excavation. The resolution of either or both of
these issues can prove costly, and such costs will increase
rapidly with the depth of material excavated.
In both cases, the use of lightweight construction materials is
desirable. This paper introduces lightweight tyre bales focusing
upon their potential use as a road foundation material and draws
on the author’s experience in the UK and the USA. Relative to
conventional lightweight foundation materials such as expanded
polystyrene, the cost of tyre bale construction is relatively low.
2 TYRE BALES
Around 48M tyres (480,000 tonnes) are scrapped in the UK
each year. However, the issue of scrap tyres is by no means
unique to the UK and Europe. In the USA it has been estimated
that over two billion used tyres are stockpiled, and that 285M
are added each year (Winter et al. 2006). In the recent past the
bulk of waste tyres in the UK was stockpiled, disposed of in
landfill or illegally, or sent for energy recovery (Hird et al.
2001) or processed as waste-to-energy. In Europe the Landfill
Directive outlawed the disposal of tyres in landfill, with UK
exceptions being made for engineered works. In the USA a
number of fires in waste dumps comprising whole tyres, and
concerns regarding the potential flammability of tyre shreds and
chips, led the drive towards alternative solutions.
The majority of R&D activity has addressed tyre shred, chip
and crumb for use in construction works. An alternative is the
baling of whole tyres to produce rectilinear, lightweight/low
density, permeable, porous bales of high bale-to-bale friction.
2.1
Composition, properties and behaviour
Tyre bales comprise 100 to 115 car/light goods vehicle tyres
compressed into a lightweight block of mass around 800kg and
density
circa
0.5Mg/m
3
. The bales measure approximately 1.3m
by 1.55m by 0.8m and are secured by five galvanized steel tie-
wires running around the length and depth of the bale (Figure
1). They have considerable potential for use in construction
particularly where their low density and ease of handling places
them at a premium. A porosity of around 62% and permeability
of approximately 0.02m/s through the length and 0.2m/s
through the depth (Simm et al. 2005) makes them ideal for
drainage applications. The bale-to-bale friction angle is around
35
o
in dry conditions and stiffness in the vertical direction of
Figure 1 is up to around 1GPa (Frielich & Zornberg, 2009;
Winter et al. 2006). Furthermore, the process of tyre bale
manufacture consumes around 1/16 of the energy required to
shred a similar mass of tyres (Winter et al. 2006).
Road foundation construction using lightweight tyre bales
Construction des assises de routes à l'aide de balles de pneus légères
Winter M.G.
Transport Research Laboratory (TRL), Edinburgh, United Kingdom
