DEF Grilli Andrea PhD Thesis 2007.pdf

Chapter 1. Literature review – Part I
1. Literature review – Part I
Numerous detrimental factors affect the service life of asphalt
pavement in terms of mechanical and functional performance. These
factors, such as environmental conditions, subgrade conditions, traffic
loading and ageing, prematurely addressed to rehabilitation or
maintenance of asphalt pavements if not adequately took into account
during design and construction phases.
Moreover, pavement maintenance treatments can be ineffective if they
do not act against the real detrimental causes.
Nowadays, geosynthetics can be used for both long-term road during
initial construction and cost-effective maintenance (Brown 2006).
The five main functions of geosynthetics in road construction are:
• Separation and filtration;
• Stabilization;
• Reinforcement and Stress absorption.
The separation function is primary characteristic of geotextiles in road
construction. In this case, the geosynthetics acts as a separator
between the soft subgrade and the aggregates avoiding the intrusion of
cohesive soil in upper layers. In this way the initial thickness and
mechanical characteristics of road layers are preserved. In addition,
the separation function has to be combined with the filtration function
to allow water drainage and to avoid interstitial pressure which can
cause differential settlements.
The stiffness properties of geosynthetics are essential for the
stabilization function. A considerable reduction of aggregates or an
increasing of bearing capacity is possible by the use of a geosynthetics
which implies the membrane action, a lateral restrain and confinement
of aggregates.
The reinforcement function in a continuum body is obtained by
insertion of reinforcing materials able to improve mechanical
properties of the continuum body. The main reinforcement
mechanisms are:
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