Note: Descriptions are shown in the official language in which they were submitted.
CA 02302117 2000-03-27
2
Technical Field
The present invention relates generally to geocomposite systems, and more
particularly to using a geocomposite layer in the construction of roads and
bridges.
Background of the Invention
The United States has a public roadway infrastructure of more than 6.2
million kilometers with more than 575,000 bridges which is traveled by more
than 2.4
trillion vehicle-miles per year. Approximately 3.8 million kilometers of the
system are
paved road, 96% of these paved roads have flexible, or hot-mix asphalt,
pavements. It is
estimated that approximately one sixth of the more than 90 billion dollars
spent annually
by U.S. governmental agencies to enhance, rehabilitate, and maintain the
public roadway
infrastructure is spent on constructing and maintaining these paved roads.
Considering the magnitude of this type of annual investment, the potential
savings from developing improved and longer lasting pavement systems is
substantial.
For example, if the service life of a new pavement system is extended by three
years, i.e.,
twenty percent considering the average life of a pavement system is 15 years,
the savings
in hot-mix asphalt alone is estimated to be three billion dollars per year.
Furthermore, the
labor cost savings are estimated to be at least ten times this amount.
Another substantial expense involving the public highway infrastructure is
the rehabilitation and maintenance costs associated with the corrosion of
reinforcing steel
in bridge decks. In 1991, the backlog of public bridge repair and maintenance
costs was
estimated to be 78 billion dollars. It is also estimated that 40% of the
575,000 bridges are
structurally or functionally obsolete with reinforcing steel corrosion being
the major
cause of deterioration at more than 31 billion dollars.
In order to stem the overwhelming costs associated with the enhancement,
rehabilitation, and maintenance of the public highway infrastructure, several
techniques
have been developed which attempt to prevent or deter the deterioration and
eventual
breakdown of roads and the corrosion of reinforcing steel in bridges. For
example,
several techniques were used to abate corrosion in bridge decks including the
use of
sealers, coated reinforcing bars, cathodic protection, low permeability
concrete, and
CA 02302117 2000-03-27
3
waterproofing membranes, among others.
Possibly the most popular of these techniques is shown in one form in U.S.
Patent 4,362,780 to Marzocchi et al., wherein a single thickness fiber web is
asphalt
impregnated and laid between layers of the pavement system to impede the
downward
migration of water (or other liquids) into the roadbed or the bridge deck.
Although
successful in reducing the downward migration of some moisture, the web in the
'780
patent falls short in several functional areas, such as the ability to
laterally drain the water
away and providing a cushioning effect to alleviate weather and traffic
related damage.
Accordingly, while the use of impregnated fiber webs is generally known in
the art of constructing roads and bridges, to date no one has recognized and
adequately
addressed the advantages of providing a prefabricated, composite layer,
including an
impermeable membrane. Thus, there is a need to provide an improved
geocomposite
system to extend the service life of roads, bridges, or the like, and an
improved method of
construction with such a composite layer. The geocomposite system and method
should
make the best use of a flexible geomembrane combined with at least one
geotextile
backing to form a geocomposite layer to be located between adjacent
geocomposite
layers. This geocomposite layer so constructed should prove to provide water
impregnability in a vertical direction, but allow lateral drainage. Indeed, it
is
contemplated that utilizing a flexible geomembrane, and geotextile backings on
both
sides, can best carry out these intended purposes. In addition, there should
be a
significant improvement in the structural capacity and cushioning of the road
or bridge to
withstand rigorous dynamic loading by traffic. Costly cracking and
deterioration,
including due to water, is to be significantly reduced, and the life of the
road or bridge
significantly extended.
Summary of the Invention
Accordingly, the primary object of the present invention is to provide an
improved geocomposite system for extending the service life of roads, bridges,
or the like
by overcoming the limitations and disadvantages of the prior art and adopting
the
improvement features contemplated above.
Another object of the present invention is to provide a geocomposite system
CA 02302117 2000-03-27
4
wherein a geocomposite layer or web placed between an upper base layer and a
lower
structural layer of a roadway or bridge eliminates the vertical migration of
water.
A further object of the present invention is to provide a geocomposite layer
having a geomembrane disposed between first and second geotextile backings,
which
have sufficient porosity to provide a wicking action of water along both sides
of the
geomembrane and out of the geocornposite system.
It is still another object of the present invention to provide a geocomposite
system of the type described, which provides cushioning so as to dissipate
stress loads to
a level supportable by the base layer, and thus to alleviate load-related
cracking.
Still another object of the present invention is to provide a geocomposite
system utilizing a flexible and cushioned geomembrane capable of conforming to
the
base and structural layers of the roads and bridges.
Yet another object of the present invention is to provide a geocomposite
layer of the type described having a geomembrane of sufficient thickness to
allow easy
coupling of the geotextile backings prior to installation in the road or
bridge.
Another object of the present invention is to provide a geocomposite system
including a geocomposite layer with thermal properties sufficient to withstand
the
temperature of the base layer (e.g., hot-mix asphalt) during application of
the base layer
and having sufficient thickness so that milling of a wear surface of the base
layer will not
affect the geocomposite layer, thus allowing repair and replacement of a
portion of the
wear surface.
Yet another and related object of the present invention is to provide a
method of constructing a geocomposite system for use in a road, bridge, or the
like,
wherein the method includes fabricating a geocomposite layer, applying a tack
coat to a
structural layer of the road or bridge, laying the geocomposite layer on the
prepared
structural layer and rolling the geocomposite layer to insure conformity and
coupling, and
applying a tack coat to the geotextile backing on the exposed side of the
geocomposite
layer, and forming a base layer on the geocomposite layer.
Additional objects, advantages and other novel features of the invention
will be set forth in part in the description that follows and in part will
become apparent to
those skilled in the art upon examination of the following or may be learned
with the
CA 02302117 2000-03-27
10 practice of the invention. The objects and advantages of the invention may
be realized
and obtained by means of the instrumentalities and combinations particularly
pointed out
in the appended claims.
To achieve the foregoing and other objects, and in accordance with the
purposes of this invention, an improved geocomposite system is provided, and
is
contemplated to be utilized to increase the service life of roads, bridges, or
the like. The
geocomposite system includes a geocomposite layer disposed between and bonded
to a
structural layer and a base layer. More specifically, the geocomposite layer
is securely
bonded to each of the structural and the base layers by means of a tack coat
of a suitable
adhesive. Within the broadest aspects of the present invention, the
geocomposite layer
20 provides a barrier against the penetration or permeation of surface
moisture or liquid into
the structural layer, as well as, upward migration of ground moisture or
liquid into the
base layer. Additionally, the geocomposite layer placed in between conforms to
the base
and structural layers such that the load of passing vehicles is transferred
through the
geocomposite layer to the structural layer efficiently by dissipating the
applied stress.
In accordance with an important aspect of the present invention, the
geocomposite layer includes a geomembrane disposed between first and second
geotextile backings. The geotextile backings are fabricated of a mat of non-
woven
polypropylene fibers or, in the present preferred embodiment, as a mat of non-
woven
polyester fibers. The geotextile backings are securely adhered to the
geomembrane
30 through a heat coupling process, such as calendaring. Advantageously, this
process
allows the geocomposite to be fabricated and quality tested prior to
installation in the
road or bridge. The geomembrane is preferably extruded having a thickness in
the range
of 30 to 100 millimeters. In accordance with the broader aspects of the
present invention,
the geomembrane can be formed utilizing various known processes and utilizing
a
material selected from the group consisting of polyvinylchloride, very
flexible
polyethylene, linear low density polyethylene, low density linear
polyethylene, ethylene
propylene dime terpolymer, or chlorosuphonated polyethylene.
In accordance with another feature of the invention, the geomembrane is
impermeable and the geotextile backings are sufficiently porous to provide a
wicking
40 action of the moisture or liquid along the geomembrane. Advantageously, the
geotextile
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6
backings direct the moisture or liquid laterally, toward the edges of the road
or bridge,
while the geomembrane prevents the migration of water between the base layer
and the
structural layer. This is effective in preventing downward penetration or
permeation of
surface moisture into the structural layer, as well as, upward migration of
ground
moisture into the base layer. Overall, the combination of impeding and
directing the flow
of moisture or liquid is effective in preventing pooling within or between the
layers,
dissipating pore water pressure, limiting soil movement, and/or providing a
moisture
barrier that prevents water movement between layers. Each of these scenarios,
unless
corrected by use of the present invention, is singly capable of causing minor
to severe
damage to a road or bridge.
The geomembrane is also flexible and elastic allowing the geocomposite
layer to substantially conform to the structural and base layers of the road
or bridge.
Specifically, these positive conformal properties allow loads created by
constant traffic to
be transferred directly, but in a cushioned fashion and thus more efficiently,
to the
structural layer. The reduction or elimination of these undesirable load
conditions
reduces the proliferation of reflective (or rebound), shrinkage and fatigue
cracking in the
road or bridge. Even more specifically, the elasticity of the geomembrane
allows the
geomembrane to temporarily deform, thus cushioning and absorbing a significant
portion
of the lateral stresses imparted to the base layer by passing vehicles. This
increases the
effective overall tensile strength of the base layer, and necessarily, the
overall structural
capacity and durability of the road or bridge.
The geocomposite layer of the present invention preferably includes a
geomembrane having a thickness in the range of between 30 and 100 millimeters.
Preferably, the thickness of the base layer is sufficient to allow an upper
portion to be
removed and replaced without adversely affecting the geocomposite system, and
specifically, the bonds between the geocomposite layer and the structural and
base layers.
It is contemplated that the thickness of the base layer including the upper
wear surface
should be thick enough to allow milling of the wear surface/base layer up to
one-half inch
above the geocomposite layer to accommodate the later removal and replacement
of a
worn out wear surface. Advantageously, this greatly reduces the costs
associated with
maintenance of roads or bridges constructed in accordance with the present
invention.
CA 02302117 2000-03-27
7
In accordance with the broadest aspects of the present invention, the
geocomposite system can be utilized for new roads and bridges, or the like.
However, it
is further contemplated that a specific form of the geocomposite system of the
present
invention may be further utilized in the repair or rehabilitation of existing
roads and
bridges, and in known trouble spots in new construction areas, such as in
transition areas
between roads and bridges, or between train tracks at crossings, for example.
Preferably, the structural layer in a geocomposite system utilized with a
road includes a common sub-grade (road bed) or soil base, a subbase, and a
drainage
layer of aggregate stone, for example. Alternatively, the structural layer of
a
geocomposite system utilized with a bridge may simply include a steel deck
and/or a
reinforced concrete deck. The base layer for either may include one or more
layers of
asphalt, including an asphalt wear surface.
In the related method, the geocomposite system is constructed by first
fabricating the geocomposite layer. Preferably, the geomembrane is extruded
and the
geotextile backings are securely adhered to the geomembrane through a heat
coupling
process, such as by calendaring, just after extrusion. Advantageously, this
step is
preferably carried out prior to installation in the road or bridge.
Necessarily, this provides
a geocomposite of superior quality and uniformity than heretofore achieved
utilizing
known prior art methods.
Next, the structural layer of the road or bridge is prepared to receive the
geocomposite layer, preferably by applying a tack coat of a suitable adhesive
on top of
the structural layer. The geocomposite layer with a geotextile backing
engaging the
prepared structural layer absorbs a portion of the tack coat. A suitable force
is applied to
enhance the absorption of the tack coat into the geotextile backing and to
insure
substantial conformity of the geocomposite layer with the structural layer. An
additional
tack coat is applied to the top of the remaining exposed geotextile backing
prior to
forming the base layer. This insures a secure bond between the geotextile
backing and
both of the base and structural layers in either a road or bridge.
Still other objects of the present invention will become apparent to those
skilled in
this art from the following description wherein there is shown and described a
preferred
embodiment of this invention, simply by way of illustration of one of the
modes best
CA 02302117 2000-03-27
8
suited to carry out the invention. As it will be realized, the invention is
capable of other
different embodiments and its several details are capable of modification in
various,
obvious aspects all without departing from the invention. Accordingly, the
drawings and
description will be regarded as illustrative in nature and not as restrictive.
Brief Description of the Drawings
The accompanying drawings incorporated in and forming a part of the
specification, illustrate several aspects of the present invention and
together with the
description serve to explain the principles of the invention. In the drawings:
Figure 1 is a cross sectional view of the geocomposite system constructed
in accordance with the present invention, illustrating the geocomposite layer
within a
road and indicating the drainage movement of moisture or liquid through the
geotextile
backings to one edge of the geocomposite system and road edge;
Figure 2 is a perspective exploded view of the geocomposite system for a
road including the geocomposite Layer, the preferred structural layer, and the
preferred
base layer, all cut away in cross section for clarity;
Figure 3 is a cross sectional view of the geocomposite system for a bridge,
again illustrating the geocomposite layer within the geocomposite system, and
indicating
the lateral drainage of moisture or liquid through the geotextile backings to
a suitable
weep collection channel and exit passage;
Figure 4 is a side cross sectional view showing the preferred method of
forming the geocomposite layer including heat coupling, utilizing a
calendaring process,
the geotextile backings to the geomembrane prior to installation in the road
or bridge;
Figure 5 is an illustrated view showing the preferred method of constructing
the road or bridge including laying the geocomposite layer with the geotextile
backing on
top of the prepared structural layer, and applying a force, in the form of a
roller, to
enhance the absorption of adhesive and to conform the geocomposite layer to
the face of
the structural layer; and
Figure Sa is a side enlarged cross sectional view taken from Figure 5
showing the spray application of the tack coats, the conforming effect of the
applied force
on the geocomposite layer, and the enhanced absorption of the tack coat into
the
CA 02302117 2000-03-27
9
geotextile backing to form a secure bond.
Reference will now be made in detail to the present preferred embodiment
of the invention, an example of which is illustrated in the accompanying
drawings.
Detailed Description of the Preferred Embodiment
Reference is now made to the drawings showing a geocomposite system 10
forming a road in accordance with the present invention. As indicated above,
the
particular preferred embodiment chosen to illustrate the invention, and best
shown in
Figure 2, includes a geocomposite layer 12 disposed between a structural layer
14 and a
base layer 16 for extending the service life of the road. While the pavement
system 10 is
a preferred embodiment that takes full advantage of the present invention, it
is to be
understood that equivalent systems for extending the service Iife of roads,
bridges, or the
like are deemed to be within the broadest aspects of the present invention.
As best shown in Figure l, the geocomposite layer I2 provides a barrier
against the penetration or permeation of surface moisture or liquid (S) into
the structural
layer 14, as well as, upward migration of ground moisture or liquid (G) into
the base
layer 16. In other words, geocomposite layer 12 provides a barrier sufficient
to prevent
the vertical penetration or migration of moisture or liquid between the layers
of the
geocomposite system 10. Additionally, the geocomposite layer 12, and
specifically
geotextile backings 20 and 22 retain sufficient porosity to provide a path
based on
wicking action for the moisture or liquid horizontally along geomembrane 18
out of the
geocomposite system 10 to a suitable stabilized edge drain system 24 for
release beyond
the shoulder of the road.
More specifically, the moisture or liquid (S or G) entering the geocomposite
system 10 is absorbed and flows or weeps through the geotextile backings 20
and 22 to
the edge drain system 24. The edge drain system 24, in the present preferred
embodiment, is a trough formed beyond the edge of the emergency travel
shoulder T of
the pavement system 10. The semi-permeable stabilized aggregate stone and/or
soil
receives the flow of moisture or liquid from the geotextile backings 20 and 22
and directs
it away from the road.
While the preferred edge drain system 24 is one commonly utilized along
CA 02302117 2000-03-27
10 roadways and in other applications, it is to be understood that other like
systems for
moving moisture or liquids away from the geocomposite system 10 are deemed to
be
within the broadest aspects of the present invention. For example, a sub-
surface
geotextile wrapped permeable pipe with spaced weep passages directed away from
the
shoulder could also perform the function.
The geocomposite layer 12 is both flexible and elastic. Advantageously,
these properties allow the geocomposite layer 12 to conform to the structural
layer 14 and
the base layer 16. This allows the dynamic loading of passing vehicles to be
transferred
directly through the geocomposite layer 12 which acts as a stress absorption
layer above
the structural layer 14. This is of increased importance in geocomposite
systems wherein
the structural layer is subjected to more severe stress, or in transition
areas such as
between a road and a bridge, for example. Absent these stress absorption
properties, the
geocomposite layer 12 would transmit all loads into the structural layer from
the passing
vehicles. The reduction or elimination of these undesirable stress loading
conditions
reduces the proliferation of reflective (or rebound), fatigue and shrinkage
cracking in
roads or bridges.
The elasticity of the geomembrane allows the geomembrane 18 to
temporarily deform up to 250 percent. This property allows a large portion of
the vertical
stresses, but especially the lateral stresses, imparted to the base layer by
passing vehicles
to be cushioned, and in effect absorbed by the geomembrane 18, thus preventing
the
transfer of stresses to the structural layer 14. As noted above, this
increases the overall
tensile strength of the structural layer 14 and the durability of the
geocomposite system,
and decreases the possibility of excessive sub grade deformation which may
occur
resulting in pavement cracking, rutting and other distresses.
As indicated above, the preferred geocomposite system 10 includes the
geocomposite layer 12 disposed between the structural layer 14 and the base
layer 16.
Specifically, the structural layer 14 (shown in Figure 2) includes a sub grade
26; an
aggregate layer 28, and a treated aggregate layer 30. The base layer 16
comprises a base
hot-mix asphalt course 32 and a wear hot-mix asphalt course 34. In this
preferred
embodiment, the geocomposite layer 12 is specifically disposed between the
upper most
layer of the structural layer 14, i.e., it is between the treated aggregate
layer 30 and the
CA 02302117 2000-03-27
11
base hot-mix asphalt course 32.
In accordance with the broadest aspects of the present invention, the
structural layer 14 and the base layer 16 may include several distinct and
varying layers
and layer combinations dependent upon the specific road or bridge application.
While
the preferred structural layer 14 takes full advantage of the present
invention, it is to be
understood that other combinations and methods for forming the structural
layer 14 are
deemed to be within the broadest aspects of the present invention. For
example, the
structural layer 14 may include more than one aggregate or treated subbase
layer.
Further, the base layer 16 could include an additional intermediate hot-mix
asphalt layer,
for example, or it could be made semi-rigid, including a stabilized aggregate
layer and/or
a concrete slab.
In addition to the various possible combinations of layers forming the
structural layer 14 and the base Iayer 16, the placement of the geocomposite
layer 12
within the geocomposite system 10 may also vary dependent upon the specific
required
application. For instance, the geocomposite layer 12 may alternatively be
placed between
the base hot-mix asphalt course 32 and the wear hot-mix asphalt course 34
within the
base layer I6. This placement may be preferred for certain repair or
rehabilitation
purposes to reduce fatigue cracking due to its ability to absorb stress/strain
energy.
Similarly, it could be placed between the sub grade 26 and the aggregate layer
28 within
the structural layer 14 for specific wetland applications.
As shown in Figure 3, an alternate embodiment of the present invention
includes a geocomposite system 40 for a bridge having a geocomposite layer 42
disposed
between a structural layer 44 and a base layer or overlay 46. In this
preferred alternate
embodiment, the structural layer 44 includes a bridge deck 48 and a reinforced
concrete
deck 50, with or without reinforcement bars 52. The base layer 46, on the
other hand, is
simply a hot-mix asphalt wear course 54. As in the geocomposite system 10
utilized for
roads, the geocomposite layer 42 and specifically geotextile backings 56 and
58 provide a
wicking action for Lateral movement of moisture or liquids along the
geomembrane 60 to
the channel 62 and weep passages 64.
As clearly shown in Figure 3, the geocomposite system 40 is designed to
extend the service life of the bridge primarily by providing a barrier against
the
CA 02302117 2000-03-27
12
penetration of surface moisture or liquid into the structural layer 44. More
specifically,
the geocomposite system 40 protects the bridge deck 48 and the reinforcement
bars 52
from the corrosive properties typically associated with moisture and other
liquids, such as
chloride ions and other solutions, that result from use of ice and snow
control materials in
the colder climates and/or splashing of seawater.
According to the present invention, the geocomposite layer 12 is
completely fabricated and quality tested prior to installation in the road
geocomposite
system 10 or bridge geocomposite system 40. Advantageously, this provides a
superior
quality and uniformity than was heretofore available with prior road or bridge
geocomposite systems where the impermeable barriers are formed at the
worksite.
In accordance with the broadest aspects of the present invention, the
geomembrane 18 is a plastic or rubber web. Preferably, the web is selected
from the
group consisting of polyvinylchloride, a very flexible polyethylene, a linear
low density
polyethylene, a low density linear polyethylene, an ethylene propylene dime
terpolymer,
or a chlorosuphonated polyethylene and has a thickness in the range of 30 to
100
millimeters. More preferably, the geomembrane 18 is an extruded
polyvinylchloride
plastic web with a thickness in the range of 60 to 100 millimeters and most
preferably,
the thickness is substantially 80 millimeters. It is generally accepted that a
20 millimeter
plastic or rubber membrane is sufficient to provide the impermeable barrier
capable of
preventing the migration or permeation of moisture or liquid. However, a 20
millimeter
membrane provides no margin to protect against damage during construction.
Thus, the
present preferred geomembrane 18 inherently provides a margin {50 to 400
percent)
against damage during construction, or during repair work, such as
resurfacing.
The geotextile backings 20 and 22 are fabricated of a mat of non-woven
polyester or polypropylene fibers having a density in the range of 100-400
grams per
square meter (g/m2). Most preferably, the geotextile backings 20 and 22 are
non-woven
polyester fibers having a density of 150-200 grams per square member {g/m2).
As shown
in Figure 4, the geotextile backings 20 and 22 are heat bonded to the
geomembrane 18,
preferably just after extrusion, such as by calendaring or rolling under
pressure. The
preferred range of thickness of the geomembrane 18 is necessary to accommodate
proper
bonding, while assuring retention of the proper wicking action in the backings
20, 22.
CA 02302117 2000-03-27
13
Advantageously, the fabricated geocomposite layer 12 may be transported
to the construction site on a conventional transport vehicle T in a roll
(shown in Figure
Sa), where it is easily unrolled during construction of the road or bridge.
The road or bridge construction method of the present invention can now be
explained in more detail. As a first step, the geocomposite layer 12 is formed
off site (see
Figure 4), by a calendaring process, and brought to construction site on a
trailer T (see
Figure 5). The structural layer 14 of the road or bridge geocomposite system
10 or 40 is
prepared in the cut of the ground or on the bridge deck. It is leveled to
receive the
geocomposite layer I2. A tack coat C, forming a suitable adhesive is applied,
such as by
a sprayer E, (Figure Sa). Preferably, the tack coat C, is an asphalt
elastomeric
composition. For example, an emulsified, liquid asphalt, which includes
bituminous
andlor non-bituminous components, can be economically used. The composition
selected
should be capable of assuring that the geotextile backing 20 is securely
mechanically
bonded to the upper face of the structural layer 14.
As shown in Figures 5 and Sa, the geocomposite layer 12 is thus laid onto
the upper face of the prepared structural layer 14. The geotextile backing 20
advantageously generally conforms to the face, and absorbs the tack coat C,
for bonding.
In the preferred method, an outside farce sufficient to insure full conformity
of the geocomposite layer 12 to the structural layer 14, and a more complete
absorption
of the tack coat C" is applied. The force may be applied in the form of a
conventional
road construction roller R. The roller R thus forces the geocomposite layer 12
into
intimate contact with the tack coat C, and the structural layer 14 so that the
geotextile
backing 20 is now securely adhered to the structural layer 14.
Of course, several webs of the geocomposite layer 12 are laid in an abutting
end-to-end/side-to-side relationship with overlapping edges to form a
road/bridge section.
Next, the geotextile backing 22 is prepared to receive the base layer 16.
Specifically, tack
coat CZ, the same as described above, is sprayed on the geotextile backing 22
by sprayer
E2. The base layer 16, for example, is then formed by a mechanical payer, and
simultaneously bonded to the geotextile backing 22. Again, a conventional
roller (not
shown) used in road construction (see the roller R) finishes the road or
bridge deck
through compacting the base layer 16, and in turn pressing the backing 22 into
the tack
CA 02302117 2000-03-27
14
coat C2 .
In summary, the results and advantages of the present invention can now be
fully understood. The road and bridge geocomposite systems 10 and 40 include a
geocomposite layer 12 having a geomembrane 18 disposed between two geotextile
backings 20, 22, a structural layer 14 for supporting the geocomposite layer
12, and a
base layer 16 formed on top of the geocomposite layer 12. Advantageously, the
geomembrane 18 is impermeable to block the movement of moisture vertically
between
the structural and base layers 14, 16. At the same time, the geotextile
backings 20, 22 are
sufficiently porous to provide horizontal wicking action for the moisture or
liquids
causing it to move harmlessly to the lateral edges of and away from the road
or bridge.
Additionally, the geomembrane 18 is sufficiently flexible and resilient to
conform to the
layers 14, 16 of the geocomposite system 10, thereby providing a cushioning
effect that is
operative in increasing the structural capacity. As a result, reflective,
shrinkage and
fatigue cracking and other damage is minimized.
The foregoing description of a preferred embodiment of the invention has
been presented for purposes of illustration and description. It is not
intended to be
exhaustive or to limit the invention to the precise form disclosed. Obvious
modifications
or variations are possible in light of the above teachings. The embodiment was
chosen
and described to provide the best illustration of the principles of the
invention and its
practical application to thereby enable one of ordinary skill in the art to
utilize the
invention in various embodiments and with various modifications as is suited
to the
particular use contemplated. All such modifications and variations are with in
the scope
of the invention as determined by the appended claims when interpreted in
accordance
with breadth to which they are fairly, legally and equitably entitled.