Note: Descriptions are shown in the official language in which they were submitted.
1
SYNTHETIC GROUND COVER SYSTEM FOR EROSION CONTROL
BACKGROUND
[0001] The prior art discloses systems for erosion protection that
typically take the form
of a combination of synthetic mat and natural grass. Additionally, the prior
art generally requires
multiple anchors to resist wind uplift and erosion forces on the synthetic
mat. Thus, the industry
continues to search for improved erosion protection systems which are
effective, economical and
meet the various local, state and federal environmental laws, rules and
guidelines for these
systems.
100021 Artificial grass has been extensively used in sport arenas (playing
fields) as well
as along airport runways and in general landscaping. A primary consideration
of artificial turf
playing fields is the ability of the field to drain. Examples of prior art in
synthetic grass drainage
are U.S. Pat. Nos. 5,876,745; 6,858,272; 6,877,932 and 6,946,181. However,
these artificial
grasses are generally only suitable for field playing surfaces where the
ground is substantially
flat and the concern is only with the ability to improve field playing
conditions.
[0003] The drainage use in the prior art of artificial turf deals
principally with slow
infiltration of flat surfaces to avoid inundation of the field, and such
drainage use generally
cannot handle the very large and rapid run-off that would occur on very large
and steep
sideslopes of natural or man-made ground topography, such as landfills,
stockpiles, berms,
embankments, levees, drainage channels, mine tailing piles, etc.
SUMMARY OF THE INVENTION
[0004] Briefly described, the present invention provides a new and useful
system for
covering various types of sloping ground where water and wind erosion
protection are needed.
More particularly, in a first example form the invention comprises a synthetic
ground cover
system for erosion control to be placed atop substantially non-level, sloping
ground, including a
synthetic grass which comprises a composite of an impermeable backing and
synthetic grass
blade-like elements secured thereto and extending therefrom. An infill ballast
is applied to the
synthetic grass atop the backing and a binding agent is applied to the infill
ballast t protect the
infill ballast against high velocity water shear forces. With this
construction, the synthetic
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ground cover system can remain in place atop substantially non-level, sloping
ground despite
shear forces from gravity, wind, and water flow.
[0005] Preferably, the impermeable backing comprises a geotextile.
Optionally, the
impermeable backing comprises a permeable geotextile and an impermeable
polymer applied to
the permeable geotextile to make the backing impermeable. Optionally, the
impermeable
polymer comprises Polyethylene, Polypropylene, Polyurethane, Ethylene
Propylene Diene
Terpolymer (EPDM), or Polyvinyl Chloride (PVC).
[0006] In a broad aspect, the invention pertains to a synthetic ground
cover system for
erosion control to be placed atop substantially non-level, sloping ground.
There is a synthetic
grass which comprises a composite of an impermeable backing attached to an
underside of a turf
backing, and synthetic grass blade-like elements are secured thereto and
extend therefrom. The
impermeable backing is affixed thereto to strengthen the turf backing, and the
connection
between the blade-like elements and the turf backing. An infill ballast is
applied to the synthetic
grass atop the turf backing, and a binding agent is applied to the infill
ballast to protect the infill
ballast against high velocity water shear forces. The synthetic ground cover
system can remain
in place atop substantially non-level, sloping ground despite shear forces
from gravity, wind, and
water flow. Water present above the turf backing is prevented from penetrating
the soil by the
impermeable backing.
[0007] In one optional form, the impermeable polymer is laminated, glued,
sprayed, or
coated on the permeable geotextile.
[0008] Preferably, the impermeable polymer is non-flat for gripping the non-
level,
sloping ground.
[0009] Optionally, the binding agent in the synthetic ground cover system
for erosion
control is cement, grout, lime or the like. Optionally, the binding agent can
comprise a polymer.
100101 Preferably, the binding agent applied to the infill results in a
bound infill having a
depth of between about 1/2 inch and about 2 inches. Also, preferably the
infill is applied to the
synthetic grass in a dry condition and then is wetted later to be cured into a
bound infill.
Preferably, the infill comprises a sand or granular material and the
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binding agent comprises cement Preferably, the sand-to-cement ratio is between
about 1:1 and 3:1 by weight.
[0011] Optionally, the synthetic ground cover also includes at least one
filter
fabric to be placed on or in the ground and an open grid mesh positioned
between the
synthetic grass and the filter fabric. Preferably, the at least one filter
fabric comprises
non-woven synthetic fabric. Also preferably, the open grid mesh comprises a
synthetic
drainage system. Optionally, the synthetic ground cover can include at least
one low
permeability barrier geomembrane to be placed adjacent the ground.
[0012] Optionally, the synthetic grass has a density of between about 20
ounces
per square yard and 120 ounces per square yard. Preferably, the synthetic
grass has
fibers with an average length of between about 0.5 and 4 inches that act as
reinforcement for the sand/soil infill. Optionally, the synthetic grass has
fibers with an
average length of between about 1.5 and 3 inches
[0013] Preferably, the filter fabric is positioned to be in direct contact
with the
ground surface and comprises woven synthetic fabric. Alternatively, the
synthetic fabric
can be a non-woven material.
[0014] In another example form, the invention comprises a method of
covering
ground for erosion control. The method includes the steps of: (a) placing a
synthetic
grass atop the ground, the synthetic grass having a backing and synthetic
grass blades
extending therefrom; (b) applying a dry infill ballast to the synthetic grass;
and (c)
applying a wetting agent to the dry infill to cure the dry infill into a bound
infill to stabilize
the infill against high velocity water shear forces.
[0015] Optionally, the dry infill ballast includes cement and the wetting
agent
comprises water.
[0016] In another example form, the invention comprises a method of
covering
ground for erosion control. The method includes the steps of: (a) placing a
synthetic
grass atop the ground, the synthetic grass having a backing and synthetic
grass blades
extending therefrom; (b) applying a dry infill ballast to the synthetic grass;
and (c)
applying a wet binding agent to the dry infill to bond the dry infill into a
bound infill to
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stabilize the sand/soil infill against high velocity water shear forces.
[0017] Optionally, the dry infill ballast includes granular material and
the binding
agent comprises a polymer. In another form, the binding agent comprises a
cementitious slurry.Optionally, the dry infill ballast can include sand and/or
gravel.
[0018] It is to be understood that this invention is not limited to the
specific
devices, methods, conditions, or parameters described and/or shown herein, and
that
the terminology used herein is for the purpose of describing particular
embodiments by
way of example only. Thus, the terminology is intended to be broadly construed
and is
not intended to be limiting of the claimed invention. For example, as used in
the
specification including the appended claims, the singular forms "a," "an," and
"one"
include the plural, the term "or" means "and/or," and reference to a
particular numerical
value includes at least that particular value, unless the context clearly
dictates
otherwise. In addition, any methods described herein are not intended to be
limited to
the sequence of steps described but can be carried out in other sequences,
unless
expressly stated otherwise herein.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0019] Figure 1 is a schematic, sectional view of a synthetic ground cover
system for erosion control according to a first example of the present
invention.
[0020] Figure 2 is a schematic, sectional view of a synthetic ground cover
system for erosion control according to another example of the present
invention,
shown with an open mesh grid drainage at the bottom of the system.
[0021] Figure 3A is a schematic, sectional view of a synthetic ground
cover
system for erosion control according to another example of the present
invention.
[0022] Figure 3B is a schematic, detailed sectional view of the synthetic
ground
cover system for erosion control of Figure 3A.
[0023] Figure 4 is a schematic, sectional view of a synthetic ground cover
system for erosion control according to another example of the present
invention.
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[0024] Figure 5A is a schematic, sectional view of the synthetic ground
cover
system for erosion control of Figure 1 and shown installed over terrain of
various
slopes.
[0025] Figure 5B is a schematic, detailed sectional view of the synthetic
ground
cover system for erosion control of Figure 5A.
[0026] Figure 6A is a schematic, sectional view of a synthetic ground
cover
system for erosion control according to another example of the present
invention.
[0027] Figure 6B is a top perspective view of the synthetic ground cover
of
Figure 6A.
[0028] Figure 6C is a bottom perspective view of the synthetic ground
cover of
Figure 6A.
DETAILED DESCRIPTION
[0029] The present invention provides an erosion protection layer for use
in
embankments, ditches, levees, water channels, downchutes, landfills and other
steep
topographic ground conditions that are exposed to shear forces of water and
winds.
[0030] In one example form of the present invention, a synthetic grass is
used in
combination with a bound/stabilized infill ballast to provide a new and useful
ground
cover system, while also providing a beneficial erosion protection system that
does not
require maintenance. This combination (sometimes referred to as a composite
material)
can be used for covering slopes and lining drainage ditches, swales, and
downchutes.
With the cover system of this invention, owners and operators can realize
significant
cost savings by constructing a cover system with synthetic grass that does not
require
the vegetative support and does not require a topsoil layer typical of the
known prior art
final cover systems.
[0031] More particularly, in a first example form the invention comprises
a
synthetic ground cover system for erosion control to be placed atop the
ground,
including a synthetic grass which comprises a composite of one or more geo-
textiles
tufted with synthetic yarns. The synthetic ground cover also includes a
stabilized/bound
infill ballast applied to the synthetic grass (stabilized against high
velocity water shear
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forces).
[0032] Optionally, the infill ballast comprises a sand or soil and is
bound with a
binding agent, such as cement, grout, lime or the like.
[0033] With this invention, down-chutes and ditches can be lined with this
system
to resist large shear forces of water and wind without washing the soil below
the
system. The artificial turf provides for separation of the sand infill from
the ground below
and the turf blades act as structural reinforcement of the sand infill while
providing an
aesthetically pleasing surface. The sand infill on top is stabilized against
washing or
blowing away by a binding agent applied to the sand infill, which generally
has the effect
of cementing or bonding together the sand. This allows the invention to resist
large
shear forces from water or wind. In this regard, the bonding strength need not
be
terribly high. Indeed, it is not necessary to achieve a structural strength as
great as
concrete, for example. Instead, it is sufficient that the binding agent merely
hold the
sand together against erosive forces of wind and water. In this regard, the
sand/soil is
bound to the other sand particles and/or to the synthetic turf blades by the
binder.
[0034] Figure 1 is a schematic, sectional view of an example synthetic
ground
cover system 110 for erosion control according the present invention and
showing the
surface of the soil S covered with the present ground cover erosion control
system. The
system includes a synthetic turf 140 which includes a backing 142 and
synthetic turf
blades 141 secured to the backing. A stabilized/bound sand/soil infill 160 is
placed in
the bottom of the synthetic turf 140 above the backing 142. The soil S can be
topped
with a sand subgrade, gravel subgrade, or intermediate cover before laying
down the
synthetic ground cover system 110 for erosion control, as desired. In this
first example
embodiment, the synthetic turf 140 is placed more or less directly atop the
soil S. As
will be seen below, the system can also be provided with additional elements
interposed
between the soil S and the turf 140.
[0035] Preferably, the synthetic turf 140 is used as a principal component
of the
synthetic ground cover system. It can be constructed using a knitting machine
or tufting
machine that may use, for example, over 1,000 needles to produce a turf width
of about
15 feet. Preferably, the synthetic turf includes synthetic grass blades 141
which
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comprise polyethylene monofilament and/or slit-film fibrillated and non-
fibrillated fibers
tufted to have a blade length of between about 0.5 inches and 4 inches. Other
polymers can be used for the synthetic grass blades, as desired. Preferably,
the
synthetic grass blades 141 are tufted to have a blade length of between about
1.5
inches and 3 inches. Most preferably, the synthetic grass blades 141 are
tufted to have
a blade length of about 1.5 inches. Optionally, the synthetic grass blades 141
are tufted
to have a density of between about 20 ounces/square yard and about 120-
ounces/square yard. Preferably, the synthetic grass blades have a thickness of
at least
about 100 microns.
[0036] The synthetic grass blades 141 are tufted into the substrate or
backing
142 comprising a synthetic woven or non-woven fabric. Moreover, this backing
can be
a single ply backing or can be a multi-ply backing, as desired. Optionally, a
geo filter
can be secured to the substrate to reinforce the substrate and better secure
the
synthetic grass blades.
[0037] The chemical composition of the synthetic turf components should be
selected to resist degradation by exposure to sunlight, which generates heat
and
contains ultraviolet radiation. The polymer yarns should not become brittle
when
subjected to low temperatures. The selection of the synthetic grass color and
texture
should be aesthetically pleasing.
[0038] The actual grass-like components preferably consist of green
polyethylene
fibers 141 of about 1.5 to about 2.5 inches in length tufted into a woven or
non-woven
geotextile(s). For added strength in severely steep sideslopes, an additional
geo filter
component backing can be tufted for improving dimensional stability. The
polyethylene
grass filaments 141 preferably have an extended operational life of at least
15 years.
[0039] A sand/soil layer 160 of about 0.5 to about 2.0 inches is placed
atop the
synthetic turf as infill to ballast the material and protect the system
against wind uplift as
well as to provide dimensional stability. Preferably, the infill is between
about 0.5 and 1
inches. The sand/soil layer provides additional protection of the geotextiles
against
ultraviolet light. Moreover, the sand/soil ballast is bonded with cement,
grout, lime or
another binding agent in order to resist the shear forces of water and wind on
steep
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side-slopes, drainage ditches and down-chutes. In this regard, the synthetic
turf 140 is
first placed over the ground and then the sand/soil infill is spread over the
synthetic turf
in dry form. This allows the dry infill material to easily and effectively
settle into the
bottom of the synthetic turf. Thereafter, the infill is watered (as by
spraying water over
the turf) and allowed to cure into a hardened, bound infill layer. In this
regard, the
sand/soil infill is bound to itself and is bound to the individual blades of
the synthetic turf.
Thus, in the event that the bound infill should become cracked in places, the
individual
blades of the turf act as anchors and help hold the bound infill in place.
[0040] The "sand/soil" infill includes true sands (including silica sands,
quartz
sands, etc), soils, clays, mixtures thereof, etc. It also includes things that
are like sand
or soil. For example, granular tailings from rock quarries could be employed
(things like
granular marble, quartz, granite, etc). Also, small gravel can be used as the
"sand/soil"
infill. In this regard, it is preferred that the infill be inorganic in nature
so as to be very
stable and long-lasting. But organic granular material could be employed in
certain
applications. Moreover, the binding agent could be inorganic or organic.
Preferably,
the binding agent is inorganic (again, for stability and long life). The
cements, grouts,
liming agents, etc., fit this application well. But other binding agents, such
as organic
binders, could be employed. For example, polymer-based binders could be used
(for
example, a urethane product). Indeed, in recent times a spray-on binding agent
has
come to market for binding small gravel in pathways under the brand name
"Klingstone"and sold by Klingstone, Inc. of Waynesville, NC.
[0041] Applicants have found that a recipe of about three parts sand and
one part
cement works well as a dry infill. Once wetted and cured, this bound sand
infill provides
an excellent ballast against lifting of the turf by wind and also resists
damage or erosion
from wind or rain or high water flows. A recipe of about equal parts sand and
cement
also works well, as do ratios between these two examples. However, for
economic
reasons, one should choose to use only as much cement as is needed to hold the
infill
together and to the synthetic turf blades, as cement is more costly than sand
(generally). Thus, recipes closer to 3:1 are generally more economical but
have lower
strength, while recipes closer to 1:1 are generally stronger, but more
expensive.
Moreover, a recipe of 2:2:1 of sand/cement/lime works well also. Also, instead
of lime
9
one can use fly ash.
[0042]
Advantageously, the present invention can be used even where high
concentrated flows are expected (e.g.. downchutes, large drainage swales). To
this end
the sand/soil infill is stabilized with a binding agent, such as cement,
grout, lime, etc.
This creates a more or less grouted or bound sand/soli infill 160 to resist
the shear
forces of water flow and wind.
[0043] This
invention combines the use of a synthetic grass to provide a pleasant
visual appearance, erosion protection with very minimal maintenance. The
invention
incorporates a bound infill that, together with the synthetic grass, can
handle very rapid
water run-offs. Thus, the cover system of this invention can be installed on
very steep
slopes which typically occur in embankments, levees, dams, downchutes,
landfills and
stockpiles. The system can be used as erosion control material that can resist
large
shear forces of water or wind.
[0044] In
addition to the embodiments described above, the system can take
other forms. For example, the system can comprise a membrane with a drainage
layer
overlain by synthetic turf having cemented (stabilized) infill using any of
the binding
agents described herein and the like. In such an embodiment, a bottom layer
includes a
structured low permeable membrane (optionally with textured or spikes on
bottom side
and drainage studs on top side) and a top layer. The top layer can include
turf (with, for
example, 1.5 inch pile height) and an infill of sand, lime and cement mixture.
In one
example, the infill can be 0.75 inches of the mixture.
[0045] Figure 2
is a schematic, sectional view of a synthetic ground cover
system 210 for erosion control according to a second example of the present
invention,
shown with an open mesh grid at the bottom of the system. Similarly to the
example
embodiment of Figure 1, the example cover system 210 for erosion control shown
in
Figure 2 is used to control erosion of the soil S. The system 210 includes a
lower filter
fabric (geofilter) 220, an open grid mesh or geo-net 230 and a synthetic turf
240. The
synthetic turf 240 includes a backing 242 and blades 241 secured to the
backing. A
stabilized/bound sand/soil infill 260 is placed in the bottom of the synthetic
turf 240
above the backing 242. The soil S can be topped with a sand subgrade, gravel
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subgrade, or intermediate cover before laying down the synthetic ground cover
system
210 for erosion control, as desired. Preferably, the lower filter fabric 220
comprises a
woven or non-woven synthetic fabric. In some applications, the lower filter
fabric 220
can be replaced with a barrier geomembrane with low permeability.
[0046]
Figures 3A and 3B depict a synthetic ground cover system 310 for
erosion control according to a third example of the present invention, shown
without an
open mesh grid at the bottom of the system. Similarly to the example
embodiment of
Figure 1, the example cover system 310 for erosion control shown in these
figures is
used to control erosion of the soil S. The system 310 includes an impermeable
geomembrane 350 and a synthetic turf 340. The impermeable geomembrane 350 is a
polymeric sheet with slender spikes on the bottom surface and cleat-like or
stud-like
nubs on the top surface. For example, see upper nubs 351-354 and spikes 357-
359.
The lower spikes help anchor the impermeable geomembrane to the soil S and the
upper nubs help anchor the synthetic turf 340 to the impermeable geomembrane
350.
The upper nubs also provide a transmissive drainage layer or space in which
water can
flow over the membrane beneath the synthetic turf. The synthetic turf 340
includes a
backing 342 and blades 341 secured to the backing. A stabilized/bound
sand/soil infill
360 is placed in the bottom of the synthetic turf 340 above the backing 342.
[0047]
Figure 4 is a schematic, sectional view of another synthetic ground cover
system 410 for erosion control according to the present invention, shown with
a
reinforcement layer on the backing of the synthetic turf.
Similarly to the example
embodiment of Figure 1, the example cover system 410 for erosion control shown
in
Figure 4 is used to control erosion of the soil S. The system 410 includes a
synthetic
turf 440 which includes a backing 442 and blades 441 secured to the backing.
The
backing 442 can be a single ply backing or a multi-ply backing. A urethane
barrier 443
is applied to the underside of the backing 442 and acts to both strengthen the
backing
and the connection between the blades 441 and the backing 442. The urethane
barrier
443 also makes the backing 442 generally impermeable to water. A
stabilized/bound
sand/soil infill 460 is placed in the bottom of the synthetic turf 440 above
the backing
442.
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[00481 Figures 5A and 5B show the example embodiment of Figure 1 applied
over a terrain of varying slopes. This synthetic ground cover system 110 has
the
capacity to handle high-intensity precipitation and avoids erosion of the
sand/soil infill
ballast and/or the shearing stresses on the turf ranging from 1 pound per
square foot to
more than 25 pounds per square foot.
[0049] The applicants have found that sand works particularly well as the
primary
ballast agent, although soil works well as well. Even small gravel could be
employed as
the primary ballast agent. Moreover, the applicants have found that the
binding agent
that works the best in most applications is cement, although other binding
agents could
work also. Thus, while cementitous materials are the preferred binders, other
materials
could work also
[0050] Figure 6A is a schematic, sectional view of a synthetic ground
cover
system 610 for erosion control according to another example of the present
invention.
Similarly to the example embodiment of Figure 1, the ground cover system 610
for
erosion control is used to control the erosion of the soil S. The system 610
generally
includes a synthetic turf 640 which includes a backing 642 and blades 641
secured to
the backing. The backing 642 can be a single ply or a multi-ply backing. An
impermeable backing or layer 650 is applied to or formed on the underside of
the
backing 642 and acts to strengthen both the backing 642 and the connection
between
the blades 641 and the backing 642. Preferably, the impermeable layer 650
makes the
backing 642 generally impermeable to water, thus water or other liquids
present above
the backing 642 are prevented from penetrating the soil S. An infill ballast
660 is
applied to the synthetic grass atop the backing and a binding agent is applied
to the infill
ballast to protect the infill ballast against high velocity water shear
forces.
0051
Preferably, the impermeable layer or backing 650 comprises a geotextile.
Optionally, the impermeable layer 650 comprises a permeable geotextile and an
impermeable polymer applied to the permeable geotextile to make the layer 650
impermeable.
Optionally, the impermeable polymer comprises Polyethylene,
Polypropylene, Polyurethane, EPDM, or PVC. In one form, the impermeable
polymer is
sprayed onto the permeable geotextile and then cured. Optionally, the
impermeable
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polymer is laminated, glued, coated, or otherwise applied to the permeable
geotextile.
In example forms, the impermeable backing 650 is substantially non-flat for
gripping the
non-level, sloping ground (see Figure 6B).
[0052] In one optional form, solid elements may be incorporated with the
impermeable polymer to provide for greater gripping ability when placing the
ground
cover system 610 on non-level, sloping ground. For example, in one form, a
plurality of
solid or pointy jack-like objects are placed on the permeable geotextile and
the
impermeable polymer is applied to the permeable geotextile, thus affixing the
plurality of
objects thereto to provide a non-flat impermeable layer 650. In another
optional form,
the plurality of objects are incorporated within the impermeable polymer and
are affixed
to the permeable geotextile upon spraying or applying the impermeable polymer
on the
permeable geotextile. In yet another optional form, a generally thin grid-like
component
comprising a plurality of spikes or extruding members is placed atop the
permeable
geotextile and the impermeable polymer is applied atop the grid-like
component,
thereby affixing the grid-like component in the impermeable layer 650.
[0053] Preferably, by providing the non-flat impermeable layer 650 that is
affixed
to the ground cover system 610, the ground cover system 610 can be installed
on non-
level, sloping ground in a one-step process, which can be seen to reduce
manufacturing
and installation costs.
[0054] There are many advantages to the cover system of this invention.
The
cover system reduces construction costs, reduces annual operation and
maintenance
costs while providing superior and reliable/consistent aesthetics. It also
reduces the
need for expensive riprap channels and drainage benches, with substantially no
erosion
or siltation problems, even during severe weather. It is a good choice in
sensitive areas
where soil erosion and sedimentation are major concerns because soil loss is
substantially reduced. It also eliminates the need for siltation ponds and
associated
environmental construction impacts. It allows for steeper slopes, because
there will be a
reduced risk of soil stability problems.
[0055] While the invention has been shown and described in exemplary
forms, it
will be apparent to those skilled in the art that many modifications,
additions, and
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deletions can be made therein without departing from the spirit and scope of
the
invention as defined by the following claims.
