Patent Description:
This invention relates generally to ground covers and methods used in covering large areas of ground for controlling environmental water infiltration into covered ground and/or wind erosion of the ground surface. More particularly, the present invention relates to ground covers that regulate flow of environmental water covering large areas of ground through the ground cover for abated infiltration through the ground cover into a ground water table below and methods for abated infiltration of environmental water for replenishing the ground water table. The invention further provides for control of dust scattering in response to wind forces on a ground surface.

In this application, the following terms will be understood to have the indicated definitions.

Coverings have been used to overlay large areas of ground including landfills, waste sites, manufacturing laydown sites, and stockpiles. Some tufted geosynthetic ground covers are used to shed environmental water and prevent the water from infiltration through the site and being absorbed into the soil which may allow contaminates into the soil. Other sites such as in arid regions experience infrequent, but short duration rain storms. Often the rain storms are intense with significant volume of rainfall water. A common problem with such rainfall in arid regions is the rapid accumulation of large amounts of water that results in large volumes of water moving swiftly and rapidly across the ground particularly across the slopes and into gullies, stream beds, or ravines often present in such areas. The large volume flow and velocity of environmental water that may occur from sudden and heavy rainfall poses a danger to persons in low areas and areas remotely downstream from the source rainfall, and may cause damage to the ground as the fast moving water moves across the ground. Further the fast moving water fails to substantially infiltrate the ground and replenish the local ground water table, but rather a significant volume of the available environmental water often moves rapidly away through stream beds and to locations remotely downstream. Much of the available environmental water thus fails to enter the local ground water table.

Also, arid regions typically have insufficient plants, grasses, bushes, and trees, for resisting erosion by wind dispersion of soils and dust particles. Such wind-blown materials erode ground surfaces and cause dusty air conditions.

While water-shedding ground covers accordingly allow clean water to flow-off of the covered site and also provide control of wind-caused erosion, there are reasons to allow infiltration of environmental water for absorption into the underlying soil. However, the tufted geosynthetic types of ground covers are expensive to manufacture, install, and maintain.

Accordingly, it is seen that a need remains for a ground cover which may be formed to slow or abate environmental water flow across a ground for moderated flow allowing absorption of the water into the local source soil and ground water table below and control dusts, yet is easy and cost effective to manufacture, install, and maintain. It is to the provision of such that the present invention is directed. Reference is made to the documents <CIT> and <CIT> which have been cited as exemplary of the state of the art.

The present invention meets the need in the art for a stabilized water control ground cover providing environmental water flow abatement and wind erosion control over land surfaces for local source infiltration into ground water table. In one aspect, the present invention meets the need in the art by providing for stabilized water flow control ground cover of a non-woven mat of randomly oriented polymeric fibers defining interstitial gaps and the mat having respective extended longitudinal and transverse axis and a thickness that is less than an significant minority of the transverse axis. The interstitial gaps define a plurality of interference pathways for non-direct water flow through the mat. Spaced-apart tufts are tufted with a polymeric yarn to form one or more synthetic blades in each tuft extending from the upper surface of the mat to a blade extent to simulate a field of grass. The tufts are connected by tuft bridges on an opposing side of the mat. A stabilization layer on a bottom side and proximate interior portion of the non-woven mat comprises a plurality of heat-bonded contacting engagements of portions of at least some of the fibers and the tuft bridges, whereby the mat is stiffened. The mat being disposed on a ground surface moderates a rate of flow of environmental water for increased seepage of the environmental water through the ground surface and resists rapid lateral flow thereof across the ground surface.

In yet another aspect, the present invention provides a method of abating environmental water flow off of a ground surface, comprising the steps of:.

The present invention provides a new and improved stabilized water flow control ground cover for use in conjunction with large areas of land.

Objects, advantages, and features of the present invention will become apparent upon a reading of the following detailed description in conjunction with the drawings and the appended claims.

With reference next to the drawings, there is shown in <FIG> in perspective bottom view a ground cover <NUM> embodying principles of the invention in a preferred form. The ground cover <NUM> has a non-woven textile layer or mat <NUM> of randomly oriented polymeric fibers <NUM> (sometimes referenced herein as thermoplastic fibers), which may be made of polyethylene, polypropylene, polyolefin, or other non-woven textile fiber, spun-bond or lofted/air laid as a non-woven textile. The mat <NUM> has respective extended longitudinal and transverse axis and a thickness that is less than an significant minority of the transverse axis. That is, the thickness is less than the width. The mat <NUM> has an upper side <NUM> and opposing bottom side <NUM>. The fibers <NUM> define a plurality of interstitial gaps or spaces <NUM>. The spaces <NUM> formed by the fibers <NUM> define interference pathways for flow of environmental water through the mat <NUM>. The fibers <NUM> interfere with direct linear flow, and rather, the environmental water flows in non-linear, not-direct channels downwardly and laterally through and the mat.

The mat <NUM> features permittivity that allows abated water flow therethrough for infiltration of environmental water such as from a rain storm <NUM> local to a source occurrence for replenishing a ground water table. The term "permittivity" refers to a cross-plane permeability of water flow perpendicular to a plane of the mat <NUM> divided by the thickness of the textile under a normal load. See Designing with Geosynthetics by Dr. Robert Koerner (<NUM>).

Presently, it is believed that mats <NUM> useful with the present invention are made according to the following properties:
Fiber denier (grams per <NUM> meters) in a range from about <NUM> denier to about <NUM>,<NUM> denier.

An Apparent Opening Size (AOS): ASTM D4751 for AOS in a range from US Sieve size of <NUM> (<NUM> microns) to US Sieve size of <NUM> (<NUM> microns).

The resulting mat has a thickness in a range from about <NUM> inches (<NUM>) to <NUM> inches (<NUM>).

The mass per unit area of the mat <NUM>: <NUM> grams per square metre (<NUM> oz/ square yd (<NUM> grams/yd<NUM>)) to <NUM> grams per square metre (<NUM> oz/square yd (<NUM>,<NUM> grams/yd<NUM>)).

With continuing reference to <FIG>, the ground cover <NUM> also includes an array or mass of synthetic blades <NUM> incorporated into and extending from the upper side of the mat <NUM> as a plurality of spaced-apart tufts <NUM>. The ground cover <NUM> thereby comprises a configured embodiment of a tufted geosynthetic enabled for abated water flow through the mat <NUM> that contributes to infiltration of environmental water through the mat and absorption of the water in the soil for replenishment of a ground water table. The synthetic blades <NUM> may be formed by any conventional means such as tufting of yarns through the non-woven mat or weaving tufts or lines of tufts of synthetic fibers or yarn into the non-woven mat. The tufting involves knitting the yarns through the mat <NUM> with running tuft bridges <NUM> on the bottom side <NUM> as best illustrated in <FIG>. The tufting thereby defines the adjacent tufts <NUM> in a field of spaced-apart tufts.

As discussed below, the spaces <NUM> during operational use of the ground cover <NUM> become occupied by environmental water and the combination of the randomly disposed fibers <NUM>, the resulting spaces <NUM>, and the tufts <NUM>, cooperatively abate or moderate the flow of the environmental water through the mat <NUM> into a ground water table <NUM> below the ground surface <NUM> as shown in <FIG>.

Preferably, the synthetic strands <NUM> are slender elongated elements. As used herein, "slender" indicates a length that is much greater than its transverse dimension(s). Examples of slender elongate elements contemplated as encompassed by the present invention or in conjunction therewith are structures that resemble blades of grass, rods, filaments, tufts, follicle-like elements, fibers, narrow cone-shaped elements, etc. The synthetic strands <NUM> extend upwardly from the base mat <NUM> as a field of such strands. Such can simulate a field of grass, pine straw or similar. The synthetic strands <NUM> extend upwardly a length of about <NUM> (<NUM>/<NUM> inch) to about <NUM> (<NUM> inches).

Preferably, the chemical composition of the synthetic grass blades <NUM> should be selected to be heat-resistant and UV-resistant (to withstand exposure to sunlight, which generates heat in the blades and contains ultraviolet rays), and fire-retardant. Furthermore, the polymer yarns of the blades <NUM> should not become brittle when subjected to low temperatures. The selected synthetic grass color and texture should be aesthetically pleasing. While various other materials may work well for the grass blades, it is presently believed that polyethylene fibers work best.

Optionally, the synthetic grass blades <NUM> are tufted to have a density of between about <NUM> grams per square metre (<NUM> ounces/square yard) and about <NUM> grams per square metre (<NUM> ounces/square yard). Preferably, the synthetic grass blades have a density of between about <NUM> and <NUM> grams per square metre (<NUM> and <NUM> ounces/square yard). The tufting is fairly homogeneous. In general, a "loop" is inserted at a gauge spacing to achieve the desired density. Each loop shows as two blades of grass at each tufted location. Preferably, the synthetic grass blades <NUM> have a thickness of at least about <NUM> microns.

The bottom side <NUM> of the mat <NUM> in the illustrated embodiment includes a stabilization layer generally <NUM> in a side edge portion of the mat as illustrated in Fig. l. The stabilization layer <NUM> includes the bottom side <NUM> (and its open pore surface formed by the exterior portions of the fibers <NUM>) and a proximate interior portion of the mat <NUM>. The bottom side and proximate interior portions forming the stabilization layer <NUM> comprises a minor dimension of the thickness of the mat <NUM>. In the illustrated embodiment, the stabilization layer <NUM> forms by contacting engagements <NUM> of portions of at least some of the fibers <NUM> and of portions of the fibers <NUM> and the tuft bridges <NUM> as tuft bind connections. The stabilization layer <NUM> stiffens the mat <NUM> with a bottom or lower portion of the mat <NUM> proximate the ground surface <NUM> providing a structural stabilization.

In the illustrated embodiment, the fibers <NUM> and fibers <NUM> and tuft bridges <NUM> heat bond together, or tuft bind, to establish the stabilization layer <NUM>. The structure of the stabilization layer <NUM> forms by heat-bonding respective overlapping fibers <NUM> in the mat <NUM> at points of contact <NUM>, and by heat-bonding of the fibers <NUM> that are in contact (<NUM>) with the tuft bridges <NUM> that extend across portions of the bottom side of the mat <NUM>. This is accomplished with a heat bond/calendar process in which the open lofted fabric of the air-laid fibers are heated and calendared to reduce or take downwardly the lofting of the mat. For example, a heated roller heats the fibers <NUM> of the bottom side <NUM> and proximate portion of the mat <NUM> and the tuft bridges <NUM> and calendars the heated fibers and tufted bridges while leaving the interstitial spaces <NUM> porously open for environmental water flow. The bottom side and proximate portion of the mat <NUM> thereby form the joined integral stabilizing structure <NUM> of the bottom ground-contacting portion of the mat <NUM>. Other bonding such as adhesive, spray-upon polypropylene, polyethylene or polymerizing vinyl chloride (PVC), or the like, may contactingly engage the respective fibers and tuft bridges, while leaving generally open the pores defined by the fibers for permeability of the mat. The stabilization portion <NUM> retains a base of the tufts <NUM> secured to the bottom side <NUM> and resists pull-out of the tufts and separation of the tufts from the mat <NUM> during long-term usage of the ground cover in exposure to wind, environmental water, and other weather related events, for ground cover longevity.

In reference to <FIG> and <FIG>, the ground cover <NUM> is positioned for use over or upon a tract of land wherein it is desired to have environmental water <NUM> such as rainfall, snow melt, or storm water runoff seep or infiltrate into the soil. As the water falls upon the ground cover <NUM>, the water seeps, percolates or travels generally <NUM>, <NUM> through the mat <NUM>. The spaced fibers <NUM> and interstitial gaps or spaces <NUM> cooperatively abate or moderate the flow of the environmental water through the mat <NUM>. While the environmental water flows generally downwardly <NUM> through the air-laid mat <NUM>, the tufts <NUM> of the grass blades <NUM> abate the rapid lateral flow to a slower flow <NUM> across the ground cover <NUM>. The tuft bind of the fibers <NUM> and the tuft bridges <NUM> creates drag on the waterflow while the tufts remain secured in the stabilization portion <NUM>. The non-woven mat <NUM> thereby slows down the movement and the flow rate or rate of travel of the water through the mat (downwardly and laterally). This slows the flow of environmental water across, through and over the ground cover <NUM>.

As a result, the environmental water has an increased dwell time relative to the ground cover <NUM>. The invention thereby increases the capability of the environmental water on the ground cover to pass from the non-woven mat <NUM> outwardly of the stabilization portion <NUM> and into the underlying soil for replenishment of the ground water table <NUM>. The ground cover <NUM> thereby provides hydraulic energy dissipation for the overland flow of the water that does not infiltrate the ground. The energy dissipation results from the slowing of the environmental water which promotes infiltration and seepage. Slowing of the water flow further reduces the erosive forces (energy) below the ground cover and thereby reduces the potential for erosion rill or washout that, with water flow carrying away sediment, creates a recess below the ground cover. A recess formed below the ground cover results in a trampoline in that portion of the ground cover and the covered ground, and may lead to potential unstable ground particularly on slopes. The present invention thereby provides erosion dissipation across a large project site. Additionally, the nonwoven mat <NUM> works very well in disturbing wind flow over the ground cover <NUM> and reducing the uplift forces upon the base layer <NUM>.

The sizing of the pores or interstices <NUM> should be selected to allow the flow of water through the mat <NUM> and the stabilizing portion <NUM> by being large enough so as not to prevent the flow through the mat as a result of the water tension within the pores.

The synthetic grass ground cover <NUM> accordingly aids in abated slowing of the flow of water from environmental water such as rainfall while providing a pleasant appearance to the ground cover and providing a surface that creates turbulent air flow across the upper side which air flow applies a bearingly normal force against the mat <NUM> for resisting wind uplift.

In another aspect, the present invention provides a method for abated flow of environmental water flow over a ground surface for infiltration into the ground water table local to an environmental water occurrence particularly applicable for arid regions. The method provides the cover <NUM> comprising the mat <NUM> of air-laid fibers <NUM> tufted with yarn as the field of tufts <NUM> having the grass-like blades <NUM> with a stabilized portion <NUM> of the mat of joined fibers <NUM> and tuft bridges <NUM> in the bottom side of the mat <NUM>, disposing the cover <NUM> over a large area of ground, for exposing to environmental water occurrences, in which the mat <NUM> abates the flow of environmental water to facilitate flow passage outwardly of the bottom side for infiltration into the local ground water table.

Further, the ground cover <NUM> in accordance with the invention suitably provides dust control or abatement features in addition to water flow control. The mat <NUM> formed of the air-laid fibers <NUM> define openings and passages generally <NUM> through the mat, with a thickness of about <NUM>/<NUM> inch to about <NUM> inches. The mat <NUM> thereby provides constricted non-linear pores <NUM> or passageways as defined by the randomly laid fibers <NUM> relative to a perpendicular plane between the top side <NUM> and the bottom side <NUM>. The fibers and the constricted non-linear pores <NUM> restrict passage of dust from the ground surface <NUM> in response to wind flow across the cover <NUM>. It is contemplated that the textured upper side <NUM> creates a turbulent air flow proximate the cover <NUM> which air flow partially passes in the openings or passageways <NUM> in the mat <NUM>, and thereby the fibers <NUM>, the openings <NUM> through the mat <NUM>, and the tufts <NUM>, cooperatively resist outflow of dust from the ground surface through the mat <NUM>. Further, as discussed above, the passages and pores defining the permittivity of the mat <NUM> abates environmental water flowing through the mat.

<FIG> illustrates in perspective view an alternate embodiment ground cover <NUM> overlaid on a ground surface <NUM> for dust control yet also providing water flow control, and resisting uplift from wind because of the weight of the mat <NUM> itself, or alternatively also optionally secured with staples <NUM> or similar ground securing fasteners. The ground cover <NUM> forms of the air-laid fibers <NUM>. This alternate embodiment is particularly preferred for temporary application in a method of controlling uplift of surface materials as wind-carried dust within the air above a ground surface, deploying the mat <NUM> as a dust control ground cover overlying a ground surface <NUM> having exposed dust <NUM> but provided without the tufted yarns for tufts <NUM> of simulated grass and without the stabilized structure <NUM>. The term "temporary application" refers to a period of time less than that specified conventionally for tufted geosynthetic cover systems for site closure purposes pursuant to regulatory guidelines and rules concerning closures for landfills, waste sites, and environmental sites requiring a geomembrane that restricts water infiltration and secured from wind uplift. The term "temporary application" in an illustrative embodiment refers to a period of up to and about <NUM> years, although the method of dust control matting may involve a longer period.

The ground cover <NUM> thereby provides an inexpensive, light-weight porous water flow control mat for covering large areas of wind-subject ground <NUM> while resisting uplift of dust <NUM> from the ground surface. Upon exposure to wind, the non-linear top side <NUM> creates a turbulent air flow generally <NUM> proximate <NUM> the cover <NUM> which air flow partially passes in the openings or passageways <NUM> in the mat <NUM>, and thereby the fibers <NUM> and the openings <NUM> through the mat <NUM>, cooperatively resist outflow of dust from the ground surface through the mat <NUM>. The present invention accordingly provides a method for dust control of ground surfaces by seating the ground cover <NUM> as a blanket of the mat <NUM> in contact with the ground surface <NUM>, and alternatively securing the blanket with anchors, U-shaped staples <NUM>, pins, or other such mechanical connectors, to the ground, and alternatively, with the mass of the mat <NUM> and/or the turbulent proximate air flow, cooperatively resisting wind upload forces, and restricting flow of dust from the ground into the air by wind across the covered area. The blanket may comprise multiple side-by-side partially overlapping and edge joined lengths of the mat <NUM> (for example, mats <NUM> having a length of <NUM> feet supplied in rolls for unrolling installation on the ground surface and adjacent overlapped edges heat-bonded together to form the area wide blanket). The staples <NUM> provide lateral stabilization of the mat <NUM>. The staples <NUM> may also optionally be gainfully employed with the ground cover <NUM> illustrated in <FIG>.

Claim 1:
A stabilized water flow control ground cover (<NUM>), comprising:
a non-woven mat (<NUM>) of randomly oriented polymeric fibers (<NUM>) defining interstitial gaps (<NUM>), the mat having respective extended longitudinal and transverse axis and a thickness that is less than a significant minority of the transverse axis,
the interstitial gaps (<NUM>) defining a plurality of interference pathways for non-direct water flow therethrough;
a plurality of spaced-apart tufts (<NUM>) tufted with a polymeric yarn to form one or more synthetic blades (<NUM>) in each tuft extending from the upper surface (<NUM>) of the mat (<NUM>) to a blade extent to simulate a field of grass and connected by tuft bridges (<NUM>) on an opposing side of the mat; and
a stabilization layer (<NUM>) on a bottom side and proximate interior portion of the non-woven mat (<NUM>), said stabilization layer comprises a plurality of heat-bonded contacting engagements (<NUM>) of portions of at least some of the fibers (<NUM>) and the tuft bridges (<NUM>), whereby the mat is stiffened,
whereby the mat being disposed on a ground surface moderates a rate of flow of environmental water into the stabilization layer (<NUM>) and through the mat (<NUM>) for increased permittivity seepage of the environmental water through the ground surface and resists rapid lateral flow thereof across the ground surface.