Patent Application
20220049450
The present invention relates to geomembranes having high shear resistance for use in stabilizing piles or mounds of deposited aggregations of materials. More particularly, the present invention relates to shear resistant geomembranes that mechanically engage to overlying fabric liners for use in stabilizing layered deposit aggregations in layers, piles, or built-up mounds of granular particulate and solids materials, which layers are susceptible to plane shear failure arising from lack of force loading on the aggregation or shear load applied on the geomembranes, especially on sloped surfaces.
In this application, the following terms will be understood to have the indicated definitions:
waste sites—refers to earthen berms and to sites where waste is deposited, such as landfills, phosphogypsum stacks, environmentally impacted land, leach pads, mining spoils and environmental closures or material stockpiles that require a closure or cover system;
synthetic grass—refers to a composite of at least one geotextile (woven or nonwoven) tufted or knitted with one or more synthetic yarns or strands that has the appearance of grass;
geomembrane—refers to a structured or textured polymeric material, such as high-density polyethylene, very low-density polyethylene, linear low-density polyethylene, polyvinyl chloride, provided as an impermeable sheet for liner purposes in the waste site and land site industry.
Large area aggregations of particulate and solids materials collected together as a mass of distinct parts are found in a wide range of structural applications. These applications include landfill and waste storage sites, manufacturing products storage laydown areas and by-product waste storage and holding fields, stockpiles, power plant disposal fields, reinforced foundations for roadways, retaining wall structures, and the like. Such applications typically involve the depositing of particulate and solids materials often in sloped landsite collections or aggregations but may be substantially planar layers of such materials as well. For example, landfills and waste sites typically form sloped collections of the particulate and solids materials deposited in layers, piles, and mounds for long term storage and containment. Planar structures such as for roadways and backfill for retaining wall structures typically have stacked layers of particulate and solids materials, which layers may be of differing materials characteristics such as materials or particulate type, grade, and layer dimensions.
Each of such aggregations are susceptible to planar failures arising from shear loading. Planar failure may cause catastrophic slope failure and avalanche conditions in which the material within the aggregation suddenly releases and moves under loading. The loading may arise from the mass of the materials in the aggregation becoming released from engagement or external forces, particularly, for example, hydraulic shear forces arising from water flow across the aggregation or across a covering closure system, such as caused by rain storms or by vertical acceleration and deceleration forces, or combinations of such internal and external loading forces.
Landfills and waste sites, for example, typically remain open for a number of years for receiving waste materials, mining spoils or power plant wastes and ash, landfill trash and municipal solids and liquids wastes. Such waste sites typically have steep slopes rising from a toe or base to an upper elevated apex or peak as the additional deposits of waste materials are made over time. The elevation may typically reach several hundred feet above the toe with deposits over time of fill materials. While steep slopes allow geometrically increased storage volume, steep slopes experience significantly high shear forces. These forces occur in response to the fill materials loaded in within a vertical portion of the area allocated for the landfill and also arise from precipitation and water flow such as from rain fall on the waste site that generates high volumes of water flowing downwardly to the toe. Steep slopes often experience large and rapid run-off. Upon reaching an appropriate capacity for the particular site, the site is closed to receiving additional waste materials. Closure involves overlaying a water impermeable ground cover such as a geomembrane and a synthetic drainage system over the aggregation land site. The ground cover restricts water inflow into the collected particulate and solids materials to prevent contamination of below-grade water tables while the synthetic drainage system provides for water flow off of the cover system. Ground cover design and installation needs to consider cover stability for the long-term post-closure covering of the site.
Closure systems for landfills use geomembranes and synthetic drainage systems covered by soil (typically 18 inches to 24 inches) for developing a final grass growth on the upper soil surface. The weight or mass of the soil develops friction to resist shear loading and site slope failures. The synthetic drainage is composite layered sheet having a core geonet mesh sheet with spaced-openings and sandwiched by a fabric overlay that restricts soil from filing the openings and a fabric underlay that sits on the upper surface of the aggregation site to be closed. Ambient and environmental water such as from rain or snow percolates through the soil and flows off the covered site by the synthetic drainage system. However, in recent years, landfills have been covered with lightweight (lighter than the soil mass) geosynthetics such as synthetic grass of tufted fabric backing. While there are benefits to synthetic grass ground covers, the weight of such covers is insufficient for developing friction to avoid sliding on steep slopes (for example, up to 1:1 gradients) in high shear loading that occurs particularly during rail storms. Also, planar applications such as road ways and retaining wall backfill aggregations include stacked layers of granular materials, particulates, and soil materials. These structures provide foundations for roadway and secure retaining walls.
To increase resistance to shear loading and thus resistance to slope failure, installations typically include spaced geomembrane sheets between adjacent layers of fill materials. The interposed geomembrane provides a frictional engagement with the adjacent layers of fill materials, whereby the aggregation becomes interlinked and stabilized against planar failure.
While geomembranes providing frictional resistance to planar failure and increased aggregation stability, there are drawbacks. The frictional resistance may be insufficient to retain the fill materials under loading, typically extreme loading, such as from heavy rainfall events and flooding that in combination with internal loading creates high shear forces on the aggregation. For example, light weight synthetic grass or tufted geosynthetic sheets overlaid on steep sloped ground surfaces lack sufficient mass or weight to develop frictional surface-to-surface engagement that resists the shear forces causing sloped aggregation failure and movement.
Accordingly, there is a need in the art for an improved geomembrane having increased shear resistance for use in covering closure of materials aggregation applications using confining pressures that otherwise surface exposed layered materials cannot achieve. It is to such that the present invention is directed.
The present invention meets the need in the art by providing an improved geomembrane for use in resisting shear loading in materials aggregation applications and in reducing stabilization failures of materials aggregation applications. The improved geomembrane comprises an elongated polymeric impermeable sheet having opposing surfaces with a plurality of spaced-apart first projections extending from a first surface, which first projections mechanically engage, puncture, or pierce a respective geotextile sheet with the geomembrane in contact with adjacent fill materials within the aggregation, whereby the aggregation has increased resistant to shear failure of the aggregation of fill materials.
In another aspect, the present invention meets the need in the art by providing a ground cover system for a covering closure of a land site, comprising an elongated polymeric impermeable sheet having opposing first and second surfaces, for overlying a ground surface to be closed, with a plurality of spaced-apart first projections extending from the first surface. The first projections each tapering to a pointed apex at a distal extent. A covering for overlying the first surface of the elongated polymeric impermeable sheet, which first projections for mechanically engaging, puncturing, or piercing the covering. Upon covering installation, the aggregation has increased resistance to shear failure of the aggregation of fill materials for reducing stabilization failures of materials in aggregation land sites.
In another aspect, the present invention provides an aggregation cover system for a covering closure, comprising a liner sheet having opposing first and second surfaces, for overlying an aggregation surface to be closed and a plurality of spaced-apart spikes extending from the first surface, each said first projections tapering to a respective pointed apex at a distal extent. A tufted geosynthetic of a backing sheet tufted with yarns to define a plurality of spaced-apart tufts of synthetic grass blades extending from the backing sheet as a covering for overlying the first surface of the liner sheet, whereby said spikes for mechanically engaging the backing sheet to resist movement of the tufted geosynthetic during shear loading while the tufted geosynthetic frictionally engages the aggregation surface. The aggregation has increased resistance to shear failure of the aggregation of fill materials for reducing stabilization failures of materials in aggregation land sites.
In the geomembrane as recited above, the first projections are spaced apart to have a first density.
In the geomembrane as recited above, an alternate embodiment further comprises a plurality of spaced-apart second projections extending from a second opposing surface.
In the geomembrane as recited above, in which the second projections are spaced apart to have a second density.
The geomembrane as recited above, wherein the first projections and the second projections extend from the respective surface to an extent from about 10 mills to about 100 mills relative to the respective surface, and preferably the extent is about 40 mils.
The geomembrane as recited above, wherein the first projections are spikes, spines, or pointed pins, knobs, posts, extending members, or projections with distal pointed tips, angled tipped members, for mechanical puncture or piercing engagement with an adjacent overlying sheet material.
The geomembrane as recited above, wherein the second projections are spikes, spines, or pointed pins, knobs, posts, extending members, or projections with distal pointed tips, angled tipped members, for further mechanical puncture or piercing engagement with exposed surface layer of the collected particulate and solids materials.
The geomembrane as recited above, wherein an extent of the respective first projections is of a first length and the extent of the respective second projections is of a second length, the first length different from the second length.
The geomembrane as recited above, wherein at least the first projections have an axis oriented on a perpendicular relative to the surface of the geomembrane.
The geomembrane as recited above, wherein at least the first projections have an axis oriented at an oblique angle relative to a perpendicular to the surface.
The geomembrane as recited above, wherein the oblique angle of the axis of the first projections is from about 1 degree to about 45 degrees, preferably from about 5 degrees to about 20 degrees, and more preferably from about 10 degrees to about 15 degrees.
The geomembrane as recited above, wherein the geomembrane has an interface shear strength to resist shear load.
Objects, advantages, and features of the improved geomembrane and cover system will become apparent upon a reading of the detailed description in conjunction with the drawings illustrating various embodiments of the improved geomembrane.
With reference to the drawings, in which like parts have like identifiers,
With reference to
The geomembrane 20 is preferably made of very low density polyethylene, linear low density polyethylene (LLDPE), high density polyethylene (HDPE), or polyvinyl chloride.
The illustrated embodiments provide an interface resistance to slippage of aggregations of particulate and solids materials such as slippage occurring between layers of the aggregation or slippage of sloped surfaces. In a covering application discussed below in
As illustrated in
As noted above, the geomembrane 20 may be used for providing resistance to high shear forces that may arise in materials aggregation applications, such as in mounded or layered infill aggregation applications including landfill and waste site operations including as a site liner or as a component of a covering system for closure of a landfill. In such application involving sloped land for closing coverage, the geomembrane 20 is preferably oriented with the pointed apex 29 of the spikes 26 facing uphill in opposition to a force inducing slippage downwardly along sloped land but may be oriented facing downhill or transverse on sloped surfaces. In other applications, the geomembrane 20 may be installed as a stabilizing layer in a layered backfill for retaining walls or as a foundational layer in a roadway application.
The geotextile sheet 72 comprises a woven or non-woven textile. In the illustrated embodiment, the geotextile sheet 72 is non-woven but may be woven with warp and waft yarns. The geotextile sheet 72 has a weight basis or mass of between about 3 ounces per square yard to about 16 ounces per square yard, more preferably about 6 ounces per square yard to about 9 ounces per square yard, and preferably of about 6 to 8 ounces per square yard.
The backing sheet 124 may be a woven or non-woven textile, and may comprise one or a plurality of separate sheets tufted together. The backing sheet 124 may have weight basis or mass of between about 6 ounces per square yard to about 24 ounces per square yard. The tufting yarns interweave through the backing to define spaced-apart rows of the tufts 125 that extend from the geosynthetic 20 as the grass-like blades 126. The tufts 125 tuft on spacing in a range from about ¼ inch to 1 inch, preferably ½ inch. The blades 126 extend from the backing sheet 124 about ½ inch to about 4 inches, and more preferably from about 1 inch to about 1 and ½ inches. The adjacent blades 126 define the interstices 128. The interstices 128 receive the distributed granular infill 130 selectively to a fill plane (preferably less than and no more than a greatest extent defined by about a distal extent of the blades 126). The backing sheet 124 forms of a polymer material that resists exposure to sunlight that generates heat rise in the geosynthetic 20 and that resists ultraviolet (UV) radiation in the sunlight, which degrades the backing sheet and the tufted blades. The polymer yarns further should not become brittle when subjected to low temperatures. The color selection of the yarns for the backing sheet 124 are preferably black and/or gray yarns. The color selection for the tufting yarns are green or brown, to simulate tufts 126 of grasses. The tufts may be tufted in combinations for closer simulation of the area to be covered, for example using a respective proportion of a first, second, or more, color yarns. Further, the polymeric material for the yarns that are woven to form the backing sheet or the polymers spun bond for a non-woven backing sheet, include UV resistant additives such as HALS and carbon black. The polymers are selected to provide high shear strength resistance for the geotextile 20. The backing sheet has strong tensile strength, in a range of about 1,000 pounds per foot to about 4,000 pounds per foot.
The cover system may gainfully use the granular infill 130 received within the interstices 128 between the tufts 125. The infill 130 is a granular material cooperating with the extending blades 126 of the tufts 24 to shadow the backing sheet 22 and further enhances the friction developed with the tufted geosynthetic covering. The infill 130 fills onto the backing sheet 124 and within the interstices 128 therefrom preferably to about a second extent that is generally less than the fill plane of the geosynthetic. The infill 130 cooperates with the blades 126 to shadow the backing sheet 124 from UV exposure and degradation. The infill 38 may be a sand material, and further particularly may comprise a fire retardant additive or product independent of a sand carrier mixture, such as a non-halogenated magnesium hydroxide powder, silicates including potassium silicate, calcium silicate, and sodium silicate, or other in situ fire suppression or resistant material.
The foregoing discloses an improved geomembrane for use in resisting shear loading in materials aggregation applications and in reducing stabilization failures of materials aggregation applications, comprising an elongated polymeric impermeable sheet having opposing surfaces with a plurality of spaced-apart first projections extending from a first surface, which projections for mechanically engaging a synthetic drainage overlaid by a respective geotextile sheet and in contact with adjacent fill materials within the aggregation, whereby the aggregation has increased resistance to shear failure of the aggregation of fill materials. While the invention has been described with particular reference to various embodiments, variations and modifications can be made without departing from the spirit and scope of the invention recited in the appended claims.
| Number | Date | Country | |
|---|---|---|---|
| 63066155 | Aug 2020 | US |
