Abstract:
Numerous permutations of high-friction void-maintaining membrane laminates are provided. Laminates of the invention are particularly useful for providing high performance drainage within installations having a high slope component. Void-maintaining laminates of the invention comprise flow zones of void spaces which are typically interconnected, and constructed and arranged so that the flow zones provide desirable paths for the egress of drainage fluids. The laminates advantageously include also high-friction zones which are typically interspersed between the flow zones such that the laminates are useful to provide drainage in installations of high incline angles. Laminates of the present invention provide both desired resistance to movement, that is, increased shear resistance, and flow capacity increases of from 25-100% when compared with conventional laminates.

Description:
RELATED APPLICATIONS  
       [0001]     Applicant claims priority to U.S. Provisional Application Ser. No. 60/460,784, filed Apr. 7, 2003, and to U.S. Provisional Application Ser. No. 60/460,147, filed Apr. 4, 2003. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to geonets and geocomposite drainage structures that are constructed and arranged to possess high resistance to unwanted movement while in place. The high-friction elements or portions of the laminates, friction zones, anchor zones and fluid transmission zones (“flow zones”) of structures of the invention advantageously can be constructed and arranged such that desired fluid flow paths or patterns are provided through the fluid transmission zones of the laminates while portions of the laminate are dedicated to maintaining a high resistance to movement of the laminate with respect to adjacent membranes and with respect to the soils in which the laminates are positioned. Structures of the invention are therefore particularly useful for high capacity drainage in sloped installations.  
       BACKGROUND OF THE INVENTION  
       [0003]     Water is the principal cause of distress in many types of structures. Geotechnical engineers and others skilled in the art specify or purchase sand, stone, or gravel as a means of conveying fluids to collection pipes. For some time, conventional geonet and geocomposites (hereinafter geocomposites) have been used to complement or replace natural earthen materials such as stone, gravel and clay. Geonets are often used as core elements within geocomposite structures to provide voids disposed for conveying fluids above or between geofabrics or geomembranes and in a desired direction, for example, away from a building or roadway.  
         [0004]     In such drainage geocomposites, the core element is typically encased or laminated between one or more permeable woven or non-woven fabrics. Such fabrics are commonly known in the art as geotextiles. Core elements, such as geonets, are typically manufactured in large sheet-like forms having a desired thickness. A core element having a geotextile bonded to one of its sheet-like, or approximately planar, surfaces is commonly known as a single-sided geocomposite system. A core element having geotextiles bonded to both of its sheet-like surfaces is commonly known as a double-sided geocomposite system. The relative position of the geotextiles with respect to the core element, that is the adjacency of the layers, is typically effected and maintained by means of thermal or adhesive processes that mechanically or chemically bond the geotextiles to one or both surfaces of the core element.  
         [0005]     Thus, in single-sided conventional drainage laminate structures, a geotextile is typically attached to all of the upper surface area of the core element to yield a single sided geocomposite. Similarly, in conventional double-sided drainage laminate structures, one geotextile is attached to all of the upper surface area of the core element and a second geotextile is attached to all of the lower surface area of the core element to yield a double-sided geocomposite. Typically, a single-sided or double-sided geocomposite laminate is installed on top of a geo-membrane, that is, a layer that is impermeable to the water and other fluids that the installation is intended to drain. Also typically, the geocomposite is not attached to the membrane. Thus, in sloped applications, installation designs depend on the frictional characteristics of the interface between the membrane and the adjacent geocomposite layer. In conventional methods of constructing sloped installations, the friction between the membrane and the adjacent geotextile of a geocomposite is increased, for example, by providing the membrane with textured or roughened surfaces which interact with the adjacent geotextile to inhibit movement.  
         [0006]     A significant disadvantage of conventional types of single-sided geocomposites relates to the fact that they can only be used in limited manners due to the lack of friction between their lower surfaces and geomembranes. Moreover, those skilled in the relevant art are also less prone to use conventional single-sided geocomposites because they possess less puncture resistance then double-sided systems. Conventional double-sided systems are similarly problematic. Indeed, a significant disadvantage of double-sided geocomposite systems is that their low-friction surfaces act as energy dissipaters and as flow impeders, thereby undercutting the very reason to utilize such conventiuonal double-sided the products. Nonetheless, because they are the best product currently available on the market, at times double sided geocomposites are desirable when the slope angle of an installation is greater then  8 % and friction between the separate geosynthetics is essential for reasonable slope stability. However, although the lower layer of geotextile increases friction between the laminate and the underlying membrane, it also serves to reduce flow by an order of magnitude. This flow reduction is due largely to intrusion of the lower geotextile layer into the flow channels of the core element.  
         [0007]     By providing multiple zones within laminated structures of the invention, embodiments of the present invention advantageously combine the frictional advantages of double-sided geocomposites with the high-capacity fluid flow transmissivity of single-sided geocomposites while yielding a weighted average friction angle for the entire width of a particular laminate that is suitable to maintain slope integrity.  
         [0008]     Until the present invention, there has never been a laminate comprising a geonet core having an upper layer, such as a geotextile, laminated virtually over the geonet&#39;s entire upper surface in combination with, on less than all, or only part of the geonet&#39;s lower surface, a lower layer such as a geotextile or high-friction scrim, laminated on less than all of the geonet&#39;s lower surface to thereby make the core element available for contacting something other than a laminate lower layer. In some embodiments of the invention, the lower layer is provided, for example, in alternating parallel or non-parallel strips, uniform or random shapes, or any combination that is constructed and arranged to form both “friction zones” and “flow zones.” With the myriad of configurations possible within the scope and spirit of the invention, geocomposite laminates of the invention provide both desired drainage flow characteristics and an increase in resistance to unwanted movement. In many combinations according to the invention, this is accomplished at a lower material cost.  
         [0009]     In one set of embodiments, the present invention thus combines the advantageous characteristics of both single-sided and double-sided geocomposites. For example, as shown in  FIG. 3 , wide strips of areas of single-sided and double-sided geocomposites are combined in parallel alternations to provide double-sided friction zones and single-sided flow zones within one continuous roll of finished product. This combination of friction zones and flow zones offers both superior transmissivity performance and superior frictional characteristics when compared to either a conventional single sided or double-sided geocomposite system.  
         [0010]     The present invention provides significant advantages over conventional geocomposite systems used in applications of significant slope. Typically, the degree of slope angle in installations employing conventional single sided geonets is limited to slopes of no greater then 8%. Conventional double-sided geocomposites, which rely on a lower layer of geocomposite adjacent all of the core element&#39;s lower surface to increase friction between the laminate and an underlying membrane, are also limited with respect to the slope angle and drainage capacity because of cover soil permeability and slope length factors which make them more prone to fail when placed at significant slope angles.  
       SUMMARY OF THE INVENTION  
       [0011]     It is therefore an object of the invention to provide laminates which possess superior characteristics with respect to drainage performance in sloped installations.  
         [0012]     It is a similar object of the invention to provide laminates having preferred paths or flow zones for the egress of fluids such as aqueous-based fluids and gases.  
         [0013]     It is a further object of the invention to provide methods for designing and adapting laminates of the invention to specific uses and installations. In accordance with this and other objects, a laminate having void-maintaining regions and high friction regions is provided, the laminate comprising a sheet-like upper layer, the upper layer having two primary surfaces, an upper layer lower surface and an upper layer upper surface. The laminate also has a sheet-like lower layer, the lower layer having a lower layer lower surface and a lower layer upper surface, and a void-maintaining core, the core having an upper core surface and a lower core surface. In numerous embodiments of the invention, the core is interposed between less than all of the area of the lower layer upper surface and the area of the upper layer lower surface to form at least one flow zone. Alternatively stated, the void-maintaining core element is not interposed between all of the area of the respective surfaces of the upper and lower layers but only between desired portions, areas or patterns of the upper and lower layers to form one, or a plurality, or numerous, interconnected voids or flow zones between the upper and lower layers. In accordance with additional objects of the invention, the lower layer is provided on less than all, or only portions of, the lower layer lower surface of the void-maintaining core to thus form exposed core sections such that the exposed core sections function as friction zones that can be positioned in contact with materials placed adjacent to the lower core surface. Such materials can be, for example, a base layer such as an additional layer of permeable or impermeable membranes, grids or geotextiles or may simply be the dirt, gravel or landfill materials over which, or among which, the laminate is placed. Thus, the exposed layers of the core element serve to anchor the laminate into an installation in which it is placed.  
         [0014]     The upper layer, lower layer, void-maintaining core, and base layer of laminates according to the invention may comprise one or more of membranes, grids and geotextiles. The upper layer, lower layer and base layers of laminates according to the invention may be permeable or impermeable to fluids depending upon the desired characteristics of an installation. One or both of the upper layer and the lower layer may be provided discontinuously on the void-maintaining core. In some embodiment of laminates of the invention, one or more of the layers are attached to adjacent layers to further increase shear strength and ease of installation. The degree of attachment of any two adjacent layers can be of any level so long as the desired performance characteristics are achieved. Attachment can be effected by, for example, with respect to the effective surface area of the core surface, that is, with respect to the core area that is available in a plane-like volume defined by the tips of compression elements or by the available area defined by strands of a geogrid core element. As is known in the field, attachment can be effected by one or more of adhesives, flame welding, melt bonding, laser welding, ultrasound welding, hook-and-loop protrusions, stitching or by any other means which provides the desired attachment strength. Thus, in some preferred embodiments, the upper, lower or base layers are attached to an adjacent layer by at least 10% of the effective surface area of the respective layers, or by at least 20% of the effective surface area of the respective layers, or by at least 30% of the effective surface area of the respective layers, or by at least 40% of the effective surface area of the respective layers.  
         [0015]     In some preferred embodiments, the void-maintaining core may comprise high-friction compounds. In some preferred embodiments, the void-maintaining core may comprise one or more of biplanar geogrids, tri-planar geogrids, cuspidations, and compression elements wherein the compression elements are provided in one or more shapes, and the shapes are selected from one or more of spikes, cones, hollow cones, spindles, convolutions, bubbles, circular cylinders, ovoid cylinders, hollow cylinders, flat-faceted pyramids, arcuate-faceted pyramids, volcano-shaped columns, mushroom-shaped columns, tubes, sphere-topped shafts, and peduncles. Depending upon the topology of an installation into which they are placed, laminates of the invention may comprise one or a plurality of flow zones, the flow zones may be provided in regular or irregular patterns, and the flow zones may be interconnected in any way desired in order to provide specific drainage capabilities. In some preferred embodiments, a laminate of the invention comprises a plurality of flow zones wherein a at least some of the flow zones interconnect with one another to provide desired drainage capacities.  
         [0016]     The respective layers and void-maintaining core of laminates of the invention may be formed of any materials that provide the desired engineering and performance characteristics. Particularly preferred materials include one or more thermoplastics such as those selected from the group consisting of polyethylene, high density polyethylene (“HDPE”), polypropylene, glass-filled plastics, and ABS.  
         [0017]     In accordance with additional objects of the invention, laminates can be provided wherein the lower layer, upper layer and core are constructed and arranged such that the overall capacity, or the capacity of the at least one flow zone of the laminate has a transmissivity of at least 10 −3 M 2  sec −1  of aqueous liquid at a normal load of at least 100 PSF (pounds/ft 2 ) sustainable for at least 100 hours when tested in accordance with ASTM 4716, or at least 1,000 PSF (pounds/ft 2 ) sustainable for at least 100 hours when tested in accordance with ASTM 4716, or at least 10 −3  M 2  sec −1  of aqueous liquid at a normal load of at least 10,000 PSF (pounds/ft 2 ) sustainable for at least 100 hours when tested in accordance with ASTM 4716, or at least 15,000 PSF (pounds/ft 2 ) sustainable for at least 100 hours when tested in accordance with ASTM 4716.  
         [0018]     As an additional advantage, laminates of the invention may further comprise a base layer, wherein the base layer is provided on or adjacent to the lower layer lower surface and on or adjacent to the exposed sections of the core. The base layer may be permeable or impermeable to fluids, and may comprise one or more of membranes, grids and geotextiles. Preferably, one or more of the base layer, the upper layer, the lower layer and the core are formed of one or more thermoplastics selected from the group consisting of polyethylene, high density polyethylene (“HDPE”), polypropylene, glass-filled plastics, and ABS. As with other layers of laminates of the invention, the base layer may be attached to at least a portion of the effective surface area of the lower layer surface and the attachment is effected by one or more of adhesives, flame welding, melt bonding, laser welding, ultrasound welding, and hook-and-loop protrusions.  
         [0019]     Capacities of a laminate of the invention comprising a base layer may be designed and provided such that the overall capacity, or the capacity of the at least one flow zone of the laminate has a transmissivity of at least 10 −3 M 2  sec −1  of aqueous liquid at a normal load of at least 100 PSF (pounds/ft 2 ) sustainable for at least 100 hours when tested in accordance with ASTM 4716, or at least 1,000 PSF (pounds/ft 2 ) sustainable for at least 100 hours when tested in accordance with ASTM 4716, or at least 10 −3  M 2  sec −1  of aqueous liquid at a normal load of at least 10,000 PSF (pounds/f 2 ) sustainable for at least 100 hours when tested in accordance with ASTM 4716, or at least 15,000 PSF (pounds/ft 2 ) sustainable for at least 100 hours when tested in accordance with ASTM 4716.  
         [0020]     In accordance with still other objects of the invention, methods are provided for providing high-friction void-maintaining laminates to meet the desired drainage specifications of one or more particular slopes. A preferred method of the invention comprises the acts or steps of A) determining the desired drainage specifications of the slope, and B) providing a laminate having void-maintaining regions and high friction regions, the laminate comprising a sheet-like upper layer, the upper layer having an upper layer lower surface and an upper layer upper surface, a sheet-like lower layer, the lower layer having a lower layer lower surface and a lower layer upper surface, and a void-maintaining core, the core having an upper core surface and a lower core surface, wherein the core is interposed between portions of the lower layer upper surface and the upper layer lower surface to form at least one flow zone, wherein the lower layer is provided on portions of the lower layer lower surface of the void-maintaining core to thus form exposed core sections such that the exposed core sections function as friction zones that can be positioned in contact with materials placed adjacent to the lower core surface, and wherein the laminate meets or exceeds the desired drainage specifications of the slope. Methods of the invention may include the further step or act of C) providing a base layer on or adjacent to the laminate, wherein the base layer is provided on or adjacent to the lower layer lower surface and on or adjacent to the exposed sections of the core. Moreover, the base layer can be permeable or impermeable to fluids such as aqueous-based fluids and gases, and may comprise one or more of membranes, grids and geotextiles.  
         [0021]     As yet a further advantage, the flow zones and friction zones may be provided in any pattern or patterns that provide desired drainage patterns, ease the installation of the laminates, and make the junctures between adjoining portions or pieces of laminates contribute to the overall performance and efficiency of the means and methods of the invention. Examples of such patterns include strips of flow zones interposed between strips of friction zones, strips of flow zones interposed between strips of anchor zones, tree-like shapes, dendritic shapes, checkerboards, geometric shapes, and shapes determined by the desired flow pattern or flow path of a slope or slopes.  
         [0022]     Consonant with other objects of the invention, one or more of the base layer, the upper layer, the lower layer and the core are formed of one or more thermoplastics, and wherein the one or more thermoplastics are selected from the group consisting of polyethylene, high density polyethylene (“HDPE”), polypropylene, glass-filled plastics, and ABS. Moreover, the present methods of the invention may result in desired flow capacities in the nature of those discussed herein for laminates of the invention, that is, the present methods can provide transmissivity performances for the at least one flow zone, or for the laminate as a whole, in the ranges of from at least 10 −3  M 2  sec −1  of aqueous liquid at a normal load of at least 100 PSF (pounds/ft 2 ) sustainable for at least 100 hours when tested in accordance with ASTM 4716 to similar capacities at pressures of 1,000 PSF (pounds/ft 2 ), 5,000 PSF, 10,000 PSF and at least 15,000 PSF sustainable for at least 100 hours when tested in accordance with ASTM 4716.  
         [0023]     As one of skill in the art can appreciate, the present invention includes a plethora of embodiments that are resistant to unwanted movement after they are installed. These embodiments are thus particularly useful for sloped applications. High-friction geonets and geocomposites of the invention include one or both of high-friction elements and geonets made of high-friction materials formed by extruding and or forming conventional polymers into core layers which maintain channels for the flow of fluids such as water.  
         [0024]     Geonet structures suitable for use with the invention include any which provide drainage capacity alone or in combination with one or more other layers. Exemplary of these are geonets which maintain flow channels for transmitting fluids, such as water-based fluids and gases, in a desired direction, as well as void-maintaining geonets such as those comprising biplanar, triplanar, or cuspidated cores. Some embodiments of the present invention are achieved by bonding sections, strips, or pads of frictional materials of specified size, shape, and geometry to the lower surface of a one-sided geocomposite. With such combinations, laminates having the advantages of both double-sided and single-sided geocomposites are produced.  
         [0025]     One important aspect of the present invention is that it produces laminates of high transmissivity and adequate friction at relatively low cost. This combination of characteristics is important particularly because failure to maintain design flow parameters often results in increased hydrostatic pressure on an underlying geomembrane. Such a failure can cause rupture and even catastrophic collapse of a geomembrane system. The present invention significantly ameliorates such problems by providing laminates with high transmissivity, adequate friction, and competitive costs.  
         [0026]     As one advantage of the present invention, geocomposite structures having atypically high frictional properties can be achieved at lower unit costs while maintaining or increasing desirable flow characteristics. Geonet and geocomposite structures according to the present invention are thereby suitable in those applications to complement or replace sand, stone, or gravel in civil and environmental construction projects even when harshly acidic or alkaline liquid interactions are expected and overlying or underlying geomembranes or geotextiles are utilized.  
         [0027]     Typical characteristics of hybrid geocomposite laminates according to the invention include: a continuous upper permeable or impermeable surface, a geonet or other flow-maintaining center, and discontinuous lower layers such as strips of high-friction substrate laminated to the lower surface in such a manner that high-friction sections of the laminate interact with adjacent layers to form high-frictional areas adjacent to or between areas having lower frictional characteristics.  
         [0028]     A flow zone (the void-maintaining portions) of a geocomposite laminate of the invention has a transmissivity rate of not less than 1×10 −3  m 2 /sec, or not less than 1.5×10 −3  m 2 /sec, preferably not less than 2.5×10 −3  m 2 /sec, more preferably not less than 4×10 −3  m2/sec even more preferably not less than 5×10 −3  m2/sec or more preferably not less than 7.5×10 −3  m2/sec and most preferably not less than 1×10 −2  m2/sec when used adjacent a lower fluid-impermeable layer, and tested in accordance with ASTM D4716 at a hydraulic gradient of from 0.01 to 1.0 at a normal stress of not less than 100 psf or not less than 500 psf, or not less than 1,000 psf, and preferably not less than 5,000 psf or 10,000 psf, and most preferably not less than 15,000 psf with boundary conditions of soil/geotextile/geonet/geomembrane.  
         [0029]     A friction zone (having a both upper and lower geotextile layers) of a geocomposite laminate of the invention has a transmissivity rate, when combined with an adjacent fluid-impermeable membrane, of not less than 5×10 −4  m 2 /sec when tested in accordance with ASTM D 4716 at a hydraulic gradient of from 0.01 to 1.0 at a normal stress of not less than 100 psf and not greater than 25,000 psf with boundary conditions of soil/geotextile/geonet/geotextile/geomembrane.  
         [0030]     Embodiments of the invention are particularly useful for installation in slopes of significant angles because they exhibit increased resistance to movement while maintaining high transmissivity. Essentially, the weighted friction angle is an average of the two friction angle values for a laminate having both friction zones and flow zones and approximately proportional to their relative areas. Thus, while friction angles for friction zone portions of a laminate range from 18-32 degrees, friction angles for flow zone portions range from 8-10 degrees.  
         [0031]     Accordingly, the weighted friction angle for a geocomposite according to the invention would depend upon the relative area ratios of friction zone laminate to flow zone laminate. For example, in embodiments where the ratio of flow zone area to friction zone area is 1:1, the weighted frictional angle values would be in the range of from 14 to 21 degrees. Thus, the present invention provides both desired resistance to movement, that is, increased shear resistance, as well as flow capacity increases of from 25-100% when compared with conventional laminates. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0032]      FIG. 1 ( a ) is a side view of a conventional double-sided geocomposite which typically would be installed above a geo-membrane;  
         [0033]      FIG. 1 ( b ) is similar to  FIG. 1 ( a ) but shows a fluid-impermeable membrane immediately against, that is, below the lower fluid-transmissible layer of a conventional geocomposite.  
         [0034]      FIG. 2 ( a ) is a side cross-sectional view of a laminate of the invention showing a combination single-sided/double-sided multizone geocomposite having flow zones disposed within a core element.  
         [0035]      FIG. 2 ( b ) is a similar view of the geocomposite of  FIG. 2 ( a ) but with an upper fluid-transmissable layer and a geonet core shown disposed downwardly into flow zones.  
         [0036]      FIG. 2 ( c ) is a similar view of the geocomposite of  FIG. 2 ( b ) but with an upper fluid-transmissable layer and geonet core shown disposed downwardly by an overburden into the flow zones.  
         [0037]      FIG. 3  is a bottom plan view of a double-sided geocomposite sheet laminate, wherein a lower fluid-transmissible geotextile is provided with a plurality of removed portions which form friction zones.  
         [0038]      FIG. 4  is a bottom plan view of a double-sided geocomposite sheet laminate having anchor zone, flow zones and frictions zones.  
         [0039]     FIGS.  5 ,  6 ( a ) and  6 ( b ) are side views of geocomposites having friction strips disposed on the bottom surface of the void-maintaining core element.  
         [0040]      FIG. 7 ( a ) is a side cross-sectional view of a discontinuous double-sided multizone geocomposite wherein Portions of the laminate have only two layers, and form pinch zones.  
         [0041]      FIG. 7 ( b ) shows the geocomposite of  FIG. 7 ( a ) installed within a sloped site.  
         [0042]      FIG. 8 ( a ) is a side cross-sectional view of combination double-sided multizone geocomposite having a geonet core and intermittent upper and lower layers to form anchor zones.  
         [0043]      FIG. 8 ( b ) is similar to  FIG. 8 ( a ) but additionally shows the geocomposite installed within a sloped site having an overburden layer and a subbase.  
         [0044]      FIG. 9  ( a ) is a bottom plan view of a tree pattern 3-layered, or double-sided, multiple zone geocomposite having anchor zones.  
         [0045]      FIG. 9  ( b ) is a bottom view of a tree pattern 3-layered, or double-sided, multiple zone geocomposite having friction zones.  
         [0046]      FIG. 10  is a bottom plan view of three separate 3-layered multiple zone geocomposite sheets similar to the tree pattern 3-layered sheet shown in  FIG. 9 ( b ), and juxtaposed to form preferential drainage paths.  
         [0047]      FIG. 11  is a bottom view of four separate 3-layered (or double-sided) multiple zone geocomposite sheet goods according to the invention juxtaposed and aligned to form preferential drainage paths.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0048]     The invention may be understood both with respect to the textual description provided herein and also with respect to the accompanying figures, which are exemplary only and show only a few of the many permutations of embodiments of the present geo-stabilizers.  
         [0049]     Within the meaning of the invention, a geonet core can be of any material so long as it provides the needed design strengths and performance characteristics. Depending upon the specific embodiment, a geocomposite of the invention can be installed with or without a geomembrane beneath it. Moreover, the numerous embodiments of the present invention can be adapted to specific uses since resistance to movement is provided in several different aspects.  
         [0050]     The present invention includes methods for designing and using its myriad embodiments. Thus, any combination of flow zones, friction zones and anchor zones can be combined to form a drainage structure of desired drainage capacity and resistance to movement on a given slope. For example, the present invention includes a method for providing drainage specific to a target structure comprising the steps of formulating target drainage capacities regarding a structure or installation, providing a geocomposite which comprises a core element, the core element having a plurality of interconnected voids or channels of desired flow capacity to transmit a desired quantity of fluid, the core element also having an upper surface and a lower surface, and attached adjacent the upper surface, at least one upper layer, and attached adjacent the core lower surface, at least one lower layer wherein the lower layer comprises discontinuities that form flow zones and friction zones, wherein the formulating is performed with respect to one or more site factors including size of the structure, the slope of the site, the soil types of the site, and the required drainage capacities.  
         [0051]     A drainage geocomposite of the invention thus has a high resistance to movement within sloped installations, and comprises a core element, the core element having a plurality of interconnected voids or channels of desired flow capacity to transmit a desired quantity of fluid, the core element also having an upper surface and a lower surface, and attached adjacent the upper surface, at least one upper layer, and attached adjacent the core lower surface, at least one lower layer wherein the lower layer comprises discontinuities. Embodiments of the invention include those wherein one or both of the upper layer and lower layer are fluid-transmissible and wherein the discontinuities are patterned or random.  
         [0052]     In the field of conventional drainage geocomposites, a single-sided geocomposite comprises a geonet along with one fluid-transmissible geotextile layer attached, typically, to the upper surface of the geonet. A double-sided geocomposite is typically a geonet core having one fluid-transmissible geotextile layer attached to the geonet&#39;s upper surface and one geotextile layer attached to the lower surface of the geonet core. In some embodiments of either a single-sided or double-sided geocomposite, instead of a geotextile layer, other sheet-form materials are used such as fluid-impermeable membranes. The present invention advantageously provides heretofore unavailable geocomposite drainage structures which comprise one of more of friction zones, flow zones and anchor zones.  
         [0053]     In the accompanying drawings, friction zones are shown as diagonally hatched areas. Friction zones are those portions of a geocomposite laminate which are double-sided. In other words, a friction zone is that portion where the geonet core has a geotextile (or other) layer attached to its upper surface, and a geotextile (or other) layer attached to corresponding portions of its lower surface for engaging an underlying layer such as a geomembrane in such a manner that movement of the geocomposite with respect to the geomembrane is resisted. Thus, a friction zone is an area of the geonet core which has a lower layer, such as a high-friction scrim or a geotextile, for gripping an adjacent layer, such as a fluid-impermeable membrane disposed adjacent to and under the geocomposite. Other portions of the geonet core are single-sided. Thus, in embodiments of the invention where frictions zones are intended to be disposed downwardly for engagement with an adjacent geomembrane for example, the friction zones are those portions of the geonet core having a geotextile or other layer attached to the upper surface of the core and a high-friction scrim or geotextile on parts of the lower surface of the core.  
         [0054]     Because friction zones have layers of geotextile (or other materials) on both surfaces, intrusion of these upper and lower layers into the geonet core reduces the core&#39;s effective dimensions, and thus limits the transmissivity of the friction zones. In an advantageous contrast, flow zones of the present invention provide increased transmissivity performance when compared with conventional double-sided geocomposites.  
         [0055]     In some of the accompanying drawings, flow zones, which are single-sided portions of a geocomposite, are shown in white with arrows depicting general flow directions when the laminate is disposed in a slope manner. As elucidated herein, in contrast to friction zones of the invention, flow zones are those single-sided portions of the laminates of the invention where the geonet core is free to contact an underlying layer, such as a fluid-impermeable membrane in such a manner that void spaces are maintained. Among other advantages, flow zones of the invention are therefore substantially free of intrusion from a lower layer. Because of this, flow zones exhibit superior transmissivity, that is, an increased capacity for the flow of fluids, such as gases and water-based liquids, through the geocomposite to exit the site to be drained.  
         [0056]     In the accompanying drawings, anchor zones are shown by cross-hatched areas. Anchor zones are geonet-exposed portions of a single-sided or double-sided geocomposite. Alternatively stated, an anchor zone is where geotextile (or other) layers are absent from corresponding portions of both the upper and lower surfaces of the geonet core. Thus constructed and arranged within a laminate of the invention, anchor zones make the geonet core available from both of its surfaces for interaction with the soils in which it is placed to provide, for example, additional resistance to movement of the laminate in the soil. Geocomposite laminates comprising anchor zones can be particularly useful in applications where the roots of vegetation planted on the installation site can grow through the exposed portions of the geonet core to thereby provide an additional source of anchoring and resistance to movement.  
         [0057]     The following descriptions and accompanying figures are not exclusive but are exemplary and illustrative of the many embodiments of the present invention and are thus not limiting with respect to the scope and spirit of the invention. Therefore, as one of skill in the art will comprehend, numerous combinations of the flow zones, friction zones, pinch zones and anchor zones of the invention are achievable within the bounds of the present disclosure and invention.  
         [0058]      FIG. 1 ( a ) is a side view of a conventional double-sided geocomposite  6  having geonet core  9 , upper fluid-transmissable layer  11  disposed on the upper surface of core  9  and lower fluid-transmissible layer  13  disposed on the lower surface of core  9 . In one type of typical conventional installation, such a geocomposite would be installed above a geo-membrane, that is, above a fluid-impermeable membrane, such as membrane  15 , which is shown below but not touching geocomposite  6 . Typically, such fluid-impermeable membranes are provided with roughened or uneven surfaces in order to increase the coefficient of friction between the membrane and an overlying geocomposite, and thereby minimize the movement of the geocomposite and overburden disposed upon geocomposite  6 .  
         [0059]      FIG. 1 ( b ) is similar to  FIG. 1 ( a ) but shows fluid-impermeable membrane  15  immediately against lower fluid-transmissible layer  13  of conventional geocomposite  6 .  
         [0060]      FIG. 2 ( a ) is a side cross-sectional view of an embodiment of the invention showing combination single-sided/double-sided multizone geocomposite  46  having geonet core  49  comprising, for example, polyethylene or polyolefin polymers, upper fluid-transmissable layer  41  disposed on the upper surface of high-friction core  49  and lower fluid-transmissible layer  53  disposed on part of the lower surface of core  49 . The discontinuities, or absence portions of lower geotextile  53 , form the margins of flow zones FZ which are disposed within core element  49  and between upper fluid-transmissable layer  41  and lower fluid-transmissible layer  53 . In one type of installation according to the present invention, geocomposite  46  would be installed above a geo-membrane, that is, above a fluid-impermeable membrane such as membrane  75 , which is shown below, but not touching, geocomposite  46 .  
         [0061]      FIG. 2 ( b ) is also a side cross-sectional view of combination single-sided/double-sided geocomposite  46  similar to that of  FIG. 2 ( a ) but with upper fluid-transmissable layer  41  and geonet core  49  shown disposed downwardly by overburden  42  into flow zones FZ formed by the removed portions of lower fluid-transmissible layer  53 .  
         [0062]      FIG. 2 ( c ) is similar to  FIG. 2 ( b ) but shows geocomposite  46  installed within a sloped site and having fluid-impermeable membrane  75  immediately against lower fluid-transmissible layer  53  of geocomposite  46 .  FIG. 2 ( c ) also shows overburden layer  42 , and subbase  43  which may comprise one or more of, for example, soils, rocks, aggregates, reinforcing materials and paving, compressing high-friction core  49  into fluid-impermeable membrane  75  at friction zones F to thereby increase the resistance to movement of geocomposite  46  with respect to membrane  75 , overburden layer  42  and subbase  43 .  
         [0063]      FIG. 3  is a bottom plan view of double-sided geocomposite sheet laminate C according to the invention, wherein lower fluid-transmissible geotextile  63  is provided with a plurality of removed portions. The exposed portions of lower geotextile  63  form friction zones F disposed for contact, for example, with a fluid-impermeable membrane(not shown) which would underlie laminate C in a sloped installation. In this embodiment, flow zones FZ are disposed parallel to friction zones FZ.  
         [0064]      FIG. 4  is a bottom plan view of double-sided geocomposite sheet laminate K according to the invention, wherein lower fluid-transmissible geotextile  73  is provided with a plurality of removed portions which form both anchor zones A or frictions zones F. Anchor zones A are one-layered, that is, they are formed by the absence of both an upper layer and a lower layer on portions of the core element. Three-layered sections of the laminate K form friction zones F which, along with flow channels C are provided between two-layered (single-sided geocomposite sections) flow zones FZ, anchor zones A or frictions zones F to allow the flow of fluids through the geocomposite.  
         [0065]     FIGS.  5 ,  6 ( a ) and ( b ) are side views of geocomposites D and B according to the invention showing friction strips  39  disposed on the bottom surface of core element  51 .  FIG. 6 ( b ) shows fluid-impermeable membrane  54  adjacent to friction strips  39  of laminate B. The increased friction provided by the interaction between membrane  54  and friction strips  39  provides increased resistance to movement of laminate B with respect to membrane  54 .  
         [0066]      FIG. 7 ( a ) is a side cross-sectional view of discontinuous double-sided multizone geocomposite  101  having discontinuous high-tensile-strength geonet core  109  made of, for example HDPE, upper fluid-transmissable layer  111  disposed on all of the upper surface of high-tensile-strength core  109  and lower fluid-transmissible layer  113  disposed on all of the lower surface of core  109 . Geonet core  109  is discontinuous being provided, for example, in one or more strips or portions disposed between layers  111  and  113  to form 3-layer laminated sections or flow zones  115 . Portions of the laminate having only two layers, that is, where fluid-transmissable layer  111  and lower fluid-impermeable layer  113  are immediately adjacent to one another, and form pinch zones P which separate flow zones  115  from one another. In some embodiments (not shown) high-tensile-strength core  109  is provided only with upper fluid-transmissable layer  111  disposed on all of the upper surface of core  109  and no lower layer is provided on the lower surface of core  109 .  
         [0067]      FIG. 7 ( b ) shows geocomposite  101  of  FIG. 7 ( a ) installed within a sloped site having overburden layer  42  and subbase  43  both of which may comprise one or more of, for example, soils, rocks, aggregates, reinforcing materials and paving materials. Portions of overburden layer  42  and subbase layer  43  intrude into pinch zones P to thereby increase the resistance to movement of geocomposite  101  with respect to overburden layer  42  and subbase  43 . In the embodiment shown in FIGS.  8 ( a ) and ( b ), flow zones  115  are formed by geonet core strips  109  which are disposed parallel to one another in laminate  101 , and are thus arranged such that strips  109  extend the full length of geocomposite  101  but are separated along their full lengths by a plurality of pinch zones P. Advantageously, the difference in thicknesses between flow zones  115  and pinch zones P is such that it contributes to the movement-resistant characteristics of geocomposite  101 .  
         [0068]      FIG. 8 ( a ) is a side cross-sectional view of combination double-sided multizone geocomposite  96  having high-tensile-strength geonet core  99  comprising, for example, HDPE reinforced with glass fibers, upper fluid-transmissable layer  91  disposed on portions of the upper surface of high-tensile-strength core  99  and lower fluid-impermeable layer  93  disposed on corresponding portions of the lower surface of core  99 . Anchor zones A are formed in geocomposite  96  by the removed portions of upper fluid-transmissible layer  91  and lower fluid-impermeable layer  93  disposed on corresponding portions of the lower surface of core  99 . Flow zones FZ are the voids formed between layers  91  and  93  of geocomposite  96 . Flow zones FZ can be of any desired shape or pattern and can be configured in advance of the installation of geocomposite  96  in a site.  
         [0069]      FIG. 8 ( b ) is similar to  FIG. 8 ( a ) but shows geocomposite  96  installed within a sloped site having overburden layer  42  and subbase  43  which may comprise one or more of, for example, soils, rocks, aggregates, reinforcing materials and paving materials. Portions of overburden layer  42  and subbase layer  43  intrude into anchor zones A to thereby increase the resistance to movement of geocomposite  96  with respect to overburden layer  42  and subbase  43 .  
         [0070]      FIG. 9  ( a ) is a bottom plan view of a tree pattern 3-layered, or double-sided, multiple zone geocomposite having portions of both the upper and lower layers removed to expose anchor zone portions of the core element. Anchor zones A are portions of the core element having no geotextiles attached to either the upper or lower surfaces of the core element such that the core element can be engaged from all sides by the soils in which the laminate is placed. In installations where the laminate is installed on top of an impermeable membrane, high-friction portions of the geonet core, that is anchor zones A, are pressed in contact with the membrane to thereby increase resistance of the laminate to unwanted movement.  
         [0071]      FIG. 9  ( b ) is a bottom view of a tree pattern 3-layered, or double-sided, multiple zone geocomposite having portions of only the lower layer removed to expose the core element. The 3-layered portions of the laminate are high-friction segments F, that is, friction zones F disposed for engaging material adjacent to the laminate. In use with a fluid-impermeable membrane, the bottom of the geocomposite is disposed downwardly and on top of the membrane (not shown) such that Friction Zones F, typically of a high-friction scrim or geotextile, are pressed into the fluid-impermeable membrane thereby increasing the frictional coefficient between the laminate and the fluid-impermeable membrane when compared with that of a conventional laminate having no friction zones.  
         [0072]      FIG. 10  is a bottom plan view of three separate 3-layered (or double-sided) multiple zone geocomposite sheets according to the invention juxtaposed to form preferential drainage paths. In  FIG. 10 , Sheets A and B, which are both similar to the tree pattern 3-layered sheet shown in  FIG. 9 ( b ), and are juxtaposed such that their respective flow zones and friction zones abut one another to thereby form the preferred flow paths shown by arrows on the figures. Sheets A and B are each provided with an Exit Gate  5 , a continuation of the respective flow zones providing egress for fluids that are transmitted through Sheets A, B and C. Sheet C is constructed and arranged such that its flow zones and friction zones abut the respective flow zones and friction zones of Sheet B such that fluids entering the upslope portions of Sheet C are preferentially directed toward the flow zone of Sheet B. for egress through Exit Gate  5 . Exit gates  5  are disposed for connecting with downslope drainage components such as pipes, culverts, and the flow zones of other sheets.  
         [0073]      FIG. 11  is a bottom view of four separate 3-layered (or double-sided) multiple zone geocomposite roll goods according to the invention juxtaposed and aligned to form preferential drainage paths. In  FIG. 11 , Sheets G, H, I and J, are juxtaposed such that their respective flow zones and friction zones F abut one another to thereby form the preferred flow paths shown by the arrows on the figures. In use, the bottoms of juxtaposed Sheets G, H, I and J, are disposed downwardly and on top of a fluid-impermeable membrane (not shown) such that friction zones F are pressed into the fluid-impermeable membrane. With a high-friction core element according to one aspect of the invention such as one made of polyolefin polymers or recycled tire rubber, the friction between Sheets G, H, I and J, and the fluid-impermeable membrane is thus increased over that of a conventional laminate having no friction zones.  
         [0074]     The present invention may be understood both with respect to the textual description provided herein and also with respect to the accompanying figures, which are exemplary only and show only a few of the many permutations of embodiments of the present geo-stabilizers. Thus, as one of skill in the art will appreciate, the spirit and scope of the invention includes any combination of flow zones and friction zones, or any combination of flow zones, friction zones and anchor zones, as well as methods for designing and using them to form a drainage structure of desired drainage capacity and resistance to movement on a given slope.