CA1230980A - Elongated bendable drainage mat - Google Patents
Elongated bendable drainage matInfo
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- CA1230980A CA1230980A CA000451022A CA451022A CA1230980A CA 1230980 A CA1230980 A CA 1230980A CA 000451022 A CA000451022 A CA 000451022A CA 451022 A CA451022 A CA 451022A CA 1230980 A CA1230980 A CA 1230980A
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- Prior art keywords
- mat
- fingers
- drainage mat
- fabric
- drainage
- Prior art date
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Abstract
APPLICATION FOR LETTERS PATENT
FOR
ELONGATED BENDABLE DRAINAGE MAT
ABSTRACT OF THE INVENTION
Elongated bendable drainage mat having a rectangular transverse cross section and comprising a polymeric core having a plurality of substantially rigid fingers extending from one side of a layer and an enveloping water permeable fabric. Apparatus and systems using such drainage mat.
FOR
ELONGATED BENDABLE DRAINAGE MAT
ABSTRACT OF THE INVENTION
Elongated bendable drainage mat having a rectangular transverse cross section and comprising a polymeric core having a plurality of substantially rigid fingers extending from one side of a layer and an enveloping water permeable fabric. Apparatus and systems using such drainage mat.
Description
" ~3~38~
ELONGATED BENDABLE DRAINAGE MAT
I~ACI~ID OF ~1911 lWl~ZIII~
This invention relates t:o multidirectional drainage mats ~hich are useful and effective, for in~tance as a highway edge drain for ~he dewatering of highway pavement systems.
The problem of water in pavements ha~
been of concern to engineers for a considerable period of time. As early as 1823 McAdam reported to the London (England) Board of Agriculture on t~e importance of keeping the pavement subgrade dry in order to carry heavy loads without distress. ~e discussed the importance of maintaining an impermeable surface over the subgrade in order to keep water out of the subgrade.
The types of pavement distresses caused by water are quite numerous. Smith et.al. in the "Highway Pavement Distress Identification ~anual"
(1979) prepared for the Federal Highway Admini~tration of the United States Department of Tran~portation identifies most of ~he common types of distre~ses.
Moi~ture in paYement systems can come from several sources. Moisture may permeat~ the ~ides, particularly where coarse-grained layers are present or where surface drainage facilitie~ within the vicini~y are inadequate. The water table may rise; this can be e2pected in the winter and spring seas~ns. Surface water may enter joints and cracks in the pavement, penetrate at the edges of the surfacing, or percolate through ~he surfacing and shoulders.
Water may move vertically in capillaries or interconnected water films. Moisture may move in vapor form, depending upon adeguate temperature gradient~ and air void space. Moreover, the problem of water in pavement systems often becomes more severe .
35 .in areas where frost action or freeze-thaw cycles 3 ~
occur, as well as in areas of swelling soils and shales.
The type~ of pavement distresses caused ~y water are quite numerou~ and vary depending on the type of pavement ~ystem. For flexible pav2ment systems some of the dlstresses related to water either alone or in combination with temperature include:
potholes, loss of aggregates, raveling, weathering, alligator cracking, reflective cracking, shrinkage cracking, shoving, and heaves ( from frost or swelling ~oils). For rigid pavement ~ystems, some o~ the distresses include faulting, joint failure, pumping, corner cracking, diagonal cr~cking, transverse cracking, longitudihal cracking, shrinkage cracking, blowup or bucklingl ~urling, D-cracking, surface spalling, steel corrosion and heaving (from frost or swelling soils). Similar types of distresses occur in taxiways and ru~ways of airfields.
Numerous of these joint and slab distresses are related to water pumping and erosion of pavement base materials used in rigid p~vement construction. Water pumping and erosion of pavement base materials have been observed to cause detrimental effect~ on shoulder performance as well. Also, many of the distresses observed in asphalt concrete pavements are caused or accelerated by water.
For instance, faultinq at the joi~ts is a normal manifestation of distress of unreinforced concrete paveme~ts without load transfer. Faulting can occur under the following conditions:
1. The pavement ~l~b ~ust have a slight curl with the individual slab ends raised slightly off the llnderlyi~g stabilized layer ~thermal gradients and differential drying within the slab create this condition).
3 ~ 3
ELONGATED BENDABLE DRAINAGE MAT
I~ACI~ID OF ~1911 lWl~ZIII~
This invention relates t:o multidirectional drainage mats ~hich are useful and effective, for in~tance as a highway edge drain for ~he dewatering of highway pavement systems.
The problem of water in pavements ha~
been of concern to engineers for a considerable period of time. As early as 1823 McAdam reported to the London (England) Board of Agriculture on t~e importance of keeping the pavement subgrade dry in order to carry heavy loads without distress. ~e discussed the importance of maintaining an impermeable surface over the subgrade in order to keep water out of the subgrade.
The types of pavement distresses caused by water are quite numerous. Smith et.al. in the "Highway Pavement Distress Identification ~anual"
(1979) prepared for the Federal Highway Admini~tration of the United States Department of Tran~portation identifies most of ~he common types of distre~ses.
Moi~ture in paYement systems can come from several sources. Moisture may permeat~ the ~ides, particularly where coarse-grained layers are present or where surface drainage facilitie~ within the vicini~y are inadequate. The water table may rise; this can be e2pected in the winter and spring seas~ns. Surface water may enter joints and cracks in the pavement, penetrate at the edges of the surfacing, or percolate through ~he surfacing and shoulders.
Water may move vertically in capillaries or interconnected water films. Moisture may move in vapor form, depending upon adeguate temperature gradient~ and air void space. Moreover, the problem of water in pavement systems often becomes more severe .
35 .in areas where frost action or freeze-thaw cycles 3 ~
occur, as well as in areas of swelling soils and shales.
The type~ of pavement distresses caused ~y water are quite numerou~ and vary depending on the type of pavement ~ystem. For flexible pav2ment systems some of the dlstresses related to water either alone or in combination with temperature include:
potholes, loss of aggregates, raveling, weathering, alligator cracking, reflective cracking, shrinkage cracking, shoving, and heaves ( from frost or swelling ~oils). For rigid pavement ~ystems, some o~ the distresses include faulting, joint failure, pumping, corner cracking, diagonal cr~cking, transverse cracking, longitudihal cracking, shrinkage cracking, blowup or bucklingl ~urling, D-cracking, surface spalling, steel corrosion and heaving (from frost or swelling soils). Similar types of distresses occur in taxiways and ru~ways of airfields.
Numerous of these joint and slab distresses are related to water pumping and erosion of pavement base materials used in rigid p~vement construction. Water pumping and erosion of pavement base materials have been observed to cause detrimental effect~ on shoulder performance as well. Also, many of the distresses observed in asphalt concrete pavements are caused or accelerated by water.
For instance, faultinq at the joi~ts is a normal manifestation of distress of unreinforced concrete paveme~ts without load transfer. Faulting can occur under the following conditions:
1. The pavement ~l~b ~ust have a slight curl with the individual slab ends raised slightly off the llnderlyi~g stabilized layer ~thermal gradients and differential drying within the slab create this condition).
3 ~ 3
2. Free ~ater must be present~
3. ~eavy loads must cross the transYerse joints first depre~ing the approach side of ~he joint, then allowi~g a sudden rebound, while instantaneously impacting the leave ~ide of the joint causing a violent pumping action of free water.
4. Pumpable fines must be present (untreated base material, the sur-face of the stabilized base or subgrade, and forei ~ material entering the joints can be classified as pumpable fines).
Faulting of 1/4 in. or more adversely affects the riding quality of the pavement system.
Methods for predicting and controlling water contents in pavement systems are well documented by Dempsey in 'IClim~tic Effects on Airport Pavement Systems~^State of the Art", Report No. FAA-RD-75-196 ~1976), United States Department of Defense and United States Department of Transportatisn. Methods for controlling moisture in pavement systems can generally be cla~sified in terms of protection through the use of waterpr~ofing membranes and anticapillary courses, the utilization of materials which are insensitive to moisture changes, and water evacuation by means of subdrainage.
Fiel~ investigations indicate tha~
evacuation by ~eans of a subdrainage system i5 often the preferred method for controlling water in pavement systems. In this regard proper selec~ion, design, ~nd con truction of the subdrainage system is important to the long-term pe~formance of a pavement. A highway subsurface drainage system should, among other functions, intercept or cut off the ~eepage above an impervious boundary, draw down or lowex the water ~ 3 ~ 4-table, and/or collect ~he flow from other drainage systems.
Exi~ting highway drains include a multitude of designs. Among the simplest ~re those which comprise a perorated pipe installed at the bottom of an excavated trench backfilled with sand or coarse aggregate. For instance, a standard drain specified by the State of Illinois re~uires a 4-inch di~neter perforated pipe be placed in the hottom of a trench 8 inches (20.3 cm~ wide by 30 inches (76 cm) deep. The trench is then backfilled with oarse sand meeting the State of Illinois standard FAl or FA2.
Such drains are costly to fabricate in terms of labor and materials. For instance the material excavated from the trench must be hauled to a disposal site, and sand b~ckfill must ~e purchased and hauled to the drain construction site.
Other types of dxains have attempted to avoid the use of the perforated pipe by utilizing a synthetic textile fabric as a trench liner. The fabric-lined trench is filled with a coarse aggregate which provides a support for the fabric. The ~oid space within the combined aggregate serves as a conduit for collected water which permeates the fabric. Such drains are costly to install, for instance in terms of labor to lay in and fold the fabric as well as in terms of haulage of excavated and backfill material. Moreover, there is considerable ' fabric area blocked ~y contact with the aggregate surface. This results in an increased hydraulic resistance through the fabric areas contacting the aggregate surface.
Other ~odifications to drai~age material include fabric c~vered perforated conduit, such as corrugated pipe as disclosed by Sixt et.al. in United States Patent 3,330,373 or raised surface pipe as disclosed by Uehara et.al. in United States Patent ~ ~ ~ Q 98 ~ -5- ~
4,182,581. A disadvantage is ~hat the planar surface area available for intercepting ~ubsurface water is limited to approximately the pipe di~meter unless the fabric covered perforated ~onduit is installed at the hottom of an interceptor trench fille!d, say, wlth coarse sand. A further disadvantage is that much of the fabric surface, say ~bout 50 perc:ent, is in contact with the conduit, thereby reclucing the effective collection area.
The problem of limited planar surface area for intercepting subsurface water is address~d by drainage products disclosed by Healy et.al. in United States Patents Nos. 3,563,038 and 3,654,765. Healy et.al. generally disclose a planar extended ~urface core covered with a filter fabric which serves as a water collector. One edge of the core terminates in a pipe-like cond~it for transporting collected water.
Among the configurations for the planar extended core are a s~uare-corrugated sheet and an expanded metal sheet. A major disadvantage of desi~ns proposed by Healy et.al. is that the drains are rigid and not bendable; this re~uires excavation of sufficiently long trenches that an entire length of drain can be installed. The pipe-like conduit reguires a wider trench than ~ight otherwise be needed. Moreover, the expanded metal sheet core does not provide adequate support to the fabric which can readily collapse again~t ~he opposing fabric surface, thereby greatly reducing the flow capacit~ within ~he core. Also the ~quare corrugated ~hee~ core is limited in that at least 50 percent of the fabric surface arc is occluded by the core, thereby reducing water collection area.
A related drainage material with extended surface is a two-layer composite of polyester non-woven filter fabric heat bonded to an expanded nylon ~on~woven matting, such as ENK~DRAINr foundation drai~aye material available from American Enka Company ~ ~3~9~ ~6 of En~a, North Carolina. The drainage material which can be rolled has ilter fabric on one side of the nylon non-woven matting. The drainage material serves as a collector only and requires installation of a conduit at the lower edge. This necessitates costly excavation of wide trenches, in addition to cost of conduit.
Another related drainage material with extended surface comprises a filter fabric covered core of cuspated polymeric sheet, such as STRIPDRAI~*
drainage product available from Nylex Corporation Limited of Victoria, Australia. The impervious cuspated polymeric sheet divides the core into two isolated opposing sections which keeps water collected on one side on that side. Moreover, in order that the drainage material be flexible, the core must be contained in a loose fabric envelope which, being unsupported on the core, can due to soil loading collapse into the core thereby hlocking flow channels.
2Q ~ The cuspated polymeric sheet i5 bendable only along two perpendicular axes in the plane of the sheet.
This makes installation somewhat difficult, for instance whole lengths must be inserted at once in an e~cavated trench.
A still further similar polymeric drainage product comprises a perforated sheet attached to 1at surfaces of truncated cones extending from an impervious sheet, su~h as CULDRAIN*board-shaped draining material available from ~itsui Petrochemical Industries, Ltd. The perforated sheet has holes in the range of O.S to 2.0 millimeters in diameter and allows fine and small particles to be leached from the subsurface ~oil.
The drainage materials available have one or more significant disadvantages, including economic disadvantages of re~uiring extensive amounts of labor for installation and performance disadvantages such as *Tracle r~arlc .
~ 9 ~
requirin~ separate conduit for removiny collected water.
This invention overcomet; mo~t if not all of the major disadvantages of such drainage materials.
For instance the drainage mat of this invention serves both as a collector, as well as a conduit for removing, intercepted ground water. The drainage mat of thi~ invention is flexible along any axis into one plane of its major longitudinal surface, this greatly facilitates installation of long lengths of drainage mat in incremental le~gths as trenches are excavated and backfilled within a short length. This provides a significant economic advantage in installation co~t when automatic installation equipment is utilized.
One embodiment of the drainage mat of this invention can, depending on hydraulic gradient, allow intercepted water to flow through any surface of the mat into a common conduit.
In the description of the present invention, the following definitions are used.
The term l'elongated drainage mat" as used in this ~pplication refers to a drainage mat having a length substantially larger than its width or depth.
The term "axis of elongation" as used in this application refers to the a~is passing through the center of an elongated drainage mat along its length.
The term "transverse rectangular cross sectionl' as used in this application refers to a cross section of an elongated drainage mat in a pl~ne normal to the axis of elongation of the drainage mat.
The term "pointing" as used in this application means a direction in which the axis o elongation of an elongated drainage mat i5 extended or aimed.
An elongated drainage mat is said to be "vertically-pointed" when the axis of elongatioll of ~ 3~ 8-the drainage mat is generally vertical with respect to the ~urface of the earth.
~ n elongated drai~age mat is ~aid to be "hori20ntally-pointed" when the axis of elongation of S the drainage mat is generally horizon.tal with respect to the ~urface of the earth.
The term "orientation" as used in this application refers to the attitude of an elongated drain ma~ having a rectangular txansverse cross ~ection determined by the relationship of the axes of the rectangular transverse cross section.
An elongated horizontally-pointed drainage mat having a rectangular transverse cross section is said to be "vertically-oriented" when the axis of tbe rectangular transverse cross section having the larger dimension is in a vertical position and the axis of the rectangular transverse cross section having the smaller dimension is in ~
horizontal position. The s2me drainaye mat, when rotated 90 around its axis of elongation, is ~aid to ~e "horizontally-oriented".
Among the useful parameters for characterizing fabric useful in the drainage mat of this invention i~ the coefficient of permeability which indicates the rate of water flow through a fabric material under a differential pressure between the two fabric ~urfaces e~pressed in terms of velocity, e.g., centimeters per second. Such coe~ficie~ts of permeability can be detenmined in accordance with American Soc~ety for Testing and Materials (ASTM) Standard D-737. Because of difficulties in determining the thickness of a fabric for use i~ determinlng a coefficient of permeability, it is often more convenient and meaningful to characterize fabric in terms of permittivity which is a ratio of the coefficient of permeability to fabric thickness, expressed in terms of velocity per o -9-thic]~ness, which reduces to inverse time, e.g., seconds 1. Permittivity can be determined in accordance with a procedure defined in Appendix A of Transportation Research Report 80-2, available from the United States Department of Transportation, Federal Highway Administration.
SUMM~RY OF THE INVENTION
This invention provides, in one aspect, a bendable drainage mat having a rectangular cross section. The drainage mat comprises a polymeric core having a flexible base layer with a plurality of substantially rigid fingers of substantially uniform height attached to only one side of the base layer and extending therefrom; and a water permeable fabric envel-oping the core and secured to a sufficient number of ends of the fingers such that the fabric does not unduly collapse. For convenience in installation the mat is often elongated.
So that the fabric does not unduly collapse in a flow-restricting manner into the conduit area of the mat it is generally desired that the fabric be secured to a sufficient number of the ends of the fingers. In most constructions the mat is bendable only such that the surface proximate the layer becomes convex.
This invention also provides a number of improved systems utilizing such drainage mat including, for instance, an improved highway system.
The invention, in another aspect, relates to a traffic carrying surface system comprising at least two pavement sections separated by an elongated joint and at least one vertically-oriented, elongated drainage mat having a rectangular transverse cross section installed below, in substantial alignment with, and proximate to the elongated joint, the elongated drainage mat comprising a polymeric core having a flexible base layer with a plurality of substantially rigid fingers attached to only one side of the base layer and e~tending therefrom and a water permeable fabric enveloping the core and secured to a sufficient number of ends of the fingers such that the fabric does not unduly collapse.
In accordance with another aspect of the present invention, there is provided a highway systern comprising a pavement section and a shoulder, positioned adjacent to the pavement section to form a joint therebetween, and a vertically-oriented, elongated, bendable drainage mat having a rectangular transverse cross section; wherein the drainage mat comprises a polymeric core having a flexible base layer with a plurality of substantially rigid fingers attached to only one side of the base layer and extending therefrom, and a water permeable fabric enveloping the core and secured to a sufficient number oE ends of the fingers such that the fabric does not unduly collapse; wherein the drainage mat has an upper edge positioned in substantial alignment with the joint, the edge being positione~ sufficiently close to the joint to intercept substantially all of any water passing through the joint to thereby prevent the water from spreading under the pavement section and shoulder.
BRIEF DESCRIPTION OF THE DRAWINGS
-FIGURE l illustrates an embodiment of a drainage mat accoraing to this invention.
FIGURE 2 illustrates an embodiment of a perforated layer having rod-like projections useful as 3a the three-dimensional core in a drainage ma-t according to this in~entionO
FIGVRE 3 illustrates a transverse cross-sectional view of a drainage mat.
FIGURE 4 schematically illustrates a cross-sectional view of a highway system with a drainage mat according to this invention installed proximate to a shoulder joint.
~3~
-lOa-FIGURE 5 schematically illustrates the position of bending axes with reference to the axis of elongation superimposed on the drainage mat surface which is proximate the ends of the fingers.
FIGURE 6 schematically illustrates -the characteristic of a drainage mat to change horizontal/vertical-pointing by rotating around a bending axis disposed at an angle of 45 from the axis of elongation.
FIGURE 7 schematically illustrates a partial cross-sectional view of continuous injection molding apparatus for producing polymeric core useful in the drainage mat.
FIGURE 8 illustrates a view of the surface of a useful core material opposite the side from which fingers extend.
FIGURE 9 is a schematic illustration of an artificial turf assembly utiliæing the drainage mat of this invention.
FIGURE 10 is a schematic illustration of a railroad system utilizing the drainage mat of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The elongated, bendable polymeric drainage mat having a rectangular transverse cross section comprises a polymeric core having a plurality of substantially rigid fingers extending from only one side of a base layer and an enveloping water permeable fabric. It is generally desirable that the fabric be secured to the core to avoid undesirable movement of the fabric relative to the core. For instance the fabric ~\
~3~)~38~
can be secured to the layer. In those instances when the layer is perforated, or otherwise permeable, the fabric 6hould totally e~elop ~he core including the perforated layer ~uch that perforations in the layer are covered by f~bric. To avoid occluding flow channels within the ~ore the fabric should also be secured to a ~ufficient number of ends of said fingers such that the fabric does not unduly collapse into space around the fingers. In some instances it may be sufficient that the fabric be secured to relatively few of the plurality of fingers, for instance less than 50 percent, ~ay even as low as 30 percen~ or even iO percent, of the flngers to avoid movement of the fabric relative to the ends of the fingers such that the fabric would unduly collapse into the space around the finger~ thereby occluding cross-sectional area otherwise available for fluid flow. In other cases it may be desirable that the fabric be secured to substantially all of the fingers to ensure that the structure of the drainage mat is maintained with a maximum t~ansverse cross-sectional area even after severe handl}ng, fGr instance in installation.
The drainage mats of this invention have unique properties characterized by a large surface area available for drainage, bendability for ease o~
installation, and a large open transverse cross-sectional area which serves as a conduit for allowing high multi-directional flow volumes for rapid evacuation of collected water.
A preferred form of t:he draina~e mat o thi~ invention is illustrated in Figures 1, 2 and 3.
In general, Figure 1 sc:hematically illustrates an embodiment of a section of drain~ge mat of this iT~vention where water permeable fabric 1 envelops core 2 having a plurality of substantially rigid fingers 4 extendi~g from one side of a layex 3. The axis of elonga~ion of the mat is indicated by axis 5.
~3~g8~
Figure 2 schematically illustrates an embodiment of a section of polymeric core useful in the drainage mat where the core has a p~urality of fingers 2~ extending from layer 23.
Figure 3 schematically illustrates a transverse cross section of drainage mat where fabric 31 envelops a core having a plurality of substantial].y rigid fingers 3~ extending from one side of a layer 33.
With reference to Figure 3, the drainage mat of this invention is readily bendable into the surface 35 proximate the ends 37 of the fingers 34. That is, the drainage mat is readily bendable only such that the surface 35 proximate the ends 37 of the f.ingers 3~
become concave, and the surface 36 proximate the layer 33 becomes convex. That is, the drainage mat is readily bendable such that spacing between the fingers at the base is substantially invariant and the spacing between the fingers at the end thereof can be decreased. In this regard the drainage mat can not be folded upon itself into the surface 36 proximate the layer 33 without an undue amount of force which is likely to tear the fabric or deform or collapse the core. This is especially the case when the fabric is bonded to the core. The mat is however readily bendable with little force such that the surface 35 proximate the ends 37 of the fingers 34 will readily and easily bend upon itself even up to about 1~0 around a bending axis having a radius of less than about 1 inch (2.54 cm), for instance as low as 0.25 inches ~0.63 cm). This bending lnto the surface proximate the ends of the fingers can be achieved around any bending axis parallel to the surface 35. In this regard ~igure 5 illustrates various bending axes superimposed on a drainage mat surface 56 proximate the ends of the fingers. Such bending axes are parallel to the surface 56 and are defined by their rotational ~rs~ disposition from axis of elongation 50 of the drainage ~` mat. A bending axis can be rotationally disposed at any angle from 0 to 180 from the axis of elongation ~3~8~) 50. For inst~nce the bending axis 51 is normal to the axis of elongation 50 (that i~, the :bending axis 51 i5 rotationally disposed at an angle of 90 from the axis of elongation 50). The drainage mat can be folded upon itself around bending axis 51 resulting in a shorter length; or such mat can be rolled into a short cylindrical spiral roll. The bending axis 52 is parallel to the axis of elongation 50 (that is, the bending axis ~2 is rotationally disposed at an angle of 0 from the axis of elongation 50). The drainage mat can be folded around bending axis 52 upon itself lengthwise or rolled into a long spiral roll.
~hen the drainage mat is folded upon itself up to about 180~ on a bending axis 53 which is rotationally disposed at an angle of 45 from the axis of elongation 50, the axis of elongation 50 o~ the drainage ~at will effect a 90 bend, as illustrated in Figure 6. This property of ~he drainage mat is particularly useful for those installations where the ~0 drainage mat 61 is to be installed below grade in a vertical orientation. In this regard the drainage mat can be provided in a vertical orientation above grade and guided to a roller 62 at an angle of 45. The drainage mat directed around such a roller 62 will be normal to a horizontal pl~n~ and can be guided to a second roller 63 at an angle of 45 at an elevation below grade. This second roller 63 will direct the drainage mat into a vertical orientation below grade in a position for its utilization.
Of course, rollers at other angles can be utilized to effect such changes in elevation.
Moreover, changes in horizontal positio~ can also be effected by rolIers disposed in horizontally parallel planes.
The drainage mat of this invention provides a large open tranverse cross-sectional area which provides little resistance to flow in any 3 ~ ~ ~O
~14- .
direction. A large ope~ transverse cros~-sectional area is provided by ~electing an optimum nu~ber of ~ubstantially rigid finger~ which provide the spaced-apart fabric suxfaces~
The core for use in the drainage mat of this invention is three-dimensional, having a plurality of substantially rigid ~ingers extending from one side of a layer. The layer can be impervious or perforated, depending on the intended use. When it is desira:~le that the drainage mat be capable of intercepting water from both major surfaces the layer should be perforated. A core with a perforated layer is illustrated in Figure 2 where layer 23 has a plurality of per~orations 25. Such perforations should be of sufficiently large area to allow water containing suspended solids to pass freely through the layer without pluggage by entrapped or bridged solids.
The fingers can comprise a very large group of shaped projections. As illustrated in Figure 2 a preferred finger is a r~d-like proje~tion which is cylindrical and projects in a direction normal to the plane of the layer. Fingers of other shapes can be utilized for instance fingers having square, hexagonal, star or oblong cross-sectional shape or with fin~, etc. Such shapes can be influenced by the mold desi~n utili~ed in the core forming process.
Al~hough solid fingers can be utilized, it is often desired that the fingers be hollow both for ease of fabrication and for minimizin~ the mass of the core to facilitate installation.
Regardless of shape, t~e fingers can be characterized as having a nominal diameter which is an average transverse dimension across the cross section of a finger. When the finger has a cylindrical shape normal to the plane of the base the nominal diameter is the diameter of the circular cross section; when the finger has some other geometric shape the nominal 1?~30980 diameter is an average transv2r6e dimension, for instance ~hen the finger is square ~haped the average transverse dimensio~ will be ~omewhat greater than a side of the ~quare but 60mewhat less than the diagonal of the ~guare. The nominal diameter dimension can be approximated by the average of the maximum and the minimum distance fro~ the center o~ the shape to a suxface.
In most instances it is preferred that fingers have a central axis which is normal ts the plane of the perforated layer. In other cases it may be desirable for fingers to project at some other angle from the perforated layer. ThP core can be characterized a~ having fingers which have a nominal diameter such that the ratio of the length of the fingers measured from the perforated layer to ~he end of the finger to the nominal diameter of the finger is in the range of from about 1:1 to about 8:1.
Tv provide a core with a maximum amount of cross-sectional area for fluid flow with the minimum resistance provided by fingers it is desirahle to provide a maximum spacing between fingexs.
~owever, fingers must not be spaced so far apart that the fabric will collapse into the space between fingers because of a lack of support. In this regard it is generally desired that the core be provided with an optimum spacing of fingers which can be characterized as an average center spacing, that is, the distance between centers of fin~ers intercepting the base. A~Prage center spacing can range from about 0.3 inches (0.76 cm~ to about 3 inches or more (7.6 cm)~ In many instances it is desired that the average center spacing range from 0.4 inches ~2.3 cm) to 1.25 inches (3.2 cm~.
Cores having utility in the drainage mat of this invention can have fingers with a length from about 0.125 inches (0.3 cm) to 3 inches or more ~7.6 ~3~80 16~
cm) in length and a nominal diameter of from about 0.1 inches ~0.25 cm) to 1.0 inch (2.54 cm~ or more.
However, it is often desired that the finger~ have ~
length from 0.5 inches ~1.3 cm) to 1.5 inches (3.8 cm) and a nominal diameter ~rom 0.15 inches (0.4 cm) to 0.5 inches (1.~ cm).
The depth of drainage mat will ~e approximated by the length of the fingers and the length can be very long, for instance up to about 400 feet (122 meters). The width of the drainage mat, that is, the larger dimension of its transverse rectangular cross section can range from 6 inches (15.2 cm) to more than 4 feet (122 cm~, say even up to 12 feet (365 cm) or more. The width will depend on the size of the apparatus used to fa~ricate the core.
Larger sizes can be fabricated by fastening two or more widths of core.
Drainage mats can be fabricated from a very large variety of polymeric materials. Among the preferred materials for the core are thermoplastic material6 such as polyethylene and polypropylene. For some uses, the preferred materials comprise low density polyethylene or linear low density polyethylene.
,25 Polymeric core useful in the drainage mat of this invention can be fabricated utilizing thermoplastic molding apparatus and processes well known to those skilled in such art. A preferred procedure for fabricating polymeric core having hollow cylindrical fingers is to utilize continuous molding apparatus as described by Doleman et.al. in U.S.
Patent 3,507~010.
Figure 7 illustrates a cross-sectional view of such continuous molding apparatus comprising a ~r 35 rotating cylindrical drum 70 having a plurality of '~ regularly spaced injection cavities 71. The cylindrical dr-~ 70 rotates in context with stationary ~ 17-injection head 74. The spacing of thle injection cavitie~ 71 ~ill correspond to the av~erage center ~pacing o ~he fingers exte~ding from o~e side of ~he core~ The cross-sectional 6hape of t.he injection cavities can be varied t~ produce fingers of a desired cross section, for instance circular, rectangular, star-shaped, etc. Such fingers can also be tapered, depending on the cavity design. Hollow fingers can also be produced by providing an annular injection cavity, as illustrated in Figure 7, where each injection caYity 71 is fitted with an insertion pin 72, having a reduced diameter extension 73. The length of the reduced diameter extension can be varied depending on the desired depth of the hollow bore within the finger.
Stationary injection head 74 has two rows of extension nozzles--high pressure nozz~es 76 and low pressure nozzles 75. The high pressure nozzles 76 provide molten thermoplastic material P from a pressurized reservoir 77 to the injection cavities 71 as they rotate into communication with the end of the high pressure nozzle 76. A high pressure nozzle 76 is aligned with each row of injection cavities 71 aligne~
around the circumference of the cylindxical drum 70.
The low pressure nozzles 75 are supplied with molten thermoplastic material P from the pressurized reservoir 77. Restrictors 78 in each low pressure nozzle reduce ~he pressure of the thermoplastic material ~xiting the end of each low pressure nozzle 3~ providing longitudinal stringers between rows of fingers .
Core geometry can be varied a~ desired by providing ~uch conti~uous injection molding apparatus with appropriate dimensions.
The enveloping water permeable fabric can comprise a wide variety of materials. Among the preferred fabric~ are those comprising polymeric ~`~ 3 ~
materials 6uch as polyethylene, polypropylene, polyamides, polyesters and polyacxyl:ic~. Other useful f~ric include~ glass fiber iEabric. In most in~tar~ces it is preferred Wlat the fabric comprise a hydrophobic material such as polypropylene or po:Lyester. Such fabric should be sufficiently water permeable that it exhibits a water permittivity in the range of from about O.2 seconds ~ to 2.0 seconds 1, More preferred fabrics axe those having a permittivity in ~he range of from about O.5 seconds 1 to about 1.0 ~econds The fabric can either be of a woven or non-woven manufacture; however non-woven fabrics are often generally preferred.
It is often desirable that the water permeable fabric envelop the entire core. When the layer is not perforated the fabric need only overlap the edges of the lay2r. ~owever, wh~n thç layex i~
perforated the fabric should entirely envelop the core. The fabric may be provided as a sock to ~lip 20 over the core. Alternatively the abric may be wrapped around the core such that there is an overlapping longitudinal seam to form the enveloping fabxic .
The fabric should of course be secured to 25 the core particularly to the ends of the fingers to avoid collapse of the iEabric into the conduit space of the core. A variety of me~hods of securing the fabric to the core may be employed. For instance, the fabric can be secured to the core by use of an adhesive, such ~s a hot melt adhesive. The fabric ca~ also be secured to the core by the use of mechanical fasteners or by sonic welding. Alternatively, the fabric c~n be secured to the ends of the fingers by causing the material of the ends of the finger6 to flow into the 3S fabric.
The drainage mat o~ this invention is u~eful in ~ny number of applications where it is ~L23~ 9 desirable to remove water from an area. ~or instance ~he mat can be u~ed in aguariums as a support for gravel. The penmeability of the fabric c~uld ~ary depending on whe~her filteriny would be desired.
The drainage mat can al~;o be advantageously utilized ~s a support for both natural and artificial turf. It is sometimes desirable to grow turf over a paved surface, f~r instance a patio or rooftop. The drainage mat of this invention can be laid in a horizontal orientation, preferably within a confined area, then covered with a layer of ~oil, such as loam, to support natural turf.
In many instances it is desirable to install artificial tur, such as synthetic grass-like playing surfaces, on a level surface. This has some disadvantages in outdoor installation which are subject to r~infall. Rainfall often accumulates on level in~tallations of artificial turf to the detriment of sport activities. The drainage mat o 2G this invention can be advantageously installed below the artificial turf, which is most o:Eten watex permeable, to collect and drain away rain wa~er. Even when installed on a level paved surface, the d~pth ~f the drainage mat will provide sufficient head to allow adequate water ~low over several hundred feet to drain connections. The drainage mat of this invention has sufficient strength to support playing activity including vehicle trsffic on the supported artifi~ial turf.
Reference is now made to Figure 9 which illustrates a cro~s-~ectional view of an artificial turf playing surface supported by a drainage mat in accordance with this invention. Artificial turf 91 is installed over a resilient mat 92 having a pluxality of perforations 93. The resilient mat ~2 is installed over a drainage mat 94, according to this invention.
The drainage mat can be installed with the layer ~ 8~ -20-against a supporting smooth surface 95; alternatively, if the layer is perforated, the drainage mat can be installed with the layex aqainst the re~ilient mat 92.
In some instances ~he dxainage mat can be utilized withol~t an enveloping water permeable fabric, for instance when the drainage mat is installed over concrete pavement or the like. However, when the drainage mat is installed over soil it is desirable to utilize an enveloping fabric to prevent water saturated soil from entering into the mat.
It is particularly useful in subsurface applications where water removal is desired. A large surface a.rea available for drainage is provided by the rectangular transverse cross-section of the drainage mat. The drainage mat of this invention is advantageously useful with traffic-carrying sur~ace~
for bearing traffic by motor vehicles, aircraft, rail conveyed vehicles and even pedestrians. Such use of this drainage mat is particularly advantageous in those installations where the drainage mat is installed such ~hat the laxger of its transverse cross-sectional dimensions is normal to an area to be drained. For instance the mat is useful in a vertical orientation as a traffic carrying surface edge drain such as a highway edge drain or as a joint drain for instance where two pavement seyments abut. In the vertical orientation the drainage ma~ is also useful in intercepting ground water flowing toward structure6 such as highway support beds, railroad support bed~, retaining walls, building foundations and subterranean walls and the like. Such an advantageous installation is in a highway sy~tem where the drainage ma~ is installed parallel to a road fox in tance in a vertical orientation under a highway shoulder joint.
In this regard Figure 4 illustrates a highway system cQmprising concrete pavement 41 with an adjoining ~houlder 42 which may be paved. The concre~e pavement 41 overlies a support bed 43~ The shoulder overlies support 440 In such an installation water infiltrating in a vertical direction through the highway shoulder joint 46 can be intercepted by ~:he
Faulting of 1/4 in. or more adversely affects the riding quality of the pavement system.
Methods for predicting and controlling water contents in pavement systems are well documented by Dempsey in 'IClim~tic Effects on Airport Pavement Systems~^State of the Art", Report No. FAA-RD-75-196 ~1976), United States Department of Defense and United States Department of Transportatisn. Methods for controlling moisture in pavement systems can generally be cla~sified in terms of protection through the use of waterpr~ofing membranes and anticapillary courses, the utilization of materials which are insensitive to moisture changes, and water evacuation by means of subdrainage.
Fiel~ investigations indicate tha~
evacuation by ~eans of a subdrainage system i5 often the preferred method for controlling water in pavement systems. In this regard proper selec~ion, design, ~nd con truction of the subdrainage system is important to the long-term pe~formance of a pavement. A highway subsurface drainage system should, among other functions, intercept or cut off the ~eepage above an impervious boundary, draw down or lowex the water ~ 3 ~ 4-table, and/or collect ~he flow from other drainage systems.
Exi~ting highway drains include a multitude of designs. Among the simplest ~re those which comprise a perorated pipe installed at the bottom of an excavated trench backfilled with sand or coarse aggregate. For instance, a standard drain specified by the State of Illinois re~uires a 4-inch di~neter perforated pipe be placed in the hottom of a trench 8 inches (20.3 cm~ wide by 30 inches (76 cm) deep. The trench is then backfilled with oarse sand meeting the State of Illinois standard FAl or FA2.
Such drains are costly to fabricate in terms of labor and materials. For instance the material excavated from the trench must be hauled to a disposal site, and sand b~ckfill must ~e purchased and hauled to the drain construction site.
Other types of dxains have attempted to avoid the use of the perforated pipe by utilizing a synthetic textile fabric as a trench liner. The fabric-lined trench is filled with a coarse aggregate which provides a support for the fabric. The ~oid space within the combined aggregate serves as a conduit for collected water which permeates the fabric. Such drains are costly to install, for instance in terms of labor to lay in and fold the fabric as well as in terms of haulage of excavated and backfill material. Moreover, there is considerable ' fabric area blocked ~y contact with the aggregate surface. This results in an increased hydraulic resistance through the fabric areas contacting the aggregate surface.
Other ~odifications to drai~age material include fabric c~vered perforated conduit, such as corrugated pipe as disclosed by Sixt et.al. in United States Patent 3,330,373 or raised surface pipe as disclosed by Uehara et.al. in United States Patent ~ ~ ~ Q 98 ~ -5- ~
4,182,581. A disadvantage is ~hat the planar surface area available for intercepting ~ubsurface water is limited to approximately the pipe di~meter unless the fabric covered perforated ~onduit is installed at the hottom of an interceptor trench fille!d, say, wlth coarse sand. A further disadvantage is that much of the fabric surface, say ~bout 50 perc:ent, is in contact with the conduit, thereby reclucing the effective collection area.
The problem of limited planar surface area for intercepting subsurface water is address~d by drainage products disclosed by Healy et.al. in United States Patents Nos. 3,563,038 and 3,654,765. Healy et.al. generally disclose a planar extended ~urface core covered with a filter fabric which serves as a water collector. One edge of the core terminates in a pipe-like cond~it for transporting collected water.
Among the configurations for the planar extended core are a s~uare-corrugated sheet and an expanded metal sheet. A major disadvantage of desi~ns proposed by Healy et.al. is that the drains are rigid and not bendable; this re~uires excavation of sufficiently long trenches that an entire length of drain can be installed. The pipe-like conduit reguires a wider trench than ~ight otherwise be needed. Moreover, the expanded metal sheet core does not provide adequate support to the fabric which can readily collapse again~t ~he opposing fabric surface, thereby greatly reducing the flow capacit~ within ~he core. Also the ~quare corrugated ~hee~ core is limited in that at least 50 percent of the fabric surface arc is occluded by the core, thereby reducing water collection area.
A related drainage material with extended surface is a two-layer composite of polyester non-woven filter fabric heat bonded to an expanded nylon ~on~woven matting, such as ENK~DRAINr foundation drai~aye material available from American Enka Company ~ ~3~9~ ~6 of En~a, North Carolina. The drainage material which can be rolled has ilter fabric on one side of the nylon non-woven matting. The drainage material serves as a collector only and requires installation of a conduit at the lower edge. This necessitates costly excavation of wide trenches, in addition to cost of conduit.
Another related drainage material with extended surface comprises a filter fabric covered core of cuspated polymeric sheet, such as STRIPDRAI~*
drainage product available from Nylex Corporation Limited of Victoria, Australia. The impervious cuspated polymeric sheet divides the core into two isolated opposing sections which keeps water collected on one side on that side. Moreover, in order that the drainage material be flexible, the core must be contained in a loose fabric envelope which, being unsupported on the core, can due to soil loading collapse into the core thereby hlocking flow channels.
2Q ~ The cuspated polymeric sheet i5 bendable only along two perpendicular axes in the plane of the sheet.
This makes installation somewhat difficult, for instance whole lengths must be inserted at once in an e~cavated trench.
A still further similar polymeric drainage product comprises a perforated sheet attached to 1at surfaces of truncated cones extending from an impervious sheet, su~h as CULDRAIN*board-shaped draining material available from ~itsui Petrochemical Industries, Ltd. The perforated sheet has holes in the range of O.S to 2.0 millimeters in diameter and allows fine and small particles to be leached from the subsurface ~oil.
The drainage materials available have one or more significant disadvantages, including economic disadvantages of re~uiring extensive amounts of labor for installation and performance disadvantages such as *Tracle r~arlc .
~ 9 ~
requirin~ separate conduit for removiny collected water.
This invention overcomet; mo~t if not all of the major disadvantages of such drainage materials.
For instance the drainage mat of this invention serves both as a collector, as well as a conduit for removing, intercepted ground water. The drainage mat of thi~ invention is flexible along any axis into one plane of its major longitudinal surface, this greatly facilitates installation of long lengths of drainage mat in incremental le~gths as trenches are excavated and backfilled within a short length. This provides a significant economic advantage in installation co~t when automatic installation equipment is utilized.
One embodiment of the drainage mat of this invention can, depending on hydraulic gradient, allow intercepted water to flow through any surface of the mat into a common conduit.
In the description of the present invention, the following definitions are used.
The term l'elongated drainage mat" as used in this ~pplication refers to a drainage mat having a length substantially larger than its width or depth.
The term "axis of elongation" as used in this application refers to the a~is passing through the center of an elongated drainage mat along its length.
The term "transverse rectangular cross sectionl' as used in this application refers to a cross section of an elongated drainage mat in a pl~ne normal to the axis of elongation of the drainage mat.
The term "pointing" as used in this application means a direction in which the axis o elongation of an elongated drainage mat i5 extended or aimed.
An elongated drainage mat is said to be "vertically-pointed" when the axis of elongatioll of ~ 3~ 8-the drainage mat is generally vertical with respect to the ~urface of the earth.
~ n elongated drai~age mat is ~aid to be "hori20ntally-pointed" when the axis of elongation of S the drainage mat is generally horizon.tal with respect to the ~urface of the earth.
The term "orientation" as used in this application refers to the attitude of an elongated drain ma~ having a rectangular txansverse cross ~ection determined by the relationship of the axes of the rectangular transverse cross section.
An elongated horizontally-pointed drainage mat having a rectangular transverse cross section is said to be "vertically-oriented" when the axis of tbe rectangular transverse cross section having the larger dimension is in a vertical position and the axis of the rectangular transverse cross section having the smaller dimension is in ~
horizontal position. The s2me drainaye mat, when rotated 90 around its axis of elongation, is ~aid to ~e "horizontally-oriented".
Among the useful parameters for characterizing fabric useful in the drainage mat of this invention i~ the coefficient of permeability which indicates the rate of water flow through a fabric material under a differential pressure between the two fabric ~urfaces e~pressed in terms of velocity, e.g., centimeters per second. Such coe~ficie~ts of permeability can be detenmined in accordance with American Soc~ety for Testing and Materials (ASTM) Standard D-737. Because of difficulties in determining the thickness of a fabric for use i~ determinlng a coefficient of permeability, it is often more convenient and meaningful to characterize fabric in terms of permittivity which is a ratio of the coefficient of permeability to fabric thickness, expressed in terms of velocity per o -9-thic]~ness, which reduces to inverse time, e.g., seconds 1. Permittivity can be determined in accordance with a procedure defined in Appendix A of Transportation Research Report 80-2, available from the United States Department of Transportation, Federal Highway Administration.
SUMM~RY OF THE INVENTION
This invention provides, in one aspect, a bendable drainage mat having a rectangular cross section. The drainage mat comprises a polymeric core having a flexible base layer with a plurality of substantially rigid fingers of substantially uniform height attached to only one side of the base layer and extending therefrom; and a water permeable fabric envel-oping the core and secured to a sufficient number of ends of the fingers such that the fabric does not unduly collapse. For convenience in installation the mat is often elongated.
So that the fabric does not unduly collapse in a flow-restricting manner into the conduit area of the mat it is generally desired that the fabric be secured to a sufficient number of the ends of the fingers. In most constructions the mat is bendable only such that the surface proximate the layer becomes convex.
This invention also provides a number of improved systems utilizing such drainage mat including, for instance, an improved highway system.
The invention, in another aspect, relates to a traffic carrying surface system comprising at least two pavement sections separated by an elongated joint and at least one vertically-oriented, elongated drainage mat having a rectangular transverse cross section installed below, in substantial alignment with, and proximate to the elongated joint, the elongated drainage mat comprising a polymeric core having a flexible base layer with a plurality of substantially rigid fingers attached to only one side of the base layer and e~tending therefrom and a water permeable fabric enveloping the core and secured to a sufficient number of ends of the fingers such that the fabric does not unduly collapse.
In accordance with another aspect of the present invention, there is provided a highway systern comprising a pavement section and a shoulder, positioned adjacent to the pavement section to form a joint therebetween, and a vertically-oriented, elongated, bendable drainage mat having a rectangular transverse cross section; wherein the drainage mat comprises a polymeric core having a flexible base layer with a plurality of substantially rigid fingers attached to only one side of the base layer and extending therefrom, and a water permeable fabric enveloping the core and secured to a sufficient number oE ends of the fingers such that the fabric does not unduly collapse; wherein the drainage mat has an upper edge positioned in substantial alignment with the joint, the edge being positione~ sufficiently close to the joint to intercept substantially all of any water passing through the joint to thereby prevent the water from spreading under the pavement section and shoulder.
BRIEF DESCRIPTION OF THE DRAWINGS
-FIGURE l illustrates an embodiment of a drainage mat accoraing to this invention.
FIGURE 2 illustrates an embodiment of a perforated layer having rod-like projections useful as 3a the three-dimensional core in a drainage ma-t according to this in~entionO
FIGVRE 3 illustrates a transverse cross-sectional view of a drainage mat.
FIGURE 4 schematically illustrates a cross-sectional view of a highway system with a drainage mat according to this invention installed proximate to a shoulder joint.
~3~
-lOa-FIGURE 5 schematically illustrates the position of bending axes with reference to the axis of elongation superimposed on the drainage mat surface which is proximate the ends of the fingers.
FIGURE 6 schematically illustrates -the characteristic of a drainage mat to change horizontal/vertical-pointing by rotating around a bending axis disposed at an angle of 45 from the axis of elongation.
FIGURE 7 schematically illustrates a partial cross-sectional view of continuous injection molding apparatus for producing polymeric core useful in the drainage mat.
FIGURE 8 illustrates a view of the surface of a useful core material opposite the side from which fingers extend.
FIGURE 9 is a schematic illustration of an artificial turf assembly utiliæing the drainage mat of this invention.
FIGURE 10 is a schematic illustration of a railroad system utilizing the drainage mat of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The elongated, bendable polymeric drainage mat having a rectangular transverse cross section comprises a polymeric core having a plurality of substantially rigid fingers extending from only one side of a base layer and an enveloping water permeable fabric. It is generally desirable that the fabric be secured to the core to avoid undesirable movement of the fabric relative to the core. For instance the fabric ~\
~3~)~38~
can be secured to the layer. In those instances when the layer is perforated, or otherwise permeable, the fabric 6hould totally e~elop ~he core including the perforated layer ~uch that perforations in the layer are covered by f~bric. To avoid occluding flow channels within the ~ore the fabric should also be secured to a ~ufficient number of ends of said fingers such that the fabric does not unduly collapse into space around the fingers. In some instances it may be sufficient that the fabric be secured to relatively few of the plurality of fingers, for instance less than 50 percent, ~ay even as low as 30 percen~ or even iO percent, of the flngers to avoid movement of the fabric relative to the ends of the fingers such that the fabric would unduly collapse into the space around the finger~ thereby occluding cross-sectional area otherwise available for fluid flow. In other cases it may be desirable that the fabric be secured to substantially all of the fingers to ensure that the structure of the drainage mat is maintained with a maximum t~ansverse cross-sectional area even after severe handl}ng, fGr instance in installation.
The drainage mats of this invention have unique properties characterized by a large surface area available for drainage, bendability for ease o~
installation, and a large open transverse cross-sectional area which serves as a conduit for allowing high multi-directional flow volumes for rapid evacuation of collected water.
A preferred form of t:he draina~e mat o thi~ invention is illustrated in Figures 1, 2 and 3.
In general, Figure 1 sc:hematically illustrates an embodiment of a section of drain~ge mat of this iT~vention where water permeable fabric 1 envelops core 2 having a plurality of substantially rigid fingers 4 extendi~g from one side of a layex 3. The axis of elonga~ion of the mat is indicated by axis 5.
~3~g8~
Figure 2 schematically illustrates an embodiment of a section of polymeric core useful in the drainage mat where the core has a p~urality of fingers 2~ extending from layer 23.
Figure 3 schematically illustrates a transverse cross section of drainage mat where fabric 31 envelops a core having a plurality of substantial].y rigid fingers 3~ extending from one side of a layer 33.
With reference to Figure 3, the drainage mat of this invention is readily bendable into the surface 35 proximate the ends 37 of the fingers 34. That is, the drainage mat is readily bendable only such that the surface 35 proximate the ends 37 of the f.ingers 3~
become concave, and the surface 36 proximate the layer 33 becomes convex. That is, the drainage mat is readily bendable such that spacing between the fingers at the base is substantially invariant and the spacing between the fingers at the end thereof can be decreased. In this regard the drainage mat can not be folded upon itself into the surface 36 proximate the layer 33 without an undue amount of force which is likely to tear the fabric or deform or collapse the core. This is especially the case when the fabric is bonded to the core. The mat is however readily bendable with little force such that the surface 35 proximate the ends 37 of the fingers 34 will readily and easily bend upon itself even up to about 1~0 around a bending axis having a radius of less than about 1 inch (2.54 cm), for instance as low as 0.25 inches ~0.63 cm). This bending lnto the surface proximate the ends of the fingers can be achieved around any bending axis parallel to the surface 35. In this regard ~igure 5 illustrates various bending axes superimposed on a drainage mat surface 56 proximate the ends of the fingers. Such bending axes are parallel to the surface 56 and are defined by their rotational ~rs~ disposition from axis of elongation 50 of the drainage ~` mat. A bending axis can be rotationally disposed at any angle from 0 to 180 from the axis of elongation ~3~8~) 50. For inst~nce the bending axis 51 is normal to the axis of elongation 50 (that i~, the :bending axis 51 i5 rotationally disposed at an angle of 90 from the axis of elongation 50). The drainage mat can be folded upon itself around bending axis 51 resulting in a shorter length; or such mat can be rolled into a short cylindrical spiral roll. The bending axis 52 is parallel to the axis of elongation 50 (that is, the bending axis ~2 is rotationally disposed at an angle of 0 from the axis of elongation 50). The drainage mat can be folded around bending axis 52 upon itself lengthwise or rolled into a long spiral roll.
~hen the drainage mat is folded upon itself up to about 180~ on a bending axis 53 which is rotationally disposed at an angle of 45 from the axis of elongation 50, the axis of elongation 50 o~ the drainage ~at will effect a 90 bend, as illustrated in Figure 6. This property of ~he drainage mat is particularly useful for those installations where the ~0 drainage mat 61 is to be installed below grade in a vertical orientation. In this regard the drainage mat can be provided in a vertical orientation above grade and guided to a roller 62 at an angle of 45. The drainage mat directed around such a roller 62 will be normal to a horizontal pl~n~ and can be guided to a second roller 63 at an angle of 45 at an elevation below grade. This second roller 63 will direct the drainage mat into a vertical orientation below grade in a position for its utilization.
Of course, rollers at other angles can be utilized to effect such changes in elevation.
Moreover, changes in horizontal positio~ can also be effected by rolIers disposed in horizontally parallel planes.
The drainage mat of this invention provides a large open tranverse cross-sectional area which provides little resistance to flow in any 3 ~ ~ ~O
~14- .
direction. A large ope~ transverse cros~-sectional area is provided by ~electing an optimum nu~ber of ~ubstantially rigid finger~ which provide the spaced-apart fabric suxfaces~
The core for use in the drainage mat of this invention is three-dimensional, having a plurality of substantially rigid ~ingers extending from one side of a layer. The layer can be impervious or perforated, depending on the intended use. When it is desira:~le that the drainage mat be capable of intercepting water from both major surfaces the layer should be perforated. A core with a perforated layer is illustrated in Figure 2 where layer 23 has a plurality of per~orations 25. Such perforations should be of sufficiently large area to allow water containing suspended solids to pass freely through the layer without pluggage by entrapped or bridged solids.
The fingers can comprise a very large group of shaped projections. As illustrated in Figure 2 a preferred finger is a r~d-like proje~tion which is cylindrical and projects in a direction normal to the plane of the layer. Fingers of other shapes can be utilized for instance fingers having square, hexagonal, star or oblong cross-sectional shape or with fin~, etc. Such shapes can be influenced by the mold desi~n utili~ed in the core forming process.
Al~hough solid fingers can be utilized, it is often desired that the fingers be hollow both for ease of fabrication and for minimizin~ the mass of the core to facilitate installation.
Regardless of shape, t~e fingers can be characterized as having a nominal diameter which is an average transverse dimension across the cross section of a finger. When the finger has a cylindrical shape normal to the plane of the base the nominal diameter is the diameter of the circular cross section; when the finger has some other geometric shape the nominal 1?~30980 diameter is an average transv2r6e dimension, for instance ~hen the finger is square ~haped the average transverse dimensio~ will be ~omewhat greater than a side of the ~quare but 60mewhat less than the diagonal of the ~guare. The nominal diameter dimension can be approximated by the average of the maximum and the minimum distance fro~ the center o~ the shape to a suxface.
In most instances it is preferred that fingers have a central axis which is normal ts the plane of the perforated layer. In other cases it may be desirable for fingers to project at some other angle from the perforated layer. ThP core can be characterized a~ having fingers which have a nominal diameter such that the ratio of the length of the fingers measured from the perforated layer to ~he end of the finger to the nominal diameter of the finger is in the range of from about 1:1 to about 8:1.
Tv provide a core with a maximum amount of cross-sectional area for fluid flow with the minimum resistance provided by fingers it is desirahle to provide a maximum spacing between fingexs.
~owever, fingers must not be spaced so far apart that the fabric will collapse into the space between fingers because of a lack of support. In this regard it is generally desired that the core be provided with an optimum spacing of fingers which can be characterized as an average center spacing, that is, the distance between centers of fin~ers intercepting the base. A~Prage center spacing can range from about 0.3 inches (0.76 cm~ to about 3 inches or more (7.6 cm)~ In many instances it is desired that the average center spacing range from 0.4 inches ~2.3 cm) to 1.25 inches (3.2 cm~.
Cores having utility in the drainage mat of this invention can have fingers with a length from about 0.125 inches (0.3 cm) to 3 inches or more ~7.6 ~3~80 16~
cm) in length and a nominal diameter of from about 0.1 inches ~0.25 cm) to 1.0 inch (2.54 cm~ or more.
However, it is often desired that the finger~ have ~
length from 0.5 inches ~1.3 cm) to 1.5 inches (3.8 cm) and a nominal diameter ~rom 0.15 inches (0.4 cm) to 0.5 inches (1.~ cm).
The depth of drainage mat will ~e approximated by the length of the fingers and the length can be very long, for instance up to about 400 feet (122 meters). The width of the drainage mat, that is, the larger dimension of its transverse rectangular cross section can range from 6 inches (15.2 cm) to more than 4 feet (122 cm~, say even up to 12 feet (365 cm) or more. The width will depend on the size of the apparatus used to fa~ricate the core.
Larger sizes can be fabricated by fastening two or more widths of core.
Drainage mats can be fabricated from a very large variety of polymeric materials. Among the preferred materials for the core are thermoplastic material6 such as polyethylene and polypropylene. For some uses, the preferred materials comprise low density polyethylene or linear low density polyethylene.
,25 Polymeric core useful in the drainage mat of this invention can be fabricated utilizing thermoplastic molding apparatus and processes well known to those skilled in such art. A preferred procedure for fabricating polymeric core having hollow cylindrical fingers is to utilize continuous molding apparatus as described by Doleman et.al. in U.S.
Patent 3,507~010.
Figure 7 illustrates a cross-sectional view of such continuous molding apparatus comprising a ~r 35 rotating cylindrical drum 70 having a plurality of '~ regularly spaced injection cavities 71. The cylindrical dr-~ 70 rotates in context with stationary ~ 17-injection head 74. The spacing of thle injection cavitie~ 71 ~ill correspond to the av~erage center ~pacing o ~he fingers exte~ding from o~e side of ~he core~ The cross-sectional 6hape of t.he injection cavities can be varied t~ produce fingers of a desired cross section, for instance circular, rectangular, star-shaped, etc. Such fingers can also be tapered, depending on the cavity design. Hollow fingers can also be produced by providing an annular injection cavity, as illustrated in Figure 7, where each injection caYity 71 is fitted with an insertion pin 72, having a reduced diameter extension 73. The length of the reduced diameter extension can be varied depending on the desired depth of the hollow bore within the finger.
Stationary injection head 74 has two rows of extension nozzles--high pressure nozz~es 76 and low pressure nozzles 75. The high pressure nozzles 76 provide molten thermoplastic material P from a pressurized reservoir 77 to the injection cavities 71 as they rotate into communication with the end of the high pressure nozzle 76. A high pressure nozzle 76 is aligned with each row of injection cavities 71 aligne~
around the circumference of the cylindxical drum 70.
The low pressure nozzles 75 are supplied with molten thermoplastic material P from the pressurized reservoir 77. Restrictors 78 in each low pressure nozzle reduce ~he pressure of the thermoplastic material ~xiting the end of each low pressure nozzle 3~ providing longitudinal stringers between rows of fingers .
Core geometry can be varied a~ desired by providing ~uch conti~uous injection molding apparatus with appropriate dimensions.
The enveloping water permeable fabric can comprise a wide variety of materials. Among the preferred fabric~ are those comprising polymeric ~`~ 3 ~
materials 6uch as polyethylene, polypropylene, polyamides, polyesters and polyacxyl:ic~. Other useful f~ric include~ glass fiber iEabric. In most in~tar~ces it is preferred Wlat the fabric comprise a hydrophobic material such as polypropylene or po:Lyester. Such fabric should be sufficiently water permeable that it exhibits a water permittivity in the range of from about O.2 seconds ~ to 2.0 seconds 1, More preferred fabrics axe those having a permittivity in ~he range of from about O.5 seconds 1 to about 1.0 ~econds The fabric can either be of a woven or non-woven manufacture; however non-woven fabrics are often generally preferred.
It is often desirable that the water permeable fabric envelop the entire core. When the layer is not perforated the fabric need only overlap the edges of the lay2r. ~owever, wh~n thç layex i~
perforated the fabric should entirely envelop the core. The fabric may be provided as a sock to ~lip 20 over the core. Alternatively the abric may be wrapped around the core such that there is an overlapping longitudinal seam to form the enveloping fabxic .
The fabric should of course be secured to 25 the core particularly to the ends of the fingers to avoid collapse of the iEabric into the conduit space of the core. A variety of me~hods of securing the fabric to the core may be employed. For instance, the fabric can be secured to the core by use of an adhesive, such ~s a hot melt adhesive. The fabric ca~ also be secured to the core by the use of mechanical fasteners or by sonic welding. Alternatively, the fabric c~n be secured to the ends of the fingers by causing the material of the ends of the finger6 to flow into the 3S fabric.
The drainage mat o~ this invention is u~eful in ~ny number of applications where it is ~L23~ 9 desirable to remove water from an area. ~or instance ~he mat can be u~ed in aguariums as a support for gravel. The penmeability of the fabric c~uld ~ary depending on whe~her filteriny would be desired.
The drainage mat can al~;o be advantageously utilized ~s a support for both natural and artificial turf. It is sometimes desirable to grow turf over a paved surface, f~r instance a patio or rooftop. The drainage mat of this invention can be laid in a horizontal orientation, preferably within a confined area, then covered with a layer of ~oil, such as loam, to support natural turf.
In many instances it is desirable to install artificial tur, such as synthetic grass-like playing surfaces, on a level surface. This has some disadvantages in outdoor installation which are subject to r~infall. Rainfall often accumulates on level in~tallations of artificial turf to the detriment of sport activities. The drainage mat o 2G this invention can be advantageously installed below the artificial turf, which is most o:Eten watex permeable, to collect and drain away rain wa~er. Even when installed on a level paved surface, the d~pth ~f the drainage mat will provide sufficient head to allow adequate water ~low over several hundred feet to drain connections. The drainage mat of this invention has sufficient strength to support playing activity including vehicle trsffic on the supported artifi~ial turf.
Reference is now made to Figure 9 which illustrates a cro~s-~ectional view of an artificial turf playing surface supported by a drainage mat in accordance with this invention. Artificial turf 91 is installed over a resilient mat 92 having a pluxality of perforations 93. The resilient mat ~2 is installed over a drainage mat 94, according to this invention.
The drainage mat can be installed with the layer ~ 8~ -20-against a supporting smooth surface 95; alternatively, if the layer is perforated, the drainage mat can be installed with the layex aqainst the re~ilient mat 92.
In some instances ~he dxainage mat can be utilized withol~t an enveloping water permeable fabric, for instance when the drainage mat is installed over concrete pavement or the like. However, when the drainage mat is installed over soil it is desirable to utilize an enveloping fabric to prevent water saturated soil from entering into the mat.
It is particularly useful in subsurface applications where water removal is desired. A large surface a.rea available for drainage is provided by the rectangular transverse cross-section of the drainage mat. The drainage mat of this invention is advantageously useful with traffic-carrying sur~ace~
for bearing traffic by motor vehicles, aircraft, rail conveyed vehicles and even pedestrians. Such use of this drainage mat is particularly advantageous in those installations where the drainage mat is installed such ~hat the laxger of its transverse cross-sectional dimensions is normal to an area to be drained. For instance the mat is useful in a vertical orientation as a traffic carrying surface edge drain such as a highway edge drain or as a joint drain for instance where two pavement seyments abut. In the vertical orientation the drainage ma~ is also useful in intercepting ground water flowing toward structure6 such as highway support beds, railroad support bed~, retaining walls, building foundations and subterranean walls and the like. Such an advantageous installation is in a highway sy~tem where the drainage ma~ is installed parallel to a road fox in tance in a vertical orientation under a highway shoulder joint.
In this regard Figure 4 illustrates a highway system cQmprising concrete pavement 41 with an adjoining ~houlder 42 which may be paved. The concre~e pavement 41 overlies a support bed 43~ The shoulder overlies support 440 In such an installation water infiltrating in a vertical direction through the highway shoulder joint 46 can be intercepted by ~:he
5 narrow transverse cross-sectional area at th~ top of the drainage mat 45, water present under the his~hway can be intercepted by the lar~e transverse cross-sectional area which is normal to the highway support bed, and the opposing large transverse cross-sectional area can intexcept ground water approaching the highway from the outside. All such ihtercepted water can be carried away as soon as it is collected by the drainage mat.
In other installations where it is desired to maintain a moisture level in a highway support bed, a drainage mat with an impervlous layer can be installed with the impervious layer in contact with the vertical edge of the support hed to prevent the flow of ground water either into or out of ~he support bed. The drainage mat can intercept and carry away ground water which could otherwise enter the support bed.
The drainage mat is also advantageously useful in railroad systems when installed in a 25 horizontal orientation for instance below or within ballast. Figure 10 schematically illustrates such an installation where a pair of rails 96 lie on cross-ties 97 which are supported by ballast 98.
Drainage mat 99 according to this invention can lie 30 below or within the ballast to stabilize the railroad system by intercepting and carrying away rain w~ter which would allow ballast and soil to intermix undermining the ~upport.
The drainage mat of this invention is 35 readily installed with simple connectors and transition pieces. For instance, rectangular molded couplings fitting over the terminals of ~he drainage ~ 22-mat can readily 6plice two lengths of drainage mat.
Transition pieces adapted to intercept the bottom edge of the drainage mat can be utilized to connect the drai~age mat to standard circular conduit or pipe for conveying collected water away from ~he drainaqe mat to a sewer or drain system~
This invention is further illustrated by, but not limited to, the following exc~mples.
EXAMPLE I
An apparatus for producing continuou~
lengths of three-dimen ional molded products composed of a matrix having projections extending from one surface as described in United States Patent No.
3,507,010, was designed to produce an artificial grass-like material. The apparatus comprises a cylindrical drum provided with a multitude of equally spaced rows of cavitles, for instance on one-half inch centers. Fluted insertion pins were press~fitted into the cavities to selectively limit the penetration of injected polymer melt into the drum and thus control the height of the projections formed from the polymer.
In one-fourth of the cavities the fluted insertion pins were replaced with insertion pins having a reduced diameter extension forming an annular mold space within the injection cavity. The aDnular mold space had an outer diameter of about ~ inch tO.64 cm), an inner diameter o about 3/16 inch (0.48 cm~ and a length of ab~ut 1 i~ch (2.54 cm). The remaining threeofourths of the cavities were plugged with fill pins. The pin modifications resulted in a cylindrical drum having annular injection cavities on 1 inch centers.
Lineax low density polyeth~lene pellets were melted and fed under hydraulic pressure from a screw extruder into the distributing nQzzle of the ~ 3 ~ 23-apparatus having two rows of holes which directed polymer into the cavities and grooves of the cylindrical drum. The first row of holes in contact with the rotating cylindrical drum ~upplied polymer to the annular mold cavities as well as the b~inded cavities. The second row of holes supplied polymer to stringer grooves in the drum. Stationary finger~
lying in grooves of ~he cylindrical drum isolated each cavity while molding took place, thus creating a zone of high pressure which allowed full depth penetration into the annular mold cavities as well as a short pillar piece in ~he blinded cavities. Polymer was deposited in the stringer grooves at a pressure slightly above atmospheric to control the amount of polymér fed to each groove. By adjusting the restricters it was possible to obtain a balance of molding pres~ures to completely fill the annular mold cavities and produce stringers flush with the surface of the cylindrical drum.
The shape of the molded product is illustrated ~chematically in Figure 2 which shows a perforated layer having a plurality of hollow cylinders e~tending from one surfa~e of the layer.
The cylinders had a length of 1 inch (2.54 cm~, an outer diameter of about 15 inch (0.64 cm), and an inner diameter o~ about 3/16 inch (O.48 cm). The cylinders were spaced at about 1 inch ~2.54 cm) centers with two rows of stringers extending between rows of cylinders in the longitudinal direction. Circular plugs provided connectors between stringers on ~ inch (1.27 cm) centers as illu~trated in Figure Z. This provided a continuou~ layer having butterfly shaped perforations as illustrated in Figure 8 which is a bottom view of the molded core. The molded core was provided in a width o about 6 inches (15.24 cm) wi~h a continuous length. The core can be cut into any desired length, fvr instance as short as 5 feet (1.5 --~ 3~ 24 meters) or le~s or as long as 400 feet (122 ~eters) or more.
E ~ LE II
A 2 foot x 4 foot (0.61 m x 1.22 m) section of core material was fabricated from molded core material as produced in Example I. A drainage mat was produced by enveloping the section of core with a water pexmeable fabric which was secured to the back side of the perforated sheet and to ~he ends of the hollow cylinders with a hot melt adhesive. The water permeable fabric was a non-woven polypropylene fabric available from Amoco Fabrics Company under the trade name PROPAX 4545 Soil Filtration Fabric. Such fabric is specified as having the following properties: tensile stxeng~h of 90 lbs. as determined by American Society for Testing and Material~ (ASTM), standard test method D-1682; elongation of 60 percent, as determined by ASTM-D-1682; burst strength of 230 psi as determined by Mullen Burst Test; accelerated weathering strength retained of 70 percent, as determined by Fed~ral Test Method CCC-T-l91, method 5804 (500 hours exposure); equivalent opening size ~f 70 (minimum equivalent U.S. Sieve No,~, as determined as CW-02215; and a permeability coefficient of 0.2 cm/sec, as determined by a falling head method from 7 mm to 25 mm~
The fabric was also deter~ined to have a permittivity per fabric layer of 0.75 cm/sec, as determined by the test method defined in Appendix A of Transportation Research Report 80-2 available from U~ited States Department of Transportation, Federal Highway Administration.
~3~ 2S-EXA~LE I I I
The drainage mat prepaxeld in Exa~ple II
was installed in a lysimeter for outflow studies to eYaluate its drainage performance. The lysimeter consi~ted of a large water-proof box 96 inches ( 244 cm) long, 48 inches (122 cm) deep and 48 inches (122 cm ) wide O The top of the box was open . The box was filïed to a depth of 3 feet ( 91 . 4 cm ~ with a comp~ted subgrade soil characterized by AlTerican ~ssociation of State ~ighway Transportation Officials ~AASHTO) cla~sification system A-7-6. Eight inch (20.3 cm) wide ~lots were then eaccavated in the subgrade material to a depth of 2 feet ( 61 cm) . An outflow pipe was installed through the side wall of the water-proof box to intercept the excavated slot at the base. The drainage mat was installed in a vertical orientation with the surface of the mat pro~imate ~e perforated base lying against the side wall of the slot. The lower 12 inches (30.5 cm) of the slot was refilled with compacted subgrade soil (AASHTO A-7-6).
The remainder of the slot as well as the 6 inches ~15 . 2 cm ~ above the 3 foot ( 91. 4 cm ) depth of compacted subgrade soil ~AAS~TO A-7 6) was filled with a coarse sand material (AASHTO A 1-B ) .
To conduct the outflow studies a head of water wa~ maintained in the lysimeter at a level 5 inches above the surface of the coar~e sand material.
Water flowing rom the outfl~w pipe was measured periodically to determine an outflow rate.
Instantaneous outflow rates, measured in units of gallons per day, were recoxded after various elapsed time, measured in units of days. These outflow ~ates are tabulated in Table 1.
~23~8C~ -26-Insl:antaneous ~ Ou l:i low Rate ( gal/day ) ~ m3/day ) 1 day 297 1.12 2 days 232 0 . 88 days 449 1. 70 days 3~0 1. 32 days 281 1. 06 100 days 272 1. 03 155 days 228 0 . 86 EXAE~LE IV
This example illustrates the load deflection resistance of the drainage mat produced in Example I I . A section of drainage mat fabricated in accordance with E~ample I I was laid in a horizontal orientation with the sur:Eace proximate the perforated 20 layer in contact with a base. An open bottom/open top rectangular bo~ having inside diDIensions of 4 inches tlO.2 cm) and 5~ inche~ (14.0 cm) was pla;::ed on the drainage mat surface pro~imate the ends of the cylind~rs. The box was partially filled with AAS~0 A-7-6 soil which was covered by a 4 inch by 535 inch ~10.2 cm x 14.0 cm) steel compressiorl plate. Guide casirlgs were installed through hvles in ~he compression plate through the soil to contact the surface of the drainage mat. One guide casing was 3V installed on the fabric above a cylinder; another guide casing was installed on the fabric betweell ~2~ 38~ -27-cylinders. Extension pirlS fxom dial gauges were passed through the guide casings to the fabric surace. As the load on the compres~ion plate was increa~ed in increment6 of 100 l~f (0.445 ~). the S deflection of the surface of the drai.nage mat was measured by the dial gauges. The results of this load deflection test are tabulated in Table 2.
LOAD DEFLECTION TEST
AppliedUnitFabric Fabric Load PressureDeflectionl Deflection2 (kN) (kPa) (mm) (mD) .4 31 O.lS 0.0 .9 63 0.36 0.0 1.3 ~4 0.41 0.0 1.8 125 0.43 û.0 2 . 2 157 û . 53 0 . O
2.7 188 0.53 0.0 3.1 219 ~.58 0.0 3.6 251 0.58 0.0 4 . 0 282 0 . 64 0 . 0 4.5 313 0.74 0.0 4.9 345 0.74 0.0 5.3 376 0.76 O.û
5.8 ~07 0.76 0.0
In other installations where it is desired to maintain a moisture level in a highway support bed, a drainage mat with an impervlous layer can be installed with the impervious layer in contact with the vertical edge of the support hed to prevent the flow of ground water either into or out of ~he support bed. The drainage mat can intercept and carry away ground water which could otherwise enter the support bed.
The drainage mat is also advantageously useful in railroad systems when installed in a 25 horizontal orientation for instance below or within ballast. Figure 10 schematically illustrates such an installation where a pair of rails 96 lie on cross-ties 97 which are supported by ballast 98.
Drainage mat 99 according to this invention can lie 30 below or within the ballast to stabilize the railroad system by intercepting and carrying away rain w~ter which would allow ballast and soil to intermix undermining the ~upport.
The drainage mat of this invention is 35 readily installed with simple connectors and transition pieces. For instance, rectangular molded couplings fitting over the terminals of ~he drainage ~ 22-mat can readily 6plice two lengths of drainage mat.
Transition pieces adapted to intercept the bottom edge of the drainage mat can be utilized to connect the drai~age mat to standard circular conduit or pipe for conveying collected water away from ~he drainaqe mat to a sewer or drain system~
This invention is further illustrated by, but not limited to, the following exc~mples.
EXAMPLE I
An apparatus for producing continuou~
lengths of three-dimen ional molded products composed of a matrix having projections extending from one surface as described in United States Patent No.
3,507,010, was designed to produce an artificial grass-like material. The apparatus comprises a cylindrical drum provided with a multitude of equally spaced rows of cavitles, for instance on one-half inch centers. Fluted insertion pins were press~fitted into the cavities to selectively limit the penetration of injected polymer melt into the drum and thus control the height of the projections formed from the polymer.
In one-fourth of the cavities the fluted insertion pins were replaced with insertion pins having a reduced diameter extension forming an annular mold space within the injection cavity. The aDnular mold space had an outer diameter of about ~ inch tO.64 cm), an inner diameter o about 3/16 inch (0.48 cm~ and a length of ab~ut 1 i~ch (2.54 cm). The remaining threeofourths of the cavities were plugged with fill pins. The pin modifications resulted in a cylindrical drum having annular injection cavities on 1 inch centers.
Lineax low density polyeth~lene pellets were melted and fed under hydraulic pressure from a screw extruder into the distributing nQzzle of the ~ 3 ~ 23-apparatus having two rows of holes which directed polymer into the cavities and grooves of the cylindrical drum. The first row of holes in contact with the rotating cylindrical drum ~upplied polymer to the annular mold cavities as well as the b~inded cavities. The second row of holes supplied polymer to stringer grooves in the drum. Stationary finger~
lying in grooves of ~he cylindrical drum isolated each cavity while molding took place, thus creating a zone of high pressure which allowed full depth penetration into the annular mold cavities as well as a short pillar piece in ~he blinded cavities. Polymer was deposited in the stringer grooves at a pressure slightly above atmospheric to control the amount of polymér fed to each groove. By adjusting the restricters it was possible to obtain a balance of molding pres~ures to completely fill the annular mold cavities and produce stringers flush with the surface of the cylindrical drum.
The shape of the molded product is illustrated ~chematically in Figure 2 which shows a perforated layer having a plurality of hollow cylinders e~tending from one surfa~e of the layer.
The cylinders had a length of 1 inch (2.54 cm~, an outer diameter of about 15 inch (0.64 cm), and an inner diameter o~ about 3/16 inch (O.48 cm). The cylinders were spaced at about 1 inch ~2.54 cm) centers with two rows of stringers extending between rows of cylinders in the longitudinal direction. Circular plugs provided connectors between stringers on ~ inch (1.27 cm) centers as illu~trated in Figure Z. This provided a continuou~ layer having butterfly shaped perforations as illustrated in Figure 8 which is a bottom view of the molded core. The molded core was provided in a width o about 6 inches (15.24 cm) wi~h a continuous length. The core can be cut into any desired length, fvr instance as short as 5 feet (1.5 --~ 3~ 24 meters) or le~s or as long as 400 feet (122 ~eters) or more.
E ~ LE II
A 2 foot x 4 foot (0.61 m x 1.22 m) section of core material was fabricated from molded core material as produced in Example I. A drainage mat was produced by enveloping the section of core with a water pexmeable fabric which was secured to the back side of the perforated sheet and to ~he ends of the hollow cylinders with a hot melt adhesive. The water permeable fabric was a non-woven polypropylene fabric available from Amoco Fabrics Company under the trade name PROPAX 4545 Soil Filtration Fabric. Such fabric is specified as having the following properties: tensile stxeng~h of 90 lbs. as determined by American Society for Testing and Material~ (ASTM), standard test method D-1682; elongation of 60 percent, as determined by ASTM-D-1682; burst strength of 230 psi as determined by Mullen Burst Test; accelerated weathering strength retained of 70 percent, as determined by Fed~ral Test Method CCC-T-l91, method 5804 (500 hours exposure); equivalent opening size ~f 70 (minimum equivalent U.S. Sieve No,~, as determined as CW-02215; and a permeability coefficient of 0.2 cm/sec, as determined by a falling head method from 7 mm to 25 mm~
The fabric was also deter~ined to have a permittivity per fabric layer of 0.75 cm/sec, as determined by the test method defined in Appendix A of Transportation Research Report 80-2 available from U~ited States Department of Transportation, Federal Highway Administration.
~3~ 2S-EXA~LE I I I
The drainage mat prepaxeld in Exa~ple II
was installed in a lysimeter for outflow studies to eYaluate its drainage performance. The lysimeter consi~ted of a large water-proof box 96 inches ( 244 cm) long, 48 inches (122 cm) deep and 48 inches (122 cm ) wide O The top of the box was open . The box was filïed to a depth of 3 feet ( 91 . 4 cm ~ with a comp~ted subgrade soil characterized by AlTerican ~ssociation of State ~ighway Transportation Officials ~AASHTO) cla~sification system A-7-6. Eight inch (20.3 cm) wide ~lots were then eaccavated in the subgrade material to a depth of 2 feet ( 61 cm) . An outflow pipe was installed through the side wall of the water-proof box to intercept the excavated slot at the base. The drainage mat was installed in a vertical orientation with the surface of the mat pro~imate ~e perforated base lying against the side wall of the slot. The lower 12 inches (30.5 cm) of the slot was refilled with compacted subgrade soil (AASHTO A-7-6).
The remainder of the slot as well as the 6 inches ~15 . 2 cm ~ above the 3 foot ( 91. 4 cm ) depth of compacted subgrade soil ~AAS~TO A-7 6) was filled with a coarse sand material (AASHTO A 1-B ) .
To conduct the outflow studies a head of water wa~ maintained in the lysimeter at a level 5 inches above the surface of the coar~e sand material.
Water flowing rom the outfl~w pipe was measured periodically to determine an outflow rate.
Instantaneous outflow rates, measured in units of gallons per day, were recoxded after various elapsed time, measured in units of days. These outflow ~ates are tabulated in Table 1.
~23~8C~ -26-Insl:antaneous ~ Ou l:i low Rate ( gal/day ) ~ m3/day ) 1 day 297 1.12 2 days 232 0 . 88 days 449 1. 70 days 3~0 1. 32 days 281 1. 06 100 days 272 1. 03 155 days 228 0 . 86 EXAE~LE IV
This example illustrates the load deflection resistance of the drainage mat produced in Example I I . A section of drainage mat fabricated in accordance with E~ample I I was laid in a horizontal orientation with the sur:Eace proximate the perforated 20 layer in contact with a base. An open bottom/open top rectangular bo~ having inside diDIensions of 4 inches tlO.2 cm) and 5~ inche~ (14.0 cm) was pla;::ed on the drainage mat surface pro~imate the ends of the cylind~rs. The box was partially filled with AAS~0 A-7-6 soil which was covered by a 4 inch by 535 inch ~10.2 cm x 14.0 cm) steel compressiorl plate. Guide casirlgs were installed through hvles in ~he compression plate through the soil to contact the surface of the drainage mat. One guide casing was 3V installed on the fabric above a cylinder; another guide casing was installed on the fabric betweell ~2~ 38~ -27-cylinders. Extension pirlS fxom dial gauges were passed through the guide casings to the fabric surace. As the load on the compres~ion plate was increa~ed in increment6 of 100 l~f (0.445 ~). the S deflection of the surface of the drai.nage mat was measured by the dial gauges. The results of this load deflection test are tabulated in Table 2.
LOAD DEFLECTION TEST
AppliedUnitFabric Fabric Load PressureDeflectionl Deflection2 (kN) (kPa) (mm) (mD) .4 31 O.lS 0.0 .9 63 0.36 0.0 1.3 ~4 0.41 0.0 1.8 125 0.43 û.0 2 . 2 157 û . 53 0 . O
2.7 188 0.53 0.0 3.1 219 ~.58 0.0 3.6 251 0.58 0.0 4 . 0 282 0 . 64 0 . 0 4.5 313 0.74 0.0 4.9 345 0.74 0.0 5.3 376 0.76 O.û
5.8 ~07 0.76 0.0
6.2 439 1.07 0.0 6 . 7 470 1 . 24 1 . 75
7.1 501 2.01 1.88 7.6 533 2.g7 2.39
8 . 0 564 3 . 12 2 . 39 8 . ~ 5~5 3 ~ 28 2 . 57 8 . ~ 620 4 . 42 `4 . 3 1: measured between cyli~ders 2: measured over qrlinder ~ hile the invention has been described herein with regard to certain specific embodiments, it is not so limited. It is to be understood that variations and modifications thereof may be made by ~L~3C)~
those skilled in the art s~ithout depa:rting frora the ~pirit and scope of the invention.
those skilled in the art s~ithout depa:rting frora the ~pirit and scope of the invention.
Claims (12)
1. An elongated bendable drainage mat having a rectangular transverse cross section, said drainage mat comprising:
a polymeric core having a flexible base layer with a plurality of substantially rigid fingers of substantially uniform height attached to only one side of said base layer and extending therefrom; and a water permeable fabric enveloping said core and secured to a sufficient number of ends of said fingers such that the fabric does not unduly collapse.
a polymeric core having a flexible base layer with a plurality of substantially rigid fingers of substantially uniform height attached to only one side of said base layer and extending therefrom; and a water permeable fabric enveloping said core and secured to a sufficient number of ends of said fingers such that the fabric does not unduly collapse.
2. The mat of Claim 1 which is readily bendable only such that the surface of the drainage mat proximate the ends of the fingers can be concavely rolled over any bending axis, which is parallel to the plane of the layer and rotationally disposed at any angle from 0 to 180° from the axis of elongation of the mat.
3. The mat of Claim 2 wherein the surface of the drainage mat proximate the ends of the fingers can be concavely rolled up to 180° over a bending axis having a diameter of less than about 1.0 inch.
4. The mat of Claim 3 wherein the fingers have a nominal diameter such that the ratio of length of the fingers to nominal diameter is in the range of 1:1 to 8:1.
5. The mat of Claim 4 wherein the fingers have an average center spacing from one another such that the ratio of average center spacing to nominal diameter is 2:1 to 20:1.
6. The mat of Claim 5 wherein the fingers have a length from 1.3 to 3.8 centimeters, a nominal diameter from 0.4 to 1.1 centimeters and an average center spacing from 2.3 to 3.2 centimeters, wherein the rectangular transverse cross section has a long dimension from 15 centimeters to 3.6 meters.
7. The drainage mat of Claim 1 which is readily bendable such that spacing between said fingers at the base is substantially invariant and the spacing between said fingers at the ends thereof can be decreased.
8. The mat of Claim 1 wherein said fabric is secured to substantially all of the ends of said fingers.
9. A traffic carrying surface system comprising at least two pavement sections separated by an elongated joint and at least one vertically-oriented, elongated drainage mat having a rectangular transverse cross section installed below, in substantial alignment with, and proximate to said elongated joint, said elongated drainage mat comprising a polymeric core having a flexible base layer with a plurality of substantially rigid fingers attached to only one side of said base layer and extending therefrom and a water permeable fabric enveloping said core, and secured to a sufficient number of ends of said fingers such that the fabric does not unduly collapse.
10. A highway system comprising a pavement section and a shoulder, positioned adjacent to said pavement section to form a joint therebetween, and a vertically-oriented, elongated, bendable drainage mat having a rectangular transverse cross section; wherein said drainage mat comprises a polymeric core having a flexible base layer with a plurality of substantially rigid fingers attached to only one side of said base layer and extending therefrom, and a water permeable fabric enveloping said core and secured to a sufficient number of ends of said fingers such that the fabric does not unduly collapse; wherein said drainage mat has an upper edge positioned in substantial alignment with the joint, said edge being positioned sufficiently close to said joint to intercept substantially all of any water passing through said joint to thereby prevent said water from spreading under said pavement section and shoulder.
11. The highway system of Claim 10 comprising a drainage mat which is readily bendable only such that the surface of the drainage mat proximate the ends of the fingers can be concavely rolled over any bending axis, which is parallel to the plane of the layer and rotationally disposed at any angle from 0 to 180° from the axis of elongation of the mat and has a diameter of less than about 1.0 inch.
12. The highway system of Claim 11 comprising a drainage mat wherein the fingers are cylindrical and have a length from 1.3 to 3.8 centimeters, a nominal diameter from 0.4 to 1.1 centimeters and an average center spacing from 0.8 to 8.0 centimeters.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US48110483A | 1983-03-31 | 1983-03-31 | |
| US481,104 | 1983-03-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1230980A true CA1230980A (en) | 1988-01-05 |
Family
ID=23910621
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000451022A Expired CA1230980A (en) | 1983-03-31 | 1984-03-30 | Elongated bendable drainage mat |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1230980A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5688073A (en) * | 1993-06-11 | 1997-11-18 | Brodeur; Joseph Clement | Earth drains |
| US6786013B2 (en) * | 2000-06-14 | 2004-09-07 | Benjamin Obdyke Incorporated | Building structure and spacer used therein |
-
1984
- 1984-03-30 CA CA000451022A patent/CA1230980A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5688073A (en) * | 1993-06-11 | 1997-11-18 | Brodeur; Joseph Clement | Earth drains |
| US6786013B2 (en) * | 2000-06-14 | 2004-09-07 | Benjamin Obdyke Incorporated | Building structure and spacer used therein |
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