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United States Patent |
5,336,544
|
Bach
,   et al.
|
August 9, 1994
|
Reinforced cell material
Abstract
A cell material structure for confinement of concrete and earth material,
having a plurality of plastic strips bonded together on their faces in a
side by side relationship at bonding areas which are staggered from strip
to strip such that the plurality of strips may be stretched in a direction
perpendicular to the faces of the strips to form a web of cells, the
strips forming cell walls. At least one of the strips has an aperture
through which a reinforcing member extends. Preferably, the reinforcing
member is a tendon made of a polymer having a nominal breaking strength of
from about 100 to about 2,500 lb.
Inventors:
|
Bach; Gary M. (Appleton, WI);
Crowe; Robert E. (Milton, CA)
|
Assignee:
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Reynolds Consumer Products Inc. (Appleton, WI)
|
Appl. No.:
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019101 |
Filed:
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February 18, 1993 |
Intern'l Class: |
B32B 003/12 |
Field of Search: |
428/116,117,184,188
52/806,807
405/258
160/84.1 D
|
References Cited
U.S. Patent Documents
3990247 | Nov., 1976 | Palmer | 428/116.
|
4469756 | Sep., 1984 | Jungwirth et al. | 428/364.
|
4502815 | Mar., 1985 | Scales et al. | 405/17.
|
4647325 | Mar., 1987 | Bach | 156/73.
|
4648224 | Mar., 1987 | Kitta et al. | 428/272.
|
4675060 | Jul., 1987 | Schnebly et al. | 156/65.
|
4717283 | Jan., 1988 | Bach | 405/17.
|
4778309 | Oct., 1988 | Bach et al. | 428/117.
|
4856939 | Aug., 1989 | Hilfiker | 405/284.
|
4965097 | Oct., 1990 | Bach | 428/194.
|
5091247 | Feb., 1992 | Willibey et al. | 428/255.
|
Primary Examiner: Epstein; Henry F.
Attorney, Agent or Firm: McDonald; Alan T.
Claims
We claim:
1. In a cell material structure for confinement of concrete and earth
material, comprising:
a plurality of plastic strips bonded together on their faces in a side by
side relationship at bonding areas which are staggered from strip to strip
such that the plurality of strips may be stretched in a direction
perpendicular to the faces of the strips to form a unitary web of cells,
the strips forming cell walls,
the improvement wherein adjacent strips of the plurality of strips have
apertures, and reinforcing means extending through said apertures of said
adjacent strips.
2. The cell material structure of claim 1 wherein the reinforcing means is
a tendon comprised of a material having a nominal breaking strength of
from about 100 to about 2,500 lb.
3. The cell material structure of claim 2 wherein an outer surface of the
tendon is enclosed by an acid and alkali resistant material.
4. The cell material structure of claim 1 further including means for
terminating the reinforcing means on an end of the web.
5. The cell material structure of claim 4 wherein the reinforcing means is
a tendon and the terminating means is a loop of the tendon, or a washer
and a knot of the tendon.
6. In a cell material structure for confinement of concrete and earth
material, comprising:
a plurality of plastic strips bonded together on their faces in a side by
side relationship at bonding areas which are staggered from strip to strip
such that the plurality of strips may be stretched in a direction
perpendicular to the faces of the strips to form a unitary web of cells,
the strips forming cell walls,
the improvement wherein each of the cell walls has an aperture, and wherein
said cell material structure includes means for reinforcing the unitary
web, the reinforcing means extending through the aperture of each of the
cell walls.
7. The cell material structure of claim 6 wherein the reinforcing means is
a tendon comprised of a material having a nominal breaking strength of
from about 100 to about 2,500 lb.
8. The cell material structure of claim 7 wherein the material is a
polymer.
9. The cell material structure of claim 7 wherein an outer surface of the
tendon is enclosed by an acid and alkali resistant material.
10. The cell material structure of claim 9 wherein the acid and alkali
resistant material is a polymer.
11. The cell material structure of claim 6 further including means for
terminating the reinforcing means on an end of the web.
12. The cell material structure of claim 11 wherein the reinforcing means
is a tendon and the terminating means is a loop of the tendon, or a washer
and a knot of the tendon.
13. The cell material structure of claim 6 wherein the apertures are
positioned adjacent the bonding areas, the apertures being substantially
coincident.
14. The cell material structure of claim 6 wherein the apertures are
positioned below a midpoint of the faces of the strips.
15. The cell material structure of claim 6 wherein the apertures are
positioned about a midpoint of the faces of the strips.
Description
FIELD OF THE INVENTION
The present invention relates to a reinforced cell material for confinement
of concrete and earth materials. Specifically, the present invention
relates to a cell web material which is reinforced with tendons to prevent
unwanted displacement of the web material during installation and
operation.
BACKGROUND OF THE INVENTION
Cellular confinement systems serve to increase the load bearing capacity,
stability and erosion resistance of materials which are placed within the
cells of the system. A commercially available system is Geoweb.RTM.
plastic web soil confinement system, sold by Presto Products,
Incorporated, P.O. Box 2399, Appleton, Wis. 54913. Geoweb.RTM. cells are
made from high density polyethylene strips which are joined by ultrasonic
seams on their faces in a side by side relationship at alternating
spacings so that when the strips are stretched out in a direction
perpendicular to the faces of the strips, the resulting web section is
honeycomb-like in appearance, with sinusoidal or undulant shaped cells.
Geoweb.RTM. sections are light-weight and are shipped in their collapsed
form for ease in handling and installation.
The web materials have been used extensively to provide road bases,
subgrades or pavement systems. Structural foundations have been reinforced
or stiffened with the web materials. Additionally, Geoweb.RTM. cells have
been used to provide earth and liquid retention structures by stacking one
web layer upon another, such as a stepped back design for hill slope
retention. The Geoweb.RTM. cells also protect earth slopes, channels,
revetments and hydraulic structures from surface erosion. Grass and other
earth slope cover materials have been protected and stabilized through the
use of the web cells. Geoweb.RTM. cells can be infilled with various earth
materials such as sand, rounded rock, granular soils and aggregates,
topsoil, vegetative materials and the like. Concrete and soil-cement or
asphaltic-cement can also be used to infill the cells.
During installation and long-term operation of the web materials, the fill
material and the webs may be displaced. Erosion below the web material may
cause concrete infill to drop out of the cells. Concrete cannot be
pre-cast in the web materials because the concrete fill would drop out of
the cells as it was lifted and moved to the installation site. Applied
forces such as hydraulic uplift and ice action may lift the web material
or lift the fill material out of the cells. Translational movement of the
webs may occur in channel lining applications, or when surface protection
on steep slopes slides.
In an effort to overcome these problems, J hooks have been intermittently
spaced along the face of some cell walls and driven into the ground to
anchor the web material before the cells are infilled. The rounded
portions of the J hooks extend over the tops of the cell walls to limit
displacement of the web material. While this approach has limited
displacement of the web materials in some applications, it has not been
completely successful in preventing movement of the webs.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide an improved
cellular web material which is reinforced to minimize displacement of the
web or fill material during installation and long-term operation. In this
connection, a related object of this invention is to provide such an
improved cellular material which resists hydraulic uplift, ice action, and
translational movement.
Another important object of this invention is to provide a reinforced
cellular web material which anchors poured-in-place concrete fill material
within the cells to prevent displacement of the concrete from the cell and
facilitate movement of the concrete infilled web material.
Yet another object of the invention is to provide a cellular web material
reinforced by tendons having long term durability and optimum
load-deformation characteristics and long-term creep performance.
The present invention provides a cell material structure for confinement of
concrete and earth material, having a plurality of plastic strips bonded
together on their faces in a side by side relationship at bonding areas
which are staggered from strip to strip such that the plurality of strips
may be stretched in a direction perpendicular to the faces of the strips
to form a web of cells, the strips forming cell walls. At least one of the
strips has an aperture through which a reinforcing member extends.
In a preferred embodiment, each of the cell walls has at least one
aperture. The reinforcing member is a tendon made of any polymer having a
nominal breaking strength of from about 100 to about 2,500 lb. which
extends through the aperture of each of the cell walls. The tendon is
preferably formed from a polymer which is enclosed in a polymer material
which is acid and alkali resistant. The tendon is terminated on an end of
the web by a loop of the tendon, or a washer and a knot of the tendon.
In another embodiment, the apertures of the cell walls are substantially
coincident and are preferably positioned adjacent the bonding areas.
Additionally, a length of the tendon is restrained from passing through
the aperture of one of the cell walls into an adjacent cell of the web. A
washer and a knot of the tendon provide the restraint.
Another aspect of the present invention is a method of installing a cell
web having a plurality of cells by forming a set of substantially
coincident apertures in cell walls of the cell web, guiding a tendon
through the apertures, terminating the tendon at ends of the cell web,
positioning the cell web on an earthen surface, anchoring the tendon to
prevent movement of the cell web and filling the cells with concrete or
earth material.
While the invention is susceptible to various modifications and alternative
forms, specific embodiments thereof have been shown by way of example in
the drawings and will herein be described in detail. It should be
understood, however, that it is not intended to limit the invention to the
particular forms disclosed, but on the contrary, the intention is to cover
all modifications, equivalents, and alternatives falling within the spirit
and scope of the invention as defined by the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partial perspective view of a single layer of the expanded
reinforced cell material of the present invention;
FIG. 2 is an enlarged perspective view of an expanded cell reinforced with
a tendon;
FIG. 3 is a partial cross-sectional view of the expanded cell material
taken along line 3--3 of FIG. 1 and terminated by a washer and a double
knot of the tendon;
FIG. 4 is a partial cross-sectional view of the collapsed cell material
taken along line 3--3 of FIG. 1 and terminated by a washer and a double
knot of the tendon;
FIG. 5 is a sectional view of a cell reinforced with a polymer tendon and
terminated by a loop of the tendon;
FIG. 6 is a sectional view of a cell reinforced with a polymer tendon and
terminated by a washer and a double knot of the tendon;
FIG. 7 is a cross-sectional view of an infilled reinforced cell material
internally anchored by the reinforcing tendon;
FIG. 8 is a cross-sectional view of an infilled reinforced cell material
externally anchored by the reinforcing tendon; and
FIG. 9 is a cross-sectional view of a concrete infilled reinforced cell
material being lifted for installation.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Turning now to the drawings and referring specifically to FIG. 1, there is
shown a cell material 10 reinforced by tendons 12. The cell material 10
has a plurality of strips of plastic 14 which are bonded together, one
strip to the next at alternating and equally spaced bonding areas 16 to
form cell walls 18 of individual cells 20. The bonding between strips may
best be described by thinking of the strips 14 as being paired, starting
with an outside strip 22 paired to an outermost inside strip 24, a pair of
the next two inside strips 24, etc. Each such pair is bonded at a bonding
area constituting an outside weld 26 adjacent the end 28 of each strip 14.
A short tail 30 between the end 28 of strip 14 and the outside weld 26 is
provided to stabilize segments of the strip 14 adjacent the outside weld
26. Each pair of strips is welded together at additional bonding areas 16,
creating equal length strip segments between the outside welds 26. In
addition to these welds, one strip 14 from each adjacent pair of strips 24
is also-welded together at positions intermediate each of the welds in the
pairs of strips, referred to hereafter as non-pair bonding areas 32. As a
result, when the plurality of strips 14 are stretched in a direction
perpendicular to the faces of the strips, the plastic strips bend in a
sinusoidal manner and form a web of cells 20 in a repeating cell pattern.
Each cell 20 of the cell web has a cell wall made from one strip and a
cell wall made from a different strip.
Adjacent the bonding areas 16 or 32 are apertures 34 in the strips 14. Each
tendon 12 extends through a set of apertures 34 which are substantially
coincident. As used herein, the phrase "substantially coincident" means
that the degree of overlap between adjacent apertures of the cell walls is
greater than fifty percent, preferably greater than about 75 percent and,
most preferably greater than about 90 percent. The tendons reinforce the
cell web and improve the stability of web installations by acting as
continuous, integral anchoring members which prevent unwanted displacement
of the web.
As shown in FIG. 2, the tendon 12 is preferably rectangular or oval in
cross section to provide a thin profile. A flexible tendon of rectangular
or oval cross section is easily knotted to terminate the tendon at an end
of the web or to connect adjoining sections of webs. Tendons having a flat
profile also readily fold as the tendon is inserted through the apertures
34. In order to properly reinforce the cell web and anchor fill material
placed within the cells, the tendon has a tensile strength of from about
100 to about 2,500 lb/in.sup.2. Preferably, the tendon is formed from a
polymer capable of providing such tensile strength as well as optimum
load-deformation characteristics and long-term creep performance. Such
polymers include polyester, polypropylene, polyethylene and the like.
In a preferred embodiment, the tendon is composed of a core material 36
surrounded by a sheath 38 which protects the core from a wide range of
chemicals encountered in stabilization and environmental protection work.
The core material 36 of the tendon is preferably any polymer having a
nominal breaking strength of from about 100 to about 2,500 lb. A linear
composite polymer core material is most preferred because it provides
long-term durability comparable to that of the cell web. Linear composite
tendons are commercially available from Delta Strapping Industries, Inc.
of Charlotte, N.C. The sheath 38 may be composed of an acid and alkali
resistant polymer or other acid and alkali resistant material to protect
the tendon from deterioration when exposed to acidic or basic materials or
environments, such as soil or limestone. A preferred tendon is made from
continuous high-tenacity polyester filament bundles coated with a
UV-stabilized high density polyethylene or polypropylene protective
sheath. Such tendons have been manufactured commercially by the Conwed
Company of Minneapolis, Minn.
FIG. 3 illustrates a cross-section of an expanded web taken along the line
3--3 of FIG. 1 wherein the tendon 12 extends through the substantially
coincident apertures 34 of each strip 14. FIG. 4 depicts the same cross
section in collapsed form. As the web is collapsed, the length of tendon
12 within each cell 20 folds upwardly along its center such that the
length of tendon assumes an inverted V-shaped form within the cell. The
compactness of the collapsed cell webs is maintained due to the thin
profile of the folded tendon. The tendons can be pre-installed during
manufacture of the cell webs. Furthermore, the collapsed, reinforced cell
webs are easily packaged, handled and shipped.
A tendon is terminated at the ends of the cell web to maintain the tendon
within the web. As illustrated in FIGS. 5 and 7, a preferred method of
terminating a tendon 12 is by forming a loop 40 in the tendon after the
tendon is guided through the aperture. In another preferred method, the
tendon is terminated by a steel or polymer washer 44 which is threaded
onto the tendon before a double knot 46 is formed such that the washer is
positioned between the knot 46 and the aperture 34 as shown in FIGS. 6 and
8.
The number of tendons present within a web is dependent upon the
application and the tensile strength of the tendon. For example, shoreline
installations may require only one tendon attached to a cell on an end of
the web to externally secure the web with an anchoring member. When
tendons are used to join sections of the webs, the tails of the cells at
the end of one web are positioned between the tails of the cells at the
end of another web. A tendon is guided through a set of apertures in the
tails of both interlocking webs to connect the sections of webs.
Concrete-filled webs typically contain two tendons per cell to enable the
webs to be moved, lifted and installed. Webs infilled with earth material
often contain one tendon per cell. For most applications, cells of the web
will include up to two tendons per cell. However, if tendons having lesser
tensile strength are used, such as polypropylene strapping, additional
tendons would be required to reinforce each cell.
In addition to reinforcing the cell webs, the tendons facilitate resistance
to applied forces such as hydraulic uplift and ice action which tend to
lift the cell webs. A web may be anchored to the ground at spaced
intervals along the tendons to prevent lifting of the web. FIG. 7
illustrates a cross-section of an anchored expanded web taken along the
line 3--3 of FIG. 1 wherein the tendon 12 extends through the
substantially coincident apertures 34 of each strip. J-pins 42, or other
earth anchors such as duckbill or auger anchors, are placed over the
tendon 12 within cells 20 and are driven into the ground. The J-pins 42
internally anchor the tendon 12 to minimize lifting of the cell web away
from the ground. Any number of the cells containing a tendon can be
anchored. Preferably, the anchors are spaced at intervals between the ends
of the web to resist applied forces along the entire length of the web.
Anchoring is not required in some applications where applied forces are
resisted by the passive resistance of the cell fill material acting on the
top surface of the tendon spanning between the cells. Additionally,
vegetative root mass which forms within the cells may envelope the tendons
and impart a natural root anchorage to the system. The web illustrated in
FIG. 7 is also externally anchored by a J-pin 42 or other earth anchor
which is placed within the loop 40 which terminates the tendon. The loop
may also be connected to a tendon of an adjoining web if desired.
Anchoring the tendons to earth anchors at the upper end of each web resists
forces which cause translational movement of the cell webs, such as
tractive forces experienced in channel lining applications, or sliding of
surface protection on steep slopes. FIG. 8 illustrates a cell web which is
anchored by a passive restraint anchor at the crest of the slope on which
the web rests. The tendon 12 is terminated with a loop 40 which is
attached to the deadman anchor 48 to minimize translational movement of
the web. The web is positioned above a geotextile or geomembrane liner 50,
particularly when the fill material is dissimilar to the subgrade. When a
reinforced cell web is installed on a sloped surface, restraints may be
formed along a length of the tendon to support the cells after they are
infilled. A preferred restraint is formed by guiding the tendon through an
aperture, threading a washer 44 onto the tendon, and forming a double knot
46 in the tendon such that the washer is positioned between the knot and
the aperture as illustrated in FIG. 8.
When the cell webs are used in multiple layers as earth retaining
structures, the ends of the tendons of each cell web layer can be anchored
to the backfill soil to resist translational sliding and overturning due
to active earth pressures. The preferred method of constructing such earth
retaining structures is to anchor guide posts into the ground at the
corner positions where the structure is to be built. The base layer web is
then stretched out and the corner cells are slid down over the posts. A
suitable fill material is filled into the cells of the base layer web and
compacted if desired. Subsequent web layers are then stretched out and
slid down over the posts, infilled and compacted until the structure is of
the desired height.
When concrete infill is required, concrete can be pre-cast in the
reinforced cell webs of the present invention before installation of the
web because the tendons anchor the concrete within the cells. The concrete
encases the tendons within the cells such that the concrete is cast around
the tendons. The tendons anchor the concrete within the cells so the
concrete is not displaced when the cell web is lifted. Furthermore, the
tendons remain flexible such that pre-cast sections of concrete-filled
cell webs can be moved, lifted and installed as shown in FIG. 9.
Concrete-filled cell webs exhibit maximum flexibility when the tendons are
positioned about the midpoint of the face of a strip (i.e., at about half
the width of the cell wall). In a preferred embodiment, each of the cell
walls has two apertures such that the apertures of each of the cell walls
of a cell are substantially coincident. Tendons extend through each set of
substantially coincident apertures and are terminated at the ends of the
web. The pre-cast sections are lifted by the terminated ends of the
tendons extending from the web and are moved for installation.
Concrete-filled cell webs are easily installed below water providing
excellent protection for shorelines, revetments, spillways, chutes and the
like. The webs conform to subgrade movement during underwater operation to
prevent piping and undermining. Conventional boat ramps and other
underwater structures can be replaced by the pre-cast sections. The
pre-cast sections can also be used on land as road base structures.
The cell webs can be installed by manually expanding the web in a direction
perpendicular to the faces of the strips of the web and infilling the
cells with concrete or earth material. When the reinforced cell webs are
infilled with earth material, the webs can also be installed through the
use of an installation frame as described in U.S. Pat. No. 4,717,283,
issued Jan. 5, 1988 to Gary Bach and incorporated herein by reference. The
cell web is secured to the installation frame to maintain the web in
expanded form. The frame is rotated such that the web rests on the
installation surface. Before the frame is removed, the tendons may be
internally or externally anchored to the surface as shown in FIGS. 7 and
8. The cells are then infilled with earth material to maintain the cell
web in its expanded configuration. The earth materials such as sand,
rounded rock, granular soils and aggregates, topsoil, vegetative materials
and the like, exert force on the top surface of the tendon spanning
between the cells to anchor the web.
The cell material is preferably made from sheet extruded polyethylene of 50
mil thickness. Carbon black may be included in the plastic to help prevent
ultraviolet degradation of the web material when exposed to sunlight. The
faces of the plastic strips of cell material may also have textured
surfaces as disclosed in U.S. Pat. No. 4,965,097, issued Oct. 23, 1990 to
Gary Bach and incorporated herein by reference. The cell webs may also
include notches which allow adjoining layers of cell webs to overlap along
their edges to improve the stackability of the webs in forming earth
retaining structures as described in U.S. Pat. No. 4,778,309, issued Oct.
18, 1988 to Bach et al.
The plastic strips may be bonded together by a number of methods known in
the art. The preferred method of ultrasonic welding is accomplished using
the process and apparatus disclosed in U.S. Pat. No. 4,647,325, issued
Mar. 3, 1987 to Gary Bach and incorporated herein by reference. The bond
is formed as groups of welding tips simultaneously contact the strips 14
to form a weld substantially traversing the entire width of the strips 14.
The apertures 34 may be formed in the strips 14 by a number of methods
known in the art either before or after the strips are bonded together.
Preferably, the apertures are formed by drilling through a collapsed cell
web to form a set of substantially coincident apertures through the web. A
suitable length of tendon is then guided through each aperture, and may be
restrained within the cell web as discussed above in reference to FIG. 8.
The tendon is terminated at the ends of the web with either a loop of
tendon or a washer and a double knot as shown in FIGS. 5-8. As the cell
web is then fully expanded, the tendon is positioned within the cells and
is folded vertically between adjacent cell walls as the cell web is
re-collapsed. The reinforced cell material is then palletized and shipped
for installation. Alternatively, the tendons may be guided through the
apertures at the installation site.
The apertures are preferably positioned at about the midpoint of the width
of the plastic strips when infilled with concrete resulting in minimal
tension on the tendons. When infilled with earth materials, the apertures
are preferably positioned below the midpoint of the width of the plastic
strip so that more weight is placed on the tendon to anchor the web. The
apertures may be positioned anywhere along the length of the cell walls,
but it is preferred that the apertures are not formed in the bonding
areas.
The web materials may be manufactured to result in webs of any dimension,
but are typically three to eight feet wide and eight to twenty feet in
length when stretched out for use. In the preferred embodiment, each
plastic strip 14 is eight inches wide. The bonding areas 16 are about
thirteen inches apart on each strip, as are the non-pair bonding areas 32.
Each cell wall 18 comprises a section of the plastic strip about thirteen
inches in length, between adjacent bonding areas 16 or non-pair bonding
areas 32. The tail 30 is about one inch in length. The tendon 12 is about
one-quarter to three-quarter inch wide and the apertures 34 have a
diameter slightly greater than the width of the tendon.
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