U.S. patent number 3,811,287 [Application Number 05/170,607] was granted by the patent office on 1974-05-21 for bottom and bank facing.
Invention is credited to Jan Gerrit De Winter.
United States Patent |
3,811,287 |
De Winter |
May 21, 1974 |
BOTTOM AND BANK FACING
Abstract
A bottom and bank facing for preventing erosion of subaqueous
soil structures comprising a lattice of fascines fastened to a mat
of synthetic resin material, wherein the resin material comprises a
fabric sheet having means attached thereto for use in securing the
fascines to the fabric, such means including transversely spaced
groups of threads, each group being woven into the fabric at spaced
portions along their length to provide resultant loops or floating
portions in each group of threads to which the fascines are
attached; or separate strips of fabric fastened to the fabric sheet
for being tied to the fascines.
Inventors: |
De Winter; Jan Gerrit
(Enschede, NL) |
Family
ID: |
26644184 |
Appl.
No.: |
05/170,607 |
Filed: |
August 10, 1971 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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721784 |
Apr 16, 1968 |
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Foreign Application Priority Data
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Apr 17, 1967 [NL] |
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6705380 |
Nov 2, 1967 [NL] |
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6714909 |
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Current U.S.
Class: |
405/19;
428/102 |
Current CPC
Class: |
E02B
3/126 (20130101); E02B 3/125 (20130101); E02B
3/122 (20130101); Y02A 10/11 (20180101); Y10T
428/24033 (20150115); Y02A 10/16 (20180101) |
Current International
Class: |
E02B
3/12 (20060101); E02b 003/12 () |
Field of
Search: |
;161/48,49,50,53,91,164,270,78,53,57,58,89,92 ;156/60,250,252,253
;61/38 ;2/237,266,221 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Lesmes; George F.
Assistant Examiner: Silverman; Stanley S.
Attorney, Agent or Firm: Burns; Robert E.
Parent Case Text
This is a continuation-in-part of Ser. No. 721,784, filed Apr. 16,
1968, now abandoned.
Claims
What I claim is:
1. A bottom and bank facing for preventing erosion of subaqueous
soil structures on which it is placed comprising a strong, slightly
elastic, sandtight, water permeable continuous mat of synthetic
resin fabric lying on the soil surface to be protected, a lattice
of fascines superposed on said mat and comprising a set of spaced
parallel lower fascines disposed on said mat and a set of spaced
parallel upper fascines overlying said lower fascines and crossing
said lower fascines substantially at right angles, said mat having
on its upper surface at each crossing of said upper and lower
lattices and intermediate said crossings receiving means connected
with said mat and providing openings to receive tying material, and
strands of tying material passing over said fascines and through
respective openings of said receiving means at each said crossing
and intermediate said crossings to secure the crossing fascines to
one another and to secure said fascines in said mat, said strands
of tying material passing through said openings of said receiving
means without passing to the lower side of said mat and thereby
avoiding discontinuities in the fabric of said mat, said fascines
being disposed solely on the upper face of said mat whereby said
mat lies on the surface of the soil to be protected without
fascines therebetween, thereby avoiding undermining of the
facing.
2. A facing according to claim 1, wherein the synthetic resin
material fabric is a fabric of polyethylene yarn, said fabric
having a tensile strength of at least 2,000 kg/m.
3. A facing as set forth in claim 1, in which said receiving means
comprises a plurality of elongated spaced groups of threads
disposed in parallel and woven into said synthetic resin fabric
only at transversely aligned intermittent portions along the extent
of said threads, thereby providing floating portions of said
threads between said intermittent portions, one of said sets of
fascines being disposed in alignment with said groups of parallel
threads, and in which said strands of tying material for securing
said fascines to said mat pass under said floating portion of said
groups of threads and over said fascines.
4. A facing according to claim 3, in which said groups of threads
are of a first color, and said fabric is otherwise of a second
color which contrasts with said first color.
5. A facing as set forth in claim 1, in which said receiving means
comprises a plurality of separate strip means of synthetic resin
fabric attached to said mat for enclosing at least a portion of the
circumference of said lower fascines along a substantial
longitudinal extent thereof, and for enclosing spaced portions of
said upper fascines, and means for securing said strip means to
said mat, said strip means having eyelets therein to receive said
strands of tying material passing through said eyelets and over
said fascines.
6. A facing according to claim 5, wherein the strip means are sewn
to the mat.
7. A facing as set forth in claim 1, in which the spacing between
said parallel fascines is of the order of three quarters to 1
meter.
8. A facing as set forth in claim 1, in which said mat extends
beyond at least one of the two outermost fascines in one of said
sets of fascines and is folded back to form a flap, and further
comprising means attaching the edge of said flap to said mat to
provide pocket means for holding a ballast weight.
9. A facing as set forth in claim 1, in which said lower fascines
are disposed longitudinally in a common plane below said upper
fascines, and in which said mat is disposed in continuous contact
with said lower fascines along the entire longitudinal coincident
extent of said mat and said lower fascines.
10. A facing as set forth in claim 9, in which the synthetic resin
fabric is a fabric comprising polyethylene yarn, said fabric having
a tensile strength of at least 2,000 kg/m', and further comprising
a plurality of elongated spaced groups of threads disposed in
parallel and woven into said fabric only at transversely aligned
intermittent portions along the extent of said threads, the
fascines of one of said sets of fascines being disposed in
alignment with said respective groups of threads, and in which said
strands of tying material for securing said fascines to said mat
pass under said floating portion of said group of threads and over
said fascines.
11. A facing as set forth in claim 10, in which said polyethylene
yarn is disposed in the warp in said fabric, said fabric further
comprising weft yarn selected from the group consisting of
polyamide polyester or polypropylene.
Description
This invention relates to facings for subaqueous soil structures,
comprising fascines which cross each other according to a lattice
pattern and are interconnected at the crossing points, and
continuous fabric mat connected with said fascines.
Conventional facings of this kind, known in the field of hydraulic
engineering as "mattresses", comprise a bottom lattice formed from
fascines, an upper lattice of fascines in register with said bottom
lattice, and a center portion or filling consisting of a plurality
of cross-wise disposed layers of brush sandwiched between the two
lattices. At the crossing points the fascines are interconnected
with lashing, rope or like material, and in addition firm
connections are made with this material between the crossing points
of the bottom lattice and the superjacent crossing points of the
upper lattice, so that the interposed filling is firmly retained
therebetween.
A disadvantage of these known mattresses is that they require much
material such as brush and reeds, and a considerable ballast is
required to compensate for the buoyancy of that material when the
facing is submerged. In addition, as a result of their considerable
height, the known mattresses are difficult to maneuver, and since
the bottom lattice of fascines has a considerable thickness, the
filling is prevented from contacting the bottom or bank at the
portions along the fascines of the bottom lattice, thereby
providing paths for water flow and resultant erosion. Also, the
mattresses used hitherto are often insufficiently sand-tight.
It is an object of the present invention to provide a bottom and
bank facing or revetment which obviates the above and similar
disadvantages of known mattresses.
According to the present invention, there is provided facing for
subaqueous soil structures, comprising fascines which cross each
other according to a lattice pattern and are interconnected at the
crossing points, and a continuous mat connected with said fascines,
said mat consisting of a strong, slightly elastic, synthetic resin
material, such as a fabric, whose sand-tightness, thickness,
strength, and water-permeability are adapted to the requirements
dictated by the soil conditions and the other conditions of the
work. The mat is secured to the fascines as by means of separate
strips of the same material such as the mat, said separate strips
being fastened to the mat and tied around the fascines; or, by
means of bands of threads which are woven into the mat at spaced
portions along their lengths, thus providing unattached or floating
portions of the threads in each band thereof to which the fascines
may be secured.
It should be noted that the use of a mat as the filling of a
mattress has already been proposed to replace the conventional
brush and/or reed filling. In the prior proposal, however, the mat
concerned is composed of an impermeable synthetic resin foil
reinforced with a wire netting. In that known application the
securing of the fascines to the mat filling is time-consuming and
cumbersome.
It should further be noted that the use of synthetic resin netting
is known per se for the protection of mounds of sand or earth, but
not as a substitute for mattresses and other submerged bottom or
bank facings.
According to a preferred embodiment of the invention the synthetic
resin material engages portions of the fascines. That is, zones of
the synthetic resin material constituting the mat proper extend in
at least one of the directions of longitudinal extent of the
fascines, and a group of threads are woven into each of said zones
in bands of a certain width on opposite sides of the axis of the
fascine concerned, said threads being unattached to the mat at
portions therealong to float jointly on the side of the mat facing
the fascines in places spaced along the length of the band, said
fascines being connected together and with the mat by means of rope
or like material, which is passed through the loops formed by the
bundled floats on opposite sides of the fascines and across the
fascines and thus tightened.
According to the invention the floating bands of woven-in threads
preferably have a color contrasting with the color of the mat, so
that the lattice pattern according to which the fascines must be
laid in assembling the facing is clearly marked, while the loops
formed by the floating thread portions, through which rope or other
material is passed for firmly connecting the fascines together and
to the mat, become clearly visible. The rapid assembly of the
mattress is thus effectively promoted.
When the lower fascines are laid transversely to the woven-in bands
of synthetic threads it may be sufficient, by a suitable selection
of their spacing, to connect them with the mat at the points where
they are intersected by the upper fascines, while the upper
fascines can be connected to the mat through bundled floats at
points intermediate said crossing points. However, the lower
fascines may also be laid parallel to the woven-in bands of
threads. In that case separate bands of threads may be woven in for
the connection of the upper fascines with the mat between the
crossing points with the lower fascines. These bands, conveniently
extending parallel to the other bands, have floating portions at
the places where they are intersected by the upper fascines.
A typical example of a suitable material for the purposes of the
present invention is a dobby fabric of polyethylene yarn having a
tensile strength of 3,000kg/m', and having additional threads,
disposed in parallel, and partially woven therein in spaced groups,
each group including about 32 threads arranged to provide a band of
such threads which is about 2.2 cm. in width; said bands in each
pair having their axes spaced at about 15 cm., and each pair of
such bands being spaced from the adjacent pairs by a distance
corresponding to the distance between adjacent parallel fascines.
Each of the threads is woven into the fabric at intervals spaced
along its length so that it provides a loop or floating portion,
such loops being disposed in parallel and each extending for about
10 cm for providing groups of thread loops to which the fascines
may be attached.
In this arrangement, the loops constituted by the groups of
floating portions of the threads are capable of holding tensile
forces of at least 100kg, which is amply sufficient for the
contemplated connections and fastenings.
According to another embodiment of the invention, separate strips
of the synthetic resin material referred to, such as a fabric, are
attached to the mat for engaging a portion the circumference of the
lower fascines in the lattice of at least substantially throughout
the longitudinal extent thereof, and for engaging the upper
fascines through portions of their length between the crossing
points, the longitudinal edges of said strips having eyelets for
receiving rope therethrough to tighten the strips around the
fascines. Preferably, the separate strips are connected to the mat
by two-needle stitchings, which are easy to make and result in
strong connections; and, the resin material is a polyethylene yarn
fabric having a tensil strength of at least 2,000 kg/m'.
By tightening the rope material through the eyelets, in the manner
described, the rope material comprising, for example, manilla rope
or nylon cord, there is obtained a sturdy construction which
requires relatively little ballast for it to be sunk. When the
facing according to the invention is sunk, the mat fully beds down
on the bottom or bank throughout its extent, so that there is no
risk of the mattress being undermined. A special advantage is that
the manufacture of the facing does not require a separate
intertidal building site or slipway, since it can be made and payed
out from a vessel or from the bank. The lattice to be formed from
the fascines is secured, in the manner described, to the gradually
unrolled mat.
Of essential importance is also the fact that the mat does not
require any brush; such material which is in short supply in some
areas being required only for use in forming fascines, if required
at all. The rate of production of the facings according to the
invention is at least three to four times that of conventional
mattresses, and a stock of the fascines can be made, and a facing
can be rapidly assembled, as and when required, mainly by unskilled
labor. Skilled labor is only required for sinking the facing. In
addition, the material used for the mat has a long service life as
compared with conventional mattresses, since the fabric material is
resistant to corrosion.
A further advantage is that time is also saved in the sinking of
the facing. In a similar period of time, considerably more facings
can be positioned than has hitherto been possible, which is
especially of importance with tidal currents. Also, no auxiliary
structures are required at high water, as is the case with
conventional mattresses. In cases in which a bedding must be made
for the facing by excavation, an obvious advantage as compared with
the known mattresses is the small thickness of the facing according
to the invention, which materially reduces the excavation work
required.
A preferred feature of the embodiment of the invention provided
with separate fastening strips is that washers of rubber or like
material may be inserted around the eyelets so that the insertion
of the connecting rope material is thus considerably simplified,
while there is no risk of tearing when the connections are
tightened.
Another feature of the invention, which is a convenience in laying
down the structure, is that the mat extends beyond at least one of
the two extreme lower fascines to form a projecting flap, the free
terminal zone of which is weighted as with a length of reinforcing
rod, such as used in reinforcing concrete, or the like, enclosed in
an end seam thereof. By virtue of the flap it is possible to lay a
plurality of such facings in an overlapping relationship and hence
closer together, thereby providing a sturdier revetment. The flap
can also be useful during the transport of the mattress,
particularly by virtue of the weighting member accommodated
therein, as will be described more fully hereinafter.
The invention will now be described in greater detail with
reference to the accompanying drawings, which illustrate by way of
example, two embodiments of a facing according to the
invention.
In said drawings,
FIG. 1 is a plan view of a portion of a first embodiment of the
invention;
FIG. 2 shows, on a larger scale, a part-sectional view on the line
II--II in FIG. 1;
FIG. 3 is a plan view of a portion of a second embodiment of the
invention, with portions broken away; and,
FIG. 4 is a cross-sectional view on the line II--II in FIG. 3.
Referring to the drawings, there is shown a mat 1 of polyethylene
yarn dobby fabric having a tensile strength of 3,000 kg/m' (that is
to say, a length of the fabric having a width of 1 m can carry
tensile loads of up to 3,000 kg uniformly applied throughout its
width). The mat is composed of a plurality of webs of the maximum
width that can be woven, the webs being sewn together to a size
which is common for facings, for example, 30 .times. 60m. The mat
contains a plurality of longitudinally disposed groups of threads
2, each group forming a longitudinal band of about 2.2 cm, and each
formed of 32 polyethylene threads woven into the fabric of the mat
(such as with a sewing machine) except at a plurality of places
spaced along the length of the mat, where all of the threads in the
group float freely on the upper side of the mat as viewed in FIG. 1
for an extent of about 10 cm. These floating bundles of threads
thus form loops 3, through which ropes can be inserted for securing
fascines to the mat.
As shown in FIG. 1 the bands are woven in pairs at intervals spaced
apart 50 cm transversely of the mat, the axes of the bands of the
individual pairs being spaced a distance of 15 cm. The loops formed
by the floating thread portions are located at the points of
intersection of the bands with an imaginary system of lines
extending transversely of the mat. Thus, the lines in this system
are disposed in a pattern of 15-50-15-50 cm etc., transversely of
the mat.
As shown in the drawing, lower fascines 4 are laid in alignment
with the middle of every other pair of bands on the mat 1, and
upper fascines 5 are laid transversely to these, spaced 1 m from
each other. The axes of the crossing fascines thus form a lattice
pattern of squares. At each crossing point the fascines are secured
together and to the mat by ties 6, passing through the loops 3 and
across the superposed fascines. At intermediate points the lower
fascines are similarly tied to the mat by means of ties 7 passed
through the loops 3 located opposite each other at these points,
and the upper fascines are secured by ties 8 passing through the
loops 3 of the pairs of bands on which no lower fascines have been
laid.
With a pattern of bands similar to the embodiment illustrated, it
is naturally also possible to interchange the lower and upper
fascines, and, with a greater distance of, for example, 75 cm,
between the center lines of the successive pairs, to lay an upper
fascine between each pair of bands, which is then connected with
the mat between the points where the upper fascines are intersected
by the lower fascines, the latter being solely connected with the
mat, as described above, at said points of intersection with the
upper fascines.
FIG. 2 shows in detail how the material of the mat is pulled tight
against the fascines by tightening the ties 6, 7 and 8.
In an alternative configuration, the spacing between the bands in
each pair is omitted and the bands are moved together to provide a
single band every 50 cm. transversely of the mat, each band
comprising a group of 64 threads providing a 4.4 cm. band.
It has been found that a particularly preferable fabric for use in
silty conditions comprises a dobby fabric consisting, in warp, of
0.3 mm diameter polyethylene monofilament yarn, varying from about
13 to 15 ends per cm; and, in weft, of an 840 to 1,000 denier
multifilament yarn such as polyamide polyester or polypropylene,
varying from 10 to 14 ends per cm. Such a fabric is exceedingly
strong and has, for example, a tensile strength in warp of 4,000 kg
per meter, and a corresponding strength in weft of about 5,500 kg
per meter. Strong means for fastening the fascines to the mat are
provided by weaving threads into the fabric to provide bands about
4.4 cm. wide at a spacing of about 50 cm., each such band including
64 threads of polyethylene monofilaments of a color which contrasts
with that of the fabric. As described above, the threads are woven
in to provide floating portions extending for about 10 cm. and at
equally spaced intervals along the bands. The loops which result
from bundling the floating portions together when tying the
fascines to the mat will sustain a tensile force in excess of 180
kg, thus providing adequate strength for the fascine
fastenings.
For applications where a coarser soil structure is to be protected
the mat preferably comprises a dobby fabric of 0.3 mm. diameter
polyethylene monofilament yarn varying from 20 to 23 ends per cm.
in warp, and 7 to 11 ends per cm in weft, thus providing a tensile
strength in warp of 5,500 kg per meter, and 3,000 kg per meter in
weft. The bands of threads may be provided as set forth in the
above example. In any event, the bands of threads, in any of the
above-described configurations, also provide a reinforcing function
to further strengthen the fabric.
Referring to FIGS. 3 and 4, there is shown a mat 11 of a
composition similar to that of the above-described mat shown in
FIGS. 1 and 2. Sewn to the mat are a plurality of separate strips
12 of a material similar to that of the mat fabric, said strips
having a width of 25 cm and being folded upon themselves along
their longitudinal edges to form an overlap or doubling of about 4
cm. The strips 12 are spaced apart about 1 m and are stitched to
the webs of fabric comprising the mat by means of two-needle
stitchings extending transversely of the mat, across the full width
thereof. On one end of the mat a strip 12 is provided adjacent to
the edge, and on the other end the last strip is spaced about 1 m
from the edge to leave a flap 14 about 1 m wide, the flap having a
seam formed at its terminal edge to receive a length of iron 15
such as a reinforcing rod for concrete or other suitable weighting
member. Eyelets 16 are provided in the double longitudinal margins
of the strips 12 at the points indicated in FIG. 3, and rubber
washers are inserted between the fabric and the eyelets. Previously
prepared fascines 17 are laid on the strips 12 and comprise the
lower fascines of the lattice to be formed. Across these lower
fascines 17 are laid upper fascines 18, i.e., longitudinally of the
mat, also spaced about 1 m from each other. The upper fascines 18
cross the lower fascines at places where four eyelets are fastened
in the margins of the strips 12. Strips 19, about 40 cm long and
otherwise similar in material and design to the strips 12, are sewn
to the mat, also by two-needle stitchings 20, between the points of
intersection of each upper fascine with two successive lower
fascines 17, with eyelets 21, similar to the eyelets 16, and rubber
washers are provided centrally opposite each other in the margins
of the strips. At the points of intersection of the fascines, and
the points intermediate these points of intersection, the strips 12
and 19 are firmly lashed together by means of strong nylon cord
inserted through the eyelets 16 and 21, so that the strips 12 and
19 embrace part of the circumference of the lower fascines 17 and
the upper fascines 18, respectively. The extreme eyelets 16 are
disposed adjacent to the longitudinal edges of the mat 11.
FIG. 4 shows that the mat 11 is pulled against the upper fascines
at least in the intermediate zone between each pair of adjacent
lower fascines.
In FIG. 4, the direction of current flow is indicated by an arrow
A. By virtue of the weighting member 15, the flap 14 of the mat 11
will hang down and thus enable utilization of the current in
transporting the floating facing to its destination. It will be
seen that the flap 14 will assume a bulging shape.
The firm connections between the mat and the fascines, which are
further strengthened by the partially surrounding strips and the
lash connections, are productive of a sturdy facing which
nevertheless is light in weight and low in buoyancy, so that
relatively little ballast is required for sinking the mattress.
Accordingly, a large proportion of the overall ballast acts as
actual weighting ballast on the facing when it is deposited on the
bottom or bank.
Other modifications and changes will be readily apparent to those
skilled in the art, and can be made without departing from the
scope of the invention as defined by the following claims.
* * * * *