Note: Descriptions are shown in the official language in which they were submitted.
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:TITLE OF 'THE INVENTION
METHOD FQR CONSTFCrJCTINGr A PLASTIC LINED CONCRETE STRUCTURE
AND sTRUCT~E I~uILT THIrREBY
BACKGROUND OF THE INVENTION
Field of the Znvtnrion
The present invention relates generally to the field of concrete
structures of the sort which may often be us~l in the construction of open
topped or
domed, ground level yr elevated tanks and the like that may generally be used
to hold
liquids, for example, water. In particular the present invention relates to
plastjc lined
concrete structures and the metliodology used in the fabrication of composite
plastic
lined concrete structures where the plastic lining is securely affixed to a
concrete wall.
The invention has special utility in connection with plastic lined
prestressed/post-
tensioned concrete tanks-
The Prior Art Background
Concrete tanks have been widely used for decades to hold fresh or
waste water, and the like. Generally speakinø such tanks are highly
commercially
valuable properties, and a large construction industry has been established to
serve the
needs of a variety of activities and entp rises which desire an economical and
reliable means for holding a xeadily available supply of fresh water or for
storing
waste water during and/or prior to treatment. Such tanks are currently
available in
sizes ranging from about 50,000 gallons to several million ballons or more.
Prior art concrete tanks, while extremely successful in many regards,
have had limited applicability in situations where the liquid to be contained
is capable
of reacting with or otherwise harming concrete.
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To increase the overall applicability of cortcxete tanks, plastic linings
have been proposed to limit the exposure of the interior walls of tanks to the
material
captained therein, Howtvcr, it has been a very difhcuIt and expensive
operation to
attach large sheets of plastic to concrete walls in such a way that the
plastic sheets are
securely attached to the walls and all of the seams between adjacent sheets
have
complete integrity.
svMl~ARx of T~ ~NVENT~oN
The present invention provides a solution for many of the problems
encountered previously in the construction of plastic lined concrete tanks.
That is to
say, in accordance with the concepts and principles of the invention, a method
is
provided for efficiently and economically consuucting plastic lined concrete
structures wherein the structural integrity of the incorporated plastic
linings is greatly
enhanced. rn this latter regard, the methodology provided by the invention is
particularly applicable to all varieties of concrete tanks, including, for
example, and
without limitation, eonexete tanks that are standard cast-in place, wire wound
and
presn~essed, and internally tendoned and post-tensioned. Thus, in one fonn of
the
invention, the same provides a method that includes forming fast and second
plastic
Lined eoperete panels, each panel including a concrete slab having an
elongated edge
and a surface, and a plastic sheet having a plurality of anchoring projections
protruding ourivardly from a face thereof. The forming of the panels is
conducted in
such a way that the face of each plastic sheet is engaged against the surface
of a
corresponding concrete slab and the anehozing projections are embedded in the
concrete of the corresponding slab. In addition, the plastic sheets are each
arranged
and positioned such that an edge flap portion thereof projects outwardly
beyoztd the
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edge of the corresponding slab. The formed panels are arranged in ad3aeent,
aligned
positions with the elongated edge of the concrete slab of the first panel
disposed in
opposing spaced relationship relative to the elongated edge of the concrete
slab of the
second panel so that an elongated gap is presented between the edges. In
addition, an
outboard segment of the edge flap portion of the plastic sheet of the first
panel is
disposed in overlapping relationship relative to an outboard segment of the
edge flap
portion of the plastic sheet of the second panel at said gap. The overlapping
segments
are then welded together with an upwardly extending seaxn.
In another adaptation of the invention, a method is provided for
constructing a plastic lined concrete structure which comprises providing f
cst and
second plastic sheets, each sheet having a facw and a plurality of anchoring
projections
protruding outwardly fi;om the face. In this adaptation, the method further
includes
forming a first plastic lined concrete panel by causing a first quantity of
wet
cementitious material to come into contact with a portion of the face of the
first
plastic sheet, pen~nitting the first quantity of cementitious zztaterial to
set in the form of
a first solid concrete slab having the anchoi~ng projections of the first
plastic sheet
embedded therein_ The first concrete slab desirably has an elona tod edge and
the
first plastic sheet and the first quantity of Wet cernentitious material are
initially
arranged relative to one another such that an edge ~lap portion of the :brst
plastic sheet
projects outwardly beyond the edge ofthe brst slab after the cementitious
material has
become set. Also in this adaptatian of the invention, a second plastic lined
concrete
panel is formed in essentially the same rnarner as tk~e first plasric lined
panel. The
formed panels are an-anged in adjacent, aligned positions with the elongated
edge of
the first canerete slab disposed in opposing spaced relationship relative to
the
elongated edge of the second concrete slab to thereby present an elongated gap
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between the edges. In addition, an outboard segment of the edge ~lap portion
of the
plastic sheet of the first panel is arranged in overlapping relationship
relative to an
outboard segment of the edge flap portion of the plastic sheet of the second
panel at
said gap. The overlapping outboard segments are then welded together in situ
with an
upwardly extending sea~m_
In yet another aspect o~ rhr invention, a method is provided for
constructing a plastic lined concrete tank. In accordance with this aspect of
the
invention, the method includes forming a plurality of plastic lined concrete
panels.
Each of the panels includes a concrete slab having opposed, laterally spaced,
elongated edges and an inner surface, and a plastic sheet having a plurality
of
anchoring projections protruding outwardly from a face thereof. The forming of
the
panels is conducted in such a way that the face of each plastic sheet is
engaged against
the surface of a corresponding concrete slab with the anchoring projections
embedded
in the concrete of the corresponding slab. The plastic sheets are arranged,
configured
and positioned such that a respective edge flap portion thereof projects
outwardly
beyond each edge of the corresponding slab. Each of the edge flap portions has
an
outboard segment. The formed panels are arranged in adjacent, aligned
positions
around a periphery of a tank foundation with the inner surfaces of the slabs
facing
inwardly, with the elongated edges of the slabs extendixag upwardly, with the
respective elongated edges of each slab disposed in opposing spaced
relationship
relative to the elongated edges of adjacent slabs to thereby present elongated
gaps
therebetwecn, with the plastic sheets disposed within the periphery, and with
the
outboard segments of the edge flap portions of each sheet overlapping the
outboard
segments of the edge flap portions of the sheets of adjacent panels at said
gap. The
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overlapping outboard segments are welded together in situ with an upwardly
extending seam.
Desirably, although not necessarily, a wedge welder may be used for
welding the overlapping segments together. When a wedge welder is used, a
maixt
S body portion of the welder may ideally be located on an opposite side of the
plastic
sheets from the concrete slabs during the welding. Ideally, a second portion
of the
wedge welder may be positioned within the gap between the edges dutang said
welding.
In preferred forms of the invention, the edges of the panels may be
.r/
coextensive in length and the edge flap portions may project outwardly beyond
the
edges along essentially tire entire length thereof. In other preferred forms
of the
invention, the panels may initially be formed with the edges thereof disposed
to
extend in an essentially horizontal direction. That is to say, the panels may
be formed
on the ground and thereafter erected so that the edges extend in as
essentially upright
13 direction. When the panels are erect, the welding may ideally be
accomplished by
causing a welder mechanism to move upwardly along the overlapping segments of
the
edge flap portions of the plastic sheets. In further accordance with the
concepts and
principles of the invention, the dap between the edges of the panels may be
filled with
a grouting material after the welding has been completed. In this latter
regard, it is a
very desirable feature of the invention for the plastic sheets to be arranged
and
constructed such that anchoring pmj ectiorzs are provided on the edge flap
portions so
that the same project into the gap. Accordingly, during the grouting
operation, a firm
bond may be created between the anchoring projections and the grout to hold
the
plastic sheet firmly against the concrett at all locations including the gaps.
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In further accordance with the concepts and principles of the invention,
the same provides plastic lined structures and plastic lined tanks that have
been built
employing the methodology of the invention_
BR~D~'SCRII'~'IQN QF 'SHE DRA'W1NGS
Figure 1 is a fragmentary, p;utial, perspective, elevatianal view of a
tank which has been constructed from, a series of side-by-side aligned panels
in
accordance with the methodology provided by the present invention;
lnigure 2 is an enlargtd, fragmentary, partial cross-sectional view
taken essentially in a downward direction along the line 2-2 of Fig. 1 and
which also
schematically illustrates the positioning of a welder used in accordance with
the
concepts and principles of the inv~tion;
Figure 3 is a perspective view illustrating the methodology used in
constructing the panels used to construct the tank of Fig. I;
Figure 4 is a fragmentary, partial, perspective view of a panel used to
construct the tank of Fig. I, and wherein certain parts have been broken away
to
illustrate the internal construction of the panel;
Figure 5 is perspective view illustrating the manner in which the
eructed panels are supported during construction of a tank;
>iigure 6 is a side elevational view of a wedge welder oFthe sort used
2U to weld overlapping sheets ofplastic together; and
Figure 7 is an elevational cross-sectional view illustrating an
alternative procedure for constructing plastic-lined concrete tanks in
accordance with
the invention_
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DE AILED D)SCRIPTION OF TF~ PREFERRED E
~ODIMENTS
As mentioned above, the present invention relates generally to the field
of concrete structures of the sort which may often be used in the construction
of
ground level or elevated concrete liquid containing storage tanks and the
like, and to
plastic lined concrete structures and the methodology used in the fabrication
of
composite plastic lined concrete structures whereby the plastic lining is
securely
affixed to a concrete v~rall. Iu connection with the foregoing, and in further
accordance with the invention, the tanks may have no mof or a roof that
comprises a
dome made from concrete, aluminum, fabric, or a flat panel roof with or
without
column supports that bear at or beneath the floor of the tank.
In a particularly preferred mode of the invention, the same provides
rrtethodology for constructing plastic lined concrete taztks; however, as will
be
apparent to those of ordinazy skill in the concrete construction arc, the
invention more
broadly relates to the construction of any sort of plastic lined concrete
structures
where it is desirable to prefabricate a plurality of lined concrete panels,
cause the
panels to be arranged in an aligned, side-by-side relationship, and thereafter
weld the
separate linings on adjacent panels togethet~ in situ to thereby present a
continuous
sealed barrier.
Broadly, and with particular reference to Figs. 1 through 5 of the
drawings, the method for constructing plastic lined concrete structures
includes
forming a plurality of plastic lined cvn~:rete panels 10. Such panels may be
constructed adjacent the site where a tank is to be built or at a remote
location and
shipped to the site. Panels 10 are similarly constructed and each includes a
concrete
slab 12, which may be gea~erally rectangular in shape arid which desirably has
a pair
of opposed, laterally spaced, elongated lateral edges 14, 16 and a surface 18
which
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extends laterally between edges 1 A, 16. As can be seen from the drawings, in
a
preferred form of the invention, the slabs 12 tray desirably be curved so that
when a
series of the same are placed in an aligned, side-by-side relationship,
together they
may be arranged so as to present the outer periphery of a generally round
concrete
S tank 20 which may be used to contain liquids generally, including water and
the like.
Each of the panels 10 also includes a plastic sheet 22 having a plurality
of anchoring projections 24 protruding outwardly from a face 26 thereofi and
the
panels IO arc desirably formed in such a way that the face 26 of each plastic
sheet 22
is engaged against the surface 1$ of the corresponding concrete slab 12 with
the
anchoring projectioxts 24 embedded within the concrete of the slab 12. The
sheets 22
may be formed from any sort of thermoplastic material which is essentially
inert to
the substances that it will cono~e into contact with during operation and
tough enough
to withstand the physical rigors associated with the construction and/or use
of the
lined structure, Ideally, the shits 22 nrtay bc, formed from hialt density
polyethylene,
linear low density polyethylene, polypropylene and/or PVC. Desirably the
plastic
sheets 22 are wider than the concrete slabs 12, and each sheet 22 is atranled
and
positioned on its corresponding slab 12 in such a way that an edge p.ap
portion 28
thereof projects outwardly beyond the edge 14 of the corresponding slab 12 and
an
edge flap portion 30 projects outwardly beyond the opposite edge 16 of the
correspondiutg slab 12.
The sheets Z2 ,generally may have a thickness ranging firom about 0.5
mm (0.020 inch) to about 7 mm {0.28 inch), and desirably the thicimess may be
within the range of from about 1.5 to 4 mrn. hor heavy duty operation under
adverse
axidlor corrosive chemical conditions, it has been found that a high da~sity
polyethylene material having a thickness of about 3 nrtrt may be desirable.
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Conversely, far applications where the tank. will contain relatively pure
water and be
exposed to mild temperature conditions, it may be desirable, for economical
reasons,
to use a linear low density polyethylene having a thiclrness of Z n~.
As can be seen from )~igs. 1 and z, the panels 10 of a series 32 thereof
are disposed in adjacent, aligned positions with the elongated edge 14 of each
concrete slab 12 arranged in opposing spaced relationship relative to the
elongated
edge 16 of an adjacent concrete slab 12 so as to thereby present an elon~ted
gap 34
between the edge 14 of one slabl2 and the edge 16 of the adjacent slab 12.
Desirably,
the panels 10 are arranged so that an outboard segment 36 of the edge flap
portion 30
of *he plastic sheet of one panel IO is disposed in overlapping relationship
to an
outboard segment 38 of the edge flap portion 2$ of the plastic sheet 22 of the
adjacent
panel at the gap 34. In accordance with the concepts and principles of the
invention,
the overlapping segments 36, 38 are welded together in situ.
A preferred procodure for forming the panels 10 is illustrated in Figs. 3
and 4. Fig. 3 illustrates a form box 40 which can be used in the fabrication
of a panel
10. Form box 40 includes a lower former 41 having an upper fornx surface 42,
the
lateral cross-section of which can best be seen in Fig. 4. It is to be noted
in ibis regard
that surface 42 is convex and upwardly curved at the same degree of curvature
as the
inside circuamference of a tank to be constructed from the panels i0 formed in
box 40.
A sheet 22 is then laid out on the surface 42 so that face 26 faces upwardly
and
projections 24 protrude upwardly. It is to be noted in this latter regard that
the
projections 24 as illustrated are preferably in the form of a multiplicity of
elongated,
generally parallel T-shaped ribs 44 which are integral with the sheet 22.
However, as
will be apparent to those skilled in the field of plastic linings for concrete
panels, there
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are a variety of known shapes and forms f'or such anchoring projections which
have
previously been in conventional use.
The sheet 22 is laid out such that the edge flap portions 28 and 30
extend laterally beyond the lateral extremities of the upper form surface 42
on each
side thereof. In this regard, edge flap portion 30 can be seen in Fig_ 3;
however, edge
flap portion Z8 on the apposite side of shot 2Z is hidden fram view. It is to
be noted
that in Fig. 3, the ribs 44 on edge flap pordan 28 are shown schematically as
single
lines. After sheet 2z has been appropriately positioned relative to upper fonn
surface
42, reinforcing steel 46 is arranged atop sheet 22 and side boards 48 are
installed in
locations for appropriately defining the edges 14, 16 of the slab 12. In this
latter
regard, in the preferred form of the invention illustrated in the drawings and
describai
herein, the side boards 4$ and the edges 14, 16 defined thereby, desirably
extend in
general parallelism with ribs 44. End boards 50 complete the internal
periphery of
form box 40 which is intended to retain vvet cementitious material after it is
pour
and while it is selxing up into a solid form. A quantity of wet cementitious
tnatcrial is
then poured onto the face 26 of sheet 22, appropriately shaped with a curved
screed
board S 1, and thezt allowed to harden to thereby form slab 12. After the slab
12 is
formed, it is clear that the surface 1$ thereof is engaged against the face 26
of sheet
22, and that the T-shaped ribs 44 are emb~ided within the concrete.
As can be appreciated from Figs. 3 and 4 of the drawings, in one
particularly preferred form of the invention, at the time the panels 10 are
formed, the
edges 14, 16 of the slab 12 extend horizoxttally. That is to say, the panel 10
is lying in
a generally horizontal position. Accordingly, in order to use the panels I O
to form a
concrete tank, the same must be erected so that the edges 14, 16 extend in an
upward
direction. Such eroetion rnay be accomplished in a co»ventional manner usi ng
a crane
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ar a hoist or the like. After erection and pt~ior to the completioxr of the
entire tank, the
individual panels I O may be htld is place by respective sets of conventional
braces 52
such as those illustrated in Fig. 5. Conventional weld plates (not shown) may
also be
used to further support the panels 10 during welding of the overlapping
segments 36,
3$. Desirably, the panels 1p may be erected on a concrete base or foundation
33, or
the like which may be lined or unlined.
As is illustrated in Fig- 1, a :plurality of the pre-fabricated pastels IO
may be arranged so as to prasent a tank 20, the interior surFaces of which
will be lined
with a plastic lining upon completion of the construction of the tank. Thus, a
plurality
of the panels 10 may be arranged in an aligned, side.by-side relationship as
shown,
with the elongated edges 14, 16 of adjacent panels 10, which are essentially
coextensive in length, disposed in an opposing, spaced apart relationship so
as to
present the upwardly extending gap 34 thercbetween. As mentioned above,
adjacent
panels 10 are positioned and arranged so that an outboard segment 36 of the
edge hop
portion 30 of the plastic sheet 22 of one panel 1Q is disposed in overlapping
relationship to an outboard segment 38 of the edge flap portion 28 of the
plastic sheet
22 of the adj scent panel 10 at the gap 34. °T"lvis relationship can
best be seen from Fig.
2, where it can also be seen that at least one of the ribs 44 may be removed
ii-om the
outboard segment 36 of edge flap portion 30 so as to avoid interference with
the
welding operation. It should also be noted in connection with the foregoing
that the
ribs 44 on the edge flap portion 28 remain intact so as to provide a secure
connection
between the grouting material 70 and the sheet 22 when the gap 34 is grouted
as
described hereinafter. In further connection with the foregoing, it should be
noted
also from Fig. 1 that the edge flap portions 28, 30, which project outwardly
beyond
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the elongated edges 14, 16, axe desirably coextensive in vertical length with
one
another as well as with the elongated edges 14, 1~.
As described above, the panels 10 are pre-fabricated and arranged in
place after the concrete has become set. Alternatively, in accordance with
another
embodiment of the invention, the panels lit may be formed in sizu in an
already erect
condition. In accordance with this aspect of the invention, and with specific
ccferenee
to Fig. 7, an upstanding form assembly :40 may be employed to construct each
panel
10. corm assembly 140 may be erected on the base pad 33, and the same includes
an
inner form element 142 and an outer foxzn clement 144. These form elements
142,
144 may be made from plywood or other prefabricated form system material and
may
be appropriately curved to simulate the curvature of the completed concrete
structure.
As built, the elements 142, 144 are disposed in a horizontally spaced, facing
relationship so as to preset a concrete finable space 145 therebetween. To
construct
each panel 10 in situ, a plastic sheet 22 is placed over the interior face 146
of form
element I42 with the ribs 44 thereof (not shown iz~ Fig. 7) projecting into
the space
145. R.einforeing steel (not shown in Fig. 7) rcay then be arranged in space
145 and
fluid concrete nay be poured into the space, 145. Upon dryixig, the coz~crcte
poured
into space 145 presents slab 12. Thereafter, the form assembly I40 is removed
to
present an already in place panel 10. As will be appreciated by those skilled
in the
art, a series of laterally spaced and aligned panels 10 may be constructed in
this
manner around the periphery of the tonic. These panels will be spaced apart
laterally
as described above so as to present a gap 34 between adjacent aligned panels
10. In
addition, the plastic sheets extend laterally outwardly beyond the lateral
edges of the
panels as described above so as to present corresponding outboard segment 36,
38
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which may then be welded together in accordance with the concepts and
principles of
the invention.
In another embodiment of the invention, the panels 10 may be formed
using concrete spraying methodology. In accordance with this form of the
invention,
a forrzr assembly similar to the assembly 140 may be used However, in this
c:~se, the
outer forth eltmcnt 1~ is not needed. The c,~onstruction of the panel 10 in
this case
simply involves conSCnlcIirig the form ClCtlac~ tt I a-4, placing the plastic
sheet oveF tl~c
face 146 of the latter with the ribs projecting outwardly, installing the
steel reinforcing
material, and spraying concrete onto the exposed surface of plastic sheet 22.
In each of the embodiments descn'bed above, the anal atxangement of
the panels 10 is as illustrated in Figs. 1 and 2.
Preferably, each gap 34 may vary in width from about 4 inches to
about 20 inches, and desirably the width of the gap 34 should be about 6 to 8
inches_
Advantageously, each of the flap portions 2~, 30 may project laterally and
outwardly
beyond edges 14, 16 of slab 12 for a distance of from about 4 inches to about
20
inches, and ideally the outboard segments 36, 38 should overlap a minimum of 2
inches and a maximum of 10 inches. GenLrally, it is preferred for the
overlapping
segments 36, 38 to be positioned centrally trf the gap 34. In a particularly
prefezred
form o~the invention, the gap 34 may be about 7 inches wide and the Qap
portions 28,
30 may project outwardly beyond the edges 14, 16 of slab 12 for a distance of
about S
inches, whereby the overlap is about 3 inches wide.
The overlapping outboard se,~~ments 36 and 38 may be welded together
in situ using hot air welding, hot gas welding, infrared element welding
andlor wedge
welding. However, wedge welding tnay desirably be used in accordance with the
preferred aspecFs of the invention. A typical wedge welder 56 is illustrated
in Fig. 6
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where it can be seen that the welder 56 includes a main body portion 58 where
the
caz~trols and drive mechanisms are located and a bottont sled portion 60. The
overall
operational characteristics of wedge welders are conventional and well known,
and
such mechanisms are commonly used to weld overlapping, horizontally extending
edge flap portions of adjacent plastic sheets together_ Accordingly, as shown
in Fig.
6, the wedge welder is employed to weld overlapping outboard segments 36 and
38
together using a heated wedge 62 and pinch wheels 64, 66. As is well known,
pinch
wheel 64 may be a driven wheel carried by main body portion 58 while pinch
wheel
66 carriod by bottom sled portion 60 may be either a driven wheel or an idler
wheel.
Conventionally, during operation the wedge welder Sb travels in the direction
of the
arrow 61 in Fig. 6.
In further accordance with the concepts and principles of the present
invention, the overlapping outboard segments 36, 38 of the edge flap portions
28, 30
are welded together in situ using a wedge welder 56. This operation is best
illustrated
in Fig. 2 where it can be seen that the main body portion 58 of the weldc~ 56
is
desirably positioned on the opposite sides c~f the plastic sheets 22 from the
concrete
slabs 12, whereas the bottom sled portion 6~ of the welder 56 is desirably
positioned
within gap 34. The bottom sled portion 60 may desirably bt provided with slots
75
which eoopezate with ribs 44 or other anchoring projections on flap 2$ for
guiding the
welder 56 along the gap 34. Ideally, the wedge welder 56 may be started at the
bottom of each overlapping set of outboaa°d segments 36, 38 and caused
to move
upwardly along the sheets 22 while the segments 36, 38 arc welded together to
produce a continuous, upwardly extending seam 6$, which desirably may vary
from
0.5 inch to 2 inches in width and ideally is about 1 inch in width.
Alternatively, the
welder 56 may be started at tho top and caused to move downwardly along tlZe
ed~es
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of the sheets. In accordance with the particularly preferred form of the
invention
described above where the gap 34 is 7 inches wide, the bottom sled portion 60
may
ideally be about S-G inches wide.
A$er each seam is completed, the gap 34 may desirably be filled with
a grouting material 70 as illustrated schenrratically in Fig. 1. As explained
above, it is
desirable in connection with the invention for anchoring projections 24 tv be
arranged
such that the same project into the gap 34 where they znay be surrounded by
grout
during the grouting pracess. This insures a rigid and secure connection
between the
plastic sheets 22 and the grout. After the gaps 34 are fully grouted, the tank
20 may
be prestressed/post-tensioned using wires or strands (not shown).
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