Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a collapsible tunnel
liner section and to a method of lining tunnels using
collapsible liner sections.
Tunnels, particularly those having a medium
diameter (5 to 12 ~eet) are commonly used to carry water
and sewage, and also to carry services such as power and
communication conduits. Such tunnels are currently normally
constructed in one of two ways. In one o~ the common methods,
a removable mold is constructed within an underground tunnel,
and concrete is then injected between the exterior wallstof
the mold and the walls of the -tunnel. After the concrete has
set, the mold is disassembled and moved along to the head of
the tunnel where it is again erected. The constant erection
and disassembly of the mold is expensive and time consuming.
Typical such removable molds are disclosed in U.S. patents
Nos. 1,137,44~; 1,320,199; 1,702,646; 1,716,125; and
1,734,773.
In the other assembly method which is commonly
in use, segments of concrete tunnel liner sections are
transported one at a time into the tunnel and are then assembled
by a machine at the tunnel head, to form a complete concrete
liner section. Grout is then injected between the exterior of
the liner section and the tunnel and hardens to ~orm a mono-
lithic structure with the liner section. The disadvantage of
this method is that assembly of the liner segments within the
tunnel requires use of an expensive specially designed
machine and requires stoppage of excavation for prolonged
periods while a liner section is being assembled.
The present invention provides a hinged
collapsible closed loop tunnel liner section which in collapsed
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form is small enough in cross section to be transported
into the tunnel through the previously erected liner sections.
When the collapsed tunnel liner section reaches the desired
location, it is erected b~ expanding the expansion means
located within the collapsed section. After the collapsible
liner section has been erected and put into position, grout
or other filler material is then inserted between the liner
section and the tunnel wall. The same procedure may be used
for vertical shafts (which however will usually be grouted),
and the term "tunnel" as used herein is intended to include
horizontal, sloping and vertical shafts.
Further objects and advantages of the invention
will appear from the following descriptions of preferred
embodiments of the invention, taken together with the accom-
panying drawings, in which:
Fig. 1 is a sectional view showing a number of
tunnel liner sections according to the invention in position
in a tunnel;
Fig. 2 is an end view showing a tunnel liner
section of the invention in erected condition;
Fig. 2A is a sectional view through the joint
between two segments;
Fig. 3 is an end view of the tunnel liner
section of Fig. 2 in collapsed condition prior to erection
and located on a cart within an erected tunnel liner section;
Fig. 4 is an end view similar to that of
Fig. 3 and showing an alternative method of transporting the
tunnel liner section of Fig. 2 through a tunnel;
Fig. 5 is an end view showing the tunnel liner
section of Fig~ 2 in partially erected condition and showing
the temporary oversize of the section;
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Fig. 6 is an end view showing a modified
tunnel liner section in collapsed condition, located within
an erected similar tunnel liner section;
Fig. 7 is an end view showing a still further
modified tunnel liner section in collapsed condition, located
within an erected similar tunnel ]iner section;
Fig. 8 is an end view showing a still further
modified tunnel liner section in collapsed condition, located
within an erected similar tunnel liner section;
Fig. 9 is a perspective view showing elastic
strap detail for the tunnel liner section of Fig. 8;
Fig. 10 is a sectional ~iew showing the tunnel
liner sections of the invention being assembled within a
mine shaft;
Fig. 11 is an end view showing a still further
modified tunnel liner section in collapsed condition, located
within an erected similar tunnel liner section; and
Fig. 12 is an end view showing yet another
modified tunnel liner section, in erected condition.
Reference is first made to Fig. 1, which shows
a tunnel 10 which has been cut through ground 12 by conventional
means. The tunnel 10 is typically a medium diameter tunnel,
for example 5 to 12 feet in diameter. A cylindrical tunnel
liner 14 is positioned within the tunnel 10, the liner
14 consisting of a number of identical sections 16 constructed
as will be described. The liner sections 16 may have keyed
end portions 18 for alignment purposes. Grout 20 is injected
in the space 22 between the exterior of the liner sections 16
and the ground 12 to form a monolithic tunnel structure.
As shown in Fig. 2, each tunnel liner section
16 is a closed loop (i.e. it is not open ended) and consists
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o~ eight identical arcuate concre~e segments 24, numbered
as 24-1 to 24-8 in the drawings. Each arcuate segment 24
extends over an arc of 45 degrees and has a keyed end 26
for better engagement with its neighbouring segments. The
segments 24 are connected together by flexible hinges 28-1
to 28-8, which may be elastomer or metal strip hinges glued
orotherwise secured to the segments. A11 the hinges are
located along the interior of the segments 24, except for
the side hinges 2~ 3 and 28-7, which are located at the
exterior of the segments. For example, as shown in Fig. 2A,
the hinges may be welded or clamped to the circumferential
reinforcing steel rods 29 used to reinforce the segments.
The rods 29 are exposed at the ends of the segments for this
purpose.
The tunnel liner section 16 is shown in
collapsed condition in Fig. 3. In its collapsed condition
the tunnel liner section is indicated at 16', to differentiate
it from the liner section in its erected condition. As shown
in Fig. 3, the collapsed liner sectlon 16' still forms a
closed loop, i.e. a line traced alon~ the respec~ive segments
in their numerical order is endless. However, the collapsed
liner section 16l is now arranged in a compact stack having
generally the form of a figure 3, in which segments 24-1,
24-2, 24~7 and 24-8 form the top portion of the "eight" and
the segments 24-3, 24-4, 24-5 and 24-6 form the bottom portion~
The top portion of the "eight" contains an upper cavity 30,
and the lower portion contains a lower cavity 32. Two air
bags 34, 36 are provided, one located within each cavity 30,
32.
It will be seen, as shown in Fig. 3, that in
its collapsed condition the liner section 16' has (as viewed
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from its end)across section in which the maximum
dimension is less than the interior diameter of the erected
liner section 16'. Therefore, the collapsed section 16'
may be transported axially through the partly finished tunnel
on a cart 38 having wheels 40. Alternatively, provided
that the length of the liner section 16' is made short
enough, it may be transported in the position shown in Fig.
which is rotated 90 degrees in a horizontal plane ~rom that
shown in Fig. 3 , and greater clearances may be provided in
this manner, by suitably adjus~ing the length of the liner
section 16'.
When the collapsed liner section 16l has been
brought to the head of the tunnel, it is erected by inflating
the air bags 3~, 36 in conventional manner. In the
embodiment shown in Figs. 1 to 3, the air bags 34, 36 will
normally be inflated together at the same time, to expand
the liner section gradually as shown in Fig. 5.
It will be seen that the design of the liner
section 16' is such that during expansion, its maximum
height increases beyond tha~ of the finished liner section
and then decreases to that of the ~inished liner section.
This is because during the expansion procedure, the upper ;~
segments 24-1 and 24-8 move upwardly, away from the lower
segments 24-4 and 24-5, and the exterior side hinges 28-2
and 28-7 move outwardly/ away from each other. At the
intermediate stage of erection shown in Fig. 5, the side
segments 24-6 and 24-7 have reached a stage in which they
are generally vertically aligned and in which the hinges
28-6, 28-7 and ?8-8 are aligned in a straight vertical line,
indicated by dotted line 42. At this point the maxim~n
interior diameter Dl of the partly erected liner section
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16' exceeds the interior diameter D2 of the erected liner
section 16. Then, as the hinges 28-7 and 28-2 continue to
move outwardly, the upper segments 24-1 and 24-8 move back
toward segments 24-4 and 24-5, and the liner section assumes
its final circular form.
The temporary oversize condition of the liner
section 16' is essential in the embodiment illustrated, to
provide a stable form when the liner section is in fully
erected condition. The temporary oversize condition may
be contrasted with a conventional collapsible interior
tunnel mold which must not expand past its erected position
during the erection procedure, since it could not then be
removed. The extent of the temporary oversize of the liner
section of the invention is rnodest and may be ascertained as
follows. In the temporary oversize condition, the vertical
distance between hinges 28-7 and 28-8 is simply the dimension
x between the two hinges. In the final erected condition,
the vertical distance y -(Fig. 3) between hinges 28-7 and
28-8 is x sine A where A is the angle (Fig. 3) between the
line joining hinges 28-7 and 28-8 and the horizontal (angle
A in the Figs. 1 to 3 embodiment will be slightly less than
45 degrees). The difference in height between the oversize
condition and the final erected condition is 2x~1-sine A) or
about .6x if angle A is nearly 45 degrees. This modest
oversize will normally be accommodated by the oversized
tunnel cross section which is normally provided to ensure
adequate room for grout.
After each liner section 16' has been erected,
it is moved axially into contact with its neighbouring
liner section 16 and aligned therewith. Grout 20 is then
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injected by conventional means between the newly installed
liner section and the earth 12. The grout adheres to the
exterior of the newly erected liner section 16 and forms
with the section 16 a monolithic structure.
It will be seen that very little stress is
imposed on the hinges 28. The hinges are used to hold the
segments 24 of the liner section in the desired form in the
collapsed condition of the liner section and also to guide
the liner segments during the expansion. Once the liner
I0 section has been erected, it is essentially self supporting
and the stress on the hinges 28 is minimal. Any residual
stress is largely removed after the grout 20 has been
injected and has hardened. By use of the method shown,
complete closed loop liner sections can be brought through
the tunnel into position and erected quickly, easily and
inexpensively, without the need for costly and bulky
assembly equipment located within the tunnel.
I~ desired, and as shown in Fig. 6, the upper
liner sections 24-1 and 24-8 may be joined as one monolithic
arcuate concrete segment 24 1,8 extending over a 90 degree
arc, and the bottom segments 24-4, 24 5 may be formed as a
single similar arcuate segment 24-4,5. This method elimina~es
two sets of hinges but does require the production of two
different kinds of segments. In the Fig. 6 embodiment, the
ends 26a of the segments are simply formed as planar surfaces.
In addition, air bag 34 can if desired be replaced by two con-
nected air bags and the same can be done for air bag 36. This
will improve the control over the shape of the air bags as they
are erected. The connected air bags can be secured together in
conventional manner, e.g. by being sewn, or by heat bonding.
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Reference is next made to Fig. 7, whic~shows a further embodiment of the invention. ~s shown in
Fig. 7, the liner section, indicated erected at 50 and
collapsed at 50', is formed from an upper arcuate concrete
segment 52-1 extending over 60 degrees of arc, an opposed
lower arcuate concrete segment 52-2 also extending over
60 degrees of arc, and eight intermediate concrete segments
52-3 to 52-10 each extending over 30 degrees of arc. As
shown, in collapsed condition the four segments 52-3 to
52-6 are arranged in a vertical sub-stack 54 at the right
hand side of the collapsed liner section/ and the four
segments 52-7 to 52-10 are arranged in a vertical sub-stack
56 at the left hand side of the collapsed liner. Elastomeric
hinges 58-1 to 58~10 are provided to hinge the sections
together, the hinges being fastened to the concrete in
conventional manner (e.g. by glue). To achieve the collapsed
configuration shown, in which the sub-stacks 54, 56 have a
rectangular form as viewed from the:ir ends, hinges 58-2, 58-4,
58-7 and 58-9 are located on the exterior of the liner section
50 as erected, and the remaining hin~es are loca~ed on the
interior of the liner section 50. It will be seen that
hinge 58-2, for example, is fastened to segments 52-3 and
52-4 at contact points 58-21, 58-22 located on the exterior
surfaces of the segments. The length between these contact
points along the hinge is equal to the arc length along the
segments between the contact points, so the hinge will simply
extend along the outside surfaces of the segments when the
section is erected.
In the Fig. 7 embodiment, a temporary block
or support 60 is provided, located on the concave surface of
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the bottom segments 52-2, to support the two sub-stacks 5~,
56. Seven air bags 62-1 to 62-7 are provided for erection,
located within the cavities formed by opposed concave
surfaces of the segments, and all connected to each other for
better control of their shape during erection. The air bags
may be inflated in an appropriate sequence to achieve stable
erection of the liner section 50'. For example seven hoses
and a distributor (not shown) may be used to direct air to the
desired air bags. It will be seen that during erection of
the Fig. 7 embodiment, the air bags should be slightly over-
inflated and then as they are collapsed, the section will
settle back to its final erected condition. The same system
of connecting multiple air bags together may be used in the
other embodiments described and has the added advantage of
reducing the likelihood of chipping the edges of the segments.
Reference is next made to Fig. 8, which shows
a collapsed liner section 70' located within a corresponding
erected liner section 70~ As shown, the liner section 70,
70' resembles the liner section ~0, 50' except that the
segments 52-1 and 52-2 have each been divided into two equal
parts and folded. Specifically, liner 70, 70' includes
twelve arcuate concrete segments 72-1 to 72-12 each extending
over 30 degrees of arc, and arranged in two sub-stacks 74, 76
of six segments each. Each sub-stack is generally rectangular
in form as viewed from its end, resulting in very substantial
clearances at the sides and top and bottom of the collapsed
liner 70'. In the Fig. 8 embodiment the hinge means used
may consist of two or more elastic straps best shown at 74
in Fig. 9. Each strap 74 has a number of relatively short
portions 76 which are secured one to each concrete segment by
a suitable adhesive. The remainder o each strap 74 is not
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bonded to the segments slnce this would inhibit stretching
of the straps 74. However, strap guides may be provided,
consisting of wire loops 78, one set into the exterior of
each segment.
In the collapsed condition of the liner, the
elastic straps 74 follow a tortuous path as indicated in
Fig. 8, the points of adherence 76 preferably being located
near one hinge point of each segment. Six air bags 82-1
to 82-6 are located within the cavities formed between the
opposing concave surfaces of the segments. When the air
bags are inflated, the collapsed liner section 70' expands
through an intermediate oversized condition of the kind
previously described, to the final erected condition shown
at 70. The straps 74 may also be used in the embodiments
previously described. If desired, the air bags 82 1 to
82-6 may be connected to each other or to a central air bag
like air bag 62-3 shown in the Fig. 7 embodiment.
When the collapsible liner sections of the
invention are used in tunnel shafts, the procedure is
essentially the same as that previously described, except,
as shown in Fig. 10, each liner section 86 (which may be
any of the forms described)is lowered in collapsed condition
on cables 88 to the desired position, where it is supported
on temporary shoring 90. While thus supported, the liner
section 86 is then expanded by its air bags (not shown) and
is then grouted. Gaps 91 may he left between ad~acent
sections to facilitate groubing. A plug 92 is installed
around the bottom exterior o~ the expanded liner section 86
(after the expansion has been completed) to retain the
grouting.
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In some cases it may be desirable that the
liner as it is being erected not expand to an oversized
condition even temporarily. In this event, the liner
section 100 shown in Fig. 11 (and shown at 100' in collapsed
condition) may be used~ In the liner section, six arcuate
segments 102-1 to 102-6 are used. The upper and lower
se~ments 102-1 and 102-4 are each 60 degrees in arcuate
length. However, the four intermediate segments 102-2,
102-3, 102-5, 102-6 are of somewhat lesser than 30 degrees
in arcuate length. The ends of adjacent intermediate
segments 102-2 and 102-3, 102-5 and 102-6 are connected
together by wide elongated flexible elastomer hinges 104-1,
104-2, glued to the segments at points 104-la, 104-lb, 104-2a,
104-2b. Therefore, when the liner section 100' is erected,
longitudinal gaps 106, 108 occur between the ends of segments
102-2, 102-3 and 102-5, 102-6. The gaps 106, 108 may then
be filled with concrete plugs 110, 112 which may be cast in
place or may be precast and then inserted. Since the liner
sections are relatively short, the precast plugs may be
inserted from the end.
Although the erected tunnel liner sections have
been shown as having a circular cross section, it will be
realized that they can have a different erected cross section,
for example elliptical or horse-shoe shaped. In addition,
while the segments have been shown as annular, they can be
thickened at locations of increased stress, as sho~n for
example in Fig. 12. In the Fig. 12 embodiment the interior
ofthe liner section 120 remains of circular cross section,
but the exterior has been thickened or arched at the top,
bottom and sides as indicated at 122, to provide greater
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strength. The segments need not be symmetrical or equal
in length but may be varied, and the hinging arrangement may
be varied as required (for example in the Figs. 2 and 3
embodiment, hinges 2~-1 and 28-5 may be on the exterior of
the segrnents to allow a slight "peaking" at the top and
bottom of the section during erection).
If desired, instead of concrete gro~ting,
other means may be used to fill the gap between the exterior
of the liner sections and the tunnel wall. For example,
urethane foam may be used, and this will also insulate the
liner. Alternatively, where the tunnel is accurately
bored (e.g. by a drilling machine in hard ground), precast
bars or blocks rnay be inserted between the exterior of the
liner sections and the tunnel wall. Any gaps between the
bars or blocks may be left or may be grouted or filled with
foam, depending on the requirements of the tunnel in question.
Although air bags have been shown as a means
for erecting the tunnel liner sections, it will be realized
that other expansion means can be used. In additiQn, although
the tunnel liner sections have been sho~n as being made from
concrete, it will be realized that other suitabl~ strong
materials can be used.
