Note: Descriptions are shown in the official language in which they were submitted.
CA 02904683 2015-09-16
SEISMIC REINFORCED UNDERGROUND WATER CONDUIT
FIELD OF THE INVENTION
[0001] The present invention relates to a method of reinforcing an
underground water
conduit to resist earthquakes and landslides and to a structural reinforcement
device adapted for
insertion into an underground water conduit.
BACKGROUND OF THE INVENTION
[0002] Underground water conduits, either potable water pipes, waste
water pipes or
sewer pipes, are typically made of rigid materials such as reinforced
concrete, cast iron, ductile
iron, steel and hard polymers such as PVC, HDPE, etc. that are durable and
adapted to resist
high internal pressure if required and the weight of the landfill covering
them. Underground
water pipes provide essential services to the urban population, and as a
result of their
geographical dispersion they remain particularly vulnerable to damage caused
by natural
disasters. A network of buried water pipes connected together extends over
long distances,
spreads out in all directions to provide services to residential home or
businesses over a wide
area and may pass through soils having different properties.
[0003] In the event of an earthquake or a landslide, the network of water
pipes is
subjected to variable ground motions along its various segments and
particularly at its various
connections for which it may not have been designed to resist. For example, at
bends, elbow or
tee connections, seismic waves propagating in a certain direction or
landslides moving in a
certain direction, affect the water pipes before and after bends, elbow or tee
connections
differently. Previous major earthquakes revealed that most damage of the
buried segmented
water pipes occurs at the joints and connections of the network of water
pipes. It has been
proven that the differential motions between the pipe segments are one of the
primary reasons
that results in damages and ruptures. With the surrounding soil giving way,
the external forces
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exerted on the water pipe network around bends, elbow and tee connections and
around straight
couplings connecting abutting pipe segments generate high shear and tensile
stresses and
strains that often exceed the elastic limits of the pipes or the pipes
connections leading to
multiple ruptures in the network of water pipes at various points thereby
partially or completely
shutting down water supply to residential home and/or businesses over the area
serviced by the
water network.
[0004] Functioning water systems are a cornerstone of urban human
communities, to
bring in the clean water on demand for drinking, washing and sanitary needs,
and in turn
remove the used water from drains, waste, and storm water sources. If the
water network
system is suddenly rendered partially or totally non-functional by an
earthquake or a landslide,
critical disruption of the community and public health danger may result. In
catastrophic events
such as earthquakes, water supply to the population in the aftermath of the
event is crucial and
must be restored rapidly. However, locating and replacing ruptured or broken
pipe segments
and pipe connections through a vast network is time consuming and requires
heavy machinery
for excavation, removal of damage pipes and connections and installation of
new pipes and
connections.
[0005] Newer networks of underground water conduits built in high risk
areas are
designed to withstand higher shear and tensile stresses and strains such as
those generated by
earthquakes and landslides. However, the vast majority of underground water
networks were
built many decades ago based on lower standards and cannot withstand the high
shear and
tensile stresses and strains generated by earthquakes and landslides.
[0006] Replacing older networks of underground water conduits with new
ones more
adapted to withstand the high shear and tensile stresses and strains generated
by earthquakes
and landslides is unrealistic because of the sheer magnitude of the work that
would be involved.
However, reinforcing existing water networks without the need to excavate
represents a
feasible alternative especially in higher risk areas.
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[0007] Therefore, there is a need for a method of reinforcing underground
water
conduits to resist earthquakes and landslides and to a reinforcement
structural device adapted
for insertion into underground water conduits without having to excavate.
SUMMARY OF THE INVENTION
[0008] It is an object of the present invention to ameliorate at least
some of the
inconveniences present in the prior art.
[0009] In one aspect, the invention provides a structural liner for
reinforcing a network
of underground water conduits, the structural liner comprising a seamless
woven tubular sheath
impregnated with a hardening resin; the seamless woven tubular sheath
comprising longitudinal
fiber warp yarn having a linear mass density of at least 7,000 deniers
providing tensile strength
along a longitudinal axis of the woven tubular sheath and circumferential
fiber filling yarn
having a linear mass density of at least 10,000 deniers oriented substantially
perpendicular to
the longitudinal warp yarn providing tensile strength and stiffness around the
circumference of
the woven tubular sheath.
[0010] In an additional aspect, the warp yarn and filling yarn have a
twists per unit
length in the range of 0.3/inch to 3/inch.
[0011] In an additional aspect, the seamless woven tubular sheath further
comprises
longitudinal fiber warp yarns extending along a first axial direction and
curving to extend along
a second axial direction thereby forming three branches of a T-shaped woven
sheath
specifically adapted to reinforce a tee connection coupling of the network of
underground water
conduits.
[0012] Embodiments of the present invention each have at least one of the
above-
mentioned objects and/or aspects, but do not necessarily have all of them. It
should be
understood that some aspects of the present invention that have resulted from
attempting to
attain the above-mentioned objects may not satisfy these objects and/or may
satisfy other
objects not specifically recited herein.
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[0013] Additional and/or alternative features, aspects, and advantages of
embodiments
of the present invention will become apparent from the following description,
the
accompanying drawings, and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] For a better understanding of the present invention, as well as
other aspects and
further features thereof, reference is made to the following description which
is to be used in
conjunction with the accompanying drawings, where:
[0015] Figure 1 is a schematic top plan view of a typical older network
of underground
water conduits;
[0016] Figure 2 is a schematic view of a structural liner in accordance
with one
embodiment of the invention;
[0017] Figure 3 is a schematic view of the structural liner of Figure 2
positioned inside
two adjacent pipe segments connected together;
[0018] Figure 4 is a schematic view of the structural liner of Figure 2
positioned inside
an elbow connecting two pipe segments;
[0019] Figure 5 is a schematic view of the structural liner of Figure 2
positioned inside
a tee connection connected to three pipe segments;
[0020] Figure 5a is a schematic view of a T-shaped woven sheath in
accordance with
another embodiment of the invention;
[0021] Figure 5b is a schematic view of the T-shaped woven sheath of
Figure 5a
positioned inside a tee connection connected to three pipe segments;
[0022] Figure 6 is a schematic view of the structural liner of Figure 2
positioned inside
a bend of an older network of underground water conduits;
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[0023] Figure 7 is a schematic cross-sectional view of a pipe segment
reinforced with a
structural liner subjected to a bending moment;
[0024] Figure 8 is a schematic cross-sectional view of a pipe segment
reinforced with a
structural liner subjected to a shear force;
[0025] Figure 9 is a schematic cross-sectional view of a pipe segment
reinforced with a
structural liner subjected to an axial pullout force;
[0026] Figure 10 is a schematic side elevational view of a portion of a
network of
underground water conduits;
[0027] Figure 11 is a schematic top plan view of the network of
underground water
conduits illustrated in Figure 10; and
[0028] Figure 12 is a schematic top plan view of the network of
underground water
conduits illustrated in Figures 10 and 11 with the structural liner partially
installed therein.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] Figure 1 is a schematic illustration of a portion of a typical
older network of
underground water conduits 10 comprising a series of straight segments of
pipes 12 joined
together with couplings 14, elbows 16, tee connections 18 and bends 20.
Typical underground
conduits for potable water have diameters ranging from 4 inches to 24 inches
and the more
common diameters range from 6 inches to 12 inches. Underground conduits for
potable water
have multiple small diameters service entrances ranging from 1/2 inch to 2
inches typically in
diameter connected to residences or businesses supplying the end users with
potable water.
[0030] In the event of an earthquake or a landslide, the ground motion
will exert
extreme forces on the water pipe network and the direction of the ground flow
will generate
axial pullout forces and bending moments around the coupling 14, elbow 16, tee
connection 18
and bend 20 due to their specific orientations relative to the direction of
the ground flow
thereby generating high shear and tensile stresses and strains that, at some
connections, will
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exceed the elastic limits of the pipe connections leading to ruptures in the
network of water
pipes at various points.
[0031] As shown in Figure 2, in order to reinforce the network of
underground conduits
particularly at the couplings 14, a structural liner 22 consisting of a
seamless woven tubular
sheath 24 impregnated with a hardening resin was devised which is adapted for
insertion into
the network of underground water conduits 10 without the need to excavate
because the
structural liner 22 remains flexible until its impregnated resin is hardened
after it has been
installed inside the network of underground conduits 10. The seamless woven
tubular sheath 24
consists of continuous longitudinal fiber warp yarns 26 providing tensile
strength along the
longitudinal axis 27 of the woven tubular sheath 24 and circumferential fiber
filling yarn 28
oriented approximately 90 relative to longitudinal warp yarn 26 providing
tensile strength
around the wall 30 of the woven tubular sheath 24 along the perpendicular axis
32.
[0032] The warp yarn 26 and the filling yarn 28 are preferably made of
heavy yarns.
For woven tubular sheath of six (6) inches in diameter, the warp yarn 26 has a
linear mass
density of at least 7,000 deniers and the circumferential filling yarn has a
linear mass density of
at least 10,000 deniers. For woven tubular sheath of eight (8) inches in
diameter, the warp yarn
26 has a linear mass density of at least 9,000 deniers and the circumferential
filling yarn has a
linear mass density of at least 20,000 deniers. For woven tubular sheath of
twelve (12) inches in
diameter, the warp yarn 26 has a linear mass density of at least 20,000
deniers and the
circumferential filling yarn has a linear mass density of at least 30,000
deniers and preferably
40,000 deniers. Heavy yarns having high linear mass density have high tenacity
and tensile
modulus, and moderate to high tensile elongation which are essential
characteristics for
reinforcing underground water conduits to prevent ruptures in the event of an
earthquake.
Furthermore, preferred heavy yarns have fewer twists per unit length than
lower linear mass
density yarns which mechanically improves their wettability. A high number of
twists per unit
length provide a physical barrier against the impregnation of the yarn by the
hardening resin
because there is less space for the hardening resin to penetrate the yarn.
Heavy yarns with twist
per unit length in the range of 0.3/inch to 3/inch are preferred for the
structural liner 22 and
more preferably in the range of 1/inch to 2.5/inch. An improved wettability of
the longitudinal
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fiber warp yarns 26 and of the circumferential fiber filling yarn 28 results
in a better
impregnation of the woven tubular sheath 24 by the hardening resin and
increases the overall
strength of the fiber-resin matrix of the structural liner 22. Heavy yarns
therefore have the
added advantage of being able to absorb a large quantity of hardening resin as
the resin
penetrates easily through the large diameter filaments and the low twist per
unit length of the
bulky yarn. The structural liner 22 is therefore more densely impregnated with
hardening resin
with fewer voids than lower linear mass density yarns thereby generating a
more solid structure
when the resin is hardened.
[0033] The hardening resin may be curable resin such as an epoxy resin,
an unsaturated
polyester resin, a vinyl ester resin, or a urethane based resin, or a
thermoplastic resin such as a
polyolefin, a polyethylene, a polyethylene terephthalate (PET) or technical
resin such as
NYLON, etc.
[0034] The fiber yarn may be made of polyester fibers, fiber glass,
carbon fibers,
aramid fibers, natural fibers such as cellulosic fibers, like flax or hemp
fibers, oriented
polyethylene fibers, polyamide fibers or polypropylene fibers.
[0035] Once in place inside the network of underground conduits 10 and
more
specifically inside the couplings 14 connecting two adjacent pipe segments 12,
the hardening
resin is cured and the structural liner adheres to the inner wall of the pipe
segments 12. The
longitudinal warp yarn 26 of the woven tubular sheath 24 provides added
tensile strength to the
couplings 14 along the longitudinal axis 40 of the two adjacent pipe segments
12 as shown in
Figure 3. This added tensile strength along the longitudinal axis 40 at the
coupling 14 of the
two adjacent pipe segments 12 dramatically increases the deformation limit or
damage
tolerance of the coupling 14 and of the pipe segments 12 thereby enabling the
coupling 14 to
resist the axial pullout forces, the shear forces and the bending moments
generated during an
earthquake or a landslide. The force of the adhesion of the hardening resin to
the inner wall of
the pipe segments also provides additional strength to resist the axial
pullout forces, the shear
forces and the bending moments generated during an earthquake or a landslide.
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[0036] Figure 4 illustrates a structural liner 22 positioned inside an
elbow 16. The
woven tubular sheath 24 being flexible prior to curing the resin impregnated
therein is adapted
to conform to the curvature of the elbow. Once cured in place, the
longitudinal warp yarn 26 of
the woven tubular sheath 24 provides added tensile strength to the couplings
14 connecting the
elbow 16 to the pipe segments 12 along the axial direction 42 and provides
added tensile
strength to the body of the elbow 16. When the elbow 16 and its couplings 14
are subjected to
axial pullout forces, shear forces and bending moments during an earthquake or
a landslide, the
longitudinal warp yarn 26 of the woven tubular sheath 24 increases the
resistance of the
assembly at the points of maximum strain which enables the assembly of elbow
16 and pipe
segments 12 to remain together even if the elbow is subject to deformation.
[0037] Figure 5 illustrates a tee connections 18 connected to three pipe
segments 12.
Due to the particular configuration of a tee connection, the structural liner
22 cannot reinforce
the central portion 44 of the tee connection 18 without blocking one of the
branches 46, 48 or
50. However, it is possible to reinforce the couplings 14 connecting the
branches 46, 48 and 50
to the pipe segments 12 by inserting structural liners 22 from the pipe
segments 12 and ending
each structural liner 22 at the junctions of the branches 46, 48 or 50 to the
central portion 44 of
the tee connection 18 as illustrated. In this manner, the longitudinal warp
yarn 26 of the woven
tubular sheath 24 of the structural liners 22 provides added tensile strength
at least to the
couplings 14 connecting the tee connection 18 to the pipe segments 12 along
the axial
directions 52 and 54 where the axial pullout forces, shear forces and bending
moments are
highest during an earthquake or a landslide.
[0038] Figure 5a illustrates a T-shaped woven sheath 25 specifically
adapted to
reinforce the central portion 44 of the tee connection 18. The woven sheath 25
comprises
longitudinal fiber warp yarns 26 extending along the axial directions 52 and
longitudinal fiber
warp yarns 29 also extending along the axial directions 52 and curving at the
central portion 31
to extend along the axial direction 54 thereby forming the branches 47, 49 and
51 of the T-
shaped woven sheath 25. The longitudinal fiber warp yarns 26 and 29 are held
together with
circumferential fiber filling yarn 28 oriented nearly 90 relative to
longitudinal warp yarns 26
and 29.
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[0039] In operation, the T-shaped woven sheath 25 is impregnated with the
hardening
resin and is inserted into the central portion 44 of the tee connection 18
prior to the insertion of
the structural liners 22 into the branches 46, 48 and 50. The T-shaped woven
sheath 25 is soft
and malleable and can be positioned in the central portion 44 of the tee
connection 18.
Thereafter, a tubular shaping device is introduced into the branches 47, 49
and 51 of the T-
shaped woven sheath 25 that push the branches 47, 49 and 51 of T-shaped woven
sheath 25
outwardly against the inner walls of the branches 46, 48 and 50 of the tee
connection 18 such
that the branches 47, 49 and 51 temporarily adhere to the inner walls of the
branches 46, 48 and
50 of the tee connection 18 through the uncured resin in order to initially
shape the T-shaped
woven sheath 25 without curing its resin. Once the T-shaped woven sheath 25 is
properly
shaped, the structural liners 22 are inserted into the pipe segments 12 and
extend into the
branches 47, 49 and 51 of the T-shaped woven sheath 25 such that the branches
47, 49 and 51
of the T-shaped woven sheath 25 overlap the ends of each structural liner 22
at the junctions of
the branches 46, 48 or 50 to the central portion 44 of the tee connection 18
as illustrated in
Figure 5a.
[0040] Figure 6 illustrates a structural liner 22 positioned inside a
bend 20. As
previously described relative to structural liner 22 positioned inside an
elbow 16, the woven
tubular sheath 24 being flexible prior to curing the resin impregnated therein
is adapted to
conform to the curvature of the bend 20. Once cured in place, the longitudinal
warp yarn 26 of
the woven tubular sheath 24 provides added tensile strength to the bend 20 and
to the pipe
segments 12 extending from the bend along the axial direction 56. When the
bend 20 is
subjected to axial pullout forces, shear forces and bending moments during an
earthquake or a
landslide, the longitudinal warp yarn 26 of the woven tubular sheath 24
increases the resistance
of the bend 20 at the points of maximum strain enabling the bend 20 to resist
the high tensile
strains and stresses generated even if it is subjected to partial deformation.
[0041] With reference to Figure 7, which illustrates a pipe segment 12
subjected to a
bending moment M, the pipe segment 12 has bent and has fractured and separated
at the bend
75 under the localised tension force Tf . However, the structural liner 22
inside the pipe
segment 12 has remained intact under the bending moment M due to its
flexibility and its
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ability to sustain deformation. The structural liner 22 has stretched at the
fracture point and
maintained the integrity of the fractured pipe segment 12. The result is that
in the aftermath of
an earthquake or a landslide, the underground water conduit remains
operational.
[0042] With reference to Figure 8, which illustrates a pipe segment 12
subjected to a
shear force St- perpendicular to the longitudinal axis of the pipe segment 12,
the pipe segment
12 has fractured and separated under the shear force Sf. However, as can be
seen, the structural
liner 22 inside the pipe segment 12 has remained intact under shear force Sf
due to its flexibility
and its ability to sustain deformation. The structural liner 22 has bent at
the fracture point and
conformed to the displacement of the fractured pipe segment 12. The result is
that in the
aftermath of an earthquake or a landslide, the underground water conduit
remains operational.
[0043] With reference to Figure 9, which illustrates a pipe segment 12
subjected to
subjected to an axial pullout force Pf along its longitudinal axis, the pipe
segment 12 has
fractured and separated under the pullout force Pf. However, as can be seen,
the structural liner
22 inside the pipe segment 12 has remained intact under pullout force Pf due
to its flexibility
and its ability to sustain deformation. The structural liner 22 has stretched
at the fracture point
and maintained the integrity of the fractured pipe segment 12. The result is
that in the aftermath
of an earthquake or a landslide, the underground water conduit remains
operational.
[0044] With reference to Figure 10, which illustrates a side view of a
portion of a
typical older network of underground water conduits 10 comprising a series of
straight
segments of pipes 12 joined together with couplings 14, elbows 16, tee
connections 18 and
Figure 11 which is a plan view of the same portion of the network of
underground water
conduits 10 illustrated in Figure 10, a winch cable 62 is initially inserted
into the network of
underground water conduits 10 entering through first pipe segment 64 connected
above ground
to a fire hydrant for example and exiting through a second pipe segment 66
connected above
ground to another fire hydrant for example. The structural liner 22 comprising
the woven
tubular sheath 24 impregnated with resin is then attached to the winch cable
62 and pulled into
the network 10 by a winching device (not shown) attached to the cable 62. The
flexibility of the
structural device 22 allows it to be pulled through the first tee connection
18a and through the
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first and second elbows 16a and 16b as illustrated. The structural liner 22 is
pulled through the
whole length of the portion of the network of underground water conduits 10 in
this manner.
[0045] As previously mentioned with reference to a tee connection 18, the
structural
liner 22 cannot be pulled into the central portion 44 of the tee connection
18b without blocking
one of its branches. The front end of the structural liner 22 is therefore
pulled up to the
junction of the branch 48 and the central portion 44 of the tee connection 18b
and released.
Similarly, the length of the structural liner 22 is calculated such that its
rear end is located at the
junction of the branch 50 and the central portion 44 of the tee connection
18a. A T-shaped
woven sheath 25 as described with reference to Figures 5a and 5b is used in
order to reinforce
the central portion 44 of the tee connections 18a and 18b. As shown in Figures
10 and 11, a T-
shaped woven sheath 25 was first inserted in the tee connections 18a and 18b
and shaped with a
tubular shaping device such that the branches 47, 49 and 51 of the T-shaped
woven sheath 25
temporarily adhere to the inner walls of the branches 46, 48 and 50 of the tee
connections 18a
and 18b prior to the insertion of the structural liner 22. Thereafter, the
structural liner 22 of a
specific length corresponding to the distance between the junction of branch
48 and the central
portion 44 of the tee connection 18b and the junction of the branch 50 and the
central portion
44 of the tee connection 18a is inserted through the T-shaped woven sheath 25
and pulled
through the network of underground water conduits 10 such that the branches of
the T-shaped
woven sheath 25 overlap the ends of the structural liner 22 prior to curing.
[0046] Figures 10 and 11 illustrate and describe a pull-in-place process
of installing the
structural liner 22 into network of underground water conduits 10. However, an
inversion
process may also be used in which the resin impregnated structural liner 22 is
inverted and
pushed inside the water conduits 10 by applying hydrostatic or air pressure
against the internal
walls of the structural liner 22 such that the structural liner 22 reverses
and deploys right side
up against the walls of the water conduits 10.
[0047] After the insertion of the structural liner 22 into the portion of
the network of
underground water conduits 10, the woven tubular sheath 24 impregnated with
resin is resting
flat on the bottom of the water conduits 10 and must be shaped to take its
final tubular form in
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order to rest against the inner walls of the pipe segments 12 and couplings
14, elbows 16 and
the couplings of the branches 48 and 50 of the tee connections 18a and 18b.
The shaping of the
structural liner 22 against the inner walls of the network of underground
water conduits 10 is
accomplished by passing a shaping member or pig 70 through a first T-shaped
woven sheath 25
which is preferably pushed along the structural liner 22 by pressurized water.
The pig 70
pushes the woven tubular sheath 24 outwardly against the inner walls of the
pipe segments 12
and couplings 14, elbows 16 and the couplings of the branches 48 and 50 of the
tee connections
18a and 18b and assumes its final tubular shape.
[0048] After the shaping of the structural liner 22 against the inner
walls of the network
of underground water conduits 10, the curable resin of the structural liner 22
and of the T-
shaped woven sheaths 25 is cured in place. The curing of the resin is
preferably achieved by the
effect of the passage of hot pressurised water through the structural liner 22
and the T-shaped
woven sheaths 25. The transfer of the heat from the water to the curable resin
allows the cross-
linking reaction to take place, and thus the curing of the resin. The curing
of the resin maintains
the woven tubular sheath 24 in its tubular shape and provides mechanical
integrity and rigidity
to the structural liner 22 and the T-shaped woven sheaths 25. Furthermore, the
curing of the
resin permanently bonds the woven tubular sheath 24 and the T-shaped woven
sheaths 25 to the
inner walls of the network of underground water conduits 10.
[0049] If a structural liner 22 pre-impregnated with a thermoplastic
resin or comprising
a thermoplastic resin in the form of comingled fibres is used, the
thermoplastic is consolidated
through heating and pressurizing for a given period of time by means of
pressurized hot water,
steam or hot air or other means to bring the thermoplastic to its
consolidation point i.e. slightly
above its melting temperature, in order for it to melt, wet-out the fibres of
the structural liner,
and solidify upon cooling, resulting in a structural thermoplastic composite
liner.
[0050] Once installed and cured, the structural liner 22 and the T-shaped
woven sheath
25 reinforce the entire network of underground water conduits 10 and more
specifically around
the couplings 14, elbows 16, tee connections 18 and bends 20 which are more
susceptible to
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breakage under the axial pullout forces, shear forces and bending moments
generated by
earthquakes and landslides.
[0051]
Modifications and improvements to the above-described embodiments of the
present invention may become apparent to those skilled in the art. The
foregoing description is
intended to be exemplary rather than limiting. The scope of the present
invention is therefore
intended to be limited solely by the scope of the appended claims.
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