Note: Descriptions are shown in the official language in which they were submitted.
CA 02648820 2009-01-02
CONTROLLED SYSTEM FOR THE DENSIFICATION OF WEAK SOILS
TECHNICAL FIELD
[0001] This document relates to controlled systems for the densification of
weak
soils, and more specifically to a bag system for densifying weak soils in a
controlled fashion.
BACKGROUND
[0002] A traditional method of densifying base soils, called pressure grouting
or
permeation grouting, involves forcing a high density cementitious material
under high
pressure into the base soils with a view to increase the bearing capacity of
the soils.
However, in the case of weak soils there is no controlling of the amount of
grout that is
required and as such, extreme amounts of grout can be pressure pumped into the
soils with
limited or no positive results. This is especially true in the case of highly
saturated soils.
[0003] An alternative method of densifying soils is the injection of expanding
polymer resins directly into the base soils, as for example described in EP 0
851 064 Al.
This typically works when the soils are relatively strong but in the case of
weak to very weak
soils that are saturated, enormous amounts of expanding polymer resin are
required which
once again makes it uneconomical due to the lack of control as to where the
resins are
expanding to.
[0004] Another alternative method of densifying weak soils involves driving a
pre-
formed member made of wood, or any other strong material, into the soils,
densifying the
soil through the displacement of the soil by the driven member. Although this
system has
merit, it is very intrusive and especially damaging to the surface soils as
the driven members
have to be of significant diameter and must be driven from the surface.
SUMMARY
[0005] A method of imparting strength to earth in support of a ground surface
is
disclosed. A bag is placed in the earth under the ground surface, the bag
having a first end
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oriented towards the ground surface, a second end opposite the first end, and
a cross
sectional contour from the first end to the second end that includes at least
one wedge
portion extendable laterally into surrounding earth located above and below
the wedge
portion when the bag is filled. Expandable polymeric resin is injected into
the bag to at least
partially fill the bag to compress earth around the bag.
[0006] A bag is also disclosed for use in imparting strength to earth in
support of a
ground surface. The bag comprises at least an opening, a first end and a
second end opposed
the first end, and a cross sectional contour from the first end to the second
end that includes
at least one wedge portion extendable laterally into surrounding earth above
and below the
wedge portion when the bag is filled and in earth under the ground surface.
[0007] A method of imparting strength to earth in support of a ground surface
is also
disclosed. A first bag and a second bag are placed in the earth under the
ground spaced along
an injection tube inserted through the second bag and into the first bag.
Expandable
polymeric resin is injected into the first bag from an injection end of the
injection tube to
compress the earth around the first bag. The injection end is removed from the
first bag and
expandable polymeric resin injected into the second bag from the injection end
to compress
the earth around the second bag. The injection tube is removed from the second
bag. In some
embodiments, the method further comprises drilling a hole in the earth with a
hollow drill
stem connected to a sacrificial drill bit, and in which placing further
comprises placing the
first bag, second bag, and injection tube in the hollow drill stem under the
ground surface.
The hollow drill stem is then removed from over the first bag prior to
injection of the first
bag.
[0008] A method of imparting strength to earth in support of a ground surface
is also
disclosed. A first bag is placed in a first layer of earth below the ground
surface. A second
bag is placed in a second layer of earth below the ground surface. Expandable
polymeric
resin is injected into each of the first bag and second bag to at least
partially fill the first bag
and second bag to compress the earth around the first bag and second bag,
respectively, and
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to form a support stack of bags. The first layer is weaker than the second
layer, and a
maximum lateral cross sectional area of the first bag is larger than a maximum
lateral cross
sectional area of the second bag.
[0009] A method of densifying weak earth at least partially saturated with
water and
in support of a ground surface is also disclosed. A first bag is placed in the
weak earth below
a first location of the ground surface and expandable polymeric resin injected
to at least
partially fill the first bag and to compress weak earth around the first bag.
A second bag is
placed in the weak earth below a second location of the ground surface and
expandable
polymeric resin injected to at least partially fill the second bag and to
compress weak earth
around the second bag. After a pre-determined amount of time to allow the
first bag and the
second bag to at least partially drive out water from the weak earth between
the first bag and
the second bag, a third bag is placed in the weak earth below a third location
of the ground
surface in between the first location and the second location and expandable
polymeric resin
is injected to at least partially fill the third bag and to compress weak
earth around the third
bag.
[0010] A further method involves inserting a bag or an array of bags of
predetermined shape and size into a pre-drilled hole to a predetermined depth,
air filling the
bag or bags to allow for free flow of an expanding polymeric resin thereby
allowing the
expanding resin to be confined yet allowing the expanding confinement bag to
compact,
compress and densify the soils in proximity to the confinement bag(s) to
increase bearing
capacity of soils beneath foundation support systems.
[0011] In a further method, a geotechnical survey is carried out on weak soils
to
determine a profile of soil weakness. A bag or stack of bags is then placed in
the weak soils
and injected with an expanding polymeric resin to compress the weak soils
around the bag or
stack of bags. The bag or stack of bags is selected to have a shape that
conforms to the soil
weakness profile such that a portion of the bag or stack of bags placed in a
weaker layer of
the weak soils has a greater diameter than another portion of the bag or stack
of bags placed
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in a stronger layer of the weak soils. The portions of the bags or bags having
the greater
diameter may provide a bridge between stronger layers of soil. The portions
with greater
diameter thus form wedges that provide the bridging function.
[0012] Various applications of these methods include the densification of weak
soils
beneath foundation footings, concrete floor slabs, perimeter thickened or non-
thickened
concrete slab-on-grade slabs, asphalt and concrete pavements, walks, and
railroad track for
example. Methods as disclosed herein may be used as methods of replacing the
pre-loading
of weak soils at construction sites. In use, the wedge portions extend between
layers of soil
and form a supportive bridge between the layers.
[0013] These and other aspects of the device and method are set out in the
claims,
which are incorporated here by reference.
BRIEF DESCRIPTION OF THE FIGURES
[0014] Embodiments will now be described with reference to the figures, in
which
like reference characters denote like elements, by way of example, and in
which:
[0015] Figs. 1-5 are side elevation views, in section and not to scale, of
earth under a
ground surface and illustrating a process forming a support stack of plural
bags in earth
under a ground surface.
[0016] Fig. 6 is a perspective view, partially in section and not to scale,
that
illustrates an opening in a bag housing a back-flow prevention valve.
[0017] Fig. 7 is a side elevation view, in section and not to scale, of earth
under a
ground surface containing a support stack of four bags.
[0018] Figs. 8-9 are perspective views, in section and not to scale, of earth
under a
ground surface and illustrating a method of placing support stacks of at least
one bag.
[0019] Figs. 10-11 are side elevation views, in section and not to scale, that
illustrate
a further method of placing support stacks of at least one bag.
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[0020] Fig. 12 is a side elevation view, in section and not to scale, that
illustrates an
embodiment of a support stack with two bags, in which one bag has an hourglass
cross
section, and the other bag has a bulged midsection, as well as a soil weakness
profile of the
soil of illustrated.
[0021] Figs. 13-15 are flow diagrams that illustrate various methods of
imparting
strength to earth under a ground surface.
[0022] Fig. 16 is a flow diagram that illustrates a method of densifying weak
earth at
least partially saturated with water and in support of a ground surface.
[0023] Figs. 17A and 17B are side elevation views, in section and not to
scale, that
illustrate the placement and filling, respectively, of a bag in the earth.
[0024] Figs. 18-19 are side elevation views, in section and not to scale, that
illustrate
the formation of a support stack of bags.
[0025] Fig. 20 is a side elevation view, in section and not to scale, that
illustrates the
first and second bags from Fig. 18 fully filled out of the ground.
[0026] Fig. 21 is a perspective view, in section and not to scale, that
illustrates a bag
with an annular wedge portion.
[0027] Fig. 22 is a perspective view, in section and not to scale, that
illustrates a bag
with an arm.
[0028] Fig. 23 is a flow diagram that illustrates a method of imparting
strength to
weak soils in support of a ground surface.
DETAILED DESCRIPTION
[0029] Immaterial modifications may be made to the embodiments described here
without departing from what is covered by the claims.
[0030] This document relates to the construction of in-situ expandable
vertical/horizontal support member(s) in weak base soils as a means of
densifying the weak
base soils for supporting and under-pinning structures on these soils. For
example, these
methods and apparatuses may carry out the densification of foundation soils
support systems
for buildings, walks, bridge approaches, concrete or asphalt paved roads, rail
beds, and any
CA 02648820 2009-01-02
other structure requiring a base support system or requiring enhancement or
strengthening of
the existing soil-based support system.
[0031] The present disclosure is directed to providing a controlled method of
densifying soils at depth to increase bearing capacity of the weak soils as an
alternative to
pressure grouting and to direct injection of expanding polymer resins into
weak base soils.
Weak alluvial soils and silts replete with peat, hog fuel, and other weak
sediments that may
be highly saturated and demonstrative of Standard Penetration Test N-values of
5 or lower
are examples of soils that this disclosure relates to.
[0032] In many types of weak soils, such as weak alluvial soils, silts, clay,
peat, hog
fuel, wood chips, and water saturated soils for example, the inherent strength
of the earth
below the ground surface is limited. Soils of these types are known to have
caused hazardous
situations such as standing derailments of trains, and the cracking of
foundations of various
structures. In order to stabilize these types of soils, and prevent such
incidents from occuring,
the earth below the ground surface must be strengthened.
[0033] Referring to Fig. 17A, a bag 10 is illustrated for use in imparting
strength to
earth 14 in support of a ground surface 16. Bag 10 may be made of non-
expandible material,
for example thick polymer material. Referring to Fig. 17B, the material may
resist the
expansion of the bag itself, thus compressing the inside and outside of the
bag while
maintaining structural integrity. In some embodiments, the bag is made of
resilient material.
Bag 10 may be filled underground with an expandable polymeric resin that fills
bag 10 to
compress and densify the adjacent earth. The expandable polymeric resin reacts
to expand
and fill bag 10, compressing and densifying as it does so. By densifying and
strengthening
the weak adjacent soils, the weight bearing capacity of the ground surface 16
is increased,
and overlying structures may be more easily stabilized and built on top.
Referring to Figs.
17A and 17B, bag 10 has at least an opening 24 through which an injection tube
18 (shown
in Fig. 2) is inserted to dispense the expandable polymeric resin. It should
be understood that
the injection tube need not be a tube.
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[0034] Referring to Fig. 13, a method of imparting strength to earth in
support of a
ground surface is illustrated. Referring to Fig. 2, in a stage 100 (shown in
Fig. 13), a first bag
and a second bag 12 are placed in the earth 14 under the ground 16 spaced
along an
injection tube 18 inserted through the second bag 12 and into the first bag
10. The injection
tube 18 may be inserted through the second bag 12 through openings 20, 22, and
into first
bag 10 through opening 24. The bags 10, 12 may form an array of non-
symmetrical
containment bags vertically placed one on top of each other to the appropriate
depth. Bags
10, 12, and injection tube 18 may be placed in the earth 14 through a hole 34.
Referring to
Fig. 1, an embodiment is illustrated where hole 34 is drilled. Hole 34 may be
drilled by a
conventional means, in which the drilling device (not shown) is removed upon
completion of
the hole and prior to placement of bags 10, 12, and tube 18. In other
embodiments, hole 34
may be drilled in the earth using a hollow drill stem 36 connected to a
sacrificial drill bit 38.
This embodiment is described in greater detail below.
[0035] Referring to Fig. 4, in stage 102 (shown in Fig. 13) expandable
polymeric
resin 25 is then injected into the first bag 10 from an injection end 26 of
the injection tube 18
to compress the earth 28 around the first bag 10. Referring to Fig. 3, prior
to injecting
expandable polymeric resin 25 into the first bag 10, gas, for example
compressed air, may be
injected to at least partially fill the first bag 10. Each containment bag may
be expanded in-
situ as much as possible using compressed air to allow as easy as possible
filling of each bag
with a predetermined amount of expandable polymeric resin. In some
embodiments, the
expandable polymeric resin is added as a liquid and fills the containment
bag(s) through the
expansion of the polymeric resin, the balloon effect on the containment bags
compacting and
compressing the base soils surrounding the containment bag(s). By filling the
first bag 10
with air prior to injection, the expandable polymeric resin is allowed to free
flow into bag 10
and properly fill, yet be confined by, the dimensions of bag 10 upon
expansion. Each bag 10,
12 may be expanded in-situ as much as possible using compressed air to allow
as easy as
possible filling of each bag with a predetermined amount of expandable
polymeric resin. The
predetermined amount of liquid resin injected may be an amount much smaller
than the fully
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expanded volume of the bag, depending on the expansion ratio of the resin
used. Referring to
Figs. 3 and 4, injection of the expandable polymeric resin may proceed first
with injection
end 26 of tube 18 near the base of first bag 10 (shown in Fig. 3). Once bag 10
has begun to
fill up, injection end 26 is gradually drawn up towards opening 24. The
predetermined
amount of resin may be hydro-insensitive polyurethane for example.
[0036] Referring to Fig. 5, in stage 104 (shown in Fig. 13), the injection end
26 is
removed from the first bag 10 and expandable polymeric resin 30 injected into
the second
bag 12 from the injection end 26 to compress and compact the surrounding
solids, for
example earth 32, around the second bag 12, thereby increasing the bearing
capacity of the
soils being treated. A pre-determined amount of expandable polymeric resin 25
may be
injected into bag 10. Referring to Fig. 4, opening 24 of first bag 10 may
comprise a backflow
prevention valve 40. Valve 40 may be provided to prevent material contained
within the bag
from passing out of the bag 10 when the opening 24 is unobstructed. Valve 40
allows the
injection tube to be threaded through, but once the injection tube 18 has been
removed the
valve will close and not allow expandable polymeric resin to escape from the
containment
bag. Valve 40 is sized to accept the passage of injection tube 18. Normally,
valve 40 may be
biased to close opening 24, unless tube 18 is extending through opening 24.
Valve 40 is
illustrated in Fig. 6, and described in detail below. Referring to Fig. 5,
once tube 18 is
removed from bag 10, valve 40 closes and prevents any expandable polymeric
resin pressure
from expandable polymeric resin 25 from passing out of bag 10 through opening
24, for
example into second bag 12. This is especially useful when the expandable
polymeric resin
used is expanding polymeric resin. The valves and openings used may be of
sufficient
diameter to allow the injection probe to freely move through.
[0037] Referring to Fig. 13, in stage 106, the injection tube 18 is removed
from the
second bag 12. Bag 12 may be filled in much the same fashion as bag 10.
Similarly,
openings 20, 22 of bag 12 may have valves 42, 44, respectively, which may
function the
same as valve 40. In some embodiments, at least one of valves 40, 42, and 44
are at least
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partially threaded on to tube 18. In such embodiments, tube 18 must be
unscrewed out of the
respective valve.
[0038] Referring to Fig. 12, in some embodiments first bag 10 and second bag
12 are
connected. Bags 10 and 12 may be connected via a sleeve 46, for example a
polymer
connector, through which injection probe 18 (not shown) may be passed through
both bags
10, 12. In such embodiments, it may only be necessary to provide one backflow
prevention
valve on sleeve 46.
[0039] Referring to Fig. 14, a further method of imparting strength to earth
14 in
support of a ground surface 16 is disclosed. Referring to Figs. 18-19, this
method is
illustrated. Referring to Fig. 18, in stage 108 (shown in Fig. 14), first bag
10 is placed in a
first layer 48 of earth 14 below the ground surface 16. A second bag 12 is
placed in a second
layer 50 of earth 14 below the ground surface 16. Referring to Fig. 12, this
is also illustrated
as first bag 10 is placed predominantly in first layer 48, and second bag 12
is placed
predominantly in second layer 50. Referring to Fig. 19, in stage 110 (shown in
Fig. 14)
expandable polymeric resin 25, 30 is injected into the first bag 10 and second
bag 12,
respesctively, to at least partially fill the first bag 10 and second bag 12
to compress the earth
14 around the first bag 10 and second bag 12, respectively, and to form a
support stack 52 of
bags. In this embodiment, the first layer 48 is weaker than the second layer
50, and referring
to Fig. 20, a maximum lateral cross sectional area 54 of the first bag 10 is
larger than a
maximum lateral cross sectional area 56 of the second bag 12. Referring to
Fig. 20, in some
embodiments, first bag 10 has a larger maximum width than second bag 12. This
method
takes advantage of the lower density of weaker soil layers, as larger volume
bags may be
spaced to align within weaker soils. This allows further densification of the
weak soils to
take place than would be the case if the same size bag was used for the entire
support stack
52.
[0040] Referring to Fig. 15, a further embodiment of methods of imparting
strength
to earth in support of a ground surface is illustrated. This method may be
illustrated with
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reference to Fig. 12, despite the fact that Fig. 12 illustrates bag 12 in a
filled state. Referring
to Fig. 12, in stage 116 (shown in Fig. 15), bag 12 is placed in the earth 14
under the ground
surface 16. Bag 12 has a first end 58 oriented towards the ground surface 16,
and a second
end 60 opposite the first end 58. Bag 12 also has a cross sectional contour 62
from the first
end 58 to the second end 60 that includes at least one wedge portion 64
extendable laterally
into surrounding earth 14 located above and below the wedge portion 64 when
the bag 12 is
filled. Wedge portion may be between the first end 58 and the second end 60 of
the bag. This
method may also be illustrated with reference to bag 10 in Fig. 12, as bag 10
includes a
wedge portion 64. Wedge portion 64 may extend laterally into soil, for example
layer 48 to
bridge the soil above and below the wedge portion 64. In the example shown,
wedge portion
64 on bag 10 extends into weak layer 48 and bridges between soil layers above
and below
layer 48. In stage 118, expandable polymeric resin 25 is injected into the bag
12, for example
through an opening (not shown) to at least partially fill the bag 12 to
compress earth around
the bag 12. Wedge portion 64 is used to extend into and wedge between earth 14
adjacent the
bag, increasing the structural effectiveness of the bag and densifying the
soil. This is
contrasted with a traditional bag shape, which merely compresses the adjacent
soil. Wedge
portion 64 is understood to be defined by a portion only of the cross-
sectional contour
between ends 58 and 60, and not the entire vertical contour itself. This way,
wedge portion
64 effectively fingers laterally into the surrounding earth, compressing
adjacent soil
vertically as well as horizontally and bridging between soil above and below
wedge portion
64. This type of friction pile is also more effective at forming a support
stack than a stack of
conventional bags, because it is harder to vertically displace due to the
lateral interaction
with the adjacent soil by the wedge portion(s).
[0041] The method illustrated in Fig. 15 is particularly useful for densifying
particularly narrow strata of weak soil, such as layer 48 in Fig. 12. Because
a weak layer
may be short enough vertically that a bag positioned within such a layer will
extend beyond
the layer as illustrated, this method allows a portion of the bag to be
modified to target the
small weak layer and provide more compression to it. In some embodiments, the
wedge
portion 64 is oriented in a first strata 48 of earth 14 over a second strata
68, the first strata 48
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of earth being weaker than the second strata 68. This method allows a bag 10
to ledge over
and be shouldered by an underlying layer of earth. For example, in Fig. 12,
wedge portion 64
effectively sits over earth layer 68, which is stronger and denser than layer
48. Referring to
Fig. 12, this may also be illustrated as bag 12 may have an hourglass cross
sectional contour
66 from the first end 58 to the second end 60. In some embodiments, wedge
portion 64
comprises a sloped ledge 71. The bag may also have at least two wedge
portions, for
example wedge portion 64 and 70 illustrated for bag 12. Referring to Fig. 21,
wedge portion
64 may comprises an annular portion. As illustrated, the wedge portion 64 may
comprise a
bulged cross sectional contour when the bag is filled. This is also
illustrated in Fig. 12 with
bag 10. Referring to Fig. 22, wedge portion 64 may comprise an arm 72. Arm 72
may be
useful for targeting an inconsistent layer of weak soil.
[0042] Referring to Fig. 12, placing may further comprise placing the bag 12
in the
earth 14 with an injection tube (not shown) inserted through an opening (not
shown) of the
bag 12, and in injecting may further comprise injecting expandable polymeric
resin into the
bag from an injection end of the injection tube. This is illustrated in the
embodiments shown
in Fig. 4 for example. Similarly, the injection end may be removed from the
bag. Referring
to Fig. 6, the bag 10 may further comprises a backflow prevention valve 40 to
prevent
material contained within the bag 10 from passing out of the bag 10 when the
opening 24 is
unobstructed. Valved opening 24 may comprise a rigid flange 41.
[0043] Referring to Fig. 12, also disclosed is a structural support 74 for a
ground
surface 16 comprising the confinement bag 12 located in earth 14 under the
ground surface
16 and at least partially filled with the expandable polymeric resin 25 to
compress the earth
14 around the bag 10.
[0044] Referring to Fig. 1, in some embodiments of the methods disclosed
herein, a
hole 34 may be initially drilled in earth 14 with a hollow drill stem 36
connected to a
sacrificial drill bit 38. Referring to Fig. 2, in these methods, the injection
tube 18, along with
at least one of the first bag 10, and second bag 12 are placed in the hollow
drill stem 36
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under the ground surface 16. In some weak soils, the hollow drill stem may be
required to
prevent the drilled hole from collapsing prior to placement of the bags.
Referring to Fig. 3,
the hollow drill stem 36 (shown in Fig. 2) is at least removed from over the
first bag 10 prior
to injection of the first bag 10. In the embodiment illustrated in Fig. 3, the
hollow drill stem
36 is completely removed at this stage. In other embodiments, the hollow drill
stem 36 may
be removed enough to clear each bag one at a time as the cleared bag has
expandable
polymeric resin injected into it.
[0045] Referring to Fig. 16, a method of densifying weak earth at least
partially
saturated with water and in support of a ground surface is detailed. Referring
to Figs. 10-11,
this is illustrated. Referring to Fig. 10, in stage 120 (shown in Fig. 16), a
first bag 74 is
placed in the weak earth below a first location 76 of the ground surface 16
and expandable
polymeric resin 25 is injected to at least partially fill the first bag 74 and
to compress weak
earth around the first bag 74. In stage 122, a second bag 78 is placed in the
weak earth below
a second location 80 of the ground surface 16 and expandable polymeric resin
25 is injected
to at least partially fill the second bag 78 and to compress weak earth around
the second bag
78. A pre-determined amount of time is then elapsed to allow the compression
from first bag
74 and the second bag 78 to at least partially drive out water 82 from weak
earth between the
first bag 74 and the second bag 78. Referring to Fig. 11, in stage 124 (shown
in Fig. 16),
after the pre-determined amount of time a third bag 84 is placed in the weak
earth below a
third location 86 of the ground surface 16 in between the first location 76
and the second
location 80 and expandable polymeric resin 25 is injected to at least
partially fill the third
bag 84 and to compress weak earth around the third bag 84. Referring to Fig.
10, the
placement of bags 74 and 78 is close enough such that water 82 is driven out
along lines 88
for example. In some embodiments, the first location 76 and the second
location 80 are any
suitable distance apart, for example less than 10, 20 feet apart. As
illustrated in Fig. 11, the
third location 86 may be centrally located between the first location 76 and
the second
location 80.
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[0046] Referring to Fig. 8, in one embodiment of the method, prior to
placement of
the third bag 84, a fourth bag 90 is placed in the weak earth below a fourth
location 92 of the
ground surface 16 and expandable polymeric resin 25 is injected to at least
partially fill the
fourth bag 90 and to compress weak earth around the fourth bag 90. The fourth
bag 90 acts
to at least partially drive out water 82 from weak earth between the first bag
74, the second
bag 78, and the fourth bag 90 during the pre-determined amount of time.
Referring to Fig. 9,
the third position 86 is in between the first position 76, second position 80,
and fourth
position 92. In this way, a triangle of bags may be employed, and the third
bag 84 placed in
between the triangle.
[0047] Referring to Fig. 8, in a further embodiment of the method, prior to
placement
of the third bag 84, a fifth bag 94 is placed in the weak earth below a fifth
location 96 of the
ground surface 16 and expandable polymeric resin 25 is injected to at least
partially fill the
fifth bag 94 and to compress weak earth around the fifth bag 94. The fifth bag
94 acts to at
least partially drive out water 82 from weak earth between the first bag 74,
the second bag
78, the fourth bag 90, and the fifth bag 94 during the pre-determined amount
of time.
Referring to Fig. 9, the third position 86 is in between the first position
76, second position
80, fourth position 92 and fifth position 96. In this way, a grid of bags may
be placed to drive
out water from in between prior to placement of the final bag. Once the final
bag is placed,
the final bag acts to further drive out water from in between the final bag
and the prior placed
bags, thus drying the soil at least in part and imparting strength to the
soil. The separation of
the bags may be the same as the separation between the first and second bags
74, 78 for
example. An appropriate grid system of these containment bags may be placed
under
whatever structure requires under-pinning and support. Further bag supports
may be placed
in between the already placed bags after a further pre-determined amount of
time.
[0048] In some embodiments, the pre-determined amount of time is any suitable
amount of time, for example more than 4, 8 hours. As illustrated in Figs. 10-
11, the steps of
placing the bags may actually involve placing stacks of bags by, for example
using the
methods disclosed in this document. This method may further comprise removing
water
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from between the first bag and the second bag through at least one relief hole
23. Relief hole
23 may be drilled near enough to at least one of bags 74, 78 to relieve the
water pressure that
has been increased due to the placement and expansion of the bags. A pump (not
shown)
may be used to further aid in the removal of water from between the bags.
[0049] In some of the embodiments of methods disclosed herein, the earth
comprises
at least one of weak alluvial soils, silts, clay, peat, hog fuel, wood chips,
and water saturated
soils. It should be understood that each method disclosed herein can
incorporate all the
characteristics of the other methods. Weak soils may have Standard Penetration
Test blow
counts (N-values) of between 0 to 10, for further example 0-8.
[0050] In the embodiments of the methods disclosed herein, the expandable
polymeric resin may be expanding polymeric resin that comprises a high
density, closed cell
expanding two component polyurethane foam system. The resin may be hydro-
insensitive. In
some embodiments, the polymeric resin is a high density, two-part, closed cell
expanding
polymeric resin system, such as a polyurethane system which is injected into
the
confinement bag or array of confinement bags. The particular foam system used
may be
tailored to meet specific design applications relating to tensile strength,
compressive
strength, shear strength, flexural strength and other structural
characteristics to meet the
specific design applications of the controlled foam densification system. It
is also possible to
use other expandable substances having similar properties.
[0051] The expansion rate of the freely blown polymeric resin system is known
as is
the approximate relationship of the expanding polymeric resin system under
confinement in
a weak soils condition and hence the amount of resin can be pre-estimated to
minimize resin
usage and maximize soils densification around the confinement bag or array of
confinement
bags.
[0052] The shape and size of containment bags, constructed of natural or
synthetic
fibers for example, will be determined depending upon the soils conditions.
The weaker the
14
CA 02648820 2009-01-02
soil's condition, the larger the containment bag may be in both width and
depth. The
containment bags will typically not be symmetrical in shape to enhance the
stability of the
filled bag in the weak soils as well as enhance any "friction" effect the
containment bag may
have. The containment bags may be designed to meet specific soils needs, for
example using
a containment bag in a specifically weak soil strata that has been designed to
more so
compact the weak soil as compared to the soils above and below the weak
strata.
[0053] In some embodiments of the methods disclosed therein, various
placements of
bags as support stacks may be employed. The grid for placement of the
expanding
stabilization members for densifying soils under any structure will depend
upon the structure
and the weakness of the soils, and to what depth the weak soils exist at. For
example, for
densifying soils beneath a railroad track a typical grid may be a staggered
grid pattern under
each track at four foot intervals to a depth of twelve feet comprising an
array of three hour-
glass shaped containment bags one on top of the other. In some embodiments,
testing is
carried out on the soil layers below the ground surface to determine exactly
where to place
the bags.
[0054] Referring to Fig. 1, the diameter of the drill stem 36 and the
sacrificial drill
head 38 may be variable in dimension. Referring to Fig. 2, in that the drill
head will be
sacrificed (left at the bottom of the hole), the bag or array of bags complete
with injection
tube can be inserted into the vacant drill stem and then the drill stem
removed leaving the
bag or array of bags in the weak soils.
[0055] As described above, in some embodiments the expandable polymeric resin
used may be an expandable polymeric resin. A positive benefit of this is that
expanding
polymeric resin systems set up extremely quickly and allow for immediate use
of the
structure shortly after completion of the soils densification. Although it is
recognized that
because of the extreme expansive nature of these resin systems, the
containment bags may
rupture, because of the rapidity with which the resins set up this should not
materially effect
the densification of the soils around the containment bag. Referring to Fig.
4, the pre-
CA 02648820 2009-01-02
determined amount of expandable polymeric resin 25 may be selected to
partially rupture the
bag 10.
[0056] A further positive benefit of the foam bag containment system used to
densify
weak base soils is that the expanding polymer resin is light weight, for
example in the range
of 300 lbs per cubic meter. Thus, the use of expandable polymeric resin does
not contribute a
severe weight or over-burden effect on the weak soils being densified.
Further, in
embodiments where the polymer resin is a closed cell material, water
permeation is not a
consideration. This is a significant factor in the event the containment bag
splits and the
weak soils being treated are saturated, since such ruptured supports will not
lose their
function, that is to compress and compact the adjacent soils.
[0057] In some embodiments of these methods, the first bag and second bag are
injected with expandable polymeric resin until full. Referring to Fig. 7, any
number of bags
may be used with the methods disclosed herein, for example four bags lOA-D as
illustrated.
Referring to Fig. 12, the methods disclosed herein may be used to strengthen
earth 14 in
support of a railroad track 97 on ground surface 16. As illustrated, the bags
may be placed
adjacent the railroad track 97, in order to not disturb the track itself. In
other embodiments, a
hole may be drilled directly underneath the tracks 97, and the bag or bags
inserted through
the hole and injected. Regardless, the methods disclosed herein represent a
non-intrusive
method of providing support to earth under a ground surface.
[0058] In a further method illustrated in Fig. 23, in a stage 126 a
geotechnical survey
is carried out on weak soils to determine a pattern or profile of soil
weakness. Referring to
Fig. 12, an exemplary profile 131 is indicated of the soil weakness of the
soils of Fig. 12.
The profile 131 illustrates the relative weakness of the soil, which may be
plotted using for
example negative N-values obtained at spaced intervals below the surface 16.
As an
illustration, region 132 corresponds to layer 48, indicating a weak region or
layer of soil
relative to the surrounding regions 134 and 136. In a stage 128 (shown in Fig.
23), a bag or
16
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stack of bags (for example bags 10, 12) is placed in the weak soils. The bag
or stack of bags
is selected to have a shape that conforms to the soil weakness profile 131,
such that a portion
of the bag or stack of bags placed in a weaker layer of the weak soils has a
greater diameter
than another portion of the bag or stack of bags placed in a stronger layer of
the weak soils.
For example, bag 10 is selected to have a portion (illustrated as portion 64)
that has a greater
diameter than portion 67. Portion 64 is placed in the weaker region 132, while
portion 67 is
placed in stronger region 134. The bag or stack of bags is then injected in
stage 130 (shown
in Fig. 23) with an expanding polymeric resin to compress the weak soils
around the bag or
stack of bags. The soil weakness profile will have at least one weak region
adjacent at least
one stronger region, and this will mean that the bags will have at least one
larger diameter
portion adjacent a smaller diameter portion. In some embodiments the larger
diameter
portion (for example portion 64) placed in the weaker layer forms a supportive
bridge
between stronger layers of soil, for example regions 134 and 136. In other
embodiments, the
stronger layer (for example region 140) may be clamped by two large diameter
portions (for
example portions 64 and 70 of bag 12) positioned in surrounding weak regions,
such as
regions 138 and 134, respectively. A smaller diameter portion (for example
portion 69) is
positioned in the strong region. The portions with greater diameter thus form
wedges that
provide the bridging or clamping function. Referring to Fig. 19, as
illustrated, the portion
placed in the weaker layer may comprise at least one bag, for example bag 10.
As illustrated,
the shape of the bag or bags does not have to exactly conform to the profile,
but should be
tailored maximize the strength of the weak soils.
[0059] Some methods disclosed herein relate to the use of pre-designed
containment
bags dependent upon geo-technical data received on the weak soils to be
treated. The
containment elements will be irregular in shape to more effectively densify
the weak soils
and also to provide additional vertical strength to the ground surface.
[0060] In the claims, the word "comprising" is used in its inclusive sense and
does
not exclude other elements being present. The indefinite article "a" before a
claim feature
does not exclude more than one of the feature being present. Each one of the
individual
17
CA 02648820 2009-01-02
features described here may be used in one or more embodiments and is not, by
virtue only
of being described here, to be construed as essential to all embodiments as
defined by the
claims.
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