Note: Descriptions are shown in the official language in which they were submitted.
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METHODS AND APPARATUSES FOR COMPACTING SOIL AND GRANULAR
MATERIALS
CROSS-REFERENCE TO RELATED APPLICATIONS
The presently disclosed subject matter is related and claims priority to U.S.
Patent
Application No. 17/171,664 filed on February 9, 2021; the entire disclosure of
which is
incorporated herein by reference.
TECHNICAL FIELD
The presently disclosed subject matter relates generally to the compaction and
densification of granular subsurface materials and more particularly to
methods and
apparatuses for compacting soil and granular materials that are either
naturally deposited
or consist of man-placed fill materials for the subsequent support of
structures, such as
buildings, foundations, floor slabs, walls, embankments, pavements, and other
improvements.
BACKGROUND
Heavy or settlement sensitive facilities that are located in areas containing
soft,
loose, or weak soils are often supported on deep foundations. Such deep
foundations are
typically made from driven pilings or concrete piers installed after drilling.
The deep
foundations are designed to transfer structural loads through the soft soils
to more
competent soil strata. Deep foundations are often relatively expensive when
compared
to other construction methods.
Another way to support such structures is to excavate out the soft, loose, or
weak
soils and then fill the excavation with more competent material. The entire
area under
the building foundation is normally excavated and replaced to the depth of the
soft,
loose, or weak soil. This method is advantageous because it is performed with
conventional earthwork methods, but has the disadvantages of being costly when
performed in urban areas and may require that costly dewatering or shoring be
performed to stabilize the excavation.
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Yet another way to support such structures is to treat the soil with "deep
dynamic
compaction" consisting of dropping a heavy weight on the ground surface. The
weight
is dropped from a sufficient height to cause a large compression wave to
develop in the
soil. The compression wave compacts the soil, provided the soil is of a
sufficient
gradation to be treatable. A variety of weight shapes are available to achieve
compaction by this method, such as those described in U.S. Patent No.
6,505,998.
While deep dynamic compaction may be economical for certain sites, it has the
disadvantage that it induces large waves as a result of the weight hitting the
ground.
These waves may be damaging to structures. The technique is deficient because
it is
only applicable to a small band of soil gradations (particle sizes) and is not
suitable for
materials with appreciable fine-sized particles.
In recent years, aggregate columns have been increasingly used to support
structures located in areas containing soft soils. The columns are designed to
reinforce
and strengthen the soft layer and minimize resulting settlements. The columns
are
constructed using a variety of methods including the drilling and tamping
method
described in U.S. Patent Nos. 5,249,892 and 6,354,766; the tamper head driven
mandrel
method described in U.S. Patent No. 7,226,246; the tamper head driven mandrel
with
restrictor elements method described in U.S. Patent No. 7,604,437; and the
driven
tapered mandrel method described in U.S. Patent No. 7,326,004; the entire
disclosures of
which are incorporated by reference in their entirety.
The short aggregate column method (U.S. Patent Nos. 5,249,892 and 6,354,766),
which includes drilling or excavating a cavity, is an effective foundation
solution when
installed in cohesive soils where the sidewall stability of the hole is easily
maintained.
The method generally consists of: a) drilling a generally cylindrical cavity
or hole in the
foundation soil (typically around 30 inches); b) compacting the soil at the
bottom of the
cavity; c) installing a relatively thin lift of aggregate into the cavity
(typically around 12-
18 inches); d) tamping the aggregate lift with a specially designed beveled
tamper head;
and e) repeating the process to form an aggregate column generally extending
to the
ground surface. Fundamental to the process is the application of sufficient
energy to the
beveled tamper head such that the process builds up lateral stresses within
the matrix
soil up along the sides of the cavity during the sequential tamping. This
lateral stress
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build up is important because it decreases the compressibility of the matrix
soils and
allows applied loads to be efficiently transferred to the matrix soils during
column
loading.
The tamper head driven mandrel method (U.S. Patent No. 7,226,246) is a
displacement form of the short aggregate column method. This method generally
consists of driving a hollow pipe (mandrel) into the ground without the need
for drilling.
The pipe is fitted with a tamper head at the bottom which has a greater
diameter than the
pipe and which has a flat bottom and beveled sides. The mandrel is driven to
the design
bottom of column elevation, filled with aggregate and then lifted, allowing
the aggregate
to flow out of the pipe and into the cavity created by withdrawing the
mandrel. The
tamper head is then driven back down into the aggregate to compact the
aggregate. The
flat bottom shape of the tamper head compacts the aggregate; the beveled sides
force the
aggregate into the sidewalls of the hole thereby increasing the lateral
stresses in the
surrounding ground. The tamper head driven mandrel with restrictor elements
method
(U.S. Patent No. 7,604,437) uses a plurality of restrictor elements installed
within the
tamper head 112 to restrict the backflow of aggregate into the tamper head
during
compaction.
The driven tapered mandrel method (U.S. Patent No. 7,326,004) is another means
of creating an aggregate column with a displacement mandrel. In this case, the
shape of
.. the mandrel is a truncated cone, larger at the top than at the bottom, with
a taper angle of
about 1 to about 5 degrees from vertical. The mandrel is driven into the
ground, causing
the matrix soil to displace downwardly and laterally during driving. After
reaching the
design bottom of the column elevation, the mandrel is withdrawn, leaving a
cone shaped
cavity in the ground. The conical shape of the mandrel allows for temporarily
stabilizing of the sidewalls of the hole such that aggregate may be introduced
into the
cavity from the ground surface. After placing a lift of aggregate, the mandrel
is re-
driven downward into the aggregate to compact the aggregate and force it
sideways into
the sidewalls of the hole. Sometimes, a larger mandrel is used to compact the
aggregate
near the top of the column.
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SUMMARY
The present disclosure relates generally to an apparatus for densifying and
compacting granular materials. In some embodiments, the apparatus may include
a
closed end drive shaft and one or more diametric expansion elements. The
diametric
expansion elements, in their expanded state, may form compaction surfaces
having a
diameter greater that he diameter of the drive shaft. The diametric expansion
elements
may be attached to a bottom surface of the drive shaft, or attached to a base
plate attached
to the bottom end of the drive shaft. The base plate may be changeable.
The diametric expansion elements may include any one or more of chains,
cables,
wire rope, and/or a lattice of vertically and/or horizontally connected
chains, cables, or
wire rope. The diametric expansion elements may be configured and sized
accordingly to
achieve desired lift thickness, compaction surface area, and/or soil flow
based on material
type and/or project requirements. Additionally, the diametric expansion
elements may be
housed within a sacrificial tip that may be releasably connected to a bottom
portion of the
drive shaft. The apparatus may also include one or more wing structures
attached to the
drive shaft that are configured to loosen free-field soils around the drive
shaft.
In certain other embodiments, the apparatus may include a drive shaft, a
compaction chamber at a lower end of the drive shaft, and one or more
diametric
expansion elements, wherein the apparatus further includes an opening in an
upper
surface of the compaction chamber forming a flow-through passage exterior of
the drive
shaft and configured for accepting granular materials from outside of the
drive shaft. The
drive shaft may be the same size and/or diameter, a larger size and/or
diameter, or a
smaller size and/or diameter than the compaction chamber. Additionally, the
compaction
chamber may be connected to the drive shaft through a load transfer plate, and
may
further incorporate one or more stiffener plates connected to the drive shaft
and the load
transfer plate.
Certain embodiments of the apparatus may include one or more diametric
expansion and restriction elements attached to one or both of an interior or
exterior of the
compaction chamber. The one or more diametric expansion and restriction
elements may
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also be attached to the load transfer plate. The apparatus may include both
interior
diametric restriction elements and exterior diametric expansion elements.
Moreover, the
interior diametric restriction elements and exterior diametric expansion
elements may or
may not be connected to one another. The drive shaft may include a hollow
tube, a
substantially I-beam configuration that may further include an opening in the
I-beam
configuration, or a solid cylindrical shaft configuration. The apparatus may
further be
configured to be inserted in a pre-drilled cavity.
In certain other aspects of the present disclosure, an apparatus for
densifying and
compacting granular materials is presented according to other embodiments. The
apparatus may include a drive shaft, a compaction chamber, and one or more
diametric
restriction elements, wherein the compaction chamber comprises a pipe and the
drive
shaft is fitted into one end of the pipe. The apparatus may be configured to
be inserted in
a pre-drilled cavity. In some embodiments, the drive shaft includes an I-Beam
configuration, and may further include an opening in the I-Beam configuration
wherein at
least a portion of the opening in the drive shaft may extend into the pipe.
Certain
embodiments may also include a reinforcing ring fitted around a bottom end of
the
compaction chamber, and may further include a substantially ring-shaped
wearing pad
abutting the reinforcement ring.
Embodiments of the apparatus may also include a ring that may be secured to
the
compaction chamber and positioned near the end of the drive shaft that
includes an
arrangement of the diametric restriction elements. A second arrangement of
diametric
restriction elements may be secured to the drive shaft. The ring may be
optionally
removable.
In certain other embodiments, the apparatus may include a drive pipe affixed
to a
lower end of the drive shaft, wherein a bottom end of the drive pipe may
extend into the
compaction chamber, and further wherein the drive pipe may secured to the
compaction
chamber by one or more struts or plates extending from sides of the compaction
chamber
radially inward to the drive pipe. The one or more struts or plates may extend
along the
drive pipe above the compaction chamber to a termination point, tapering from
the sides
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of the compaction chamber to the termination point. Additionally, a bottom end
of the
drive pipe may be closed using a plate or cap and the plate or cap extends
below a lower
end of the one or more struts or plates.
Other embodiments of the apparatus may also include a perimeter ring inside
the
.. compaction chamber, the ring including an arrangement of the diametric
restriction
elements and being disposed along the inner perimeter of the compaction
chamber at
substantially the lower end of the one or more struts or plates. The ring may
be
removable. The apparatus may also include diametric restriction elements that
are
coupled to the lower end of the one or more struts or plates and the perimeter
of the plate
.. or cap.
In still other embodiments, an air injection line extending along the drive
shaft
with at least one discharge port along the mandrel may be used to provide
positive air
pressure required for increasing interior and/or exterior aggregate flow
during
installations. The discharge port may be located, for example, along the drive
shaft at a
location above the compaction chamber. Certain other embodiments may include
multiple air injection lines with one or more discharge ports along the drive
shaft. In such
embodiments, the discharge ports may be oriented such that the air pressure is
directed
outwards towards the soil cavity to facilitate exterior aggregate flow,
inwards towards the
drive shaft or downwards along the drive shaft to facilitate interior
aggregate flow, or a
combination thereof.
Certain other aspects of the present disclosure include a method of densifying
and
compacting granular materials, the method including the steps of (a) providing
a
compaction apparatus comprising a closed end drive shaft having a first
diameter and one
or more diametric expansion elements, wherein the one or more diametric
expansion
elements expand when the apparatus is driven downward forming compaction
surfaces
having a second diameter greater than the first diameter of the drive shaft,
(b) driving the
compaction apparatus into free-field soils to a specified depth, (c) lifting
the compaction
apparatus a specified distance, and (d) repeating the driving and lifting of
the compaction
apparatus. The method may also include repeating the driving and lifting steps
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incrementally until the compaction apparatus has been lifted to or near an
original ground
elevation. In such embodiments, each of the repeated driving of the compaction
apparatus
may be to a distance generally less than a distance the compaction apparatus
was
previously lifted.
Driving of the compaction apparatus may be effectuated using one of an impact
or
vibratory hammer. In certain embodiments, the lifting of the compaction
apparatus
allows for surrounding materials to flow around the compaction apparatus to
fill a void
created by lifting the compaction apparatus. In some embodiments, the one or
more
diametric expansion elements may be placed within a sacrificial tip and upon
the initial
lifting of the compaction apparatus the one or more diametric expansion
elements are
removed from the sacrificial tip and move downward relative to the compaction
apparatus so as to hang from a bottom portion of the compaction apparatus. The
method
may, in some embodiments, create a well compacted column of densified soil
below and
around the one or more diametric expansion elements.
Certain other embodiments of methods of densifying and compacting granular
materials include the steps of (a) providing a compaction apparatus comprising
a drive
shaft, a compaction chamber at a lower end of the drive shaft, and one or more
diametric
expansion elements, wherein the apparatus further comprises an opening in an
upper
surface of the compaction chamber comprising a flow-through passage exterior
of the
.. drive shaft and configured for accepting granular materials from outside of
the drive
shaft, (b) driving the compaction apparatus into free-field soils to a
specified depth, (c)
lifting the compaction apparatus a specified distance such that the one or
more diametric
restriction elements move downward relative to the compaction apparatus to
hang from
connections to the compaction apparatus thereby allowing granular materials
located
.. above a top portion of the compaction chamber to flow through the flow-
through passage,
(d) re-driving the apparatus downwardly into the free-field soils causing the
one or more
diametric restriction elements to bunch-up forming compaction surfaces, and
(e) repeating the driving and lifting of the compaction apparatus. Moreover,
other
methods of densifying and compacting granular materials may include the steps
of
(a) providing a compaction apparatus comprising a drive shaft, a compaction
chamber,
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and one or more diametric restriction elements, wherein the compaction chamber
comprises a pipe and the drive shaft is fitted into one end of the pipe, (b)
driving the
compaction apparatus into free-field soils to a specified depth, (c) lifting
the compaction
apparatus a specified distance such that the one or more diametric restriction
elements
move downward relative to the compaction apparatus to hang from connections to
the
compaction apparatus thereby allowing granular materials located above a top
portion of
the compaction chamber to flow around the outside of the drive shaft and into
the
compaction chamber, (c) re-driving the apparatus downwardly into the free-
field soils
causing the one or more diametric restriction elements to bunch-up forming
compaction
surfaces; and (d) repeating the driving and lifting of the compaction
apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
Having thus described the presently disclosed subject matter in general terms,
reference will now be made to the accompanying Drawings, which are not
necessarily
drawn to scale, and wherein:
FIG. lA and FIG. 1B illustrate side views of an example of the presently
disclosed soil compaction apparatus in the raised and lowered positions,
respectively, and
comprising an arrangement of diametric expansion elements;
FIG. 2 illustrates a side view of the soil compaction apparatus of FIG. lA and
FIG. 1B and further comprising a sacrificial tip;
FIG. 3A and FIG. 3B illustrate a side view and a plan view, respectively, of
yet
another example of the presently disclosed soil compaction apparatus
comprising yet
another arrangement of diametric expansion/restriction elements;
FIG. 4A and FIG. 4B illustrate a side view and a plan view, respectively, of
yet
another example of the presently disclosed soil compaction apparatus
comprising another
arrangement of diametric restriction elements;
FIG. 5 illustrates a side view of the soil compaction apparatus of FIG. 4A and
FIG. 4B wherein the apparatus is used to compact granular materials within a
preformed
cavity;
FIG. 6 illustrates a side view of another example of a soil compaction
apparatus
comprising a removable ring of diametric restriction elements;
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FIG. 7A and FIG. 7B illustrate a top view and a bottom view, respectively, of
the
soil compaction apparatus of FIG. 6;
FIG. 8A illustrates a side view of a soil compaction apparatus comprising the
diametric restriction elements, according to yet another embodiment;
FIG. 8B and FIG. 8C illustrate a top view and a bottom view, respectively, of
the
soil compaction apparatus of FIG. 8A;
FIG. 9A illustrates a side view of a soil compaction apparatus comprising
diametric restriction elements, according to yet another embodiment;
FIG. 9B and FIG. 9C illustrate a top view and a bottom view, respectively, of
the
soil compaction apparatus of FIG. 9A;
FIG. 10 shows a plot of the modulus load test for a 16-inch (40.6 cm) mandrel
substantially similar to the mandrel of FIG. 6, FIG. 7A, and FIG. 7B in an
EXAMPLE I;
FIG. 11 shows a plot of the modulus load test results for a 28-inch (71.1 cm)
mandrel substantially similar to the mandrel of FIGS. 8A-8C in an EXAMPLE II;
FIG.12A and FIG. 12B illustrate side views of a soil compaction apparatus of a
further embodiment in the raised and lowered positions, respectively, and
comprising an
arrangement of separate diametric restriction and expansion elements;
FIG.13A and FIG. 13B show illustrations of the raised and lowered positions of
the apparatus described with reference to FIG. 12A and FIG. 12B, respectively;
FIG. 14A and FIG. 14B illustrate side views of an example of the presently
disclosed soil compaction apparatus in the raised and lowered positions,
respectively, and
comprising an arrangement of diametric expansion elements and a feed tube with
an
internal flow passage;
FIG. 15A and FIG. 15B illustrate side views of an example of the presently
disclosed soil compaction apparatus in the raised and lowered positions,
respectively, and
comprising an arrangement of diametric expansion elements and a closed-end
drive shaft;
FIG. 16A and FIG. 16B illustrate a side view and a top view, respectively, of
a
soil compaction apparatus of a further embodiment comprising one or more
interior air
injection tubes for increasing interior aggregate flow;
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FIG. 17A and FIG. 17B illustrate a side view and a top view, respectively, of
a
soil compaction apparatus of a further embodiment comprising one or more
exterior air
injection tubes for increasing exterior aggregate flow; and
FIG 18 shows a plot of the cone penetration resistance versus depth measured
down the center of two piers where one pier was installed using the present
invention
with air injection tubes similar to the mandrel in FIG 17A and FIG. 17B and
the other
pier was installed using the soil compaction apparatus without air injection
tubes.
DETAILED DESCRIPTION
The presently disclosed subject matter now will be described more fully
hereinafter with reference to the accompanying Drawings, in which some, but
not all
embodiments of the presently disclosed subject matter are shown. Like numbers
refer to
like elements throughout. The presently disclosed subject matter may be
embodied in
many different forms and should not be construed as limited to the embodiments
set forth
herein; rather, these embodiments are provided so that this disclosure will
satisfy
applicable legal requirements. Indeed, many modifications and other
embodiments of the
presently disclosed subject matter set forth herein will come to mind to one
skilled in the
art to which the presently disclosed subject matter pertains having the
benefit of the
teachings presented in the foregoing descriptions and the associated Drawings.
Therefore, it is to be understood that the presently disclosed subject matter
is not to be
limited to the specific embodiments disclosed and that modifications and other
embodiments are intended to be included within the scope of the appended
claims.
In some embodiments, the presently disclosed subject matter provides methods
and apparatuses for compacting soil and granular materials that are either
naturally
deposited or consist of man-placed fill materials for the subsequent support
of structures,
such as buildings, foundations, floor slabs, walls, embankments, pavements,
and other
improvements. Namely, the presently disclosed subject matter provides various
embodiments of soil compaction apparatuses in which each soil compaction
apparatus
includes an arrangement of diametric expansion/restriction elements. The
diametric
expansion/restriction elements can be fabricated from, for example, individual
chains,
cables, or wire rope, or a lattice of vertically and horizontally connected
chains, cables, or
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wire rope. In a specific example, the diametric expansion/restriction elements
can be
formed of half-inch, grade 100 alloy chains.
Embodiments of the soil compaction apparatus include, but are not limited to,
closed-ended driving shafts, open-ended driving shafts, flow-through passages,
no flow-
through passages. removable rings for holding the diametric
expansion/restriction
elements, and any combinations thereof.
In an example method of using the presently disclosed soil compaction
apparatus,
after initial driving, the soil compaction apparatus is raised and the
diametric expansion
elements hang freely by gravity from the bottom of the driving shaft. As the
driving shaft
is raised the free-field soils flow into the cavity left by the driving shaft.
After raising the
driving shaft the prescribed distance, the driving shaft is then re-driven
downwardly to a
depth preferably less than the initial driving depth into the underlying
materials. This
allows the diametric expansion elements the opportunity to expand radially,
forming a
compaction surface that has a diameter larger than the driving shaft. This
process creates
a well compacted column of densified soil below and around the diametric
expansion
elements. This process of lifting the driving shaft upward and driving back
down is
repeated incrementally until the driving shaft has been lifted to or near an
original ground
elevation.
Referring now to FIG. lA and FIG. 1B, a soil compaction apparatus 100
according to one embodiment is illustrated, wherein the soil compaction
apparatus 100 is
used to compact granular materials. Namely, FIG. 1A and FIG. 1B are side views
of the
presently disclosed soil compaction apparatus 100 in the raised and lowered
positions,
respectively, and comprising an arrangement of diametric expansion elements
114. The
soil compaction apparatus 100 shown in FIG. lA and FIG. 1B may be inserted or
driven
into free-field soils (i.e., soil that exists in its natural or placed state
below grade). The
soil compaction apparatus 100 comprises a driving shaft 110. In this example,
the
driving shaft 110 is a closed-top and closed-end driving shaft. Namely, a base
plate 112
is provided at the end of the driving shaft 110 that is driven into the soil,
thereby forming
the closed-end or closed-bottom driving shaft.
Further, an arrangement of diametric expansion elements 114 are attached to
the
bottom of the driving shaft 110 via, for example, a mounting plate 116. For
example, the
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diametric expansion elements 114 can be fastened to the mounting plate 116.
Then, the
mounting plate 116 can be bolted to the base plate 112. In this example, the
diametric
expansion elements 114 are located at the closed bottom of the driving shaft
110 that is
used to compact granular materials.
The diametric expansion elements 114 can be fabricated from individual chains,
cables, wire rope, or the like, or a lattice of vertically and horizontally
connected chains,
cables, wire rope, or the like. In a specific example, the diametric expansion
elements
114 are half-inch, grade 100 alloy chains. In the embodiment shown in FIG. lA
and FIG.
1B, when the soil compaction apparatus 100 is initially driven downward into
free-field
soil, the diametric expansion elements 114 may be placed within a sacrificial
tip 118, as
shown in FIG. 2. The sacrificial tip 118 may have a depth enough, such as 6
inches (15.2
cm), to house the diametric expansion elements 114.
After initial driving (see FIG. 1B), the soil compaction apparatus 100 is
raised and
the diametric expansion elements 114 hang freely by gravity from the bottom of
the
driving shaft 110 (see FIG. 1A). As the driving shaft 110 is raised the free-
field soils (or
additionally added aggregate) flow into the cavity left by the driving shaft
110.
Optionally, one or more wings 120 are attached to the outer sides of the
driving shaft 110.
The wings 120 can act to loosen the free-field soils around the driving shaft
110.
After raising the driving shaft 110 the prescribed distance, the driving shaft
110 is
then re-driven downwardly to a depth preferably less than the initial driving
depth into
the underlying materials. This allows the diametric expansion elements 114 the
opportunity to expand radially (see FIG. 1B) forming a compaction surface CS
that has a
diameter larger than the base plate 112. In one example, the diameter Dil of
the driving
shaft 110 and base plate 112 is about 12 inches (30.5 cm), while the diameter
Di2 of the
expanded compaction surface is about 18 inches (45.7 cm). The process creates
a well-
compacted column of densified soil below and around the diametric expansion
elements
114. This process of lifting the driving shaft 110 upward and driving back
down is
repeated incrementally until the driving shaft 110 has been lifted to or near
an original
ground elevation.
The diametric expansion elements 114 are configured and sized accordingly to
achieve the desired lift thickness, compaction surface area, and soil flow
based on the
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material type and project requirements. The base plate 112 and the diametric
expansion
elements 114 (with mounting plate 116) are typically changeable. The
configuration of
the changeable base plate 112 with the attached diametric expansion elements
114 can be
adapted to project requirements, which eliminates having to make separate
drive shaft
mandrels and is therefore a low cost and effective method. The soil compaction
apparatus 100 shown in FIG. lA and FIG. 1B has the advantage of being simple
to
fabricate, construct, and maintain.
Referring now to FIG. 3A and FIG. 3B, a side view and a plan view,
respectively,
of yet another example of the presently disclosed soil compaction apparatus
100 is
illustrated comprising yet another arrangement of diametric
expansion/restriction
elements 114. In this example, a flow-through passage 122 around the driving
shaft 110
and within a compaction chamber 124 facilitates aggregate flow into the
compaction
chamber 124 from an exterior of the driving shaft 110. In one example, the
driving shaft
110 is an I-beam or H-beam that provides the "flow-through" arrangement,
wherein soil
can flow through the driving shaft 110 and into the flow-through passages 122
of the I-
beam or H-beam (and compaction chamber 124). In the case of an H-beam being
used as
the driving shaft 110. the outer two flanges on the H-beam can also help case
the soil
cavity walls while the mandrel is being lowered and raised in the cavity. It
is also
contemplated that the driving shaft 110 can be a solid cylindrical shaft (with
struts or
similar connections to the compaction chamber) or the like.
The soil compaction apparatus 100 shown in FIG. 3A and FIG. 3B further
comprises a compaction chamber 124. Namely, the compaction chamber 124 is
mechanically connected to the bottom end of the driving shaft 110. The
compaction
chamber 124 is, for example, cylinder-shaped. The compaction chamber 124 may
be the
same size or diameter as the driving shaft 110 or the compaction chamber 124
may be
larger or smaller than the driving shaft 110. In FIG. 3A and FIG. 3B, the
compaction
chamber 124 is larger in cross-sectional area than the driving shaft 110. In
one example.
the length of the compaction chamber 124 is about 24 inches (61.0 cm).
The compaction chamber 124 may be connected to the driving shaft 110 with a
load transfer plate 126 with the optional use of one or more stiffener plates
128. The
compaction chamber 124 may be open at its lower surface allowing for the
intrusion of
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granular materials into the compaction chamber 124 when the soil compaction
apparatus
100 is driven downwards. In the embodiment shown in FIG. 3A and FIG. 3B, the
compaction chamber 124 may also be generally open at its upper surface
facilitating the
flow-through passage(s) 122. Namely, the load transfer plate 126 can be a ring-
shape
plate with an opening in the center portion thereof.
Further, in the embodiment shown in FIG. 3A and FIG. 3B, both interior
diametric restriction elements 1141 and exterior diametric expansion elements
114E are
attached to the load transfer plate 126. In this example, interior diametric
"restriction"
elements 1141 means interior to the compaction chamber 124 and exterior
diametric
"expansion" elements 114E means exterior to the compaction chamber 124. The
interior
diametric restriction elements 1141 and exterior diametric expansion elements
114E may
or may not be connected to one another. The diametric expansion/restriction
elements
114 (generally including interior diametric restriction elements 1141 and
exterior
diametric expansion elements 114E) typically may consist of individual chain
links,
cable, or of wire rope or a lattice of connected elements that hang downward
from the
load transfer plate 126. In a specific example, the diametric
expansion/restriction
elements 114 are half-inch, grade 100 alloy chains.
In the embodiment shown in FIG. 3A and FIG. 3B, the soil compaction apparatus
100 can be used to compact and densify granular soils in the free field or
within a
predrilled cavity. When the soil compaction apparatus 100 is extracted upwards
through
the free field soil or within a preformed cavity, the diametric
expansion/restriction
elements 114 hang vertically downward and offer little resistance to the
upward
movement of the soil compaction apparatus 100. When the soil compaction
apparatus
100 is driven downward, the diametric expansion/restriction elements 114
engage the
materials that the soil compaction apparatus 100 is being driven into because
these
materials (i.e., free field soil or aggregate placed in a predrilled hole) are
moving upwards
relative to the downwardly driven soil compaction apparatus 100.
The engaged materials cause the diametric expansion/restriction elements 114
to
"expand" or "bunch" together, thereby substantially inhibiting any further
upward
movement of the soil or aggregate materials. The interior diametric
restriction elements
1141 thus "bunch" in the interior of the compaction chamber 124 causing the
compaction
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chamber 124 to "plug" with the upwardly moving soil material during downward
movements of the mandrel. This creates an effective compaction surface CS that
is then
used to compact the materials directly below the bottom of the soil compaction
apparatus
100. The exterior diametric expansion elements 114E likewise "expand" exterior
of the
compaction chamber 124 thus inhibiting the upward movement of the soil or
aggregate
materials exterior to the compaction chamber. This mechanism thus effectively
increases
the cross-sectional area of the compaction surface CS during downward
compaction
strokes. The increase in cross-sectional area allows for the use of the soil
compaction
apparatus 100 with an effective cross-sectional area that is larger during
compaction than
during extraction, offering great efficiency and machinery and tooling cost
savings during
construction.
Referring now to FIG. 4A and FIG. 4B, a side view and a plan view,
respectively,
are illustrated of yet another example of the presently disclosed soil
compaction
apparatus 100 comprising yet another arrangement of diametric restriction
elements 114.
The soil compaction apparatus 100 shown in FIG. 4A and FIG. 4B is
substantially the
same as the soil compaction apparatus 100 shown in FIG. 3A and FIG. 3B, except
that it
does not include the exterior diametric expansion elements 114E. In this
example, the
load transfer plate 126 does not extend beyond the diameter of the compaction
chamber
124 and only the interior diametric restriction elements 1141 are attached
thereto. Both of
the soil compaction apparatuses 100 shown in FIG. 3A, FIG. 3B, FIG. 4A, and
FIG. 4B
provide an efficient flow-through passage 122 in an arrangement exterior of
the driving
shaft 110 that allows for improved granular material flow into the compaction
chamber
124.
In the soil compaction apparatus 100 shown in FIG. 4A and FIG. 4B, when the
soil compaction apparatus 100 is raised, granular materials that are located
above the top
of the compaction chamber 124 may flow around the outside of the compaction
chamber
124 and/or through or exterior of the driving shaft 110 and into flow-through
passage 122
to enter the compaction chamber 124 from above. The ability of the granular
materials to
flow through the flow-through passage 122 allows the soil compaction apparatus
100 to
.. be raised upwards with less extraction force and thus with greater
efficiency (as opposed
to a more generally "closed" upper portion of the compaction chamber as seen
in the
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prior art). After the soil compaction apparatus 100 is raised, it is then re-
driven back
downwards. The downward action allows the interior diametric restriction
elements 1141
to "bunch" together thereby forming an effective plug that is then used to
compact the
materials below the bottom of the soil compaction apparatus 100.
The soil compaction apparatus 100 shown in FIG. 4A and FIG. 4B is especially
effective at densifying and compacting aggregates within preformed cavities.
By way of
example, FIG. 5 shows the soil compaction apparatus 100 shown in FIG. 4A and
FIG. 4B
in a cavity 130, wherein the soil compaction apparatus 100 is used to compact
granular
materials within a preformed cavity. In this example, the soil compaction
apparatus
compaction chamber 124 has a height H of approximately 24 inches (61.0 cm).
In an exemplary method, the cavity 130 is formed by drilling or other means
and
the soil compaction apparatus 100 is lowered into the cavity 130. Aggregate
may then be
poured from the ground surface to form a mound on top of the compaction
chamber 124
within the cavity 130. When the soil compaction apparatus 100 is raised, the
aggregate
may then flow through and around the flow-through passage 122 and into the
interior of
the compaction chamber 124. Further raising the soil compaction apparatus 100
allows
aggregate to flow below the bottom of the compaction chamber 124. When the
soil
compaction apparatus 100 is driven downwards into the placed aggregate, the
interior
diametric restriction elements 1141 move inwardly to "bunch" together to form
a
compaction surface. This mechanism facilitates the compaction of the aggregate
materials below the compaction chamber 124. The soil compaction apparatus 100
and
method described above for this embodiment allows the soil compaction
apparatus 100 to
remain in the cavity 130 during the upward and downward movements required for
the
compaction cycle and eliminates the need to "trip" the mandrel out of the
cavity 130 as is
required for previous art. The soil compaction apparatus 100 and method
further
eliminate the need for a hollow feed tube and hopper that is typically
required for
displacement methods used in the field and described above. Another advantage
of the
open flow-through passage 122 in the upper portion of the compaction chamber
124 is
the ability to develop a head of stone above the compaction chamber to
temporarily case
the caving cavity soils during pier construction, while being able to leave
the mandrel in
the cavity while aggregate is added.
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The soil compaction apparatuses 100 shown in FIG. lA through FIG. 3B may
also be used in conjunction with the method for compacting and densifying
aggregate in
predrilled holes as described above in FIG. 4A, FIG. 4B, and FIG. 5. When the
soil
compaction apparatuses 100 shown in FIG. lA through FIG. 3B are used, the
exterior
diametric expansion elements 114 hang downwards during upward extraction and
expand/bunch together during the downward compaction stroke. This prevents the
aggregate below from moving upwards relative to the exterior of the driving
shaft 110
and/or the compaction chamber 124. The prevention of upward movements allows a
tamper head to effectively enlarge during the compaction of the aggregate. A
larger sized
tamper head provides greater confinement to the lift of aggregate placed and
effectively
densifies a greater depth of aggregate within the lift that is placed. This
mechanism
allows for the use of thicker lifts of aggregate during compaction, making the
process less
costly and more efficient.
Referring now to FIG. 6, a side view of another soil compaction apparatus 200
is
illustrated comprising a removable ring of diametric restriction elements
(defined in
further detail hereinbelow), according to another embodiment. FIG. 7A and FIG.
7B
illustrate a top view and a bottom view, respectively, of the soil compaction
apparatus
200 of FIG. 6.
The soil compaction apparatus 200 includes a driving shaft 210. The driving
shaft
210 is typically an I-beam or H-beam that provides a "flow-through"
arrangement,
wherein soil/aggregate can flow through or exterior of the driving shaft 210
and into the
flow-through passages 122 of the I-beam or H-beam (see FIG. 7A and FIG. 7B).
In one
example, the I-beam or H-beam has a height of about 11.5 inches (29.2 cm), a
width of
about 10.375 inches (26.4 cm), and a length of about 112 inches (2.84 m). An
opening
212 may be provided in the web of the I-beam or H-beam that forms the driving
shaft 210
to allow aggregate or other materials in the cavity above the bottom end of
the drive shaft
to pass from one half of the cavity to the other. The opening 212 may be near
the bottom
end of the driving shaft 210. In one example, the opening 212 has rounded ends
and is
about 24 inches (61.0 cm) long and about 6 inches (15.2 cm) wide. To overcome
any
loss of strength in the driving shaft 210 due to the presence of the opening
212, a pair of
reinforcing plates 214 can be, for example, welded to the driving shaft 210,
i.e., one
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reinforcing plate 214 on one side and another reinforcing plate 214 on the
other side near
the opening 212. In one example, each reinforcing plate 214 is about 5 inches
(12.7 cm)
wide and about 1 inch (2.5 cm) thick.
In soil compaction apparatus 200, the bottom end of the driving shaft 210 is
fitted
into one end of a pipe 216 such that a portion of the opening 212 is inside
the pipe 216.
Namely, the driving shaft 210 is fitted into the pipe 216 to a depth dl. In
one example,
the depth dl is about 11 inches (27.9 cm). Once fitted into the pipe 216, the
driving shaft
210 can be secured therein by, for example, welding. In one example, the pipe
216 has a
length Li of about 36 inches (91.4 cm), an outside diameter (OD) of about 16
inches
(40.6 cm), an inside diameter (ID) of about 14 inches (35.6 cm), and thus a
wall thickness
of about 1 inch (2.5 cm).
Fitted around the bottom end of the pipe 216 can be a reinforcing ring 218. In
one
example, the reinforcing ring 218 has a height hl of about 3 inches (7.6 cm),
an OD of
about 18 inches (45.7 cm), an ID of about 16 inches (40.6 cm), and thus a wall
thickness
of about 1 inch (2.5 cm). In one example, the reinforcing ring 218 can be
secured to the
pipe 216 by welding. Further, a ring-shaped wearing pad 220 can abut the end
of the
pipe 216 and the reinforcing ring 218. In one example, the wearing pad 220 has
a
thickness ti of about 1 inch (2.5 cm). The wearing pad 220 may be replaced as
needed.
The soil compaction apparatus 200 also typically comprises a removable ring
222
to which an arrangement of the diametric restriction elements 114 is attached.
In one
example, the removable ring 222 has a height of from about 3 inches (7.6 cm)
to about 4
inches (10.2 cm), an OD of about 14 inches (35.6 cm), an ID of about 13 inches
(33.0
cm), and thus a wall thickness of about 0.5 inches (1.3 cm). By attaching the
diametric
restriction elements 114 to the removable ring 222, a removable ring of the
diametric
restriction elements 114 is formed. The removable ring 222 with the diametric
restriction
elements 114 may be fitted inside of the pipe 216 and positioned near the end
of the
driving shaft 210 such that the diametric restriction elements 114 hang down
toward the
bottom end of the pipe 216. The removable ring 222 can be secured inside the
pipe 216
by, for example, bolts 224.
Another set of diametric restriction elements 114 can be secured to the web of
the
I-beam or H-beam that forms the driving shaft 210. Hereafter, the diametric
restriction
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elements 114 attached to the removable ring 222 are called the diametric
restriction
elements 114A. Hereafter, the diametric restriction elements 114 attached to
the web of
the driving shaft 210 are called the diametric restriction elements 114B.
In one example, the removable ring 222 can be a single-piece continuous ring.
In
this example, the diametric restriction elements 114A are formed, for example,
by
welding twenty-six (26), 14-inch (35.6 cm) long, half-inch (1.3 cm), grade 100
alloy
chains to the removable ring 222. In another example, the removable ring 222
can
consist of two half-rings that are positioned together inside of the pipe 216.
In this
example, the diametric restriction elements 114A are formed, for example, by
welding
thirteen (13), 14-inch (35.6 cm) long, half-inch (1.3 cm), grade 100 alloy
chains to each
half of the removable ring 222.
In one example, the diametric restriction elements 114B attached to the web of
driving shaft 210 are formed by welding five (5), 14-inch (35.6 cm) long, half-
inch (1.3
cm), grade 100 alloy chains to the web of the I-beam or H-beam that forms the
driving
shaft 210. When the mandrel is driven into the aggregate, the chains bunch-up,
thereby
substantially restricting the flow of aggregate upward and allowing the
mandrel to
compact the aggregate. When the mandrel is extracted, the chains fall,
allowing
aggregate to flow downward relative to the mandrel.
Referring now to FIG. 8A, a side view of a soil compaction apparatus 300 is
illustrated comprising the diametric restriction elements 114, according to
another
embodiment. FIG. 8B and FIG. 8C illustrate a top view and a bottom view,
respectively,
of the soil compaction apparatus 300 of FIG. 8A. In this example, the soil
compaction
apparatus 300 can comprise a pipe 310. The bottom end of the pipe 310 may be
closed
using a plate or cap 312, thereby rendering the pipe 310 a closed-end pipe.
The top end
of the pipe 310 typically has a flange 314 for connecting to the tip of the
driving shaft
110. In one example, the pipe 310 is about 40 inches (101.6 cm) long and has
an OD of
about 10 inches (25.4 cm), an ID of about 8 inches (20.3 cm), and thus a wall
thickness of
about 1 inch (2.5 cm). The pipe 310, the plate or cap 312, and the flange 314
can be
fastened together by, for example, welding.
The bottom end of the closed-end pipe 310 is fitted into one end of a
compaction
chamber 318. In one example, the compaction chamber 318 is a pipe that has a
length Li
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of about 40 inches (101.6 cm), an OD of about 33.5 inches (85.1 cm), an ID of
about 31.5
inches (80.0 cm), and thus a wall thickness of about 1 inch (2.5 cm). In one
example, the
pipe 310 is fitted into the compaction chamber 318 a distance of about 21
inches (53.3
cm).
The pipe 310 may be supported within the compaction chamber 318 by, for
example, four struts or plates 320 arranged radially around the pipe 310
(e.g., one at 12
o'clock, one at 3 o'clock, one at 6 o'clock, and one at 9 o'clock). In one
example, the
struts or plates 320 are about 1 inch (2.5 cm) thick. The struts or plates 320
typically
extend into the compaction chamber 318 a distance dl, or for example, about 19
inches
(48.3 cm). The top end of the struts or plates 320 can be tapered toward the
pipe 310 as
shown, whereas the lower ends of the struts or plates 320 are typically
squared off.
Alternatively, the struts or plates 320 may be squared off at the top similar
to the lower
end. The plate or cap 312 at the end of the pipe 310 may extend slightly below
the lower
end of the struts or plates 320. The pipe 310, the compaction chamber 318, and
the struts
or plates 320 can be fastened together by. for example, welding.
Further, a ring 322 may be provided inside of the compaction chamber 318 and
near the lower end of the struts or plates 320. In one example, the ring 322
has a height
of about 2 inches (5.1 cm), an OD of about 31.5 inches (80.0 cm), an ID of
about 29.5
inches (74.9 cm), and thus a wall thickness of about 1 inch (2.5 cm). The ring
322 can be
fastened inside of the compaction chamber 318 by, for example, welding or
bolting.
As shown in FIG. 8C, the diametric restriction elements 114 may be attached to
and hang down from the lower surface of the ring 322, the lower edges of the
four struts
or plates 320, and around the perimeter of the plate or cap 312. The diametric
restriction
elements 114 can be fabricated from individual chains, cables, or wire rope,
or a lattice of
vertically and horizontally connected chains, cables, or wire rope. In a
specific example,
the diametric restriction elements 114 are 19-inches (48.3 cm) long, half-inch
(1.3 cm),
grade 100 alloy chains that are welded to the ring 322, the struts or plates
320, and the
plate or cap 312.
Referring now to FIG. 9A, a side view of a soil compaction apparatus 400 is
illustrated comprising the diametric restriction elements 114, according to
another
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embodiment. FIG. 9B and FIG. 9C illustrate a top view and a bottom view,
respectively,
of the soil compaction apparatus 400 of FIG. 9A.
In this example, the soil compaction apparatus 400 typically comprises a drive
pipe 410. The bottom end of the drive pipe 410 may be closed using a plate or
cap 412,
thereby rendering the drive pipe 410 a closed-end pipe. The top end of the
drive pipe 410
typically has a flange 414 for connecting to the tip of the driving shaft 110.
In one
example, the drive pipe 410 is about 40 inches (101.6 cm) long and has an OD
of about 7
inches (17.8 cm), an ID of about 5 inches (12.7 cm), and thus a wall thickness
of about 1
inch (2.5 cm). The drive pipe 410, the plate or cap 412, and the flange 414
can be
fastened together by, for example, welding.
The bottom end of the closed-end drive pipe 410 is fitted into one end of a
compaction chamber 418. In one example, the compaction chamber 418 is a pipe
that
has a length Li of about 40 inches (101.6 cm), an OD of about 27 inches (68.6
cm), an
ID of about 25 inches (63.5 cm), and thus a wall thickness of about 1 inch
(2.5 cm). In
one example, the drive pipe 410 is extended into the compaction chamber 418 a
distance
of about 26 inches (66.0 cm).
The drive pipe 410 may be supported within the compaction chamber 418 by, for
example, three struts or plates 420 arranged radially around the drive pipe
410 (e.g., one
at 12 o'clock, one at 4 o'clock, and one at 8 o'clock). In one example, the
struts or plates
420 are about 1 inch (2.5 cm) thick. The struts or plates 420 can extend into
the
compaction chamber 418 a distance dl, or for example, about 24 inches (61.0
cm). The
top end of the struts or plates 420 can be squared off at about the top edge
of the drive
pipe 410 as shown. The lower end of the struts or plates 420 can be also be
squared off.
The plate or cap 412 at the end of the drive pipe 410 may extend slightly
below the lower
end of the struts or plates 420. The drive pipe 410, the compaction chamber
418, and the
struts or plates 420 can be fastened together by, for example, welding.
Further, a ring 422 may be provided inside of the compaction chamber 418 and
near the lower end of the struts or plates 420. In one example, the ring 422
has a height
of about 2 inches (5.1 cm), an OD of about 25 inches (63.5 cm), an ID of about
23 inches
(58.4 cm), and thus a wall thickness of about 1 inch (2.5 cm). The ring 422
can be
fastened inside of the compaction chamber 418 by, for example, welding or
bolting.
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The diametric restriction elements 114 are typically attached to and hang down
from the lower surface of the ring 422, around the perimeter of the plate or
cap 412, and
from the bottom of the struts 420. The diametric restriction elements 114 can
be
fabricated from individual chains, cables, or wire rope, or a lattice of
vertically and
horizontally connected chains, cables, or wire rope. In one example, there are
thirty two
(32), 14-inch (35.6 cm) long, half-inch (1.3 cm), grade 100 alloy chains
welded to the
ring 422 and fourteen (14), 20-inch (50.8 cm) long, half-inch (1.3 cm), grade
100 alloy
chains welded to the plate or cap 412.
Exterior Ring Embodiment with Exterior and Internal Elements
Referring now to FIG. 12A and FIG. 12B, side views of the raised and lowered
positions, respectively, of yet another example of the presently disclosed
soil compaction
apparatus 100 is illustrated comprising yet another arrangement of separate
interior and
exterior diametric restriction/expansion elements 1141 and 114E, respectively.
The soil
compaction apparatus 100 shown in FIG. 12A and FIG. 12B is substantially the
same as
the soil compaction apparatus 100 shown in FIG. 3A and FIG. 3B, except that
the
exterior diametric expansion elements 114E are not connected to the interior
diametric
restriction elements 1141. In this example, the exterior diametric expansion
elements are
mechanically fastened to the load transfer plate 126 that extends beyond the
diameter of
the compaction chamber 124 and attached to an exterior floating
circumferential ring 140
that is free to translate in the vertical, up and down direction yet is
constrained in the
lateral, side-to-side direction.
In the soil compaction apparatus 100 shown in FIG. 12A and FIG. 12B, when the
soil compaction apparatus 100 is raised, granular materials that are located
above the top
of the compaction chamber 124 may flow around the outside of the exterior
diametric
expansion elements 114E and/or through or exterior of the driving shaft 110
and into
flow-through passage 122 to enter the compaction chamber 124 from above. The
ability
of the granular materials to flow through the flow-through passage 122 allows
the soil
compaction apparatus 100 to be raised upwards with less extraction force and
thus with
greater efficiency (as opposed to a more generally "closed" upper portion of
the
compaction chamber as seen in the prior art). After the soil compaction
apparatus 100 is
raised, it is then re-driven back downwards. The downward action allows the
exterior
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floating ring 140 to translate up the outside of the compaction chamber 124
and further,
allowing the diametric expansion elements to expand outwards thereby
increasing the
compaction diameter below the bottom of the apparatus 100.
The soil compaction apparatus 100 described in FIG. 12A and FIG. 12B is
further
illustrated in FIG. 13A and FIG. 13B. The raised position of the apparatus 100
is pictured
in FIG. 13A. The increased compaction diameter achieved by the apparatus 100
in the
lowered position is shown in FIG. 13B. In this example, there are twenty (20),
18-inch
(45.7cm) long, half-inch (1.3cm), grade 100 alloy chains welded approximately
4 inches
(10.2cm) below the top of the compaction chamber 124 and connected by the
exterior
floating ring 140 hanging approximately 2 inches (5.1 cm) above the bottom of
the soil
compaction apparatus 100. In this example, the soil compaction apparatus has
an exterior
diameter in the raised position Dil of 15 inches (38.1cm) and an exterior
diameter in the
lowered position Di2 of about 20 inches (50.8cm).
Exterior Only Embodiment
Referring now to FIG. 14A and FIG. 14B, side views of the raised and lowered
positions, respectively, of yet another example of the presently disclosed
soil compaction
apparatus 100 is illustrated comprising yet another arrangement of exterior
diametric
expansion elements 114E. The soil compaction apparatus 100 shown in FIG. 14A
and
FIG. 14B can be substantially the same as the soil compaction apparatus 100
shown in
FIG. 12A and FIG. 12B, except that the mandrel is designed such that only
exterior
diametric expansion elements 114E are present and are mechanically fasted to
the drive
shaft 110 in a different manner, such as attachment at a notch point N. Notch
point N can
consist of a notch formed between different wall thicknesses in the drive
shaft, for
example a first wall thickness formed in an upper portion of drive shaft 110
to form a
first diameter Dil and a second wall thickness formed in a lower portion of
drive shaft
110 to form a second diameter Di2. A similar exterior floating circumferential
ring 140
can be used at the terminal end of the exterior diametric expansion elements
114E and is
free to translate in the vertical, up and down direction yet is constrained in
the lateral,
side-to-side direction. FIG. 14A and FIG. 14B depict use with a feed tube
having an
internal flow passage 122, whereas FIG. 15A and FIG. 15B depict use with a
closed-end
drive shaft but with a similar arrangement of exterior diametric expansion
elements 114E.
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Air Enhanced Embodiment
Referring now to FIG. 16A and FIG. 16B, a side view and a plan view,
respectively, are illustrated of yet another example of the presently
disclosed soil
compaction apparatus 100, comprising at least one interior air injection tube
150 with at
least one injection port 152 used to supply positive air pressure required to
increase
interior aggregate flow down the flow-through passage(s) 122.
In this example, the air injection tubes 150 are fastened to the inside
flanges of the
drive shaft 110 with multiple discharge ports 152 located above the compaction
chamber
124. The air injection ports 152 may be directed towards the center of the
drive shaft 110
or downwards along the drive shaft 110 to contain the flow of air pressure
within the
interior of the drive shaft 110. The supply of positive air pressure focused
to the interior
of the drive shaft 110 is useful to facilitate the flow of aggregate down
through the flow-
through passage(s) 122 to enter the compaction chamber 124 from above by
reducing any
aggregate bridging that may occur between the interior flanges of the drive
shaft 110 and
the side walls of preformed or displaced soil cavity. In one example, the air
injection
tube 150 has a nominal diameter of 0.75 inches (1.9cm) with multiple air
injection ports
152 of about 0.125 inches (3.18mm) in diameter located more than 1 inch (2.54
cm)
above the compaction chamber 124 and spaced approximately 3 feet (0.9 m)
center-to-
center along the length of the drive shaft 110.
A further embodiment of the presently disclosed soil compaction apparatus 100
is
illustrated in a side view and a plan view in FIG. 17A and FIG. 17B,
respectively. The
soil compaction apparatus 100 shown in FIG. 17A and FIG. 17B is substantially
the same
as the soil compaction apparatus 100 shown in FIG. 16A and FIG. 16B, except
that the
air injection tubes 150 are located on the exterior flange of the drive shaft
110 and the
injection ports 152 are directed outwards away from the drive shaft 110 to
increase
exterior aggregate flow.
In this example, the four air injection tubes 150 are fastened to the outside
of the
drive shaft flanges with multiple discharge ports 152 located above the
compaction
chamber 124 and directed outwards towards the free field soil. The supply of
positive air
pressure focused to the exterior of the drive shaft 110 is useful to induce
caving of the
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granular free field soils into the cavity created by driving the soil
compaction apparatus
100 into the ground. When the soil compaction apparatus 100 is raised, the
caving
granular materials may flow around the outside of the compaction chamber or
between
the driving shaft 110 flanges and into flow-through passage 122 to enter the
compaction
chamber 124 from above. When the soil compaction apparatus 100 is re-driven
back
downwards, the caving granular free field soils may then be compacted in place
below
the bottom of the apparatus 100. The ability of the exterior free field
granular materials
to flow into the compaction chamber 124 increases the volume of aggregate that
can be
compacted below ground.
Having generally described the invention, various embodiments are more
specifically described by illustration in the following specific EXAMPLES,
which further
describe different embodiments of the soil compaction apparatus.
EXAMPLE I
In one example, a method of compacting aggregate using an embodiment of the
subject matter disclosed herein in a pre-drilled cavity was demonstrated in
full-scale field
tests. The compaction mandrel was comprised of an 1-beam" drive shaft with a
16-inch
(40.6 cm) diameter flow-through compaction chamber at the bottom, similar to
the soil
compaction apparatus 200 shown in FIGS. 6, 7A, and 7B.
Test piers with a diameter of 20-inches (50.8 cm) were installed to a depth of
30
feet (9.1 m). The piers were constructed by drilling a cylindrical cavity to
the specified
depth. After drilling, stone aggregate was poured into the cavity until there
was an
approximate 3-foot thick lift of uncompacted stone at the bottom of the
cavity. The
mandrel was then lowered into the cavity until it reached the top of the
stone. The
hammer was started and the mandrel was lowered into the stone until the
diametric
restrictor elements on the bottom were engaged. The mandrel was then driven
into the
stone, both compacting the stone and driving the stone downward and laterally
into the
surrounding soil.
While the mandrel was in the cavity and compacting the bottom lift of stone,
additional aggregate was poured into the cavity until the aggregate was
approximately 10
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feet (3.0 m) above the compaction head. The mandrel was then raised 6 feet
(1.8 m),
causing the diametric restrictor elements to unfurl and allowing the aggregate
to pass
through the compaction head (via the flow-through passages). The mandrel was
then
driven down into the aggregate 3 feet (0.9 m), causing the diametric
restrictor elements to
bind up and both compact the aggregate between the initial lift and compaction
head and
drive the aggregate laterally into the surrounding stone. The mandrel was then
subsequently raised 6 feet (1.8 m) and lowered 3 feet (0.9 m) compacting each
lift of
aggregate in 3-foot (0.9 m) increments, until reaching the ground surface. The
level of
stone was maintained above the top of the compaction head throughout
construction of
the pier.
Modulus tests were performed on two of the constructed piers, one for a pier
constructed to a depth of 30 feet (9.1 m) using clean, crushed stone and one
to a depth of
30 feet (9.1 m) with the bottom 10 feet (3.0 m) of compacted aggregate
consisting of
clean, crushed stone and the upper 20 feet (6.1 m) of compacted aggregate
consisting of
concrete sand. The results shown in plot 1000 of FIG. 10 indicate that the
constructed
piers confirmed the design and were sufficient to support the structure.
More than 5,000 piers were installed at this site with the technique described
above. Traditional replacement methods such as those described in U.S. Patent
Numbers
5,249,892 and 6,354,766 were not feasible at this site because the drilled
cavities were
unstable below a depth of 10 feet (3.0 m). The installation method described
herein
allowed for the head of stone above the compaction chamber to temporarily case
the
caving soils during pier construction. The advantage of being able to leave
the mandrel
in the cavity as aggregate was added allowed for an average installation rate
of
approximately 145 feet (44.2 m) of pier per hour, a rate estimated to be
approximately 30
percent faster than is typically observed for traditional replacement methods.
Further, the
present invention was advantageous over the displacement method described in
U.S.
Patent Number 7,226,246 because it allowed for higher capacities to develop in
the upper
cohesive soils relative to displacement methods.
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EXAMPLE II
In another example of an embodiment of the subject matter disclosed herein, a
method of compacting aggregate in a pre-drilled cavity with a mandrel having a
28-inch
(71.1 cm) diameter flow-through compaction chamber similar to FIGS. 8A-8C was
demonstrated in full scale field tests. A modulus test pier was constructed to
verify the
performance of the construction method.
The cavity for the test pier was drilled to a depth of 12 feet (3.7 m). After
drilling, the mandrel was lowered into the cavity until the compaction chamber
reached
the bottom. Clean stone aggregate was poured into the cavity until there was
enough
uncompacted stone to create a 2-foot (0.6 m) thick compacted lift. The mandrel
was
raised 3 feet (0.9 m) and lowered 3 feet (0.9 m) to drive the stone into the
underlying soil.
The mandrel was then removed and a telltale assembly was placed into the
cavity, on top
of the initial compacted lift.
The mandrel was lowered back into the cavity and crushed stone aggregate was
poured into the cavity until it reached the ground surface. The mandrel was
raised 3 feet
(0.9 m), allowing the aggregate to pass through the compaction head (via the
flow-
through passage), and then driven down into the aggregate 1.5 feet (0.5 m),
causing the
diametric restrictor elements to bind up and both compact the aggregate and to
drive the
aggregate laterally into the surrounding soil. The mandrel was then
subsequently raised 3
feet (0.9 m) and lowered 1.5 feet (0.5 m) until reaching the ground surface.
The level of
stone was maintained above the compaction chamber throughout construction of
the pier.
The modulus test results are shown in plot 1100 of FIG. 11. The test was
conducted using a test set up and sequence used for a "quick pile load test"
described in
ASTM D1493. The test results show a plot of applied top of pier stress on the
x-axis and
top of pier deflection on the y-axis. The results indicate that the
constructed piers
confirmed the design and were sufficient to support the structure.
Several hundred piers were installed at this site with the technique described
above to depths of up to 40 feet (12.2 m). The advantage of being able to
leave the
mandrel in the cavity as aggregate was added allowed for an installation time
that is
faster than is typically observed for traditional replacement methods.
Further, the present
invention was advantageous over the displacement method described in U.S.
Patent
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Number 7,226,246 because it allowed for higher capacities to develop in the
upper
cohesive soils relative to displacement methods.
EXAMPLE III
In yet another example of an embodiment of the subject matter disclosed
herein, a
method of compacting aggregate in soil with a mandrel having a 15-inch (38.1
cm)
exterior diameter and flow-through compaction chamber similar to FIGS. 12 A ¨
13B
was demonstrated in full scale tests.
The mandrel was driven into the granular fill soil to a depth of approximately
10
feet (3.0 m). During the initial drive of the mandrel, it was observed that
the exterior
diametric expansion chains "bunched" up and outwards to form a widened
compaction
area such as that pictured in FIG. 13B. The diameter of cavity created by the
vertical
displacement of the mandrel and widened compaction area was measured to be
approximately 20 inches (50.8cm). With the mandrel at the bottom of the
cavity, clean
aggregate was poured into the cavity until it reached the ground surface. The
mandrel
was raised 3 feet (0.9m) to allowing the aggregate to pass through the
compaction
chamber (via the flow through passage) and through the annular space between
the
outside diameter of the mandrel in the raised position and the enlarged cavity
created by
the mandrel during the initial drive. The mandrel was then driven 2 feet
(0.6m) causing
the diametric expansion/restrictor elements to bind up and compact the
aggregate in the
widened area below the mandrel. The 3ft/2ft-up and down stroking pattern was
continued
until reaching the ground surface. The level of clean aggregate was maintained
above the
compaction chamber throughout construction of the pier.
The advantage of the increased compaction area created by the exterior
diametric
expansion elements (chains) allowed for more efficient aggregate flow by
creating an
enlarged cavity where the material could flow around the exterior diameter of
the
mandrel while being raised. This technique also increases the ability to use
finer
aggregates for backfill material in the cases where not having enough flow
through area
was a limiting factor.
EXAMPLE IV
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In still yet another example of an embodiment of the subject matter disclosed
herein, a method of compacting aggregate in soil with a mandrel having a 12-
inch
(30.5cm) diameter flow-through compaction chamber with exterior air injection
tubes to
increase aggregate flow similar to FIGS. 17A and 17B was demonstrated in full
scale
tests.
Several test piers were installed with a Liebherr 125 base machine equipped
with
an air compressor with a rated air volume flow rate of 185 cubic feet per
minute. An air
hose ran from the air compressor and connected to an air fitting mounted at
the top of the
mandrel. The air fitting ran into a splitter that tied together two steel 1
inch (2.5 cm)
nominal diameter air injection tubes that ran down the outside of the opposing
flanges on
the I-beam drive shaft. At approximately 3 feet above the compaction chamber,
the air
tubes split again a second time into two 0.75 inch (1.9 cm) nominal diameter
tubes that
ran down the outer edges of the drive shaft flanges making a total of four air
injection
tubes above the compaction chamber. Along each of the four air injection tubes
there
were three 0.125 inch (3.18mm) diameter injection ports spaced 1-ft center-to-
center for a
total of twelve injection ports. The injection ports were oriented parallel
with the flange
to direct the air pressure outwards to cut into the surrounding soil.
The test piers were constructed by driving the mandrel supplied with positive
air
pressure into the loose clean sand profile to a depth of approximately 20 feet
(6.1m).
Clean aggregate backfill was added to the cavity until it reached the ground
surface. The
mandrel was raised 4 feet (1.2m) allowing the aggregate backfill plus any
caving sand
from the surrounding soil (induced by the outward air pressure) to pass
through the
compaction chamber (via the flow through passage). The mandrel was then driven
3 feet
(0.9m) causing the diametric restrictor elements to bind up and compact the
aggregate
below the mandrel. The 4ft/3ft-up and down stroking pattern was continued
until
reaching the ground surface. The level of clean aggregate was maintained above
the
compaction chamber throughout construction of the pier. The air compressor was
turned
on and supplying the mandrel with positive air pressure during the entire
build process.
In this example, cone penetration tests were performed measure the soil
density
through the centers of two test piers, where one test pier was constructed
with a 4ft/3ft
up/down stroke pattern and the air injection technique described above and the
other was
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constructed with a 4ft/3ft up/down stroke pattern without the use of air. Cone
penetration
tests were performed by vertically advancing a 1.25 inch (3.2 cm) diameter
steel rod
affixed with a slightly larger 1.45 inch (3.7 cm) diameter cone tip through
the center of
the aggregate pier at a rate of approximately 2 inches per second while
simultaneously
measuring the penetration resistance with depth using an external load cell.
The
penetration resistance was measured by an external load cell with a sampling
rate of 2
samples per second, or equivalently, 1 sample per inch of penetration depth.
FIG. 18 shows a plot of the cone penetration resistance measured in tons per
square foot (tsf) versus depth below the ground surface in feet for both the
pier
constructed using air injection and the pier constructed without using air
injection. FIG.
18 shows that the cone penetration resistance for the pier constructed using
the air
injection technique was greater than that of the pier constructed without air
injection by
approximately 25-50 tsf in the upper 10 feet and 50-75 tsf from 10 to 20 feet.
The
increase in cone penetration resistance indicates a higher stiffness pier that
is associated
with a larger aggregate dosage during installation. The advantage of injecting
air pressure
during construction resulted in better aggregate flow that ultimately
increased the
constructed pier stiffness for the same compactive effort.
Following long-standing patent law convention, the terms "a," "an," and "the"
refer to "one or more" when used in this application, including the claims.
Thus, for
example, reference to "a subject" includes a plurality of subjects, unless the
context
clearly is to the contrary (e.g., a plurality of subjects), and so forth.
Throughout this specification and the claims, the terms "comprise,"
"comprises,"
and "comprising" are used in a non-exclusive sense, except where the context
requires
otherwise. Likewise, the term "include" and its grammatical variants are
intended to be
non-limiting, such that recitation of items in a list is not to the exclusion
of other like
items that can be substituted or added to the listed items.
For the purposes of this specification and appended claims, unless otherwise
indicated, all numbers expressing amounts, sizes, dimensions, proportions,
shapes,
formulations, parameters, percentages, parameters, quantities,
characteristics, and other
numerical values used in the specification and claims, are to be understood as
being
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modified in all instances by the term "about" even though the term "about" may
not
expressly appear with the value, amount or range. Accordingly, unless
indicated to the
contrary, the numerical parameters set forth in the following specification
and attached
claims are not and need not be exact, but may be approximate and/or larger or
smaller as
desired, reflecting tolerances, conversion factors, rounding off, measurement
error and
the like, and other factors known to those of skill in the art depending on
the desired
properties sought to be obtained by the presently disclosed subject matter.
For example,
the term "about," when referring to a value can be meant to encompass
variations of, in
some embodiments, 100% in some embodiments 50%, in some embodiments 20%,
in some embodiments 10%, in some embodiments 5%, in some embodiments 1%,
in some embodiments 0.5%, and in some embodiments 0.1% from the specified
amount, as such variations are appropriate to perform the disclosed methods or
employ
the disclosed compositions.
Further, the term "about" when used in connection with one or more numbers or
numerical ranges, should be understood to refer to all such numbers, including
all
numbers in a range and modifies that range by extending the boundaries above
and below
the numerical values set forth. The recitation of numerical ranges by
endpoints includes
all numbers, e.g., whole integers, including fractions thereof, subsumed
within that range
(for example, the recitation of 1 to 5 includes 1, 2, 3, 4, and 5, as well as
fractions thereof,
e.g., 1.5. 2.25, 3.75, 4.1, and the like) and any range within that range.
Although the foregoing subject matter has been described in some detail by way
of illustration and example for purposes of clarity of understanding, it will
be understood
by those skilled in the art that certain changes and modifications can be
practiced within
the scope of the appended claims.
31
