U.S. patent application number 09/882151 was filed with the patent office on 2002-01-24 for lateral displacement pier.
Invention is credited to Fox, Nathaniel S., Peterson, Gale M..
Application Number | 20020009337 09/882151 |
Document ID | / |
Family ID | 22788305 |
Filed Date | 2002-01-24 |
United States Patent
Application |
20020009337 |
Kind Code |
A1 |
Fox, Nathaniel S. ; et
al. |
January 24, 2002 |
Lateral displacement pier
Abstract
A method and special mechanical apparatus for installation of
support pier for structure comprises positioning a hollow tube
apparatus in a soil matrix wherein the hollow tube apparatus has a
hollow core and is susceptible to lateral and longitudinal
movement, removing soil from the hollow core and then filling that
core with an aggregate followed by raising and lowering of the
hollow tube apparatus by means of a special bottom mechanical
device in a manner which compacts the aggregate and also applies
lateral forces to the aggregate against the walls of the cavity in
the soil matrix, pushing a portion of the aggregate into the soil
matrix.
Inventors: |
Fox, Nathaniel S.;
(Scottsdale, AZ) ; Peterson, Gale M.; (Reinbeck,
IA) |
Correspondence
Address: |
BANNER & WITCOFF, LTD.
TEN SOUTH WACKER DRIVE
SUITE 3000
CHICAGO
IL
60606
US
|
Family ID: |
22788305 |
Appl. No.: |
09/882151 |
Filed: |
June 15, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60211773 |
Jun 15, 2000 |
|
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|
Current U.S.
Class: |
405/232 |
Current CPC
Class: |
E02D 5/72 20130101; E02D
7/20 20130101; E02D 3/08 20130101; E02D 5/46 20130101; E02D 5/44
20130101; E02D 5/385 20130101 |
Class at
Publication: |
405/232 |
International
Class: |
E02D 011/00 |
Claims
What is claimed is:
1. A method for installation of a pier comprising, in combination,
the steps of: a) positioning a hollow tube apparatus having a
longitudinal dimension and a lateral dimension in a soil matrix,
said hollow tube apparatus including a hollow core and a special
mechanical device lower end for directing both lateral and
longitudinal forces when raised and lowered and reciprocated
longitudinally in said soil matrix; b) removing the soil matrix
from the hollow core of the hollow tube apparatus; c) at least
partially filling the hollow tube apparatus with aggregate; and d)
raising and lowering the hollow tube apparatus incrementally to
impart lateral forces on the aggregate and soil matrix
simultaneously with longitudinal forces on the aggregate to thereby
form compacted lifts as the casing is removed in incremental steps
from the soil matrix.
2. The method of claim 1 wherein the step of filling the hollow
tube apparatus comprises filling with a material selected from the
group consisting of aggregate and dry cement, aggregate and
recycled concrete, recycled concrete, recycled asphalt, aggregate
and chemical additives, stone; drainage graded stone, stone and
sand, aggregate and mesh and combinations thereof.
3. The method of claim 1 including the further step of positioning
a mechanical device in the hollow core of the hollow tube apparatus
before placing aggregate in the casing.
4. The method of claim 3 wherein the mechanical device placed in
the hollow tube apparatus extends the longitudinal length of the
casing.
5. The method of claim 3 including the step of moving the
mechanical device in the aggregate to densify the aggregate.
6. The method of claim 5 including the steps of removing the
mechanical device from the hollow tube apparatus.
7. The method of claim 1 wherein the hollow tube apparatus is
positioned in a predrilled cavity.
8. The method of claim 1 wherein the hollow tube apparatus is
driven or pushed into the soil matrix.
9. The method of claim 1 wherein the hollow tube apparatus includes
a mechanical portion with a lower peripheral surface defining an
angle intermediate the longitudinal and lateral directions.
10. The method of claim 1 wherein removal of the soil matrix from
the hollow tube apparatus is by drilling.
11. The method of claim 1 wherein removal of the soil matrix from
the hollow tube apparatus is effected by excavating, by vacuum
suction, combinations thereof or other means.
12. The method of claim 1 including vibrating the hollow tube
apparatus.
13. The method of claim 1 including raising and lowering the hollow
tube apparatus incrementally and lowering the hollow tube apparatus
to impart forces on the soil matrix and aggregate.
14. A pier formed by the process of claim 1 or 3.
15. The method of claim 1 wherein the hollow tube apparatus is
formed with an inwardly beveled lower edge end comprising a special
mechanical device.
16. The method of claim 1 wherein the hollow tube apparatus is
cylindrical.
17. The method of claim 1 wherein the hollow tube apparatus
includes a uniform diameter hollow core, and a bottom mechanical
device with an internal rim at the bottom of the hollow tube
apparatus, said bottom mechanical device being beveled
inwardly.
18. The method of claim 1 wherein the completed or partially
completed aggregate pier may be preloaded to form a stiffer pier
and to prestress and prestrain the matrix soil in the vicinity of
the formed aggregate pier.
19. Apparatus for formation of an aggregate material pier in a soil
matrix comprising, in combination: (a) a hollow, elongate tube for
generally vertical insertion into the soil matrix, said elongate
tube including an open top end and an open bottom end, and a
generally constant cross section hollow passage between the bottom
and the top end, said bottom end having a reduced cross section and
comprising a shaped rim for providing longitudinal and lateral
forces simultaneously on the soil matrix as the tube is moved up
and down longitudinally in the soil matrix; and (b) an auger for
placement in the tube to remove soil matrix from the tube, said
auger sized to fit through the bottom end of the tube.
20. The apparatus of claim 18 further including a shaped rod member
for placement in the hollow tube upon removal of the auger, and
means for vibrating the rod member and incrementally lifting the
tube and the rod member in discrete steps.
Description
BACKGROUND OF THE INVENTION
[0001] In a principal aspect the present invention relates to a
pier construction for supporting structures in a soil matrix
wherein the pier is formed with a special mechanical apparatus from
an aggregate material by compacting successive lifts or sectors of
the aggregate material located in a cavity in the matrix.
[0002] In U.S. Pat. No. 5,249,892, incorporated herewith by
reference, a method and apparatus are disclosed for producing short
aggregate piers in situ. The process includes forming a cavity in
soil and then introducing successive layers of compacted aggregate
material into the cavity to form a pier that can support a
structure. The aggregate may be comprised of various materials. The
lifts or layers of aggregate which are compacted during the pier
forming process typically have a diameter of 1 to 3 feet and a
vertical rise of similar dimension and range. Thus, such piers are
made by drilling a hole or cavity in a soil matrix, placing
aggregate or other select fill material in small discreet layers in
the cavity, and then tamping each layer of the material in the
cavity with a special mechanical tamper apparatus to provide impact
or ramming energy to the layer of material. This apparatus and
process produces a stiff and effective stabilizing element or pier.
However, this method of pier construction has a limitation in terms
of the depth to which the pier forming process can be accomplished
economically. Typically the process described in the patent is
limited to a depth of approximately 20 feet because of the
equipment utilized, the time required to make a pier and the
techniques that are available. Thus, there has developed a need for
a mechanical apparatus, as well as a construction process, which
can be successfully and economically utilized at greater depths yet
have the attributes and benefits associated with the short
aggregate pier method, apparatus and construction disclosed in U.S.
Pat. No. 5,249,892.
SUMMARY OF THE INVENTION
[0003] Briefly, the present invention comprises a method for
installation of a pier formed from layers of aggregate material in
a soil matrix and includes the steps of positioning a hollow tube
with a special mechanical bottom compacting apparatus in the soil
matrix, removing the soil matrix from the core of the tube and the
special mechanical bottom compacting apparatus followed by at least
partially filling the tube and the special mechanical compacting
apparatus with an aggregate material and then raising and lowering
the tube and bottom apparatus within the soil matrix as the tube
and bottom apparatus are incrementally raised in steps from the
cavity. Raising and lowering of the tube and bottom apparatus
enables a specially designed lower portion of the bottom apparatus
to impact upon the aggregate material, thereby densifying the
material, forcing the material laterally outward and simultaneously
imparting lateral forces on the aggregate and the soil matrix and
applying longitudinal forces on the aggregate. The tube with bottom
apparatus may be vibrated while being incrementally raised and
lowered depending upon conditions of the soil matrix and
composition of the aggregate materials. The tube with bottom
apparatus may also be pushed downward or driven downward during the
"lowering" sequence to provide additional densification and lateral
force energy. In this manner, compacted lifts are incrementally
formed by the bottom apparatus as the tube is removed from the
cavity in the soil matrix. The process is continuously repeated
along the length of the soil cavity with a result that an elongate
pier of separately compacted layers or lifts is formed within the
soil matrix. A pier having a length or depth of fifty (50) feet or
more can be constructed in this manner.
[0004] Numerous types of aggregate materials may be utilized in the
practice of the process including a mixture of aggregate and dry
cement. Such mixture has proven to be beneficial in creating a pier
having significantly improved stiffness and integrity for support
of a structure, especially when the soil matrix is very soft and
weak.
[0005] The tube with bottom mechanical apparatus may be positioned
within the soil matrix in the event the soil is soft by forcing the
tube into the soil matrix with or without applying vibration
energy. If the soil is hard, the soil matrix may be pre-drilled to
form a cavity into which the tube apparatus is lowered or driven
prior to filling the tube with aggregate. In any event, the soil
contained within the hollow tube apparatus is removed from the tube
apparatus once the tube apparatus is lowered, pushed, vibrated,
driven or otherwise placed in the soil. A drill or other evacuation
technique is used to remove the soil from the interior of the
hollow tube apparatus. In soft soils, a removable cap or a
sacrificial cap may be placed at the bottom of the hollow tube
apparatus to prevent soil matrix from entering the tube. For such
situations, removal of the soil matrix from within the hollow tube
will not be necessary. Other steps described in the process of
making the lateral displacement pier remain essentially the same.
Other mechanical apparatus descriptions contained herein remain
essentially the same.
[0006] In a preferred embodiment, the lower portion of the tube
apparatus is designed with an inwardly extending bevel so that both
lateral and longitudinal forces may be imparted to aggregate in the
tube by the downward movement of the tube apparatus within the soil
matrix cavity during incremental raisings and lowerings. The bevel
may be effected by an internal thickening of material formed at the
lower end of the tube apparatus. In that event, the drill or auger
for removing the soil from the tube apparatus may have a special
construction including reduced diameter section at the distal end
of the drill or auger. The bevel may also be effected by an
external thickening of material formed at the lower end of the tube
apparatus. The bevel may also be effected by a combination of an
internal thickening and an external thickening of material formed
at the lower end of the tube apparatus.
[0007] During the practice of the method, the aggregate will be
compacted and thus additional aggregate will necessarily be added
to the tube apparatus as the aggregate is densified and compacted.
Upon completion of the formation of the pier and total removal of
the hollow tube apparatus from the soil matrix, the pier may be
pre-loaded, for example, by placement of a static or dynamic load
thereon, prior to placing a structure on the pier. This preloading
process will stiffen the constructed aggregate pier and will cause
prestressing and prestraining of the matrix soil in the vicinity of
the pier, thus increasing the support capacity of the pier.
[0008] Thus, it is an object of the invention to provide a special
hollow tube apparatus with a special designed bottom apparatus
portion to create a compacted aggregate pier that extends to a
greater depth and to provide an improved method for creating a pier
that extends to a greater depth than typically enabled or practiced
by prior short aggregate pier technology.
[0009] It is a further object of the invention to provide a method
or process for installing a pier formed of aggregate material
wherein the material has discrete compacted lifts along the length
of the pier with the hollow tube apparatus and special designed
bottom apparatus.
[0010] Yet a further object of the invention is to provide a method
for forming an elongate pier having improved load bearing
characteristics when incorporated in the soil matrix wherein the
pier is formed of a compacted aggregate material and the compaction
is effected by a hollow tube apparatus and special designed bottom
apparatus which is placed within a soil cavity filled with the
aggregate and may be vibrated, pushed downward, driven downward, or
a combination of these.
[0011] Yet another object of the invention is to provide an
improved method for forming a pier of aggregate material wherein
the aggregate may be chosen from a multiplicity of options,
including a mix of stone or other types of aggregate with dry
cement.
[0012] Yet a further object of the invention is to provide an
aggregate pier construction which is capable of being incorporated
in many types of soil and which is further capable of being formed
at greater depths than prior aggregate pier constructions.
[0013] These and other objects, advantages and features of the
invention will be set forth in the detailed description which
follows.
BRIEF DESCRIPTION OF THE DRAWING
[0014] In the detailed description which follows reference will be
made to the drawing comprised of the following figures:
[0015] FIG. 1 is a schematic cross sectional view of a first step
in the process of the invention;
[0016] FIG. 2 is a schematic cross sectional view of a further step
in the process of the invention;
[0017] FIG. 3 is a schematic view of further step in the process of
the invention;
[0018] FIG. 4 is a depiction in a schematic cross sectional view of
a further step in the practice of the invention;
[0019] FIG. 5 is a schematic view of another step in the process of
the invention;
[0020] FIG. 6 schematically depicts a further step in the practice
of the invention;
[0021] FIG. 7 is an enlarged schematic cross sectional view of the
special mechanical compacting apparatus which is used in the
practice of the invention;
[0022] FIG. 8 is a cross sectional view of the active end of the
hollow tube apparatus;
[0023] FIG. 9 is a cross sectional view of the hollow tube
apparatus of FIG. 7 along the line 9-9 as positioned in a soil
matrix incorporating an element which is used to help assist in
densifying the aggregate within the hollow tube apparatus;
[0024] FIG. 10 is a cross sectional view of the hollow tube
apparatus and aggregate similar to FIG. 9 wherein the element 30
has been removed;
[0025] FIG. 11 is a cross sectional view of a partially formed pier
by the special mechanical compacting apparatus and the disclosed
process;
[0026] FIG. 12 is a graph illustrating the comparative load testing
of piers of the present invention as compared with various prior
art constructions;
[0027] FIG. 13 is a cross sectional view of an alternative
embodiment and method for the practice of the invention;
[0028] FIG. 14 is an enlarged cross sectional view of an
alternative embodiment of the mechanical apparatus utilized in the
practice of the invention; and
[0029] FIG. 15 is an enlarged cross sectional view of an
alternative method for practice of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0030] FIGS. 1-7 illustrate the sequential steps in the performance
of the method of the invention and the resultant pier construction.
Referring to FIG. 1, the method is applicable to placement of piers
and supports for structures in a soil matrix 14 which requires
reinforcement. A wide variety of soils may require the practice of
the invention. With the invention it is possible to provide a pier
of aggregate material having greater stiffness and structural
integrity than some prior art aggregate piers and which can extend
to greater depths than some prior art aggregate piers thus enabling
support thereon of more massive and more weighty structures.
[0031] As a first step, a cavity or hole 16 is drilled in the soil
matrix 14. It is unnecessary, however, to remove the loose soil 14
from the cavity. Rather, by predrilling the hole to a desired
depth, for example, 50 feet, the soil 14 within the cavity is
loosened so that a casing 18 may be inserted or driven into the
cavity 16. As shown in FIG. 2, the hollow tube apparatus 18 may
comprise a cylindrical steel tube having a diameter, for example,
in the range of 24-36 inches. In the event that the soil 14 has
been predrilled in order to soften or agitate the soil 14, the
casing 18 can be vibrated as it is lowered into the drilled cavity
16. Alternatively, it is possible to remove the soil 14 during the
drilling operation and then place the hollow tube apparatus 18
within the generally hollow cavity. As a further alternative, in
the event the soil 14 is adequately soft, the hollow tube apparatus
may be driven or pushed or vibrated, or a combination of these,
into the soil 14 to the desired depth without predrilling or
otherwise loosening the soil 14. The character of the soil 14
matrix will thus dictate, at least in part, the particular
procedure adopted.
[0032] Typically, the hollow tube apparatus 18 is cylindrical
although other shapes may be utilized. Typically, the diameter of
the hollow tube apparatus is 24-36 inches, although other diameters
may be utilized in the practice of the invention. Also typically,
the hollow tube apparatus 18 will extend to the ultimate depth of
the pier or within 36 inches or less of the ultimate depth of the
pier. A portion of the hollow tube apparatus 18 will typically
extend above the gradient or plane 20 of the soil matrix 14 as
depicted in FIG. 2. This enables the hollow tube apparatus 18 to
provide a top opening 22 which may be engaged or gripped to vibrate
the hollow tube apparatus 18 and which may also serve as an inlet
spout to the interior or hollow core 24 of the hollow tube
apparatus 18.
[0033] FIG. 3 illustrates a further step in the practice of the
invention. The soil 14 within the hollow core 24 of the tube
apparatus 18 is removed after the tube apparatus 18 is positioned
in soil 14. As shown in FIG. 3, an auger 50 may be inserted within
the hollow tube apparatus 18 to remove soil 14 from the hollow tube
apparatus 18. Typically, the auger 50 will remove the soil 14 only
from the entire core or interior 24 of the hollow tube apparatus
18. However, in circumstances such as depicted in FIG. 3, the auger
50 may project below the lower end 26 of the hollow tube apparatus
18 to remove soil 14 from the region below the hollow tube
apparatus 18. Additionally, in the event the hollow tube apparatus
18 includes a rim construction described below, auger 50 may have a
special construction including a reduced diameter blade as depicted
in FIG. 3 and as further discussed below, to remove loose soil 14
from beneath the hollow tube apparatus 18.
[0034] FIG. 4 represents a subsequent sequential step in the
practice of the invention. The step of FIG. 4 is optional and may
or may not be included depending upon the size or diameter of the
hollow tube apparatus 18, the depth of the hollow tube apparatus 18
in the soil matrix 14 and the aggregate or material which is used
in the formation of the pier. As depicted in FIG. 4, an element 30
is positioned generally axially within the hollow tube apparatus
18. The element 30 may have any desired cross sectional shape
including a rod type shape or an I-beam shape. The element 30,
however, must be positioned and located so that it can be vibrated.
In a preferred embodiment, the element 30 extends the entire
longitudinal depth of the hollow tube apparatus 18 within the soil
matrix 14 although it may extend for a lesser depth if so desired.
FIG. 9 illustrates, in cross sectional view, the element 30 and its
operation as described below in more detail.
[0035] Next, referring to FIG. 5, aggregate material 25 is filled
into the hollow core 24 of the tube apparatus 18. The aggregate 25
is preferably clean stone material. An alternative aggregate 25
comprises clean stone without fines or graded stone with fines, and
with dry cement. The combination of dry cement and stone has been
found to be especially advantageous and preferable in the practice
of the invention under certain soil matrix conditions such as very
soft and weak soils. Note, however, that many alternative choices
exist with respect to the material used as an aggregate 25.
Aggregate 25 should therefore be interpreted broadly to include
various materials and mixtures including stone, recycled concrete,
recycled asphalt, sand, chemical additives, other additives and
materials including mesh materials, and mixtures thereof. The
aggregate 25 typically, however, does not include viscous concrete,
i.e, a slurry that is mixed, cured and then hardens. Rather, the
aggregate 25 comprises separate particulate matter including
multiple types of particulate and additives thereto all of which
are compacted in layers in the process of forming the pier of the
invention. The physically compacted materials are compressed
longitudinally in the direction of the hollow tube apparatus 18
inserted into the soil matrix and forced laterally to engage and
displace the sides of the soil matrix 14.
[0036] As shown in FIG. 5, the optional element 30 is surrounded by
the aggregate 25 which is placed in the hollow tube apparatus 18.
Typically, the aggregate 25 is filled to the top of the hollow tube
apparatus 18 and as the aggregate material 18 is compacted, it may
be necessary to add additional aggregate 25 to the hollow tube
apparatus 18. Also, it is possible that various types of aggregate
25 may be provided in various sections along the length of the
casing. For example, dry stone material having a certain drainage
gradation may be provided at the lower end of the pier within the
hollow tube apparatus 18. Thereafter, a mixture of stone and dry
cement may be provided with ad-mixtures of chemicals, mesh
materials and the like. Thus, the hollow tube apparatus 18 may
include various alternative types of aggregate 25 along the length
or depth of the formed cavity 18.
[0037] The next step schematically shown in FIG. 6 involves
vibration of the insert element 30 and/or the hollow tube apparatus
18, or both. As mentioned above, the insert element 30 is an
optional element. Vibration of the element 30 will cause
densification and settling of the aggregate material. This lateral
vibration process is graphically illustrated in greater detail in
FIG. 9 with typical vibration positions illustrated in phantom. The
element 30 is depicted in a cross sectional view in FIG. 9 and
vibrates or oscillates from side to side as well as longitudinally
or lengthwise (FIG. 6 and 7), or both, within the hollow tube
apparatus 18.
[0038] The element 30 may be retained within the hollow tube
apparatus 18 preferably initially axially aligned with the
centerline axis of the apparatus 18. As the hollow tube apparatus
18 is withdrawn, element 30 is caused to oscillate or vibrate and
further transfer and compact and densify the aggregate material 25.
Alternatively, the element 30 may be vibrated and then removed from
the hollow tube apparatus 18 prior to initial upward movement of
the hollow tube apparatus 18 within the soil cavity 14. Also, the
assembly of the element 30 and the hollow tube apparatus 18 may be
simultaneously vibrated and removed from the soil 14. All of these
possibilities are available depending upon the soil 14, the
aggregate material 25, the depth of the pier, the lateral width of
the pier and other parameters. A choice can thus be made as to the
most appropriate alternative for the particular construction
project. The element 30 is, of course, optional or alternative in
the method and practice of the invention.
[0039] Referring next to FIG. 7, the element 30 may be vibrated and
removed and subsequently the hollow tube apparatus 18 may be
vibrated both laterally and longitudinally. Typically, however, the
casing (hollow tube apparatus) 18 is vibrated longitudinally. As
depicted in FIG. 8, the lower portion 26 of the hollow tube
apparatus 18 has a preferred mechanical shape or configuration.
Specifically, the lower end 26 of the hollow tube apparatus 18 has
a thickened ring portion with an inwardly beveled configuration
defined by inwardly beveled surface 42. The inwardly beveled
surface 42 formed in the lower end 26 of the hollow tube apparatus
18 includes a rim member 44 welded or otherwise attached to the
inside of the hollow tube apparatus 18. Although the preferred
method is to have the rim member permanently attached to the hollow
tube apparatus, an option in that the rim member may be temporarily
affixed to the hollow tube apparatus. A rim member 44 extends
around the entire, interior circumference of the hollow tube
apparatus 18. The rim member may also extend around the entire,
exterior circumference of the hollow tube apparatus as shown in
FIG. 14. Alternatively, rim members may extend around the entire
internal and the entire external circumference of the hollow tube
apparatus as also shown in FIG. 14. In all cases, an inwardly
beveled surface is created by the rim member, or by the rim member
and the tube bottom itself, whether the rim member extends around
the interior circumference, the exterior circumference, or both the
interior and the exterior circumference of the hollow tube
apparatus.
[0040] The rim member 44 defines a portion of surface 42 which,
when the hollow tube apparatus 18 is vibrated, effects transfer of
energy from the surface 42 to the aggregate material 25 and
ultimately the surrounding matrix soil 14. Thus, as the hollow tube
apparatus 18 typically vibrates longitudinally or up and down in
the figures causing, the surface 42 to impart a lateral vector
force against aggregate material 25 as well as the soil 14 matrix
as diagramatically depicted in FIG. 10. Another vector force will
simultaneously be imparted downwardly on the aggregate material 25.
The magnitude of the respective vector forces is dependent upon the
angle of the bevel 42 as well as the frequency and amplitude of the
vibration and the surface area of the beveled surface 42.
Additionally, the surface 42 may connect to a transverse surface 46
of rim 44 which will impart forces in the longitudinal direction on
the aggregate material 25. The design of these surfaces 42, 26 and
their extent thus become an important feature of the invention.
Typically, for example, a hollow tube apparatus having a diameter
of 30 inches will include an interior rim member 44 having a wall
thickness of 1 to 11/2 inches. That, in combination with the wall
thickness of the hollow tube apparatus 18 will provide a total wall
thickness of approximately 2 to 21/2 inches. Such a wall will have
a bevel surface 42 and a lower impact surface 46. The bevel surface
42 will typically form an angle of 45 degrees within casing 18 axis
though the angle may be varied, preferably in the range of between
15 and 75 degrees from horizontal as depicted in FIG. 8.
[0041] In practice, the hollow tube apparatus 18 will be located at
a fixed depth in cavity 16 and vibrated at a certain position
within the cavity 16. The hollow tube apparatus 18 will then be
moved upwardly a certain distance equivalent, for example, to twice
the height of a completed lift, e.g. about 24 inches. Lowering of
the hollow tube apparatus, with or without vibration, will then
cause impaction of material 25 once again. In this manner, a series
of lifts along the length of the pier will be formed. Each lift
will comprise a compacted material resulting in lift elements
having a general configuration of the type depicted and described
in U.S. Pat. No. 5,249,892, although bulging may not be as
pronounced and interior portions of the pier may not be as
densified as with the short aggregate pier described in U.S. Pat.
No. 5,249,892. The elements, however, are formed in a manner that
does not utilize a separate tamping tool. Rather, the hollow tube
apparatus with special mechanically designed bottom portion 18 acts
as a tamping mechanism and also as a vibrating mechanism, and the
alternative vibrating element 30 further facilitates densification
and tamping. The element 30 may also act as a tamping device when
employed.
[0042] With the hollow tube apparatus 18 configuration depicted in
FIG. 8, an auger 50 as shown in FIG. 3 may be utilized to remove
the original soil 14 from the hollow tube apparatus 18. The auger
50 may include a reduced diameter blade 52 which will fit through
the region incorporating the thickened mechanical rim 44 so that
soil matrix 14 can be removed from beneath the end 26 of the hollow
tube apparatus 18. In this manner, when aggregate 25 is placed
within the hollow tube apparatus 18, it will initially form a bulb
27 in a compressed region of material 25 beneath the end 26 of the
hollow tube apparatus 18 as depicted in FIG. 11. The auger 50
further includes an increased diameter blade section 54 for
evacuation of the interior or core of the hollow tube apparatus
18.
[0043] The element 30 may also constitute a hollow tube with an end
formed in the manner depicted in FIG. 8. Thus, both the hollow tube
apparatus 18 as well as the element 30 may receive and feed
aggregate into the soil cavity and act to form and tamp the
material 14 and form the respective lifts as the element 30 and
hollow tube apparatus 18 are alternately lifted vertically and
lowered with or without vibration, and with or without pushing or
driving energy applied as described. beams to apply vertical
compressive loads in increments. Load deflection readings were made
of each pier, and the load deflection curves were plotted and are
shown on FIG. 12. Stiffness Modulus values were determined by
dividing the stress values at top of pier by the corresponding pier
movements (deflections). A similar load test was performed of the
stone column pier. Results of that load test are also shown on FIG.
12.
[0044] Deflections corresponding to top of pier stresses of 6,000,
8,00, 10,000, and 12,000 psf are shown on Table 1. Modulus values
corresponding to the same top of pier stress are also shown on
Table 1. Ratios of modulus values produced by the beveled lateral
displacement pier to modulus values produced by the non-beveled
lateral displacement pier are shown on Table 1, as well as ratios
of the beveled lateral displacement pier modulus values to those of
the stone column.
[0045] It can readily be seen that stiffness modulus values
produced by the beveled lateral displacement pier are significantly
greater than those of the non-beveled lateral displacement pier.
For example, within the 6,000 to 8,000 psf top of pier stress
range, modulus values of the beveled pier are about 3 times
greater. It is further shown that stiffness modulus values of the
beveled lateral displacement pier are significantly greater than
the stone column pier. For the 6,000 to 8,000 psf top of pier
stress range, modulus values of the beveled lateral displacement
pier are about 4 times greater than those of the stone column
pier.
[0046] The beveled lateral displacement pier produced stiffer
elements than the other two piers. Deflections corresponding to
applied to of pier stresses were less than corresponding
deflections of the non-beveled and non-thickened hollow tube
apparatus pier, and even greater differences were measured in
comparing the beveled lateral displacement pier with the stone
column pier.
[0047] Although the movement of the hollow tube apparatus 18 and
the optional element 30 is described to be performed in incremental
and generally equal steps, it is possible to vary the amount of
movement of the hollow tube apparatus 18 and element 30 during each
of the separate steps of longitudinal movement. Movement may also
be simultaneous or non-simultaneous. Also, the direction, amplitude
and frequency of vibration may be varied depending upon the
material forming the aggregate pier and other factors. Also, the
application of downward pushing energy or driving energy may be
varied or may be omitted depending upon the material forming the
aggregate pier and other factors. Also, the application of downward
pushing energy or driving energy may be varied or may be omitted
depending upon the material forming the aggregate pier and other
factors. In any event, successive lifts 29 are formed as depicted
in FIG. 11.
[0048] Further, the aggregate may contain fluid materials or
chemicals or the hollow tube apparatus 18 may be coated to
facilitate aggregate flow and compaction. The hollow tube apparatus
18 may be precoated or fluids added during the vibration steps or
otherwise as discussed hereinafter.
[0049] The process and resulting product piers or columns were
built and tested in comparison to prior art stone columns. Two
lateral displacement piers and one stone column pier were installed
in May, 2001 on the same site and in similar soil conditions. Each
of these three piers was of the same diameter and each was of the
same length. The two lateral displacement piers were each
constructed with a different apparatus, one with an outward-facing
bevel at the bottom side wall and a thickened bottom apparatus
attached to a hollow tube apparatus. The other Lateral Displacement
Pier was constructed with the hollow tube apparatus extending full
length, and without the beveled thickened bottom apparatus portion
with the outward-facing beveled bottom.
1TABLE 1 Table 1 reports the observed results. Top of Pier Stress
6,000 psf 8,000 psf 10,000 psf 12,000 psf 1. Deflections, inches
Beveled Lateral 0.50 0.86 1.43 2.29 Displacement Pier (LDP)
Non-Beveled LDP 1.48 2.48 3.52 4.57 Stone Column 2.10 3.48 5.02
6.26 2. Modulus Values, pci Beveled LDP 83.3 64.6 48.6 36.4
Non-Beveled LDP 28.2 22.4 19.7 18.2 Stone Column 19.8 16.0 13.8
13.3 3. Ratio of Modulus Values Beveled LDP 3.0 2.9 2.5 2.0
Non-Beveled LDP Stone Column 4.2 4.0 3.5 2.7
[0050] Additional embodiments and variations of the invention,
including the method of the invention and the apparatus for
practice of such methods, are contemplated. Referring to FIG. 13,
an alternative embodiment is depicted as well as an alternative
method of practice of the invention. In particular, a casing 18 is
provided with an end cap 80. In the embodiment depicted, the end
cap 80 has a pointed configuration and is held in place on the
casing by means of a removable lock ring 82. The lock ring 82 may
be rotated, for example, to release the cap 80 for removal of the
cap 80 upon the desired depth of penetration of casing 18 into a
soil matrix. Alternatively, the cap 80 may be left in position
within the ground or soil matrix by merely releasing the cap
retaining ring 82.
[0051] In any event, the apparatus of FIG. 13 is provided to close
the hollow tube in order to keep soil from entering the tube or
casing 18 as it penetrates the soil matrix. The casing or hollow
tube 18 can then be driven, vibrated, pushed or manipulated by a
combination of the described methods to assume a desired depth in
the soil matrix. The bottom cap 82 may then be left in place or
removed through the hollow tube. The column or pier is then
constructed in the manner previously described. The bottom cap 80
has the dual function of providing a means for effectively
effecting penetration of the casing 18 while prohibiting ingress of
the matrix into the casing 18.
[0052] FIG. 14 illustrates an alternative embodiment of the end
construction of casing 18. This is an alternative to the
construction illustrated, for example, in FIG. 8. In the
construction of FIG. 14, the casing or tube 18 includes an annular
or circular rim 86 which preferably includes a lower beveled edge
88 and an upper beveled edge 90 to facilitate movement of the
casing end 18 and ring 86 into and out of the soil. The ring 86 may
be used in combination with an internal annular ring or member 44
of the type depicted in FIG. 7 or in place of such an annular ring
or member 44.
[0053] FIG. 15 illustrates yet another method feature of the
invention as an alternative. Specifically, the insert element 30
(or the auger 50) may be utilized to provide insertion of mix
materials into the casing 18 as the various lifts formed by the
casing 18 are sequentially created. That is, the element 30 (or the
auger 50) may include exit passages 96 and mixing blades 98. The
exit passages 96 permit the insertion of a soil mixing compound
such as lime or cement into the material forming the lifts. The
blades 98 effect a mixing action upon vibration, rotation, or other
movement of the insert element 30. Thus, the material forming the
lifts may be mixed in situ. Various additives may be included. The
additives may be varied with respect to each of the separately
formed lifts.
[0054] It is possible to vary the construction and method of
operation of the invention without departing from the spirit and
scope thereof. Alternative hollow tube apparatus configurations,
sizes and lengths of piers may be utilized. The element 30 may be
varied in its configuration and use. It is also an optional element
and may or may not be used depending on the type of aggregate used
and other factors. Therefore, the invention is to be limited only
by the following claims and equivalents thereof.
* * * * *