U.S. patent application number 15/872715 was filed with the patent office on 2019-07-18 for soil reinforcement system including angled soil reinforcement elements to resist seismic shear forces and methods of making same.
This patent application is currently assigned to Geopier Foundation Company, Inc.. The applicant listed for this patent is Geopier Foundation Company, Inc.. Invention is credited to Russell Green, Kord J. Wissmann.
Application Number | 20190218742 15/872715 |
Document ID | / |
Family ID | 67213632 |
Filed Date | 2019-07-18 |
View All Diagrams
United States Patent
Application |
20190218742 |
Kind Code |
A1 |
Green; Russell ; et
al. |
July 18, 2019 |
Soil Reinforcement System Including Angled Soil Reinforcement
Elements To Resist Seismic Shear Forces And Methods Of Making
Same
Abstract
A soil reinforcement system including angled soil reinforcement
elements to resist seismic shear forces and methods of making same
are disclosed. For example, the soil reinforcement system includes
an array or grid of angled soil reinforcement elements installed
within the ground, wherein the angled reinforcement elements are
designed to absorb and/or resist earthquake-induced seismic shear
forces by transferring the applied shear forces into axial
compressive and tensile forces within each of the angled
reinforcement elements.
Inventors: |
Green; Russell; (Davidson,
NC) ; Wissmann; Kord J.; (Davidson, NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Geopier Foundation Company, Inc. |
Davidson |
NC |
US |
|
|
Assignee: |
Geopier Foundation Company,
Inc.
Davidson
NC
|
Family ID: |
67213632 |
Appl. No.: |
15/872715 |
Filed: |
January 16, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E04H 9/021 20130101;
E02D 27/34 20130101 |
International
Class: |
E02D 27/34 20060101
E02D027/34; E04H 9/02 20060101 E04H009/02 |
Claims
1. A method of installing an array of angled soil reinforcement
elements to absorb seismic shear stresses in a soil matrix,
comprising inserting an array of angled soil reinforcement elements
into a soil matrix at a determined angle and to a determined depth,
wherein each of the soil reinforcement elements of the array of
angled soil reinforcement elements comprises a material that
exhibits a stiffness modulus greater than the stiffness modulus of
the soil matrix and wherein seismic shear stresses imparted from
seismic activity are absorbed by the array of angled soil
reinforcement elements, thus reducing a potential for soil
liquefaction, wherein the soil reinforcement elements are spaced
from each other such that none of the angled soil reinforcement
elements within the array are in direct contact with another angled
soil reinforcement element within the array.
2. The method of claim 1, wherein the soil reinforcement elements
are inserted in the soil matrix by drilling means.
3. The method of claim 1, wherein the angled soil reinforcement
elements are inserted in the soil matrix by driving means.
4. The method of claim 1, wherein the angled soil reinforcement
elements within the array comprise metallic material.
5. The method of claim 1, wherein the angled soil reinforcement
elements within the array comprise non-metallic material.
6. The method of claim 1, wherein the angled soil reinforcement
elements within the array comprise a combination of metallic and
non-metallic materials.
7. The method of claim 1, wherein the determined depth is selected
based on the in-situ liquefaction susceptibility of the matrix
soil.
8. The method of claim 1, wherein the spacing and diameter of the
array of angled soil reinforcement elements is determined such that
the transfer of the seismic shear stresses to the array of angled
soil reinforcement elements is sufficient to reduce shear strains
in the soil to reduce the triggering of liquefaction.
9. The method of claim 1, wherein the angle of inclination is a
predetermined angle based on desired installation and load transfer
efficiency criteria.
10. The method of claim 1, wherein the angled soil reinforcement
elements comprise cast-in-place shafts that are formed in the soil
matrix.
11. The method of claim 10, wherein the shafts are filled with one
or more of concrete and grout.
12. The method of claim 11, wherein the angled soil reinforcement
elements are installed using a mandrel driven or pushed into the
ground and filled with the one or more of concrete and grout, and
then the mandrel is extracted.
13. The method of claim 11, wherein the method further comprises
forming an angled drilled hole in the soil matrix and filling the
angled hole with the one or more of concrete and grout.
14. The method of claim 11, wherein reinforcing steel is added to
the one or more of concrete and grout shafts prior to curing.
15. The method of claim 1, wherein the angled soil reinforcement
elements are installed in the soil matrix by piling equipment and
are driven or pushed into the soil matrix and are filled with an
in-fill after driving.
16. The method of claim 1, wherein the angled soil reinforcement
elements are hollow and are filled with an in-fill material after
installation.
17. The method of claim 16, wherein the in-fill material comprises
one or more of concrete, grout, gravel, aggregate, sand, recycled
concrete, crushed glass, and other flowable or pumpable
material.
18. The method of claim 16, wherein the in-fill material is
compacted in place using a compaction device.
19. The method of claim 1, wherein the angled soil reinforcement
elements comprise a permeable material that facilitates drainage of
excess pore water pressures during and after seismic events.
20. The method of claim 1, wherein the array of angled soil
reinforcement elements are installed on a grid pattern.
21. The method of claim 20, further comprising a second grid
pattern of two or more angled soil reinforcement elements angled
180 degrees from the first grid pattern of the array of angled soil
reinforcement elements.
22. The method of claim 20, further comprising a second grid
pattern of two or more angled soil reinforcement elements installed
in a transverse direction relative to a direction of the first grid
pattern of the array of angled soil reinforcement elements.
23. The method of claim 22, wherein the transverse direction is
perpendicular to the first grid pattern.
24. The method of claim 22, wherein the transverse direction is not
perpendicular to the first grid pattern.
25. An array of angled soil reinforcement elements for absorbing
seismic shear stresses in a soil matrix, the array of angled soil
reinforcement elements installed in a soil matrix each at a
determined angle relative to the soil matrix and to a determined
depth in the soil matrix, the array of soil reinforcement elements
each comprising a material that exhibits a stiffness modulus
greater than the stiffness modulus of the soil matrix wherein
seismic shear stresses are absorbed by the array of angled soil
reinforcement elements to reduce potential for soil liquefaction,
wherein each of the angled soil reinforcement elements are spaced
from each other such that none of the angled soil reinforcement
elements are in direct contact with another angled soil
reinforcement element within the array, and wherein spacing between
each angled soil reinforcement element of the array is about four
feet to about thirty feet.
26. A system for installing an array of angled soil reinforcement
elements to absorb seismic shear stresses, comprising: a) an array
of angled soil reinforcement elements; and b) a device for
installing the array of angled soil reinforcement elements into a
soil matrix at a determined angle and to a determined depth;
wherein each angled soil reinforcement element of the array of
angled soil reinforcement elements comprise a material that
exhibits a stiffness modulus greater than the stiffness modulus of
the soil matrix wherein seismic shear stresses in the soil matrix
imparted from seismic activity are absorbed by the array of angled
soil reinforcement element to reduce potential for soil
liquefaction, wherein each of the angled soil reinforcement
elements are spaced from each other such that none of the angled
soil reinforcement elements are in direct contact with another
angled soil reinforcement element within the array, and wherein
spacing between each angled soil reinforcement element of the array
is about four feet to about thirty feet.
27. The system of claim 26 wherein the device for installing the
array of angled soil reinforcement elements into the soil matrix
comprises a piling device for driving or pushing each of the angled
soil reinforcement elements into the soil matrix.
28. The system of claim 26 wherein the device for installing the
array of angled soil reinforcement elements into the soil matrix
comprises a mandrel driven or pushed into the soil matrix, wherein
the mandrel is filled with one or more of grout and concrete, and
then the mandrel is extracted.
29. The system of claim 26 wherein the device for installing the
array of angled soil reinforcement elements into the soil matrix
comprises a drilling device wherein the drilling device forms an
angled drilled hole in the soil matrix and the hole is then filled
with one or more of concrete and grout.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to and incorporates by
reference U.S. patent application Ser. No. 13/912,986 filed Jun. 7,
2013, entitled "Soil Reinforcement System Including Angled Soil
Reinforcement Elements To Resist Seismic Shear Forces And Methods
Of Making Same" that claims priority to U.S. Provisional
Application Ser. No. 61/656,687 filed Jun. 7, 2012, entitled
"Method and Apparatus for Creating Inclined Soil Reinforcement
Elements to Resist Seismic Shear Forces," the disclosures of which
are expressly incorporated by reference herein in their
entirety.
TECHNICAL FIELD
[0002] The presently disclosed subject matter relates generally to
mechanisms for resisting earthquake seismic shear stresses and
forces and more particularly to a soil reinforcement system
including angled soil reinforcement elements to resist seismic
shear forces and methods of making same.
BACKGROUND
[0003] Earthquakes occur as a result of tectonic activity. When
earthquakes occur they shake the bedrock in the vicinity of the
fault rupture that results in shearing stresses applied to the soil
column above the rock. Pore fluid is the groundwater held within a
soil or rock; namely, in the gaps between particles (i.e., in the
pores). Pore water pressure refers to the pressure of groundwater
held within the pores of the soil or rock.
[0004] Seismically-induced shearing forces propagate upwards
through the soil profile, often resulting in damage to existing
structures and sometimes resulting in soil liquefaction.
Liquefaction is a phenomenon that occurs in saturated soils that
involves the transfer of the effective overburden load from the
soil grains to the pore fluid, with the commensurate reduction in
effective stress and, hence, reduction in soil strength. In
earthquake-induced liquefaction, this transfer is initiated in
sandy soils by the collapse of the soil skeleton due to earthquake
shaking. Following liquefaction, settlement occurs as the pore
water pressures dissipate. Soil liquefaction can result in billions
of dollars in structural damage and can lead to a loss of life.
[0005] Many methods are available to mitigate the effects of soil
liquefaction or to render the soil non-liquefiable. Deep
foundations (e.g., driven pilings, drilled concrete-filled shafts)
can be used to bypass the liquefiable soil and reduce the effects
of liquefaction. Dynamic compaction, vibroflotation, and the
installation of stone columns are some methods used to densify
clean granular soils and thereby reduce liquefaction potential.
Vertical stiff inclusions have also been used to absorb seismic
shear stresses to reduce liquefaction potential. However, this
method is partially limited in its effectiveness because the
elements, if sufficiently slender, inherently are more efficient at
resisting shear forces through flexure (i.e., bending) in lieu of
shear.
SUMMARY
[0006] In one aspect, the presently disclosed subject matter
relates to a method of installing one or more angled soil
reinforcement elements to resist seismic shear stresses. The method
comprises inserting an angled stiff element into a soil matrix at a
determined angle and to a determined depth. The one or more angled
stiff elements preferably have a sufficient rigidity and area ratio
such that seismic shear stresses imparted from seismic activity are
transferred to the angled stiff element, thus reducing a potential
for soil liquefaction. The one or more angled stiff elements may be
inserted in the soil matrix by drilling means or by driving means.
The one or more angled stiff elements comprise a material that
exhibits a stiffness modulus greater than that of the soil matrix,
which may comprise metallic material, non-metallic material, or a
combination of metallic and non-metallic materials. In one
embodiment, the one or more angled stiff elements are installed in
an array.
[0007] The determined depth of the one or more angled stiff
elements may be selected based on the in-situ liquefaction
susceptibility of the matrix soil. The spacing and diameter of the
one or more angled stiff elements may be determined such that the
transfer of the seismic shear stresses to the elements is
sufficient to reduce the shear strains in the soil to reduce the
triggering of liquefaction. The angle of inclination may be a
predetermined angle based on desired installation and load transfer
efficiency criteria.
[0008] The one or more angled stiff elements may comprise
cast-in-place shafts that are formed in the soil matrix. The shafts
may be filled with concrete and/or grout. The one or more angled
stiff elements may be installed using a mandrel driven or pushed
into the ground and filled with the concrete and/or grout, and then
the mandrel is extracted. The method may further comprise forming
an angled drilled hole in the soil matrix and filling the angled
hole with the concrete and/or grout. Reinforcing steel may also be
added to the concrete and/or grout shafts prior to curing.
[0009] The one or more angled stiff elements may be installed in
the soil matrix by piling equipment and may be driven or pushed
into the soil matrix and may be filled with an in-fill after
driving. The one or more angled stiff elements may be hollow and
may be filled with an in-fill material after installation. In-fill
material may comprise one or more of concrete, grout, gravel,
aggregate, sand, recycled concrete, crushed glass, or other
flowable or pumpable material. Further, the in-fill material may be
compacted in place using a compaction device. In one embodiment,
the one or more angled stiff elements may comprise a material with
high permeabilities that facilitate drainage of excess pore water
pressures during and after seismic events.
[0010] The one or more angled stiff elements may be installed on a
grid pattern. The method may also further comprise a second grid
pattern of one or more angled stiff elements angled 180 degrees
from the first grid pattern of the one or more angled stiff
elements. The method may also comprise a second grid pattern of one
or more angled stiff elements installed in the transverse direction
to that of the first grid pattern of the one or more angled stiff
elements. The transverse direction of the second grid pattern may
be either perpendicular to the first grid pattern or not
perpendicular to the first grid pattern.
[0011] In another aspect, the presently disclosed subject matter
relates to an angled stiff element for resisting seismic shear
stresses. The angled stiff element has a sufficient rigidity and
area ratio such that seismic shear stresses are transferred to the
angled stiff element, thus reducing a potential for soil
liquefaction. The angled stiff element may comprise a material that
exhibits a stiffness modulus greater than that of a matrix soil in
which it is installed.
[0012] In a further aspect, the presently disclosed subject matter
relates to a system for installing one or more angled soil
reinforcement elements to resist seismic shear stresses and forces.
The system comprises: a) one or more angled soil reinforcement
elements and b) a device for installing the one or more angled soil
reinforcement elements into a soil matrix at a determined angle and
to a determined depth. The device for installing the one or more
angled soil reinforcement elements into the soil matrix may
comprise a piling device for driving or pushing the one or more
angled soil reinforcement elements into the soil matrix. The device
for installing the one or more angled soil reinforcement elements
into the soil matrix may also comprise a mandrel driven or pushed
into the soil matrix, the mandrel is filled with grout and/or
concrete, and then the mandrel is extracted. The device for
installing the one or more angled soil reinforcement elements into
the soil matrix may also comprise a drilling device. In one
embodiment, the drilling device forms an angled drilled hole in the
soil matrix and the hole is then filled with concrete and/or
grout.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] 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:
[0014] FIG. 1 and FIG. 2 illustrate a side view and top down view,
respectively, of an example of a soil reinforcement system that
includes angled reinforcement elements for absorbing
earthquake-induced seismic shear stresses and forces in accordance
with the present invention;
[0015] FIG. 3 illustrates a side view of one angled reinforcement
element and showing more details thereof;
[0016] FIG. 4, FIG. 5, and FIG. 6 illustrate side views of a
process of forming and installing an angled reinforcement element
according to one embodiment of the invention,
[0017] FIG. 7 illustrates a flow diagram of an example of a method
of forming and installing the angled reinforcement element of FIG.
4, FIG. 5, and FIG. 6;
[0018] FIG. 8 and FIG. 9 illustrate side views of a process of
forming and installing an angled reinforcement element according to
another embodiment of the invention;
[0019] FIG. 10 illustrates a flow diagram of an example of a method
of forming and installing the angled reinforcement element of FIG.
8 and FIG. 9;
[0020] FIG. 11 and FIG. 12 illustrate side views of a process of
forming and installing an angled reinforcement element according to
yet another embodiment of the invention;
[0021] FIG. 13 illustrates a flow diagram of an example of a method
of forming and installing the angled reinforcement element of FIG.
11 and FIG. 12;
[0022] FIG. 14 shows a schematic of the transfer of seismic shear
forces to the angled reinforcement element and to the matrix soil
around the angled reinforcement element in accordance with the
present invention;
[0023] FIG. 15 shows a schematic of the load transfer mechanism
provided by the present invention loaded by one shear force;
[0024] FIG. 16 shows a schematic of the propagation of the
distribution of sinusoidal shear stresses applied within
unreinforced soil mass at two time intervals for a simulated
earthquake;
[0025] FIG. 17 shows a schematic of the load transfer mechanisms
provided by the present invention loaded by two shear forces;
[0026] FIG. 18 shows a plot of the normalized shear stress vs.
normalized depth for an array of angled reinforcement elements of
the present invention; and
[0027] FIG. 19 shows a plot of the normalized shear stress vs.
normalized depth for an array of conventional prior art vertical
elements.
DETAILED DESCRIPTION
[0028] The presently disclosed subject matter will now 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.
[0029] In some embodiments, the presently disclosed subject matter
provides a soil reinforcement system including angled soil
reinforcement elements to resist seismic shear forces and methods
of making same. In particular, the invention is directed to a soil
reinforcement system for and methods of installing angled
reinforcement elements within the ground, wherein the angled
reinforcement elements are designed to absorb and/or resist
earthquake-induced seismic shear forces by transferring the applied
shear forces into axial compressive and tensile forces within each
of the angled reinforcement elements.
[0030] In one aspect, a soil reinforcement system and method is
provided for the installation of angled reinforcement elements in
soils subject to earthquake ground motions. A method consists of
inserting an angled reinforcement element with a sufficient
rigidity and area ratio into the soil profile such that the seismic
shear stresses are transferred to the angled reinforcement element,
thus reducing the potential for soil liquefaction. The angled
reinforcement elements may be inserted by drilling, driving, or
other means and may consist of metallic materials (e.g., steel,
cast iron, aluminum,), non-metallic materials (e.g., concrete,
grout, plastic, fiberglass), or combinations of materials (e.g.,
concrete filled fiberglass tube, plastic filled steel tube) that
exhibit a stiffness modulus greater than that of the matrix
soil.
[0031] The presently disclosed soil reinforcement system that
includes angled reinforcement elements provides certain advantages
over conventional prior art reinforcing methods, such as vertical
reinforcing methods. Namely, the presently disclosed soil
reinforcement system provides a more efficient mechanism for
resisting shear forces than, for example, vertical reinforcing
methods, by transferring applied shear forces in the angled
reinforcement element into axial compressive and tensile forces
that act along the axis of the angled reinforcement element.
[0032] Generally, the presently disclosed soil reinforcement system
employs angled reinforcement elements that are inserted into the
ground to absorb and/or resist seismic shear forces. Each of the
angled reinforcement elements has a stiffness modulus that is
greater than the stiffness modulus of the soil that it reinforces.
During seismic shaking, each of the angled reinforcement elements
acts in compression or tension to resist the ground motions. This
causes a reduction in the shear stress demand applied to the matrix
soil, which, in turn, reduces soil liquefaction potential.
[0033] FIG. 1 and FIG. 2 illustrate a side view and top down view,
respectively, of an example of a soil reinforcement system 100 that
includes an arrangement of angled reinforcement elements 110 for
absorbing earthquake-induced seismic shear forces. The angled
reinforcement elements 110 of soil reinforcement system 100 are
installed across an area of matrix soil 150, which is the ground.
Matrix soil 150 can include, for example, any type or types of
soil, any type or types of rock, or any combinations of any type or
types of soil and rock and in any proportions.
[0034] The angled reinforcement elements 110 are formed, for
example, of metallic materials (e.g., steel, cast iron, aluminum,),
non-metallic materials (e.g., concrete, grout, plastic, fiberglass,
wood), or combinations of materials (e.g., concrete filled
fiberglass tube, plastic filled steel tube) that exhibit a
stiffness modulus greater than that of the matrix soil 150. The
angled reinforcement elements 110 may be inserted by drilling,
driving, or other means. Examples of angled reinforcement elements
110 are shown and described with reference to FIG. 3 through FIG.
18.
[0035] The soil reinforcement system 100 can include any number and
arrangement of angled reinforcement elements 110 as long as the
goal of absorbing and/or resisting earthquake-induced seismic shear
forces for reducing soil liquefaction potential is substantially
achieved. Namely, the angled reinforcement elements 110 can be
arranged in any random or non-random pattern that is useful for
absorbing and/or resisting earthquake-induced seismic shear
forces.
[0036] Wherein conventional prior art vertical (non-angled)
elements, such as driven pilings or drilled shafts, may be used to
reduce seismic shearing stresses within the matrix soil, a
limitation of the use of vertical elements is that if they are
sufficiently slender, they resist a significant portion of the
applied shear stresses by bending, a mechanism that results in less
reduction of shear stresses within the reinforced matrix soil. This
mechanism thus may significantly reduce the ability of the vertical
elements to reduce soil liquefaction potential. It is the intent of
the presently disclosed soil reinforcement system 100, which
includes angled reinforcement elements 110, to overcome this
limitation.
[0037] In one example, the soil reinforcement system 100 includes
an array or grid of angled reinforcement elements 110 installed in
matrix soil 150. The array or grid of angled reinforcement elements
110 can include any number of rows and columns, wherein each row
and column can include any number of angled reinforcement elements
110. In the example shown in FIG. 1 and FIG. 2, soil reinforcement
system 100 includes a 25.times.25 array of angled reinforcement
elements 110 installed in matrix soil 150, wherein FIG. 1 shows one
row (or line) of the 25.times.25 array of angled reinforcement
elements 110. The presence of any arrangement of angled
reinforcement elements 110 in the matrix soil 150 creates a
reinforced zone 115 in the matrix soil 150. Although not shown in
FIG. 1, a second array of reinforcement elements that is orthogonal
or transverse to the first array may also be installed to resist
earthquake movement from other directions.
[0038] One row of the angled reinforcement elements 110 is
installed to reinforce a zone of width w1 generally from the
proximal end of the first angled reinforcement element 110 to the
proximal end of the last angled reinforcement element 110, as shown
in FIG. 1 and FIG. 2. Additionally, one column of the angled
reinforcement elements 110 is installed to reinforce a zone of
width w2 generally from the proximal end of the first angled
reinforcement element 110 to the proximal end of the last angled
reinforcement element 110, as shown in FIG. 2.
[0039] The rows of angled reinforcement elements 110 are installed
at a spacing s1. Spacing s1 can be constant or variable along the
rows of angled reinforcement elements 110. The columns of angled
reinforcement elements 110 are installed at a spacing s2. Spacing
s2 can be constant or variable along the columns of angled
reinforcement elements 110. Spacing s1 and spacing s2 can be the
same or different. In one example, both the spacing s1 and spacing
s2 are a substantially constant spacing of about 10 feet.
[0040] Additionally, each of the angled reinforcement elements 110
has a length L.sub.ARE (see FIG. 3) and a diameter D.sub.ARE (see
FIG. 3). Further, the angled reinforcement elements 110 are
installed at an angle .theta. with respect to a surface 155 of the
matrix soil 150 and to a depth dl into the matrix soil 150. For a
certain length L.sub.ARE, the depth dl of the angled reinforcement
elements 110 and the lateral extent Lx of the angled reinforcing
elements will depend on the angle .theta..
[0041] The depth dl of the array of angled reinforcement elements
110 is selected based on the in-situ liquefaction susceptibility of
the matrix soil 150 and the consequences of liquefaction at a given
depth profile. The depth dl of the angled reinforcement element 110
typically can be from about 10 feet to about 70 feet, or is about
40 feet in one example.
[0042] The spacing s1 and spacing s2 and the diameter D.sub.ARE of
the angled reinforcement elements 110 are selected so that the
transfer of the seismic shear stresses to the angled reinforcement
elements 110 is sufficient to reduce the stresses in the soil in
order to mitigate or reduce the triggering of liquefaction. The
spacing s1 and spacing s2 of the angled reinforcement element 110
typically can be from about 4 feet to about 30 feet, or is about 10
feet in one example. The diameter D.sub.ARE of the angled
reinforcement element 110 typically can be from about 2 inches to
about 24 inches, or is about 12 inches in one example. The length
L.sub.ARE of the angled reinforcement element 110 typically can be
from about 15 feet to about 100 feet, or is about 57 feet in one
example.
[0043] The angle .theta. of angled reinforcement elements 110 is
selected based on both installation and load transfer efficiency
criteria. The angle .theta. of the angled reinforcement element 110
typically can be from about 45 degrees to about 80 degrees, and is
about 45 degrees in one example.
[0044] By way of example, FIG. 3 shows one angled reinforcement
element 110. In this example, if the angle .theta. of the angled
reinforcement element 110 is about 45 degrees, in order to provide
a depth dl of about 40 feet and a lateral extent Lx (for a single
angled reinforcement element 110) of about 40 feet, then the length
L.sub.ARE of the angled reinforcement element 110 must be about
56.6 feet. If the 25.times.25 array of angled reinforcement
elements 110 shown in FIG. 2 is installed in matrix soil 150
according to FIG. 3 and if spacing s1 and spacing s2 are both about
10 feet, then the width w1 of the reinforced zone 115 is about 240
feet and the width w2 of the reinforced zone 115 is about 240
feet.
[0045] FIG. 4 through FIG. 13 show and describe three examples of
angled reinforcement elements 110 and respective methods of forming
the three examples of angled reinforcement elements 110. However,
the presently disclosed angled reinforcement elements 110 are not
limited to these three examples only.
[0046] In one embodiment and referring now to FIG. 4 and FIG. 5,
the angled reinforcement element 110 may consist of concrete-filled
or grout-filled shafts that are formed in the ground. For example,
FIG. 4 shows a mandrel 410 that is driven or pushed into the matrix
soil 150 to form an elongated hold or cavity (or shaft). The
mandrel 410 is typically hollow (but typically with a removable
closed end driving cap, for example, which can be valved or
sacrificial) and forms a hollow channel or shaft in the matrix soil
150. Then, the mandrel 410 is filled with a flowable material 415.
The flowable material 415 can be, for example, concrete or grout.
Once the mandrel 410 is filled (or during filling), but before the
flowable material 415 is cured to a hardened state, the mandrel 410
is extracted from the matrix soil 150, leaving behind an angled
channel or column of, for example, concrete or grout in the matrix
soil 150, as shown in FIG. 5. Namely, FIG. 5 shows the resulting
angled reinforcement element 110 (minus the mandrel 410), which is
formed of the cured flowable material 415. In another example,
instead of using the hollow mandrel 410, an angled hole or cavity
(or shaft) can be drilled in the matrix soil 150 using a
hollow-flight or solid-flight auger and the angled hole is then
filled with the flowable material 415. Optionally and referring now
to FIG. 6, before the flowable material 415 is cured, steel
reinforcing rods 420 may be installed in the flowable material 415.
The presence of steel reinforcing rods 420 allows the resulting
angled reinforcement element 110 to better resist both compressive
and tensile loads.
[0047] FIG. 7 shows a flow diagram of an example of a method 700 of
forming and installing the angled reinforcement element 110 that is
shown and described with reference to FIG. 4, FIG. 5, and FIG. 6.
Whereas method 700 describes a method of forming one angled
reinforcement element 110, the soil reinforcement system 100 is
formed by repeating method 700 for each of the multiple angled
reinforcement elements 110 in the soil reinforcement system 100.
Method 700 may include, but is not limited to, the following
steps.
[0048] At a step 710, the flowable material from which the angled
reinforcement element 110 is to be formed is selected and prepared.
In one example and referring now to FIG. 4, the flowable material
415 can be, for example, concrete or grout. If concrete is
selected, then the concrete is prepared. If grout is selected, then
the grout is prepared.
[0049] At a step 715, at any desired angle .theta., an elongated
shaft is formed in the ground according to the desired element
length L.sub.ARE and element diameter D.sub.ARE. In one example and
referring again to FIG. 4, the mandrel 410 is driven into the
matrix soil 150 to form the elongated shaft. The size of the
mandrel 410 depends on the desired element length L.sub.ARE and the
desired element diameter D.sub.ARE. In one example, the mandrel 410
is about 50 feet long, has a diameter of about 1 foot, and is
driven into the matrix soil 150 at about a 45-degree angle. In
another example, such as in cohesive soils, instead of using the
mandrel 410, a hole is drilled in the matrix soil 150. In one
example, the hole is about 50 feet long, has a diameter of about 1
foot, and is drilled into the matrix soil 150 at about a 45-degree
angle.
[0050] At a step 720, the elongated shaft is filled with the
flowable material selected in step 710. In one example, the mandrel
410 is filled with the flowable material 415, such as concrete or
grout, and then the mandrel 410 is extracted from the matrix soil
150 (or the mandrel is extracted while the flowable material is
filled), leaving behind a channel or column of concrete or grout in
the matrix soil 150, as shown in FIG. 5. In another example (e.g.,
drilling), the hole is filled with the flowable material 415, such
as concrete or grout, to form the angled channel or column of
concrete or grout in the matrix soil 150.
[0051] At an optional step 725, reinforcing rods are installed in
the elongated shaft. For example, before the flowable material 415
is cured, steel reinforcing rods 420 may be installed in the
flowable material 415, as shown in FIG. 6.
[0052] In yet another embodiment and referring now to FIG. 8 and
FIG. 9, the angled reinforcement element 110 may consist of a
hollow tube 810 comprised of, for example, concrete, steel,
aluminum, plastic, fiberglass, composite materials, or any
combinations thereof. Optionally, the hollow tube exhibits
properties that allow it to resist applied tensile loads. The
hollow tube typically has a closed end (pointed or otherwise) on
one end for driving. The hollow tube 810 is driven into the matrix
soil 150 and then filled with a flowable material 815. Examples of
flowable material 815 include, but are not limited to, concrete;
grout; granular materials, such as gravel, aggregate, sand,
recycled concrete, crushed glass, or other flowable materials; and
any combinations thereof. Granular infill materials may be
compacted in place using a compaction device (not shown) to
increase their density and the composite stiffness of the angled
reinforcement element 110. Optionally, steel reinforcing rods, such
as the steel reinforcing rods 420 shown in FIG. 6, may be installed
in the flowable material 815. Additionally, flowable material 815
can include materials with high permeabilities that facilitate the
drainage of excess pore water pressures during and after seismic
events.
[0053] FIG. 10 shows a flow diagram of an example of a method 1000
of forming and installing the angled reinforcement element 110 that
is shown and described with reference to FIG. 8 and FIG. 9. Whereas
method 1000 describes a method of forming one angled reinforcement
element 110, the soil reinforcement system 100 is formed by
repeating method 1000 for each of the multiple angled reinforcement
elements 110 in the soil reinforcement system 100. Method 1000 may
include, but is not limited to, the following steps.
[0054] At a step 1010, the flowable material from which the angled
reinforcement element 110 is to be formed is selected and prepared.
Referring now to FIG. 8, the flowable material 815 can be, for
example, concrete; grout; granular materials, such as gravel,
aggregate, sand, recycled concrete, crushed glass, or other
flowable materials; and any combinations thereof. If concrete or
grout is selected, then the concrete or grout is prepared. If
granular materials are selected, then the granular materials are
prepared.
[0055] At a step 1015, an elongated shaft is formed in ground to
any desired depth dl and diameter D.sub.ARE and at any desired
angle .theta.. In one example, a hole is drilled in the matrix soil
150. For example, a 1-foot diameter hole is drilled in the matrix
soil 150 at about a 45-degree angle and to a depth dl of about 40
feet. It is understood that this step may be optional if the hollow
tube 810 can be driven in to the matrix soil 150 without the pilot
shaft being needed.
[0056] At a step 1020, a hollow casing or tube is driven or pushed
into the shaft in the matrix soil 150. For example and referring to
FIG. 8 and FIG. 9, hollow tube 810 is driven or pushed into the
shaft in the matrix soil 150. The hollow tube 810 can be formed,
for example, of concrete, steel, aluminum, plastic, fiberglass,
composite materials, or any combinations thereof.
[0057] At a step 1025, the elongated hollow casing or tube is
filled with the flowable material selected in step 1010. In one
example, the hollow tube 810 is filled with the flowable material
815, such as concrete; grout; granular materials, such as gravel,
aggregate, sand, recycled concrete, crushed glass, or other
flowable materials; and any combinations thereof, as shown in FIG.
8 and FIG. 9.
[0058] At an optional step 1030, reinforcing rods are installed in
the hollow casing or tube. For example, before the flowable
material 815 is cured, steel reinforcing rods 420 (see FIG. 6) may
be installed in the flowable material 815.
[0059] While FIG. 4 through FIG. 10 describe examples of angled
reinforcement elements 110 that are formed directly within the
matrix soil 150, FIG. 11, FIG. 12, and FIG. 13 describe an example
of an angled reinforcement element 110 that is formed separately
outside of the matrix soil 150 and then installed into the matrix
soil 150.
[0060] In another embodiment and referring now to FIG. 11 and FIG.
12, the angled reinforcement element 110 may consist of an
elongated solid and rigid element that can be driven or pushed into
the matrix soil 150 using, for example, piling equipment (not
shown). In particular, the material that is used to form the solid
and rigid angled reinforcement element 110 has a material stiffness
value greater than that of the matrix soil 150. Examples of such
materials include, but are not limited to, steel, concrete,
fiberglass, wood piling, plastic, composite materials, and any
combinations thereof. The reinforcement element 110 embodiment as
shown in FIG. 12 is circular in cross-section (such as a pointed
cylinder), but it is understood that a variety of cross-sections
may be used such as, for example, square, rectangle, T-shaped,
X-shaped, or cross-shaped.
[0061] FIG. 13 shows a flow diagram of an example of a method 1300
of forming and installing the angled reinforcement element 110 that
is shown and described with reference to FIG. 11 and FIG. 12.
Whereas method 1300 describes a method of forming one angled
reinforcement element 110, the soil reinforcement system 100 is
formed by repeating method 1300 for each of the multiple angled
reinforcement elements 110 in the soil reinforcement system 100.
Method 1300 may include, but is not limited to, the following
steps.
[0062] At a step 1310, an elongated, solid, rigid element is formed
according to the desired length L.sub.ARE and diameter D.sub.ARE of
the angled reinforcement element 110. For example, the elongated,
solid, rigid element can be formed of steel, concrete, fiberglass,
wood piling, plastic, composite materials, and any combinations
thereof to create an angled reinforcement element 110. In one
example, the resulting elongated, solid, rigid angled reinforcement
element 110 is about 50 feet long and has a diameter of about 1
foot.
[0063] At a step 1315, at any desired angle .theta., the elongated,
solid, rigid element is driven or pushed into the matrix soil 150.
For example, the resulting elongated, solid, rigid angled
reinforcement element 110 is driven or pushed into the matrix soil
150 using piling equipment (not shown).
[0064] During seismic events, shear stresses are transmitted from
bedrock upwards through the soil profile. When seismic shear
stresses are applied to saturated loose deposits of sand, silt, and
low plasticity clay, the soil particles have a tendency to contract
(move towards each other) and the water that exists in the pore
spaces becomes pressurized. As the pore water pressure increases,
the effective stress in the soil decreases resulting in reduction
of soil shear strength. With time, the elevated pore water pressure
causes the pore water to vent, which results in seismically-induced
settlement. It is the intent of the presently disclosed soil
reinforcement system 100 to reduce the magnitude of the peak shear
forces applied to the soil at a given elevation within the
reinforced zone 115 (see FIG. 1 and FIG. 2) by transferring these
shear forces to the angled reinforcement elements 110.
[0065] Shear forces applied to heterogeneous materials de-aggregate
into component shear forces where the magnitudes of the component
shear forces depend on the relative stiffnesses and areas of the
heterogeneous components. Referring to FIG. 14, the shear forces
V.sub.EQ that propagate upward through the soil profile during
seismic events may be resisted in part by the shear force V.sub.S
applied to the matrix soil 150 between the angled reinforcement
elements 110 and the shear force V.sub.P applied to the angled
reinforcement elements 110. The sum of shear force V.sub.S and
shear force V.sub.P must equal shear forces V.sub.EQ to satisfy
equilibrium. The magnitudes of shear force V.sub.S and shear force
V.sub.P depend on the component area encompassed by shear force Vs
and the component area encompassed by shear force Vp and also
depends on the relative stiffness of the components. The higher the
percentage of area covered by the angled reinforcement element 110
and the higher the stiffness of the angled reinforcement element
110, the greater the magnitude of shear force V.sub.P relative to
shear force V.sub.S. It is the intent of the present invention to
decrease the magnitude of shear force V.sub.S to a level that is
insufficient to cause the matrix soil to liquefy.
[0066] The shear force V.sub.P that is applied to the angled
reinforcement element 110 is in turn resisted by the development of
axial compressive or tensile stresses within the element and by
transverse shear forces within the element. Referring to FIG. 15,
the shear force V.sub.P that is applied to the angled reinforcement
element 110 is made up of vector components transverse to, and
along the axis of element 110. Using geometry, the magnitude of
axial force P.sub.P is computed as the product of applied shear
force V.sub.P and the sine of the angle .alpha., which is the angle
of inclination. Thus, the smaller the angle .alpha., the greater
the value of axial force P.sub.P required to achieve equilibrium
with the applied load of shear force V.sub.P. The axial force
P.sub.P is, in turn, resisted by the sum of the unit tractile
forces F.sub.S that develop along the element shaft. Examples of
tractile forces F.sub.S are tractile cohesion and friction
resistance. Thus, applied shear force V.sub.P results in axial
force P.sub.P, which is resisted by the sum of the tractile forces
F.sub.S acting along its shaft. It is the intent of the present
invention to distribute applied shear loads along the shaft of the
angled reinforcement element 110.
[0067] The description above is applicable for a single shear force
to be applied to the angled reinforcement element 110. However,
earthquakes cause shear stress to propagate throughout the soil
profile resulting in a spectrum of shear stress applied at various
elevations at various times. Referring to FIG. 16, a plot 1600 is
shown of the sinusoidal shear stress distributions that may occur
within the ground at two different discrete times (e.g., time A and
time B) during a simulated earthquake. In accordance with the
simulated input motion, the shear stress distribution has a
sinusoidal shape. At time A, peak shear stresses occur at depths
with peak values occurring at depths indicated by depths 1, 2, and
3. At depths 1 and 3, the peak shear stresses Veq1 and Veq3 are
applied in the left direction. At depth 2, the peak shear stress
Veq2 is applied in the right direction. At depths midway between
depths 1 and 2 and midway between depths 2 and 3, the shear stress
is zero. At time B, the shear wave has moved up in the soil profile
such that no shear stresses are experienced at depths 1, 2, and 3.
Rather, peak shear stresses are experienced at the midway depths
between depths 1 and 2 and between depths 2 and 3. FIG. 16 shows
that the seismic stresses applied to the reinforced depth H of a
given soil profile change with time and may consist of multiple
stresses resulting in either compression or tension within the
angled reinforcement element 110.
[0068] A schematic representation of the application of two shear
forces, each acting in opposite directions, is shown in FIG. 17.
Namely, FIG. 17 illustrates the case of a rightward-acting shear
force V.sub.P1 applied to the upper portion of the angled
reinforcement element 110 and a leftward-acting shear force
V.sub.P2 applied to the lower portion of the angled reinforcement
element 110. Shear force is the product of shear stress applied
over a tributary area. In this case, the downwardly angled
compressive force P.sub.P1 is resisted by the upwardly angled
compressive force P.sub.P2 and the tractile forces represented by
the sum of tractile forces F.sub.S1 that acts to resist P.sub.P1
are negated by the tractile forces represented by the sum of
tractile forces F.sub.S2 acting to resist the upwardly angled
compressive force P.sub.P2. The net result of the load transfer
mechanisms depicted in FIG. 17 are that the angled reinforcement
element 110 internally resists the applied shear forces that act
simultaneously but in two different directions on the soil profile.
It is the intent of the presently disclosed soil reinforcement
system 100 to capture these applied counteracting loads to reduce
the potential for matrix soil liquefaction.
[0069] There are unlimited combinations of forces applied to the
angled reinforcement element 110 with respect to time during an
applied seismic event. Mathematical solutions can be achieved for
many combinations, however, using computer numerical simulations.
It is the intent of the presently disclosed soil reinforcement
system 100 to capture many of these counteracting modes of applied
forces.
[0070] The angled reinforcement elements 110 must exhibit a
stiffness modulus greater than the matrix soil that they are
reinforcing. Elements with a high interface friction coefficient
exhibit improved functionality compared to those with low interface
friction coefficients because of their ability to transmit applied
shear forces V.sub.P into the angled reinforcement elements 110 and
then in turn transmit these loads out of the angled reinforcement
elements 110 through the sum of tractile forces F.sub.S transferred
from the angled reinforcement elements 110 to the soil.
[0071] Referring again to FIG. 1 and FIG. 2, which shows the angled
reinforcement elements 110 arranged in an array or grid pattern, if
the angled reinforcement elements 110 are designed to resist
compressive forces only, then a second array or grid of angled
reinforcement elements 110 that are angled 180 degrees in plan view
from the first array or grid is required. Further, to resist
seismic forces that may occur orthogonal to the reinforced zone 115
shown in FIG. 1 and FIG. 2, an array or grid of angled
reinforcement elements 110 is required in the transverse direction
to that shown in FIG. 1 and FIG. 2, wherein the transverse
direction may be perpendicular or not perpendicular to the first
array or grid pattern.
Example
[0072] A numerical analysis was performed to simulate the effects
of applied earthquakes to the array or grid of angled reinforcement
elements 110 shown in FIG. 1 and FIG. 2. The numerical analysis
consisted of a two-dimensional plane strain model created using the
software SAP 2000. The model included the following features: (a)
the matrix soil 150 and angled reinforcement element 110 respond
linearly; (b) perfect strain compatibility is developed at the
junction in between the angled reinforcement elements 110 and the
grid nodes; (c) vertical, horizontal, and rotational degrees of
freedom of nodes along the left and right lateral boundaries of the
finite element mesh shown in FIG. 1 displace equally; and (d) the
Corralitos station acceleration time history recorded during the
Loma Prieta earthquake, which has a peak ground acceleration of
0.48 g.
[0073] The angled reinforcement elements 110 were modeled as
one-foot diameter frame elements as available in the SAP program.
The frame elements develop moments, shear, and axial forces when
loaded. The modulus of elasticity for the piles was varied during
the investigation. Energy dissipation for the elastic model is
handled in SAP 2000 through Rayleigh damping. An iterative
procedure was used to introduce a damping ratio of 5% for the first
and second modes of vibration. The model included a built-in
algorithm which extrapolates damping for higher modes. A check of
the damping coefficients was made by comparing: a) the fundamental
period of vibration (T) obtained from SAP 2000 to b) that
calculated using closed form equations.
[0074] The results of the numerical studies for the angled
reinforcement elements 110 are shown in FIG. 18. Namely, FIG. 18
shows a plot 1800 of the normalized shear stress vs. normalized
depth for angled reinforcement elements 110 on a grid spacing of 10
ft.times.10 ft. The results are shown in terms of the normalized
shear stresses computed at points along a vertical section through
the center of the finite element mesh shown in FIG. 1 for a given
soil elastic modulus value, E.sub.soil, where the normalized shear
stress is defined as the maximum shear stress in the matrix soil
computed by analyses containing inclined elements normalized by the
maximum shear stress in the matrix soil computed by analyses that
do not contain inclined elements.
[0075] Lower values of normalized shear stress indicate greater
effectiveness of the angled reinforcement elements 110 in resisting
applied shear stresses and forces. FIG. 18 shows plots of the
normalized shear stress vs. normalized depth for angled
reinforcement elements 110 for a grid spacing of angled
reinforcement elements 110 that are 10 feet on-center for ground
spacing. Normalized depth is the ratio of the depth from the ground
surface in the model to the depth of the reinforced zone 115 shown
in FIG. 1 and FIG. 2. FIG. 18 shows that normalized shear stresses
computed using the model range from 0.37 to 0.95 within the upper
90 percent of the reinforced soil profile. Lower values of
normalized shear are achieved for higher E.sub.pile/E.sub.soil
ratios. This means that the stiffer the angled reinforcement
element 110 is relative to the soil, the more effective it is in
reducing the shear stresses and forces applied to the matrix soil
150.
[0076] By contrast, FIG. 19 shows the results an equivalent set of
numerical analyses applied to an array of conventional prior art
vertical (non-angled) elements (not shown); namely, elements
installed at angle .theta.=about 90 degrees. The vertical elements
are also spaced in an array 10 feet on-center for ground spacing.
Namely, FIG. 19 shows a plot 1900 of the normalized shear stress
vs. normalized depth for vertical elements on a grid spacing of 10
ft.times.10 ft. FIG. 19 shows that the vertical elements achieve
normalized stress ratios ranging from approximately 0.8 to 1.0 over
the upper 90 percent of the soil profile. The higher normalized
stress ratios relative to those shown in FIG. 18 indicate less
effectiveness at resisting applied shear stresses.
[0077] Comparing the results shown in plot 1800 of FIG. 18 to those
shown in plot 1900 of FIG. 19 for an E.sub.pile to E.sub.soil ratio
of 400 at a normalized depth of 0.5, a normalized stress ratio of
0.52 is achieved for the angled reinforcement elements 110 and a
normalized stress ratio of 0.87 is achieved for the conventional
vertical elements. This means that the angled reinforcement
elements 110 reduce about 70% more shear force than resisted by the
conventional prior art vertical elements at the same stiffness and
same spacing. These results demonstrate the efficiency of the
presently disclosed soil reinforcement system 100 that includes the
angled reinforcement elements 110.
[0078] 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.
[0079] 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.
[0080] 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 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.
[0081] 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.
[0082] 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.
* * * * *