U.S. patent application number 13/689162 was filed with the patent office on 2013-05-30 for mechanical earth stabilizing system including reinforcing members with enhanced soil shear resistance.
This patent application is currently assigned to EarthTec International LLC. The applicant listed for this patent is EarthTec International LLC. Invention is credited to David P. McKittrick.
Application Number | 20130136544 13/689162 |
Document ID | / |
Family ID | 48467033 |
Filed Date | 2013-05-30 |
United States Patent
Application |
20130136544 |
Kind Code |
A1 |
McKittrick; David P. |
May 30, 2013 |
MECHANICAL EARTH STABILIZING SYSTEM INCLUDING REINFORCING MEMBERS
WITH ENHANCED SOIL SHEAR RESISTANCE
Abstract
A mechanical earth stabilizing system is provided that includes
at least one facing panel that retains compacted soil, and at least
one reinforcing member connected at one end to the facing element
and disposed within the retained soil. The reinforcing member is
formed from a pair of parallel, bar-shaped legs disposed in a
horizontal plane. Each of the bar-shaped legs includes a plurality
of deformations along its length to resist axial movement of the
leg through the surrounding soil. The parallel legs are spaced
apart a distance of no more than about four times the thickness of
the legs in order to synergistically increase the resistance of the
legs to axial shearing through the compacted soil. The legs are
preferably formed from a single length of bar-shaped material
having a U-shaped bent portion that integrally connects the legs in
parallel. Such a structure facilitates manufacture and the rounded
portion of the integrally formed U-shaped portion provides a strong
and convenient site for connecting the reinforcing member to a
facing element.
Inventors: |
McKittrick; David P.;
(Lorton, VA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EarthTec International LLC; |
Lorton |
VA |
US |
|
|
Assignee: |
EarthTec International LLC
Lorton
VA
|
Family ID: |
48467033 |
Appl. No.: |
13/689162 |
Filed: |
November 29, 2012 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61565470 |
Nov 30, 2011 |
|
|
|
Current U.S.
Class: |
405/262 |
Current CPC
Class: |
E02D 29/0233
20130101 |
Class at
Publication: |
405/262 |
International
Class: |
E02D 29/02 20060101
E02D029/02 |
Claims
1. A mechanical earth stabilizing system, comprising: at least one
facing element that retains soil; at least one reinforcing member
connected at one end to the facing element and disposed within the
reinforced soil, the reinforcing member including a pair of legs,
each of which includes a plurality of deformations along its length
that resists axial movement of the leg through the surrounding
soil, the pair of legs having mutually parallel longitudinal axes
and being disposed in a same horizontal plane, wherein the legs are
spaced apart a distance of no more than about five times the
thickness of the legs for at least a substantial portion of their
lengths.
2. The mechanical earth stabilizing system of claim 1, wherein the
legs are integrally connected together at the end connected to the
facing element.
3. The mechanical earth stabilizing system of claim 2, wherein the
legs are integrally connected together by a U-shaped member.
4. The mechanical earth stabilizing system of claim 3, wherein the
legs are formed by a single length of bar-shaped material having a
U-shaped bent portion that integrally connects the legs in
parallel.
5. The mechanical earth stabilizing system of claim 1, wherein the
deformations are protrusions that extend from the surface of the
legs at a distance of at least about 10% of the thickness of the
legs.
6. The mechanical earth stabilizing system of claim 1, wherein the
deformations are protrusions that extend from the surface of the
legs at a distance of between about 2 and 4 millimeters.
7. The mechanical earth stabilizing system of claim 1, wherein the
legs have a rounded cross-sectional shape, and the deformations are
ridges that circumscribe the outer surface of the legs at least
partway.
8. The mechanical earth stabilizing system of claim 1, wherein the
deformations are spaced along the length of the legs a distance of
not more than about 200 millimeters apart.
9. The mechanical earth stabilizing system of claim 1, wherein the
deformations are spaced along the length of the legs a distance of
not more than about twenty times the thickness of the legs.
10. The mechanical earth stabilizing system of claim 1, wherein the
deformations are crimps or bends in the legs.
11. The mechanical earth stabilizing system of claim 10, wherein
the deformations are sinusoidal bends in the legs.
12. The mechanical earth stabilizing system of claim 11, wherein
the sinusoidal bends are of uniform length and amplitude.
13. The mechanical earth stabilizing system of claim 12, wherein
the sinusoidal bends on both legs are uniformly spaced along the
longitudinal axis of each leg.
14. The mechanical earth stabilizing system of claim 3, further
comprising a connection assembly that fixedly connects the end of
the reinforcing member to the facing element, wherein the
connection assembly includes a loop member fixedly mounted to the
facing element and having a rounded section that overlaps with the
rounded portion of the U-shaped bar element.
15. The mechanical earth stabilizing system of claim 14, wherein
the connection assembly further includes a tubular linking element
disposed in the overlapping rounded portion of the U-shaped bar
element and the rounded section of the loop element.
16. The mechanical earth stabilizing system of claim 15, wherein
the connection assembly further includes a mounting element that
fixedly connects the tubular linking element to one or both of the
rounded portion of the U-shaped bar element and the rounded section
of the loop element.
17. The mechanical earth stabilizing system of claim 15, wherein
the mounting element includes at least one cotter pin.
18. The mechanical earth stabilizing system of claim 3, further
comprising a connection assembly that fixedly connects the end of
the reinforcing element to the facing element, wherein the
connection assembly includes a plate element fixedly mounted to the
facing element, and a fastener for fixedly mounting the U-shaped
bar element of the reinforcing element to the plate.
19. The mechanical earth stabilizing system of claim 18, wherein
the plate element includes an opening, and the fastener of the
connection assembly includes a bolt that extends through the
rounded portion of the U-shaped bar element and the opening of the
plate, and a nut.
20. A mechanical earth stabilizing system, comprising: at least one
facing element that retains compacted soil; at least one
reinforcing element connected at one end to the facing element and
disposed within the compacted soil, the reinforcing element
including a pair of bar-shaped legs, each of which includes a
plurality of protrusions along its length that resist axial
movement of the leg through the surrounding soil, the pair of legs
being mutually parallel and in a horizontal plane and having about
a same cross sectional area, wherein the parallel legs are spaced
apart a distance of no more than about five times the thickness of
the legs, and are connected together at the facing element by a
U-shaped element.
21. The mechanical earth stabilizing system of claim 16, wherein
the legs are formed by a single length of bar-shaped material
having a U-shaped bent portion that integrally connects the legs in
parallel.
22. The mechanical earth stabilizing system of claim 16, wherein
the legs have a rounded cross-sectional shape, and the protrusions
are ridges that circumscribe the outer surface of the legs at least
partway.
23. The mechanical earth stabilizing system of claim 18, wherein
the ridges extend from the surface of the legs at a distance of
between about 2 and 4 millimeters.
24. The mechanical earth stabilizing system of claim 16, wherein
the protrusions are spaced along the length of the legs a distance
of not more than about 200 millimeters apart.
Description
FIELD OF THE INVENTION
[0001] The present invention generally relates to a mechanical
earth stabilizing (MSE) system for forming structural components
from compacted soil reinforcing members formed from a pair of
parallel legs that are spaced apart a selected distance to
synergistically increase the resistance of the legs to axial shear
movement through the compacted soil.
BACKGROUND OF THE INVENTION
[0002] Mechanically stabilized earth (MSE) is used to build a
variety of structures such as retaining walls, bridge abutments,
and sea walls. These structures are formed from a network of soil
reinforcing members embedded in a volume of engineered frictional
backfill formed from soil that has typically been compacted to a
high percentage (>90%) of its maximum dry density. The
reinforcing members are connected at one end to a structural facing
that retains the engineered backfill. Stresses in the engineered
backfill are partially transferred to the reinforcement members by
way of frictional forces acting between the reinforcing members and
the engineered backfill, or passive resistance between protruding
surfaces on the reinforcing members and the surrounding soil, or a
combination of both, resulting in a composite structural material
of reinforced soil, the strain of which, in the working condition,
is limited by the strain in the soil reinforcing element. The
tensional forces in the reinforcing members are also partially
transferred to the structure facings, which most commonly include
precast concrete facing panels, welded wire facing forms, or
modular blocks.
[0003] A number of different types of soil reinforcing members are
known in the prior art, including steel strips, bar mats,
ladder-type reinforcements and geosynthetic sheets, grids and
strips. Ideally, the soil-reinforcing members should carry the
tensile loads applied to them by the surrounding compressed soil in
a uniform manner along their lengths. In order for the forces in
the soil to be transferred to the reinforcement, the reinforcing
member must effectively engage the surrounding soil along its
length through friction, or bearing resistance on protrusions, or a
combination of both mechanisms. The ability of soil reinforcing
elements to engage the surrounding soil is commonly referred to by
practitioners in the art as "pull out resistance." Ladder-type
reinforcements, usually made of steel, are commonly formed by
welding cross bars at regular intervals to parallel steel bars. The
cross bars on this type of reinforcement are particularly good at
providing pullout resistance. However, ladder-type reinforcements
are relatively expensive to produce in view of the welding required
in mounting the large number of cross bars. The cross bars also add
significantly to the unit weight of the reinforcing member,
increasing the cost of transportation and installation. Finally,
the welds may make ladder-type reinforcing members more susceptible
to accelerated corrosion in service.
[0004] While steel strip-type reinforcements are easier and less
expensive to manufacture, they typically provide less resistance to
shearing through the soil than do ladder-type reinforcements even
when manufactured with ribs or other types of protrusions to
enhance soil engagement. Moreover, the applicant has observed that
reinforcing members that are wider than they are thick require a
greater weight of steel per unit of tensile strength, since a loss
of thickness due to corrosion (generally on the order of 1.5 mm to
2 mm) is assumed to occur over the design life of the structure.
Additionally, narrow relatively flat reinforcements also suffer
from the need to create a penetration at the connection with
facings to accommodate a connection member, commonly a bolt, which
in turn reduces its structural capacity at the location of the
penetration.
[0005] Accordingly there is a need in the field of MSE for a soil
stabilization system having reinforcing members that generate a
high resistance to pullout, are relatively simple and easy to
manufacture, provide maximum tensile strength with a minimum amount
of material, maintain full strength at the connection with the
facing, and maintain structural efficiency in tension over the
design life of the resulting MSE structure.
SUMMARY OF THE INVENTION
[0006] The present invention solves or at least ameliorates all of
the aforementioned shortcomings associated with the prior art. To
this end, the mechanical earth stabilizing system comprises at
least one facing element that retains compacted soil, and a
plurality of reinforcing members connected at one end to the facing
element and disposed within the retained soil, the reinforcing
member including a pair of legs, each of which includes a plurality
of deformations along its length that generate passive resistance
to sliding through the soil. The longitudinal axes of the legs are
mutually parallel and preferably disposed in a same horizontal
plane. Preferably, the legs are spaced apart a distance of no more
than about four or five times the thickness of the legs. The
applicant has surprisingly found that such spacing synergistically
increases the resistance of the legs to shearing through the
compacted soil. Stated differently, the total amount of shear
resistance for both legs when such spacing is present is greater
than the sum of the shear resistance of the individual legs when
such spacing is not present.
[0007] The legs are preferably formed from a continuous bar-shaped
member and formed into a U-shaped configuration, with the U-shaped
bend connected to the facing element. Such a structure facilitates
manufacture and the rounded portion of the integrally formed
U-shaped portion provides a strong and convenient site for
connecting the reinforcing member to a facing element.
Alternatively, the legs may be independent elements connected to a
separate facing connection apparatus.
[0008] The legs have a same or substantially same cross-sectional
shape which is preferably round or oval, but which could be square
or hexagonal or any other regular polygon, the only constraint
being that the legs are not substantially flat. The deformations
along the length of the legs may be protrusions such as ribs or
ridges which circumscribe the outer surface of the legs.
Alternatively, the deformations may take the form of crimps or
bends in the legs, such as an undulating pattern of sinusoidal
bends in the legs. In order to effectively engage the surrounding
soil, the deformations should have a regular pattern and be spaced
at regular intervals of not more than about 200 mm. If the
deformations are protrusions, then they preferably protrude between
about 2 and 4 mm.
[0009] The present invention further includes a connection assembly
that fixedly connects the reinforcing member to the facing element.
One embodiment of the connection assembly includes a loop member
fixedly mounted to the facing element and having a rounded section
that overlaps with the rounded portion of the U-shaped bar element.
A tubular linking element is disposed in the overlapping rounded
portion of the U-shaped bar element and the rounded section of the
loop element. The tubular linking element is secured to the rounded
section of the loop element and the rounded portion of the U-shaped
bar element by opposing cotter pins. Another embodiment of the
connection assembly includes a mounting plate that projects from
the face of the facing element and that overlaps with the rounded
portion of the U-shaped bar element. A bolt in combination with a
thick washer, nut, and clamping plate clamps the U-shaped bar
element to the mounting plate extending from the facing
element.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate several
embodiments of the invention and, together with the written
description, serve to explain various principles of the
invention.
[0011] FIG. 1 is a cross sectional view of a typical MSE structure
that the system of the invention may be applied to.
[0012] FIG. 2 is a partial isometric view of the MSE system of the
invention that includes an enlarged view of the connections between
the reinforcing elements and the facing panels.
[0013] FIG. 3 is a plan view of a single reinforcement member and a
first embodiment of a connecting assembly that connects the
U-shaped end of the reinforcing member to the loop connector of a
facing element.
[0014] FIG. 4 is a side view of the single reinforcement member and
a first embodiment of a connecting assembly shown in FIG. 3.
[0015] FIG. 5A is an enlarged side view of the tubular linking
element and cotter pins used in the connection assembly shown in
FIGS. 3 and 4.
[0016] FIG. 5B is a plan view of the tubular linking element
illustrated in FIG. 5.
[0017] FIG. 6 is an enlarged side view of one of the parallel legs
of the reinforcing members, illustrating the soil-engaging
deformations in the legs.
[0018] FIGS. 7 and 8 are side and plan views, respectively, of a
single reinforcement member and a second embodiment of a connecting
assembly that connects the U-shaped end of the reinforcing member
to a plate connector of a facing element.
[0019] FIG. 9 is the plan view of FIG. 8 with the bolt removed to
illustrate the washer used in the connection assembly illustrated
in FIG. 7 and FIG. 8.
[0020] FIG. 10 is a partial isometric view of the MSE system of the
invention that uses the second embodiment of the connecting
assembly including an enlarged view of the connections between the
reinforcing elements and the facing panels.
[0021] FIG. 11 illustrates how the spacing of the parallel legs of
the reinforcing members generates synergism in the ability of the
reinforcing member to engage with the surrounding compacted
soil.
[0022] FIG. 12 is a plan view of an alternate embodiment of the
invention wherein the deformations are an undulating pattern of
sinusoidal bends in the legs.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] Reference will now be made in detail to various exemplary
embodiments of the invention, examples of which are illustrated in
the accompanying drawings. The following detailed description is
provided to give details on certain embodiments of the invention,
and should not be understood as a limitation on the full scope of
the invention.
[0024] FIG. 1 illustrates the principal components of the MSE
system 100 of the invention. This system 100 includes facing
elements 102 which in this example are pre-cast concrete wall
panels, a network of horizontally-oriented soil reinforcing members
104, and connecting assemblies 106 that affix the free ends of the
reinforcing members 104 to the facing elements 102. While not
specifically shown in FIG. 1, the other ends of the reinforcing
elements 104 are secured into or on the structural member 107
opposite the facing elements 102. The facing elements 102 retain a
volume of engineered backfill, which in this example is soil 108
that has been compacted to about 95% of its maximum potential dry
density. The compacted soil 108 forms a solid matrix of material
around the network of reinforcing members 104. Mechanical
engagement between the reinforcing members 104 and the compacted,
surrounding soil 108 caused by friction and passive resistance
between the soil 108 and protrusions on the members 104 forms a
composite structural material of reinforced soil. Accordingly,
lateral deformation of the reinforced compacted soil 108 in
response to gravity and externally applied loads is resisted by the
tensile strength of the reinforcing members 104 in combination with
the compressive capacity of the reinforced soil structure.
[0025] The ability of the MSE structure formed by the system 100 to
carry a load is dependent upon the ability of the reinforcing
members to generate pullout resistance 108 and to withstand tensile
loads. So, if the soil easily shears between the reinforcing
members 104 and surrounding soil 108, it will pull out of the soil
long before reaching the tensile capacity of the element. While
pullout resistance may be increased by increasing the number of
reinforcing members in the system 100, such a solution would
require substantial increase in material and labor. Accordingly,
the reinforcing members 104 are designed to provide a high degree
pullout resistance.
[0026] With reference now to FIGS. 2 and 3, each of the
reinforcement members 104 includes a pair of bar-shaped, parallel
legs 110a, 110b oriented in a horizontal plane as shown. While each
of the legs has a generally round cross-sectional shape in this
example of the invention to facilitate manufacture, cross-sectional
shapes that are ovular, square, or any type of regular polygon are
within the scope of the invention. Preferably, the cross-sectional
shape is not substantially longer than it is wide (as would be the
case if the legs 110a, 110b were substantially flat) so that the
reinforcing members 104 will maintain their strength over the
expected lifetime of the resulting MSE structure despite a 1.0 to
1.5 mm loss in material over all exposed surfaces of the legs due
to corrosion. In this application, the "thickness" of the legs
110a, 110b refers to the average distance across their non-deformed
cross-section. Accordingly, "thickness" corresponds to diameter in
the case of legs 110a, 110b having round cross-sections. In the
preferred embodiment, the legs 110a, 110b range from between about
5 and 25 mm in thickness and more preferably between about 9 mm and
20 mm in thickness. The legs 110a, 110b are preferably of the same
thickness to facilitate manufacture. While the outer surface of bar
material used to form the legs 110a, 110b may be smooth, it
preferably carries a base texture such as that rolled into concrete
reinforcing bars in order to increase frictional engagement between
the legs 110a, 110b formed thereby and the surrounding soil
108.
[0027] With reference to FIGS. 2, 3 and 6, in order to enhance the
engagement of the legs 110a, 110b and the surrounding compacted
soil 108, each of the legs 110a, 110b includes a plurality of
deformations which in this example are a series of annular ribs 112
that completely circumscribe the legs 110a, 110b. In order to
ensure a high degree of soil engagement, the outer edges 114 of
each of the annular ribs 112 should radially extend between about 2
and 4 mm from the surface of the legs. Additionally, there should
be at least one rib 112 every 200 mm length of the legs 110a, 110b.
Preferably the annular ribs 112 are integrally formed around the
bar-like legs 110a, 110b by a hot rolling or cold drawing process
of the type well known in the prior art.
[0028] With reference again to FIGS. 2 and 3, the legs 110a, 110b
of each reinforcing member 104 are preferably integrally connected
at one end by a U-shaped bent portion 116 having a rounded portion
118. The rounded portion 118 provides a convenient and strong means
to interconnect the free ends of the reinforcing members 104 to the
facing elements 102 via the connecting assemblies 106, as will be
described in detail hereinafter. One preferred method of forming
the reinforcing members 104 of the system 100 is to bend a single
bar-shaped member in "hairpin" fashion to form two leg members
110a, 110b of equal length and thickness that are integrally
connected via a U-shaped bent portion. Such a method is easy to
implement, and creates an integral U-shaped portion without the
need for welding. However the invention is not confined to such a
manufacturing method or the particular embodiment of the
reinforcing member formed thereby.
[0029] With reference now to FIGS. 3-5B, a first embodiment 106 of
the connection assembly of the invention includes upper and lower
anchor loops 122a, 122b, a tubular linking member 128, and a pair
of cotter pins 130a, 130b. The anchor loops 122a, 122b are formed
from bar stock, preferably plain round reinforcing steel, that
includes an end portion 124a, a 90.degree. bend extending the bar
perpendicular to the facing element, a curved section 126 having an
inner, semi-circular shape that is about the same size as the
inner, semi-circular shape as the U-shaped bent portions 116 of the
reinforcing members 104, a return elongated leg equal in length to
the first, a 90.degree. bend in the opposite direction of the
first, and another end portion 124b which is approximately equal in
length to the first end portion 124a. The end portions 124a, 124b
are directly cast within the precast concrete panel forming the
facing element 102, although any form of attachment of the anchor
loops 122a, 122b to the facing element 102 is within the scope of
the invention. The anchor loops 122a, 122b are spaced vertically at
a distance reasonably close to, but not less than the maximum
thickness of the U-shaped bent portion 116 of the reinforcing
member 104. The diameter of the anchor loops 122a, 122b is sized
such that their combined cross sectional area, at the end of the
structure design life, is at least equal to, and not less than the
cross sectional area of the parallel legs 110a, 110b of the
reinforcing member 104 at the end of the structure design life.
[0030] The tubular linking element 128 has a cylindrical outer
surface that is preferably complementary in shape to the circular
opening made after the U-shaped bent portion 116 is inserted
between the curved sections 126 of the anchor loops 122a, 122b. The
tubular linking member 128 is disposed within this circular opening
as shown. To secure the bent portion 116 and the curved section 126
to the tubular linking member 128, cotter pins 130a, 130b are
slipped over the upper edge of the linking member as shown in FIG.
4. As best seen in FIG. 5, cotter pin 130a includes a single
C-shaped section 132 for receiving the distal end of the U-shaped
bent portion 116, while cotter pin 130b includes two such C-shaped
sections to receive the distal ends of the curved sections 126 of
the anchor loops 122a, 122b. The cotter pins 130a, 130b not only
securely mount the tubular linking member 128 to the U-shaped bent
portion 116 and the curved sections 126 of the anchor loops; they
also rigidly affix the linking member 128, bent portion 116 and
curved sections 126 together so that they cannot move relative to
one another along the axis of the reinforcing member 104. This is
important as any such axial, relative movement between these
components could promote undesirable shear movement between the
reinforcing members 104 and the surrounding compacted soil 108 and
thereby diminish the engagement between the reinforcing members 104
and the surrounding soil 108. The thickness of the linking member
128 is sized such that the shear capacity of the tube, at the end
of the design life of the MSE structure, is at least equal to the
tensile capacity of the reinforcing member 104.
[0031] With reference now to FIGS. 7-10, a second embodiment 135 of
the connection assembly includes a rectangular mounting plate 137
having a hole 139a, 139b at its distal and proximate ends, a steel
mounting dowel 141, a washer 143 sized to fit closely within the
U-shaped bent portion 116 of the reinforcing member, an L-shaped
clamping plate 145 having a lip portion 147 and a hole 148, and a
bolt 149 and nut of 150. The mounting dowel 141 secures the
mounting plate 137 to the pre-cast concrete panel that forms the
facing element 102. To this end, the dowel 141 is inserted through
the hole 139a at the distal end of the mounting plate 137, and both
are cast within the facing element 102 with the dowel 141
vertically oriented and the plate 137 horizontally oriented as best
seen in FIG. 7. Next, as best seen in FIG. 9, the U-shaped bent
portion 116 is aligned over the hole 139b at the end of the
mounting plate 137 that projects out of the facing element 102.
Washer 143 is then disposed within the semicircular inner periphery
of the U-shaped portion 116 of the reinforcing member such that the
opening in the center of the washer 143 is aligned with the hole
139b in the mounting plate 137. The clamping plate 145 is then
positioned over the U-shaped portion of the reinforcing member 104
with the hole 148 of the clamping plate aligned with the hole 139b
of the mounting plate 137 and the lip portion 147 overhanging the
distal end of the U-shaped portion as shown in FIGS. 7 and 8.
Finally, the shaft of the bolt 149 is inserted through the hole 148
of the clamping plate 145 and through the washer 143, and the nut
150 is tightened over the threaded end of the bolt shaft. The
pressure that the bolt 149 and nut 150 applies to the clamping
plate 145 in combination with the capture of the distal end of the
U-shaped portion by the lip portion 147 fixedly connects the free
end of the reinforcing member 104 to the mounting plate 137 cast
into the facing element such that the reinforcing member 104 cannot
move axially with respect to the facing element 102. The shear
capacity of the both the mounting plate 137 and the bolt 149 at the
end of the design life of the resulting MSE structure must at least
equal to, but not less than the tensile capacity of the reinforcing
member 104.
[0032] While the facing elements 102 have been described as
pre-cast concrete wall panels in the descriptions of both
connecting assembly embodiments 106, 135 they may just as easily be
cast-in-place panels or blocks or welded wire the facings.
[0033] FIG. 11 illustrates what the applicant believes is the
synergistic mechanism behind the enhanced resistance to axial shear
movement between the reinforcing members 104 and the surrounding
compacted soil 108. As previously stated, the legs 110a, 110b of
the reinforcing members are preferably spaced apart a distance D of
between two and five thicknesses of the legs 110a, 110b, and most
preferably a distance of about four thicknesses of the legs 110a,
110b. When tensile forces are applied to the legs 110a, 110b and
the legs attempt to move axially relative to the compacted soil
108, the friction between the outer surfaces of the legs and the
surrounding compacted soil 108, in combination with the passive
resistance between the protruding ribs 112 circumscribing the legs
110a, 110b and the surrounding compacted soil 108 creates two
interfering zones of dilation, i.e. zones where the compacted soil
is being pushed away from the legs 110a, 110b in the radial
direction. The interference between these two zones of dilation
tends to compress the soil between the two parallel legs 110a, 110b
and create a positive arching effect in the soil above and below
the legs 110a, 110b, thereby increasing both the friction between
the outer surfaces of the legs 110a, 110b and the surrounding soil
108 as well as the passive resistance between the protruding ribs
112 and the surrounding soil 108. These increased frictional and
passive resistance forces in turn impart to the reinforcing member
104 enhanced resistance to shearing through the soil.
[0034] FIG. 12 illustrates a second embodiment 200 of the invention
wherein the deformations 112 in the legs 110a, 110b are bends or
crimps in the bar-like material forming the legs. In this
particular example, such bends or crimps are a series of undulating
sinusoidal curves 112 in the legs 110a, 110b having the same
amplitude and wavelength. In one preferred embodiment, the length
of each of the sinusoidal bends 112 is between about 25 and 40 cm
The maximum distance "d1" between the legs 110a, 110b at opposing
peaks 150a, 150b peaks of adjacent bends 112 is no more than about
six diameters of one of the legs 110a, 110b and a minimum distance
"d2" between the legs is at least one diameter of one of the legs
110a, 110b. Such proportioning of the distances d1 and d2 insures
that the distance between the two legs 110a, 110b is between about
two and five leg thicknesses throughout a substantial portion of
the length of the legs 110a, 110b. Even though both of the legs
110a, 110b in the second embodiment have deformations in the form
of sinusoidal bends 112, the central axes A1, A2 of these legs
110a, 110b are parallel as shown. This second embodiment has the
advantage that the legs 110a, 110b may be formed from standard
reinforcing bar material of the type commonly used to reinforce
concrete structures. The naturally rough exterior surface of such
reinforcing bar helps enhance the frictional forces between the
legs 110a, 110b and the surrounding compressed ground fill.
[0035] The foregoing examples have been provided merely for the
purpose of explanation and are in no way to be construed as
limiting of the present invention. While the present invention has
been described with reference to exemplary embodiments, it is
understood that the words which have been used herein are words of
description and illustration, rather than words of limitation.
Changes may be made, within the purview of the appended claims, as
presently stated and as amended, without departing from the scope
and spirit of the present invention in its aspects. Although the
present invention has been described herein with reference to
particular means, materials and embodiments, the present invention
is not intended to be limited to the particulars disclosed herein;
rather, the present invention extends to all functionally
equivalent structures, methods and uses, such as are within the
scope of the appended claims.
* * * * *