U.S. patent application number 10/599558 was filed with the patent office on 2008-10-30 for reinforced soil retaining wall system and method of construction.
This patent application is currently assigned to MODALCO PTY LTD. Invention is credited to Samuel Patrick Costin.
Application Number | 20080267718 10/599558 |
Document ID | / |
Family ID | 35063821 |
Filed Date | 2008-10-30 |
United States Patent
Application |
20080267718 |
Kind Code |
A1 |
Costin; Samuel Patrick |
October 30, 2008 |
Reinforced Soil Retaining Wall System and Method of
Construction
Abstract
A reinforced soil retaining wall system (10) in which a
plurality of blocks (12) are arranged in courses (14) to form a
wall (16). Soil reinforcement is provided to the wall (16) using a
plurality of lengths of strip reinforcement (18) inserted in and
extending from the blocks (12), the strip reinforcement (18) being
buried under compacted backfill (20) either as each course (14) is
laid or after construction of the wall (16). Also disclosed is the
use of a second plurality of sections of soil reinforcement, spaced
apart from the first plurality of sections and arranged to extend
perpendicular to the wall.
Inventors: |
Costin; Samuel Patrick;
(Western Australia, AU) |
Correspondence
Address: |
BROOKS KUSHMAN P.C.
1000 TOWN CENTER, TWENTY-SECOND FLOOR
SOUTHFIELD
MI
48075
US
|
Assignee: |
MODALCO PTY LTD
Quinns Rock, Western Australia
AU
|
Family ID: |
35063821 |
Appl. No.: |
10/599558 |
Filed: |
March 31, 2005 |
PCT Filed: |
March 31, 2005 |
PCT NO: |
PCT/AU2005/000474 |
371 Date: |
October 2, 2006 |
Current U.S.
Class: |
405/262 ;
405/284 |
Current CPC
Class: |
E02D 29/0233 20130101;
E02D 29/0225 20130101 |
Class at
Publication: |
405/262 ;
405/284 |
International
Class: |
E02D 29/02 20060101
E02D029/02; E02D 5/76 20060101 E02D005/76; E02D 17/20 20060101
E02D017/20 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 1, 2004 |
AU |
2004901725 |
Apr 5, 2004 |
AU |
2004901789 |
Dec 15, 2004 |
AU |
2004907121 |
Feb 23, 2005 |
AU |
2005900832 |
Claims
1. A reinforced soil retaining wall system comprising: a plurality
of blocks arranged in courses above a base course to form a wall,
the wall having a retained side and a dredge side, each block
comprising a front face oriented in use towards the dredge side of
the wall, a rear face spaced from said front face by a distance
defining the depth of said block and oriented in use towards the
retained side of the wall, a top surface, a bottom surface spaced
from said top surface by a distance defining the height of said
block, opposing side surfaces spaced from each other by a distance
defining the width of said block, and a passage extending through
at least a portion of the height of the block and terminating in a
first opening in the top or bottom surface, the passage and first
opening configured to receive a first portion of a length of strip
reinforcement; and, a plurality of lengths of strip reinforcement
for anchoring the wall, each length of strip reinforcement
insertable within at least one of the plurality of blocks such that
a first portion of the length of strip reinforcement is received
within the passage of the block, a second portion of the length of
strip reinforcement is arranged in coplanar alignment with the top
or bottom surface of the block and a third portion of the length of
strip reinforcement is arranged to extend outwardly from the rear
face of the block and secured in position substantially
perpendicular to the wall during backfilling and compaction.
2. The reinforced soil retaining wall system of claim 1 wherein the
passage is substantially vertically oriented relative to the top or
base section of the block.
3. The reinforced soil retaining wall system of claim 1 wherein
each length of strip reinforcement is resiliently flexible.
4. The reinforced soil retaining wall system of claim 1 wherein the
block further comprises a guide slot extending from the first
opening passage along the top or bottom surface of the block, the
guide slot terminating at the rear face of the block and configured
to house the second portion the length of strip reinforcement.
5. The reinforced soil retaining wall system of claim 1 wherein the
third portion of the length of strip reinforcement is arranged in
coplanar alignment with the top and or base surface of the blocks
immediately prior to backfilling and compacting.
6. The reinforced soil retaining wall system of claim 1 wherein the
passage extends through the full height of the block from a first
opening provided in the bottom surface of the block to a second
opening provided in the top surface of the block.
7. The reinforced soil retaining wall system of claim 6 wherein a
length of strip reinforcement is inserted through the passage from
the first opening to the second opening and a fourth portion of the
length of strip reinforcement is arranged to extend outwardly from
the rear face of the block to be secured in position substantially
perpendicular to the wall during backfilling and compaction.
8. The reinforced soil retaining wall system of claim 7 wherein the
fourth portion is arranged in general coplanar alignment with
respect to the top or bottom face of the block away from the wall
immediately prior to backfilling and compaction.
9. The reinforced soil retaining wall system of claim 1 wherein the
passage is a cavity extending from the bottom surface to the top
surface, the cavity configured to receive a quantity of
ballast.
10. The reinforced soil retaining wall system of claim 10 wherein
the ballast is drainage aggregate.
11. The reinforced soil retaining wall system of claim 10 wherein
the ballast is impermeable.
12. The reinforced soil retaining wall system of claim 1 wherein
the passage is one of plurality of passages.
13. The reinforced soil retaining wall system of claim 1 further
comprising one or more shear pins to resist sliding movement of a
first course over an adjacent second course.
14. The reinforced soil retaining wall system of claim 1 further
comprising a drainage channel configured to direct moisture from
the retained side of the wall towards the dredge side of the
wall.
15. The reinforced soil retaining wall system of claim 1 wherein
the plurality of lengths of strip reinforcement are divided into a
threaded section inserted into at least one block and a free
section co-operatively associated with the threaded section and
arranged to arranged to extend outwardly from the rear face of the
block and be secured in position substantially perpendicular to the
wall during backfilling and compaction.
16. The reinforced soil retaining wall system of claim 1 forming a
lower section of a composite wall, the composite wall being divided
a transition depth into an upper section and the lower section
17. The reinforced soil retaining wall system of claim 16 wherein
the upper section is a gravity retaining wall.
18. The reinforced soil retaining wall system of claim 16 further
comprising a soil reinforcement protection barrier at the
transition depth in general coplanar alignment with the top
uppermost course of blocks forming the lower section of the
composite wall.
19. The reinforced soil retaining wall system of claim 18 wherein
the soil reinforcement protection barrier is a concrete slab.
20. A method of construction of a reinforced soil retaining wall
system, the system comprising a plurality of blocks arranged in
courses above a base course to form a wall, the wall being anchored
by backfilling and compacting soil over a plurality of lengths of
strip reinforcement operatively connected to at least a portion of
the plurality of blocks laid in courses, the method of construction
comprising the steps of: a) providing a level surface for laying a
course of blocks, each block comprising a front face, a rear face
spaced from said front face by a distance defining the depth of
said block, a top surface, a bottom surface spaced from said top
surface by a distance defining the height of said block, opposing
side surfaces spaced from each other by a distance defining the
width of said block, a passage extending through at least a portion
of the height of the block and terminating in a first opening in
the top or bottom surface, the passage and first opening configured
to receive a first portion of a length of strip reinforcement; b)
inserting a length of strip reinforcement into a block to be laid
in the course such that a first portion of the length of strip
reinforcement is received in the passage, a second portion of the
length of strip reinforcement is arranged in coplanar alignment
with the top or bottom surface of the block and a third portion of
the length of strip reinforcement is arranged to extend outwardly
from the rear face of the block; c) positioning the block and the
inserted length of strip reinforcement onto the level surface such
that the rear surface of the block and the third portion of the
length of strip reinforcement is directed towards the soil to be
retained by the wall; d) repeating step (a) to (c) until a required
height for the retaining wall has been achieved; and, e) anchoring
the position of the third portion of the length of strip
reinforcement by backfilling and compacting a quantity of soil
behind the rear face of the block.
21. The method of construction of claim 20 wherein step (e) is
conducted after step (c) after each course is completed.
22. The method of construction of claim 20 wherein construction is
mortarless and each block further comprises a guide slot extending
from the first opening along the bottom surface of the block and
terminating at the rear face of the block, the guide slot being
configured to accommodate the second portion the length of strip
reinforcement.
23. The method of construction of claim 20 wherein the third
portion of the length of strip reinforcement is arranged in
coplanar alignment with the top and or base surface of the blocks
immediately prior to step (e).
24. The method of construction of claim 20 wherein the passage
extends through the full height of the block from a first opening
provided in the bottom surface of the block to a second opening
provided in the top surface of the block and step (b) comprises the
step of inserting a length of strip reinforcement through the
passage from the first opening to the second opening such that a
fourth portion of the length of strip reinforcement is arranged to
extend outwardly from the rear face of the block.
25. The method of construction of claim 24 wherein step (e) further
comprises the step of anchoring the position of the fourth portion
of the length of strip reinforcement by backfilling and compacting
a quantity of soil behind the rear face of the block.
26. The method of construction of claim 25 wherein the fourth
portion is arranged in general coplanar alignment with respect to
the top or bottom face of the block away from the wall immediately
prior to backfilling and compaction.
27. The method of construction of claim 20 wherein the passage is a
cavity extending from the bottom surface to the top surface and the
method further comprises the step of adding a quantity of ballast
to the cavity after each block or each course of blocks has been
laid.
28. The method of construction of claim 27 wherein the ballast is
drainage aggregate.
29. The method of construction of claim 27 wherein the ballast is
impermeable.
30. The method of construction of claim 20 further comprising the
step of installing one or more shear pins to resist sliding
movement of a first course over an adjacent second course.
31. The method of construction of claim 20 wherein the plurality of
lengths of strip reinforcement are divided into a threaded section
inserted into at least one block at step (b) and a free section
co-operatively associated with the threaded section and arranged to
extend outwardly from the rear face of the block and be secured in
position during step (e) substantially perpendicular to the wall
during backfilling and compaction.
32. The method of construction of claim 20 wherein the reinforced
soil retaining wall forms a lower section of a composite wall, the
composite wall being divided a transition depth into an upper
section and the lower section and the method further comprises the
step of constructing a gravity or cantilever retaining wall to form
the upper section of the composite wall.
33. The method of construction of claim 32 further comprising the
step of installing a soil reinforcement protection barrier at the
transition depth in general coplanar alignment with the, top
uppermost course of blocks forming the lower section of the
composite wall.
34. The method of construction of claim 33 wherein the step of
installing a soil reinforcement protection barrier comprises the
step of laying a concrete slab.
35. A block for use in constructing the reinforced soil retaining
wall system of claim 1.
36. A length of strip reinforcement for use in constructing the
reinforced soil retaining wall system of claim 1.
37. A reinforced soil retaining wall system comprising: a plurality
of blocks arranged in courses above a base course to form a wall,
the wall having a retained side and a dredge side, each block
comprising a front face oriented in use towards the dredge side of
the wall, a rear face spaced from said front face by a distance
defining the depth of said block and oriented in use towards the
retained side of the wall, a top surface, a bottom surface spaced
from said top surface by a distance defining the height of said
block, opposing side surfaces spaced from each other by a distance
defining the width of said block; a first plurality of sections of
soil reinforcement for anchoring the wall to the backfill, the
first plurality of sections of soil reinforcement arranged between
adjacent courses of the wall and extending outwardly from the rear
face of the blocks on the retained side of the wall; and, a second
plurality of sections of soil reinforcement for stabilizing a
quantity of backfilled and compacted soil on the retained side of
the wall, the second plurality of sections of soil reinforcement
being spaced apart from the first plurality of sections of soil
reinforcement and arranged to extend substantially perpendicular to
the wall during backfilling and compaction.
38. The reinforced soil retaining wall system of claim 37 wherein
the second plurality of sections of soil reinforcement is spaced
apart from the rear face of the wall.
39. The reinforced soil retaining wall system of claim 37 wherein
one or both of the first or second plurality of sections soil
reinforcement is/are resiliently flexible.
40. The reinforced soil retaining wall system of claim 37 wherein
the wall has a height and the plurality of second sections of soil
reinforcement have a length that is equal to at least 60% of the
height of the wall.
41. The reinforced soil retaining wall system of claim 39 wherein
the wall has a height and the plurality of second sections of soil
reinforcement have a length that is equal to at least 70% of the
height of the wall.
42. The reinforced soil retaining wall system of claim 40 wherein
the wall has a height and the plurality of second sections of soil
reinforcement have a length that is equal to at least 80% of the
height of the wall.
43. The reinforced soil retaining wall system of claim 37 wherein
the plurality of second sections of soil reinforcement have a
length that extends at least through the anticipated plane of
rupture of the backfill.
44. The reinforced soil retaining wall system of claim 37 wherein
one or both of the first or second plurality of sections of soil
reinforcement is/are planar.
45. The reinforced soil retaining wall system of claim 37 wherein
the one or both of the first or second plurality of sections of
soil reinforcement is/are geomesh.
46. The reinforced soil retaining wall system of claim 37 wherein
one or both of the first or second plurality of sections of soil
reinforcement is/are in the form of elongated strips.
47. The reinforced soil retaining wall system of claim 37 wherein
the first and second plurality of sections of soil reinforcement
are arranged in horizontal coplanar arrangement with respect to
each other.
48. The reinforced soil retaining wall system of claim 37 wherein
the first plurality of sections of soil reinforcement are arranged
in a first layer and the second plurality of sections of soil
reinforcement are arranged in a second layer offset from the first
layer.
49. The reinforced soil retaining wall system of claim 37 wherein
one or both of the first or second plurality of sections of soil
reinforcement is/are arranged in coplanar alignment with the top
and or base surface of one or more of the plurality of blocks
immediately prior to backfilling and compacting.
50. The reinforced soil retaining wall system of claim 37 wherein
the blocks further comprise one or more cavities extending from the
bottom surface to the top surface, the cavity configured to receive
a quantity of ballast.
51. The reinforced soil retaining wall system of claim 49 wherein
the ballast is drainage aggregate.
52. The reinforced soil retaining wall system of claim 50 wherein
the ballast is impermeable.
53. The reinforced soil retaining wall system of claim 37 further
comprising one or more shear pins to resist sliding movement of a
first course over an adjacent second course.
54. The reinforced soil retaining wall system of claim 37 further
comprising a drainage channel configured to direct moisture from
the retained side of the wall towards the dredge side of the
wall.
55. The reinforced soil retaining wall system of claim 37 forming a
lower section of a composite wall, the composite wall being divided
a transition depth into an upper section and the lower section.
56. The reinforced soil retaining wall system of claim 54 wherein
the upper section is a gravity retaining wall.
57. The reinforced soil retaining wall system of claim 54 further
comprising a soil reinforcement protection barrier at the
transition depth in general coplanar alignment with the top
uppermost course of blocks forming the lower section of the
composite wall.
58. The reinforced soil retaining wall system of claim 56 wherein
the soil reinforcement protection barrier is a concrete slab.
59. The reinforced soil retaining wall system of claim 37 wherein
the first plurality of sections of soil reinforcement are fixedly
held between adjacent courses of blocks using mortar.
60. The reinforced soil retaining wall system of claim 37 wherein
the first plurality of sections of soil reinforcement are fixedly
held between adjacent courses of blocks by gravity under the weight
of the blocks forming the adjacent courses.
61. A method of construction of a reinforced soil retaining wall
system, the system comprising a plurality of blocks arranged in
courses above a base course to form a wall, the method of
construction comprising the steps of: a) providing a level surface
for laying a course of blocks, each block comprising a front face,
a rear face spaced from said front face by a distance defining the
depth of said block, a top surface, a bottom surface spaced from
said top surface by a distance defining the height of said block,
opposing side surfaces spaced from each other by a distance
defining the width of said block; b) arranging a first plurality of
sections of soil reinforcement for anchoring the wall to the
backfill between adjacent courses of the wall whilst laying each
course of blocks, the first plurality of sections of soil
reinforcement being arranged to extend outwardly from the rear face
of the blocks on the retained side of the wall; c) laying each
subsequent course until a required height for the retaining wall
has been achieved; d) arranging a second plurality of sections of
soil reinforcement spaced apart from the first plurality of
sections of soil reinforcement and arranged to extend during step
(e) substantially perpendicular to the wall; and, e) backfilling
and compacting a quantity of backfill behind the rear face of the
blocks so as to anchor the position of the first and second
plurality of sections of soil reinforcement.
62. The method of construction of claim 60 wherein step (e) is
conducted after step (b) and prior to step (c).
63. The method of construction of claim 61 wherein the second
plurality of sections of soil reinforcement are arranged during
step (e) so as to be spaced apart from the rear face of the
wall.
64. The method of construction of claim 60 wherein the first and
second plurality of sections of soil reinforcement are arranged in
horizontal coplanar arrangement with respect to each other.
65. The method of construction of claim 60 wherein the first
plurality of sections of soil reinforcement are arranged in a first
layer and the second plurality of sections of soil reinforcement
are arranged in a second layer offset from the first layer.
66. The method of construction of claim 60 wherein one or both of
the first or second plurality of sections of soil reinforcement
is/are arranged in coplanar alignment with the top and or base
surface of one or more of the plurality of blocks immediately prior
to backfilling and compacting.
67. The method of construction of claim 60 wherein the blocks
further comprise one or more cavities extending from the bottom
surface to the top surface, the cavity configured to receive a
quantity of ballast and the method further comprises the step of
adding a quantity of ballast to the cavity after each block or each
course of blocks has been laid.
68. The method of construction of claim 66 wherein the ballast is
drainage aggregate.
69. The method of construction of claim 66 wherein the ballast is
impermeable.
70. The method of construction of claim 60 further comprising the
step of installing one or more shear pins to resist sliding
movement of a first course over an adjacent second course.
71. The method of construction of claim 60 wherein the reinforced
soil retaining wall forms a lower section of a composite wall, the
composite wall being divided a transition depth into an upper
section and the lower section and the method further comprises the
step of constructing a gravity or cantilever retaining wall to form
the upper section of the composite wall.
72. The method of construction of claim 70 further comprising the
step of installing a soil reinforcement protection barrier at the,
transition depth in general coplanar alignment with the top
uppermost course of blocks forming the lower section of the
composite wall.
73. The method of construction of claim 71 wherein the step of
installing a soil reinforcement protection barrier comprising the
step of laying a concrete slab.
74. The method of construction of claim 60 wherein the first
plurality of sections of soil reinforcement are fixedly held
between adjacent courses of blocks using mortar.
75. The method of construction of claim 60 wherein the first
plurality of sections of soil reinforcement are fixedly held
between adjacent courses of blocks by gravity under the weight of
the blocks forming the adjacent courses.
76. A block for use in the method of constructing a reinforced soil
retaining wall system of according to claim 60.
77. A length of strip reinforcement for use in the method of
constructing a reinforced soil retaining wall system according to
claim 60.
77.-80. (canceled)
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a reinforced soil retaining
wall system and a method of construction of a reinforced soil
retaining wall. The present invention further relates to a block
used in the construction of a reinforced soil retaining wall and a
length of strip reinforcement used in the construction of a
reinforced soil retaining wall.
[0002] The present application claims priority from Australian
provisional patent application 2004901725 filed on 1 Apr. 2004,
Australian provisional patent application 2004901789 filed on 5
Apr. 2004, Australian provisional patent application 2004907121
filed on 15 Dec. 2004 and Australian provisional patent application
2005900832 filed on 23 Feb. 2005.
BACKGROUND TO THE INVENTION
[0003] Retaining walls are defined as any wall that restrains
material on one side of a wall to maintain a difference in
elevation. Nearby slopes, driveways, buildings, and tiered walls
all represent potential loads on retaining walls. There are three
main types of retaining walls: gravity walls, cantilever walls and
reinforced soil walls. A retaining wall without soil reinforcement,
where the weight of the blocks alone provides resistance to the
load of the soil being retained, is referred to as a "gravity
wall". Gravity retaining walls cost more money to install, which
each block in the wall consisting of a mass of concrete or stone.
Gravity walls rely upon their mass weight to retain the soil.
Excavation of the soil behind a gravity wall has no effect on the
structural strength of the wall. Cantilever walls are typically
sheet pile structures which are driven into the soil and derive
their support solely through the resistance the soil provides
against rotation of the sheet pile under the weight of the soil
being retained. One type of cantilever wall comprises a horizontal
base section that is buried under the backfill with a stem section
permanently connected to and extending vertically from the base
section to form the wall. Cantilever walls rely on the weight of
the backfill on the base section to keep the wall from tipping
over.
[0004] The term "reinforced soil retaining wall" refers to a
retaining wall that incorporates substantially horizontal layers of
soil reinforcement material buried under the soil being retained by
the wall. One type of reinforced soil retaining wall comprises
reinforcement in the form of steel mesh buried within the retained
soil. The steel mesh anchors a concrete slab, steel sheet or rock
filled wire basket which acts as the facing of the retaining wall,
the facing being the structure that forms the front of the wall,
usually oriented vertical or inclined. The facing prevents the soil
from escaping from between the layers of reinforcement. Using the
methods of the background art, the soil reinforcement must be added
to all or most of the courses of blocks and some form of propping
is required to prevent the facing from moving whilst the soil is
compacted around the reinforcement.
[0005] The present invention was developed to overcome at least
some of the abovementioned problems.
[0006] It will be clearly understood that, although a number of
background art methods and/or publications are referred to herein,
this reference does not constitute an admission that any of these
methods or publications form part of the common general knowledge
in the art, in Australia or in any other country. In the summary of
the invention, the description and claims which follow, except
where the context requires otherwise due to express language or
necessary implication, the word "comprise" or variations such as
"comprises" or "comprising" is used in an inclusive sense, i.e. to
specify the presence of the stated features but not to preclude the
presence or addition of further features in various embodiments of
the invention.
SUMMARY OF THE INVENTION
[0007] According to a first aspect of the present invention there
is provided a reinforced soil retaining wall system comprising:
[0008] a plurality of blocks arranged in courses above a base
course to form a wall, the wall having a retained side and a dredge
side, each block comprising a front face oriented in use towards
the dredge side of the wall, a rear face spaced from said front
face by a distance defining the depth of said block and oriented in
use towards the retained side of the wall, a top surface, a bottom
surface spaced from said top surface by a distance defining the
height of said block, opposing side surfaces spaced from each other
by a distance defining the width of said block, and a passage
extending through at least a portion of the height of the block and
terminating in a first opening in the top or bottom surface, the
passage and first opening configured to receive a first portion of
a length of strip reinforcement; and, [0009] a plurality of lengths
of strip reinforcement for anchoring the wall, each length of strip
reinforcement insertable within at least one of the plurality of
blocks such that a first portion of the length of strip
reinforcement is received within the passage of the block, a second
portion of the length of strip reinforcement is arranged in
coplanar alignment with the top or bottom surface of the block and
a third portion of the length of strip reinforcement is arranged to
extend outwardly from the rear face of the block and secured in
position substantially perpendicular to the wall during backfilling
and compaction.
[0010] The passage may be substantially vertically oriented
relative to the top or base section of the block to maximize the
pull out forces required to remove the length of strip
reinforcement from the passage after it has been inserted.
[0011] Preferably each length of strip reinforcement is resiliently
flexible.
[0012] For mortarless construction, the blocks may further comprise
a guide slot extending from the first opening passage along the top
or bottom surface of the block, the guide slot terminating at the
rear face of the block and configured to house the second portion
the length of strip reinforcement. The third portion of the length
of strip reinforcement may be arranged in coplanar alignment with
the top and or base surface of the blocks immediately prior to
backfilling and compacting or may lie at an angle to the wall
during backfilling and compacting.
[0013] In one embodiment, the passage extends through the full
height of the block from a first opening provided in the bottom
surface of the block to a second opening provided in the top
surface of the block which allows the length of strip reinforcement
to be inserted through the passage from the first opening to the
second opening with a fourth portion of the length of strip
reinforcement arranged to extend outwardly from the rear face of
the block to be secured in position substantially perpendicular to
the wall during backfilling and compaction. The fourth portion may
be arranged in general coplanar alignment with respect to the top
or bottom face of the block away from the wall immediately prior to
backfilling and compaction to maximize resistance to pull-out
forces.
[0014] Advantageously, the passage may be a cavity extending from
the bottom surface to the top surface, the cavity configured to
receive a quantity of ballast in the form of drainage aggregate or
an impermeable material such as cast concrete or cement. The
passage may be one of plurality of passages.
[0015] In one embodiment, the system further comprises one or more
shear pins to resist sliding movement of a first course over an
adjacent second course and may further comprise a drainage channel
configured to direct moisture from the retained side of the wall
towards the dredge side of the wall. The drainage channel is
particular advantageous for use with clay soils to relieve any
buildup of hydrostatic pressure on the retained side of the
wall.
[0016] In another embodiment, the plurality of lengths of strip
reinforcement are divided into a threaded section inserted into at
least one block and a free section co-operatively associated with
the threaded section and arranged to arranged to extend outwardly
from the rear face of the block and be secured in position
substantially perpendicular to the wall during backfilling and
compaction.
[0017] In a further embodiment, the reinforced soil retaining wall
system forms a lower section of a composite wall, the composite
wall being divided a transition depth into an upper section and the
lower section. The upper section may be a gravity or cantilever
retaining wall. Using this embodiment, a soil reinforcement
protection barrier may be placed at the transition depth in general
coplanar alignment with the top uppermost course of blocks forming
the lower section of the composite wall. The soil reinforcement
protection barrier may be a concrete slab used to provide a
physical indication of the transition depth or a thin sheet of
plastic material used to provide a visual indication of the
transition depth.
[0018] According to a second aspect of the present invention there
is provided a method of construction of a reinforced soil retaining
wall system, the system comprising a plurality of blocks arranged
in courses above a base course to form a wall, the wall being
anchored by backfilling and compacting soil over a plurality of
lengths of strip reinforcement operatively connected to at least a
portion of the plurality of blocks laid in courses, the method of
construction comprising the steps of: [0019] a) providing a level
surface for laying a course of blocks, each block comprising a
front face, a rear face spaced from said front face by a distance
defining the depth of said block, a top surface, a bottom surface
spaced from said top surface by a distance defining the height of
said block, opposing side surfaces spaced from each other by a
distance defining the width of said block, a passage extending
through at least a portion of the height of the block and
terminating in a first opening in the top or bottom surface, the
passage and first opening configured to receive a first portion of
a length of strip reinforcement; [0020] b) inserting a length of
strip reinforcement into a block to be laid in the course such that
a first portion of the length of strip reinforcement is received in
the passage, a second portion of the length of strip reinforcement
is arranged in coplanar alignment with the top or bottom surface of
the block and a third portion of the length of strip reinforcement
is arranged to extend outwardly from the rear face of the block;
[0021] c) positioning the block and the inserted length of strip
reinforcement onto the level surface such that the rear surface of
the block and the third portion of the length of strip
reinforcement is directed towards the soil to be retained by the
wall; [0022] d) repeating step (a) to (c) until a required height
for the retaining wall has been achieved; and, [0023] e) anchoring
the position of the third portion of the length of strip
reinforcement by backfilling and compacting a quantity of soil
behind the rear face of the block.
[0024] Step (e) may be conducted after step (c) after each course
is completed or after the wall has been completed in a single
backfilling operation.
[0025] For mortarless construction, each block further comprises a
guide slot extending from the first opening along the bottom
surface of the block and terminating at the rear face of the block,
the guide slot being configured to accommodate the second portion
the length of strip reinforcement. The third portion of the length
of strip reinforcement may be arranged in coplanar alignment with
the top and or base surface of the blocks immediately prior to step
(e). In one embodiment the passage extends through the full height
of the block from a first opening provided in the bottom surface of
the block to a second opening provided in the top surface of the
block and step (b) comprises the step of inserting a length of
strip reinforcement through the passage from the first opening to
the second opening such that a fourth portion of the length of
strip reinforcement is arranged to extend outwardly from the rear
face of the block. For this embodiment, step (e) further comprises
the step of anchoring the position of the fourth portion of the
length of strip reinforcement by backfilling and compacting a
quantity of soil behind the rear face of the block. The fourth
portion may be arranged in general coplanar alignment with respect
to the top or bottom face of the block away from the wall
immediately prior to backfilling and compaction or arranged at an
angle with respect to the wall.
[0026] In another embodiment, the passage is a cavity extending
from the bottom surface to the top surface and the method further
comprises the step of adding a quantity of ballast to the cavity
after each block or each course of blocks has been laid. The
ballast may be drainage aggregate or an impermeable material such
as cast concrete.
[0027] The method of construction may further comprise the step of
installing one or more shear pins to resist sliding movement of a
first course over an adjacent second course.
[0028] In yet another embodiment, the plurality of lengths of strip
reinforcement are divided into a threaded section inserted into at
least one block at step (b) and a free section co-operatively
associated with the threaded section and arranged to extend
outwardly from the rear face of the block and be secured in
position during step (e) substantially perpendicular to the wall
during backfilling and compaction.
[0029] In one embodiment the reinforced soil retaining wall forms a
lower section of a composite wall, the composite wall being divided
a transition depth into an upper section and the lower section and
the method further comprises the step of constructing a gravity or
cantilever retaining wall to form the upper section of the
composite wall. Using this embodiment, the method may further
comprise the step of installing a soil reinforcement protection
barrier at the transition depth in general coplanar alignment with
the top uppermost course of blocks forming the lower section of the
composite wall. The step of installing a soil reinforcement
protection barrier may comprise the step of laying a concrete
slab.
[0030] According to a third aspect of the present invention there
is provided a block for use in constructing the reinforced soil
retaining wall system of the first aspect of the present invention.
According to a fourth aspect of the present invention there is
provided a length of strip reinforcement for use in constructing
the reinforced soil retaining wall system according the method of
the second aspect of the present invention.
[0031] According to a fifth aspect of the present invention there
is provided a reinforced soil retaining wall system comprising:
[0032] a plurality of blocks arranged in courses above a base
course to form a wall, the wall having a retained side and a dredge
side, each block comprising a front face oriented in use towards
the dredge side of the wall, a rear face spaced from said front
face by a distance defining the depth of said block and oriented in
use towards the retained side of the wall, a top surface, a bottom
surface spaced from said top surface by a distance defining the
height of said block, opposing side surfaces spaced from each other
by a distance defining the width of said block; [0033] a first
plurality of sections of soil reinforcement for anchoring the wall
to the backfill, the first plurality of sections of soil
reinforcement arranged between adjacent courses of the wall and
extending outwardly from the rear face of the blocks on the
retained side of the wall; and, [0034] a second plurality of
sections of soil reinforcement for stabilizing a quantity of
backfilled and compacted soil on the retained side of the wall, the
second plurality of sections of soil reinforcement being spaced
apart from the first plurality of sections of soil reinforcement
and arranged to extend substantially perpendicular to the wall
during backfilling and compaction.
[0035] The second plurality of sections of soil reinforcement may
be spaced apart from the rear face of the wall, laid immediately
adjacent thereto or be in abutting contact therewith.
[0036] In one embodiment, one or both of the first or second
plurality of sections soil reinforcement is/are resiliently
flexible. The length of the plurality of second sections of soil
reinforcement depends on the particular application and may be
equal to at least 60%, 70% or 80% of the height of the wall. It is
advantageous for the plurality of second sections of soil
reinforcement have a length that extends at least through the
anticipated plane of rupture of the backfill which is again a
function of a number of factors including the soil characteristics
of the backfill and the properties of the wall itself.
[0037] One or both of the first or second plurality of sections of
soil reinforcement may be planar, such as geomesh or take the form
of elongated strips of strip reinforcement.
[0038] In one embodiment the first and second plurality of sections
of soil reinforcement are arranged in horizontal coplanar
arrangement with respect to each other. In another embodiment, the
first plurality of sections of soil reinforcement are arranged in a
first layer and the second plurality of sections of soil
reinforcement are arranged in a second layer offset from the first
layer.
[0039] One or both of the first or second plurality of sections of
soil reinforcement may be arranged in coplanar alignment with the
top and or base surface of one or more of the plurality of blocks
immediately prior to backfilling and compacting. The second
plurality of sections of soil reinforcement may equally be arranged
at other heights.
[0040] In one embodiment, the blocks further comprise one or more
cavities extending from the bottom surface to the top surface, the
cavity configured to receive a quantity of ballast which may be
drainage aggregate or an impermeable material such as cast concrete
or cement mortar. For soils with poor drainage, the system may
further comprise a drainage channel configured to direct moisture
from the retained side of the wall towards the dredge side of the
wall.
[0041] In another embodiment, the reinforced soil retaining wall
system forms a lower section of a composite wall, the composite
wall being divided a transition depth into an upper section and the
lower section. The upper section may be a gravity or cantilever
type retaining wall. Using this embodiment, a soil reinforcement
protection barrier such as a concrete slab or sheet of plastic
material may be placed at the transition depth in general coplanar
alignment with the top uppermost course of blocks forming the lower
section of the composite wall.
[0042] Where mortar is used to construct the wall, the first
plurality of sections of soil reinforcement are fixedly held
between adjacent courses of blocks using mortar. Alternatively for
mortarless construction, the first plurality of sections of soil
reinforcement are fixedly held between adjacent courses of blocks
by gravity under the weight of the blocks forming the adjacent
courses.
[0043] According to a sixth aspect of the present invention there
is provided a method of construction of a reinforced soil retaining
wall system, the system comprising a plurality of blocks arranged
in courses above a base course to form a wall, the method of
construction comprising the steps of: [0044] a) providing a level
surface for laying a course of blocks, each block comprising a
front face, a rear face spaced from said front face by a distance
defining the depth of said block, a top surface, a bottom surface
spaced from said top surface by a distance defining the height of
said block, opposing side surfaces spaced from each other by a
distance defining the width of said block; [0045] b) arranging a
first plurality of sections of soil reinforcement for anchoring the
wall to the backfill between adjacent courses of the wall whilst
laying each course of blocks, the first plurality of sections of
soil reinforcement being arranged to extend outwardly from the rear
face of the blocks on the retained side of the wall; [0046] c)
laying each subsequent course until a required height for the
retaining wall has been achieved; [0047] d) arranging a second
plurality of sections of soil reinforcement spaced apart from the
first plurality of sections of soil reinforcement and arranged to
extend during step (e) substantially perpendicular to the wall;
and, [0048] (e) backfilling and compacting a quantity of backfill
behind the rear face of the blocks so as to anchor the position of
the first and second plurality of sections of soil
reinforcement.
[0049] Step (e) may be conducted after step (b) and prior to step
(c) for each course of conducted after the wall has been completed.
The second plurality of sections of soil reinforcement may be
arranged during step (e) so as to be spaced apart from the rear
face of the wall.
[0050] In one embodiment, the first and second plurality of
sections of soil reinforcement are arranged in horizontal coplanar
arrangement with respect to each other. Alternatively, the first
plurality of sections of soil reinforcement are arranged in a first
layer and the second plurality of sections of soil reinforcement
are arranged in a second layer offset from the first layer.
[0051] One or both of the first or second plurality of sections of
soil reinforcement may be arranged in coplanar alignment with the
top and or base surface of one or more of the plurality of blocks
immediately prior to backfilling and compacting.
[0052] In one embodiment, the blocks further comprise one or more
cavities extending from the bottom surface to the top surface, the
cavity configured to receive a quantity of ballast and the method
further comprises the step of adding a quantity of ballast to the
cavity after each block or each course of blocks has been laid. The
ballast may be drainage aggregate or an impermeable material such
as concrete or cement mortar.
[0053] The system may further comprise the step of installing one
or more shear pins to resist sliding movement of a first course
over an adjacent second course.
[0054] In yet another embodiment, the reinforced soil retaining
wall forms a lower section of a composite wall, the composite wall
being divided a transition depth into an upper section and the
lower section and the method further comprises the step of
constructing a gravity or cantilever retaining wall to form the
upper section of the composite wall A soil reinforcement protection
barrier may be installed at the transition depth in general
coplanar alignment with the top uppermost course of blocks forming
the lower section of the composite wall.
[0055] For mortared construction, the first plurality of sections
of soil reinforcement may be fixedly held between adjacent courses
of blocks using mortar. For mortarless construction, the first
plurality of sections of soil reinforcement may be fixedly held
between adjacent courses of blocks by gravity under the weight of
the blocks forming the adjacent courses.
BRIEF DESCRIPTION OF THE DRAWINGS
[0056] In order to facilitate a more detailed understanding of the
nature of the invention several embodiments of the reinforced soil
retaining wall system will now be described in detail, by way of
example only, with reference to the accompanying drawings, in
which:
[0057] FIG. 1 is a side cross-sectional view through a wall
constructed according to a first embodiment of the reinforced soil
system of the present invention using mortar to secure the position
of the blocks and illustrating the arrangement of the courses of
blocks and lengths of strip reinforcement anchoring the wall under
backfilled and compacted soil;
[0058] FIGS. 2 (a) and 2 (b) each illustrate an isometric view of
one of the blocks used to construct the wall of FIG. 1 illustrating
the position of the passage into which a length of strip
reinforcement is inserted before the block is laid and the position
of a guide slot for receiving a second portion of the a length of
strip reinforcement so that blocks in adjacent course may sit flush
relative to each other for use in the construction of a mortarless
wall;
[0059] FIG. 3 is a cross-section view through section A-A of the
block of FIG. 2 (a);
[0060] FIG. 4 illustrates the block of FIG. 3 with a length of
strip reinforcement inserted therein;
[0061] FIG. 5 is an isometric cross-sectional view through part of
the wall showing a plurality of lengths of strip reinforcement
threaded through the blocks;
[0062] FIG. 6 is a partial isometric view of a wall for which two
courses have been constructed showing the arrangement of the blocks
and lengths of strip reinforcement prior to backfilling and
compaction for a first embodiment of the present invention;
[0063] FIG. 7 is an isometric view of a completed wall showing the
arrangement of the blocks and lengths of strip reinforcement
through two courses of blocks after backfilling and compaction for
a first embodiment of the present invention;
[0064] FIG. 8 is an isometric view of a block used in accordance
with a second embodiment of the reinforced soil retaining wall
system of the present invention;
[0065] FIG. 9 is a cross-sectional view through section B-B of the
block illustrated in FIG. 8 showing the arrangement of the length
of strip reinforcement inserted into the block;
[0066] FIG. 10 is a partial isometric view of a wall for which two
courses have been constructed showing the arrangement of the blocks
and lengths of strip reinforcement prior to backfilling and
compaction for a second embodiment of the present invention;
[0067] FIG. 11 is a side cross-section view of a third embodiment
of the present invention illustrating a composite wall having an
upper section and a lower section;
[0068] FIG. 12 is a side cross-section view of a fifth embodiment
of the present invention showing an impermeable layer and drainage
channel for retaining clay soils;
[0069] FIG. 13 illustrates an alternative embodiment for use with
clay soils in which the cavities of the blocks illustrated in FIGS.
8 and 9 are filled with drainage aggregate which forms the
permeable layer;
[0070] FIG. 14 is a partial isometric view of a completed wall
constructed using a fourth embodiment of the present invention
whereby the strip reinforcement is laid in sections; and,
[0071] FIG. 15 is a partial isometric view of a reinforced soil
wall system constructed using a first plurality of sections of soil
reinforcement between courses and a second plurality of sections of
soil reinforcement embedded in the backfilled soil and arranged in
a spaced apart relationship relative to the first plurality of
sections of soil reinforcement.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0072] Particular embodiments of various aspects of the present
invention are now described in the context of the construction of a
single tiered straight retaining wall. It is to be understood that
the various aspects of the present invention are readily adaptable
to the construction of multi-tiered or curved retaining walls. The
terminology used herein is for the purpose of describing particular
embodiments only, and is not intended to limit the scope of the
present invention. Unless defined otherwise, all technical and
scientific terms used herein have the same meanings as commonly
understood by one of ordinary skill in the art to which this
invention belongs. For the purposes of clarity, some of the terms
as used throughout this specification are now defined.
[0073] The "dredge side" of a retaining wall is the side with the
lower soil surface elevation. The "dredge line" is the term applied
to the line of intersection between the soil surface on the dredge
side of the wall and the wall itself. The "retained side" of the
retaining wall is the side with the higher soil surface elevation
after backfilling. The term "backfill" refers to any type of
material, typically soil that is placed on the retained side of the
wall. The backfill that is placed behind a reinforced soil
retaining wall is also referred to in the art as "reinforced soil".
Loose backfill can add to the load on the retaining wall, allows
water to collect, causes settlement problems and may not anchor
soil reinforcement materials properly. Accordingly, all backfill is
compacted to meet the requirements of prevailing local compaction
standards, the term "compaction" referring to the application of
mechanical force to reduce the compressibility of the backfill and
mitigate the risk of future movement of the retaining wall.
[0074] "Drainage Aggregate" is free-draining, typically angular
gravel of substantially coarse and uniform size used to expedite
drainage of moisture. For best results, drainage aggregate should
consist of a plurality of stone particles of sufficiently large and
common size to cause voids to exist between them to allow the
passage of the water and should not contain fine particles that may
impede water flow.
[0075] A "course" is a horizontal layer of retaining wall blocks.
The "base course" is the first layer of blocks typically placed on
top of a leveled foundation. The "capping" is the last or top
course of blocks which may be designed for decorative appeal. The
capping is constructed using solid (as opposed to hollow) blocks to
prevent the ingress of water into the retaining wall. The "bond" is
the arrangement or pattern of blocks from course to course. A block
that is centered over the vertical joint created by adjacent blocks
in the preceding course is said to be laid using a "stretcher
bond".
[0076] The term "geomesh" is used throughout this specification to
describe soil reinforcement in the form of sheets of a polymeric
material, typically but not necessarily of woven construction with
transverse strands integrally connected with longitudinal strands
in a grid-like pattern.
[0077] A first embodiment of the reinforced soil retaining wall
system 10 of present invention is now described with reference to
FIGS. 1 to 7, the reinforced soil retaining wall system 10
comprising a plurality of blocks 12 arranged in courses 14 to form
a wall 16. Soil reinforcement is provided to the wall 16 using a
plurality of lengths of strip reinforcement 18 inserted in and
extending from the blocks 12, the strip reinforcement 18 being
buried under compacted backfill 20 either as each course 14 is laid
or after construction of the wall 16.
[0078] With reference to FIGS. 1, 2(a) and 2(b), the blocks 12 used
in accordance with a first embodiment of the reinforced soil wall
system 10 comprise a front face 22, a rear face 24 spaced from said
front face by a distance defining the depth of the block 12,
opposing side surfaces 26 and 28 respectively, spaced from each
other by a distance defining the width of the block 12, a top
surface 30 and a bottom surface 32 spaced from the top surface 30
by a distance defining the height of the block 12. In use, the
block 12 is positioned such that the front face 22 is directed
towards the dredge side 34 of the wall 16 with the rear face 24
being directed towards the retained side 36 of the wall 16. The
block 12 further comprises a passage 40 extending from a first
opening 42 in the bottom surface 32 towards the top surface 30. The
first opening 42 could equally be provided in the top surface 30.
With reference to FIG. 4, the passage 40 is configured to receive a
first portion 44 of a length of strip reinforcement 18 used to
stabilize the wall 16.
[0079] FIG. 1 illustrates a wall 16 constructed using a plurality
of layers of mortar 47 to secure the position of each block 12. For
mortarless construction, the bottom surface 32 of the block 12 is
provided with one or more guide slot(s) 50 extending from the first
opening 42 of the passage 40 to the rear face 24 of the block 12.
The guide slot 50 is configured to accommodate a second portion 46
of the length of strip reinforcement 18 in such a way that the
bottom surface 32 of a block 12 provided in a subsequent course 14'
is able to sit flush against the top surface 30 of a block 12 in an
underlying preceding course 14''. This is achieved by ensuring that
the guide slot 50 is of sufficient depth to house the thickness of
the length of strip reinforcement 18. The guide slot 50 also
assists in general directional alignment of the strip reinforcement
18 towards the retained side 36 of the wall 16. A third portion 48
of the length of strip reinforcement 18 is not received within the
block 12 but rather extends outwardly away from the rear face 24 of
the block 12.
[0080] Where mortar is used in the construction of the reinforced
wall retaining wall system 10, the guide slot 50 is entirely
optional and need not be present. This is because the second
portion 46 of the strip reinforcement 18 can be housed within the
layer of mortar 47. Thus where mortar is used, the first portion 44
of the length of strip reinforcement 18 is received within the
passage 40 of the block 12, the second portion 46 of the length of
strip reinforcement 18 is arranged to extend in coplanar alignment
with either the top or bottom surface 30 or 32, respectively of the
block 12 through the mortar layer 17, and the third portion 48 of
the length of strip reinforcement 18 is arranged to extend
outwardly from the rear face 24 of the block 12 to be secured in
position substantially perpendicular to the wall 16 during
backfilling and compaction.
[0081] It is to be understood that the passage 40 need not extend
through the full height of the block 12 provided only that the
length of strip reinforcement 18 is caused to bend through an
angle, preferably through approximately a 90 degree angle in order
to resist pull-out forces that are applied to the strip
reinforcement 18 after backfilling and compaction which put the
strip reinforcement 18 into tension. It is preferable that the
passage 40 is substantially vertically oriented relative to the top
or base surface 30 or 32, respectively of the block 12. For this
reason, the strip reinforcement 18 is resiliently flexible allowing
it to be bent into position through a 90 degree angle. It is
preferable that the passage 40 be positioned towards the front face
22 of the block 12.
[0082] It is also to be understood that the length of strip
reinforcement 18 is not directly mechanically coupled to the block
12. Its position is effectively secured during the backfilling and
compaction operations. In use, the length of strip reinforcement 18
is inserted into block 12 through the first opening 42 in so that
the first portion 44 is received within the passage 40 and bent in
place so that the second portion 46 is accommodated within the
guide slot 50 for mortarless construction or within a layer of
mortar 47 for construction using cement mortar. If the passage 40
extends through the full height of the block 12 from the bottom
surface 32 through to the top surface 30, the passage 40 terminates
in a second opening 52 provided in the top surface 30. The length
of strip reinforcement 18 may be threaded through the passage 40
through either the first opening 42 or the second opening 52.
[0083] The strip reinforcement 18 may be made from any other
material known to be suitable for soil reinforcement applications,
for example, galvanized steel strip, knitted high strength
polyester yarn, strips of polymer textured fabric, or high density
polyethylene.
[0084] Conveniently, each length of strip reinforcement 18 may be
cut from a sheet of mesh reinforcement, for example, geomesh and
accordingly need not comprise a single longitudinal section. The
strip reinforcement 18 may equally comprise a plurality of
longitudinal sections held together by a plurality of horizontal
sections, provided only that the strip reinforcement 18 is still
insertable in the passage 40. The length of the strip reinforcement
18 required to stabilize the wall 16 is directly proportion to the
height of the wall 16 and should be at least 0.7.times.height of
the wall. For poor soil and heavier loads the strip reinforcement
18 should be longer and or the quantity greater.
[0085] The material of construction of the blocks is equally
unimportant to the working of the present invention. Typically each
block 12 would be constructed from concrete which is made from a
mixture of cement, water and one or more types of aggregate(s). The
blocks may equally be constructed of other materials known to be
suitable for retaining walls including geopolymers, limestone or
metal. The colour and/or texture of the blocks is also not
important and may be varied by, for example, adding oxides to the
concrete or geopolymer or changing the type of aggregate used for
aesthetic appeal.
[0086] In order to facilitate a better understanding of the various
aspects of the first embodiment of the present invention, a method
of construction of a reinforced soil retaining wall using the
blocks 12 will now be described in the context of mortared
construction. It is to be understood that the reinforced soil
retaining wall system 10 is equally adaptable to mortarless
construction as described below with respect to a second embodiment
of the present invention.
[0087] The first step is the preparation of the site and the laying
of a level foundation 60. An area is excavated on the retained side
of the wall 16 to accommodate the design length of the soil
reinforcement 18 which will vary in direct proportion to the height
of the wall 16 above the dredge line 38. Any surface vegetation or
organics in the soil should be removed if it is intended to be used
as part of the backfill 20. A trench is dug along the full length
of the wall 16 and the foundation 60 is prepared using a simple
concrete slab or formed using any suitable compactable granular
material such as crushed stone, road base aggregate, gravel, or
coarse sand. The foundation 60 should be level along the full
length of the wall 16 for best results.
[0088] The base course 62 is then laid on the level foundation 60.
As is the case for any wall constructed using blocks, it is
important that the base course be laid with particular care as any
irregularities in the laying of the base course will become
exaggerated as the height of the wall increases for mortarless
construction. This is less important when using mortar to construct
the retaining wall as any irregularities in the laying of the base
course can be corrected by adjusting the amount of mortar. To
assist in correct placement of the base course blocks, a string
line (not shown) or other suitable alignment guide such as a laser
sight should be used to guide the positioning of the blocks. A
level indicating device such as a spirit level (not shown) should
be used to check the level of each block in both the front-to-back
and side-to-side directions after placement. A rubber mallet or
other suitable dead blow hammer may be used to help adjust the
position of a given block relative to the string line or spirit
level as required. Unevenness in the base course can be corrected
if needed using a suitable level correction device, for example,
one or more shims (not shown).
[0089] With reference to FIG. 1, the base course 62 is laid such
that the blocks are partially embedded below the dredge line 38.
Partial embedment of the base course blocks provides reinforcement
to the base course 62 to reduce the risk of erosion under the wall
16 at the dredge line 38. There is no requirement that any soil
reinforcement be used to provide support to the base course 62 and
accordingly, the blocks 12 of the present invention need not be
used in the construction of the base course 62. Any suitably sized
block may be used, including solid blocks if convenient. If hollow
blocks are used in the construction of the base course 62, the
cavities of the hollow blocks may be filled either with drainage
aggregate or an impermeable material such as concrete or cement.
When aggregate is used, this should be tamped down to ensure that
the cavities are filled, taking care not to disturb the position of
the blocks.
[0090] Once the base course 62 has been laid, a suitable infill
soil is used as the backfill 20 placed behind the base course 62.
The backfill 20 is then compacted using any suitable compaction
device such as a hand tamper or a mechanical plate compactor such
as a vibratory-plate compactor. Compaction should be carried out to
applicable civil engineering compaction standards which may vary
from country to country. It is considered to be a matter of routine
to a person skilled in the art to appreciate the level of
compaction required to achieve civil engineering certification of
the completed retaining wall.
[0091] The second and each subsequent course of blocks 12 apart
from the final course 64 are constructed using the blocks 12 of the
present invention. Prior to laying each subsequent course 14, any
debris or surface material should be removed from the top
surface(s) 30 of the blocks 12 of the preceding underlying course.
This provides a smooth surface for the placement of the next course
of blocks. It is further recommended to reset the string line for
each course and use the spirit level in the manner described above
to assist in correct alignment of the blocks 12. The bond of each
subsequent course is generally set such that the vertical seams 66
are offset for maximum strength. It is to be understood that the
blocks need not be placed in the stretcher bond arrangement.
[0092] With reference to FIG. 5, a length of strip reinforcement 18
is threaded through the first opening 42 and up into the passage 40
such that the first portion 44 is received within the passage 40.
The length of strip reinforcement 18 is then bent such that the
second portion 46 is arranged to extend along the bottom surface 32
from the first opening 42 towards the rear face 24. A layer of
mortar 47 is then applied and the block 12, with the length of
strip reinforcement 18 inserted therein, is laid over the blocks 12
forming the preceding course 14. The third portion 48 of the strip
reinforcement 18 extends outwardly from the block 12 in the
direction of the retained side 36 of the wall 16. Backfilling and
compaction to anchor the strip reinforcement 18 in place may be
conducted either after each course 14 is laid or after the wall 16
has been completed and is conducted in an analogous manner as
described above in relation to the laying of the base course
62.
[0093] Immediately prior to backfilling after each or all of the
second and subsequent courses 14 have been laid, each of the third
portions 48 of the lengths of strip reinforcement 18 is oriented so
as to be approximately perpendicular to the wall 16 and in general
coplanar alignment with respect to the top or bottom surface 30 or
32, respectively of the block 12. Each third portion 48 is then
held in this position when covered with infill soil during the next
backfilling and compaction operation. Advantageously, it is
possible to use separate crews during the construction of the
reinforced soil retaining wall system of the present invention--a
block laying crew being responsible for inserting the strip
reinforcement 18 in the blocks 12 during laying thereof and an
earth compaction crew being responsible for orienting the position
of each of the third portions 48 during backfilling and compaction
operations after the wall has been completed.
[0094] Additional courses 14 are laid in this manner until the wall
16 is of the required height. During backfilling and compaction,
the weight of the backfill 20 behind the wall 16 may cause the wall
to cant towards the dredge side 34. To offset this, each course 14
may be set back approximately 4 mm or more from the preceding
course 14 towards the retained side 36 of the wall 16 so that the
completed wall 16 cants back by 2% or more towards the retained
side 36 prior to backfilling. After backfilling and compaction, the
wall 16 is substantially vertical.
[0095] If desired the final course 64 may take the form of capping
as illustrated in FIG. 7, to give the wall a more aesthetically
pleasing appearance. The capping 64 may be secured in position
using a waterproof construction adhesive and is of solid
construction to prevent water from entering the passages 40
provided in the blocks 12 that are used to construct the wall
16.
[0096] When the soil being retained has a low permeability such as
clay, a layer of drainage aggregate 104 may be placed immediately
adjacent the retained side 36 of the wall 16 to prevent a buildup
of hydrostatic pressure against this side of the wall.
[0097] A second embodiment of the blocks of the present invention
is illustrated in FIGS. 8 to 10 for which like reference numerals
refer to like parts. In this embodiment the blocks 12 are provided
with a plurality of cavities 72 (in this example, two such cavities
are shown) each cavity 72 extending through the full height of the
block 12 and able to serve the same function as the passage 40 of
the block 12 described above in relation to the first embodiment.
These blocks 12 are hereinafter referred to as "hollow blocks". One
of the advantages of using hollow blocks 12 is that the effective
weight of each block is lower than the weight of a block of solid
construction of equivalent size, making the hollow blocks easier to
carry, stack and lay. Another advantage is that the cavities 72
have a larger volume than the passage 40 of the first embodiment,
making insertion of the length or lengths of strip reinforcement 18
into or through the block 12 easier.
[0098] For mortarless construction, each of the hollow blocks 12 is
provided with one or more guide slot(s) 50 which serve the same
function as described above in relation to the first embodiment.
Where mortar is used, the guide slot(s) 50 are not required. It is
not necessary for a guide slot 50 to be provided for each of the
cavities 72. In order to facilitate a better understanding of the
various aspects of the second embodiment of the present invention,
a method of mortarless construction of a reinforced soil retaining
wall using the hollow blocks 12 will now be described with
reference to FIGS. 8 to 10. It is to be understood that the
reinforced soil retaining wall system 10 is equally adaptable to
construction using mortar in an analogous manner as described above
with respect to the first embodiment of the present invention.
[0099] During construction of the wall 16 using the hollow blocks
12, the foundation 60 and the base course 62 are laid in an
analogous manner to that described above in relation to the first
embodiment. Backfilling and compaction is conducted after the base
course 62 has been laid.
[0100] The second and each subsequent course of blocks 12 (apart
from the final course 64) are constructed using the hollow blocks
12. With reference to FIG. 9, a length of strip reinforcement 18 is
threaded through one of the cavities 72 such that a first portion
44 is received within the cavity 72. The length of strip
reinforcement 18 is then bent through substantially 90 degrees such
that the second portion 46 is accommodated within the guide slot
50. The first portion 44 is positioned within the cavity 72 towards
the front face 22 of the block 12 to provide maximum resistance to
overturning forces on the wall 16.
[0101] When the hollow block 12 with the length of strip
reinforcement 18 inserted is laid over the blocks forming the
preceding course 14, the guide slot 50 is positioned towards the
retained side 36 of the wall 16. As or after each new course is
laid, the cavities 72 of the hollow blocks 12 are filled with a
quantity of ballast 76 in the form of an impermeable material, for
example, concrete, or a permeable material, for example, drainage
aggregate. Where drainage aggregate is used, the material should be
tamped down within the cavity to ensure that no voids are left. The
ballast 76 assists in providing stability to the wall, helps to
retain the position of the strip reinforcement 18 relative to the
cavity 72 and helps to resist movement of the blocks during the
backfilling and compaction operations. The drainage aggregate also
acts as a cushion to protect the strip reinforcement from damage
that may occur if the strip reinforcement is allowed to come into
contact with either of the rearward edges 78 of the cavity 72.
Moreover, since concrete has poor bending strength, the aggregate
helps to distribute the tensile forces acting on the strip
reinforcement 18 over a greater surface area that the inside rear
face 80 of the cavity 72.
[0102] After the hollow cavities 72 have been filled with the
quantity of ballast 76, the wall 16 is backfilled using an
appropriate infill soil and compacted in the manner described above
in relation to the base course 62. Immediately prior to backfilling
after the second or subsequent course 14 has been laid, the third
portion 48 of the length of strip reinforcement 18 is oriented so
as to be approximately perpendicular to the wall 16 and in general
coplanar alignment with respect to the bottom surface 32 of the
block 12. The third portion 48 is then held in this position when
covered with infill soil either after each course 14 is laid or
when the wall 16 has been completed.
[0103] With reference to FIGS. 9 and 10, this second embodiment
differs from the first embodiment in that the effective length of
the strip reinforcement 18 has been approximately doubled such that
a fourth portion 74 of the strip reinforcement 18 extends from the
first portion 44 which is received within the cavity 72. This
fourth portion 74 is caused to drape over the dredge side 34 of the
wall 16 during backfilling and compaction of the course 14 that has
just been laid. During backfilling and compaction, the third and
fourth portions 48 and 74 is laid over a layer of previously
compacted soil and oriented so as to be approximately perpendicular
to the wall 16 and in general coplanar alignment with respect to
the top or bottom surfaces 30 or 32, respectively, of the hollow
blocks 12.
[0104] Additional courses 14 are laid in this manner until the wall
16 is of the required height. If desired the final course 64 may
take the form of capping as described above. Backfilling and
compaction can be conducted after each course 14 is laid or after
the wall 16 has been completed.
[0105] To provide additional resistance against shearing across
adjacent courses 14 in the wall 16, the system 10 may further
include a plurality of shear pins 82 illustrated in FIG. 9, in the
form of a plurality of rectangular blocks made of concrete and
inserted into the cavity 72 prior to the cavity 72 being filled
with the quantity of ballast 76. It is worth noting that the use of
shear pins 82 is entirely optional in that it has been found that
when coarse aggregate is used as the ballast 76, resistance to
shear forces is provided by the particles of the coarse aggregate
themselves. When the cavities 72 have been filled with coarse
aggregate, movement of one block 12 in the wall 16 relative to an
adjacent block in an adjacent course 14 would require displacement
of the particles of coarse aggregate relative to each other.
Because the drainage aggregate particles are generally of the same
size, this is difficult to achieve, providing additional resistance
to shear between adjacent courses.
[0106] It is equally possible although more cumbersome to thread
the strip reinforcement 18 through a plurality of blocks 12 in
adjacent courses 14 as illustrated in FIG. 9. It should be noted
that it is not necessary for every block 12 to be provided with a
length of strip reinforcement unless large surcharge loads are
anticipated. It is considered a matter of routine for a person
skilled in the art to determine the requisite amount of strip
reinforcement required for the particular material of construction
of the wall, its height, the anticipated loads and the type of
backfill being retained.
[0107] A third embodiment of the reinforced soil retaining wall
system 10 and blocks 12 of the present invention is illustrated in
FIG. 11 for which like reference numerals refer to like parts.
During construction at a building site, the retaining wall is often
the first structure installed followed by other installations such
as plumbing, electrical, foundations and the like. In this third
embodiment, the system 10 comprises a composite wall 90 divided at
a transition depth 92 into an upper section 94 and a lower section
96. The lower section 96 of the composite wall is a reinforced soil
retaining wall 16 which is constructed in an analogous manner as
described above in relation to either the first or second
embodiments. The lower section 96 is laid with backfilling and
compaction is carried out on the retained side 36 of the composite
wall 90. The upper section 94 of the composite wall 90 is then
constructed as a gravity wall having a height equal to the
transition depth 92. The gravity wall 94 is constructed in
accordance with the practices of the background art.
[0108] The upper section 94 may equally take the form of a steel
reinforced cantilever wall by positioning a plurality of steel bars
(not shown) through the cavities 72 of the blocks used in the
construction of the upper section 94 of the composite wall 90, the
cavities 72 thereafter being filled with concrete to hold the steel
bars in place. A plurality of shear pins 82 may be installed inside
the blocks 12 in the uppermost course of the lower section 96 of
the composite wall 90 at the transition depth 92 to provide
resistance to shearing of the upper section 94 relative to the
lower section 96.
[0109] This third embodiment was based on a realization that the
top 0.1-0.9 meters of the retaining wall is effectively
self-supporting. The transition depth 92 depends in part on the
anticipated depth of any installations or structures to be
constructed on the retained side of the wall, but it is anticipated
that the transition depth will not exceed one metre and will more
likely be around 0.4 to 0.6 m below the final anticipated height of
the composite wall 90.
[0110] A soil reinforcement protection barrier 98 may be installed
at the transition depth 92 in general coplanar alignment with
respect to the top surface 30 of the uppermost course 14 of the
lower section 96. The barrier 98 serves as a visual or physical
barrier to protect the strip reinforcement 18 from damage during
subsequent building operations adjacent to the completed retaining
wall. Accordingly, the barrier 98 may take the form of a thin
planar strip of plastic that provides a visual indication that the
transition depth has been reached during subsequent digging.
Alternatively, the barrier 98 may take the form of a concrete slab
which provides physical resistance to penetration during subsequent
digging and providing additional protection to the strip
reinforcement 18 below.
[0111] A fourth embodiment of the system 10 and blocks 12 of the
present invention is illustrated in FIGS. 12 and 13 for which like
reference numerals refer to like parts. This embodiment has been
designed specifically to deal with problems associated with using
backfill such as clay soils which have a very slow rate of
permeation of water. As a result of the low permeability of the
soil, the backfill 20 may become saturated over time, for example
due to precipitation, resulting in a buildup in water being stored
on the retained side 32 of the wall 16. This causes hydrostatic
pressure on the wall 16 to increase, effectively pushing against
the retained side 32 of the wall 16.
[0112] One way to overcome this problem is to place a vertically
oriented permeable layer 104 of permeable material such as drainage
aggregate adjacent to the retained side 32 of the wall 16 to allow
water to drain under gravity from behind the wall through a
drainage channel 106 positioned towards the base of the wall 16 and
extending from the permeable layer 104 to the dredge side 34 of the
wall 16 above the dredge line 38. The drainage aggregate would
typically consist of a plurality of stone particles of sufficiently
large and common size to cause voids to exist between them to allow
the passage of the water. The permeable layer 104 may be laid in
sections as each course 14 is laid ensuring that the lengths of
strip reinforcement 18 extend through the permeable layer 104 to be
anchored in the backfilled and compacted soil 20 behind the
permeable layer 104. The wall 16 is otherwise constructed in an
analogous manner as described above in relation to any one of the
earlier embodiments.
[0113] Drainage aggregate is easily dislodged by workmen during
backfilling and compaction or laying operations and the block
laying crew must clear any loose stones before laying the next
course of blocks. In addition, the permeable layer 104 is not self
supporting and this can result in a thicker layer being used than
would otherwise be required leading to increased materials and
installation costs.
[0114] To alleviate this potential problem, the hollow blocks of
the second embodiment are particularly suited for use with clay
soils. If the cavities 72 are filled with drainage aggregate, the
wall itself can serve the function of the permeable layer 104 with
the guide slot(s) 50 provided in each hollow block 12 serving the
function of a plurality of drainage channels 106 each directing
water from the retained side 36 of the wall 16 into the cavities 72
filled with drainage aggregate. In this embodiment, the blocks 12
used in the construction of the base course 62 are inverted such
that the guide slot(s) direct water from the permeable layer 104
towards the dredge side 34 of the wall 16 to allow the water to
drain out of the wall itself.
[0115] The size and configuration of the guide slot(s) 50 may be
varied to suit the maximum predicted rainfall for a given
geographical location to drain from the retained soil at a rate
faster than the known flow capacity of the retained backfill 20.
The accumulated liquid inside the permeable layer 104 defined by
the filled cavities 72 of the hollow blocks 12 generates a head of
pressure that encourages the flow of liquid out through the guide
slots 50 of the inverted blocks 12 forming the base course 62.
[0116] It is to be understood that the base course 62 in this
fourth embodiment need not be constructed using inverted hollow
blocks 12 and could equally be constructed using the solid blocks
of the first embodiment or any other type of solid block provided
only that the wall 16 is provided with at least one drainage
channel 106 of a suitable size to direct the flow of liquid from
within the permeable layer 104 towards the dredge side 34 of the
wall 16.
[0117] A fifth embodiment of the system 10 and blocks 12 of the
present invention is illustrated in FIG. 14, for which like
reference numerals refer to like parts. As briefly described above
in relation to the first and second embodiments, each length of
strip reinforcement 18 is directly proportional to the height of
the anticipated final height of the wall 16. This can make
threading of the strip reinforcement 18 through a through-thickness
passage 40 or the cavity 72 difficult to achieve for walls that are
high, particular for walls higher than around 1.6 metres. It is not
only the threading of the strip reinforcement 18 through the cavity
72 or passage 40 of each block 12 that becomes increasingly
difficult as the height of the wall 16 increases, but also the
general handling of long lengths of strip reinforcement 18 which
has the tendency to curl and may snag more readily when trying to
lay each course 14 of the blocks 12.
[0118] This problem is overcome in this fifth embodiment by
splitting the length of strip reinforcement into a short threaded
section 100 and a longer free section 102. Each short threaded
section 100 is inserted through the block 12 in an analogous manner
as described above in relation to any one of the first three
embodiments. The longer free section 102 is then laid separately
during the backfilling and compaction operations either after each
course 14 has been completed or after the wall 16 has been
completed. Each free section 102 may be fixedly attached to a
corresponding threaded section 100 or laid so as to extend
substantially perpendicularly away from the wall 16 on the retained
side 32 at any depth within the backfill 20.
[0119] After backfilling and compaction, the combined effect of
laying the free section 102 separately and/or interdependently of
the threaded section 100 is the same as laying one continuous
length of strip reinforcement 18, provided only that the free
section 102 extends away from the retained side 32 of the wall 16
at least through the anticipated plane of rupture 108 of the
backfill 20. The plane of rupture 110 runs at an angle .beta.
relative to the dredge line 38 of the wall 16, the angle .beta.
being the Rankin angle (or angle of internal friction) which is a
function of the type of backfill 20 being retained.
[0120] A further advantage of using this embodiment, even for
shorter walls is that it allows for separate crews to be used--a
block laying crew being responsible for inserting the threaded
sections 100 in the blocks 12 and an earth compaction crew being
responsible for laying the free sections 102 during backfilling and
compaction.
[0121] It has further been realized that the threaded and free
sections 100 and 102 need not be provided in the form of lengths of
strip reinforcement 18 but may equally be provided using grid or
sheet reinforcement, for example, geomesh. FIG. 15 thus illustrates
a reinforced soil retaining wall system 110 for which like
reference numerals refer to like parts. The blocks 112 of this
embodiment may be any standard type of block used for the
construction of a reinforced soil retaining wall or the blocks 12
described above for any of the first to fifth embodiments. The
reinforced soil retaining wall system 110 comprises a first
plurality of sections of soil reinforcement 114 for anchoring the
wall 16 to the backfill 20, the first plurality of sections of soil
reinforcement 114 arranged between adjacent courses 14' and 14'' of
the wall 16 and extending outwardly from the rear face 24 of the
blocks 112 on the retained side 36 of the wall 16. In the
embodiment illustrated in FIG. 15, the first plurality of sections
of soil reinforcement 114 take the form of short sections of
geomesh. With reference to FIG. 14, it is to be understood that the
first plurality of sections of soil reinforcement 114 could equally
be provided using elongate strips such as the threaded sections 100
illustrated in FIG. 14 and that the elongate strips need not be
threaded through the blocks, provided only that they are arranged
between adjacent courses 14' and 14'' and extend outwardly from the
rear face 24 of the blocks 12 on the retained side 36 of the wall
16.
[0122] The reinforced soil retaining wall system 110 further
comprises a second plurality of sections of soil reinforcement 116
for stabilizing the backfilled and compacted soil on the retained
side 36 of the wall 16, the second plurality of sections of soil
reinforcement 116 being spaced apart from the first plurality of
sections of soil reinforcement 114 and arranged to extend
substantially perpendicular to the wall 16 during backfilling and
compaction. With reference to FIG. 15, the second plurality of
sections of soil reinforcement 116 are provided in the form of
large planar sheets of geomesh which are spaced apart from the
first plurality of sections of geomesh 114. Whilst geomesh is
preferred, other types of soil reinforcement may be used with
suitable materials being those that are resistant to aging in the
particular soil environment and which have sufficient tensile
strength to carry the anticipated loads in use.
[0123] In FIG. 15, the second plurality of sections of soil
reinforcement 114 is positioned immediately adjacent to the
retained side 36 of the wall 16. It is to be understood that the
second plurality of sections of soil reinforcement 114 could
equally be spaced apart from the rear face 24 of the blocks 112 on
the retained side 36 of the wall 16.
[0124] In the embodiment illustrated in FIG. 15, the first and
second plurality of sections of soil reinforcement 114 and 116,
respectively are arranged in horizontal coplanar arrangement with
respect to each other with the first plurality of sections of soil
reinforcement 116 being arranged in a first layer 118 and the
second plurality of sections of soil reinforcement 116 are arranged
in a second layer 120 offset from the first layer 118. The spacing
between the first and second layers 118 and 120 respectively may
vary depending on a number of factors but would generally not be
expected to exceed one metre.
[0125] The first plurality of sections of soil reinforcement 114
are arranged in coplanar alignment with the top or base surface 30
or 32, respectively of one or more of the plurality of blocks 112
immediately prior to backfilling and compacting. The second
plurality of sections of soil reinforcement 116 need not be
arranged in coplanar alignment with the top or base surfaces 30 or
32, respectively, but could equally be arranged in alignment with a
plane 122 that intersects the block 112 at a height intermediate
between the top and base surfaces 30 or 32.
[0126] The first plurality of sections of soil reinforcement 114
may be fixedly held between adjacent courses 14' and 14'' of blocks
112 using mortar or held by gravity under the natural weight of the
blocks forming the courses above.
[0127] Depending on a number of factors including the type and
quality of the soil used for the backfill 20, the length of the
second plurality of sections of soil reinforcement 114 may be equal
to at least 60%, 70% or 80% of the height of the wall 16 and should
extend through at least the anticipated plane of rupture 108 of the
backfill 20. It is considered to be a matter of routine to a person
skilled in the art to determine the quantity and length of second
plurality of sections of soil reinforcement 114 required for a
particular application depending on such factors as the slope
stability, the angle of internal friction .beta. of the soil, soil
cohesion and the moist unit weight of the soil as well as such
factors as the height of the wall, any surcharge loads and the top
slope angle. For example, for poor quality soil, a larger quantity
of the second plurality of sections of soil reinforcement 114 may
be required to provide sufficient stability to the wall. Where a
larger quantity is used, the tensile strength of each individual
section need not be as great as less load is carried by each
individual section.
[0128] As illustrated in FIG. 15, the wall 16 may be constructed
using the hollow blocks described above with respect to the second
embodiment with the exception that the guide slots 50 are not
required. The cavities 72 of the hollow blocks 112 are configured
to receive a quantity of ballast 76 as described above, the ballast
76 being either drainage aggregate or an impermeable material such
as concrete added to the cavities 72 apart the blocks 112 have been
laid. One or more shear pins 82 may be provided to resist sliding
movement of a first course 14' over an adjacent second course 14''
if desired. A drainage channel 106 configured to direct moisture
from the retained side 36 of the wall 16 towards the dredge side 34
of the wall 16 may also be provided if desired and is particular
advantageous when the backfill 20 is a clay soil in order to
relieve hydrostatic pressure that may otherwise be exerted on the
wall 16. The reinforced soil retaining wall system 110 is equally
adaptable for construction as a composite wall 90 in an analogous
manner as described above.
[0129] One embodiment of the method of construction of a reinforced
soil retaining wall 110 is now described with reference to FIG. 15
in the context of mortarless construction. It is to be understood
that the reinforced soil retaining wall system 110 is equally
adaptable to mortared construction, the mortar being used in part
to secure the position of the first plurality of sections of soil
reinforcement 114 between adjacent courses 14.
[0130] A foundation 60 and base course 62 are laid in an analogous
manner as described above. Once the base course 62 has been laid, a
suitable infill soil is used as the backfill 20 placed behind the
base course 62 and compacted to applicable civil engineering
compaction standards which may vary from country to country. Before
a subsequent course is laid, a first plurality of sections of soil
reinforcement 114 for anchoring the wall 16 to the backfill 20 is
arranged along the top surfaces 30 of the blocks 112 forming the
base course 62. The first plurality of sections of soil
reinforcement 114 are arranged to extend outwardly from the rear
face 24 of the blocks 112 on the retained side 36 of the wall 16.
It is to be understood that first plurality of sections of soil
reinforcement 114 need not extend along the full length of the wall
16 and need not be provided between each of the adjacent courses 14
forming the wall 16. Using mortarless construction, the first
plurality of sections of soil reinforcement 114 are held in place
by the weight of the next course of blocks laid over the top of
them. Where mortar is used, the layers of mortar 47 assist in
retaining the position of the first plurality of sections of soil
reinforcement 114 prior to backfilling.
[0131] The second plurality of sections of soil reinforcement 116
are laid during backfilling and compaction which may be conducted
either after each course 14 is laid or after the wall 16 has been
completed and is conducted in an analogous manner as described
above in relation to the laying of the base course 62. The second
plurality of sections of soil reinforcement 116 are arranged in
such a way that they are spaced apart from the first plurality of
sections of soil reinforcement 114 and extend substantially
perpendicular to the wall 16 during backfilling and compaction of a
quantity of backfill 20 behind the rear face 24 of the blocks 112
so as to anchor the position of the first and second plurality of
sections of soil reinforcement 114 and 116, respectively.
Additional courses 14 are laid in this manner until the wall 16 is
of the required height.
[0132] If desired, the final course 64 may take the form of capping
as illustrated in FIG. 7, to give the wall a more aesthetically
pleasing appearance. When the soil being retained has a low
permeability such as clay, a layer of drainage aggregate 104 may be
placed immediately adjacent the retained side 36 of the wall 16 to
prevent a buildup of hydrostatic pressure against this side of the
wall.
[0133] If hollow blocks are used to construct the wall 16, the
method of construction further comprises the step of adding a
quantity of ballast 76 to the cavities 72 either after each block
or each course of blocks has been laid in an analogous manner as
described above with reference to the second embodiment. Where
shear pins 82 are used to resist sliding movement of a first course
14' over an adjacent second course 14'', the placement thereof
should not interfere with the placement of the first plurality of
sections of soil reinforcement 114. Accordingly, shear pins 82 may
be provided between every second course 14 of blocks 112 with the
first plurality of sections of soil reinforcement 114 being
provided between the remaining courses.
[0134] Now that the preferred embodiments of the present invention
have been described in detail, the present invention has a number
of advantages over the prior art, including the following: [0135]
a) lightweight hollow blocks permit rapid installation and reduce
the likelihood of work-related injury to the block laying crew;
[0136] b) the strip reinforcement is not mechanically coupled to
the blocks thereby reducing the component cost of the block as well
as the labor time associated with installing the blocks. This also
reduces the opportunity for incorrect attachment of the
reinforcement to the facing block; [0137] c) the blocks may be
manufactured in a standard rectangular shape and laid in a standard
interlocking brick pattern which increases the aesthetics of the
wall and also increases its strength. The block can be cheaply and
readily mass produced as there is no need to incorporate mechanical
fasteners into the blocks; and, [0138] d) the system requires no
direct mechanical attachment of the strip reinforcement to the
blocks which allows for plastic to be used instead of galvanized
steel which reduces the material costs. Using prior art methods,
holes were needed in the strip reinforcement which made the use of
plastics impermissible as most plastic materials have poor
resistance to tearing.
[0139] It will be apparent to persons skilled in the relevant art
that numerous variations and modifications can be made without
departing from the basic inventive concepts. For example, the front
face of the block need not be planar but can be provided with a
different shape or surface texture on the dredge side of the wall.
Similarly, the wall system could further include a protective or
decorative facing panel (not shown) applied to the dredge side of
the wall to alter the aesthetic appeal thereof after construction.
Whilst in all of the illustrated embodiments, a single length of
strip reinforcement has been inserted per block, it is equally
permissible for a plurality of lengths of strip reinforcement to be
placed in a passage or cavity of a single block. The present
invention is equally applicable to the construction of a tiered
retaining wall by building a plurality of walls, each upper wall
set back from an underlying wall. Tiered walls can be attractive
alternatives to single tall walls and can provide areas for
plantings. To prevent an upper wall from placing a load on a lower
wall, the upper wall should be built behind the lower wall a
distance of at least twice the height of the lower wall. All such
modifications and variations are considered to be within the scope
of the present invention, the nature of which is to be determined
from the foregoing description and the appended claims.
* * * * *