WO2008070913A1 - Stabilised embankment - Google Patents

Stabilised embankment Download PDF

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Publication number
WO2008070913A1
WO2008070913A1 PCT/AU2007/001915 AU2007001915W WO2008070913A1 WO 2008070913 A1 WO2008070913 A1 WO 2008070913A1 AU 2007001915 W AU2007001915 W AU 2007001915W WO 2008070913 A1 WO2008070913 A1 WO 2008070913A1
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WO
WIPO (PCT)
Prior art keywords
retaining wall
block
wall
stabilized
length
Prior art date
Application number
PCT/AU2007/001915
Other languages
French (fr)
Inventor
Patrick Coatin Samuel
Original Assignee
Modalco Pty Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from AU2006906924A external-priority patent/AU2006906924A0/en
Application filed by Modalco Pty Ltd filed Critical Modalco Pty Ltd
Publication of WO2008070913A1 publication Critical patent/WO2008070913A1/en

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Classifications

    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D29/00—Independent underground or underwater structures; Retaining walls
    • E02D29/02—Retaining or protecting walls

Definitions

  • the present invention relates to a stabilized backfill material, a wall may attached to the backfill material, and a method of constructing a bound embankment with a wall.
  • the present invention further relates to a block used in the construction of a wall attached to stabilized embankment and a length of strip reinforcement used in the construction of a stabilized embankment attached to a wall:
  • Embankments are defined as any artificial mound or bank of earth that restrains or confines material on one side to maintain a difference in elevation. Nearby slopes, roads, railways, driveways, buildings, and tiered walls all represent potential loads on embankments. Embankments consist of earth, gravel, stones and the like formed into an artificial raised elevation. They are used for such applications as dams, supporting loads such as roads and railways.
  • the present specification describes an embankment confining soil on one side, said embankment consisting of separate particles of granular material that have undergone a chemical process to cause them to bind together to act as one mass after placing.
  • the present invention describes how a wall may be erected and the moist granular particles compacted against the wall. After the chemical reaction has occurred the wall serves no supporting function and may be removed or left in place. An application of such an invention would replace traditional retaining walls.
  • Retaining walls are known and are used to hold back soil or rock from a building, structure or other area. Retaining walls prevent down slope movement or erosion and provide support for sloping, vertical or near vertical grade changes.
  • Known retaining walls consist of a face wall, for example constructed of hollow masonry blocks, and backfill material behind the face wall for resisting, overturning and sliding of the face wall.
  • the soil behind the face wall attempts to cause the face wall to rotate forward at its base away from the soil.
  • the soil may also cause the face wall to slide forward.
  • the costs associated with constructing a retaining wall include; excavation of the existing soil; construction of the wall face; and the soil reinforced backfilling behind the face wall.
  • Such reinforced retaining walls can reduce the cost of the face wall significantly, but require additional excavation and backfilling, which each creates its own cost.
  • the required width of the reinforced soil mass may be more than height of the face wall and achieving the required width may not be possible due to rock or other structures being present behind the face wall.
  • Some building sites also do not have enough room to temporarily store all of the excavated material during the retaining wall const ⁇ jction. Further, in some areas, excavation and back filling costs are uneconomic.
  • the width of the gravity retaining wall can be reduced by using heavy materials as the back fill material. This is commonly achieved by pouring concrete behind the wall.
  • using concrete has disadvantages including: it is a very expensive material; and, whilst in its liquid state, can easily cause the face wall to be pushed out.
  • stabilised embankment and "stabilised soil” refers to a mass of particles, including clay, affected by a process by which the intrinsic properties of the embankment material are altered by the addition of a stabilisation binder to meet performance expectations in its operating, geological and climatic environment.
  • a stabilisation binder it is the purpose of the binder to cause adherence between the particles that constitute the embankment to cause them to act in unison against forces imposed onto the embankment. Such forces may be sliding, overturning or shear.
  • the embankment may incorporate substantially horizontal layers of soil reinforcement material buried within the stabilised soil to enhance the properties of the mass.
  • a stabilized soil embankment with a wall 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
  • 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.
  • each length of strip reinforcement is resiliently flexible.
  • 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.
  • 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.
  • 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 or stabilized soil.
  • the passage may be one of plurality of passages.
  • 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.
  • the plurality of lengths of strip reinforcement are divided into a section inserted into at least one block and a free section co-operatively associated with the inserted section and 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 of the stabilized or naturally stabilized soil.
  • a method of construction of a stabilized soil retaining wall 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 stabilized 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
  • 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.
  • 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).
  • 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.
  • 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 stabilized 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.
  • 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, a stabilized material or poured concrete.
  • the plurality of lengths of strip reinforcement are divided into a section inserted into at least one block at step (b) and a free section cooperatively associated with the inserted 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 of the stabilized soil.
  • a block for use in constructing the stabilized soil retaining wall system of the first aspect of the present invention there is provided a length of strip reinforcement for use in constructing the stabilized soil retaining wall system according the method of the second aspect of the present invention.
  • 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 stabilized soil.
  • a drainage channel configured to direct moisture from the retained side of the wall towards the dredge side of the wall.
  • the first plurality of sections of soil reinforcement are fixedly held between adjacent courses of blocks using mortar.
  • 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.
  • a method of construction of a stabilized soil retaining wall 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 stabilized embankment 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 embankment side of the wall; c) laying each subsequent course until a required height for the retaining wall
  • 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.
  • first and second plurality of sections of soil reinforcement are arranged in horizontal coplanar arrangement with respect to each other.
  • 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.
  • 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 stabilized soil.
  • 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 stabilized soil.
  • the first plurality of sections of soil reinforcement may be fixedly held between adjacent courses of blocks using mortar.
  • 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.
  • a method of construction of a stabilized soil retaining wall system comprising a mass of stabilized soil formed in compacted layers with sloping sides formed by the friction angle of the unbound material. After the chemical reaction has formed a bound mass the side or a plurality of sides of the mass may be cut to a steeper angle. One angle that could be obtained is 90 degrees.
  • a method of construction of a stabilized soil retaining wall 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 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, the mass of each block being sufficient to self support the wall without reinforcement.
  • the stabilized mass may consist of: a) naturally occurring material that forms a bound mass upon compaction b) waste form an industrial process excluding the process of manufacture of iron or steel c) Clay combined with a stabilizing agent d) A mass of compactable material combined with an agent designed to promote the binding of the particles into a single bound mass. e) A mass of compactable material combined with an enzyme designed to promote the binding of the particles into a single bound mass.
  • reaction refers to the application of mechanical force to reduce the compressibility of the backfill, increase density and mitigate the risk of future movement of the embankment.
  • the stabilized mass is formed by providing a layer of stabilized soil of sufficient thickness and moisture to permit the vibration from a compacting device to penetrate the layer to create sufficient density to provide a self supporting unconfined compressive strength. Another layer of stabilized soil is placed onto the compacted layer and compacted in the same procedure.
  • the stabilized embankment consists of a plurality of these compacted layers of stabilized soil.
  • a wall of sufficient mass to be self supporting or a wall attached to the stabilized embankment by way of reinforcement may be provided to create an alternative to a retaining wall or to prevent erosion of the face.
  • this invention could also be described as a retaining wall to create an awareness of its purpose.
  • the stabilized soil embankment with attached masonry wall will be referred to as a retaining wall throughout this description.
  • Figure 1 is an isometric view of a block used in accordance with a second embodiment of the stabilised soil retaining wall system of the present invention
  • Figure 2 is a cross-sectional view through section B-B of the block illustrated in Figure 1 showing the arrangement of the length of strip reinforcement inserted into the block;
  • Figure 3 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;
  • Figure 4 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;
  • Figure 5 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;
  • 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.
  • backfill refers to any type of stabilized material, typically stabilized soil that is placed on the retained side of the wall. Loose backfill can add to the load on the retaining wall, allows water to collect and causes settlement problems. All stabilized soil 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.
  • Drainage Aggregate is free-draining, typically angular gravel of substantially coarse and uniform size used to expedite drainage of moisture.
  • 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.
  • 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”.
  • geomesh is used throughout this specification to describe soil reinforcement in the form of strips of a polymeric material.
  • the foundation 60 and the base course 62 are laid with the base course 62 being laid onto the foundation 60.
  • Backfilling and compaction is conducted after the wall 94 has been constructed to a height of 1.4m.
  • the second and each subsequent course of blocks 12 are constructed using the hollow blocks 12.
  • a length of strip reinforcement 18 is inserted 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 between the laid blocks 12 at face 30 and 24.
  • 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 14.
  • the hollow block 12 with the length of strip reinforcement 18 inserted is laid over the blocks forming the preceding course 14.
  • the cavities 72 of the hollow blocks 12 are filled with a quantity of ballast 76 in the form of a stabilized material, for example, concrete, or a permeable material, for example, drainage aggregate.
  • 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.
  • the aggregate helps to distribute the tensile forces acting on the strip reinforcement 18 over a greater surface area of the inside rear face 80 of the cavity 72.
  • the wall 94 is completed to a height of approximately 1.4m and backfilled using an appropriate stabilized soil and compacted.
  • 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 stabilized soil either after each course 14 is laid or when the wall 16 has been completed.
  • 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.
  • 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. 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.
  • a maximum height of approximately 1.4m height of wall 94 may be laid prior to backfilling.
  • the strips 48 and 74 extend horizontally from the rear of the wall 94 and are permitted to drape down under gravity during construction of the wall 94.
  • Prior to backfilling the strips 48 and 74 are bent upwards to clear the backfilling operations that typically may occur in one block 12 high layers to assist compaction.
  • the strips are 48 and 74 are laid onto the compacted stabilized soil as it rises.
  • the system 10 may further include a plurality of shear pins 82 illustrated in Figure 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.
  • 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.
  • 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.
  • strip reinforcement 18 it is equally possible to insert the strip reinforcement 18 through a plurality of blocks 12 in adjacent courses 14 as illustrated in Figure 2. 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 embankment backfill behind the stabilized mass being retained.
  • FIG. 4 A third embodiment of the reinforced soil retaining wall system 10 and blocks 12 of the present invention is illustrated in Figure 4 for which like reference numerals refer to like parts.
  • 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 stabilized 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.
  • 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
  • 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.
  • 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 0.6m below the final anticipated height of the composite wall 90.
  • 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.
  • 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.
  • 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.
  • FIG. 6 A fourth embodiment of the system 10 and blocks 12 of the present invention is illustrated in Figure 6 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.
  • 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.
  • 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.
  • 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.
  • the present invention has a number of advantages over the prior art, including the following: a) lightweight hollow blocks permit rapid installation and reduce the likelihood of work-related injury to the block laying crew; 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; 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, 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.
  • the use of stabilized soil behind the blocks reduces the width of the retaining wall by approximately 50% when compared to reinforced soil prior art methods.
  • stabilized soil provides greater frictional resistance to the strips than the unstabilised fill commonly used in reinforced earth methods.
  • the composite strength of the retaining wall is gained by bonding of the soil particles the length of the strip required to hold the wall to the mass is reduced, commonly to 750mm regardless of wall height.
  • the enhanced frictional resistance of the stabilized soil to the strip permits the wall to be constructed to any height without the use of props or supporting scaffolds.
  • stabilizers exist such as lime, cement, enzymes and polymers that permit soils such as silts to be used as the wall structure which are unsuitable in prior art methods
  • blocks of sufficient mass to be self supporting without attachment to the stabilized embankment can be used as the wall face. They may be oriented in header formation to provide shear strength across the interface of the wall and the stabilized embankment.
  • 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.
  • 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.
  • a panel could be applied onto a vertical or near vertical face cut into the formed embankment. 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.
  • 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.

Abstract

A retaining wall (16) having a backfill (20) stabilized by use of soil and a binder and optionally also by reinforcing strips (18).

Description

STABILISED EMBANKMENT
FIELD OF THE INVENTION The present invention relates to a stabilized backfill material, a wall may attached to the backfill material, and a method of constructing a bound embankment with a wall. The present invention further relates to a block used in the construction of a wall attached to stabilized embankment and a length of strip reinforcement used in the construction of a stabilized embankment attached to a wall:
The present application claims priority from Australian provisional patent application 2006906924 filed on 13 December 2006, Australian provisional patent application 2007900271 filed on 22 January 2007 and Australian provisional patent application 2007901585 filed on 27 March 2007.
BACKGROUND TO THE INVENTION
Embankments are defined as any artificial mound or bank of earth that restrains or confines material on one side to maintain a difference in elevation. Nearby slopes, roads, railways, driveways, buildings, and tiered walls all represent potential loads on embankments. Embankments consist of earth, gravel, stones and the like formed into an artificial raised elevation. They are used for such applications as dams, supporting loads such as roads and railways.
The present specification describes an embankment confining soil on one side, said embankment consisting of separate particles of granular material that have undergone a chemical process to cause them to bind together to act as one mass after placing.
Traditionally, granular materials will form a sloping side when placed due to the friction between the particles. When a vertical side is desired on one side of the embankment the present invention describes how a wall may be erected and the moist granular particles compacted against the wall. After the chemical reaction has occurred the wall serves no supporting function and may be removed or left in place. An application of such an invention would replace traditional retaining walls.
Retaining walls are known and are used to hold back soil or rock from a building, structure or other area. Retaining walls prevent down slope movement or erosion and provide support for sloping, vertical or near vertical grade changes.
Known retaining walls consist of a face wall, for example constructed of hollow masonry blocks, and backfill material behind the face wall for resisting, overturning and sliding of the face wall. The soil behind the face wall attempts to cause the face wall to rotate forward at its base away from the soil. The soil may also cause the face wall to slide forward.
There are several known methods used to resist these forces, all of which involve creating sufficient mass or geometrical width in the overall face wall and infill material. This can be achieved by increasing the wall width, with the wider section being at the base. It can also be achieved by attaching the face wall to steel or plastic soil reinforcements, for example, strips or sheets of mesh which are embedded into the infill material. In this arrangement, the wall and the reinforced soil behind the face wall become the effective retaining wall and resist the rotational forces.
In areas where local masonry (eg. Stone) is of sufficiently low price, it is commonly used as a gravity retaining wall to provide sufficient size and mass to resist the rotational forces. However, where such stone is not economically available, the lowest priced retaining wall is usually achieved by using soil reinforcement behind the face wall.
The costs associated with constructing a retaining wall include; excavation of the existing soil; construction of the wall face; and the soil reinforced backfilling behind the face wall. Such reinforced retaining walls can reduce the cost of the face wall significantly, but require additional excavation and backfilling, which each creates its own cost.
There are several disadvantages with existing retaining wall construction methods. Firstly, the required width of the reinforced soil mass may be more than height of the face wall and achieving the required width may not be possible due to rock or other structures being present behind the face wall. Some building sites also do not have enough room to temporarily store all of the excavated material during the retaining wall constπjction. Further, in some areas, excavation and back filling costs are uneconomic.
The width of the gravity retaining wall can be reduced by using heavy materials as the back fill material. This is commonly achieved by pouring concrete behind the wall. However, using concrete has disadvantages including: it is a very expensive material; and, whilst in its liquid state, can easily cause the face wall to be pushed out.
It is the object of the present invention to substantially overcome or at least ameliorate one or more of the above prior art disadvantages.
The term "stabilised embankment" and "stabilised soil" refers to a mass of particles, including clay, affected by a process by which the intrinsic properties of the embankment material are altered by the addition of a stabilisation binder to meet performance expectations in its operating, geological and climatic environment. In this invention it is the purpose of the binder to cause adherence between the particles that constitute the embankment to cause them to act in unison against forces imposed onto the embankment. Such forces may be sliding, overturning or shear. The embankment may incorporate substantially horizontal layers of soil reinforcement material buried within the stabilised soil to enhance the properties of the mass.
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
According to a first aspect of the present invention there is provided a stabilized soil embankment with a wall 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.
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.
Preferably each length of strip reinforcement is resiliently flexible.
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.
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.
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 or stabilized soil. The passage may be one of plurality of passages.
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.
In another embodiment, the plurality of lengths of strip reinforcement are divided into a section inserted into at least one block and a free section co-operatively associated with the inserted section and 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 of the stabilized or naturally stabilized soil.
According to a second aspect of the present invention there is provided a method of construction of a stabilized 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 stabilized 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 stabilized soil behind the rear face of the block.
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.
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 stabilized 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. 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, a stabilized material or poured concrete.
In yet another embodiment, the plurality of lengths of strip reinforcement are divided into a section inserted into at least one block at step (b) and a free section cooperatively associated with the inserted 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 of the stabilized soil.
According to a third aspect of the present invention there is provided a block for use in constructing the stabilized 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 stabilized soil retaining wall system according the method of the second aspect of the present invention.
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 stabilized soil. 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.
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.
According to a fifth aspect of the present invention there is provided a method of construction of a stabilized 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 stabilized embankment 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 embankment 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 stabilized 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.
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.
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.
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 stabilized soil. 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 stabilized soil.
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.
According to a sixth aspect of the present invention there is provided a method of construction of a stabilized soil retaining wall system, the system comprising a mass of stabilized soil formed in compacted layers with sloping sides formed by the friction angle of the unbound material. After the chemical reaction has formed a bound mass the side or a plurality of sides of the mass may be cut to a steeper angle. One angle that could be obtained is 90 degrees.
According to a seventh aspect of the present invention there is provided a method of construction of a stabilized 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 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, the mass of each block being sufficient to self support the wall without reinforcement.
In all described aspects of the present invention the stabilized mass may consist of: a) naturally occurring material that forms a bound mass upon compaction b) waste form an industrial process excluding the process of manufacture of iron or steel c) Clay combined with a stabilizing agent d) A mass of compactable material combined with an agent designed to promote the binding of the particles into a single bound mass. e) A mass of compactable material combined with an enzyme designed to promote the binding of the particles into a single bound mass.
The term "compaction" refers to the application of mechanical force to reduce the compressibility of the backfill, increase density and mitigate the risk of future movement of the embankment.
In all described aspects of the present invention the stabilized mass is formed by providing a layer of stabilized soil of sufficient thickness and moisture to permit the vibration from a compacting device to penetrate the layer to create sufficient density to provide a self supporting unconfined compressive strength. Another layer of stabilized soil is placed onto the compacted layer and compacted in the same procedure. The stabilized embankment consists of a plurality of these compacted layers of stabilized soil. A wall of sufficient mass to be self supporting or a wall attached to the stabilized embankment by way of reinforcement may be provided to create an alternative to a retaining wall or to prevent erosion of the face. Hence, this invention could also be described as a retaining wall to create an awareness of its purpose.
BRIEF DESCRIPTION OF THE DRAWINGS
In order to facilitate a more detailed understanding of the nature of the invention the stabilized soil embankment with attached masonry wall will be referred to as a retaining wall throughout this description.
In order to facilitate a more detailed understanding of the nature of the invention an embodiment of the retaining wall will now be described in detail, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an isometric view of a block used in accordance with a second embodiment of the stabilised soil retaining wall system of the present invention;
Figure 2 is a cross-sectional view through section B-B of the block illustrated in Figure 1 showing the arrangement of the length of strip reinforcement inserted into the block; Figure 3 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; Figure 4 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;
Figure 5 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;
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
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.
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 stabilized material, typically stabilized soil that is placed on the retained side of the wall. Loose backfill can add to the load on the retaining wall, allows water to collect and causes settlement problems. All stabilized soil 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.
"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.
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".
The term "geomesh" is used throughout this specification to describe soil reinforcement in the form of strips of a polymeric material.
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 stabilized soil retaining wall using the hollow blocks 12 will now be described with reference to Figures 1 to 3. It is to be understood that the stabilized soil retaining wall system is equally adaptable to construction using mortar in an analogous manner as described with respect to the first embodiment of the present invention.
During construction of the wall 94 using the hollow blocks 12, the foundation 60 and the base course 62 are laid with the base course 62 being laid onto the foundation 60. Backfilling and compaction is conducted after the wall 94 has been constructed to a height of 1.4m.
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 Figure 2, a length of strip reinforcement 18 is inserted 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 between the laid blocks 12 at face 30 and 24. 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 14.
The hollow block 12 with the length of strip reinforcement 18 inserted is laid over the blocks forming the preceding course 14. 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 a stabilized material, for example, concrete, or a permeable material, for example, drainage aggregate. 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 of the inside rear face 80 of the cavity 72.
After the hollow cavities 72 have been filled with the quantity of ballast 76, the wall 94 is completed to a height of approximately 1.4m and backfilled using an appropriate stabilized soil and compacted. Immediately prior to backfilling behind 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 stabilized soil either after each course 14 is laid or when the wall 16 has been completed.
With reference to Figures 2 and 3, 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. 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. For safety purposes a maximum height of approximately 1.4m height of wall 94 may be laid prior to backfilling. In such a case the strips 48 and 74 extend horizontally from the rear of the wall 94 and are permitted to drape down under gravity during construction of the wall 94. Prior to backfilling the strips 48 and 74 are bent upwards to clear the backfilling operations that typically may occur in one block 12 high layers to assist compaction. The strips are 48 and 74 are laid onto the compacted stabilized soil as it rises.
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 Figure 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.
It is equally possible to insert the strip reinforcement 18 through a plurality of blocks 12 in adjacent courses 14 as illustrated in Figure 2. 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 embankment backfill behind the stabilized mass being retained.
A third embodiment of the reinforced soil retaining wall system 10 and blocks 12 of the present invention is illustrated in Figure 4 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 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 stabilized 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.
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.
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 0.6m below the final anticipated height of the composite wall 90.
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.
A fourth embodiment of the system 10 and blocks 12 of the present invention is illustrated in Figure 6 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.
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.
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.
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: a) lightweight hollow blocks permit rapid installation and reduce the likelihood of work-related injury to the block laying crew; 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; 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, 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. e) the use of stabilized soil behind the blocks reduces the width of the retaining wall by approximately 50% when compared to reinforced soil prior art methods. f) stabilized soil provides greater frictional resistance to the strips than the unstabilised fill commonly used in reinforced earth methods. g) as the composite strength of the retaining wall is gained by bonding of the soil particles the length of the strip required to hold the wall to the mass is reduced, commonly to 750mm regardless of wall height. h) the enhanced frictional resistance of the stabilized soil to the strip permits the wall to be constructed to any height without the use of props or supporting scaffolds. i) a wide variety of stabilizers exist such as lime, cement, enzymes and polymers that permit soils such as silts to be used as the wall structure which are unsuitable in prior art methods j) blocks of sufficient mass to be self supporting without attachment to the stabilized embankment can be used as the wall face. They may be oriented in header formation to provide shear strength across the interface of the wall and the stabilized embankment. 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. Also, a panel could be applied onto a vertical or near vertical face cut into the formed embankment. 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.

Claims

Claims defining the Invention:
1. A stabilized 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 to the stabilized soil mass, 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 of the stabilized soil mass.
2. The stabilized 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 stabilized soil retaining wall system of claim 1 or 2 wherein each length of strip reinforcement is resiliently flexible.
4. The stabilized soil retaining wall system of any one of claims 1 to 3 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.
5. The stabilized soil retaining wall system of any one of claims 1 to 4 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.
6. The stabilized soil retaining wall system of claim 5 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.
7. The stabilized soil retaining wall system of claim 6 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.
8. The stabilized soil retaining wall system of any one of claims 1 to 7 wherein the passage is a cavity extending from the bottom surface to the top surface, the cavity configured to receive a quantity of ballast.
9. The stabilized soil retaining wall system of claim 1 wherein the ballast is drainage aggregate.
10. The stabilized soil retaining wall system of claim 1 wherein the ballast is impermeable.
11. The stabilized soil retaining wall system of claim 1 wherein the ballast is stabilized soil.
12. The stabilized soil retaining wall system of any one of claims 1 to 11 wherein the passage is one of plurality of passages.
13. The stabilized soil retaining wall system of any one of claims 1 to 12 further comprising one or more shear pins to resist sliding movement of a first course over an adjacent second course.
14. The stabilized soil retaining wall system of any one of claims 1 to 14 forming a lower section of a composite wall, the composite wall being divided a transition depth into an upper section and the lower section
15. The stabilized soil retaining wall system of claim 14 wherein the upper section is a gravity retaining wall.
16. The stabilized soil retaining wall system of claim 14 or 15 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.
17. The stabilized soil retaining wall system of claim 15 wherein the soil reinforcement protection barrier is a concrete slab.
18. A method of construction of a stabilized 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 stabilized 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 stabilized soil behind the rear face of the block.
19. The method of construction of claim 18 wherein step (e) is conducted after step (c) after each course is completed.
20. The method of construction of any one of claims 18 to 19 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).
21. The method of construction of any one of claims 18 to 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.
22. The method of construction of claim 18 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 stabilized soil behind the rear face of the block.
23. The method of construction of claim 19 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.
24. The method of construction of any one of claims 18 to 23 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.
25. The method of construction of claim 24 wherein the ballast is drainage aggregate.
26. The method of construction of claim 24 wherein the ballast is impermeable.
27. The method of construction of claim 24 wherein the ballast is stabilised.
28. The method of construction of any one of claims 18 to 27 further comprising the step of installing one or more shear pins to resist sliding movement of a first course over an adjacent second course.
29. The method of construction of any one of claims 18 to 28 wherein the plurality of lengths of strip reinforcement are divided into a section inserted into at least one block at step (b) and a free section co-operatively associated with the inserted 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.
30. The method of construction of any one of claims 18 to 29 wherein the stabilized 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.
31. The method of construction of claim 30 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.
32. The method of construction of claim 31 wherein the step of installing a soil reinforcement protection barrier comprises the step of laying a concrete slab.
33. A block for use in constructing the stabilized soil retaining wall system of any one of claims 1 to 32.
34 A length of strip reinforcement for use in constructing the stabilized soil retaining wall system of any one of claims 1 to 32.
35. A stabilized soil retaining wall system substantially as herein described with reference to and as illustrated in the accompanying illustrations.
36. A method of construction of a stabilized soil retaining wall system substantially as herein described with reference to and as illustrated in the accompanying illustrations.
37. A block for use in the construction of a stabilized soil retaining wall system substantially as herein described with reference to and as illustrated in the accompanying illustrations.
38 A length of strip reinforcement for use in the construction of a stabilized soil retaining wall system substantially as herein described with reference to and as illustrated in the accompanying illustrations.
39 Retaining wall backfill material comprising particles and stabilizer.
40 Retaining wall backfill material comprising particles, stabilizer and added water.
41 A retaining wall backfill material comprising particles, stabilizer and water added at the location of placement of the particles.
42 A retaining wall backfill material of any one of claims 39 to 41 wherein the material is a granular material.
43 A retaining wall backfill material of any one of claims 39 to 42 wherein the granular material has a range of particle sizes.
44 A retaining wall backfill material of any one of claims 39 to 43 wherein the granular material has a range of particle sizes from dust to pass through a 40mm mesh. 45 A retaining wall backfill material of any one of the preceding claims wherein the material has water added thereto
46 A retaining wall, the retaining wall comprising a wall face and a stabilized backfill material.
47 The retaining wall of claim 46, wherein the material is a granular material.
48 The retaining wall of claim 46, wherein the granular material has a range of particle sizes.
49 The retaining wall of claim 46, wherein the granular material has a range of particle sizes from dust to pass through a 40mm mesh. 50 The retaining wall of any one of claims 46 to 49, wherein the material has water added thereto.
51 The retaining wall of any one of claims 46 to 49, wherein the material has water added thereto.
52 The retaining wall of any one of claims 46 to 49, wherein the retaining wall includes soil reinforcements extending between the face wall and the backfill material.
53 The retaining wall of any one of claims 46 to 49, wherein the retaining wall includes a layer of stones between the face and the stabilized backfill material.
54 The retaining wall of any one of claims 46 to 49, wherein the retaining wall includes a layer of substantially uniformly sized stones between the face and the stabilized backfill material.
55 The retaining wall of any one of claims 46 to 49, wherein the retaining wall includes a layer of stones between the stabilized backfill material and the retained embankment. 56 The retaining wall of any one of claims 46 to 49, wherein the retaining wall includes a layer of substantially uniformly sized stones between the stabilized backfill material and the retained embankment.
57 A method of constructing a retaining wall, the method comprising the steps of: a) constructing a face wall- and b) adding a backfill material adjacent the face wall, the backfill material comprising an added stabilizer
58 The method of claim 57, wherein the method also includes adding the backfill material' in layers
59 The method of claim 57, wherein the method also includes compacting each of the layers before adding another layer of the layers atop thereof
60 The method of claim 58, wherein the method also includes adding water to the backfill material. 61 The method of claim 59, wherein the method also includes adding water to each of the layers before adding another of the layers atop thereof.
62 The methods of claims 57 to 61 , wherein the method also includes adding soil reinforcements extending between the face wall and the backfill material
63 A method of constructing a retaining wall, the method comprising the steps of: a) constructing a face wall; and b) adding a backfill material adjacent the face wall, the backfill material possessing a natural cementacious characteristic that does not include product from the process of the manufacture of iron and steel.
64 The method of claim 63, wherein the method also includes adding the backfill material in layers
65 The method of claim 63, wherein the method also includes compacting each of the layers before adding another layer of the layers atop thereof
66 The method of claim 64, wherein the method also includes adding water to the backfill material. 67 The method of claim 65, wherein the method also includes adding water to each of the layers before adding another of the layers atop thereof.
68 The methods of claims 63 to 67, wherein the method also includes adding soil reinforcements extending between the face wall and the backfill material
69 The method of any one of the claims 57 to 68, wherein the stabilized material is granular
70 The method of any one of the claims 57 to 68, wherein the stabilized granular material has a range of particle sizes
71 The method of any one of the claims 57 to 68, wherein the stabilized granular material has a range of particle sizes from dust to pass through a 40mm mesh. 72 A type of retaining wall consisting of a granular material being stabilized said granular material comprising a plurality of particle sizes.
73 A method of constructing a gravity retaining wall comprising the stabilized material not including the product of iron and steel manufacture whereby; the stabilized material is compacted in layers; and moisture is added where it contributes to compaction to form a self supporting structure.
74 A method of constructing a gravity retaining wall consisting of stabilized material not including the product of iron and steel manufacture in conjunction with other materials also not a product of iron and steel manufacture
75 A method of constructing a soil reinforced retaining wall comprising a face wall and reinforced mass consisting of stabilized material not including the product of iron and steel manufacture
PCT/AU2007/001915 2006-12-13 2007-12-12 Stabilised embankment WO2008070913A1 (en)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
AU2006906924 2006-12-13
AU2006906924A AU2006906924A0 (en) 2006-12-13 Improved retaining walls
AU2007900271 2007-01-22
AU2007900271A AU2007900271A0 (en) 2007-01-22 Improved retaining wall
AU2007901585 2007-03-27
AU2007901585A AU2007901585A0 (en) 2007-03-27 Improved retaining wall

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