WO2001046526A1

WO2001046526A1 - Earth retention and piling systems

Info

Publication number: WO2001046526A1
Application number: PCT/AU2000/001600
Authority: WO
Inventors: Ian Robert Macdonald
Original assignee: Tristanagh Pty. Ltd.
Priority date: 1999-12-21
Filing date: 2000-12-21
Publication date: 2001-06-28
Also published as: AU2005200758A1; AU2492701A; AUPQ479699A0; AU2004101058A4; AU2008243212A1; AU2007100294A5

Abstract

A method of stabilisation and confinement of earth structures including the steps of: (a) excavating an earth structure to a predetermined depth; (b) inserting earth anchors (76) into a wall structure formed by excavation; (c) tensioning each of said earth anchors (76) to a required value against bearing members (74) lying against the surface of the wall structure; (d) interconnecting the exposed ends of selected earth anchors with reinforcing members; and, (e) applying a sprayable cementitious composition to the wall surface to encapsulate part or all of said reinforcing members.

Description

EARTH RETENTION AND PILING SYSTEMS

FIELD OF THE INVENTION THIS INVENTION relates to methods of soil stabilization. The invention also relates to the apparatus for effecting the methods, and to soil structures stabilized by the methods. BACKGROUND OF THE INVENTION

Unstable soil structures, eg., comprising sand, clay, shale and/or broken rock, must be stabilized if they are to provide good foundations for building constructions. Similarly, the structures must be stabilized where exposed wall areas are formed by excavation, eg., in open cut mines, mineshafts, and during the construction of building basements.

One excavation technique has used sheet piling and this has proved particularly successful in sandy or otherwise softer class soils. This technique is described in Australian Patent No. 631 365. The techniques to date have been primarily "passive" stabilization techniques designed to prevent localized collapsing of earth from the face of an exposed excavation wall. Over a period of time, however, subsidence can occur behind a passive retaining structure with consequent risks to the integrity of any building structure thereon.

In hard rock excavations such as underground mine shafts, it is common to stabilize and confine roof structures against collapse by the use of tensioned rock bolts which are anchored in boreholes by mechanical means and/or chemical or cementitious grouts. The anchors are spaced such that when tensioned, respective zones of compression in the rock mass overlap to form dynamic structural "beams" which are supported by the earth masses of opposing walls.

Where the rock mass is highly fractured, it is customary to employ steel "W" straps with rock bolts to spread the compressive load applied when the rock bolts are tensioned .

To restrain collapse of the rock walls in such mine shafts, a layer of steel mesh may be secured to the wall surface at intervals with rock bolts and then the wall surface is sprayed with "Shotcrete" to form a steel reinforced concrete shell. The rock bolts are inserted in the walls at much greater spacings than the roof as their purpose is merely to support the steel mesh and not to form overlapping zones of compression.

Other non-tensioned passive retaining systems are described in Australian patent applications 91 307/82 and 1 601 5/83 and Australian patent 571 856 which all describe a form of "stitching" of earth structures with non-tensioned elements. While certain aspects of the present invention are concerned primarily with stabilization and confinement of upright earth wall surfaces in open excavations, of softer earth, it is considered to be applicable in harder rock formations in certain instances.

Major problems associated with stabilization and confinement of excavation walls are the installation cost and bulk of the wall structure. One structurally effective method for stabilization and confinement of excavated earth walls is the so-called continuous piling system. This system requires the drilling of overlapping bores to a required depth about the perimeter of a side and filling the bores with concrete to form a continuous concrete wall which, when cured, enable the earth contained within to be safety excavated.

The main problem with this system, apart from cost, is that it is usually not possible to form the boreholes at the site boundary due to adjacent structures and thus the boreholes are located from 250-500mm within the boundary. After excavation, it is then necessary to erect an internal wall, spaced from the continuous piling to comply with hydrological requirements.

With such systems, an effective loss of usable space of up to 1 metre thick can occur around the boundary of the site.

Another commonly employed shoring system utilizes spaced soldier piles anchored to the earth formation with timber or otherwise shuttering extending therebetween. This system is often a temporary structure which must subsequently be replaced with say a

"Shotcrete" skin and a spaced internal wall - again with a substantial loss of useable space.

A compact system for stabilization and confinement of the walls of open excavations is described in Australian Patent Application No. 52382/86. In this system, elongate U-shaped members formed from steel rod are inserted free ends first into bore holes in a short wall formed in a first stage of excavation. The U- shaped members are full column grouted in their respective bore holes and the looped end of the U-shaped member is then bent through 90° to lie against the surface of the wall. A further bore hole is then formed in the earth wall within the looped end of the U-shaped member and one or more further U-shaped members are then inserted into the bore hole and are full column grouted . This process is repeated to form a mesh-like array of interconnected U-shaped members which are then sprayed with Shotcrete to form a steel reinforced skin.

Unlike the roof structure of a hard rock mine with reinforcing tensioned rock bolts, all of these prior art systems are passive in that they only react to resist collapse of an earth wall when localized outburst pressures due to subsidence or hydraulic pressures in wet clay occur.

The major problem associated with such passive systems is that they cannot be employed adjacent existing building structures due to the risk of subsidence in the earth structure supporting the existing building structure.

In all such passive systems, either localized or generalized subsidence will occur as the support structure takes up the subsidence pressures. In a typical excavation of say 30-40 metres in depth, the first 5-1 0 metres of excavation may occur in a layer of soft sand or clay soil. The sandy or clay layer may then overlay a more stable earth layer of cemented "coffee rock" or a stiffer clay/shale. This layer in turn may be supported on a much more stable shale or weathered bedrock layer. Accordingly, the risk of subsidence and/or collapse of the excavation wall is much greater in the upper layer of excavated earth than in the lower layers.

In sandy or unstable clay earth formations, it is common practice to employ sheet piling with earth anchors as a means of passive stabilization and confinement. While generally effective for its intended purpose, it is not always possible to employ sheet piling immediately adjacent the boundary of an existing building structure as the vibratory forces associated with driving the sheet piling into the earth formation can cause subsidence under the building structure. Moreover, it is frequently impossible to use earth anchors to anchor the sheet piling as much anchors would extend beyond the boundaries of the block being excavated into the adjoining property.

The present invention aims to provide useful and effective alternatives to prior art systems for stabilization and confinement of excavated earth structures to provide improved foundation systems for building structure.

SUMMARY OF THE INVENTION According to one aspect of the invention, there is provided a method of stabilization and confinement of excavated earth structures, said method comprising the steps of:

(a) excavating an earth structure to a predetermined depth; (b) inserting earth anchors into a wall structure formed by excavation;

(c) tensioning each of said earth anchors to a required value against bearing members lying against the surface of the wall structure; (d) interconnecting the exposed ends of selected earth anchors with reinforcing members; and

(e) applying a sprayable cementitious composition to the wall surface to encapsulate part or all of said reinforcing members. Suitably said boreholes are spaced at intervals such that when said earth anchors are tensioned, respective zones of compression associated with said bearing members overlap to form a compressed earth structure in the region of the exposed earth surface.

If required, the earth anchors may be grouted into the earth formation. A form of "deadman" anchor and/or a full column grouted anchor. The reinforcing members may comprise steel rods and/or cable and/or steel reinforcing mesh or any combination thereof.

The steel rods and/or cable may be connected between adjacent anchors in columns, rows or a mesh array.

Suitably, the sprayable cementitious composition may include reinforcing fibres.

If required, the bearing members may comprise steel plates adapted to receivably locate said steel rods and/or cable and/or mesh.

If required, the steel rods and/or cable and/or mesh may be secured to said bearing plates by clamping means or by welding .

The bearing members associated with at least some of said earth anchors may comprise spaced soldier piles or sheet piles.

Preferably, the soldier piles or sheet piles are arranged as spaced pairs. If required, the bearing members may be selected members of a continuous sheet piling system.

Preferably, the sheet piles comprise at least partially flexible sheet piles. If required, the reinforcing rods are pretensioned before the reinforcing mesh is mounted thereon, or before the concrete is sprayed.

The reinforcing rods may be provided to interconnect the anchor in columns and/or rows and/or diagonally.

By using soldier piles or sheet piles, engaged by the anchors, the number of anchors required to stabilize and strengthen a particular soil structure may be substantially reduced, eg., by up to 50% . If required, steps (a)-(f) may be repeated until the excavation has reached a required depth.

In an alternative embodiment, the exposed ends of selected earth anchors in a first excavation step are interconnected with reinforcing means to form a mesh like array and in one or more subsequent excavation steps, the exposed ends of selected earth anchors are interconnected with reinforcing means in rows, columns or diagonally.

In yet another embodiment, anchored sheet piling may be employed to stabilize and confine a second or subsequent excavation step.

According to yet another embodiment of the invention, there is provided a method of stabilizing and confining earth structures to be excavated, said method comprising the steps of: (a) locating a plurality of pile members in said earth structure;

(b) conducting a first excavation step to a desired depth; (c) anchoring said pile members to the earth structure therebehind with earth anchors;

(d) connecting exposed ends of selected earth anchors with reinforcing means;

(e) conducting a further excavation step to a desired depth; and

(f) repeating steps (c) , (d) and (e) until a desired excavation depth is reached .

The pile members may form spaced or continuous sheet piling. Suitably, the pile members are located in the earth structure are spaced, eg ., as spaced pairs, each said spaced pair being spaced from an adjacent spaced pair by a distance greater than the spacing between a spaced pair of pile members.

The spaced pile members may comprise steel sheet piling members with earth anchors extending into the earth structure via apertures in said sheet piling members.

Preferably, the sheet piling members are flexible sheet piles. Alternatively, the spaced pile members may comprise reinforced concrete piles formed in situ in spaced boreholes in the earth structure, the spaced concrete piles being anchored to the earth structure by an earth anchor connected to a saddle member extending between spaced pairs of concrete piles.

Suitably, the earth anchors are tensioned to a predetermined value to induce compression in the earth structure behind said spaced pile members.

Preferably, the earth anchors are relatively positioned such that when tensioned, regions of compression in the earth structure, associated at least with adjacent pile members, overlap to form a reinforced earth structure.

If required, the reinforcing members extending between exposed ends of selected earth anchors may be tensioned to a predetermined value after said earth anchors are tensioned.

The reinforcing members may comprise steel rods, cable, mesh or any combination thereof.

Suitably, the earth anchors are grouted in respective boreholes with a cementitious composition to form a "deadman" and/or a full column grout anchor.

Preferably, the stabilizing and confining structure, after tensioning of the earth anchors and placement of the reinforcing means is sprayed with a flowable cementitious composition to encapsulate the reinforcing members.

Most preferably, the flowable cementitious composition includes reinforcing fibres of steel, glass polymeric material or any combination thereof. If required, a layer of resiliently deformable material may be applied to the exposed earth wall surface prior to interconnection of the free ends of exposed earth anchors to form a compressible barrier between the exposed earth wall surface and a subsequently applied layer of cementitious composition encapsulating said reinforcing means.

In an alternative embodiment, a blinding layer of sprayable concrete is applied to the exposed earth wall surface prior to placement of the resiliently deformable material and/or a subsequent layer of cementitious composition encapsulating said reinforcing material.

In still another embodiment of the invention, boreholes for anchoring of pile members are formed simultaneously by two or more spaced drilling bits.

If required, the lower ends of the stabilizing and confining structure may be connected to footings formed in the base of the excavation and a load bearing structural wall may be formed by spraying the surface of the stabilizing and confining structure so formed with a suitable cementitious composition and subsequently screeding the sprayed surface to form a smooth wall.

According to a still further embodiment of the invention, there is provided a method of stabilizing and confining earth structures to be excavated, said method comprising the steps of: (a) locating to a desired depth a plurality of adjacent sheet pile members in said earth structure;

(b) locating, at spaced intervals against a su rface to be exposed of said pile members, soldier piles having respective lower ends at a depth greater than lower ends of said piling members; (c) conducting a first excavation step to a desired depth;

(d) conducting a further excavation step to a desired depth;

(e) anchoring said soldier piles to the earth structure therebehind with earth anchors below the lower ends of said sheet pile members; and, if required

(f) repeating steps (d) and (e) until a desired excavation depth is achieved .

Suitably said soldier piles comprise hollow tubular piles. Alternatively said soldier piles comprise longitudinally apertured elongate members forming a closed tubular member when positioned against a sheet pile member.

Preferably said soldier piles are driven into the earth formation whereby a quantity of earth occupies at least portion of the hollow interior thereof.

If required, the quantity of earth located within the soldier pile may be removed and replaced with a curable cementitious material.

Suitably the soldier piles are driven into the earth formation to contact a bed rock foundation.

Alternatively the soldier piles are driven into the earth formation such that respective lower ends thereof are located above a bed rock foundation and a mass of flowable curable cementitious material is pumped under pressure into the hollow interior thereof whereby a mass of cementitious curable material emerges from the respective lower ends of the soldier piles to form a footing or foundation therefor. Suitably reinforcing members may extend between the interior of said soldier piles and respective footings or foundations therefor.

Alternatively, when a soldier pile is driven into contact with a bed rock foundation, a lower portion of the hollow interior thereof may be filled with compacted sand or earth and an upper portion -thereof filled- with a curable cementitious composition- having reinforcing elements extending upwardly therefrom.

If required the soldier piles may comprise discrete elongate members axially joined by joining members.

Suitably the exposed regions between adjacent soldier piles include reinforcing members and/or mesh embedded in a sprayable curable cementitious material to form walers and/or blinder walls.

The soldier piles may be secured to the sheet pile members by welding and/or by bolting.

If required, a reinforced concrete bond beam may be formed along the top of the sheet piling structure as a structural foundation for a building structure to be supported thereon.

According to a modified form of the invention, there is provided a method of installation of load bearing piles in an earth formation, said method comprising the steps of:- locating along an upright longitudinal axis into an earth formation an elongate hollow pile member open at both ends thereof; supporting said hollow pile member on a footing or foundation; and filling at least an upper portion of said hollow pile member with a curable cementitious material to encase reinforcing members extending upwardly from an upper end of said hollow pile member.

If required said hollow pile member may be driven into said earth formation until it contacts a bedrock formation. Alternatively the hollow pile may be driven into an earth formation with a lower end of said pile spaced above a bedrock formation and then after removing earth from the interior of the hollow pile, a flowable curable cementitious material is pumped into the hollow interior of the hollow pile under pressure whereby a quantity of the cementitious material emerges from the lower end of the pile to form a footing or foundation therefor.

The bearing pile may comprise a plurality of hollow members joined axially by jointing members. If required the bearing pile may comprise elongate elements joined longitudinally to form an elongate hollow member.

The bearing pile may be of any suitable cross sectional shape selected from circular, rectangular or polygonal.

Suitably the bearing piles comprise a steel reinforced cementitious core.

Preferably the bearing piles include a plurality of spaced substantially parallel elongate steel reinforcing members extending substantially over the length of thereof, said steel reinforcing members being encapsulated in a curable cementitious composition. If required the bearing piles may include ground anchor means.

Suitably the ground anchor means comprises an anchor member coupled to an elongate tensionable anchor rod, the anchor member in use being anchored in an earth formation below a lower end of a bearing pile with said anchor rod extending through the hollow interior thereof.

Preferably the anchor rod is surrounded by a curable cementitious composition.

According to yet another aspect of the invention there is provided a method of anchoring a pile in an earth formation, the method comprising the steps of:- forming first upright borehole in an earth formation; encapsulating, in said first borehole in a mass of flowable curable cementitious composition, a steel reinforcing member; allowing the cementitious material to at least partially cure to form a cementitious column; forming a further borehole substantially along an upright central axis of said column, said borehole extending through said column into an earth formation thereunder; inserting through said further borehole into the earth formation thereunder a mechanical earth anchor having an anchor rod extending from an upper opening of said borehole and pretensioning said anchor rod to engage said earth anchor with the earth formation; inserting into at least a lower portion of said further borehole a further mass of flowable curable cementitious material and allowing said further mass of cementitious material to at least partially cure.

Preferably said fast borehole extends to a bedrock layer in said earth formation.

If required said first borehole may include a first casing . Where said first borehole does not extend to a bedrock layer an enlarged cavity may be formed below a lower end of said first borehole, said cavity in use being adapted to be filled with a flowable curable cementitious material which when cured forms a foundation member. If required said earth anchor may be anchored in said foundation member.

Alternatively said earth anchor may be anchored in an earth formation below said foundation member.

The steel reinforcing member suitably comprises a plurality of elongate substantially parallel steel rods.

Preferably said plurality of parallel steel rods are separated by spacers to form a cage-like element having a central aperture extending longitudinally thereof.

If required, the steel reinforcing member may be placed in the first borehole prior to introduction of cementitious material.

Preferably the steel reinforcing member is inserted in the first borehole after introduction of the flowable cementitious material.

Preferably the further borehole is entirely filled with cementitious material to form an integral steel reinforced column.

According to a still further aspect of the invention there is provided a building structure supported on anchored pilings formed according to the abovementioned method steps. The building structure may extend wholly above a ground surface or it may include a buoyant portion located below said ground surface.

Alternatively, the building structure may comprise a buoyant structure located substantially below a ground surface. The buoyant structure may be anchored in an earth formation by anchored piles extending below a floor surface thereof and/or anchored piles extending to a ground surface.

In each of the piling aspects of the invention described above wherein a curable cementitious composition is incorporated in a pile column, fibre reinforcing may be employed.

Yet another aspect of the invention resides in a laminated sheet pile member comprising :- a first sheet pile member of predetermined length; and, at least one further sheet pile member laminated thereto, said further sheet pile member having a lower end adjacent a lower end of said first sheet pile member and an upper end located intermediate the opposed ends of said fist sheet pile member.

If required said laminated sheet pile member may include another sheet pile member laminated to said further sheet pile member, said another sheet pile member having a lower end adjacent a lower end of said further sheet pile member and an upper end intermediate the opposed ends of said further sheet pile member. Preferably respective ends of said first sheet pile member and said at least one further sheet pile member are offset to form a tapered edge on said laminated sheet pile member.

Sheet pile members forming the laminated member may be joined by any suitable process such as edge welding, plug welding, mechanical fasteners, adhesives or the like or any combination thereof.

Preferably the laminated sheet pile member is corrosion resistant.

The sheet pile members may be planar or contoured. If required the sheet pile members may be selected from steel, synthetic resin, fibre reinforced synthetic resin or any combination thereof.

Still further aspects of the invention include apparatus for stabilizing and confining earth excavations, and earth excavations whenever confined and stabilized according to the various aspects of the invention.

As used herein, the term "flexible" as applied to sheet piling means sheet piling capable of deformation at least to a limited degree in both a longitudinal and transverse direction when earth anchors connected thereto are tensioned, the deformation in the sheet piling members causing localized compression in an earth structure therebehind. The flexible sheet piling system is adapted to adjust or compensate for regions of differing compressibility in an earth structure.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the various aspects of the invention may be more fully understood and put into practical effect, a number of preferred embodiments will- be described with reference to the accompanying drawings, in which:

FIG 1 shows schematically compression load distribution in a sheet piling wall;

FIG 2 shows a matrix of interconnected earth anchors according to one embodiment;

FIG 3 shows a bearing plate for interconnecting earth anchors;

FIG 4 shows another embodiment of the invention;

FIG 5 shows a method of tensioning reinforcing members connecting the free ends of earth anchors.

FIG 6 shows a partial view of a soldier pile and jointing element according to one aspect of the invention.

FIG 7 shows a bearing pile assembly according to another aspect of the invention.

FIG 8 shows a wall pile according to yet another aspect of the invention.

FIG 9 shows an excavation according to one method of the invention.

FIG 10 shows an excavation according to another method of the invention.

FIG 1 1 shows a laminated sheet pile according to a further aspect of the invention. FIG 1 2 shows an anchored pile according to a still further aspect of the invention.

FIGS 1 3 and 1 4 show applications of anchored piles.

FIG 1 5 shows a cross sectional view of test configurations for ultimate load capacity on single, double and triple sheet assemblies.

FIGS 1 6-1 9 show load vs deflection curves for the test configurations of FIG 1 5.

FIG 20 shows a bond beam construction.

DETAILED DESCRIPTION OF THE DRAWINGS In FIG 1 , a plurality of contoured sheet piles 1 are first driven into an earth mass to a required depth to form a sheet steel barrier which is reinforced by the longitudinal contours. Overlapping edge flanges may be bolted together for extra strength if required . However, the interlocking ribs and channels usually provide sufficient interconnection.

Through apertures formed in the sheet piling members, boreholes are formed in the earth structure 2 there behind. Depending upon the earth structure, an appropriate sand clay or shale anchor head 3 supported on a rigid steel rod 4 is inserted into the borehole.

A bearing plate 5, contoured to locate against the outer surface of the sheet piling member 1 and having a small slotted aperture to receive the free end 6 of the anchor rod 4 is placed over the anchor rod to abut the sheet piling member and form a closure to the aperture through which the head 3 of the anchor was inserted into the borehole.

A tapered washer (not shown) is then placed over the anchor rod to accommodate a downward and rearward insertion angle and then a nut 7 is tensioned to a predetermined torque on the threaded end of the anchor rod to engage the anchor head 3 in the earth structure and to induce compression in the earth structure between the region of the anchor head and the sheet piling . In some cases, a mass of cementitious grout is pumped into the region of anchor head 3 to form a "deadman" 8 which provides greater anchorage in, for example, soft sandy soils. In this case, the anchor is pre-tensioned to, say 40-60kN to locate the anchor head and then the tension is released . When the grout is partially cured, tensioned is re-applied to about 40-60 kN and then post tensioned to a desired value of between 60-1 20 kN when the grout has substantially cured . It has been found that by using the geomechanical survey information normally required to determine slip planes and thus the depth of the anchor placement, it is possible to calculate the notional boundaries of compressed earth regions in the earth structure. This information enables the calculation of anchor spacings and anchor nut torques to create an analogous situation with the reinforcement of hard rock roof structures in mine shafts or tunnels with mine roof bolts.

By careful calculation of anchor spacings and anchor nut torques, it is possible to create overlap between regions of compression 9 in the earth structure of adjacent anchors in the vicinity of the anchor heads and the sheet piling barrier where the anchor rod passes through.

This dynamic structure creates spaced bands of compressed earth structure which serve to reinforce the earth structure adjacent an excavation and otherwise to assist in its confinement.

Unlike a mine roof/bolt which creates a zone of compression over its entire length, the anchor bolts induce zones of compression adjacent its opposed ends with a region of un affected earth therebetween. Moreover, while mine roof bolts form a stressed "beam" which extends transversely of a shaft, that "beam" is structurally supported by passive earth masses in the shaft walls.

In a typically rectangular excavation aperture, the method according to the invention forms an upright rectangular boundary of earth reinforced by continuous compression throughout but otherwise confined by the sheet piling against movement. This dynamic structure is particularly important in soft sandy soils which are prone to subsidence or hydraulic clay soils which are subjected to expansion or contraction depending on water content.

The flexible sheet piling described above can be reinforced further by the subsequent connection of reinforcing rods across the exposed face of the continuous sheet piling structure. The reinforcing rods may be attached to the sheet piles and/or the anchor ends in any suitable manner, eg ., by welding, brackets or the like.

After say spaced horizontal reinforcing rods are attached across the face of the sheet piling, bands of Shotcrete or the like may be sprayed over the rods to encapsulate them to form spaced reinforced concrete walers across the exposed surface of the sheet piling structure. Instead of or in addition to the spaced horizontal reinforcing rods, steel reinforcing mesh, vertical and/or inclined reinforcing rods may be employed .

It is considered a particular advantage of the present invention to use sheet piling having substantially uniform generally

"V" shaped ribs and troughs to aid in substantially even distribution of compressive forces throughout the compressed earth layer adjacent the sheet piling .

FIG 2 shows an alternative embodiment of the invention which is suitable both for soft unstable earth masses or relatively stable earth masses.

In certain circumstances, it is not possible to use the above method in stabilization and confinement of an earth excavation where the excavation site is immediately adjacent an existing building structure supported on a highly unstable earth mass. In such circumstances, the mere vibration of the sheet piles into the ground can cause subsidence under the existing building structure before excavation commences, let alone before the earth mass may be stabilized by compression. In the circumstances, it has been discovered that it is possible to excavate to a depth of 1 -1 .5 metres and then insert a row of tensioned earth anchors 1 0 at predetermined spacings.

Excavation is then continued for a further 1 -1 .5 metres and a second row of tensioned earth anchors are inserted at appropriate spacings.

After excavation, a further depth of about 1 -1 .5 metres and inserting tensioned earth anchors, steel reinforcing rods 1 1 are connected between the free ends of the anchor rods. Optionally, a layer of steel reinforcing mesh (not shown) is then secured over the mesh-like structure of reinforcing rods.

Shotcrete containing polypropylene fibre reinforcing is then sprayed over the structure to encapsulate the reinforcing members attached to the free ends of the anchor rods.

Once the upper unstable earth layer has been confined and reinforced, it may then be possible to drive sheet piling down to a desired depth in a conventional manner without fear of subsidence of an adjacent earth mass. Alternatively, as shown, the excavation in the more stable earth mass may be continued for a further 3-4 metres and tensioned earth anchors may be inserted at the same or different spacings as those above and they may be tensioned by the same of different nut torque depending upon the geomechanics of the subsequent earth layer.

In all cases, the earth anchors are tensioned against a bearing plate 1 2 lying against the surface of the excavated earth.

As shown, only parallel rows of reinforcing rods are required in the more stable earth mass of the subsequent excavation. Shotcrete 1 3 may be applied only to encapsulate the rods or it may be applied over the entire surface of the exposed wall to form a blinding layer. If required, a reinforcing mesh (not shown) may also be used in conjunction with the reinforcing rods 1 1 .

FIG 3 shows a preferred form of bearing plate 1 2 of the type employed in the structure shown in FIG 2.

The plate 1 2 comprises a planar portion 31 having a slotted aperture (not shown) to receive the free threaded end 1 4 of an anchor rod. As the anchor rod is inserted into the earth mass at an angle relative to the horizontal, a tapered washer 1 5 is provided for an anchor nut 1 6 to bear upon.

Located across the top of bearing plate 1 2 is a tubular housing 1 7 to slidingly receive a reinforcing rod 1 8. Reinforcing rod 1 8, once located in housing 1 7, may be secured by welding at the ends of the housing or by a clamp means such as a threaded bolt extending through a threaded aperture in the housing wall.

FIGS 4 and 5 show an alternative earth reinforcing and confining system according to the invention.

In this example, sheet pile members 20 are located in an earth mass to a required depth as spaced pairs. The spaced pairs of sheet pile members as shown will provide sufficient support to permit at least a shallow excavation in relatively unstable earth masses.

Earth anchors 21 are progressively installed through the sheet piling as described with reference to FIG 1 and the anchors are tensioned by nuts 22 bearing on tapered washers 23 in turn bearing on contoured bearing plates 24 located in a trough of the sheet pile members 20. This adds stability to the earth mass. In this embodiment, the free ends 25 of the anchor rods 26 extend from the base 27 of the trough where they extend through the sheet piling to a position just beyond the tops of adjacent ribs 28. Reinforcing rods 30 are then located against the tops of ribs 28 of the sheet piling and the rods may be tack welded or otherwise secured to the other pile members over which the rods pass. For example, the rods 30 may be secured to respective sheet pile members 27 by means of bearing plates 29 of the type illustrated in FIG 3 and depending on the nature of the earth structure, rods 30 may be tensioned or untensioned . If tensioning is required, nuts 22a are torqued to a predetermined value to tension the rods 30 which then assume the position shown in phantom between the tops of adjacent ribs 28. In the event that the exposed surface of the earth retaining and confining system is to be sprayed with Shotcrete or the like and then screeded to form a finished wall surface 32 as shown in phantom in FIG 6, it is important that there is minimum protrusion beyond the tops of adjacent ribs 28 as regulations usually require a minimum thickness of coverage over steel members.

As shown in FIG 6, this may be achieved by a bracket

33 having a jaw 34 which engages over reinforcing rod 35 and which is secured to anchor rod 26 by a nut 36. In this case, the anchor rod end 37 is terminated below the levels of adjacent rib tops 28 and tensioning of rod 35 is carried out only if required.

If required, steel mesh 32 shown in FIG 4 may also be used in conjunction with reinforcing rods 30 and the entire structure may then be sprayed with Shotcrete to encapsulate the reinforcing members and to form a blinding layer in the spaces therebetween.

When the Shotcrete has at least partially cured, excavation may then continue with placement of further reinforcing members as described above. The above described method is considered to be particularly advantageous over prior art earth stabilization and confinement systems due to substantially reduced labour and materials requirements while maintaining sufficient integrity for a temporary wall structure. By utilizing a borehole drill fitted with spaced drill bits, the holes for two, three or even four adjacent anchors may be drilled simultaneously, thereby saving considerable time in installation of earth containing and retention systems according to the invention. It is considered that the structure shown generally in FIG

4 utilizes up to 50% less earth anchors than equivalent systems and overall, consumes less steel than continuous sheet piling systems.

Where circumstances mitigate against the installation of the spaced sheet pile "soldiers", spaced boreholes can be prepared to receive cast in situ reinforced concrete piles. These concrete piles may be supported by anchors attached to brackets on the concrete columns or by a saddle bracket extending between adjacent concrete piles. The following examples further illustrate the flexibility and the broad applicability of the stabilization and confinement systems according to the invention.

Examples

To "stitch" together a rock formation, a plurality of holes are drilled in a matrix configuration, preferably three rows deep. Rock anchors are inserted in the holes; grout is pumped into the holes and the anchors are pre-tensioned when the grout has partially set.

Reinforcing plates are provided on the anchor rods, and each reinforcing plate has a tubular body dimensioned to freely receive reinforcing rods passing through the bodies. Reinforcing rods interconnect the reinforcing plates on the anchors in columns, rows and/or diagonally and it is preferable that, at a "join", adjacent reinforcing rods pass through the tubular body of a reinforcing plate and overlap for, eg., 0.5 to 1 metre. The reinforcing rods are then pre-tensioned, eg., using tensioning nuts at respective ends of the rods.

The reinforcing rods may be tack-welded to the reinforcing plates, and then reinforcing mesh is fixed to the reinforcing rods, preferably interposed between the reinforcing rods and the exposed face of the rock wall . The anchors are then post- tensioned to force the reinforcing mesh (and reinforcing rods) into compression against the exposed face of the rock formation. This compresses the exposed face inwardly, while the zones around the anchors are compressed so that the total rock structure is placed into compression. Initially, the reinforcing is "dynamic", but when the anchors have been tensioned, the resulting reinforcing is passive. Example 2 In sandy, clay and/or shale soil structures, after the reinforcing mesh has been erected by the method of Example 1 , the reinforcing mesh is sprayed with concrete to form a wall. It is preferable that the concrete incorporate polymeric reinforcing fibres (eg . , of the type sold under the trade mark "FIBREMESH") and the concrete is allowed to set before the anchors are post-tensioned.

A binding layer of concrete may be sprayed onto the exposed wall surfaces either before or after the anchors are inserted, but before the reinforcing rods and reinforcing mesh are applied, to minimise likelihood of failure of the exposed wall surface while the stabilization method is being carried out. Example 3

In sand, clay or shale, soldier piles or sheet piles are erected in front of the exposed wall face and supported by the anchors, and the reinforcing steel mesh is optionally connected to the sheet or soldier piles. The use of the sheet or soldier piles has the advantage that the number of anchors required to support a particular soil structure can be reduced, eg., by up to 50% . Example 4

To enable excavation in an unstable soil structure, pairs of holes are drilled in the structure, substantially along the line to be excavated, at spaced intervals. Reinforcing steel is placed in the holes, and concrete or grout, preferably containing the polymeric reinforcing fibres, is pumped into the holes to cast the piles in situ .

When the piles have set, the structure is excavated, eg ., to a depth of 1 -2 metres and an anchor is provided to support each pair of piles in the excavated zone. (Preferably, holes are drilled into the soil structure, the anchors are inserted and grouted, the anchors are pre-tensioned, and then post-tensioned after the grout has set.)

Reinforcing mesh and/or rods are provided between the adjacent pairs of piles and concrete (containing polymeric reinforcing fibres) is sprayed onto the reinforcing mesh and allowed to set. The excavation that is carried out to a further depth of, eg., 2 metres, further anchors are installed, reinforcing mesh erected and concrete sprayed as hereinbefore described . These steps are repeated until the excavation reaches its desired depth. (NB: It is preferable that the piles extend at least 1 .5 metres below the desired depth of excavation.)

Example 5

Where the soil formation is primarily rock, it is optional whether or not the concrete is sprayed onto the reinforcing mesh. Example 6

A binding wall layer of concrete may be sprayed onto the exposed wall before the reinforcing mesh is erected in Examples 4 and 5.

Example 7 In expansive soils, eg . , clay, blocks of foam may be fixed to the exposed wall face (or blinding wall layer) and be interposed between the exposed wall face and "the reinforcing material to accommodate any expansion or contraction of the soil as the soil is either watered or de-watered . (Some de-watering of the soil will occur when the anchors are post-tensioned.)

Example 8

In an alternative embodiment, the foam material may be sprayed onto the exposed wall or blinding layer before the reinforcing mesh is erected .

At the base of the excavation, conventional footings for a building may be cast, and it is preferable that the base of the wall be tied to the footings to form water-proof unitary structure. Example 9

For deep excavations, eg., greater than 10 metres, excavation can be carried out in a series of steps, where each seceding wall is "stepped out" from the wall above it and the top of one wall is tied to the bottom of the wall above it. Example 1 0

Where the unstable soil overlies the stable soil formation, the excavation method may be carried out until the stable soil formation is reached, and then the base of the wall may be tied to sheet piles (or other piles) driven into the stable soil formation . The methods hereinbefore described enable unstable or poor quality soil formation to be stabilized and/or excavated and the resultant soil structure is much stronger and more stable than the soil structure stabilized by existing stabilization methods where the soil structure is not compressed (eg . , to overcome any weaknesses or voids in the structure) .

The examples described are by way of illustrative example only and various changes and modifications may be made thereto without departing from the broad scope of the invention. FIG 6 shows schematically a soldier pile 40 according to a further aspect of the invention.

Soldier pile 40 comprises centre flanges 41 , 42 and outer flanges 43, 44 and the cross sectional shape of the pile 40 is complementary to corrugated sheet piling of the type described in

Australian Patent No. 631 365 and which is preferably employed with the invention.

After inserting sheet piling (not shown) to a required depth in an earth formation, soldier piles 40 are driven, at spaced intervals, into the earth formation against the surface of the sheet piling to provide a support therefor where it is not possible to support the sheet piling by such earth anchors.

As shown, the soldier pile 40 may be made up of a number of elements 40a, 40b secured together by a joining element 45 having a cross-sectional shape complementary to the soldier piler contour.

Elements 40a, 40b (and so on) are progressively joined as the soldier pile is driven into the earth formation by, for example, high frequency vibration. Joining element 45 is secured to the respective lower and upper ends of elements 40a, 40b by bolts 46 or the like.

When the soldier pile 40 is driven into the earth formation to a required depth, it may be secured to the sheet piling (not shown) by bolts, plug welding or the like via punched apertures

47.

FIG 7 shows a bearing pile 50 which may be utilised in accordance with the invention. Bearing pile 50 comprises a pair of pressed, folded or cold rolled metal sheets having a folded central web 51 and opposite side flanges 52 secured together by bolts (not shown) or by jointing welding via apertures 53.

Like the soldier pile of FIG 6, the bearing pile 50 may be constructed of elements 50a, 50b (and so on) sequentially joined together by joining elements 54 as the pile is driven into the earth formation.

The bearing pile may be of any suitable cross sectional shape eg. round or polygonal and may comprise cylindrical elements if required .

FIG 8 shows a wall pile 60 in accordance with yet another aspect of the invention.

Wall pile 60 comprises a generally U-shaped central web with upturned side flanges 60 shaped to nest in the region between central web 40a and respective side flanges 43, 44 of a soldier pile

40 is shown in FIG 6.

After a soldier pile 40 is driven into an earth formation in nesting contact with a sheet pile formation 61 (shown in phantom), wall pile 60 is driven into the earth formation in nesting engagement with the soldier pile 40 to provide additional support of the sheet piling during and after excavation of earth.

As an alternative to wall pile 60, there may be used hollow triangular cross section piles of the type described in

International Patent Application PCT/AU97/00514 and illustrated in Figures 1 and 2 thereof.

Again, like the pile members of FIGS 6, 7 and 8, these triangular piles may be made up of elements joined by a joining member of complementary triangular cross section.

The triangular piles of PCT/AU97/0051 4 have an apex portion which nests directly into the valley portions of the sheet piling system and as such my function directly as soldier piles without the need for the soldier piles of FIG 6. If required, the triangular cross section piles may be of enlarged cross section such that the base portion, opposite the apex portion, lies in a plane spaced from the front surface of the sheet piling.

FIG 9 shows one method of stabilising and confining an earth excavation.

In FIG 9 the earth formation to be excavated comprises a layer of sand 70 and a layer of more stable earth 71 such as shale or clay/shale supported on a bedrock interface 72. Initially corrugated interlocking single or laminated sheet piling members 73 are driven into the earth formation below the sand/shale interface.

Soldier piles 74 of the type shown in FIG 6 are then driven to a desired depth into the earth formation in contact with the sheet piling 73. If required, wall piles 75 (shown in phantom) of the type shown in FIG 8 or of a triangular cross section as described above then may be driven into the earth formation to a desired depth, in this case down to the bed rock layer 72. Thereafter excavation is carried out with the unstable sand layer 70 being supported and confined by sheet piling 73, itself being supported by soldier piles 74 at spaced intervals and, if required wall piles 75.

If the excavation is to be carried out directly adjacent an existing building structure whereby the use of earth anchors is precluded, the soldier pile/wall pile combination will provide sufficient support for the sheet piling .

Where the use of earth anchors is not precluded, the excavation wall may be supported by the sheet piling 73 and soldier piles 74 with earth anchors 76.

If it is intended to utilise the exposed excavation wall as, say, a direct wall for a basement, wall piles 75 may then be removed and the exposed wall could then be finished by applying a blinder layer of sprayable cementitious composition over a metal mesh between the soldier piles below the level of the sheet piling . The entire wall surface may then be finished in the manner described in our Australian Patent No. 682453. Alternatively, hollow wall piles 75 may be left in place and secured to the soldier piles 74 by spaced welds, bolts or the like. Any earth remaining in the hollow interior of wall pile 75 below the excavation floor 77 may then be removed by blasting high pressure air or water via a nozzle lowered into the pile interior. The pile 75 may then be partially filled with compacted sand or earth and a concrete cap 78 containing steel starter bars 79 is formed in the upper part of the pile.

A concrete bond beam 80 tied to the piles 75 via starter bars 79 may then be formed about the upper periphery of the excavation to provide footings for a building structure to be erected thereon.

To support a floor slab 81 poured on the excavation floor 77, bearing piles 82 of the type illustrated in FIG 7 may be driven down to bedrock layer 72 and any earth therein removed by air or water blasting . Thereafter, the interior of the pile 82 is partially filled with compacted sand and a concrete cap 84 containing starter bars 85 is then formed in the top portion of pile 82.

Concrete slab floor 81 when poured is then tied to and supported by bearing piles 82.

If required, longer bearing piles 86 containing compacted sand 87 and a concrete cap 88 with starter bars 89 may extend from the bedrock surface 72 through the floor slab 81 to su pport a suspended floor slab 90 (shown in phantom) .

As indicated previously, unitary cylindrical bearing piles may be employed with the method rather than the two-piece piles of FIG 7.

FIG 10 shows an alternative embodiment of the method described with reference to FIG 9.

As with the soil stabilisation and confining system of FIG

9, sheet piling 100 is driven into an earth formation such that the lower end 1 01 of the sheet piling 1 00 is located below the interface

1 02 between an unstable sandy layer 1 03 and a layer of stable shale or clay/shale 1 04 and also below excavation floor 1 1 3.

Thereafter, spaced soldier piles 1 05 of the type illustrated in FIG 6 are driven into the earth formation with the upper portion thereof nested with the corrugated sheet piling 1 00.

Wall piles 1 06, again nested against the soldier pile 1 05 are driven into the earth formation with the lower ends 107 thereof spaced above a bedrock layer 1 08.

Earth is then removed from within the hollow interior of wall piles 106 by high pressure air or water blasting and a hollow cavity 109 below the wall piles 106 is created by the fluid blasting process.

A flowable curable cementitious mass is then pumped under pressure into the interior of wall piles 106 until it fills the hollow cavities 109 below the wall piles and fills at least the lower portion 110 of each wall pile 106. If required, steel reinforcing bars (not shown) may extend between the cementitious mass in the lower portion 110 of the wall piles and the cementitious mass 111 occupying the hollow cavities 109. When the cementitious mass 111 cures it provides a foundation or footing to support loads applied on wall piles 106 and thus obviates the need for excessively long wall piles where the bed rock surface 108 is very deep in the earth formation.

After excavation is completed and before the floor slab 112 is poured on the excavation floor 113, bearing piles 14 are driven into the earth formation and the earth contained in the piles is removed by air or water blasting.

As with the wall piles 106, a hollow cavity 115 is formed beneath each bearing pile 114 where the lower end thereof is not resting on the bedrock surface 108.

Again, the hollow cavities 115 and the hollow interior of bearing piles 114 are filled with a flowable curable cementitious mass pumped therein under pressure and, if required, reinforcing bars 116 may extend from the footing or foundations 1 1 7 through the bearing piles 1 1 4 to protrude therefrom to the floor slab 1 1 2 when it is poured.

After the floor slab 1 1 2 has been poured, the portion of wall pile 1 06 extending above the floor surface is removed by cutting the wall piles 1 06 with an oxy-acetylene torch or the like at floor level and then removing the severed portion.

Thereafter, the wall surface of the excavation may be completed by spraying a cementitious binder layer onto steel mesh reinforcing between the soldier piles 1 06 and then applying a screeded cementitious surface over the entire exposed surface in accordance with the method described in our Australian Patent 682453.

Piles of the type shown in FIG 7 and as shown generally in FIGS 9 and 1 0 as bearing piles have been shown to possess significant load bearing capacity when filled with a cementitious grout and a steel reinforcing cage.

Similarly, the performance of triangular section piles of the type described in our co-pending International Patent Application PCT/AU97/0051 also can be greatly improved by the use of a cementitious core with steel reinforcing .

Table 1 below represents the ultimate binding capacities of triangular pile sections using differing steel wall thicknesses and differing low strength concrete grouts. The steel reinforcing cage comprised three Y1 2 bars equally spaced in the section with R6 ties at 300mm intervals.

TABLE 1

Table 2 below represents calculated load strengths of an isosceles triangular section pile having a base width of 1 86mm and a height (base to apex) of 1 1 0mm with differing reinforcement capacity and concrete grout strength.

Significantly these calculated load capacities do not allow for the contribution of the triangular section steel outer casing .

TABLE 2

Notes: ( 1 ) The geotechnicai capacity of the pile will depend on the local soil conditions. (The local soil conditions need to be checked to confirm pile capacity)

(2) The pile loads are WORKING LOADS (not factored) .

(3) The pile loads assume no pile eccentricity. (4) Pile capacities do not include additional capacity due to steel casing.

Table 3 below shows pile capacity for an isosceles triangular section pile having a base width of 275mm, a height (base to apex) of 1 38mm and a steel wall thickness of 4mm. TABLE 3

Table 4 below shows load capacity of a square section pile of the type shown in FIG 7 having an external section measuring 230mm x 230mm, a wall thickness of 3mm and with varying concrete grout and reinforcement strengths . The steel reinforcing bars are equally spaced and lie along intersections between opposite corners.

TABLE 4

Similarly Table 5 represents a square section pile measuring 400mm x 400mm and a wall thickness of 4mm. Variously, combinations of spaced reinforcing bars are positioned to lie along the intersections between opposite corners approximately 50mm in from the inner wall surface and/or centrally of the external casing walls, again about 50mm in from the inner walls. TABLE 5

In the piles of Tables 4 and 5, the calculations do not take into account the additional capacity of the steel casings.

FIG 1 1 shows yet another aspect of the invention which can be employed with other aspects of the invention requiring sheet piling .

Generally speaking, the use of flexible sheet piling of, say, 3mm in thickness according to the earlier described aspects is very effective for its intended purpose provided sufficient earth anchors are employed to reinforce the corrugated sheet piling structure.

In order to insert an earth anchor, it is first necessary to cul an aperture in the sheet piling with an oxy-acetylene torch or the like and then drill a borehole to receive an earth anchor. Depending on soil conditions, the earth anchor may be driven directly into the soil by impact or high frequency vibration.

After the anchor is inserted it is tensioned against a bearing plate by a threaded nut.

As insertion of earth anchors is a relatively expensive exercise it would be of economic significance if the number of earth anchors could be reduced without affecting the structural integrity of a sheet piling installation.

In FIG 1 1 there is shown a laminated sheet pile 1 30 having a corrugated cross section wherein adjacent faces are at about 90° to each other.

The laminated pile typically comprises a full length pile member 1 31 , 3mm thick and say, 1 2m in length and laminated thereto are further 3mm nested pile members 1 32, 1 33 of say 9m and 6m in length respectively.

The lower end or toe 1 34 of the laminated sheet is tapered by offsetting the laminates 1 32, 1 33 by an amount approximately equal to the sheet thickness (3mm) and then fillet welding the sheets together across the free edges.

Between the upper ground surface 1 35 and the floor 1 36 of excavation 1 37 lies a slip plane 1 38 which has an angle dependent upon the soil type and structure.

After the sheet piling 1 30 is driven into the earth to form a support for an excavated wall, excavation occurs progressively with earth anchors being inserted at appropriate excavation depths and spacings across the interlocked sheet piling wall.

As shown a first earth anchor 1 39 may be inserted at an excavation depth of 1 m, and successive anchors 140, 1 41 and 142 at depths of 4m, 7m and 9m and respectively tensioned to 50kN,

65kN and 1 00kN.

The added stiffness of the laminated sheet towards the level of the floor of the excavation, where the compressive load of the earth therebehind is greatest, permits far less earth anchors to be employed .

In a typical excavation of from 1 0-1 2m in depth the number of earth anchors may be halved with resultant considerable cost savings. Moreover, as the thickness of the laminated pile is greatest at the base of the excavation, the extent to which the sheet piling must extend into the earth below the excavation floor (typically from 1 -3m) may be reduced with a further saving in steel. The laminated pile is preferably coated with a corrosion resistant coating such as galvanising, zinc plating, a tar epoxy compound or other synthetic resin.

The layers of the steel laminate may be connected by edge welding, plug welding, bolting or by adhesive or any combination thereof.

Depending upon the soil type, the laminated structure may comprise contoured sheets of steel or fibre reinforced plastics material or a combination thereof.

FIG 1 1 a shows schematically the relationship between sheet piling thickness and inertia moment and Table 6 shows specification and sectional parameters.

TABLE 6

Section Thickness Profile Mass Moment of Section kg/m of kg/m² of Inertia Modules

(Code) (mm) (mm) single pile wall (cm⁴/m) (cm³/m)

SP215 2 150 18.90 29.50 1378 169

SP315 3 150 28.26 44.30 2045 249

SP415 4 151 37.68 59.00 2767 333

SP515 5 152 47.16 73.80 3598 424

SP615 6 153 56.52 88.60 4600 527

SP715 7 154 65.94 103.30 5845 647

SP815 8 155 75.36 118.00 7426 788

SP915 9 156 84.84 132.80 9456 959

SP115 10 157 94.32 147.60 12084 1165

FIG 12 shows still a further embodiment of the invention.

In FIG 12, an anchored pile 140 is constructed by forming a borehole 141 in an earth formation 142 down to a base layer 143 and then filling the borehole with a low strength cementitious grout 144 of say 20-40 mPa.

A hexagonal section reinforcing cage 145 having say Y16 bars and R6 ties is then lowered into the grout while it is still fluid. The cage is positioned centrally of the grout column and rests on the base layer 143 forming the floor of the column.

After the grout is allowed to cure for 3-4 days a 150mm borehole 146 is formed down the centre of the reinforcing cage and through the base layer 1 43.

An earth anchor 1 47 with associated tension rod 148 is then inserted in borehole 1 46 and anchor 1 47 is anchored in the surrounding earth formation 1 49 by placing an apertured plate (not shown) over the top threaded end 1 50 of anchor rod 148 and then tensioning a threaded nut (not shown) to engage the flukes 1 51 of anchor 147 in the wall of borehole 1 46.

After releasing the nut and bearing plate, a further quantity of grout is placed in the lower portion of borehole 1 46 to fully encapsulate anchor 147.

The grout is allowed to cure for 3-4 days after which the anchor rod 1 48 is again tensioned to ensure anchoring of anchor 1 47.

The pile is then completed by filling the remainder of borehole 1 46 with grout and allowing it to cure. In an alternative embodiment, instead of a reinforcing cage, a triangular section pile of our co-pending application PCT/AU97/00514 may be employed or a combination of triangular section pile with reinforcing bars.

Table 7 shows calculated working capacities for the combined compression/tension piles according to this aspect of the invention. TABLE 7

It should be noted that the calculations in Table 7 do not take account of any of the steel reinforcing or anchoring elements.

Anchored piles of this aspect of the invention will have application where a structu re supported on the piles can apply both tension and compression to the pilings. Tension for example could occur due to wind uplift on the supported structure, earthquakes or even buoyant forces from subterranean water.

FIG 1 3 shows schematically a building structure 1 60 supported at ground level 1 61 on anchored piles 1 62 of the type described with reference to FIG 1 2.

Below ground level 1 61 is a two level basement area 1 63 surrounded by a waterproof wall 1 64 and a waterproof floor 1 65 also supported in its central area by anchored piles 1 62. Piles 1 62 rest on a foundation layer interface (bedrock) 1 66 with anchors 1 67 anchored therein.

In some soil conditions such as poorly drained soils and in particular clay soils, the buoyant uplift on the building structure 1 60 can cause movement in the structure when the soil becomes waterlogged .

Of even greater concern is that if such a structure was to be built on a hydraulic clay soil, prolonged dry periods can cause substantial shrinkage of the soil with consequent subsidence of the structure. If then followed by very wet conditions, the combined effects of buoyancy and the hydraulic expansion of the clay can cause very high uplift forces.

FIG 1 4 shows another application of anchored piles.

In FIG 1 4 there is illustrated schematically an underground liquid storage vessel 1 70 for water, fuel or other liquids.

Vessel 1 70 may be constructed from sheet piling according to the invention and lined with screeded cementitious grout to form a fluid tight container. A lid or roof 1 71 may comprise a suspended concrete slab and have appropriate conduits 1 72, 1 73 for filling, emptyings or as a breather.

The vessel is constructed as generally described above by installation of corrugated sheet piling followed by excavation. Before forming floor slab 1 74 anchored piles 1 75 are formed by drilling boreholes and formation of cavities 1 76 thereunder by high pressure fluid excavation.

Fluid cementitious grout is pumped into the cavities 1 76 and earth or other anchors 1 77 are inserted with their respective anchoring heads anchored in the cementitous mass 1 78 in each cavity. The anchor rods 1 79 extend beyond the upper openings of the boreholes for connection to floor and/or wall reinforcing members (not shown) .

The boreholes are then filled with cementitious grout before pouring of the floor slab 1 74 and screeding of walls 1 80.

When completed, vessel 1 70 may be covered with a layer of earth 1 81 if required .

Even when the vessel 1 70 is filled with say liquid fuel, the specific gravity is sufficiently less than water in the surrounding earth mass such that uplift can occur.

The main advantage of the structure as shown with anchored piles is realised when the vessel is empty or near empty when the buoyant uplift forces in waterlogged earth could dislodge the vessel.

Anchored piles according to the invention will have particular application to the construction of swimming pools and the like. Throughout the above description, reference is made to contoured sheet piling members, soldier pile members, wall piles and hollow or grout filled load bearing piles formed from elements having generally complementary surface contours.

Typically, these members may be formed from 3mm thick black mild steel sheet in a brake press or other folding operation.

It has now been found that instead of forming the contoured members by a folding operation, substantial increases in strength can be obtained by roll forming those members. In this manner, comparative tests on folded vs roll-formed members show an increase in yield stress from about 350 MPa in folded steel to about

410 MPa in roll formed steel. This is attributed to work hardening during the roll-forming process.

The following discussion relates to a determination of ultimate load capacity of roll formed sheet piling members employed in various aspects of the invention.

Three series of tests were conducted single, double and triple panel configurations shown generally in FIG 1 5. Each full sheet was 3000mm long x 91 5mm wide x 3mm thick having an upper profile of three peaks and two valleys. The distance from peak to valley was approximately 1 50mm.

The sheet configurations were supported as simple beams with the end reactions formed to the profile of the sheets. Sand was placed on the central section giving a bed the width of the specimen by 1 metre long and to a height of 50mm above the peaks. Lateral restraints were provided by greased steel beams, allowing vertical movement of the sheets only.

For Series 1 and 2 tests and Series 3(2), a rigid beam the width of the specimen was placed centrally across the specimen. For series 3(1 ), the beam was 2/3 the width of the specimen. A load was applied centrally through the beam with load vs. central deflection recorded.

TABLE 8 SINGLE SHEET (SERIES 1 )

SUBSTITUTE SHEET (RULE 26)

Clear span 2850mm Width 81 5mm Thickness 2mm Dead loads to be added to the above : 1 24kg bems + 265kg Sand

TABLE 9

DOUBLE SHEET (SERIES 2)

SUBSTITUTE SHEET (RULE 26)

Clear span 2850mm Width 960mm Thickness 3mm

Dead Loads to be added to the above :64kg beams + 278kg Sand

SUBSTITUTE SHEET (RULE 26) TABLE 10

TRIPLE SHEET (SERIES 3(1 ))

* Load removed to adjust sand

Clear span 2850mm Width 2260mm Thickness 3mm

Dead loads to be added to the above : 79kg beams + 41 6kg Sand

SUBSTITUTE SHEET (RULE 26) TABLE 1 1

TRIPLE SHEET (SERIES 3(2))

* Load removed to adjust sand

Clear span 2850mm Width 2260mm Thickness 3mm

Dead Loads to be added to the above : 163kg beams + 410 kg Sand

Graphical representations of the load vs deflection data for

tables 8 to 1 1 are shown in FIGS 1 6-1 9.

SUBSTITUTE SHEET (RULE 26) CONCLUSIONS Ultimate Moment Capacity of Sheet Piling System

Three series of tests were conducted on the sheet piling systems shown in FIG 1 5. Four panels with simply supported end conditions and a span of 2850 mm were tested to failure under transverse line loads at midspan. Series 1 had a single panel sheet piling system whereas Series 2 and 3 had a "double panel" and a triple panel sheet panel system, respectively. In Series 3, two tests were conducted with different lengths of midspan line loads (2250 and 1 500 mm) . These test results are further evaluated and compared with corresponding theoretical predictions.

1 . Tensile Testing of Steel Specimens

Tensile testing of steel specimens cut from sheet piling gave the following average tensile strength properties:

Yield stress f_v = 409 MPa * Ultimate tensile stress f_u = 501 Mpa * - based on 0.2% proof stress Tensile test results showed that the steel used in the sheet piles had tensile stress-strain curves with a substantial yield plateau, an average percentage elongation at failure of 29.1 %, and f_u/f_y ratio of = 1 .22. These results indicate that the steel used has adequate ductility. 2. Transverse Load Tests on Sheet Piling Systems

In all three test series, test panels appeared to have developed plastic hinges at midspan at ultimate failure loads without any local buckling prior to this. Theoretical moment capacity calculations using measured panel geometry and yield stress also support this observation. In the absence of local buckling, the ultimate moment capacity has been taken as the product of steel yield stress f_y and the plastic section modulus of the panel S. The measured yield stress used in the theoretical calculations is 409 Mpa whereas the important measured panel dimensions used are:

* Thickness = 2.995 mm

* Rib Height = 1 45 mm

* Pitch = 332 mm For each test series, experimental ultimate moment capacity of the sheet piling system is calculated based on the maximum applied test loads, and compared with the corresponding theoretical predictions.

Series 1 : Single panel sheet piling system For this series, the theoretical moment capacity was calculated using both an exact panel geometry that included the effects of curved comers (Case 1 ) and an approximate panel geometry that ignored them (Case 2) . Theoretical ultimate moment capacity = 54.2 kNm (Case 1 ) and 50.4 (Case 2)

Experimental ultimate moment capacity = 53.3 kNm As seen above, theoretical and experimental capacities agree very well.

Series 2: "Double" panel sheet piling system

For this series, the theoretical moment capacity was calculated using only the approximate panel geometry that ignored the effects of curved comers (Case 2) as the effect on moment capacity was small.

Theoretical ultimate moment capacity = 81 .1 kNm (Case 2) Experimental ultimate moment capacity - 78.6 kNm

As seen above, theoretical and experimental capacities agree reasonably well.

Series 3: Triple panel sheet piling system Test Series 3( 1 ) was not considered in this report as it had a reduced loading width. For the other test, Series 3(2) , the theoretical moment capacity was considered to be three times that of a single panel system (Series 1 ) . Theoretical ultimate moment capacity = 1 62.6 kNm (Case 1 ) and 1 51 .2 kNm (Case 2) .

Experimental ultimate moment capacity = 1 49.6 kNm.

As seen above, theoretical and experimental capacities agree reasonably well (8% difference compared with Case 1 ) .

Experimental ultimate moment capacities in Series 2 and 3 appear to be slightly less than the corresponding theoretical moment capacities. Therefore, the following recommendations are made based on the test results and theoretical predictions and associated assumptions as stated in this report.

1 . Ultimate moment capacity of a single sheet piling system can be taken as 50 kNm.

2. Ultimate moment capacity of a triple sheet piling system can therefore be taken as approximately three times that of a single sheet piling system, ie. 1 50 kNm.

3. Ultimate moment capacity of a "double panel" sheet piling system can be taken as 78 kNm.

It will be clear to a skilled addressee that with the many aspects of the invention described herein, various combinations of features from these aspects can be employed rather than the specific methods and systems which are described by way of example only.

For example, FIG 20 shows a cross sectional view of a sheet piling wall 200 supporting an earth mass 201 in an excavation. The sheet piling wall 200 comprises, typically, a 3rnm thick corrugated steel sheet having the same type of configuration as that shown at 61 in FIG 8 and is by earth anchors 202.

To stiffen the upper region of the sheet piling barrier, a ring beam construction is formed by supporting 450-500mm wide strip of

F62 mesh 203 against the speed outstanding ribs and secu ring the mesh thereto by welding spaced Y- 1 6 bars 205 to the sheet piling where the bars 204 come into contact with the vertical ribs 203.

A 450mm wide waler 206 formed of 3mm steel and having a cross section similar to the sheet piling is secured transversely across the top of the sheet piling 200, the mesh 202 and reinforcing bars 204 by bolts 207 extending through the orthogonally oriented sheets where respective ribs contact each other.

Concrete 208 having a strength of about 32 in Pa is introduced into the space between the orthogonally oriented sheets to form a continuous ring beam about the top of the sheet piling wall 200.

Throughout this specification and claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers.

Claims

CLAIMS:

A method of stabilization and confinement of excavated earth structures, said method comprising the steps of:

(a) excavating an earth structure to a predetermined depth;

(b) inserting earth anchors into a wall structure formed by excavation;

(c) tensioning each of said earth anchors to a required value against bearing members lying against the surface of the wall structure;

(d) interconnecting the exposed ends of selected earth anchors with reinforcing members; and

(e) applying a sprayable cementitious composition to the wall surface to encapsulate part or all of said reinforcing members.

2. A method as claimed in claim 1 wherein said boreholes are spaced at intervals such that when said earth anchors are tensioned, respective zones of compression associated with said bearing members overlap to form a compressed earth structure in the region of the exposed earth surface.

3. A method as claimed in claim 1 or claim 2 wherein the earth anchors are grouted into the earth formation with a cementitious grout.

4. A method as claimed in any one of claims 1 to 3 wherein the reinforcing members may comprise steel rods and/or cable and/or steel reinforcing mesh or any combination thereof.

5. A method as claimed in claim 4 wherein the steel rods and/or cable are connected between adjacent anchors in columns, rows or a mesh array.

6. A method as claimed in any preceding claim wherein the sprayable cementitious composition includes reinforcing fibres.

A method as claimed in any one of claims 4 to 6 wherein the bearing members comprise steel plates adapted to receivably locate said steel rods and/or cable and/or mesh.

8. A method as claimed in any one of claims 4 to 7 wherein the steel rods and/or cable and/or mesh are secured to said bearing plates by clamping means or by welding .

9. A method as claimed in any preceding claim wherein the bearing members associated with at least some of said earth anchors comprise spaced soldier piles or sheet piles.

1 0 A method as the soldier piles or sheet piles are arranged as spaced pairs.

1 1 . A method as claimed in any preceding claim wherein the bearing members may be selected members of a continuous sheet piling system.

1 2. A method as claimed in any one of claims 9 to 1 1 wherein the sheet piles comprise at least partially flexible sheet piles.

1 3 A method as claimed in any preceding claim wherein the reinforcing rods are pretensioned before the reinforcing mesh is mounted thereon, or before the cementitious composition is applied.

14. A method as claimed in any preceding claim wherein the reinforcing members are provided to interconnect the anchor in columns and/or rows and/or diagonally.

1 5. A method as claimed in any one of claims 1 to 1 3 steps (a)-(e) may be repeated until the excavation has reached a required depth.

1 6. A method as claimed in claim 1 6 wherein the exposed ends of selected earth anchors in a first excavation step are interconnected with reinforcing members to form a mesh like array and in one or more subsequent excavation steps, the exposed ends of selected earth anchors are interconnected with reinforcing means in rows, columns or diagonally.

1 7. A method as claimed in claim 1 wherein anchored sheet piling may be employed to stabilize and confine a second or subsequent excavation step.

1 8. A method as claimed in any preceding claim wherein a plurality of pile members are located in said earth formation before an initial excavation step.

1 9. A method as claimed in claim 1 8 wherein at lest some of said plurality of pile members are anchored with earth anchors to the earth structure therebehind before conducting a subsequent excavation step.

20. A method as claimed in claim 1 8 or claim 1 9 wherein the pile members form spaced or continuous sheet piling.

21 . A method as claimed in any one of claims 1 8 to 20 wherein the pile members are located in the earth structure as spaced pairs, each said spaced pair being spaced from an adjacent spaced pair by a distance greater than the spacing between a spaced pair of pile members.

22. A method as claimed in claim 20 or claim 21 wherein the spaced pile members comprise steel sheet piling members with earth anchors extending into the earth structure via apertures in said sheet piling members.

23. A method as claimed in claim 20 or claim 21 , wherein the spaced pile members comprise reinforced concrete piles formed in situ in spaced boreholes in the earth structure, the spaced concrete piles being anchored to the earth structure by an earth anchor connected to a saddle member extending between spaced pairs of concrete piles.

24. A method as claimed in any one of calims 1 9 to 23 wherein the earth anchors are tensioned to a predetermined value to induce compression in the earth structure behind said spaced pile members.

25. A method as claimed in claim 24 wherein the earth anchors are relatively positioned such that when tensioned, regions of compression in the earth structure, associated at least with adjacent pile members, overlap to form a reinforced earth structure.

26. A method as claimed in any one of claims 1 9 to 25 wherein the reinforcing members extending between exposed ends of selected earth anchors are tensioned to a predetermined value after said earth anchors are tensioned.

27. A method as claimed in any one of claims 1 9 to 26 wherein the reinforcing members may comprise steel rods, cable, mesh or any combination thereof.

28. A method as claimed in any one of claims 1 to 1 7 wherein a layer of resiliently deformable material may be applied to the exposed earth wall surface prior to interconnection of the free ends of exposed earth anchors to form a compressible barrier between the exposed earth wall surface and a su bsequently applied layer of cementitious composition encapsulating said reinforcing members.

29. A method as claimed in any one of claims 1 to 1 7blinding layer of sprayable concrete is applied to the exposed earth wall surface prior to placement of a resiliently deformable material and/or a subsequent layer of cementitious composition encapsulating said reinforcing members.

30. A method as claimed in any preceding claim wherein the lower ends of the stabilizing and confining structure may be connected to footings formed in the base of the excavation and a load bearing structural wall may be formed by spraying the surface of the stabilizing and confining structure so formed a suitable cementitious composition and subsequently screeding the sprayed surface to form a smooth wall.

31 . A method according to any one of claims 1 8 to 30 wherein after said plurality of pile members are located to a desired depth in said earth structure, the method comprises the further steps of:-

(f) locating, at spaced intervals against a surface to be exposed of said pile members, soldier piles having respective lower ends at a depth greater than lower ends of said piling members; (g) conducting a first excavation step to a desired depth;

(h) conducting a further excavation step to a desired depth;

(i) anchoring said soldier piles to the earth structure therebehind with earth anchors below the lower ends of said sheet pile members; and, if required

(j) repeating steps (h) and (i) until a desired excavation depth is achieved.

32. A method as claimed in claim 31 wherein said soldier piles comprise hollow tubular piles.

33. A method as claimed in claim 31 wherein said soldier piles comprise longitudinally apertured elongate members forming a closed tubular member when positioned against a sheet pile member.

34. A method as claimed in any one of claims 31 to 33 wherein said soldier piles are driven into the earth formation whereby a quantity of earth occupies at least portion of the hollow interior thereof.

35. A method as claimed in claim 34 wherein the earth located within the soldier pile is removed and replaced with a curable cementitious material.

36. A method as claimed in any one of claims 31 to 36 wherein the soldier piles are driven into the earth formation to contact a bed rock foundation.

37. A method as claimed in any one of claims 31 to 36 wherein the soldier piles are driven into the earth formation such that respective lower ends thereof are located above a bed rock foundation and a mass of flowable curable cementitious material is pumped under pressure into the hollow interior thereof whereby a mass of cementitious curable material emerges from the respective lower ends of the soldier piles to form a footing or foundation therefor.

38. A method as claimed in claim 37 wherein reinforcing members extend between the interior of said soldier piles and respective footings or foundations therefor.

39. A method as claimed in any one of claims 3 1 to 34 wherein when a soldier pile is driven into contact with a bed rock foundation, a lower portion of the hollow interior thereof may be filled with compacted sand or earth and an upper portion thereof filled with a curable cementitious composition having reinforcing elements extending upwardly therefrom.

40. A method as claimed in any one of claims 31 to 39 wherein the soldier piles may comprise discrete elongate members axially joined by joining members.

41 . A method as claimed in any one of claims 3 1 to 40 wherein exposed regions between adjacent soldier piles include reinforcing members and/or mesh embedded in a sprayable curable cementitious material to form walers and/or blinder walls.

42. A method as claimed in any one of claims 31 to 41 wherein the soldier piles are secured to the sheet pile members by welding and/or by bolting .

43. A method as claimed in any one of claims 1 1 to 42 wherein a reinforced concrete bond beam is formed along the top of the sheet piling structure as a structural foundation for a building structure to be supported thereon.

44. A method of installation of a load bearing pile in an earth formation, said method comprising the steps of:- locating along an upright longitudinal axis into an earth formation an elongate hollow pile member open at both ends thereof; supporting said hollow pile member on a footing or foundation; and filling at least an upper portion of said hollow pile member with a curable cementitious material to encase reinforcing members extending upwardly from an upper end of said hollow pile member.

45. A method as claimed in claim 44 wherein said hollow pile member is driven into said earth formation until it contacts a bedrock formation.

46. A method as claimed in claim 44 wherein the hollow pile is driven into an earth formation with a lower end of said pile spaced above a bedrock formation and then after removing earth from the interior of the hollow pile, a flowable curable cementitious material is pumped into the hollow interior of the hollow pile under pressure whereby a quantity of the cementitious material emerges from the lower end of the pile to form a footing or foundation therefor.

47. A method as claimed in any one of claims 44 to 46 wherein the bearing pile comprises a plurality of hollow members joined axially by jointing members.

48. A method as claimed in any one of claims 44 to 46 wherein the bearing pile comprises elongate elements joined longitudinally to form an elongate hollow member.

49. A method as claimed in any one of claims 44 to 48 wherein the bearing pile is of any suitable cross sectional shape selected from circular, rectangular or polygonal or triangular.

50. A method as claimed in any one of claims 44 to 49 wherein the bearing piles comprise a steel reinforced cementitious core.

51 . A method as claimed in any one of claims 44 to 50 wherein the bearing piles include a plurality of spaced substantially parallel elongate steel reinforcing members extending substantially over the length of thereof, said steel reinforcing members being encapsulated in a curable cementitious composition.

52. A method as claimed in any one of claims 44 to 51 wherein the bearing piles include a ground anchor means.

53. A method as claimed in claim 52 wherein the ground anchor means comprises an anchor member coupled to an elongate tensionable anchor rod, the anchor member in use being anchored in an earth formation below a lower end of a bearing pile with said anchor rod extending through the interior thereof.

54. ,A method as claimed in claim 53 wherein ihe anchor rod is surrounded by a curable cementitious composition.

55. A method according to claim 44 wherein said pile member is located in an earth formation by:- forming first upright borehole in an earth formation; encapsulating, in said first borehole in a mass of flowable curable cementitious composition, a steel reinforcing member; allowing the cementitious material to at least partially cure to form a cementitious column; forming a further borehole substantially along an upright central axis of said column, said borehole extending throug h said column into an earth formation thereunder; inserting through said further borehole into the earth formation thereunder a mechanical earth anchor having an anchor rod extending from an upper opening of said borehole and pretensioning said anchor rod to engage said earth anchor with the earth formation; inserting into at least a lower portion of said further borehole a further mass of flowable curable cementitious material and allowing said further mass of cementitious material to at least partially cure.

56. A method as claimed in claim 55 wherein said first borehole includes a first casing .

57. A method as claimed in claim 55 or 56 wherein said first borehole extends to a bedrock layer in said earth formation.

58. A method as claimed in claim 55 or claim 56 wherein said first borehole does not extend to a bedrock layer, an enlarged cavity is formed below a lower end of said first borehole, said cavity in use being filled with a flowable curable cementitious material which when cured forms a foundation member.

59. A method as claimed in claim 58 wherein said earth anchor is anchored in said foundation member.

60. A method as claimed in claim 58 wherein said earth anchor is anchored in an earth formation below said foundation member.

61 . A method as claimed in any one of claims 55 to 60 wherein the steel reinforcing member suitably comprises a plurality of elongate substantially parallel steel rods.

62. A method as claimed in claim 61 wherein said plurality of parallel steel rods are separated by spacers to form a cage-like element having a central aperture extending longi tudinally thereof.

63. A method as claimed in any one of claims 55 to 62 wherein the steel reinforcing member is placed in the first borehole prior to introduction of cementitious material.

64. A method as claimed in any one of claims 55 to 62 wherein the steel reinforcing member is inserted in the first borehole after introduction of the flowable cementitious material.

65. A method as claimed in any one of claims 55 to 64 wherein the further borehole is entirely filled with cementitious material to form an integral steel reinforced column.

66. A building structure supported on anchored pilings formed according to any one of claims 53 to 65.

67. A building structure according to claim 66 wherein the structure extends wholly above a ground surface.

68. A building structure according to claim 66 wherein a bouyant portion of said structure is located below a ground su rface.

69. A building structure as claimed in claim 66 wherein the structure comprises a buoyant structure located substantially below a ground surface.

70. A building structure as claimed in claim 69 wherein the structure is anchored in an earth formation by anchored piles extending below a floor surface thereof and/or anchored piles extending to a ground surface.

71 . A laminated sheet pile member for use in the method of any one of claims 9 to 70, said sheet pile member comprising :- a first sheet pile member of predetermined length; and, at least one further sheet pile member laminated thereto, said further sheet pile member having a lower end adjacent a lower end of said first sheet pile member and an upper end located intermediate the opposed ends of said fist sheet pile member.

72. A laminated sheet pile member according to claim 71 including another sheet pile member laminated to said further sheet pile member, said another sheet pile member having a lower end adjacent a lower end of said further sheet pile member and an upper end intermediate the opposed ends of said further sheet pile member.

73. A sheet pile member according to claim 71 wherein respective ends of said first sheet pile member and said at least one further sheet pile member are offset to form a tapered edge on said laminated sheet pile member.

74. A laminated sheet pile member according to any one of claims 71 to 73 wherein sheet pile members are joined by any suitable process such as edge welding, plug welding, mechanical fasteners, adhesives or any combination thereof.

75. A laminated sheet pile member according to any one of claims 71 to 74 wherein the laminated sheet pile member is corrosion resistant.

76. A laminated sheet pile member according to any one of claims 71 to 75 wherein the sheet pile members may be selected from steel, synthetic resin, fibre reinforced synthetic resin or any combination thereof.