AU701596B2

AU701596B2 - Anchoring of retaining walls

Info

Publication number: AU701596B2
Application number: AU37800/95A
Authority: AU
Inventors: Aw Ho Choon; Yu Hain Teck
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-11-11
Filing date: 1995-11-10
Publication date: 1999-02-04
Anticipated expiration: 2015-11-10
Also published as: AU3780095A; SG34302A1

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION sTfIA1U)" PATENT *0 e,

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Applicants: 1) Aw Ho CHOON and Yu Hain TECK Invention Title: ANCHORING OF RETAINING WALLS The following statement is a full description of this invention, including the best method of performing it known to me/us: TItle Aiihring of Retaizining Walls Backqxzoum of Invention This invention relates to a method andapparatus for anchoring retaining walls and in particular, relates to a method of anchoring a sheet pile retaining wall or diaphragm wall.

Decriptiau of the Prior Art Excavations usually require the use of retaining wall to prevent collapse of the excavated Pit, The retal-ing wall is often described as a sheet pile retaining wall o= diaphragm wall.. There is a need to anchor the retaining wall to the eaz-th that is behind the wall to prevent collapse of the wall into the 'excavation. one way of anchoring sheet pile retaining walls is to drill a hole through the wall into the earth behind the wall adjacent the pooition, where the wall meets the earth on tche foxward 'a side of the wall. The hole is usually inclined dowilwardly a. and is then ezcavated to provide a cylindrical passage *behind the retaining wall. A. bar, or strands are then inserted into the hole and the hole is grouted. After delayv of between three and seven days, to allow the outto set, a plate and nxut may be attached to the bar -which can then be tensioned to place the anchor into a stressed working condition. As excavation% continues, the operation can be repeated at lower levels of the retaining **wall.

Th convutional method of anchoring retaining *fee$: walls of this kind suffers from a number of problems that are associated with the difficulties of drillin4 the hole accurately,the difficulties in flushing or removing the material in the hole, the difficulties in ensuring that drilling of the hole does not disturb the surrounding soil, the problens of the hole collapsing during dzilling, the need to grout the hole around the bar~s or strands, the delay in allowing the -2grout to set and harden, the uncertainty of knowing whether the anchor is operating satisfactorily and the problems that are encountered in removing and replacing the anchor should it prove unsatisfactory. it is these problems with conventional methods of anchoring retaining walls that have brought about the present invention.

Summary of the Invention According to the present invention there is provided a method of anchoring a sheet pile retaining wall or diaphragm wall by using reaction force provided by said sheet pile retaining wall or diaphragm wall characterised by the steps of: la~cing a jacking boom against the forward face of the wal., placing an elongated anchoring member on the jacking boom with one end adjacent an opening in the wall, 90,positioning a pair of jacks between a reaction surface and the other end of the anchoring member, operating the pair of jacks to push the anchoring member through the opening in the wall and into the earth 90 on the other side of the wall, said anchoring member in tension against said retaining wall after the anchoring member has been jacked into position, and attaching said boom to the forward face of the 9 wall to provide said reaction force and allowing the pair of 'jacks to engage the opposite end of the boom to push said anchoring member.

an apparatus for anchoring a sheet pile retaining wall or diaphragm wall according to the method of any one of claims 1 to 5 characterised by a jacking boom adapted to support an elongate member and a pair of jacks, means to operate the pair of jacks whereby the retaining wall is used as a reaction member so that operation of the pair of jacks causes the anchoring member to be forced through an opening in the retaining wall into the earth behind the retaining wall.

\\mlbO~h~mo$Cgcvt\Xep\3800gS~oo24/11I90 'M Flo I 2a- Description of the Drawings Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a plan view of an excavation supported by a sheet pile retaining wall of rectangular goo* 6 V.0

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.9.9l om$ColYKep3809.dc2/19 L3 profile illustrating a jacking method for anchoring the retaining wall, Figure 2 is a plan view of a Jacking assembly shown in Figure I, Figure 3 is a side sectional view of the jacking assembly taken along the lines X-X in Figure 2, Figure 4 is a sectional view taken along the lines Y-Y of Figure 3, Figure 5 is a plan view illustrating another means of supporting a jacking boom of the assembly, Figure 6 is a plan view showing an opposed jacking arrangement, Figure 7 is a plan -iew showing a still further jackiig arrangement, and Figure 8 is a cross-sectional view taken along the lines X-X of Figure 7.

0**9 Description of the Preferred mbodi nt -nl The method and apparatus for anchoring a sheet pile retaining wall or diaphragm wall essentially comprises 20 a jacking boom 10 arranged to house a hydraulic jack 20 and a steel Section 30 that is to be jacked into position through an opening 32 in the retaining wall 40. The hydraulic jack 20 is powered by a hydraulic power pack 21 which is a free standing unit which is coupled to the jack through suitable hydraulic hose attachments 22, 23. The boom 10 comprises 'O ubtantial elongate steel member of or cross-section with a plate 11 welded across one end. The plate 11 is apertured at" futr locations 12 and is 9**C adapted to fit onto four bolts 13, 14, 15, 16 that are welded or otherwise secured to the front face 41 of the retaining wall 40. The boom 10 is bolted onto the front face 41 of the retaining wall 40 to be supported in a cantilevered fashion therefrom. The opposite end 17 of the boom is also supported by a grouznd engaging support 18 that engages either side of the boom section to support the load of the boom 10 at that end. The boom also includes a "p -4 displaceable bearing plate 35 in the form of a rectangular steel plate that can be positioned across the boom as shown in Figures I and 2. The boom includes pairs of parallel spaced apart bearing blocks 36, 37, 38, 39 which are in the form of solid square steel bars that are welded onto the steel section of the boom. As shown in Figures 1 and 2, the bearing blocks 36, 37, 38, 39 are equally spaced along the length of the boom and the spacing of the blocks 36, 37, 38, 39 is such that the plate 35 can rest against the blocks and is prevented from longitudinal displacement in one direction along the length of the boom. As shown in Figure 3, the pairs of bearing blocks 35, 37, 38, 39_also act as guides guiding the passage of the steel section The hydraulic jack 20 is positioned with its rear face 24 engaging the bearing plate 35 and its front face or piston engaging the free end of the steel section 30 through the inteediazy of a force transfer plate 26.

The steel section 30 that is to be jacked through Sthe opening 32 in the retaining wall 40 into the earth structure can be of a variety of cross-sections but is preferably of circular cross-section in the form of a hollow steel tube. The opening 32 iS formed by cutting the steel sheet pile that constitutes the retaining wall prior to the jacking operation. In the case of a diaphragm wall the opening 32 may be formed by drilling or other suitable means. The steel section 30 or anchoring member is 0 preferably in the form of a hollow-tube. However, it is envisaged that other sections such as a channel section, I section or H section may also be used as the anchoring member that is jacked into position bebind the retaining 0 °wall.

The force transfer plate 26 once engaged by the piston 25 of the hydraulic jack 20 engages the end of the steel section 30 which in turn engages the earth behind the retaining wall 40. The resistance of the earth causes the jack 20 to press up against the bearing plate 35 and in the embodiment shown .in Figures 1 and 2, the rear face of the o 0 *00 0609 o o0 006 00*04: 0 a 6e o flO* o 0 040 0 0 00 0 0*0 *o 0 00e*00 0 0 0 0 0000 0o Q boom 10 acts as a reaction through its association with the bolts 13, 14, 15, 16 on the fro-at face 31 of the retainng wall 40. Thus, as the hydraulic force from the power pack 21 is increased, the piston 25 forces the steel fMectiQn into the eazth forming a plug of conpressed earth witidn the first part of the hollow tube. When the hydraulic piston 25 has completed its stroke, it is then returned to the retracted position at which time the bearing plate is positioned further along the length of the boom against a pair of bearing blocks 37, 38, or 39 adjacent the end 24 of the jack 25.. The Jack 25 can thus be moved up as the section 30 is inserted into the retaining wall 40. This operation is repeated until the steel section 30 is inserted virtually into the opening 32 in the retaining wall 40. At this stage the nuts can be undone from the bolts 13, 14, 15, 16 on the front face 31 and the boom can be removed for use to install the next steel section.

Although not shown in the drawings it is understood that once the steel section 30 or anchoring 20 member is jacked into position a large bolt (not shown) is welded to the end of the section with the threaded shank facing forwardly. A channel section member is welded above and below the bolt and an apertured bearing plate is positioned on the bolt against the channel section members.

25 A nut is then placed on the etd of the bolt and tesioned to secure the anchoring member to the front face 31 of the retaining wall.

The hydraulic power pack 21 is selected to provide hydraulic pressure of up to 10,000 lbs f/in a-nd is 30 capable of operating a 100 Toil hydraulic cylinder at satisfactozy speed measured by the length of stroke per minute. The power pack includes control valves which control flow of hydraulic fluid and consequently the operating pressures.

In this embodiment, it is the action of the bolts 13, 14, 15, 16 andL the end plate 35 of. the boom 10 that effectively give the reaction allowing the jack to 0000 0 9 0000 0000 0000 0~ 00 0 00 00 000 00 09 0* 0 0 09 0 0 0 0900 00 00 0 00.900 0 0 0 *0 0-999 0 0009 9 0 0000 0 .09000 0 0 -6effectively press the steel section 30 into the earth behind the wall 30. Consequently, it is the retaining wall through its bolted association with the boom that provides the reaction member that effects the jacking force. In the embodiment of Figures 1 to 4 the thrust of the Jack 25 is exerted on the jacking boom 10 producing a pushing force onto the bolts 13, 14, 15, 16 which in turn transfer the force to the sheet pile retaining wall 40. During the jacking process the sheet pile wall 40 is subjected to bending under the pushing action of the jacking boom The force which counters this pushing force comes from the stiffness of the sheet pile section or the diaphragm wall itself and the passive resistance of the earth behind the wall- However, in other embodiments, a different form of reaction may be used and exami!es of these embodiments are shown in Figures 5, 6, 7 and 8. In Figure 5, the boom extends across opposed retaining walls 40 and 50 so that the end 34 of the boom i0 acts as the reaction -mer 20 through its abutting contact with the opposing wall 50. In this case, there is no need to bolt the boom 10 to the forward face 31 of the front wall 40. It is simply supported in a horizontal or slightly inclined manner with the reaction force always being provided by the opposite retaining wall In the embodiment shown in Figure 6, a pair of jacks 25a and 25b are located in a coaligned manner with the boom 10 with the hydraulic jacks being mounted opposed to one another but backing on against the reaction plate 30 between the ends of the jacks 25a and 25b. In this case, the boom 10 extends across the gap between opposed retaining walls 40 and 50. It is the abutment of the two jacks 25a and 25b that causes the reaction force and there is no need for the boom 10 to be secured to the front face of either retaining wall 40 or in the embodiment shown in Figures 7 and 8, partial excavation takes place within the excavated axea

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9999 9949 *a *9 'S 99 99 ~,99* 99 99 4, 9 9 9 99 0 999 9 9999 9999 -7 between the retaininga walls 40 and 50. BY positioning a load distributing bearing plate 60 of substantially large cross-section against the edge of the upper level 51, the boom 10 may be positioned horizontally to be supported about suitable tresses in the lower level 54 with the rear of the boom 10, and in consequence the hydraulic jack abutting the bearing plate 60. The reaction force is then distributed through the bearing plate 60 and the hydraulic jack 25 can be operated to drive the steel section 30 into the earth behind the wall 40. in this embodiment, there is also no need fo= the boom 10 to be a.ttached to the front face of the retai-iing wall t is understood that the boom and jack are usually positioned horizontally, however, it is possible for the boom to work on an incline to the horizontal meaning that the steel section 3 0 can be* driven into the earth behind the retaining wall at an incline to the horizontal.

The method and appara.tus described above has the 20 advantage over conventional methods in that there is no n~eed to drill a hole and flush/remove the soil prior to; location of the anchoring member. The drilling and f,lushing of a hole causes a number of problems such as loosening of the soil peripheral to the hole thus adversely 25 affecting the soil properties. The method of the subj ect application that operates by forcing or jacking in a shaft or steel section has the effect of compressing the soil. The compression of the soil surrounding the shaft improves a number of characteristics of the soil and enhances the 30 strength and integ-iitY of the retaining wall. Inx s:Ltuations where the soil is prone to collapse, the drilling techaicmue- is very diff'icult to carry out due to the unstable nature of the soil. This is not a problem with the method described above. Another advantage of the anch:oring technique dpscribed above is that once the 999999 9 9 999999 9 9999 0 99..

9 *9999* 9 9 I-8 Section has been positioned behind the retaining wall, the characteristic of the anchor is known unlike the more conventional anchor where there is the unknown quantity of the quality of the soil that has been drilled and there is a delay whilst the grouting associated with the steel member of the anchor sets. The conventional methods siffer from the problem that a number of anchors may be positioned before it is realised that they have failed to reach the desrired characteristics. When some anchors fail the prescribed tests, it is often too late to put in replacement anchors and thus the correction of these faults is very time consuming and consequently costly.

A very important advantage that flows from the method of the subject application concerns the use of much cheaper machinery. It is envisaged that the method of the subject application is much cheaper than the conventional method. The cost effectiveness of the method relates not only to the simplicity in operation but the high success rate of the anchors in comparison with the many problems 20 that flow from the conventional methods.

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Claims

2. The method of claim 1 by providing bolts to "attach said boom to the forward face of said wall to provide the reaction force. retaining walls with the rearward end of the boom engaging one retaining wall which acts as the reaction surface and operating the pair of jacks to push the anchoring member through the opening in the opposite retaining wall.
4. The method accordi g to claim 3 characterised by forming openings in both retaining walls, placing an anchoring member adjacent each opening, positioning the pair of jacks back to back against the anchoring members \\lsaltbt\h msS\llg~y~t cp\fl8~dl95-.d? 2C/1119B. and operating the pair of jacks to push both anchoring member into the openings and into the earth behind the retaining walls.
5. The method according to either claim 1 or clai 2 wherein the retaining wall borders a tiered excavation, the method being characterised by positioning the boom between one wall and the edge of the upper tier, positioning of a force distributing plate between the boom and the edge of tier whereby the reaction surface is the force distributing plate.
6. Apparatus for anchoring a sheet pile retaining I..e wall or diaphragm wall according to the method of any one .t 15 of claims 1 to 5 characterised by a jacking boom adapted to *4 support an elongate member and a pair of jacks, means to I A operate the pair of jacks whereby the retaining wall is used as a reaction member so that operation of the pair of jacks causes the anchoring member to be forced through an opening in the retaining wall into the earth behind the retaining wall. 4i44
7. A method of anchoring a sheet pile retaining wall t 4 or diaphragm wall substantially as described herein with S:f 25 reference to and as illustrated by nd taccompanying drawings.
8. An apparatus for anchoring a sheet pile retaining wall or diaphragm wall substantially as described herein with reference to and as illustrated by the accompanying drawings. Dated this 24th day of November 1998 AW HO CHOON and YU HAIN TECK By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent Attorneys of Australia \toelbbt\hca S\c~;lvty/Xesp\31813rpSd~~ 21it1196 ANCHORING OF RETAINING WALLS Abutract Method of anchoring a sheet pile retaining wall or diaphragm wall by placing a jacking boom (10) against the forward face (31) of the wall (40) supporting an elongate steel anchoring member (30) on the boom against a bydraulic jack (25) positioned on the boom The method includes activating the jack (25) to force the anchoring member (30) through an opening (32) in the front face (31) of the all (40) and into the earth behind the wall The retaining wall (40) or the opposite retaining wall (50) is used as the reaction member to effect transfer of the Jacking force to the anchorinj member Dooa qoa *ee 060 006 60 9e Ii 0 4. 9