AU606215B2 - Integrated support system - Google Patents

Description

AIL( l ;I.i -I- MS1RIA (51)

PATENT

PCI

(43) 1-A-232/8 WORLD INTELLECTUAL PROPERTY ORGANIZATION International Bureau INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (51) International Patent Classification 4 (11) Internati icat u 89/02008 E02D 5/80, 17/20, E21D 20/02 Al rab i t 0.0 E21D 21/00 (43) Internatil Publicatb I 9 arc 89 (09.03.89) E21D 21/00,1 0 (21) International Application Number: PCT/AU88/00318 (81) Designated States: AT (European patent), AU, BE (European patent), BR, CH (European patent), DE (Eu- (22) International Filing Date: 19 August 1988 (19.08.88) ropean patent), FR (European patent), GB (European patent), IT (European patent), JP, KR, LU (European parent), NL (European patent), SE (European (31) Priority Application Number: PI 4003 patent), SU, US.

(32) Priority Date: 27 August 1987 (27.08.87) Published (33) Prifrity Country: AU With international search report.

(71) Applicant (for all designated States except US): INTE- This document contains the GRATED SUPPORT SYSTEMS PTY. LIMITED [AU/AU]; 895 Pacific Highway, Pymble, NSW 2073 amendments made under Section 49 and is correct for (72) Inventor; and [i ting Inventor/Applicant (for US only) SHIRLEY, Andrew, Francis [AU/AU]; 22 Gwydir Avenue, North Turram- A. O. J. P 11 MAY 1989 urra, NSW 2074 (AU).

(74) Agent: SHELSTON WATERS; 55 Clarence Street, A TRAIA Sydney, NSW 2000 A ALIAN 3 1 MAR 1989 PATENT OFFICE Title: INTEGRATED SUPPORT SYSTEM (57) Abstract A method and system of reinforcing and'supporting a soil, rock or weathered rock formation by means of lightly tensioned passive anchor units and linking means interconnecting the anchor units. Each anchor unit has a retaining limb for insertion into a prepared hole (11) in the formation and an engagement portion for engaging the linking means The method consists of inserting the retaining limb of each anchor unit into a prepared hole (11) and engaging the engagement portion with the linking means and then securing the retaining limb into the hole (11) to anchor the linking means firmly against the formation The anchor unit and linking means are then tensioned to deflect the linking means outwardly with respect to the formation between the anchor units The system describes the combination of components required to perform the method.

WO 89020 Pcr/AU8/003 I WO 89/02008 Pc/AU8/00318 1 i:? TITLE: "INTEGRATED SUPPORT SYSTEM" TECHNICAL FIELD The present invention relates to support systems for excavations in earth, rock and weathered rock materials.

BACKGROUND ART The support of such excavations has been a continuing problem for engineers, miners and the like principally due to the need to provide valid and effective means of support to ensure stability; further, the longer an excavation is left unsupported the more problems that usually arise because of the deterioration in soil and rock strength with time and large differences in soil/rock 'short-term' and 'long-term' strength values. Also, where rock or weathered rock faces are fractured or jointed, or have seams or other defects, i A it Ni

II

d 4 PCT/ AU UU S -2 AMENDED RECEIVED 2 9 AUG 1989 failures in a small part of the excavation can lead to a progressive failure of the whole excavation, sometimes with severe consequent damage to structures.

Conventional approaches to the permanent support of such excavations have involved features such as permanent structures comprising retaining walls, concrete linings sloped excavations and the like, whilst temporary support methods generally utilise steel soldiers, timber, steel sets, tensioned rock bolts, stressed anchors, etc., The present systems in use can be described as either 'active' or 'passive' systems, with active systems employing such features as highly stressed anchors, highly tensioned pre-stressing cables or rods which apply a positive force or load to the soil or weathered rock formation so as to support the excavation. The tension used in the anchors, cables or rods of such 'active' systems is typically of the order of greater than 50% of the ultimate tensile strength of the material used to form each anchor, cable or rod. Passive systems (e.g.

reinforcing dowels, semi-rigid or flexible retaining .walls, sheet piling, etc.) by contrast do not apply a positive force but allow the soil or weathered rock formation to deflect or move a small amount, thus loading the restraining passive support which then in turn resists further movement. Both active and passive systems have disadvantages; the disadvantages of an active system is that the soil or weathered rock formation 'creeps' or 'deflects' under the applied pre-stressing load, and thus the effectiveness of the 'active' support system is generally lost in the SUBSTITUTE SHEET r PCT/ AU 88 00318 -3- AMENDED RECEIVED 2 9 AUG 1989 long-term; with a passive system significant movements (20-30mm) are required before the support becomes effective and these movements are often damaging or detrimental to nearby structures, roads and services.

Further, the present technology of highly stressed anchor 'active support' systems does not permit the construction of stressed anchors with sufficient cover to reinforcement wires to enable the 'long-term' corrosion protection of the stressed anchors to be completely assured.

DISCLOSURE OF THE INVENTION The support system according to the invention aims at overcoming the above discussed problems by providing an 'at rest' or 'taut' support system which both reinforces the in-situ materials and provides restraint against movement by applying a load or pressure against the soil, weathered rock, rock formation or the like.

The low stress levels adopted in the design avoids the 'creep' problem. The structure that results from installing the lightly tensioned anchors and link catenary is thus able to resist both tensile and compressive stresses; also, where a facing such as steel mesh, steel mesh and shotcrete, or similar is used, the face support materials become integrated with the soil, or soil/rock, structure. The system can also be engineered against corrosion in the long-term. The immediate effective support of the excavation between anchors is achieved by a lightly 'tensioned' linked catenary face support system which acts in combination with the lightly tensioned anchors installed in SUBSTITUTE SHEET N, I II' ti,

I

-PCTfA. '2 0 0 318 CT i989 4 SRECEIVED 0

AMENDED

the in-situ materials. The support system can be used for both the temporary support of an excavation, as well as the permanent excavation support.

The term "lightly tensioned" as used throughout this specification refers to a tension in the range of 1.0% to 35.0% of the ultimate tensile stength of the material to which the tension is applied.

According to a first aspect, the invention provides a method of reinforcing and supporting a soil, rock, weathered rock formation or the like by means of lightly tensioned anchor units which both reinforce and support the in-situ materials when installed into the soil, rock, weathered rock formation or the like, and a linking means which interconnects two or more of said anchor units, each anchor unit having a retaining limb for insertion into a prepared hole in the formation and an engagement portion, said method consisting of inserting the retaining limb of each anchor unit into the prepared hole, engaging the engagement portion of said anchor units with said linking means to anchor the said linking means firmly against said formation and securing said retaining limb into said hole, lightly tensioning said anchor unit and said linking means so as to 'deflect said linking means.outwardly with respect to said formation between said anchor units.

Preferably said linking means is deflected into a substantially catenary shape.

For preference, said method includes securing said retaining limb to said hole by.means of one or more locking or spacing elements attached to and spaced along said limb for engagement with said hcle. SSUBSTITUTE

SHEET

i 5 According to a second aspect the invention provides a reinforcing and supporting system for soil, rock, weathered rock or the like comprising in combination two end anchor units and one or more intermediate anchor units, each anchor unit having a retaining limb for insertion into a prepared hole in the formation and an engagement portion, linking means interconnecting of said o oo engagement portions of said anchor units, securing means for securing said retaining limb to said hole, tensioning 10 means for lightly tensioning said linking means so that it is deflected outwardly with respect to said formation between said anchor units.

For preference, one or more spacing or locking elements are attached to and spaced along said limb to provide engagement with said hole.

*0*4 The light tensioning of the anchors maybe achieved either by the installation of locking elements, or 000000 elements, engaging the said hole and pressing the linking so. means firmly against the said formation, or by grouting 00 00 or cementing the annular space between the dowel and the said formation, either with cement or chemical grouts, and lightly tensioning a nut or similar device on the engagement portion of dowel or anchor against the linking means.

The anchor may also be secured in the hole by wedges or other conventional 'mechanical' means without departing from this inventive concept.

NT 0~ The light tensioning of the linking means can be achieved either by the methods as aforesaid or by the installation of wedge spacers driven between the linking means and the *fe 00 000.

*fee so go

_I

I

i

:I

I

I

-i 111 PCT/ AU 88 /00318 AMENDED RECEIVED 2 3 JUN 1989 said formation. The linking means may or may not be welded to the engagement portion of the anchor unit dependent on the design requirements.

On completion of the installation the linking means has a variable distance from the said formation and adopts 'catenary' shape which may or may not be of a mathematically definable shape. The linking means ?,ay be rDnstructed of ferrous or non-ferrous materials and the engagement between the linking means and the anchors can use a variety of methods including friction, engagement loops, hooks or holes, plate washers, or the like, depending on the design requirements.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a sectional plan of the support system showing the linking means relative to the anchor units according to the invention; Figure 2 shows a partial sectional elevation of one embodiment of the catenary linking arrangement; Figures 3 and 4 show sections through a full length of an anchor, noting that Figure 3 is an example of use with a 'chemical anchor', Figure 4 is an example using cement or other grout to secure the anchor; Figure 5 shows an elevation of the linking means using metal straps.

i kI 2 if

I

7 PCT/AU 88 /00318 AMENDED RECEIVED 2 3 JUN 1989 Figure 6 shows a partial sectional elevation of one embodiment of the engagement arrangement between the anchor units and linking means according to the invention; Figure 7 shows a partial sectional elevation of a further embodiment of the engagement arrangement between the anchor units and linking means; Figure 8 shows a partial sectional elevation of a further embcdiment of the engagement arrangement between the anchor units and linking means; Figure 9 shows a partial sectional elevation of a further embodiment of the engagement arrangement between the anchor units and linking means; Figure 10 shows a partial sectional elevation of a further embodiment of the engagement arrangement between the anchor units and linking means; and Figure 11 shows a plan and sectional elevation of the locking spacers for use with the invention.

Figure 12 shows a section through an underground excavation illustrating the formation of a rock beam using the reinforcing method according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to the drawings, the support system comprises an anchor 5 having a retaining limb 6 and an engagement portion 7 formed at the end of the anchor.

The engagement portion 7 interconnects with and engages linking means comprising transverse bars, rods, straps, or cables 8 (of ferrous or non-ferrous materials) linking t ~~PITUTE Sha_ i'J PCT/ AU 88 /00318 7a AMENDED RtCEiVE 3 JU: 1989 said anchors 5 to one another across the surface of the soil, weathered rock or rock formation 9. The tensioned bars 8 and engagement portions 7 further serve to anchor a liner or mesh 10 which is also held against the surface of the soil, weathered rock or rock formation.

F -VL STITUTE SH-EL'I4 WO 89/02008 PCT/AU88/00318 -8 8 Preferably each of these components, if made of steel, is galvanised to prevent corrosion. The components may however also be made of non-ferrous materials, including plastics, polyethylene, poly-propylene or similar materials.

The retaining limb 6 is inserted into a preformed hole 11, and can be lightly tensioned by a number of locking spacers 12 (made of steel, nylon or plastic materials) or by tensioning a nut 13 on the engagement portion against the linking means 8, after grouting or cementing or securing the anchor 5 in the hole 11. Where the locking spacers 12 are used they engage the edges of hole 11 and are in the forms of barbs so that the limb 6 may be freely inserted into the hole 11 but is restrained from removal by the spacers 12. In use, where locking spacers are used, the limbs 6 are driven into the holes 11 so that a light pretension is applied to the support system. The link transverse or catenary bars 8 are lightly tensioned where the locking spacers are used by driving or forcing the wedge spacers 14 between the transverse bars 8 and the soil, rock or weathered rock formation 9 to form the required catenary shape. This shape may also be formed by fixing the bars 8 to the end of the anchor to prevent lateral movement and bowing the bars outwardly during tensioning of the anchors.

In use, where the anchor bars or limbs 6 are grouted or cemented into the formation 9 prior to the tensioning of the linking means 8, only part of the anchor may be k SWO 89/02008 PCT/AU88/00318 9 grouted, or a 'free length' of anchor created by applying 'tape' to the anchor ,to prevent the cement from adhering to the anchor, or by using special grouts that take a period Of time to set; harden or achieve their strength.

The mesh 10 may be used in conjunction with or be replaced by a layer of shotcrete or concrete 16. The mesh is not required for many of the applications of the invention but in many cases can prove of great assistance.

Various embodiments of the engagement portion are shown in Figures 6 to 10, a looped end (Figure a threaded nut system comprising an eye (Figure 7) a plate connection (Figure 8 and Figure 9) or a bar connection (Figure Referring to Figure 6, the engagement portion 7 comprises the end of the anchor rod 6, which is returned upon itself to form loop 17. The loop 17 engages the transverse bars, rods, cables 8 which in turn bear against the mesh 10. .A layer of shotcrete 16 is applied to the support system if required. Figure 7 shows a similar arrangement to Figure 6 but a threaded eye 18 is attached to the end of the anchor limb 6.

SIn Figure 8 the end 19 of the anchor limb 6 is threaded for engagement with an tension nut 13. This arrangement is preferably used with the plate-type of linking means 8. The anchor limb 6 passes through the plate 8 and is spaced therefrom by a collar 21. A tapered washer 22 fits over the end 19 of the anchor limb 6 and bears against the plate 8 as the tension nut 13 is Vt ~1 PCT/AU 88 /00318 10 AMENDED RECEIVED 2 3 JUN 1989 tightened on the anchor limb 6. The plate 8 in turn bears against and engages the mesh 10. Figure 9 shows a similar arrangement using a standard ball washer 23 and plate 24 assembly.

Figure 10 shows an arrangement where the tension nut 13 bears against a plate 25 to engage with a linking means 8 comprising a number of bars, rods, cables or the li-ke.

Figure 11 shows in detail one embodiment of the locking spacer 12 which may be used with the invention.

The spacer is generally star-like in configuration having four outwardly extending arms 26 which are stepped in thickness towards their free ends 27. The centre of the spacer is provided with an upstanding boss 28 having an axial hole 29 for receipt of the anchor limb 6.

Strengthening ribs 30 extend longitudinally along the length of each arm 26. In use when the lock spacer is inserted in the hole 11 the arms 26 fold back with their stepped section forming a 'barb' to resist withdrawal.

Referring to Figure 12, the use-of the reinforcing system to form a rock beam is illustrated. The anchors 31 are inserted into prepared holes in the shaft roof 32. The anchors are linked by a catenary linkage 33 to form a rock beam 34 above the shaft roof 32. Additional anchors 36 and catenary straps (not show&.) may be installed in the shaft wall 37 to control sidewall pressures. The detensioned zone is kept to i minimum c t I PCT I AU 88 O0 31 8 S- 10a aENDED KcCEIVED 2 3 JUN 1989 by the use of the catenary linkage between the anchors.

The low tensions in the anchors also avoids anchor relaxation problems.

Any initial movement or failure of the shaft roof results in immediate additional tension in the anchors which resists further movement. The catenary linkage 33 acts as a tensile reinforcement for the rock beam 34 and this avoids the need for high rock compression to provide rock with apparent tensile (negative compressive) strength as is common in rock bolt systems.

Thus it will be apparent to those skilled in the art that the support system is in effect a two dimensional soil, rock, or weathered rock formation support system which takes into account the "reinforcing effect" of the anchors, installed in the formation and the tensioned supporting effect of the linking means, and where used, the surface liner; further, because the catenary shape I and semi-continuous nature of the linking means enables load-sharing between the anchors, each anchor can be i, SE l1~3l~ SWO 89/02008 PCT/AU88/00318 11 designed for a load closer to its ultimate load than would otherwise be the case, as a result, the number of anchors required is reduced to the minimum possible.

Further, and because of the great efficiency of the tensioned 'linking means' it is possible to space anchors at much greater distances apart that could be achieveO by conventional rock bolt or stressed anchor practices because the spacing of the anchors can be determined on the basis of the 'strength of the support system' rather than being determined by the in-situ properties of the earth, or rock formation, particularly joints, fissures, seams, etc.

Also, unlike conventional rock bolt systems, the anchors used in this support system may be installed at angles significantly inclined to the excavated face (up to 20-30 degrees) and thus enable the use of simplified methods of grouting.

Further, unlike conventional stressed anchor systems, the anchors used in this support system may be designed to provide reinforcement cover compatible with conventional concrete technology, thus enabling the anchors to be designed as 'permanent'.

It will be appreciated by those skilled in the art that the invention is not limited to the particular embodiments described and further embodiments of the invention are possible without departing from the spirit or scope of the invention described.

A

I

Claims (14)

1. 2. A method according to claim 1 wherein said linking means is deflected outwardly into a substantially catenary shape.
2. 3. A method according to claims 1 or 2 including securing said retaining limb to said hole by means of one or more locking or spacing elements attached to and spaced along said limb for engagement with said hole. SUBSTITUTE .LTJ a g ae 0S C 0 C 13
3. 4. A method according to claims 1, 2 or 3 including inserting one or more tensioning elements between said linking means and the said formation so as to lightly tension and outwardly deflect said linking means. A method according to anyone of the preceding claims including placing a mesh, membrane or the like between said linking means and said formation and holding said mesh in position by means of said linking means and/or said anchor units.
4. 6. A method according to claim 5 including applying a layer of shotcrete to said mesh, membrane or the like.
5. 7. A method according to anyone of the preceding claims including securing said anchor to said hole by grouting or cementing the space between said hole and said retaining limb.
6. 8. A reinforcing and supporting system for soil, rock, weathered rock or the like comprising in combination two end anchor units and one or more intermediate anchor units, each anchor unit having a retaining limb for insertion into a prepared hole in the formation and an engagement portion, linking means interconnecting of said engagement portions of said anchor units, securing means for securing said retaining limb to said hole, tensioning means for lightly tensioning said linking means so that it is defilected outwardly with respect to said formation between said anchor units. S r, F~ PCT/AU 88 /00318 4 14 RECEIVED 2 3 JUN 1989 AMENDED
7. 9. A system according to claim 8 wherein said linking means is deflected outwardly into a substantially catenary shape. A system according to claims 8 or 9 wherein said securing means comprises one or more locking or spacing elements attached to and spaced along said limb for engagement with said hole.
8. 11. A system according to claim 10 wherein said locking elements comprise essentially star-shaped plates having a number of outwardly extending arms adapted to be deformed on insertion of said limb into said hole so as to engage with said hole and resist withdrawal of said limb from said hole.
9. 12. A system according to anyone of claims 8 to 11 wherein linking means comprises one or more bars, rods, straps, cables or the like.
10. 13. A system according to anyone of claims 8 to 12 wherein said tensioning means comprises one or more tensioning elements inserted between said linking means and said formation to deflect sl.d linking means outwardly between said anchor units.
11. 14. A system according to anyone of claims 8 to 12 wherein said tensioning means comprises a nut threadingly engaging a threaded end of said limb, said nut bearing directly or indirectly against said linking means to apply tension thereto. I SUBSTITUTE SHEET] i 11OPP'- PCT/AU 88 /00318 ~pi'' 15 RECEIVED 2 3 JUN 1989 AMENDED A system according to anyone of claims 8 to 14 including a mesh, membrane or the like positioned between said linking means and said formation and engaging with said linking means and/or said anchor units.
12. 16. A system according to claim 15 including a layer of shotcrete applied to said mesh, membrane or the like.
13. 17. A method of reinforcing and supporting a formation substantially as hereinbefore described with reference to anyone of the accompanying drawings.
14. 18. A reinforcing and supporting system substantially as hereinbefore described with reference to anyone of the accompanying drawings. SUBSTITUTE -EET