AU594846B2

AU594846B2 - Method of stabilizing a rock structure and stabilizer therefor

Info

Publication number: AU594846B2
Application number: AU82593/87A
Authority: AU
Inventors: Karl Gosta Lindh
Original assignee: Atlas Copco AB
Current assignee: Atlas Copco AB
Priority date: 1986-12-16
Filing date: 1987-12-16
Publication date: 1990-03-15
Anticipated expiration: 2007-12-16
Also published as: NO875236D0; SE8605408D0; FI875508A; JPS63223300A; EP0272233A1; PL269500A1; CA1286603C; HUT48711A; AU8259387A; NO875236L; ZA878649B; CS924387A2; CS274416B2; FI875508A0

Description

COMMONWEALTH OF AUSTRALIA 5948,4 PATENTS AC'* 1952-6er COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: *CQmple~fe Specification Lodged: Accepted; a' Published: Priority 'TIll docuincat contains t* aim.nkmests made uxir 8.ctmn 49, and It awreat hv, p*Aitb, elatad Art: *Name of Applicant; AdldresS of Applicant: AOtual Inventor: Address foi Service ATLAS COPCO AKTTESOLAG Nacka, Sweden KARL COSTA LINDH EDWD. WATERS SONS, 60 QUEE N STREETi MELBOURNE, AUSTRALIA, 3000.

Complete Specification for the invention entitled-.

METHOD OF STABILIZING A ROCK STRUCTURE AND 8TABILIZER

THEREFOR

The following statement Is a full description of this invention, Including the best method of performing It known to .,US -2- Method of stabilizing a rock structure and stabilizer therefor This invention relates to a method of stabilizing a rock structure and a stabilizer adapted for performing the method.

S 0 In US patent 4.423 986 a rock stabilizer is shown which comprises a closed longitudinally folded tube which is pressurized to expand to 5 anchor in the borehole. This bolt provides an outstanding anchoring and the accepted diameter range of the holes is extremely wide.

However, the bolt is comparatively expensive.

In the Swedish patent specification 8502981-7 a tubular rock stabilizer is shown which is expanded past the size of the drillhole 90.

10 by means of an expansible body inserted into the stabilizer. Thereby .e the stabilizer is anchored in the drillhole by elastic compression of the rock surrounding the stabilizer. This allows the use or cheap 5* stabilizers but the expansible body has a limited operational life due to the necessary high pressure.

15 In US patent 3 349 567, a rock stablizer is shown which comprises a 9 i tube to be inserted in the borehole and then expanded at discrete points Lv pulsed magnetic fields induced by high voltage pulses in a coil on a probe that is temporarily inserted in the stabilizer. The stabilizer is cheap but the necessary equipment very expensive and there are considerable safety hazards due to the high voltage.

It is an object of the invention to provide an efficient method of stabilizing a rock structure enabling the use of simple stabilizers which together with the method provide a low total cost for stabilizers as anchored in the rock. _I_1/I 1~ In accordance with a first aspect of the present invention there is provided a method of stabilizing a rock structure comprising providing an elongated expansible closed tubular stabilizer of a material capable of plastic elongation under action of an expansive load the stabilizer being provided with substantially circular cross-section and a perimeter equal to nD, (where D is a transverse dimension of said tubular stabilizer prior to expansion) drilling a hole in the rock of a diameter somewhat larger than D to permit the tubular stabilizer to be freely inserted in the drillhole, inserting the stabilizer in the drillhole, coupling an outer end of said stabilizer to an external source of hydraulic high pressure fluid, pressurizing the S* stabilizer by a controlled supply of hydraulic high pressure 15 fluid to such an extent that the stabilizer is widened past 5 S. the amount of D by radial expansion thereby filling the irregularities of the drillhole and widening the rock elastically therearound, whereafter the stabilizer is relieved of pressure, emptied and left anchored in the drillhole by shrinkage fit between the rock and the stabilizer.

According to a second aspect of the present invention there is provided a tubular rock stabilizer of substantially circular crods-section to be anchored by the method as set out in the preceding paragraph in a drillhole drilled in a rock structure, comprising a closed elongated Stubular body of a plasticably expansible material having a perimeter equal to rD diumensioned to be freely insertable into a drillhole of a diameter somewhat larger than D, S (where D is a transverse dimension of the stabilizer before expansion) the stabilizer being closed at one end which is a bottom end thereof, an open inlet at an outer end portion of said stabilizer opposite said bottom end, and means removably connectable to said inlet for controllably supplying hydraulic high pressure fluid via said inlet inwardly of said stabilizer to widen said stabilizer by radial expansion substantially past the perimeter value nD, -3a- Further preferred features and aspect of the present invention will become apparent from the following description given with reference to the accompanying drawings, in which: Fig. 1 is a longitudinal section of a bolt inserted in a drill hole prior to expansion.

Fig. 2 is a section on the line a-2 in Fig, 1.

Fig. 3 shows the bolt in Fig. 1 after anchoring by radial expansion.

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4 Ce Fig 4 shows an alternative outer end portion for the stabilizer in Fig 1.

Fig 5 shows an expansible stabilizer section intended for an extension build-up of stabilizers provided by one or more interconnected such sections, and outwardly terminated by the end portion of Fig 4.

Fig 6 is a closure plug for the bottom en tion of such an extension build-up.

Fig 7 is a non-expansible stabilizer section providing an 10 alternative for one or more extension section according to Fig The rock stabilizer 10 or roof bolt shown in Fig 1 comprises a closed elong.ted straight cylindrical tube 11 of steel of a property providing uniform elongation under expansive load. A suitable steel 15 given as an example is the deep drawing quality steel Swedish standard SS 141147. If the outer diameter of the tube 11 is designated D cm, its pe-imeter would be I D cm. Unchanged in perimeter the tube may have a slightly welled or somewhat irregular cross-section for increased stiffness. The bottom end of the tube 11 20 is closed tightly by a circular plate 12 welded to the tube 11 preferably by friction welding. To the outer end is similarly tightly connected a flange 13 with an outwardly protruding cylindrical boss 14. An inlet 15 of a passage 16 to the interior of tube 11 is provided on the boss 14.

The stabilizer 10 is freely inserted into a drillhole 20 drilled in a rock structure 21 with a diameter somewhat larger than D cm. While inserted, the stabilizer 10 by its flange 13 keeps a supporting plate 22 which surrounds the tube 11, resting against the rock 21.

Before or after insertion a diagrammatically indicated chuck preferably of the type shown in US patent 4 423 986, Figs 1, 10, is slipped and tightly set onto boss 14 and the opening 15 is supplied under pressure control of a valve 26 by hydraulic high pressure fluid under a pressure of up to 500 bar from a pump 27. This pressurizes the interior of the stabilizer 10 causing a radial 86038 ZT 861216 expansion thereof which fills the normal always present irregularities of the drillhole and widens the surrounding rock elastically as depicted in Fig 3. The pressure is then relieved and the chuck 25 removed so that the stabilizer eventually is emptied of fluid. Although some shrinking may take place at relief, the stabilizer remains firmly anchored in the drillhole 20 due to the significantly larger shrinkage fit of the rock 21 around the expanded stabilizer 10. A suitable manometer or other instrument in the hydraulic supply may be used for increased control during the 10 radial hydraulic expansion of the stabilizer As an alternative the stabilizer 10 may be provided instead of the boss 14 with a coupling nipple 28 of the type shown in Fig 4. In such case a quick release coupling may be used for the hydraulic high pressure fluid supply.

15 In order to match long drillholes by short lengths of expansible stabilizers of the type in question, extensible expansible tubular stabilizer sections 30 according to Fig 5 may be used, at will combined with non-expansible (narrow channel 36) sections 31 of the type shown in Fig 7, both sections 30,31 having respectively male and female coupling means 34,35 for tight interconnection of their n ends. A head 32 with a coupling means formed by a threaded hole 33, C(0' 0 Fig 4, provides the outer end of the extended stabilizer, to which for example one or more non-expansible sections 31 can be tightly connected as by threaded coupling means 34,35 and terminated within the drillhole by one or more expansible sections 30 coupled thereto, the last of them closed by a threaded plug 38, Fig 6.

86038 2T 861216

Claims

1. A method of stabilizing a rock structure comprising providing an elongated expansible closed tubular stabilizer of a material capable of plastic elongation under action of an expansive load, the stabilizer being provided with substantially circular cross-section and a perimeter equal to RD, (where D is a transverse dimension of said tubular stabilizer prior to expansion) drilling a hole in the rock of a diameter somewhat larger than D to permit the tubular stabilizer to be freely inserted in the drillhole, inserting the stabilizer in the drillhole, coupling an outer end of said stabilizer to an external source of hydraulic high pressure fluid, pressurizing the stabilizer by a controller supply of hydraulic high pressure fluid to such an extent that the stabilizer is widened past the amount of D by radial expansion thereby filling the irregularities of the drillhole and widening the rock elastically therearound, whereafter the stabilizer is relieved of pressure, emptied and left anchored in the drillhole by shrinkage fit between the rock and the stabilizer.

S.2. The method of claim 1, wherein the stabilizer is expanded to anchor in the borehole over substantially the entire le.gth of the stabilizer.

3. The method of claim 1, wherein the stabilizer is extended to match long drillholes by interconnecting for hydraulic communication inner and outer ends of a sufficient number of adjacent stabilizers.

4. The method of claim 4, wherein the stabilizer is extended by non-expansible stabilizer sections.

S. A tubular rock stabilizer of substantially circular cross-section to be anchored by the method according to claim 1 in a drillhole drilled in a rock structure, -7- comprising a closed elongated tubular body of a plasticably expansible material having a perimeter equal to RD dimensioned to be freely insertable into a drillhole of a diameter somewhat larger than D, (where D is a transverse dimension of the stabilizer before expansion) the stabilizer being closed at one end which is a bottom end thereof, an open inlet at an outer end portion of said stabilizer opposite said bottom end, and means removable connectable to said inlet for controllably supplyinq hydraulic high pressure fluid via said inlet inwardly of said stabilizer to widen said stabilizer by radial expansion substantially past the perimeter value nD. S go

6. The stabilizer of claim 5, wherein said stabilizer S. is expansible over substantially the entire perimeter Sthereof. S.

7. The stabilizer of claim 5, wherein said outer end portion is a cylindrical boss and said inlet is disposed on the periphery of said boss,

8. The stabilizer of claim 5, wherein the ends of the stabilizer provide male and female coupling means, respectively, thereby to enable stabilizer extension by intercoupling of two or more identical stabilizer sections. S I I

9. The stabilizer of claim 8, wherein the stabilizer is extended by one or more non-expansible stabilizer a section. S DATED this 5th day of December, 1989. ATLAS COPCO AKTIEBOLAG WATERMARK PATENT ATTORNEYS QUEEN STREST, MELBOURNE, VIC. 3000. IUS SAUSTRALIA Disk 0061/1.42 SOFFIG MG iiiL-_l