Hydraulic and earth engineering – Earth treatment or control – Rock or earth bolt or anchor
Patent
1997-02-18
2000-03-07
Neuder, William
Hydraulic and earth engineering
Earth treatment or control
Rock or earth bolt or anchor
4052591, E21D 2100
Patent
active
060331534
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to rock bolts and methods of installation of rock bolts.
A form of rock bolt is known in the mining industry which is used for increasing the strength of a wall or roof of a mine. The bolt is formed of a solid steel rod having a diameter in the order of 22 millimeters and a nut threadably fitted to one end thereof. In use, the bolt is secured in a 27 millimeter diameter hole formed in the rock strata by means of a chemical anchor in the form of a resin and when so secured the nut is screwed along the bolt to draw the strata together and thereby increase the tensile strength of a portion of the wall in which the bolt is secured. The method of installing the bolt includes drilling a hole in the rock wall, manually inserting a cartridge containing chemical (resin) components in the hole, inserting the bolt in the hole to rupture the cartridge and rotating the bolt so as to mix the components to form the chemical (resin) anchor. Such a method does, however, have a number of disadvantages, one of which is that difficulties are experienced in preventing the cartridge from sliding back out of the hole before the bolt is inserted therein.
In accordance with the present invention there is provided a method of installing a bolt comprising:
removably attaching a cartridge containing chemical components to an end of the bolt; inserting the bolt in a hole in a rock face;
rupturing the cartridge;
rotating the bolt to mix the chemical components together and transport the mixed chemical along the length of the bolt.
Preferably the cartridge is removably attached to the bolt by means of a plastically deformable sleeve that is fitted over the cartridge and the end of the bolt.
Preferably the sleeve is provided with an outwardly extending flange at the end thereof fitted over the bolt and the flange is caused to engage the rock face at the opening of the hole such that insertion of the bolt into the hole forces the bolt through the sleeve to drive the cartridge into the remainder of the hole.
In another aspect, there is provided a bolt having a deformable sleeve fitted thereto, the sleeve carrying a cartridge containing chemical components in an open end thereof Preferably, the sleeve has a flange extending outwardly from the end of the sleeve fitted to the bolt such that insertion of the bolt into a hole in a rock face causes the flange to engage the rock face at the opening of the hole such that further insertion of the bolt into the hole results in the bolt passing through the sleeve and carrying the cartridge into the remainder of the hole.
Preferably the flange forms a metal plate for engagement with a securing nut of the bolt.
Preferably the bolt is hollow such that the reduced amount of material used in construction of the hollow bolt, as compared to a solid bolt, will lead to some cost advantage. However, the nature of a chemical anchor which is preferably a resin anchor requires that the diameter of the bolt must be only slightly smaller than that of the hole in which it is inserted, say in the order of four millimeters whereby to provide a two millimeter angular gap therebetween, and in the case of hard rock mining the holes are in the order of 50% larger in diameter than the holes used in coal mining. This increased size is a function of the drilling machinery used in hard rock mines itself being larger than that used in coal mines. Chemical anchors are, therefore, clearly not suitable for use with such diameter bolts when the spacing between the bolt and the walls of the hole would be too great for a chemical anchor to be effective.
Due to the increased diameter holes a different method of installing rock bolts is generally practiced. This involves attachment of an expandable "shell" to an end of a bolt forming a mechanical anchor, inserting the bolt into a hole, whereby once fully inserted the shell is expanded to grip the walls of the hole and thereby locate the bolt, and injecting cementacious grout into the annular region between the bolt and the walls of the hole.
It would, of
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Industrial Rollformers Pty. Limited
Lagman Frederick
Neuder William
LandOfFree
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