Hydraulic and earth engineering – Earth treatment or control – Rock or earth bolt or anchor
Reexamination Certificate
2001-07-30
2004-03-02
Will, Thomas B. (Department: 3671)
Hydraulic and earth engineering
Earth treatment or control
Rock or earth bolt or anchor
C411S004000, C464S033000
Reexamination Certificate
active
06698980
ABSTRACT:
BACK GROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a rock stabilizing apparatus and method for anchoring unstable rock formations in underground mines and more particularly relates to an apparatus and method using a tension member that is embedded into a hardenable adhesion material for creating stabilizing forces within an unstable rock formation.
2. Background of the Invention
In underground mines it is important to secure the roof and walls of a tunnel against collapse of unstable rock formations that will hang from stable rock formations. Such situations may be caused by having to tunnel through naturally fractured rock formations or by blasting operations within the mine. Scaling the roof and walls of a newly formed tunnel is necessary to remove loose rock that could easily collapse. Scaling is a process whereby a miner uses a long pole to pry and remove loose rock, called scale, from the roof and walls of the tunnel. After removing the scale it is necessary to anchor the walls and roof of the tunnel to more stable rock formations. This is accomplished through the use of devices that are generally called rock bolts. Holes are drilled into the walls and roof of the tunnel a sufficient distance to penetrate the unstable formations surrounding the roof and walls of the tunnel and enter stable formations. Rock bolts of adequate length are then inserted into the holes. The inserted end of the rock bolt is anchored to the stable rock formation using mechanical expansion clamps or hardenable adhesion material. The end of the rock bolt protruding from the hole is generally threaded. A nut and anchor plate is often used to apply a stabilizing compressive force to the rock formation and tension the rock bolt supporting the roof and wall loads. Steel netting may be strung across the roof and walls from plurality of rock bolts for further security. As well, concrete is often applied to the surfaces of the tunnel providing even more strength to the tunnel. Where adhesion material is used to anchor the rock bolt to the stable rock formation the rock bolt can be used to rotate and mix the adhesion material so that it will cure and bind the bolt to the walls of the borehole.
A number of roof bolts and anchoring systems using hardenable materials have been proposed for use in mining applications. One example is found in U.S. Pat. No. 4,904,122 “Anchoring Device, Such As A Rock Anchor” issued to Herbst and Schnitzler in 1990. This device is not well suited to applications where the reinforcing rod is used to mix adhesion materials during curing because there is disclosed no way to rotate the rod within the hole. Another example is found in U.S. Pat. No. 4,051,683 “Method and Apparatus For Supporting A Mine Roof” issued to Koval in 1977. This system has a number of disadvantages. It relies upon a plurality of parts making it difficult to use in underground mining operations. It relies upon on a relatively complex coupling device that that will be expensive to manufacture and therefore adds expense to the cost of the overall system. The reliance upon a coupling between the bolting rod and the reinforcing rod creates a weak link that may fail during rotation necessitating the entire system and adhesion material to be removed from the hole. A similar system is found in U.S. Pat. No. 5,785,463 “Combination Cable Bolt System” issued to Eaton et al in 1998 having similar deficiencies relating to complexity, expense and inherent weaknesses caused by coupling mechanisms
Therefore there is a continued need for an apparatus and method for anchoring unstable rock formations in underground mines using a tension member with adhesion materials that is simple and inexpensive to manufacture and use and does not rely upon coupling mechanisms with their inherent weaknesses.
OBJECTS OF THE INVENTION
It is an object of the present invention to overcome the deficiencies in the prior art.
It is a further object of the invention to provide a rock stabilizing apparatus and method for anchoring unstable rock formations in underground mines.
Yet another object of the present invention is to provide a rock stabilizing apparatus and method for anchoring unstable rock formations adapted for applications where adhesion materials are used to fix the reinforcing member within the borehole.
Still another object of the invention is to provide a rock stabilizing apparatus and method for anchoring unstable rock formations in underground mines using a tensionable member and adhesion materials that is easy and inexpensive to and manufacture; does not rely upon a plurality of dependent parts; and, does not rely upon a coupling device.
SUMMARY OF THE INVENTION
The objects of the present invention are satisfied through the provision of a rock stabilizing apparatus and method for anchoring unstable rock formations adapted for use with adhesion material. The apparatus comprises an elongated reinforcing member having a threaded portion at a bottom end; and, a top end adapted to be embedded permanently within a hardenable adhesion material within the drilled hole. The threaded bottom portion and the top end are at opposite ends of the same member. The reinforcing end is inserted into a drilled hole through the unstable rock formation into stable rock. The drilled hole is sufficiently deep so that when the member is entirely inserted into the drilled hole the threaded end is partially inserted into the drilled hole. There is at least one bearing plate member retained on the threaded bolt portion of the reinforcing member. The threaded portion has a top end and a bottom end, and can be rotated through the centre of the plate. The plate can be advanced so that it abuts against the rock face for transmitting compressive forces to the rock face. There is at least one nut threadably advanceable over the threaded portion. The nut acts to advance the bearing plate to the rock face and applies a tensioning force into the reinforcing member when it is tightened against the bearing plate. A shearing element is provided within the nut that shearably fixes the nut to a predetermined and variable position on the threaded portion of the reinforcing member. The nut has a first temporary pre-torgue
max
operating position wherein it is fixed to the member-threaded portion at its bottom end by the shearing element thus permitting the nut and member to be rotated as one. The first temporary pre-torque
max
operation position is adopted when it is necessary to mix adhesion material within the borehole for curing. The nut has a second post-torque
max
permanent operation position that is adopted once the shearing element has sheared at torque
shear
and the nut is free to advance along the threaded portion of the reinforcing member. This second post-torque
max
operating position is adopted when it is necessary to abut the bearing plate against the rock formation and then further torque the nut to torque
max
thus adding compressive forces to the rock formation through the bearing plate and also adding tensile forces to the reinforcing member anchored within the drilled hole. The shearing element is adapted to shear at torque
shear
when a predetermined amount of torque is applied to the nut. Torque
shear
occurs at a predeterminable torque that is made dependent upon the curing properties of the adhesion material. The breakage of the shearing element at torque
shear
will not damage the threads on the member. Additionally, the remnants of the shearing element, once sheared, are retained within their respective bores to eliminate safety hazards that may result from energized pieces of the shearing element acting as projectiles.
A method is provided for using a rock stabilizing apparatus in underground mining operations. A hole is drilled through unstable rock strata a substantial distance into stable rock strata. The reinforcing member is prepared by threading at least one nut onto the threaded end of the reinforcing member and then fixing the nut to the threaded portion of the member using at least one shearing element. Typ
Mayo Tara L.
Stewart Mining Products Inc.
Will Thomas B.
LandOfFree
Rock stabilizing apparatus and method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Rock stabilizing apparatus and method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rock stabilizing apparatus and method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3241781