GB2206172A - Rock bolts - Google Patents

Abstract

Strata are supported by using rock bolts which drill their own holes and are hollow so that a setting medium can be injected through the bolts to secure them in position. Each bolt is made up of a string 5 of hollow tubular members 6, 7 which are fed automatically into a hole in the strata 2 drilled by the leading tubular member 7 which is provided at its front end with cutting elements 8. A resin is introduced down the bore of the drilling string and into the hole 9 formed by it to set the drilling string into the strata 2. A torque is then applied to the drilling string so that it becomes a rock bolt. The tubular members are fed from a magazine 11. The resin introduced around the cutting elements 6 sets faster than elsewhere. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO ROOF BOLTS This invention relates to a method of roof bolting and to bolts for use with such a method.

In mining and tunneling installations support is often given to the roof of roadways and tunnels by drilling holes into the roof and securing bolts in these holes and then loading the bolt by applying a stress or torque to the free end of the bolt. The effect of this is that the stress is shared within the strata of the roof and the strata is held together securely.

The conventional manner of roof bolting comprises drilling a long hole into the roof, removing the drill bar, inserting a resin or cement securing medium and then inserting a bolt into the medium which is held in position until the medium sets. Once the bolt is in its set condition a torque is applied to the free end extending from the roof and the bolt is secured with this set torque by suitable means such as a nut on the free end of the bolt.

This system of installation is time consuming and also it is not very convenient in tunnels where the head room is restricted i.e. of one metre or less. It is an object of the present invention to provide a system of roof bolting which enables bolts to be set more quickly than previously and which is also suitable for use in tunnels of limited head room.

According to the present invention a method of roof bolting strata comprises drilling a hollow member into a strata to be bolted, injecting a setting medium through the hollow member to secure it in position in the strata and applying a setting torque to the bolt when the setting medium is solid.

The hollow member may comprise a plurality of tubes which are joined end to end as the hole progresses. These tubes may conveniently be fed automatically from a magazine attached to drilling equipment.

The initial rod or the single rod comprising the hollow member may be provided with a separate hollow core head or may itself be formed with a hardened and sharpened drilling element integral with it.

The setting medium which is preferably two part resin which sets on mixing may be introduced to the end of the hole through the hollow part of the hollow member and may extrude from the end of the hollow member back between the hollow member and the wall of the hole which has been drilled.

More than one type of resin may be used and one of the types of resin which is surrounding the distal end of the hollow member may be of a type which sets faster than the other resin. This enables the distal end to be secured quickly and torque applied to the rod before the rest of the resin sets to hold the rod in the stressed condition. An alternative setting member may be a cement grout.

The invention also includes a roof bolt member for use with the above method in which the member includes a hollow tube having a drilling element formed at one end, the drilling element having an aperture through which setting medium can pass from inside the tube to engage the strata.

In order that the invention may be readily understood one example of a method of roof bolting in accordance with the invention and using bolts and equipment suitable therefore will now be described with reference to the accompanying schematic drawing.

Referring now to the drawing this shows a tunnel 1 formed in strata 2 in which roof bolting equipment is placed. The equipment comprises a number of sprags through which hydraulically secure the equipment between the roof and floor of the tunnel 1. The tunnel 1 in this example is expected to be of a limited height, for example 1 metre, and the equipment is dimensioned accordingly. Attached to the hydraulic sprags 3 is a rotary percusive drive 4 which is also operated hydraulically and which applies a drilling force to a drill string 5 comprised of a plurality of rods 6, 7. The whole of the drilling string is made up of a plurality of rods which are of a hollow tubular form and the leading rod 7 is formed with a drilling head which is made out of hardened steel elements 8 welded to its leading end.The rod 7 will therefore operate as a drill bit and the elements 8 are constituted so that there is a hollow in their centre and appertures to allow drill material to fall away from the ends into the centre of the tube. The elements 8 are driven upwards into the strata 2 to form a hole 9 to receive the rock bolt.

The equipment also includes a rod clamp 10 at its tbp which guides succesive rods 6 of the drill string 5 and also an automatic magazine 11 which feeds succesive drill rods 6 and carries a suitable setting medium in this case a two part resin. Hydraulic power equipment is derived from an adjacent power pack 12. This power may be hydraulic or pneumatic or a combination of both, and fed through hose. or hoses 13 to the sprags and drills.

When drilling is to take place the drilling equipment is moved into position and the sprags 3 are set. The first rod 7 is presented to the roof with the elements 8 of its drilling end touching the roof and the rotary percursive drive 4 is operated so that the rod 7 rotates and hammers into the roof to form the hole 9. When the rod 7 has reached the limit of equipment the magazine 11 supplies a second rod 6 and this is screwed onto the ends of the rod 7. The junction between the two rods is such that there is a continuous tubular passage between the two rods.

The drive 4 is then reactuated'and the hole line is elongated until rod 6 and 7 are in position. If further rods are to be added rod 6 would be clamped by the clamp 10 and the magazine would supply a further rod onto the end of the drill string formed.

When a sufficient length of hole line has been drilled the magazine supplies automatically a two part resin which is mixed and fed up the centre of the drill string 5 so that it extrudes from the end of the drill rods 7 around the elements 8 and back between the rods of the drilling string and the wall of the hole 9. The resin is then allowed to set which is usually a very swift operation due to the nature of the components of the resin chosen and as soon as it is set the magazine supplies a plate and nut to the free end of the drill rod 6 which is always left to extend from the end of the hole 9. A torque is then applied to this free end to the required setting and a nut tightened onto the plate to secure the drilling string 5 in a set condition so that it now constitutes a roof bolt.

As an alternative instead of using a single resin a setting resin may be introduced to the part of the hole 9 away from the distal end and a very fast setting resin introduced around the elements 8 at the distal end. But this means the end of the rod 7 is quickly secured and the torque can be applied to the drill string before the rest of the resin sets.

If necessary the equipment can supply air up the centre of the drill string to flush the drill string as drilling progresses.

Alternatively another flushing medium other then air may be used if this is more convenient.

Although the above description only applies to drilling one hole it will be appreciated that a plurality of holes may be drilled simultaneously and that suitable magazines can be arranged to supply all these drilling units. The magazines are preferably preloaded on the surface and then transported into the tunnel 1 so they can easily be set in position on the equipment and time is not wasted in assembling the magazines. The magazine housing may either be re-used or if necessary may be abandoned in the tunnel.

Because the operation is basically automatic and no drill rods have to be extracted from the drilled holes and then roof bolts inserted the speed of operation is substantially greater than has previously been obtainable in roof bolting techniques. Operator skills are reduced to a minimum and merely supervision to reset the equipment and to load fresh magazines into it is all that is needed. This will give a substantial saving in time and cost.

Claims (13)

1. A method of roof bolting strata comprising drilling a hollow member into a strata to be bolted, injecting a setting medium through the hollow member to secure it in position in the strata and apply a setting torque to the bolt when the setting medium is solid.

2. The method as claimed in claim 1 including a plurality of hollow members connected to each other serially to form a drill string.

3. The method as claimed in claim 2 wherein the tubular members are fed from a magazine.

4. The method as claimed in any preceding claim and including forming a coring or drilling element at the end of the leading hollow member.

5. The method as claimed im claim 4 where the coring end is apertured.

6. The method as claimed in any preceding claim and comprising injecting a two part resin as the setting medium through the bore of the hollow member.

7. The method as claimed in claim 6 wherein two types of resin are used and in which the resin introduced at the distal end of a hole drilled by the hollow member sets at a faster rate than that introduced elsewhere in the hole.

8. A roof bolt member for use with the method of any preceding claim comprising a hollow tube having a drilling element at one end, the drilling element having an aperture there through which a setting medium can pass from the bore of the tube through engaged strata and the external surface of the tube.

9. A roof bolt member as claimed in claim 8 comprising a plurality of hollow tubes each tube having means for securing it longitudinally to an adjacent tube in such a manner as to provide a through bore.

10. Roof bolting equipment for use for the method as claimed in claims 1 to 7 and including a magazine containing a plurality of hollow members said magazine being arranged to feed the members to a drilling position and for connection serielly into a string.

11. Roof bolting assembly as claimed in claim 10 and including a power pack for supplying power to drive the hollow member in a drilling mode.

12. A method of roof bolting strata substantially as herein before described with reference to the accompanying drawing.

13. A roof bolt member substantially as herein before described and for use in a method as claimed in claim 12.