Drilling assembly for inserting a rock bolt
OwnerClarissa Elizabeth McLareninventor
Life of this patent
Estimating the term…
Abstract
A drilling assembly is disclosed for drilling a borehole in a rock body and inserting a rock bolt within the borehole in a single pass. The drilling assembly includes an elongated drill string having a downhole end. A drill bit is detachably joined to the downhole end of the drill string, with the drill bit having an external screw thread extending in an axial direction of the drill string. The drill string is surrounded by a rock bolt sleeve that has a thread engaging formation at or near its downhole end and that is arranged to cooperate with the external screw thread of the drill bit so that the drill bit is able to be screwed into the rock bolt sleeve.
Claims22
A drilling assembly for drilling a borehole in a rock body and inserting a rock bolt within the borehole in a single pass, wherein the rock bolt is configured as a combination of both an anchor bolt and a friction bolt, the drilling assembly comprising:
- an elongated drill string having a downhole end;
- a drill bit arranged to be detachably joined to the downhole end of the drill string, the drill bit having an external screw thread extending in an axial direction of the drill string;
- and
- an elongated friction bolt sleeve having an internal axial passage and at least partially surrounding the drill string, wherein the friction bolt sleeve extends substantially along the length of the drill string but is spaced apart from the drill bit during a drilling operation, and wherein the friction bolt sleeve has a thread engaging formation at or near its downhole end arranged to cooperate with the external screw thread of the drill bit.
A method of drilling a borehole in a rock body and inserting a rock bolt within the borehole in a single pass, wherein the rock bolt is configured as a combination of both an anchor bolt and a friction bolt, the method comprising the steps of:
- providing a drill string having a detachable drill bit joined to its downhole end, the drill bit having an external screw thread extending in an axial direction of the drill string;
- providing an elongated friction bolt sleeve having an internal axial passage with a thread engaging formation at or near its downhole end, and locating the friction bolt sleeve around the drill string so that the friction bolt sleeve extends substantially along the length of the drill string but is spaced away from the drill bit during a drilling operation;
- with the drill string rotating in a first direction, drilling the borehole until the friction bolt sleeve has been inserted into the borehole to a desired length so that the friction bolt sleeve is frictionally engaged and held within the rock body;
- while continuing rotation of the drill string in the first direction, withdrawing the drill string from the borehole with the drill bit remaining attached to the drill string so that the drill bit enters into the downhole end of the friction bolt sleeve allowing the external screw thread on the drill bit to engage the thread engaging formation of the friction bolt sleeve, and subsequently screwing the drill bit into the friction bolt sleeve until the drill bit and friction bolt sleeve become wedged against the rock body;
- and
- stopping or reversing the direction of rotation of the drill string to permit the drill bit to be detached from the drill string and subsequently fully retracting the drill string from the friction bolt sleeve.
A drill bit for use in a drilling assembly for drilling a borehole in a rock body and inserting a rock bolt within the borehole in a single pass, the drill bit comprising:
- a drill bit body arranged to be detachably joined to the downhole end of a drill string, the drill bit having an external screw thread extending in an axial direction of the drill string, wherein the external screw thread is configured to cooperate with a thread engaging formation provided at or near a downhole end of a friction bolt sleeve so that the drill bit is able to be screwed into the friction bolt sleeve;
- wherein the drill bit body is substantially frustoconical having a conically tapered side wall, and wherein the external screw thread extends along the length of the tapered side wall.
Dependencies are inferred from the claim text.