Friction rock bolt

Patent metadata

Field	Value
Publication number	US-2020063556-A1
Application number	US-201816611646-A
Country	US
Kind code	A1
Filing date	May 9, 2018
Priority date	May 11, 2017
Publication date	Feb 27, 2020
Grant date	—

Abstract

A friction rock bolt assembly is arranged to frictionally engage an internal surface of a bore formed in rock strata. The rock bolt includes an expander mechanism having at least two radially outer wedge elements engageable by an inner wedge element. The expander mechanism is configured for symmetrical displacement of the expander elements to provide controlled enlargement by the rock bolt within the borehole for secure anchorage.

First claim

1 . A friction bolt assembly arranged to frictionally engage an internal surface of a bore formed in rock strata, the assembly comprising:
an elongate tube having a leading end, a trailing end and a longitudinally extending primary slot; an expander mechanism located within the tube towards or at the leading end and configured to apply a radial expansion force to the tube to secure the assembly to the rock strata; and an elongate tendon extending longitudinally within the tube and connected at or towards a first end to the expander mechanism and at or towards a second end to a loading mechanism positioned at or towards the trailing end of the tube that by adjustment is configured to create tension in the tendon to act on the expander mechanism and provide the radial expansion force, the expander mechanism including at least two radially outer wedge elements positionally secured to the tube and a radially inner wedge element secured to the tendon arranged for axial movement relative to the outer wedge elements to apply the radial expansion force to the outer wedge elements wherein the elongate tube further comprising includes at least one secondary slot positioned axially at the expander mechanism, the tube being arranged to deform radially at an axial position of the expander mechanism via the primary slot and the at least one secondary slot in response to axial movement of the inner wedge element and the expansion force transmitted by the outer wedge elements.

2 . The assembly as claimed in claim 1 , wherein the outer wedge elements each have a radially inward facing surface that is oblique relative to a longitudinal axis extending through the assembly and wherein a radially outward facing surface of the inner wedge element extends oblique relative to the longitudinal axis.

3 . The assembly as claimed in claim 2 , wherein the radially inward facing surface of the outer wedge elements and/or the radially outward facing surface of the inner wedge element are generally planar or are at least part conical.

4 . The assembly as claimed in claim 1 , wherein the secondary slot is positioned diametrically opposed to the primary slot.

5 . The assembly as claimed in claim 1 , wherein an axial length of the secondary slot is less than an axial length of the primary slot.

6 . The assembly as claimed in claim 5 , wherein the axial length of the secondary slot is 0.5 to 40% of a total axial length of the elongate tube.

7 . The assembly as claimed in claim 1 , wherein the secondary slot has a width being less than a width of the primary slot.

8 . The assembly as claimed in claim 1 , wherein the outer wedge elements are spaced apart in a circumferential direction by an equal separation distance.

9 . The assembly as claimed in claim 1 , wherein in a circumferential direction, the outer wedge elements are positioned between and do not overlap with the primary and secondary slots.

10 . The assembly as claimed in claim 1 , wherein the outer wedge elements are secured to the tube by a weld.

11 . The assembly as claimed in claim 10 , wherein the outer wedge elements are secured to the tube exclusively at or towards an axially rearward end of each of the wedge elements.

12 . The assembly as claimed in claim 1 , wherein at least a portion of each of the outer wedge elements extends axially beyond the leading end of the tube.

13 . The assembly as claimed in claim 1 , wherein at least a portion of the radially inner wedge element extends axially beyond the leading end of the tube.

14 . The assembly as claimed in claim 12 , wherein a maximum outside diameter of the inner wedge element is greater than an inside diameter of the tube.

15 . The assembly as claimed in claim 12 , wherein a maximum outside diameter of the inner wedge element is approximately equal to an outside diameter of the tube.

16 . The assembly as claimed in claim 1 , wherein the tendon is an elongate bar that is radially enlarged at or towards the first end.

17 . The assembly as claimed in claim 16 , wherein the first end of the bar comprise threads, the threads provided at the radially enlarged first end.

18 . The assembly as claimed in claim 17 , wherein the inner wedge element is mounted on the bar via the threads.

19 . The assembly as claimed in claim 1 , comprising a single primary slot, a single secondary slot and two outer wedge elements positioned diametrically opposite one another and spaced apart in a circumferential direction between the primary and secondary slots.

20 . The assembly as claimed in claim 1 , further comprising a loading mechanism projecting radially outward at the trailing end of the tube and arranged to be braced against the rock strata at a region around an external end of the bore, and a main load element connected with the tendon at the second end to brace against the trailing end of the tube and by adjustment create tension in the tendon to act on the expander mechanism and provide the radial expansion force, wherein the loading mechanism includes a load absorber arranged to absorb load imposed on the loading mechanism by the rock strata and in response to deform or fail to transfer said load to the main load element.

21 . The assembly as claimed in claim 20 , wherein the load absorber includes a compressible collar positioned in contact with the main load element.

22 . The assembly as claimed in claim 21 , wherein the load absorber comprises includes a curved or bent region of a flange, plate or washer, the region extending in a direction axially towards the main load element.

Assignees

• Sandvik Intellectual Property

Inventors

• Darlington Bradley
• Young Peter
• Rataj Mietek

Classifications

• E21D21/0033

  having a jacket or outer tube · CPC title

• E21D21/008

  Anchoring or tensioning means · CPC title

• E21D21/004 Primary

  Bolts held in the borehole by friction all along their length, without additional fixing means · CPC title