Rockbolt assembly

Details Rockbolt assembly Rockbolt assembly

2001-04-12

2002-11-05

Shackelford, Heather (Department: 3673)

Hydraulic and earth engineering

Earth treatment or control

Rock or earth bolt or anchor

C405S259100, C405S259500, C405S302100, C411S383000, C411S395000, C411S082000

Reexamination Certificate

active

06474910

ABSTRACT:

BACKGROUND
The present invention relates to rockbolts and more particularly to an assembly for securing a rockbolt within a borehole.
Rockbolts are long bolts, typically between 8 to 12 feet, used to support surfaces, for example, the roof of an underground excavation. The inner end is secured in a borehole in the surface and the outer end engages a faceplate which engages the surface. There are generally two types of rockbolts: untensioned rockbolts which engage the borehole along substantially the length of the bolt supporting the surface by engaging the overlying rock, and tensioned rockbolts which engage the rock at the inner end and at the outer end compress the surrounding rock. In the grid-like pattern in which the bolts are used, tensioned rockbolts create ribs of compressed rock across the surface which act like beams.
Referring to
FIG. 1
, a prior art tensioned rockbolt assembly
10
is illustrated. The assembly
10
includes a faceplate
12
positioned about the borehole
14
and a rockbolt
16
extending through the plate
12
into the borehole
14
. The inner end of the rockbolt
16
engages and actuates an anchor
18
positioned in the borehole
14
. While the anchor
18
is illustrated as an expansion nut and bail, other anchors can be utilized, for example, expanded wedges or curable resins. To tension the rockbolt
10
, a nut
20
on the outer end of the rockbolt
16
is tightened against a grout bulb
22
configured to seat against the faceplate
12
. A good description of prior rockbolts and anchors can be found in Underground Excavations in Rock by E. Hoek and E. T. Brown.
When rockbolts
10
are permanently installed, it is generally desirable to backfill the borehole
14
with grout after the rockbolt
16
is tensioned to protect the rockbolt
16
and anchor
18
from corrosion. To facilitate such, many prior art rockbolts
10
include a tube
24
extending from the grout bulb
22
toward the inner end of the rockbolt
16
. A side opening
26
is provided in the grout bulb
22
for injection of pressurized grout (not shown). A grout sealer
30
is provided adjacent the juncture between the grout bulb
22
and nut
20
to reduce the potential for leaking at the juncture and to ensure the grout flows through the tube
24
toward the inner end of the borehole
14
. After filling the inner end, the grout flows back along the outside of the tube
24
to fill the remainder of the borehole
14
. A check port
28
is often provided in the faceplate
12
to ensure complete fill of the borehole
14
.
SUMMARY
The present invention provides an improved rockbolt assembly. The assembly generally comprises a rockbolt, an anchor, a hollow tube assembly, a faceplate and a nut. The rockbolt has a threaded free end and a second end associated with the anchor. The hollow tube assembly has open first and second ends and an internally extending threaded portion, configured to engage the rockbolt free end, which is positioned between the ends. A passage, including at least one channel traversing the threaded portion, extends between the ends of the tube assembly. The tube assembly allows installation of a standard rockbolt and also the direct injection of back-fill grout through an easily accessible open tube which does not require internal sealers. The faceplate has an aperture therethrough adapted to be positioned about the borehole and to receive the tube assembly. The nut directly engages the faceplate and the tube assembly such that tightening of the nut about the tube assembly is translated through the rockbolt to cause engagement of the anchor.


REFERENCES:
patent: 3302410 (1967-02-01), McLean
patent: 4636115 (1987-01-01), Davis et al.
patent: 4655644 (1987-04-01), Lane et al.
patent: 4984937 (1991-01-01), Karpellus
patent: 5556233 (1996-09-01), Kovago
patent: 5636945 (1997-06-01), Oddbjorn Nes
patent: 5827014 (1998-10-01), Swemmer
Williams Form Engineering Corp. web page entitled “Rock Anchor Systems”, 6 printed pages, located at http://www.williamform.com/spinlock,html, Apr. 4, 2001.

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