Cc. Langille et al., INVESTIGATION OF ONE-PASS GROUTED SUPPORT SYSTEMS FOR USE IN A HIGH-STRESS MINING ENVIRONMENT, CIM bulletin, 89(1001), 1996, pp. 111-116
Citations number
9
Categorie Soggetti
Metallurgy & Metallurigical Engineering","Mining & Mineral Processing
Development of underground openings in a deep mining environment requi
res a support system that is able to absorb energy as a result of dyna
mic loading due to rockbursting and blasting and static loading due to
convergence as she development face advances. The support system must
be resistant to corrosion and be effective over the life of the excav
ation, upward of ten years, yet simple and cost effective to install O
ver the past two years, research has been conducted at INCO's Creighto
n Mine to try and identify a one-pass grouted support system that will
meet these needs. The main problem faced with simply using grouted re
bar at depth, is the effect of tunnel convergence on the stiff grouted
bolts. Typically, if fully grouted, stiff rebar are installed to the
face of an advancing development heading, the amount of convergence th
at occurs can result in failure of the bolts at the face plates used t
o attach the mine screen to the back. An initial support is required t
o enable crews to continue the bolting cycle in the immediate term, ye
t allow for this convergence over the longer term as the drift advance
s. The ideal support system will allow both to occur, giving effective
immediate support while providing long-term effectiveness in allowing
convergence to occur while maintaining the capacity of the bolt. This
paper will investigate the expected convergence in deep development h
eadings at +2200 m (+7200 ft) through the use of direct measurements u
sing both flex rod extensometers grouted into the back of a developmen
t heading and five-point tape extensometer stations. Measured results
will be compared with simple 2-D numerical analysis so evaluate the an
ticipated convergence expected to be absorbed by the belling system. T
he required convergence will then be compared with load deformation re
sponse of several support configurations. Several configurations of gr
outed support systems were pull tested to determine load-displacement
characteristics of the typical bolting system and several modified bel
ling systems. Grout configurations tested included standard two-compon
ent polyester waser-based resin and a two-component configuration usin
g a fast set resin cartridge at the toe and slow set (10 to 14 days) c
ement cartridges to fill the rest of the hole. The maximum deformation
achieved with the standard rebar was less than 20 mm at a peak load o
f 170 kN to 180 kN. With the cement-resin rebar, the maximum displacem
ent achieved was 36 mm, with a peak load of 170 kN to 180 kN. Failure
occurred at the threads in both cases. A third system was tested. One
that would allow the bar itself to yield through the grout, using the
South African Cone Bolt grouted with two types of modified polyester r
esin. Peak loads of 170 kN were achieved with between 89 mm and 141 mm
of displacement. Mixing of the resin with the smooth bar was inconsis
tent and requires further investigation. Ultimately the results of the
se trials will lead to recommendations for a system that will enable i
mmediate support to be accomplished with a long-term support system, i
nstalled on an initial single pass during the development cycle. The a
dvantages to be achieved will be seen in reduced reconditioning and re
work and more effective long-term ground support and reinforcement.