Chris C. Langille Ground Control Engineer Inco Limited, Creighton Complex Copper Cliff, Ontario, Canada, P0M 1N0

Dwayne D. Tannant Research Engineer Geomechanics Research Centre Laurentian University Sudbury, Ontario, Canada, P3E 2C6

John Galbraith Rock Mechanics Engineer, Inco Limited Mines Research Copper Cliff, Ontario, Canada, P0M 1N0

Development of underground openings in a deep mining environment requires a support system that is able to absorb energy as a result of dynamic loading due to rockbursting and blasting and static loading due to convergence as the development face advances. The support system must be resistant to corrosion and be effective over the life of the excavation, upwards of ten years, yet simple and cost effective to install. Over the past two years, research has been conducted at Inco's Creighton Mine to try and identify a one-pass grouted support system that will meet these needs.

The main problem faced with simply using grouted rebar 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 that occurs can result in failure of the bolts at the face plates. An initial support is required to enable crews to continue the bolting cycle in the immediate term, yet allow for this convergence over the longer term as the drift advances. 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 headings at +2200m (+7200') through use of direct measurements using both flex rod extensometers grouted into the back of a development heading and 5-point tape extensometer stations. Measured results will be compared with closed form analytical solutions to evaluate the anticipated convergence expected to be absorbed by the bolting system. The required convergence will then be compared with load deformation response of several support configurations.

Several configurations of grouted support systems were pull tested to determine load-displacement characteristics of the typical bolting system and several modified bolting systems. Grout configurations tested included standard two component polyester water based resin and a two component configuration using a fast set resin cartridge at the toe and slow set (10-14 day) cement cartridges to fill the rest of the hole. Two different bolt configurations were tested to allow the bar itself to yield through the grout. This included installation and testing of the South African Cone Bolt grouted with two types of modified polyester resin and testing of a debonded standard rebar bolt.

Ultimately, the results of these trials will lead to recommendations for a system that will enable immediate support to be accomplished with a long term support system, installed on an initial single pass during the development cycle. The advantages to be achieved will be seen in reduced reconditioning and rework and more effective long-term ground support and reinforcement.

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