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Void Fill and Support Techniques to Stabilize Drift Excavated Through a Transition Zone Mined By a TBM at the Stillwater Mine
35th International Conference on Ground Control in Mining
Void Fill and Support Techniques to Stabilize Drift Excavated Through a Transition Zone Mined By a TBM at the Stillwater Mine
by
Josh JohnsonCurt JacobsMark Ferster, Stillwater Mining Company, Nye, United StatesStephen Tadolini, Minova, Georgetown, United States
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[Conference] 35th International Conference on Ground Control in Mining
[Price] Free  [Comments] 0
[Topical Area] Operator Case Histories
[Author] Josh JohnsonCurt JacobsMark Ferster, Stillwater Mining Company, Nye, United StatesStephen Tadolini, Minova, Georgetown, United States
[Abstract] 
Key Conclusions:
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A void fill material allowed to cure 45 days had obtained an average tensile and compressive strength of 133 and 1067 psi, respectively. These physical properties were adequate to accept adjacent loading of the dike and blocky ground. Combinations of fore poling and ring steel completed the “support envelope” that permitted the successful advance of the TBM mining advance.
Key Findings:
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The fallout occurred after the TBM broke through blocky ground with serpentinized joints. Alteration to ground conditions occurred due to the faulting/subsequent dike intrusion with intense pressure and heat which changed the lithology. The physical properties of the void fill material and precise placement with water inflows is critical to creating “false” mining horizons in the roof and adjacent ribs in structurally disturbed granite formations. Additionally, fore poling spacing and lengths - coupled with steel arches and supplemental bolting were extremely important in the program success.
Objective of the Paper:
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Stillwater Mining Company is the only U.S. producer of platinum group metals (PGMs) and the largest producer outside of South Africa and Russia. The Company controls a considerable portion of the J-M Reef and is currently developing the “Blitz Project”, which will provide a main haulage level, ore pass systems, backfill plants, and flow through ventilation to increase production and ensure sustainable extraction of this critical strategic mineral. The Company is currently driving two sub-parallel footwall laterals about 26,000 feet to the east of the existing Stillwater shaft on the 5000 rail level and the 5600 rubber tire level. One of these development entries is being driven with an 18 ft diameter tunnel-boring machine (TBM) and the other sub-parallel heading is being driven using conventional drill and blast methods. The objective of this technical paper is to describe what events occurred when the TBM entered into a geologically disturbed area created by a dike intrusion and how the Engineering and Operations Teams designed, installed and implemented a successful void fill program coupled with fore poling and steel sets to mine through the area and continue the planned advance of the TBM machine.
Problem Statement:
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Mining with a TBM through a transition zone using void fill materials, fore poling and ring steel.