Lornex Wall Movement - Update
A brief summary of the current slope instability in the Lornex pit. We are currently mining the East wall of the Lornex pit (Phase 3). The Lornex pit is composed of a relatively fractured and soft rock mass and certain slope sectors are susceptible to toppling, which is a mode of geomechanical instability. The NE sector of the Lornex pit has been subject to toppling-induced ground deformation for about 4 benches now. Pit walls subject to toppling can exhibit large-scale deformations as a result of mining; however, the good thing is that this deformations tend to slow down when mining activities cease. THVC uses a complex system of ground monitoring instrumentation allowing us to monitor pit slopes in real time. At about 3AM, Saturday, Jan 20th, the Pit Control operator received a series of alarm messages from the Slope Stability Radar (SSR) and Slope Monitoring Prisms (SMPs), indicating that the rates of deformation exceeded the thresholds established for this zone. In these circumstances, the SOP requests that the Pit Supervisor contacts the Geotechnical Engineer to analyze/confirm the situation. This call was placed at ~3:15AM. After a review of the monitoring data combined with visual observations at the shovel, and given the fact that it was dark the decision was made to evacuate the pit. The evacuation order was given around 3:30AM that same day. All personnel was safely removed from the Lornex pit within about 45min. The oncoming day-shift crew was briefed on the situation at shift change the morning of Saturday Jan 20th. A detailed visual inspection by the pit General Supervisor and the Geotechnical Engineer on duty was performed at the crack of daylight yesterday morning, shortly followed by communications to the Superintendents of Mine Operations and Mine Engineering. A work team was rapidly mobilized by late morning/lunch time. The area was surveyed by drone and laser scanner. The Union Health and Safety Chair was contacted in mid-afternoon Saturday, as well as the Ministry via voice mail and email. Geotechnical monitoring continued during the day. A notice of Geotechnical Incident will be prepared and sent to MEM tomorrow. We will also start working on various designs to allow mining activities to safely resume in the Lornex pit. At this point, it is likely that an off-loading cut in the area of #4 overhaul site will be required. Currently all crews working in the area have being given a presentation as to what is being done to remedy the current situation and the pit remains closed to pit production except for drilling being done outside of the affected area by access of the West ramp. After the ramp had been repaired and as the movement has settled to 40 mm per day production will resume. Phase 2 is to do a cut back in the affected area to remove 5 million tonnes of rock. This option is currently in the design process. We would remind our members to always be vigilant when in all pits, to watch and be aware of their surroundings and report any failures or movement to their supervisors. In Solidarity, DAVE COURT OHSC UNION CHAIR DIRECT PHONE 250-523-3533 HOME 250-320-3179 Comments are closed.
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October 2018
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