New Zealand company Solid Energy has announced it has begun work to fill the ventilation shaft at the former Pike River Mine. The company said mine team and contractors have successfully placed a high-strength expanding resin into the shaft and have begun to top this resin with a layer of concrete. Once the concrete has set, the remaining area will be filled with an expanding foam material that will also be topped off with a final layer of concrete.
The re-entry project at the former Pike River mine began in October with personnel and a helicopter from the New Zealand Defence Force onsite to lift material from the top of the mine ventilation shaft.
On November 19 2010, an explosion at the mine in Greymouth New Zealand, killed 29 miners. An investigation into the mine explosion by the Royal Commission in 2012 concluded that the deaths could have been prevented, blaming poor safety standards for the disaster.
In September this year, the New Zealand Government approved conditional funding of a staged plan to re-enter and explore the tunnel up to a rock fall approximately 2.3 km from the mine entrance.
Members of the Solid Energy crew prepared for and received the first helicopter-lifted load of concrete at around 2.45 pm local time on 14 November.
Director of the project, Mark Pizey, said he was hopeful that this first phase of the project will be completed by Christmas.
The re-entry project has been planned for three separate stages, sub-phases occurring in each of these. There will be on-going safety and technical assessment at each stage. The planned re-entry project will take place in the following steps:
- Plug the ventilation shaft using material carried in by helicopter.
- Drill new boreholes into the top end of the main tunnel.
- Check underground area with camera, where another plug will be placed.
- Place expanding foam (ROCSIL) into the tunnel via a borehole from the surface. This will form a plug at approximately 2.3 km into the mine, and about 40 m on the portal (eastern) side of the rock fall that prevents entry into the main mine workings.
- Pump inert nitrogen gas into the tunnel area between the ROCSIL plug and the rock fall, which will displace methane.
- Ventilate main tunnel from the portal up to ROCSIL plug.
- Once the tunnel is safe and fully ventilated with clear air, trained mines rescue personnel will enter the tunnel.
The main work at the project is being carried out by Solid Energy, which bought the assets of the former Pike River Coal business in July 2012.
The conceptual project plans for the tunnel re-entry were developed by a group of mining experts, including independent mining consultants, Solid Energy staff, and the New Zealand Mines Rescue Service, with oversight from the Ministry of Business, Innovation and Employment’s High Hazards Unit.
Solid Energy chairman, Mark Ford, said: “While Solid Energy is managing the project, it is very much a collaborative effort, with funding from the government and the expertise of many individuals and organisations who have come together to plan it and carry it out safely.”
Adapted from press release by Sam Dodson