The flooding of the Mir mine, Alrosa, occurred on 4 August. The water suddenly poured into the workings. At that moment, 151 workers were underground. 142 people managed to evacuate at once, one got under the flood, stayed under the ground for 30 hours and managed to get out himself to a safe place. Eight people were missing. Their search went for three weeks, but on August 26, the search and rescue operation at the Mir mine was discontinued. In the pit of the pit 37 400 cu. m of water, the company explained: "The threat of a momentary uncontrolled withdrawal of such a quantity of water into the mine makes it impossible to conduct any underground work."
On the day of the accident, on August 4, Alrosa reported that there was an uncontrolled breakthrough of water into the mine from a pit located above it due to a sharp deterioration in mining and geological conditions. But the final causes of the accident are not known. An investigation is being carried out by a special commission of Rostechnadzor.
How long the mine will remain, whether it will be possible to restore it and how much it will cost is not known. "A comprehensive analysis is required from specialists, engineers, designers," the representative of Alrosa said. "The work is on, and we hope that in this and the next years the impact of the suspension of the Mir mine on the company's main production indicators will be limited."
"Judging from the information that is available to the public, the damage to the mine is significant and its recovery will not be rapid," Aton analyst Atom Lobazov wrote in his report. While it is impossible to answer the question, when and which part of the mine will be restored, says a person close to the company. "Part of the mine is flooded, and it's necessary to change the mining project for work," he added. In other words, the company will have to rewrite the diamond pipe development plan.
The mine is not subject to recovery, the former employee of Alrosa believes.
The diamond pipe Mir was opened in 1955. The open production was completed in 2001. The remaining ore body, which is located under the quarry, has been mined since 2009 in an underground way. The estimated production time is 2043. Last year, the mine reached its designed capacity.
"The possible cause of the accident at the Mir mine could be the wrongly chosen technology of development," says Nina Kaledina, professor of the Department of Safety and Ecology of Mining, NITU MISiS. The fact is that the mine into the mine was laid from the pit of the pit, at the bottom of which water was accumulated. Accordingly, mining of diamond ore was conducted from the top down, which is faster and cheaper, Kaledin points out. It's safer, but it would be more expensive to work from the bottom up, she adds. In this case, the mine for access to the mine should be drilled not from the pit of the quarry, but to the side of it. In this case, the miners would always remain under the cover of the overlying rock mass, and the upper part of the tube that would have to go into the quarry would have to be worked out in the last resort, with additional security measures, the expert explains.
During the accident, obviously, the drainage system and the pumps installed in the mine failed to raise the water level, Kaledin continues. For safe conditions, an additional vertical shaft should be drilled on the opposite side of the field from the main industrial site.
It would serve as an additional exit for miners in case of possible accidents and collapse of the main opening workings, and would also allow the mine rescuers to reach the center of the accident faster, Kaledin adds.
The former head of the alternative trade union Alrosa, Profsvoboda, and now the director of the public organization Center for the Protection of Trade Union Rights, Valentin Urusov, notes that there have been floods in the mine before. The main cause of the accident is the absence of a concreted bottom of the lake in the quarry, which could keep the water mass from getting into the mine, said mining engineer Pavel Shelkov. A fatal outcome could be the reduction in the thickness of the whole (the space between the bottom of the quarry and the point of the beginning of underground mining).
The representative of "Alrosa" said that the project of the mine, which was Glavgosekspertizu and repeated examination of industrial safety, concreting was not envisaged. He also points out that, according to design calculations, a 20 m high target is safe to work. Nevertheless, the company increased it to 40 m, he added. In addition, a three-layered array with a total thickness of 45 m was created at the bottom of the quarry: a lower drainage layer, a layer of a waterproof film, and a layer of clay-containing rock.