Underground Research

Self-organizing of a rock massif around a cavity

The results of recent research into the underground use of backfill have been released by two retired scientists. The long-term research relates to the redistribution of stresses in a rock mass around a cavity, at the Mirgalymsai mines in Kentau, Republic of Kazakhstan. They discovered a natural phenomenon of an isolated subsystem that organizes itself around a cavity, which they call “self-organizing of a rock mass around a cavity,” for which they have applied for a patent. This isolated subsystem contains three zones, each with different rock tensions. The isolated subsystem protects the rock mass and the cavity from further destruction. Using the laws governing this phenomenon has led to the creation of a safe, efficient and ecologically clean technology of mining ore.

The new technology results in no losses of the ore in the subsoil, and the restoration of the rock mass by an expanding, incompressible backfill mass, protected by 15 inventions and one patent. The new backfill is a dense, semi-fluid, slimy thixotropic mix in which all the water is held by dielectric polarized fields. Therefore, during placement of this backfill in chambers it is not necessary to make special accommodations for the drainage of excess water. The backfill mix contains from 35% to 100% 0.43-micron slime mix, and is the first hydro-backfill used in the world.

After special processing of this mix the following results have been achieved. The mix can travel to the chambers by pipelines in the same manner as water. The amount of cement required is much less than conventional systems. The cemented backfill sets in two hours, and reaches normative strength within seven days. The expanding backfill-mass from this mix is a specially developed instrument (so to speak) for the control of rock pressure, which improves the safety of mining in the zones with low rock pressure (tension), up to 3 MPa, regardless of the depth.

Using this technology, 12 million tonnes of ore were extracted over 10 years, 5 million m3 of mined-out cavities were filled and a 1-million-m2 rockmass was reconstructed. The result was a multimillion-dollar economic benefit.

The study has been written by Yevgeniya Kogan and Izrail Kogan. Before retirement, Dr. Izrail Kogan (kogan_israil@mail.ru) was chief mining engineer at the mining company Achpolimetal in Kentau, Kazakhstan. Dr. Yevgeniya Kogan worked as research scientist/faculty at the Mining Institute at Alma-Ata, Kazakhstan.