Institute of Coal, Federal Research Center of Coal and Coal Chemistry, Siberian Branch, Russian Academy of Sciences, Kemerovo, Russia:

G. Ya. Polevshchikov, Chief Researcher, Professor, Doctor of Engineering Sciences
E. N. Kozyreva, Head of Laboratory, Candidate of Engineering Sciences, kozyrevaen@ic.sbras.ru
M. V. Shinkevich, Senior Researcher, Candidate of Engineering Sciences
E. V. Leontyeva, Leading Engineer

As early as the mid-20th century, scientists of the Kazakh SSR Academy of Sciences when observed displacement of rocks in the course of coal mining in the Karaganda Basin found that formation of overhangs is accompanied with the upheaval of undermined strata above the operating coal bed, in front of the zone of maximum stresses. Later on, Russian scientists proved that the phenomenon of the roof upheaval in front of the longwall face intensified with the increase in the roof rock strength and in the depth of mining. The rock pressure distribution along the longwall face is characterized with the time periods and is wavelike. The Institute of Coal, Siberian Branch of the Russian Academy of Sciences, has been investigating these peculiarities since 2000. The emphasis is laid on the application of the methods of mining aerogasdynamics. The ground for this is the known rule: coal beds only release methane when stresses reduce; i.e. the outward perimeter for a gas-drain area in coal and gas bearing rocks is the front of the mining-induced relaxation from the effective stresses. Accordingly, in order to refine dynamics of the induced geomechanical processes embracing many millions of tons of coal and gas-bearing rocks, it is sufficient to track one of the final results of the process – the change in the methane content in the extraction panel during the production heading advance. This approach creates no troubles when extraction panels are equipped with the electronic monitoring systems. The research into the features of methane content of highly productive panels in mining of gently dipping coal beds with complete roof caving has shown the wavelike behavior of the methane content along the extraction panel with the period up to hundreds of meters (gas-kinetic pattern of gas-bearing rock mass). The wavelike change in the methane content along the extraction panel and the conformable periodicity of change in the pressure in the powered support legs has been proved. The generalization of the research findings enables refining the model of evolution in the induced structuring and gas drainage in rock mass under production face advance.

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