Status and research progress for residual coal mining in China

The drop of the coal reserve-to-production (R / P) ratio leads to a challenge on sustainable coal mining in China. Due to the historical reasons,a large number of high quality coal resources which have not been effectively mined in shallow areas form residual coal. Reserves calculation and mines statistics of residual coal were conducted. A discussion concerning the distribution characteristics of residual coal reserves,R / P ratio,types and mining,research status and key technological problems to be solved was presented. Research shows that the recoverable reserves of re- sidual coal may reach 40 billion tons and the recoverable reserve of initial recovery rate below 20% is about 27. 16 billion tons,accounting for 67. 4% of the total recoverable reserves. Increment rate of residual coal R / P ratio in the east which is average of 95. 9% is more than the west which is average of 51% . Residual coal mines distributing in 15 provinces and their recoverable reserves are 34. 71 billion tons,accounting for 86% of all the residual coal recoverable reserves. Residual coal mining operations showed different trends around 2006. Before 2006,88. 5% of the residual coal mines were concentrated in the eastern coal-producing provinces,after which began to appear in the central and western coal-producing provinces. In terms of the region,the east residual coal mines account for 65. 82% of the total, while Shanxi Province accounts for 24. 1% . It shows that residual coal mining operation is concentrated in the eastern provinces and Shanxi Province. The residual coal could be divided into the block-section,full-seam,slicing and com- pound type,in which the block-section is the most widely distributed type. The dominant type is different between the east and the west. The dominant types are edge coal and protective coal pillar in the east,while is damage areas of small coalmine in the middle and west China. Residual coal mining research in the residual coal detection technology, the residual coal mining theory and technology and disaster prevention and control technology of residual coal mining aspects have made some progresses. Because residual coal mining is a complicated system engineering,therefore,some further studies in terms of hazardous sources detection of residual coal mining,mining methods,pressure display law and rock strata control method of residual coal,law and treatment of water and gas occurrence and migration in goaf, and new materials for the disaster prevention and control of residual coal mining are still needed.