The research results provide the technical basis for the reasonable volume of air supply in thick coal seam of simple cutting of top coal dropping and the control techniques of coal spontaneous combustion.

In order to offer theoretical basis for the technology of drawing top-coal with hydraulic props,strata behaviors rule,relationship between support and surrounding rock,and adaptability of drawing top-coal with hydraulic prop in soft thick coal seam were studied by in-situ observation and numerical simulation.

The horizontal section top coal caving in steep seam is different from the gently inclined seam.

The mine adopts a coal demolish feebleization technique beforehand to implement top coal caving.

Based on the physical phenomenon that the amount of the gamma ray radiation in rock is different from the amount of the gamma ray radiation in coal,the paper puts forward the method for coal rock detection in top coal caving.

Based on conditions of Gengcuen coal mining (二 3)coal with sub-level caving mining.

The ground behavior regularity of caving method coal face on “soft seam with soft surounding”and extremely unstable seam and the optimization of support patterns;

The numerical analysis on the stress distribution and the displacement of the top coal in sublevel caving mining;

Research on the possibility of enhancing the upper extraction limit with sublevel caving method under the highly thick hydrous ravelly stratum;