The article unifies Shangwan coal mine 1-2 coal,seam studied the caving characteristic of hard extra-thick coal,which provides certain theory basis to the research of caving character of top coal.

Research on strata behavior law of fully mechanized longwall caving mining face in extra thick seam in Datong Mine Area;

Study on observations on underground pressure of special thick seam at full seam gateway in high stress area;

Through production practice at fully mechanized caving face at first-stage of south 15# coal seam in the bottom of Nanshan Coal Mine,summarizes the gas comprehensive control measures at fully mechanized caving face in the special thick seam.

Fu Gas thick coal seam,the short duration of spontaneous combustion technology Face rapid retracement;

The quenched and tempered thickness of the 2~1/_4Cr-1Mo-~1/_4V steel heavy wall forgings with high technical requirement used for the hydrogenation reactor is 477.