Discussion on rational size of district sublevel coal pillars in coal mining face with shallow mining depth;

According to the mining features of the shallow mining depth,longwall and hard over strata in the P1 first coal mining face of Balamb Mine,India,with the analysis on the mine strata pressure features and the analysis on the UDEC numerical simulation calculation,a mine strata pressure control technology with a surface ground blasting method was provided for the P1 coal mining face.

6-2 seam under the shallow mining depth conditions and discussed the suitability of the fully mechanized top coal caving mining and fully mechanized high cutting mining under the above conditions.

Research conclusions:Based on the research on the ground cracks and surrounding rock pressure during the excavation of loess tunnel,the dividing line of deep and shallow submersion,computing method of surrounding rock pressure and designing principle of secondary lining of large sectional loess tunnel on Zhengzhou-Xi\'an Passenger Dedicated Line are presented.

Based on the high mining height of fully-mechanized top-coal caving in shallow thick coal seam and the few falling waste rock in goal, the key roof can not be supported effectively,the facture mechanical model of key roof was established.