Study and Practices on Improvement of Mining Up Limit Under Loose Aquifer

In order to release the coal resources,reduce the water proof coal pillars and improve the mining up limit under the loose aqui-fer,Yanzhou Coal Mining Group had the trial mining to improve the mining up limit as well as the systematic observation and study on the water table of the low group in the Quaternary System,the overburden strata crack height and development law individually in the thin seam drilling and blasting mining,thick seam slicing fully mechanized coal mining,full seam fully mechanized top coal caving mining,fully mechanized top coal caving mining under the steel mesh roof and other different mining.The results showed that the water table of the low group in the Quaternary System was steadily decreased and the watery of the low group was steadily weakened.After the coal mining operation completed,the overburden strata would form a regenerated roof with certain water isolated capacity.With the comparison analy-sis on the deep mining and shallow mining,the full thick seam fully mechanized top coal caving mining and repeated multi slice mining,the water conducted cracking height in the overburden rock of the late mining method would be lower than the first mining method.The protective layer thickness of the water prevention and isolation coal and rock pillars for the full thick seam fully mechanized top coal caving mining and fully mechanized top coal caving mining under the steel mesh artificial roof could be 1.5 times of the coal cutting height and could provide the static formula of the water conducted cracking development height under the conditions of the thick seam slicing mining,full seam fully mechanized top coal caving mining and fully mechanized top coal caving mining.