For the purpose to raise the coal seam mining upper limit, carried out a study of 11-2 coal seam protecting pillar thickness, lithologic association characteristics and water-bearing capacity.

On this basis,the 17116 first-thick seam extraction is successful mined with retaining 37 m waterproof pillar under increasing ceiling.

The main target coal seam of Xieqiao Mine is directly covered with the Quaternary bottom gravels, whose impermeability affects the reasonable retainment of waterproof pillar.

In order to find the possibility and safety of coal exploitation under water with reduced waterproof pillar at upper limit,the vertical boreholes were drilled from the surface to detect overlaying rock failure.

UDEC simulation of the water-pouring probability in exploiting waterproof coal pillars under the conditions of thick loose bed and ultrathin overlying strata;

13-1 sublayer coal of the reducing waterproof coal pillars in No.

The author studies mainly on the characteristics of engineering geology about the zone of weathering overlying coal seam,the mechanism of cutting waterproof coal pillar and provides the reference for the coal mine with similar condition in cutting waterproof coal pillar.

Numerical simulation of influence of water barrier pillars for subsided column on rock failure in mining process;

Static simulations at different time of working face with water barrier pillars are carried out with FLAC3D , pseudo-dynamic simulation for excavation process of moving forwards are made up of static simulations being arranged according to rank of moving forwards in time field.