摘要
For circumstances of medium-embedding depth and medium-hard surroundings in Jining No.2 Colliery, Yanzhou Group, by using software RFPA2D to simulate the process of overburden fracture, studied the overburden separation which was caused by working face exploitation, its fracture characteristics and the isolated island coalface（IIC） formation systematically in comparison method. After the recovery of the IIC, the surrounding separation areas which lied above the working face and bilateral goaved respectively form a connected region, a region that is like a saddle with low middle （35 times） and high sides. The top boundary line of the separation area is an arc. Then the fracture rise rapidly to 28 times of working thickness; while it is smaller （only 8-17 times recovery height） when extracting bilaterally, though the fracture plane both are in shape of an unsymmetrical trapezium. As the recovery of IIC makes side recoveries change from insufficiency to sufficiency, the consequentially rapid change of characteristics of overburden separation and fracture would enhance the representation degree of mining pressure of IIC.
