The prediction of the hazard caused by weighting over great extent of top layer in mine worked-out section area;

Study on the rule caused by roof fall over great extent of worked-out area in mine;

The disaster of stope roof falling over great extent, happening in the coal face during the course of mining, brings about such comprehensive destruction as energy damage, load lash and cyclone damage.

Based on the the fully-mechanized top-coal caving mining of 8~# coal bed in Kangjiatan coal mine,the probability of the gas explosion induced by the impact-friction sparks during roof collapse was studied with the special designed experimental instruments.

The analytical reason of the subsidence is that old working roof collapse strengthen the vertical morenent of underground water between coal-series formation and Quaternary loose formation, the strong drain of coal mining in the area intonsify the erosion and transporting action of underground water, the Quaternary carity forms and the earthquake cause to ha.

For roof collapse control of the belt-conveying-roadway of No.

Roof pressure,structure,water volume,support deformation that are related to the roof caving mechanism are analyzed.

In order to solve the problem of roof caving of orebody in deep broken zone of Kangjiawan mine so as to realize safety mining,we performed the mechanical experiment of rocks,compared and numerically simulated the roof controlling measures,tested the mechanical parameters of rocks,analyzed and classified caving phenomenon.