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.

Analysis on roof falling causes of certain mine's stope in Jiaodong area;

On the basis of the investigation,with the rockmass mechanics and numerical simulation, the mechanism of roof falling of stope and mined out area on a large scale are discussed compendiously.

Especially in non-coal mine, the roof fallingaccidents have led to serious consequences.

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