The preventive measures of roof falling under ground production in coal mine;

Aimming at the roof falling accident in 2209 fully mechanized working face of Chensilou Coal Mine of Yongcheng Coal Industry Group,the authors have chosen the technology of injecting chemical reinforcing grout to strength the roof and ambient coal body.

Processing plan of collapse and roof fall of moving stove tunnel soft burying around rock section;

Analysis of stress arch action and preventing roof falling in laneway engineering;

The paper analyses the factor of coal mine roof fall by AHP and provides reliable theoretical basis for controlling the roof fall.

Destructive reasons and bolting-grouting mechanism are analysed direct to the caving in Renlou Coal Mine.

In this paper,a method of filling and grouting chemical materials into caving zone to solidify roadway was introduced and a good result was achieved.

Analysis on the reasons caused the roof collapse of tunnel and preventive measures

The common foundry methods for nodular iron castings with medium/ small size and their design were introduced including:process characteristics o f nodular iron;types of gating systems ,their choice and design;sorts of feed ers,their principles and choice;feeder design with modulus method.

By properly determining the dimensions of the feeder and its neck according to the principle of pressure-controllable feeder to control the inner pressure of casting,the shrinkageless casting was obtained,and the process yield of the casting was increased.

This article discusses balance compencation in casting,and researches feeding mechanism and process,finds that the point of the method is usage of extra pressure on feeder metal which comes from special pressure machine.