The feasibility of increasing open pit′s service life by deeping the final mining elevation, treating lean copper ore in the piles, recovering stope side ore is discussed.

This paper,in view of the fact that over-exploitation of groundwa- ter has been the main factor affecting the land subsidence in Tianjin and based on analyses of the monitor- ing data of land subsidence and groundwater exploitation,attempts to determine the quota of groundwater exploitation for the various townships in Tianjin in 2007,either maintaining the level in 2005 or setting .

The balance structure of main roof and its action to immediate roof in large cutting height workface;

This paper introduces the state of the art and the development of thick seam mining techniques in details and the prominent achievements in top-coal caving and large cutting height workface in China.

In the whole simulating production experiment under formation conditions, the data of the whole tight sandstone cores indicate that high speed production can cause permeability damage.