For medium-thick and moderately stable ore- body,being laid preliminary projects in ore block footwall,with medium-longth hole blast,ideal effect was ob- tained in the recovery,reference value was also provided for moderately stable pil.

According to the virtual connection phenomenon caused by easy escape of plug-in protection electronics in the box under coal mine, which makes switch fail to work, this paper analyzes theoretically the position of plug-in electronics and provides methods to increase the stability of plug-in electronics and reliable measures to ensure the working of switch.

The effect on track of the deployed number of concrete sleepers within per kilometer are calculated and analyzed in detail based on the track strength theories(including static and dynamic) and the track stability theory, thus to find the theoretical base for the decrease of the deployed number of type Ⅲ concrete sleepers per kilometer.