History of Technical Improvement and Underground Conditions at Deep Mining

Abstract

Working Level of Horonai Coal Mine which is the most deepest mine in Japan has reached up to the depth of S.L (Sea Level)-1, 210 m, i.e. to the 10th Level.
The distance between the Levels isvertically 70 m and our present rate of deepening in a year is 20m. As a coal mining method, we have been adopting mechanized mining since 1969 using Self Advancing Powered Roof Support with Double Ranging Drum Shearer.
Horonai Coal Mine has been tormented with two large problems.
1. One of the high temperature environment in underground.
2. Other is the inclination increase of mechanized working face.
According to the deepening ofmining area, the working environment is getting worse year by year owing to the high temperature and inclination increase.
Since 1983 we have been studying positively to solve these problems and have tried various countermeasures.
1. Central Cooling System which is the first installation of its kind in Japan, adding to the operation of former type partical cooling system. We could have succeeded to obtain almost sufficient environmental condition.
2. We have been adopting mechanaized mining techniques for the coal seams inclination, which was limited to about 25 degrees. As a result of reinforcement and improvement, it hasbecome possible to mine under the steep seams inclination of 43 degrees inclination. It was solved by the mechanized mining techniques for the steep coal seams of about 40 degrees inclination.