1958 年 74 巻 843 号 p. 585-640
As in about ten years the new mining machines and technics were imported, the mining method in Japan were changed remarkably.
Natural condition of coal seam in Japan (1956)
Working depth (Average) 334.7m
Average thickness of seam 1.71m
Average thickness of coal 1.31m
Output from coal face 48.281Mill. t.
About 65% of output is worked by longwall method. About 36% of output is gotten by blasting, and 36% by coal picks in coal face, but coal cutters are used pretly well. Hobels are used in Emukae, Takashima, Kogayama and Mitsubishi-Bibai. 55% of output is conveyed Panzer conveyor at coal face.
Hydraulic stowing is carried out at Onoura and pneumatic stowing is used at Yamano, Akabira and Sakito coal mines. Slicing method for thick seam is carried out at Hojo and Takashima coal mines.
We must decrease the number of coal faces in one pit and increase the output per one coal face, and use the practical working time effectively.