Abstract
Torigatayama Limestone Quarry has been developed with a view to securing abundant long-term supplies of high-grade limestone to meet the growing demand for raw material limestone from Japanese steel mills and cement manufacturers.
Torigatayama Limestone Quarry is on a mountain rising 1, 460 (one thousand four hundred and sixty) meters above the sea level, located in Shikoku, the smallest of the four main islands of Japan. The deposit exists above the 800 (eight hundred)-meter level. It has a length of 2, 300 (two thousand three hundred) meters, a width of 400 (four hundred) to 900 (nine hundred) meters, and a thickness of 300 to 500 meters. With proved reserves of 1, 500, 000, 000 (1 billion 500 million) metric tons, the quarry produces limestone of good quality with a calcium oxide (CaO) content of 55.5 (fifty-five point five) per cent.
Nittetsu Mining Co., Ltd. set about development of Torigatayama Limestone Quarry in 1969, aiming at an eventual annual production of 12 million metric tons. Two years later, or in 1971, production was begun at the rate of 6 million metric tons per annum. Output is being increased steadily in this largest-scale limestone quarrying project in Japan.
A striking feature of this project is found in the generous use of large-capacity modern equipment, notably a belt-conveyor transport system incorporating sophisticated automatic control techniques designed to minimize manpower requirements. In fact Torigatayama, where open-pit/bench-cut mining is adopted, is the first Japanese limestone quarry to employ large-size machines, which enable us to carry on operations at a high efficiency, despite the most unfavorable natural conditions, including the dense fog that persists throughout the year, the heavy rainfalls triggered by typhoons in the summer, and the heavy snow and ice in the winter.
