武甲山における石灰石の協調採掘と秩父地区残壁研究会

抄録

The Chichibu region located in Saitama Prefecture is a limestone mining area. Mt. Buko limestone deposit is located in the Chichibu region and is being collaboratively mined by Chichibu Taiheiyo Cement, Ryoko Lime Industry, and Buko Mining companies by bench-cut from the top of Mt. Buko. Since the start of mining from the top, Mt. Buko has produced about 260 million tonnes of limestone until the end of March 2017 and a large rock slope (over 400 m high, about 2 km wide, and with overall inclination of 45°) has formed. Currently, managing the stability of the rock slope is considered the most important and critical issue at Mt. Buko. The Task Group for Research on Rock Slope in Chichibu Area (Chichibu Zanken) was established before the start of the cooperative mining at Mt. Buko. The Chichibu Zanken is composed of engineers (especially younger engineers) from the three companies and its first meeting was held in November 1973. In the 45 years since then, the Chichibu Zanken has continued to meet and has held a total of 450 meetings. In the beginning, activities of the Chichibu Zanken were more fundamental, focusing on collecting information on slope stability and studying to design a stable rock slope. Since around 1994, monitoring and analysis of slope behaviors have actively intensified. After the typhoon in September 2007, a significant but short-term slope displacement was detected. From analysis of current and previous data, it was found that the rock slope was affected by heavy rainfall. Therefore, slope drainage, pavement to suppress water permeation, steel pipe piling, retailing rock piling on the rock slope, and their effects on slope stability are important discussion subjects for the Chichibu Zanken. Mining of Mt. Buko is ongoing and making the slope to extend further. The Chichibu Zanken is set to play a key role based on accumulated knowledge and cooperation to solve future unforeseen problems.