This is from Shigeo Yamamoto in Kyushu branch of CKC(Chuo Kaihatsu Corp).
When a mountain was excavated to widen the road, the coal layer which tends to peel off moved the mountain. There are unexpected geotechnical risks in the mountains. When you have a little wondering, talk to Geotechnical Engineer (GE) or Geologist. These geo risks, geotechnical engineering will deal with it!