地下空洞の安定性の評価に関する考察

抄録

According to the experience in mines, the phenomena that occur in underground openings related to the loss of the openings stability, are of the following five types.
Partial-breakdown in openings caused from defects of rock itself, the phenomena that occur in longwall mining stopes in coal mines and cut and fill mining stopes in “Kuroko” mines, where the openings are filled up with falling hangingwall rock, or swelling peripheral rock to balance stresses around the openings, chimney caving, rockburst collapse of the horizontal pillars in open stopes of the large-scale massive ore bodies.
Particulary breakdown from defects of rock and the chimney caving among the above mentioned cases are significant for the stability of openings that are planned for underground utilization.
In the case of breakdown from the defects of rock, large scale breakdowns mainly belong to those which are caused by the weak plane that intersect with the walls of openings at low angles. The width of openings affects its possibility significantly. “Width of openings”, “characteristics of rock” and “depth of opening” are the major factors in the chimney caving. The characteristics of rock considerably vary, depending on their humidity. The stability analyses of openings having been carried out up to the present do not agree with our experience, for they are considerably influenced by shapes of openings and very little by their size. This is so because the analyses are based on the essential earth pressures, while we have mainly experienced breakdowns from defects of rock and chimney cavings that are not phenomena caused mainly by the essential earth pressures.