鋼枠コンクリート支保のひずみと内力の採掘に伴う変化について

鋼枠コンクリート支保の支保機構に関する研究 (第3報)

抄録

A series of investigation on concrete support combined with outer and inner steel sets, which was developed at Matsumine mine, a mining section of Hanaoka mine, Dowa Mining Co., to maintain the haulage drift in the heavy pressure zone, are being carried out in order to clarify the mechanism of the support. In this paper described was the influence of mining excavations of black ore deposits at the upper levels on the strains and internal forces in the support at the lower haulage level as a result of long-term in-situ measurement for more than three years.
Before the beginning of mining excavations, hydrostatic secondary rock pressure which was caused by the reaction of the rigid support against the deformation of surrounding soft rock mass was found to increase approximately at the rate of 0.07-0.08 kg/cm²/day or about 27 kg/cm² /year. Therefore, it is very important to plan the mining excavations so that it may be completed before the support of the haulage drift fails due to this hydrostatic secondary rock pressure.
Once mining excavations of so-called “60m” section began at the upper levels of the haulage drift, considerable unloading of rock pressure around the drift occurred because the mining section is located in the direction of principal rock pressure, and, at the same ti me, the direction of rock pressure around the drift was rotated towards the un-mined area. However, as mining of so-called “No.47” section located at the upper levels ahead of the measured point progressed, internal forces in the supportb egan to increase again because of the stress concentration caused by the mining excavations, and it continued until the mining of lower level of “60m” section began. Rock pressure around the haulage drift was definitely unloaded finally by the mining excavations right above the measured point of the drift.
Thus, in-situ measurement on the strains and internal forces in the concrete support combined with outer and inner steel sets were successfully fulfilled until the role of the lower haulage drift was almost accomplished.