北炭夕張新鉱における地圧測定結果および一考察

抄録

With increasing depth of working place, the abnormal phenomena due to rock pressure such as rock burst and gas outburst are becoming liable to occur in our coal mines. Then, today, it is most important to take measures against rock pressure for predicting and preventing such accidents in deeper mines. As one of the measures, the in-situ stress measurements are of great importance.
The Yubari new colliery started its development at the depth of 800-850 m below surface. The assessment of rock pressure of working place, therefore, is especially inevitable for this colliery to undertake a further develnpment of coal in safety.
The authoms carried out in-situ stress measurements in thisc olliebryy thes tresrse liemef thodo f Door stopper, and made estimations about the primary and secondary earth pressure around the galleries of various depth.
The following results cbuld be obtained:
(1) The measurements conducted at the gallery of SL 600, showed that the maximum original principal stress was nearly equal to the calculated overburden pressure and its direction approached the direction of the normal to bedding plane.
(2) The intermediate original principal stress of the point had east-west direction and its value was approximately three-fourths of the overbumden pressure.This dimection coincided with that of the tectonic stress which have played an important role on the fommation of the geological structure in this district.
(3) The distribution of the measured secondary stress around the gallery, was corresponding fairly well to the fracture and elastic zone assessed by RQD measurements of the surrounding rocks.
(4) As to the relationship between depth and stress, it was found that the vertical pressure was almost equal to the overburden while the horizontal stress was a little less than the overburden varying linearly with depth.