In Sumitomo Akabira Colliery, the limit angle of the shaft pillar has been changed from 60° to 80° since 1985, which resulted in increasing the minable coal volume. A program to protect the shaft has started along with mining of the recently allowed region in the vicinity of the shaft. This is composed of an extensive monitoring of the shaft condition, repairing system of damaged portions and numerical simulation. The adopted numerical method is based on DDM, displacement discontinuity method, and is able to take into account the existence of the ground surface and faults. Simulated displacements along the shaft are in good agreement with the observed displacements in 1989. Loosened concrete blocks of the shaft lining are replaced by new ones utilizing the shaft cage and no obstruction to shaft operations has been experienced until now.


Au charbonnier de Sumitomo Akabira, depuis 1985, la limite d"angle du pilier de la flèche à ete changer de par 60° a 80° qui resulte a grossir du volume de charbon. Le programme de la protection à ete debuter durant le mines de la contree proximite de la flèche. Le travail demande moniteur etendu de la flèche, et repare le système du dommage parts et similation numerique. La methode base sur DDM. Cette methode à la possibilite du considerer l"existence de.la surface de terre et les fautes. Le deplacement simule au long de la flèche a bonne convention avec l"observation du deplacement en 1989. Le beton lache de la fleche à ete replacer avec nouveaux concret par utiliser cage du flèche, et l"operation de l"obstruction, n"eprouve pas jus qu"a maintenant.


Seit 1985 wurde im Sumitomo Akabira Kohlenbergbau der Grenzangel der Schachtssaulen von 60 Grad auf 80 Grad Geandert, mit dem Ergebnis eines höheren Steinkohlevolum. Ein Programm um die Schacht zu schuetzea wurde zusammen mit dem Graben der vor kurzem freigegebenen Region in der Nahe der Schacht eingefuehrt, mit ausfuehrliches Folgen des Schachtzustandes, Reparatursystem von geschadigten Teile und numerische Simulation. Diese numerische Simulation hat DDM (Verschiebungdiskontitnuitat Methode) Grundlage und kann die Boden Oberflache und Fehler in Begriff nehmen. Die simulierte Verschiebungen der Schacht und die beobachtete Verschiebungen sind in guter Einstimmung. Gelockerte Botonstuecke der Schachtlinien werden mit neuen Stuecken in der selben Schacht ersatzt, und keine Fahigkeithemmungen wurden soweit beobachtet.


Most Japanese coal mines suffer problems related with increase of the working depth. If the concept of the limit angle is adopted, the amount of unworkable coal around a shaft increases with the depth. Therefore, change of the limit angle can yield considerable amount of coal around the shaft and will extend the mine life time.

In this point of view, Sumitomo Akabira Colliery in Japan has changed the limit angle from 600 to 800 since 1985. A program to protect the shaft has started along with the minings of the formerly shaft pillar coal. This is composed of an extensive monitoring of the shaft condition, repairing system of the damaged portions and prediction of failures based on a numerical simulation. Observed damages in 1989, results of the numerical simulation for 1989 and the prediction of the damages until 1996 will be described.


Figs.1 and 2 show the mine layout. The rock mass in Tertiary consists of tight shale and sandstone with three workable seams. Mining area is divided by a normal fault called Akabira fault into two areas. In the steep seam area, coal is extracted by the inclined faced overhand stoping with filling.

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