The features of the subsidence and horizontal displacement caused by mining coal seams are studied by examining the results of measurement of them carried out in many Japanese coal mines which have not been made open to the public. It is found that the distributions of subsidence and so on forecast by pre calculation using the method developed in Germany do not exactly coincide with the measured ones, especially in case of inclined seams. Subsequently the mechanism of subsidence is investigated by means of mathematical simulation in consideration of those features, and the method of pre calculation above mentioned is so modified that it affords good results when it is applied to the case of inclined seams.


En utilisant les resultats inedits des mesurages executes dans les nombreuses mines de houille au Japon, I'auteur etudie les caracteristiques de l'affaissement du sol et celles du deplacement horizontal causes par l'extraction des couches de charbon. En examinant ces donnees, l'auteur trouve que la r partition des affaissements du sol prevue par le calcul utilisant la methode mise en valeur en Allemagne ne correspond pas exactement a la realite, surtout quand il s'agit des couches inclinees, L'auteur tient compte de ces caracteristiques pour etudier en suite le mecanisme de l'affaissement du sol; pour conclure il corrige la methode de calcul mentionnee ci-dessus de telle facon qu'elle donne de bons resultats quand il s'agit d'une couche inclinee egalement.


Die Eigenschaft der Bodensenkung und der horizontalen Verschiebung, die der Abbau des geneigten Kohlenflözes verursacht, wird dadurch erforscht, dass man die Messergebnisse von ihnen prueft, die durch Vermessungen in vielen japanischen Kohlenbergwerken gewonnen waren und die nicht veröffentlicht waren. Es ist sich herausgestellt, dass die mit demin Deutschland entwickelten Verfahren vorberechnete Bodensenkungsverteilung mit den aktuellen Messergebnissen nicht genau çbereinstimmt, besonders beim geneigten Kohlenflöz. Dann wird die Zusammenhang der Bodensenkung mittels mathematischen Vorschuetzung in Beruecksichtigung ihrer Eigenschaft untersucht, und das oben genannte Verfahren der Vorberechnung wird so abgeandert, dass es gute Ergebnisse gewahrt, wen es fuer das geneigte Kohlenbergwerk angewendet wird.


The coal measures in Japan consist of sandstones, shales, conglomerates and coals of Palaeogene period, and are younger than those in many foreign countries. Most coal seams incline at angles less than 30 degrees. In almost all coal mines, coal seams have been mined by the longwall method. In the northern district of Kyushu, subsidence damages caused by mining coal seams had been a problem since several decades ago. After the world War II, they pre calculated the surface subsidence in many coal mines by the method developed in Germany for the purpose of investigating some possible way to minimize damages. This method of precalculation assumes that the subsidence at an optional point on the surface can be estimated by continually multiplying the thickness of extraction by the three factors, the subsidence factor, the influence factor and the time factor. The influence factor depends upon the mined area and its relative position to the point considered on the surface. The influence factor at a point on the surface will necessarily be unity if the critical area with respect to the point is completely worked. Let us call this method of precalculation the influence factor method in the present paper. Though subsidence had been precalculated for years in Japanese Coal mines, it has not been clarified to what extent the calculated Subsidence is near the actual subsidence, because no correlation between the calculated and measured values of subsidence has been made. Nowadays all coal mines in Kyushu except three undersea coal mines have closed, and of late the authors obtained fortunately the results of subsidence measurement carried out in many coal mines through the courtesy of several mining companies and the Mine Safety Bureau. On the basis of these subsidence data, they have carried out investigations into the phenomena of subsidence to clarify their features and mechanism and to find a convenient method of precalculation for them.

2.1 Method of measurement

In many coal mines in Kyushu, surface subsidence was measured continuously by the technique of survey, subsidized by the Ministry of International Trade and Industry. In a few mines, horizontal displacement was also measured. The stations for survey were set at intervals of from 20 to 30m over sufficiently wide ranges along two lines, AA' and BB', on the surface of each mining area. If the surface condition allowed, these lines were laid through the center of the mining area, the one running in the direction of strike, and the other in the direction of dip. The stations were constructed rigidly so as never to be destroyed. The survey was generally carried out every month from a little time before the start of mining to the stage when subsidence has almost finished.

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