Abstract
Abstract. It is well known that some sinkholes or subsidence take place from time to time in the areas where abandoned room and pillar type mines exist. The author has been involved with the stability of abandoned mines beneath urbanized residential areas in Tokai region and there is a great concern about the stability of these abandoned mines during large earthquakes as well as in the long term. The 2003 Miyagi Hokubu and 2011 Great East Japan earthquakes caused great damage to abandoned mines and resulted in many collapses. The author presents the effect of the depth and groundwater on the formation of sinkholes or ground subsidence associated with abandoned room and pillar lignite mines under static and dynamic conditions and discusses the implications on the areas above abandoned lignite mines in this paper.
Highlights
Some caving, collapses and subsidence take place from time to time in the areas where abandoned room and pillar type mines exist
If the area is urbanized, it presents a great concern to the municipalities as well as to the people living in those areas
The 2003 Miyagi Hokubu and the 2011 Great East Japan earthquakes clearly indicated that such areas may experience roof collapses and subsidence as well as the ejection of underground waters from the mines (Aydan and Kawamoto, 2004; Aydan and Tano, 2012)
Summary
Collapses and subsidence take place from time to time in the areas where abandoned room and pillar type mines exist. The backfilling of the abandoned lignite mines of room and pillar type is considered and implemented as a countermeasure against the formation of sinkholes or surface subsidence. It is claimed that if the mines are submerged in groundwater, the degradation of surrounding rock becomes negligible and there is no necessity of backfilling Such a claim may be true under static conditions, the model tests and observations show that the formation of sinkholes or surface ground subsidence may occur in the areas of abandoned room and pillar lignite mines due to earthquakes (Aydan and Kawamoto, 2004; Aydan and Tano, 2012). The author is concerned with the depth and ground water on the formation of sinkholes or ground subsidence in the areas of abandoned lignite mines under static and dynamic conditions in this paper. Some suggestions on the quality of backfilling are presented and discussed
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