Seismic response and stability of abandoned lignite mines in Japan

The 2003 Miyagi Hokubu and 2011 Great East Japan earthquakes induced severe damage to abandoned mines and resulted in many collapses. There is a growing concern on the seismic response and stability of areas situated above the abandoned lignite mines in Japan due to urbanisation in recent years. The authors had the chance to investigate some damage on abandoned lignite mines caused by the 2003 Miyagi Hokubu and 2011 Great East Japan earthquakes and some local instabilities in abandoned mines in Mitake Town, Gifu Prefecture. This paper describes the characteristics of damage induced on abandoned lignite mines by the 2003 Miyagi Hokubu and 2011 Great East Japan earthquakes. The authors also performed a series of shaking-table experiments on model abandoned mines to understand the response and stability of actual abandoned mines and explain the fundamental mechanism in the formation of sinkholes and subsidence. Furthermore, some discussions are given on the possible causes of the damage inflicted on the ground surface on the basis of some shaking-table model tests in the laboratory.