Land subsidence resulted from 500m spring draining in granite complex in Mizunami, central Japan (2004-2012)
Abstract
The 1,000m shaft excavation project in granite complex by Japan Atomic Energy Agency (JAEA) is on going in Mizunami, Gifu prefecture, Central Japan since April 2004. The excavating is reached the 500 m depth in March 2010 and the groundwater are inflowing around 700 ton/day. It is suggested the land subsidence as a result of ground water level changing by spring drain at the shaft. We make observations of ground water, crustal deformation by tilt meter, stress meter, strain meter and precise leveling, and gravity around the shaft. The subsidence was started at the time of the excavation beginning. As the observation results, drawdown of water head amounting to 70 m was detected in the observation wells, and 1-2 cm subsidence are detected at the benchmarks locating close to the shaft excavation site and on its south side area in the period of February 2004 to October 2012. The groundwater was almost recovered to the level of before the shaft excavation when drainage was temporarily stopped in June 2005, but it decreased by resume of drainage again. It shows a good association between the subsidence and water level change. It is suggested ground consolidation and elastic deformation as a mechanism of the subsidence. However, benchmarks are limited to the excavation site, and we could not make clear spatial distribution of the subsidence.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.G43A0952K
- Keywords:
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- 1211 GEODESY AND GRAVITY Non-tectonic deformation;
- 1207 GEODESY AND GRAVITY Transient deformation