Abstract
On the excavation of such a under ground condition as encountering sand quick phenomenon, well-point method to lower the water-table or deep-well method to reduce the water pressure at heading is ordinally adapted. When the water-table revive after lining, sometimes leakage and piping of water cause a serious problem.
This paper reports the piping phenomenon of Obara tunnel in Tokaido-Shinkansen and the counerplans for leakage and drainage of Higuchiyama tunnel in Sanyo-Shinkansen.
