Abstract
During tunnel-excavation in unconsolidated ground, it is necessary to pay attention to erosion or collapse caused by groundwater flow.
So an observation of groundwater has been made around a tunnel in Neogene Pliocenean sandstone.
By investigating the relation between groundwater behavior and factors concerned with the erosion or collapse of the face of an inclined shaft, it was showed that the occurrence of erosion is mainly influenced by groundwater flow, degree of consolidation and grading composition.
The concentration and its variation with time of radio-isotope in groundwater leads an estimation of the subsurface flow pattern when the erosion or collapse is accompanied with the mixing flow of groundwater clustered by those duration time in each porous geological basins.
