1999 Volume 9 Pages 107-112
A tunnel which has been constructed in “Shirasu”, met with impervious layer at 260 meter from entrance. We observed groundwater level 20 meter higher than spring line in opposite side of the that layer, and we needed more than one month to drawdown. Therefore we conducted a drawdown simulation with finite element method to understand an effective dewatering method.
The results of simulation are as follows:(1) It's effective on drawdown to use longer drainage borings togetherwell point drainage.(2) The specific storage of Shirasu is about 0.03l/m, and it's very important factor in this case.
