Influence of large scale tunnel digging and drainage on groundwater

以松本城山隧道为例，研究了长期排水对地下水系统的影响。1000万m3隧道渗漏水经24年抽排后，3H浓度一直较低，氧同位素值分布均匀。因此，隧道施工前的补给水被认为是排干的。1000万m3隧道渗漏水仅占隧道水平与地表之间沉积物孔隙度的22%。沉积物中孔隙水的完全排干需要80年以上的时间。阐明了在低湿条件下，可利用氧同位素估算蒸发速率。在Namariyama矿区大规模挖掘的周围，发现海藻中含有高浓度的锌。从堵塞的隧道排出的水在海岸涌出，从矿井隧道排出的水是高浓度的金属。

Influence of long term drainage of tunnel seepage on groundwater system was studied at Matumoto-Shiroyama Tunnel. Although 10 million m3 tunnel seepage water has been drained for 24 years, 3H concentration has kept low and oxygen isotope values have been uniform. Therefore, recharged water before the tunnel construction was thought to be drained. The 10 million m3 tunnel seepage water was only 22% of all porosity in sediment between the tunnel level and surface. It needs more 80 years to perfect drain of all pore water in sediment. It has been clarified that evaporation rate can be estimated from oxygen isotope under low humid condition. At the surrounding of large scale digging, Namariyama mine area, high concentration of Zinc for seaweed was found. The drainage water from the plugged tunnel welled up at the coast and the drainage water derived from mine tunnel was high concentration of metal.