Abstract
Underground condition of constructing a tunnel is strongly controlled by geological features such as kinds of rocks, geological structure, etc.An example, Yui tunnel of Shin-Tokaido line, is shown in this paper.In this case, hardness decreases at the position of anticlinal axis of strata. Mudstone, even crushed into breccia, holds its own impermeability.Underground water is reserved mainly in the compound strata of tuff?breccia and conglomerate, partly above a muds tone layer as a form of perched water. Places of water seepage are well related with the undulation and faulting of these aquifer in the tunnel.
