ABSTRACT

This paper proposes a most suitable method for evaluating an environmental impact on the ground water surroundings at the Houou Tunnel, which crosses the Median Tectonic Line (hereinafter, referred to as M.T.L.), the largest active fault in Japan. The Houou Tunnel is a highway tunnel and consists of two sub-tunnels, the first one of which was constructed in 1990. At the initial evaluation stage we have come to notice a serious environmental problem with the ground water. The previous construction of the study tunnel appears to have given a significant influence on the surface water system around the tunnel. The ground water level has gone down, thus affecting the local residents near the site. The second tunnel was proposed in parallel to the first one. The focal point of the environmental issues is that in the future, the ground water level might be even lowered and the creek water could decrease in amount or might dry out. The three-dimensional finite element ground water analysis is proposed to predict an environmental impact by tunnel excavation on the behavior of the present surrounding ground water in the study mountain area.