Abstract
The Konan Tunnel, under construction in a densly populated area of Yokohama City, is a twin tunnels designed to carry three lanes and a sidewalk in each direction. Its specfications are a 16.2m width, a separation of 8.7m between the tunnels, a cross-sectional area of 143m2 and an overburden of 5 to 24m.
When excavating a tunnel with a thin overburden, it is important to ensure stability of tunnel itself and to obtain the earliest possible indications of ground subsidence. This paper reports on how total ground subsidence was measured and predicted the behavior of the bedrock ahead of the face.
