Tunneling in saturated soft rocks may induce serious environment problems. During the excavation of Beigang Tunnel

a railway tunnel in soft rock mass rich in water

a large volume of water and soil flowed into the tunnel and induced severe damage at several sites. At these sites

water table fell down

ground surface cracks occurred. Taking Beigang Tunnel as the prototype

model tests are conducted to study the pattern and law of ground subsidence and cracks when tunneling in soft rock with high water content. It was found that: (1) The transverse settlements curve of ground before collapse can be well described by the normal probability curve proposed by peck. (2) Water and soil flow is the main reason for severe damage in Beigang Tunnel. (3) Collapse happens firstly at the top of the tunnel and then develops upwards to form an arch shaped failure structure. (4) Main influenced area on surface by tunneling is limited in the region between the two largest cracks

which come into being in the early stage of collapse and located on the each side of the tunnel axis respectively.