Abstract: Based on a history case of excavation above the existing tunnel, this study analyzed the effect of nearby dewatering on the existing rivercrossing tunnel by the finite element method. The influence factors such as the declined depth of groundwater, the extracting layer, the dewatering time and the dewatering method are considered. The results show that dewatering above will cause the settlement of the tunnel. The dewatering depth of groundwater and the tunnel settlement present a linear relationship. Pumping from the lowpressure artesian aquifer will lead to larger tunnel settlement. The longer the dewatering lasts, the larger settlement of tunnel will occur. The result also shows that dewatering inside the foundation pit will cause less amount of tunnel settlement than dewatering outside.

Key words: soft ground, tunnel settlement, foundation pit dewatering