Abstract: The subsurface conditions in Hangzhou area are complicated and might vary significantly. In order to provide reference data for the future tunnel design and operation after the construction, this paper presents the five (5) years longterm monitoring results of the Hangzhou Metro tunnels under operation. The results indicated that, large ground disturbance and large consolidation settlement on the foundation bearing soils could be observed in the mucky clay soils and the communication pass was constructed by using soil freezing method due to the poor permeability and long consolidation period under the foundation loading. The Ushaped trench is a special transition zone between the underground structure and the surface structure. Buoyancy is different at different locations. To avoid large differential settlement after the construction and during the tunnel operation, appropriate ground improvement measures are necessary. The appropriate tunnel embedment depth can avoid the influence of Qiangtang River, which is famous for the “scouring during the flood period and sediment during the tidal period”. Otherwise, a shallow buried tunnel is easily affected by the adjacent environment and large settlement could be induced. When the tunnel structure is within the soft clay zone, the ground improvement within different patterns are necessary and the simple supporting structures are also necessary.

Key words: long-term operation monitoring, communication pass structure, tunnel buried depth, U-shaped trench, adjacent excavation