Abstract:

The effect of groundwater seepage on ground surface settlement of shallowcovered mined section of Zizhi Tunnel in Hangzhou in waterrich and softweak strata and the ground surface settlement characteristics are analyzed by site monitoring data analysis and numerical simulation calculation method. The analytical results show that: 1) Under the action of groundwater seepage, the fitting results of the transverse and longitudinal ground surface settlements are larger than the suggested values in existing researches. 2) The region where pore pressure drops gradually amplifies during tunnel construction; and the groundwater seepage is the main cause for the increase of settlement trough width. 3) The ground surface settlement mainly occurs in the region between two inclined lines, which are located at the springline and have an inclined angle of 45°+φ/2 to the horizontal direction,where φ is the average friction angle of the overlying ground.

Key words: Zizhi Tunnel, shallowcovered mined tunnel, ground surface settlement, settlement trough, solidfluid coupling analysis