Influence of water-rich tunnel by shield tunneling on existing bridge pile foundation in layered soils

At present, shield tunneling often needs to pass through a large number of bridge pile foundations. However, there are few studies on the influence of shield tunneling on adjacent pile foundations by combining with groundwater seepage. Based on Winkler model, the calculation equations of shield tunneling on vertical and horizontal displacement of adjacent bridge pile are derived. Meanwhile, full and part three-dimensional finite element models are established to analyze the trend of bridge pier settlement, ground surface settlement trough, vertical and horizontal displacement of the pile and pile stress under three calculation conditions, i.e., not considering groundwater effect, considering stable groundwater effect and fluid-soil interaction. The results show that the calculated value is small when the effect of groundwater is not considered; the seepage velocity of the soil above the excavation face is faster than that of the surrounding soil under fluid-soil interaction, and after the shield passing, the groundwater on both sides shows a flow trend of “U” shape on the ground surface supplying to the upper part of the tunnel; the vertical displacement of the pile body is bounded by the horizontal position of the top of the tunnel, the upper pile body settles, and the lower pile body deforms upward. The horizontal displacement of pile body presents a continuous “S” shape distribution, causing stress concentration near the tunnel. The calculated results of fluid-soil interaction are in good agreement with the field measured data and accord with the actual situation.