PIV EXPERIMENTAL STUDY ON STEADY-STATE SEEPAGE IN SATURATED STRATA DURING SHIELD TUNNELING EXCAVATION
This study investigates the instability of the excavation face and ground surface settlement in saturated soil layers under steady-state seepage conditions,using shield tunneling as the research background.Centrifugal model tests were conducted to explore the effects of different water head heights on the stability of the excavation face.Based on dimensional analysis and mechanical similarity theory,various saturated soil samples were prepared for the tests to simulate excavation-induced failure.The results indicate that the range of soil deformation and insta-bility increases with the water depth ratio(H/D).At the limit state of excavation,the primary settlement impact area is a 2D region centered 0.5D in front of the excavation face.The maximum ground settlement increases significantly with the water depth ratio,changing from a'W'shape to a'V'shape.During failure,the main settlement impact ar-ea is a 2D region centered 0.4D in front of the excavation face.Once the water head exceeds 2D,the maximum ground settlement stabilizes and does not increase significantly with the water depth ratio,transitioning from asym-metric to symmetric settlement,with the shape predominantly'V'.This research provides valuable insights for engi-neering risk monitoring in shield tunneling through saturated strata.
steady state seepagesaturated soil layersurface subsidence
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