Structural Torsion Caused by Large Diameter Shield Obliquely Crossing Rectangular Ramp and Its Measured Analysis
The ramp structure is sensitive to the uneven deformation in longitudinal and transverse direction due to its large and special cross-section.The camp structure with super large slurry shield under-crossing inevitably suffers from the remarkable vertical and torsional deformation,which is harmful to the structural safety.The paper,taking the Beiheng passage excavated by large slurry shield undercrossing Yangshupu portal ramp in Shanghai as example,investigates the deformation behaviors of new-built rectangular ramp induced by super large slurry shield under-crossing with small oblique angle in long distance.Besides,the deformation performance of camp induced by the two unexpected shield halt is considered.The result show that the vertical deformation of ramp is obviously affected by the position of shield incision,shield tail location,shut-down and re-advance of shield.The tail grouting and the shield re-advance lead to significant uplift of tunnel,and the uplift value can reach 4mm.The torsional deformation of ramp is closely related to the shield-ramp mutual position,and the longitudinal distribution of torsional deformation changes from anticlockwise to clockwise.Besides,the final settlement of the ramp is determined by the shield-ramp mutual position and the corresponding crossing stage.
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