Effect of a Shallowly Buried Super-large-diameter Shield Tunnel Closely Crossing Existing Pile Foundations of a Viaduct
Section Ⅷ of Shanghai Beiheng Passageway is a super large shield tunnel with a diameter of 15.5 m,which closely side-crossed the inner circle viaduct after escaping from the shaft for only 54 m.The minimum covering soil burial depth ratio is 0.5 and the shortest distance between the tunnel and pile foundation of the viaduct is only 3.9 m.Obvious interaction between the existing pile foundation,stratum,and shield crossing is present.Comprehensive monitoring on the ground surface settlement and pile displacement within the influential zone of shield tunnelling was conducted.Based on the monitoring data,the results of a refined 3D numerical model were compared and verified.The results show that the numerical results match well with the measured data,which both reflect the characteristics of settlement in the middle and significant upheaval on the two sides of the ground above the tunnel axis.Partial upheaval will be recovered due to unloading after the excavation.There is a significant effect of tunnel-soil-pile interaction during the side-crossing of the viaduct.The existing piles have a clamping effect on the stratum displacement induced by shield excavation,which results in asymmetric ground upheaval on the two sides.In the meantime,the deformation of the stratum synergistically drives the uplift of the existing piles.On the longitudinal ground response due to excavation,restricted by the working shaft and pile foundations,the expansion of the settlement section is limited.The shield's side-crossing causes the piles to deform laterally outwards for a maximum value of 3 mm,and induces additional axial forces in a single pile that exceeds 150 kN.
万方数据
维普
