大盾构管片最不利上浮状态下三维形变特征模型试验方案设计OA北大核心CSTPCD

The buoyancy of slurry on the segment is not constant during tunnel construction,and the uneven distribution of slurry pressure behind the wall will lead to segment deformation and dislocation damage of tunnel ring.To mitigate or prevent structural damage resulting from segment up-floating,this paper analyzed the transient deformation under the most unfavorable uplift condition of the segment.This analysis was conducted using a specially designed and developed three-dimensional load test system for the model segment,which took into account the influences of the horizontal thrust from the jacking force,the pressure from the surrounding rock,and the buoyancy from synchronous grouting.The test device is composed of confining pressure loading device and non-uniform buoyancy loading device,which can realize single or multiple point synchronous loading and unloading.The model tests utilizes springs with varying stiffness to replicate the interaction between the tunnel and the ground layers during the uplift phase.According to the similarity theory,the segment model and connecting bolts are designed and processed finely.The initial value of the confining pressure of the model tunnel is converted according to the confining pressure of the tunnel in the actual project,along with considering both dynamic and static buoyancy,a more accurate model for transverse and longitudinal uplift forces in the actual shield tunnels is proposed.The result revealed that under the influence of the non-uniform uplift force,the vertical displacement of the arch bottom and convergence deformation exhibit an approximate lognormal distribution along the longitudinal direction.The maximum values are observed in the third ring after disengagement from the shield tail.The convergent deformation and vertical displacement of each segmented ring exhibit approximate linearity,characterized by function slopes ranging from 0.63 to 1.49.The model test results are consistent with the measured data.The research results offer valuable technical support for the design and construction of anti-floating shield tunnel.