盾构管片上浮量变化规律及简化算法研究

在大多数软弱土层盾构隧道施工中管片上浮问题十分突出,严重时往往会导致管片破损和接缝错台。为诠释该现象的发展过程,为其预防控提供合理化建议,从实际出发,利用现场试验对管片脱离盾尾后管片上浮全过程进行了跟踪监测,并记录了各上浮管片的隧道收敛变形量加以分析。分析发现,管片脱离盾尾后的上浮规律大致分为加速阶段、平缓阶段和稳定阶段,并且第一阶段管片上浮最快,其上浮变化量占总上浮量的80%左右。隧道管片脱离盾尾后随着同步注浆浆液初凝时间的延迟,其上浮量逐渐增大,当浆液初凝后上浮量增幅变缓。伴随着盾尾管片的上浮,隧道收敛变形也随之线性增加,管片的竖向压缩量与水平拉伸量的比值大体介于0.6~0.9之间,呈现“横鸭蛋”形态。此外,提出了一种简化的盾构隧道管片上浮计算方法,该方法同时考虑了注浆浆液黏度时效性、静态上浮力、地层卸载回弹力、注浆压力、管片自重及环缝处管片摩擦阻力的影响。

Research on the Simplified Calculation Method ofSegment Uplift of Shield Tunnel

The problem of segment floating is very outstanding in the construction of shield tunnels inmost soft soil layers,and in extreme cases,segment damage and joint misalignment may be caused.Inorder to explain the development process of this phenomenon,and provide reasonable suggestions for itsprevention and control,in the paper,based on project practice,the whole process of the tube segmentfloating after the segment is separated from the shield tail is tracked and monitored by field tests,and thetunnel convergence deformation of each floating segment is recorded for analysis.After analysis,it isfound that the upward floating rule of the segment after the shield tail is roughly divided into theacceleration phase,gentle phase,and stable phase,and the segment floats fastest at the first phase,withthe variation of the upward fluctuation accounting for about 80%of the total upward displacement.Afterthe tunnel segment breaks away from the shield tail,with the delay of the initial setting time of thesynchronous grouting slurry,its floating amount gradually increases.When the initial setting of theslurry,the floating amount increases slowly.Along with the rise of the shield tail segment,the tunnel’sconvergence deformation also increases linearly,and the ratio of the vertical compression amount to thehorizontal stretch amount of the segment is generally between 0.6and 0.9,showing a“horizontal duckegg”shape.In addition,a simplified calculation method for segment uplift of shield tunnel is proposed,which takes into account the effects of viscosity time effect of grouting slurry,static uplift force,unloadingrebound force of stratum,grouting pressure,segment self-weight and segment friction resistance at thecircular joint.