考虑盾构施工影响的盾构隧道管片土压力研究

Being faced with the developing trend of larger depth tunnel and larger diameter tunnel, and more complicated geological condition and more complex construction environment, shield tunnel constructers are confronted with a tough challenge. Among of those, the most essential issue is the soil and water pressure acting at the shield segments. A tunnel model will be made up with soil and flexible pipe，which is used to study the failure characteristics, failure mode of soil around the flexible tunnel. The above studies lay a good foundation for the project. On the basis, another tunnel model will also be made, which can take into account the backfill grouting with different properties, ground loss, local overexcavation and tunnel stiffness. Thus, this tunnel model can take into account the influence of segment internal forces arising by the construction process. At the same time, with use of the internal forces from model test and field test data of shield tunnel engineering, we can back analyze the soil pressure acting on the shield segment. On the base of the above analysis, finally we can clear and definite the distribution pattern of soil pressure, determination methods and critical parameters of soil pressure acting on shield segment of deep tunnel and shallow tunnel. The critical parameters are coefficient of lateral earth pressure and coefficient of resistance pressure. Finally, the research achievements will found the calculation theories and determination methods of soil pressure acting on shield segments, which more suitable to the actual shield construction conditions in our country.

我国地铁、跨江海隧道建设将面临埋深加深、直径加大的发展趋势，目前的设计经验已经无法满足发展趋势的要求，隧道上的土水压力如何确定成为了最为紧迫的研究课题。本项目通过制作土质圆形隧道无衬砌模型，研究深埋与浅埋隧道周围围岩的破坏特点、破坏模式以及两者的分界标准。在此基础上，制作考虑我国盾构施工实际情况的双层隧道模型系统，可考虑不同性质壁后注浆液、地层损失、局部超挖和隧道刚度等对管片内力影响。然后通过对隧道模型试验和现场管片受力实测数据进行反演分析，明确盾构施工过程对盾构管片土压力的影响规律，同时还可明确浅埋与深埋土质隧道拱效应的形成原理、以及管片竖向土压力和侧向土压力的确定方法。最终，形成符合我国盾构施工实际情况的盾构管片土压力计算理论和确定方法，为将来我国跨江海隧道大规模建设提供重要的理论依据，使我国在复杂地质条件隧道设计水平达到国际领先。

我国地铁、跨江海隧道建设将面临埋深加深、直径加大的发展趋势，目前的设计经验已经无法满足发展趋势的要求，隧道上的土水压力如何确定成为了最为紧迫的研究课题。本项目通过采用有限元的强度折减安全系数的方法研究，研究深埋与浅埋隧道周围围岩的破坏特点、破坏模式以及两者的分界标准，获得了浅埋与深埋盾构隧道的分界线应该在1.5倍洞径。建立了考虑壁后注浆影响有限元数值模拟方法、根据盾构现场实测反分析方法和考虑壁后注浆液的盾构管片土压力模型试验探讨了作用在管片上的土压力，主要结论如下：1）要达到拱效应其拱顶沉降需要达到16cm以上，否则拱效应发挥不完整，得到了作用在管片上土压力将大于太沙基松动土压力；2）作用在管片上竖向土压力在形成拱效应之前，呈现拱顶中心大两侧小的特点，形成拱效应后，则呈现为较为均匀的分布特点3）作用在管片上侧向土压力，大小介于静止土压力和主动土压力之间，大约为两者算术平均值，同时产生的水平方向地基抗力对于定隧道结构的稳定性提供重要的支撑。