盾构近距离穿越施工的工作面土压力研究

盾构近距离穿越已建地下构筑物位移场的影响因素及其敏感性与常规施工有较大的不同。结合上海地铁四号线隧道超近距离穿越运营地铁隧道的工程实例发现当盾构接近上方近距离（净距为1.05 m）地铁隧道时地层土压力发生较大变化，相应的盾构土舱管理压力需作相应调整。根据隧道受荷机理及弹性力学原理，找到了这一问题的理论依据，便推导了相关理论公式，并在实际工程中设计了盾构土仓管理压力分步台阶控制方案，对盾构控制起到了很好的指导作用，成功地将地铁位移控制在5 mm之内。土压力实测结果与理论推算的数值大小及分布相当接近，说明所采用的理论方法是正确可靠的，在盾构超近距离穿越施工中具有重要指导意义。

Approach to earth balance pressure of shield tunneling across ultra-near metro tunnel in operation

The affecting factors and sensitivity of the displacement fields produced by the shield tunneling across the ultra-near tunnel obviously differ from that of the general construction. Combining the metro tunneling examples within ultra-near distance (1.05 m)in Shanghai, It is found that the earth pressure varies significantly while shield approaching to adjacent metro tunnel in operation situated overhead. Based on the principles of tunnel loading model and theory of elasticity a, theoretical formula of earth balance pressure of shield was deduced and a so-called “step control strategy” was concluded which was successfully applied in a typical project of Shanghai metro tunnel line No.4 of which the maximum displacement was controlled within 5 mm. The field measurements of earth pressure proved to be at good coincidence with the theoretical values.