Numerical Analysis of Influence of Large-Diameter EPB Shield Tunneling on Ground Deformation in Beijing Area

A large-diameter earth pressure balanced (EPB) shield has been firstly used in the Beijing metro line 14 in China. In this paper, to take the experimental project of the metro line 14 as an engineering background, the tunneling process of the EPB shield with an outer diameter of 10 m was simulated using the three-dimensional finite element method. The numerical results show that the ground settlement mainly appears in three phases during the shield tunneling: before the arrival of shield, the arrival of shield and the grouting phase, and they take respectively 32%, 45% and 23% of the total settlement. During the backfill grouting, the soil deformation around the segments goes up in the normal direction of the segments with the increase of grouting pressure. However, as the grouting pressure decreases, the rebounding of ground deformation occurs. Only increasing the grouting pressure to control the ground deformation is not effective. The influence of supporting pressure in soil chamber on excavation soil disturbance is evident. When the supporting pressure is less than a half of earth press at rest, the excavation face may be not stable and collapse during the shield tunneling, however, when the supporting pressure is more than 2 times earth press at rest, the soil ahead of the shield cutter is obviously squeezed.