Study on TBM launching in parallel with small spacing

The launching of a tunnel boring machine (TBM) is very important in the tunnel construction procedure, but it also has great risk. Water and slurry may burst into the shield work well in the case of an inappropriate launching process, resulting in the collapse of the work well. Generally, one work well of a tunnel station is uniquely designed for one TBM. The condition where two tunnels or more share one shield work well is rare. Based on the tunnel construction project of metro line 1 in Hangzhou, the special problem of TBM launching from one work well that had three tunnels in parallel was studied. The minimum spacing between tunnels was 1.83 m, which was only approximately one-third of the diameter of the tunnel. The most dangerous situation of middle TBM launching was studied, which had great influence on the two existing side tunnels. A finite element (FE) program was adopted to simulate the grouting reinforcement around the side tunnels. The stresses and displacements of the two side tunnels during the middle tunnel launching progress were studied. The effects of grouting reinforcement and different reinforcement regions were compared to guide the reinforcement construction. By real-time monitoring of the displacement of side tunnels and ground settlement, the grouting reinforcement and TBM operation measures were modified and adjusted, ensuring the successful launching of the TBM.