Study On Ground Settlement Regularity Induced By Big Diametre Shield Tunnelling Construction

Shield is an important construction method in the process of tunnel excavation and is widely used in the underground engineering for its advantages of safety and convenience. However, the shield tunneling is prone to arouse land subsidence and distortion, which will have severe influence on economic and social development, especially when going through beneath the buildings on the ground. Consequently, it is necessary to study the settlement regularty during the shield tunneling construction period.In order to study the settlement regularity, documentary analysis is used to summarize the research achievement for the further discussion. By analyzing the experience, the effections that shield induced on horizontal and vertical land subsidence have been studied. Besides, the percentage of subsidence in each phase of shield excavation and its incidence to horizontal land subsidence has been discussed.Three dimensional numerical model of shield tunneling has been established by MIDAS/GTS. Combining to the condition of underground railway, two different models are built for the different ground conditions. The regulation that there is no any load on the ground is first studied for the horizontal and vertical land subsidence. Then we analysed the settlement regularity when shield excavating under the building. The influence of building loading and pile foundation can be got through comparing to the condition of no loading. The results of comparation can provide effective evidence for the construction of other sections of the underground railway.Finally, in order to guarantee the safety of the building on the ground, some monitoring points are placed around the important houses. Comparing the field monitoring value to the modeling results, we can make a conclusion that the buildings are safe when shield goes through beneath them and the simulation model and calculation parameters are rational. The modeling results and method can be used for other part of the railway engeering and similar projects in Tianjin.