Prediction of ground movements around tunnel due to excavation by EPB machines (Case study; three line of Tehran subway)

The development of large cities requires the use the underground networks for the construction of transportation infrastructures and facilities. Construction of tunnels in soft grounds induces generally soil movement، which could seriously affect the stability and integrity of existing structures. In order to reduce such movements، in particular in urban areas، contractors use more and more the tunnel boring machines (TBM) for the construction of tunnels. Hence in urban environment، Prediction of the ground movements caused by the tunnel excavation is a major engineering challenge. In this paper is used a three-dimensional numerical model and ABAQUS cod for the prediction of soil movements induced during tunnel construction in part of the line 3 of Tehran subway using EPB excavation machine. This investigation include most shield tunneling components such as face pressure، the grouting pressure، excavation machine and frictional contact with soil and shield. Observations of the results demonstrate that the maximum surface settlement in this section is 2. 5 cm that is 0. 5 cm more than the its allowable value. Simultaneously with surface settlements occur horizontal movements within soil mass، which have different forms in two horizontal directions، and with the expansion of depth they increasing.