Abstract: Large post construction settlement is usually observed at the excavated area of a cut and cover tunnel excavation area. This paper presents an excavation of a cut and cover tunnel in soft soil area. The effect of the shape of the tunnel cross section and the backfill material on the settlement of the excavated area and the structural deformation of the tunnel are numerical investigated by using MIDASGTS geotechnical commercial software. Results show that the ground settlement after the completion of backfilling is mainly affected by the compressibility of the backfill material itself, that is, the greater the compressibility of the backfill material, the greater the surface settlement. The main factors that affecting the settlement and deformation of the tunnel structure are the unit weight of the backfill material and the thickness of the weak stratum below the tunnel. Therefore, for the excavation of the cut and cover tunnel, it is necessary to select an appropriate method for the backfill soil in accordance with the allowable deformation criteria for backfill material and for the tunnel strucutre.

Key words: Deep Excavation, Backfill, Finite Element Method, Settlement