Abstract: With the rapid development of urban surface roadways and underground rail transit traffic, the influence of deep excavation on the existing underlying subway tunnels is becoming increasingly prominent. A roadway deep excavation project in Chengdu area is presented in this paper. A three-dimensional numerical model is established by using software FLAC3D to predict the influence of roadway deep excavation on the underlying underground subway tunnel. The results indicate that the unloading of deep excavation results in the change of displacement and stress fields. The upheave deformation and the lateral displacement of tunnel are observed. The backfilling and compacting of the excavation also induce the settlement and deformation of the tunnel. The tunnel is deformed by the tension and the compression towards the open surface. The tunnel is deformed in the shape of ellipse with the short side in transverse direction and the long side in vertical direction. When the soil cover of the tunnel is shallow, the roadway compaction conditions has a significant effect on the tunnel deformation, and the grouting improvement can better control the tunnel deformation.

Key words: Deep Excavation, Tunnel Deformation, Numerical Model, Grouting Improvement