Jiangwei Shi

Performance of a Deep Excavation and Its Effect on Adjacent Tunnels in Shanghai Soft Clay

AbstractA 267-m-long, 54-m-wide, and 14.9–16.4-m-deep multipropped deep excavation with three cross walls in Shanghai soft clay was constructed at a side of an existing metro station. To investigate the performance of this deep excavation and the effect of this deep excavation on adjacent metro station and shield tunnels, the ground deformation and structure responses were extensively monitored. Based on the field observations, the deflections and vertical movements of diaphragm walls, surface settlements, vertical and horizontal displacements of the up track and the down track within the station and nearby shield tunnels, as well as tunnel convergence were extensively analyzed. By adopting cross walls, jet grouting and large dimension concrete struts, the measured maximum lateral wall deflection and ground deformation were much smaller than those at other sites without installing cross walls in Shanghai soft clay. The maximum excavation-induced lateral wall movements and ground settlement behind the reta...

Three-Dimensional Centrifuge Modeling of Ground and Pipeline Response to Tunnel Excavation

AbstractTunnel excavation inevitably induces stress changes in the surrounding soil leading to significant ground movements and additional stress in nearby pipelines. Most previous studies simplified tunnel–pipe interaction as a plane strain problem and focused on the case in which the pipeline intersects the tunnel perpendicularly. In this study, centrifuge tests were conducted to investigate the three-dimensional response of the ground and pipeline to tunneling, considering different pipeline orientations with respect to the tunneling direction. When the tunnel face was located within ±1.25D (tunnel diameter) away from the monitoring section, the ground settlement and pipe strain induced were more than 95% of the maximum recorded. When the pipeline intersected the tunnel perpendicularly, the maximum pipe strain always occurred above the tunnel centerline. However, when the pipeline intersected the tunnel at an angle of 60°, the location of maximum pipe strain shifted as the tunnel advanced. The maximum ...