Simulation on small diameter shield for pre-support method by numerical analysis

Abstract

When the road shield tunnels are constructed in urban area, the construction of branch tunnels from a main road tunnel by non-open cut method is required. Therefore, a pre-support method using several small diameter shield tunnels above and below the main shield tunnel was proposed for soft ground under groundwater level. But the small diameter shield tunnel with three dimensional sharp curve has never been constructed before, since it is difficult to control the shield along the planned alignment. Therefore, the shield operation parameters were estimated theoretically and the shield behaviors were simulated to examine the possibility of the shield tunnels using a small diameter shield with 3D sharp curve. As a result, it was confirmed that the calculated shield behavior has a good agreement with the planned one, by adjusting the shield operational parameters.