Reflections of Advanced Support of Leading Pipe-Shed in Portal Section of Loess Tunnel

Currently, advanced support technology of leading pipe -shed is often used in the excavation of the portal section, but the design parameters of leading pipe -shed and the support structure haven't yet form a unified standard. The author analyzes its force theory and design parameters. Combined with the effects of advanced support, the paper raises several issues for further research, taking the role of scaffolding into account.