Design Optimization Method of Feet-Lock Steel Pipe for Soft-Rock Tunnel Based on Load-Deformation Coordination

Feet-lock steel pipes have been widely applied in soft-rock tunnels, but their installation quantity and parameters depend on engineering experience. In this study, by simplifying the force between feet-lock pipe primary lining, load-deformation characteristics were analyzed separately, inconsistent deformation was revealed. Next, combined with passive active bearing scheme, a design optimization method for proposed under two working conditions, including predicted large observed before lining construction. Finally, to Yulinzi Tunnel, results show that original of could not meet requirements controlling settlement. After optimized design, both scheme installing ?108 × 3-millimeter one 4-millimeter The can significantly reduce amount required cost. scientificity feasibility proven on-site monitoring measurement.