Research on the Template Load Values and Structural Stress Variation Laws of Secondary Lining Trolley Under Tunnel Pouring Conditions

Existing methods for calculating tunnel formwork loads often reference those used in building construction, despite significant differences in pouring processes. To address the errors in current load values that affect tunnel lining quality, this study proposes calculation methods for lateral and top formwork loads specific to tunnel trolleys. A combination of numerical simulations and field measurements was used to validate the proposed methods and summarize the structural stress and deformation patterns of the trolley during pouring. Results indicate that during wall pouring, the hardening of concrete significantly affects lateral loads, with the proposed lateral pressure attenuation coefficient α bringing the simulation results closer to measured values. During arch pouring, the distribution range of localized grouting pressure greatly affects the stress on the top formwork. The stress variation in the pillars shows significant differences under asymmetric conditions, while stresses tend to equalize under symmetric pouring. For the beams, stress variation indicates that under asymmetric conditions, the left beam experiences compression while the right beam experiences tension, whereas stresses equalize under symmetric conditions. The proposed load calculation methods align more closely with actual tunnel conditions and offer valuable insights for engineering applications.