Considering the special condition of the six lanes large-span multi-arch tunnel in the Wanping Expressway

and choosing some representative cross-sections of Wujiazhuang Tunnel

their inner middle-wall's internal forces of the three-layer vertical middle-wall are monitored during the construction. Based on the monitoring data

and considering the interactive influences of different construction stages

the internal forces of the inner middle-wall are analyzed; and the mechanical characteristics during the construction are obtained. Then the safety performance of the Wujiazhuang Tunnel's inner middle-wall is evaluated. It is shown that the inner middle-wall's internal forces are affected by the different excavating sequences

especially in the stage of low bench excavations

however

the inner middle wall remains stable during the multi arch-tunnel construction.