English：

In order to further explore the mechanical characteristics of the construction of complex special-shaped open-cut tunnels, taking the reconstruction project of the extension section of Jinzhou Avenue and Xingguang Avenue in Chongqing as the engineering background, on the basis of clarifying the differences and stress characteristics of the stress states of each tunnel of the special-shaped tunnel, the joint control measures of targeted spraying anchor support and C15 concrete replacement treatment were proposed, and the concrete replacement depth on both sides of the bottom tunnel was analyzed.The findings reveal that by a series of numerical simulations, the noteworthy mechanical properties of complex open-cut special-shaped tunnels may be reduced to the critical areas of substantial shear failure, notable stress concentration, deformation, and stress abrupt change. The disturbance caused by the latter tunnel and backfill construction dramatically affects the first-built tunnel, resulting in serious shear failure, posing the greatest danger of damage. When the concrete replacement depth reaches 11m, the shear stress of each tunnel is efficiently managed, reducing it by 43.5%, 27.5%, and 5.9%, respectively, and eventually meeting the ultimate shear strength criteria, effectively ensuring the safety of tunnel backfill construction.