Abstract：
Steel arch is often used as supporting element in soft rock tunnelling, while it is difficult to control the external angle of advanced condulet when the distance between two rows of steel arch is less than 1 m. In order to reduce the external angle, perforation in web of steel arch was conducted during site construction. A 3D model was established to calculate the deformation of steel arch under different ranges and densities of perforation, and the influence of perforation on stiffness of steel arch and support system was studied. In light of the results of contrast test,measured deformation of primary support, pressure of surrounding rock and internal force of steel arch, it is found that perforation interval is the main factor affecting stiffness of steel arch; for the studied tunnel project, the recommended safe perforation interval of steel arch is 40 cm or larger than 40 cm, with stiffness decrease of the steel arch being less than 4% and the stiffness of primary support being barely decreased.
2019, Vol. 56 