Research on the determination and influencing factors of topographic unsymmetrical-loaded tunnels based on the unsymmetrical coefficient

Abstract

Abstract The accurate judgment of topographic bias tunnels is directly related to reasonable tunnel design and construction safety. In this study, numerical simulations were carried out to determine the unsymmetrical coefficient of topographic unsymmetrical-loaded tunnels, according to the critical thickness of the cover layer of the topographic bias tunnel proposed in the Chinese Code. The unsymmetrical coefficient was analyzed via control variable method and orthogonal test method. The results showed that it is appropriate to take 1.2 as the criterion for all types of topographic unsymmetrical-loaded tunnel in practical application. The influence of different topographic factors, mechanical properties of the surrounding rock, rock quality, construction methods and tunnel spans on the unsymmetrical coefficient were summarized by the control variable method. The results of multifactor analysis under an orthogonal design revealed that the influence of Uc is in the following order: slope angle, overburden thickness, construction method, surrounding rock quality, and height-to-span ratio. Article Highlights The Chinese code for topographic unsymmetrical-loaded tunnels presents a the determination of the corrected unsymmetry coefficient. Single-factor analysis determines the change pattern of the corrected unsymmetry coefficient under the influencing factors. Polar analysis based on orthogonal tests determines the strength of the factors influencing the corrected unsymmetry coefficient.

Keywords

• Unsymmetrical-loaded tunnel
• Unsymmetrical coefficient
• Numerical simulation
• Multifactor analyses