Optimal Sections of Tunnels’ Cross Sections with Different Overburdens

In order to obtain the optimal section for super-large cross-section loess tunnels with different overburdens, the ANSYS software is applied in this paper.

Based on the calculation nonconvergence criteria and Mohr-Coulomb criteria, the static stability of loess tunnel section is analyzed by the finite element static strength reduction method. According to the safety factors of rock mass surrounding tunnel in the case of critical failure, the safety factors of super-large cross-section loess tunnel is discussed with different section forms (rectangular cross-section, circular cross-section, horseshoe cross-section and curve wall cross-section) and different overburdens under gravity.

The results show that the safety factors of circular section and curve wall cross-section are bigger than the safety factors of the horseshoe cross-section and rectangular cross-section. The curve wall cross-section is considered to be the optimal section because of the fact that the force around the vault and the arch bottom is uniform and symmetrical, and the maximum vertical displacement of the lining is small. The horseshoe cross-section should be avoided in the loess tunnel, because the safety factor of horseshoe cross-section is so small, and stress concentration phenomenon is obvious in the case of deep buried tunnel.