Abstract: The opencut tunnel structure has many problems such as single structure form (mostly rectangular structure), few scheme studies, and insufficient innovation in crosssection form. As a result, a case study is conducted on the Sirine tunnel in Serbia, and two kinds of specialshaped crosssections out of China are selected to conduct comparison with traditional folded plate arch and rectangular crosssection in terms of mechanical characteristics and economy. The results reveal the following: (1) The arch part of the "flat bottom + round arch" crosssection scheme has good stress characteristics and visual effect, but the bottom plate has poor stress conditions and economic benefit. (2) The combination crosssection scheme has the best economic benefit and the force of each component is clear, but the waterproof effect and integrity of the structure are poor. (3) The crosssection of folded plate arch is similar to that of rectangular crosssection. Although the two have general mechanical characteristics and economic benefit, they have the advantages of small foundation pit scale, high utilization rate of space, good waterproof effect, and simple construction. The specialshaped crosssections in case study can provide reference for the selection and optimization of the crosssection form of opencut tunnel.

Key words: opencut tunnel, specialshaped structure, mechanical characteristics, crosssection form