关键词: 大跨分岔式隧道, 结构设计, 连拱隧道, 钢支撑, 锚杆

Abstract: The key technologies for the structural design of largespan forked tunnel are studied, with Liantang tunnel on East Transit Highway in Shenzhen as an example. The crosssection modes of the forked tunnel, the necessity to arrange the doublearch section, the selection of steel support types and the layout of the systematic anchor bolts are analyzed by means of finite element calculation. Conclusions drawn are as follows: 1) Crosssection of “2+2 driveway” mode shall be adopted as far as possible, provided that the traffic requirements can be satisfied; 2) Smallspaced tunnel is superior to doublearch tunnel in terms of the stress conditions and the transition among the construction methods, therefore it is suggested that the doublearch tunnel section should be cancelled; 3) The forked section of largespan forked tunnel is usually arranged at positions with good geological conditions, so as to facilitate the construction of the largespan forked structure. The forked section of Liantang tunnel is arranged at the position with Grade Ⅲ rock mass. For tunnel sections with the excavation span being close to 30m, the primary support consisting of rebar lattice girder, shotcreting and bolting shall be preferred. 4) The forked section of Liantang tunnel is located in Grade Ⅲ rock mass, therefore the systematic anchor bolts should be 5m long and should be installed uniformly on the arch and side walls.

Key words: largespan forked tunnel, structural design, doublearch tunnel, steel support, anchor bolt