大连地铁2号线兴工街站浅埋大跨隧道双层初期支护组合形式及合理参数分析

拱部采用双层初期支护的浅埋大跨地铁隧道工程实例十分有限,支护结构的组合形式选择与每层厚度确定还缺乏经验。针对这一问题,以大连地铁2号线兴工街站隧道工程为背景,通过现场试验与数值模拟,分析双层支护的组合形式及支护的刚度比对结构上的围岩压力及隧道上覆地层沉降的影响。研究表明:1)在双层格栅、外层型钢-内层格栅、外层格栅-内层型钢3种组合形式中,外层格栅-内层型钢最适合兴工街车站隧道,合理的支护厚度为外层35 cm,内层20 cm。2)外层初期支护为主要承载结构,承担的围岩压力随外层与内层支护刚度比增大而增大;内层初期支护为次要承载结构,承担的围岩压力随外层与内层支护刚度比增大而减小。

Analysis on Combination Mode and Parameters of Primary Support of Shallow-buried Large-Span Tunnel:Case Study on Xinggongjie Station Tunnel on No.2 Line of Dalian Metro

There have been few shallow buried Metro tunnels with double layer primary support. Therefore, there is little experience in the selection of combination mode and thickness of the double layer support. In this paper, the influence of the combination mode and stiffness ratio of double layer support on the surrounding rock pressure and ground surface settlement is studied by means of field monitoring and numerical simulation, with Xinggongjie Station tunnel on No. 2 Line of Dalian Metro as an example. The study shows that: 1) Of the three combination modes including “double lattice girder layers”, “outer layer shaped steel+inner layer lattice girder” and “outer layer lattice girder+inner layer shaped steel”, the combination mode of “outer layer lattice girder+inner layer shaped steel” is most suitbale to Xinggongjie Station tunnel, and the rational outer layer support thickness is 35 cm and the rational inner layer support thickness is 20 cm; 2) The outer layer primary support is the main load bearing structure, and the surrounding rock pressure born by the outer layer support increases as the ratio of the stiffness of the outer layer support to that of the inner layer support increases; The inner layer primary support is the secondary load bearing structure, and the surrounding rock pressure born by the inner layer support reduces as the ratio of the stiffness of the outer layer support to that of the inner layer support increases. 