土岩复合地层浅埋大跨地铁隧道支护理论和结构荷载特征研究

To solve the problem of design theory lag and stratum deformation control in the construction of shallow buried long-span metro tunnel in complex environment of rock mass in cities like Qingdao, Chongqing, it is studied that the support design mechanism and deform control method of the long-span metro tunnel construction in rock-soil composite stratum, by means of engineering survey, statistical analysis, model test and numerical analysis. The study is focused on the engineering mechanical property evaluation method of rock-soil composite stratum and the formation mechanism and boundary condition of the longitudinal arch in excavation unloading condition; the interaction bearing mechanism and time-dependent deformation of the surrounding rock- primary support complex structure-secondary lining integrated system in the construction of metro tunnel; the spatial-temporal evolutional laws and optimization design methods of the tunnel; with establishing the method of the deformation distribution proportion of key steps and the prediction and control of ground deformation in the shallow buried long-span tunnel excavation, combining organically the field measured data feedback, and truly realizing the information construction and deformation active control technology. Through this study, the key technology system for supporting design of shallow buried long-span tunnel construction is intend to be created for being adapted to the mountain city in our country, promoting the tunnel design transportation from qualitative analysis to quantitative analysis in the same condition in our country.

针对重庆、青岛等城市复杂环境下岩体中修建浅埋大跨地铁隧道时支护设计理论滞后和衬砌荷载难以定量确定等难题，采用工程调研、统计分析、模型试验和数值分析等综合手段，探索土岩复合地层整体工程力学性能定量评价方法、开挖卸荷时纵向成拱机理及临界跨度；揭示围岩-支护复合结构+二衬联合体系相互作用机制、承载机理和时空变形规律；阐明钢筋混凝土二次衬砌结构的施做时机和荷载特征；建立一套土岩复合地层条件下城市浅埋大跨隧道围岩-支护联合作用分析方法，发展完善城市大跨浅埋隧道设计理论，促进我国该类条件下隧道设计由定性向定量的转化。

研究了不同土层、岩层组合方式及开挖进尺等因素下，围岩压力拱的形成机制，确定了岩层覆盖厚度与导洞临界跨度的关系，建立了基于压力拱临界跨度的围岩稳定性定量评价方法。结合室内模型试验数据，利用数值分析软件，通过改变围岩应力释放率模拟初支和二衬支护时机对围岩变形和结构荷载变化规律的影响，建立了考虑多导洞、多步序施工相互影响的围岩-初支复合承载结构时效变形分析模型，为大跨隧道的断面划分方式和开挖步序的合理设置提供理论依据，并将理论研究结合实际工程进行了应用验证，取得了良好的经济效益。