【作者】 刘海荣；

【导师】 季荣生； 孙胜臣；

【作者基本信息】 中国地质大学（北京） ， 建筑与土木工程， 2009， 硕士

【摘要】 由于浅埋软弱地层隧道施工难度大,洞室变形量大,稳定性差,其变形特征和施工技术一直是岩土工程界研究的焦点。关角隧道Ⅰ、Ⅱ线西宁进口段存在约450m长的浅埋砂层隧道,地层工程力学性质差,受一定的山体偏压影响,施工风险较高,且隧道工期压力大,因此开展浅埋砂层隧道开挖洞室稳定性和安全施工技术研究具有现实的工程意义。本文具体研究内容为:1.论文首先介绍了浅埋砂层隧道的施工与变形机理的国内外研究现状,总结了砂层隧道施工中成熟、先进的施工经验和理论成果。2.论文在介绍关角隧道入口段的工程地质及水文地质等的前提下,针对该区段提出了三种备选施工方法——明挖法、盾构法和暗挖法。对于三种备选方法筛选,论文运用了模糊评判理论,从入口段浅埋砂层隧道的工程特点出发,对三种隧道施工方法的适宜性从施工安全、施工进度、社会经济效益和对环境影响等角度进行了综合评判,按照最大隶属度原则,选出了隧道入口段最优施工方法,即推荐关角隧道浅埋砂层进口段采用暗挖法施工方法。3.对于暗挖法施工下隧道围岩的变形特征研究,本文选用了数值模拟手段,分析了关角浅埋砂层隧道在不同应力释放率下围岩变形和塑性区变化规律,结合突变理论,定义了隧道的极限状态和极限位移,即当应力释放率达到80%时,围岩稳定状态为极限状态,对应的位移(拱顶下沉为90mm,水平收敛为160mm)定义为极限位移。4.为了掌握隧道施工过程中位移变化规律和支护受力情况,建立了三维有限元数值模型,对四台阶施工方案进行了模拟,得出施工过程中围岩最大拱顶下沉量和最大水平收敛量分别为35mm和64mm;支护结构最大拉、压应力基本上位于横撑与支护结合部位,大小分别为1.89MPa和-13.6MPa,皆小于C25混凝土极限强度。表明在该施工方案下,洞室稳定,支护结构安全。5.最后,通过实际的工程实践和探索,形成了浅埋砂层隧道的关键施工技术:①设置长大超前水平管棚,全断面设置超前小导管;②采用超短台阶法开挖;③设置临时横向水平钢支撑控制边墙变形。6.现场的地表下沉、内空变形监测结果表明,与原设计方案相比,采用改进后的四台阶方案施工的洞室变形明显减小,稳定性增强。更多还原

【Abstract】 The deformation behavior and construction technology of the shallow-buried sandy stratum tunnel have been the research focus in the Geotechnical engineering field due to its difficulty to construct, large deformation and poor stability. There have been shallow-buried sandy stratum of 450 metres long in the Xining entry segment of Guanjiao Tunnel. Because of the poor mechanical behavior of rockmass and the unsymmetrical pressure condition, there has been high danger to construct. So it has realistic engineering value to carry out research on the stability and construction technology of the shallow-buried sandy stratum tunnel. The detailed contents are as fellows:1. Firstly, the study actuality of internal and overseas were introduced about the construction and deformation behavior of shallow-buried sandy Stratum tunnel. The relative mature, advanced construction practice and theory achievements were also summarized. Then the Geotechnical and hydrological geology were three introduced, alternative construction methods - cut-and-cover method, shield method and mining method were presented .2. Based on the engineering charaters of the shallow-buried sandy stratum in the entry segment of Guanjiao tunnel, Fuzzy Judgment theory was adopted to evalue the three optional construction methods. By comprehensive evaluement of the three methods form aspects of safety, construction process, economic benefit and environmental influence, the optimal method was choosed. Mining method was recommended to the entry segment of Guanjiao Tunnel.3. Numerical simulation method was adopted to analyse the deformation and plastic area changing rule of surrounding rock under different stress release rate of Guanjiao Tunnel. Based on above results and catastrophic theory, limit state and limit displacement were defined . When the stress release rate reach to 80%, the state of surrounding rock was defined as limit state, and the corresponding displacement(i.e. settlement of vault is 90mm, interior horizontal convergence is 160mm ) was defined as limit displacement. 4. Based on 3D finite element numerical model, the modified construction method was simulated and the displacement of surrounding rock and stress distribution of support structure were analysed. The maximal settlement and horizontal converge of surrounding rock were respectively 35mm and 64mm . And the maximal tension and compression stress of primary support were respectively 1.89MPa and -13.8MPa. It was concluded that new construction technology could control deformation of tunnel, improve the stability and assure the safety of support structure of tunnel.5.At last, the key construction technologies of shallow-buried sandy stratum tunnel were formed by practical engineering practice and exploration, i.e.①setting long and large advanced horizontal roof pipes and full-face advanced ductule;②mini four-steps excavation;③setting temporary horizontal steel brace to control deformation of surrounding rock.6.From monitoring measurement of ground settlement and interior deformation, it was concluded that the deformation of tunnel markedly minished and stability improved compared with the former design scheme.更多还原