【作者】 张俊峰；

【导师】 王建华；

【作者基本信息】 上海交通大学 ， 结构工程， 2013， 博士

【摘要】 在城市复杂敏感施工环境条件下，邻近隧道基坑发展趋势是越来越深、大、近、复杂，基坑设计、施工不当所引起的后果非常严重。如何控制基坑施工引起的周围地层移动、保证隧道运行正常和安全已经引起人们越来越多的重视。引起隧道隆起变形的基坑开挖施工过程非常复杂，基坑结构布置情况、基坑加固、基坑开挖施工过程等对隧道隆起变形都有着重要影响，但目前对于此类研究还不是很成熟。本文采用了理论方法、现场试验和三维数值模拟分析相结合的方法，对基坑开挖引起的隧道隆起问题进行了系统研究，主要内容包括：1、针对基坑开挖卸载引起的下卧隧道隆起变形，提出了可考虑软土流变特性和隧道刚度影响的解析分析方法。应用Boussinesq解求解基坑开挖卸载应力，采用Mindlin解求解隧道结构抗力引起的土体变形，结合隧道反力引起的隧道自身变形，进行隧道与土体之间作用力和变形的耦合分析，该分析方法可很方便地分析基坑开挖引起的隧道隆起变形的时间效应。在此基础上基于CAD平台编制了一套相应分析程序，应用该程序进行了参数分析，研究了隧道刚度、基坑深度、基坑开挖面积、分块开挖、基坑与隧道相对距离对下卧隧道隆起的影响规律。文献案例的分析结果表明，本方法计算所得的隧道隆起量与实测值比较吻合，反映了下卧隧道在基坑开挖卸载下的位移特性，可应用于类似工程分析。2、在解析理论分析的基础上，采用三维数值分析方法，进一步研究了地基加固、基坑围护结构措施等对控制隧道隆起变形的作用规律。建立了66个考虑土体、基坑支护体系和隧道结构模型共同作用的三维有限元模型，土体采用修正剑桥模型，分别研究了基坑坑底浅部土体加固、隧道两侧土体加固、基坑外围周边土体加固、基坑分隔墙、隧道隔离墙对减小隧道隆起变形作用的机理。结果表明，地基加固、分隔墙、隔离墙对隧道变形有显著影响，参数分析结果给出了控制隧道隆起变形的优化建议，为实际工程提供了理论依据和指导。3、针对地基加固和分隔墙、隔离墙施工引起的隧道变形，通过现场足尺试验研究了三轴搅拌桩施工的环境影响机理和控制方法。在基坑现场进行的三轴深层搅拌桩试验中对搅拌桩单桩、群桩连续施工引起的超孔隙水压力扩散和分布规律进行了研究；建立了超孔隙水压力增长预测模型。对搅拌桩单桩、群桩施工引起的周边土体水平位移、深层土体位移影响规律进行了研究，在由远及近的搅拌桩群桩施工过程中研究发现了土体位移的波动效应。根据搅拌桩施工对周边环境影响的机理，提出了控制搅拌桩引起的隧道变形的优化施工工艺，现场完成的工程应用验证了优化施工工艺的有效性。4、依托上海东西通道陆家嘴段穿越地铁二号线的基坑施工方案，应用理论分析方法和三维数值分析方法，分析了基坑开挖引起的下卧隧道隆起量与控制效果，并开展了现场测试与验证。采用解析理论方法分析的隧道最大隆起量与实测结果比较接近。采用位移反分析的方法，编制了反分析计算程序，对数值分析参数进行了反分析。通过引入权函数，在参数反分析时同时考虑了基坑开挖引起的隧道与围护墙的变形。分析了基坑围护结构的侧向变形规律和隧道隆起规律，有限元分析结果和监测数据体现了基坑开挖过程对隧道隆起的显著影响和叠加效应。更多还原

【Abstract】 Under the complicated and sensitive construction environment in urban places, the excavations adjacent to tunnels become deeper, larger and even closer to tunnels. Any improper excavation construction plan will lead to serious consequence. People have to pay more and more attention to control soil movement by excavation and make efforts to assure tunnel’s safety. But the analysis of tunnel displacement induced by adjacent excavation is very complicated, which has to take excavation structures plan, soil reinforcement and construction technologies into accounts. And the relevant research is of insufficient. In order to solve these problems, Methods of theoretical derivation, in situ tests and3-D numerical analysis are employed in this paper. The main contributions of this thesis are described as followed:In order to predict tunnel displacement induced by soil unloading of above excavation, a semi-analytical method was proposed by this paper, which could take the rheological soil and tunnel stiffness into account. By application of Boussinesq’s solution and Mindlin’s solution, soil displacement was derived from soil unloading and tunnel forces. The soil-tunnel interaction was analyzed by the coupling conditions on displacement and forces between soil and tunnel. Visco-elastic model was employed to simulate the rheologic deformation of soils, by which the time effect of soil displacement could be taken in account. series of computer software were programmed based on this method. By applying the software, the tunnel stiffness, the excavation depth, the excavation area and the relative distance to tunnel were discussed in details. The effect of segmentation and layered excavation method were also investigated. Results of two case studies had showed a good agreement between the predicted tunnel displacement and measurements, which guaranteed the effectiveness of the analysis for future similar cases.At the same time, in order to study the effect of decreasing tunnel displacement by soil improvement and additional excavation structures,663-D fem models were set up for analysis, which could consider the interactions between the soil, excavation structures and tunnel. The Modified Cambridge Model was employed for soil constitutive. The tunnel displacement was investigated when soil reinforcement was applied at different places and with different bulk. The effect of decreasing tunnel displacement by dividing wall and cutting off wall was also studied. The tunnel displacements caused by three series of excavation technologies were compared to show the rationality of proposed construction method.Further more, full scale field tests were conducted to investigate the impact of deep soil mixing (DSM) columns installation and its controlments, since DSM columns installation of soil improvement will bring extra harmful tunnel displacement. In the tests, soil horizontal displacement, deep soil vertical displacement and excess pore water pressure by single and large number of DSM columns installation were studied thoroughly. The accumulation and dissipation of excess pore water pressure were analyzed and a prediction model was also set up based on the research. The soil horizontal displacement and different depth of soil vertical displacement induced by DSM columns installation were studied and soil horizontal displacement fluctuation effect was also found. The optimal DSM column installation technologies to control tunnel displacement were also provided based on the tests and relevant research, investigations of case applications guaranteed the effectiveness of the installation technologies.For case studies, the semi-analytical method,3D FEM method and in situ measurements were employed, which deal with tunnel and retaining wall displacements induced by actual construction technologies. The predicted tunnel displacements by the analytical method were close to measurements. And the program of displacement back analysis was set up to study the critical parameters of FEM models. By employing the factors of weighing function, displacement of tunnels and retaining walls could be taken into accounts at the same time for back analysis. The horizontal displacement development of retaining wall during soil removing and after the structure construction completion were also investigated. The numerical analysis and monitoring data showed that pit excavation had great impact on the tunnel displacement and the impact was superimposition effect.更多还原