【作者】 吴加武；

【导师】 韩金田； 刘勇健；

【作者基本信息】 广东工业大学 ， 岩土工程， 2012， 硕士

【摘要】 随着城市地下空间的大规模开发,基坑开挖的工程环境日趋复杂。基坑开挖会使其临近的已建建筑物、地铁隧道等地下空间结构产生附加变形等效应。基坑开挖的变形控制越来越严格,从而推动基坑设计趋向于正常使用状态设计。目前国内外已有不少相关工程实例的研究,这些研究表明,基坑开挖会使侧方隧道产生位移与不可忽视的自身变形,影响隧道的安全运行。但是,由于该课题的复杂性以及工程环境的特殊性,对于基坑开挖对紧邻地铁隧道影响的理论研究以及变形控制措施还需进一步探讨研究。首先,基于位移控制有限元法(DCFEM),利用归一化围护墙体基本位移模式分析了基坑开挖墙后土体水平位移场的变化规律,间接地研究基坑开挖的环境效应问题。其次,结合数值模拟技术以及理论研究成果,提出了基于DCFEM的适用于基坑开挖对地铁隧道影响的预测方法,建模简单,概念清楚,简单合理,能为工程技术人员提供合理、快速的预测方法。再次,以广州某紧邻地铁隧道的宽大基坑工程为背景,通过规范方法和数值模拟方法比较不同变形控制措施的效果以及基坑与隧道的相互作用性状,研究结果表明：基坑开挖引起隧道斜向下、不对称的变形,隧道对基坑有“加筋”作用,水平位移主要发生隧道与支护结构之间,两者形成一个“阻隔区”,能减小水平位移向远处的传递；在浅岩地区,带撑双排桩支护结构联合中心岛开挖工法不仅能有效控制支护结构及地铁隧道的变形,还能取得很好的经济效益；与规范方法相比,数值模拟能考虑材料的非线性和基坑的空间效应,能将基坑与隧道作为整体考虑,能模拟各种开挖工法,优势明显。最后,采用有限元分析了带撑双排桩支护结构的工作性状,并对其进行参数以及经济效益的对比分析,结果表明：带撑双排桩不仅能有效控制位移,也能减少桩身弯矩,其变形性状符合柔性结构的变形特征,设计中可选用小直径后排桩,增加前排桩桩径,或在后排采用疏排桩,前排采用密排桩,增大排距,减小连梁截面,寻求最优支撑位置,其分析研究成果有利于该种新型支护形式在工程上的推广应用。更多还原

【Abstract】 With the large-scale development of urban underground space, engineering environment of excavation is becoming increasingly complex. The excavation of foundation pit will make it to the neighboring buildings, subway tunnels have been built underground space structure deformation effect. Increasingly stringent deformation control of excavation, thus promoting the design of pit tends to the normal use of state design. Presently there has been many studies of relevant projects, these studies suggest that the foundation pit excavation exposes displacement of the tunnel on the side and its own deformation that can not be ignored, which will affect the safe operation of the tunnel. However, due to the complexity of the subject and the particularity of the engineering environment, theory of the pit excavation close to the subway tunnel and the deformation control measures needs further study.This article based on DCFEM numerical simulation method, using normalized basic model analyze the impact of the foundation pit excavation on the surrounding soil, and indirectly analyze the environmental effects of the excavation. Secondly, the combination of numerical simulation techniques, as well as the results of theoretical studies, the establishment of applicable prediction model for impact of foundation pit excavation on the subway tunnel based on DCFEM, the model has modeling simple, clear concept, simple and reasonable, it can provide dynamic, rational,fast prediction methods for engineering and technical personnel. Again,Taking a wide excavation engineering close to the subway tunnel in Guangzhou as background, using gauge methods and numerical simulation methods to compare the effect of the displacement control of different supporting structure of the foundation pit,and the interaction of traits of the pit and tunnel, the results show that:oblique, asymmetric deformation of tunnel caused by the excavation, the tunnel "reinforced"the pit the horizontal displacement occurs mainly between the tunnel and the supporting structure, the two form a "barrier zone"that can reduce the horizontal displacement to the distance delivery. In areas of shallow rock, double-rows pile with brace-center island construction method not only can effectively control the deformation of the support structure and subway tunnels, but also achieved very good economic benefit;Compared with the standard method, numerical simulation can take into account the effect of material nonlinearity and spatial of foundation pit,and foundation pit and tunnel is considered as a whole, as well as can simulate all kinds of excavation method, so the advantage of numerical simulation is obvious.Finally,using numerical analysis, analysis of the force and deformation behavior of double-rows pile with brace, and comparative analysis of its parameters and economic benefits, in favor of the new form support in the promotion and application of engineering. The results show that:double-rows pile with brace in line with the deformation characteristics of the flexible structure, it meets the displacement control and economic benefits of the combination of requirements, small-diameter rear piles, and front row pile diameter, or in the post-row using the sparse pile, front close-packed pile, increasing row spacing, reducing the coupling beam cross section, to seek the optimal support position, which should be used in design,the results in favor of the new form of support in the promotion and application of engineering更多还原