随着地铁等大型市政设施的施工，各种基坑越来越深、越来越大，深基坑支护结构型式也随之增多。基坑支护结构的主要类型有放坡开挖及简易支护、悬臂式支护结构、重力式支护结构、内撑式支护结构、拉锚式支护结构、土钉墙支护结构和其它型式支护结构。由于西安地铁车站基坑主要以平面形状规则狭长的基坑为主，且钢支撑可周转使用、降低造价，体系受地域条件、土质条件限制较小，是减少和控制基坑变形的有效手段，故主要以排桩+内支撑式支护结构为主。因此，如果我们能充分分析引起钢支撑结构变形的可能影响因素及规律，并结合工程实例进行优化设计，其研究能够为以后在湿陷性黄土中修建大型建筑提供参考经验。 本文以西安地铁一号线五路口站深基坑为研究对象。首先，在理论分析的基础上，结合现场监测数据，分别对钢支撑结构的变形影响因素基坑开挖、温度、自重进行分析；然后，根据工程具体情况，在原有钢支撑设计基础上，利用数学模糊评判方法对钢支撑结构的选材、水平布置间距、支撑与开挖面间距优化，并利用分段等值梁法计算钢支撑设计轴力，对长细比、轴心受压强度、钢支撑稳定性进行验算；最后，通过数值模拟的方法，对优化设计结果进行稳定性分析。 通过一系列研究，得出以下主要结论： （1）钢支撑结构变形的可能影响因素包括基坑开挖、温度、自重、预加轴力、钢管接头焊缝质量和钢支撑接头种类。其中主要因素是基坑开挖、温度、自重三个方面的影响，影响规律分别为：钢支撑轴向位移随基坑开挖深度的增加而增加，且支撑轴力也随之变大；支撑轴力随气温的升高而增加，随气温的降低而减少；支撑轴力越大由支撑自重产生的竖向挠度越大。 （2）适合该基坑的最优方案为：内支撑设置标准段为3 道，节点段为4道；第1道位于冠梁处，采用混凝土支撑，第2道～第4道采用钢支撑，钢管直径为Φ600，t=14，两道支撑的钢管水平间距均为4.0m，每道支撑距开挖面1m； （3）计算出钢支撑设计轴力分别为R1=398kN；R2=2196kN；R3=3866kN；R4=3890kN。并对长细比、轴心受压构件的强度、钢支撑稳定性进行验算，优化方案可行； （4）利用MIDAS/GTS软件对优化设计后的基坑进行模拟，基坑土体的轴向、横向变形以及桩体变形均符合规范要求。

With the construction of metro and other large municipal facilities, a variety of pit became deeper and larger, and the types of deep foundation pit supporting structure are also increases. The major types include step-slope excavation with simple supporting structure, cantilever supporting structure, gravity shoring structure, inner-brace supporting structure, tension anchor supporting structure and soil nailed wall supporting structure. Xi'an Metro Pit is regular, long and narrow, steel tube supporting structure can reduce the cost by reuse and it is less restricted by geographical and soil conditions, therefore the deep foundation pit usually use cluster pile-steel tube supporting structure. Steel tube supporting structure is an effective means to reduce and control the deformation of the pit, is a key factor affecting the stability of the pit. So, if we can fully understand the possible factors that cause deformation of the steel tube supporting structure and optimize it with engineering examples, the research can provide a reference for construction of large buildings in loess. In this paper, we studied the deep foundation of Xi’an metro in Wulukou station. Firstly, based on the theoretical analysis, combined with spot monitoring data, we analysised the influence factors of steel supportion structure’s deformation ,such as foundation excavation temperature、dead weight ; Then, depending on the specific circumstances of the project , on the basis of the original design of the steel support ,use mathematical fuzzy evaluation method which can optimization the material selection of steel structure, the layout distance, the Support and excavation spacing diastance. Design and use of computing steel support beam equivalent axial force segmentation method, checking calculate the structure design,the slenderness ratio, axial compressive strength; Finally , through numerical simulation , analysis the stability of optimization design. Finally, through numerical simulation, it carries on stability analysis with optimization design: (1)We analysised the influence factors of steel supportion structure’s deformation ,such as foundation excavation temperature、dead weight、axial preload、dissimilar steel pipes for boiler、the mode of the junctions.The temperature、dead weight、axial preload are key factors of steel supportion structure’s deformation. The Influence rules: with the increasing depth of axial preload, steel supports of axial displacement is increased; with the increasing temperature, steel supports of axial is increased; with the increasing depth of vertical deflection, steel supports of axial displacement is increased. (2)Optimization program: in standard norm criterion sets three; in standard norm criterion sets three and in pitch pointsets four; the first sets on the top beam with concrete, from second to fourth of the suppuration we use steel sup portion, the diameter of steel is Φ600,t=14, the level space length is 4.0m, the of vertical deflection is 1m. (3)The steel tube bracing axial pressure are R1=398kN；R2=2196kN；R3=3866kN；R4=3890kN. finally, the use of reason is deep foundation design software for checking, including Slenderness ratio checking, axial compressive strength of the checking; (4)The use of MIDAS/GTS simulation software, model building, the foundation pit to simulate the process.