The actual project of the viaduct foundation near Lanzhou metro shield tunnel was analyzed .By simulating the progress of shield excavation and lining construction with numerical methods , a three-dimensional numerical model of stratum configuration ,soil condition ,viaduct and its foundation was established .According to the numerical analysis of one-way and two-way tunnel excavation ,the changing rule of stratum deformation of overlying surrounding rock ,stress on the lining structure ,stress on the viaduct structure and its foundation as well as its deformation was obtained .The result showed that a subsider was formed in the overlying soil stratum ,and its settlement curve presented a normal distribution . After the completion of the excavation ,the lower part of the pile began to incline and deform towards the tunnel ,while the upper part remained unchanged .The influence of horizontal stress and axial force increased from the top downwards . The measure of spray grouting reinforcement before the shield excavation was taken to ensure the construction safety . From the comparison results ,it is drawn that this means of reinforcement has an observable effect on reducing the differ-ential settlement and shield construction disturbance .%以兰州地铁盾构隧道穿越高架桥基础的实际工程为分析对象，通过数值方法模拟盾构开挖、衬砌施工过程，建立了地层结构及土性条件、高架桥及其基础的三维数值计算模型，开展了盾构隧道单向开挖及双向开挖完成的数值分析，得到了隧道上覆围岩地层沉降变形、衬砌结构应力、桥梁结构应力、桥基应力和变形变化规律。表明隧道上覆土层形成了沉降槽，其沉降曲线呈正态分布；开挖后桩身倾斜变形，桩身下部向洞内方向收敛变形，桩顶保持不变位；桩身的水平应力及轴力影响自上而下逐渐增大。为保证施工安全，对盾构开挖进行超前喷浆加固，对比结果表明注浆加固方法对减小不均匀沉降及盾构施工扰动具有明显效果。
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