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针对北京某地铁区间下穿高速铁路工程,分析不同盾构参数及支护条件的选择对隧道侧穿既有高架桥群桩的受力和变形的影响。在隧道开挖前的工程试验段中,建立盾构参数与有限元计算中等代层之间的关系。分别分析不同等代层和有无隔离桩的六种工况,说明盾构参数的优化及隔离桩的使用在盾构隧道开挖中对控制群桩的受力和变形所起到的作用。分析表明:1)盾构参数优化和隔离桩的使用对控制桥桩弯矩、水平位移、轴力、沉降都有明显作用,但隔离桩控制效果更显著;2)隔离桩的存在基本消除了隧道掘进过程中桩体的弯矩动态变化,并且使得隧道推进过程对桥桩沉降的影响是均匀的;3)监测结果表明,数值计算结果较好的反映了实际开挖过程,计算最终累计沉降量与实测结果非常接近。
Aiming at the high-speed railway project under the subway in Beijing, the influence of different shield parameters and support conditions on the stress and deformation of the pile group with side-pierced existing viaducts in tunnels is analyzed. In the engineering test section before tunnel excavation, the relationship between the shield parameters and the middle-layer calculation of the finite element method is established. Six kinds of working conditions of different substitutive layers with or without isolation piles were analyzed respectively. The optimization of shield parameters and the role of isolation piles in controlling the stress and deformation of group piles in shield tunneling were analyzed. The analysis shows that: 1) The optimization of shield parameters and the use of isolation piles have significant effect on the control of bridge pile bending moment, horizontal displacement, axial force and settlement, but the control effect of isolation piles is more significant; 2) The existence of isolation piles is basically eliminated The bending moments of the pile during the tunneling process are dynamically changed, and the influence of the tunneling process on the settlement of the bridge piles is uniform. 3) The monitoring results show that the numerical results better reflect the actual excavation process and calculate the final cumulative settlement The amount and the measured results are very close.