盾构施工对临近桩基影响的数值模拟及参数分析

采用数值模拟软件对盾构隧道施工近距离下穿桩基进行三维仿真模拟，研究双线盾构动态掘进时桩基位移的变化。数值模拟实现了盾构施工时的步步掘进，考虑了土仓压力、注浆压力、盾构与土体摩擦力等施工参数的影响；利用PLAXIS 3D的固结计算，考虑盾构机自重对土体的固结作用引起的地层沉降，并由此考虑开挖速度对桩基位移的影响。计算结果表明：隧道开挖将导致桩基发生沉降、侧移以及倾斜，桩基的整体位移以及倾斜都随盾构施工的进行不断增加。施工参数敏感性分析表明：增大开挖速度可以有效控制桩基位移，但当开挖速度增大至一定程度时，开挖速度对桩基的影响逐渐减小；双线隧道同步开挖时对桩基的影响比双线分别开挖时小。

Numerical study and parametric analysis of influence of tunnel excavation on adjacent pile foundation

To study the change of the pile foundation displacement during the dynamic excavation of the double-route shield tunnel, three-dimensional simulation of shield tunneling under-crossing pile foundation is performed with a finite element package, PLAXIS 3D. Numerical simulation realizes the step-by-step advancing during shield tunnel excavation by taking into account the influence of earth pressure in soil warehouse, grouting pressure, and friction between the shield and the soil. Apart from that, using consolidation calculation of PLAXIS 3D, the paper evaluate the ground settlement caused by consolidation of the shield''s own weight on the soil, and further evaluated the impact of the excavation speed on the pile displacement. The calculation results show that the tunnel excavation will cause the settlement, lateral displacement and tilt of the pile foundation, and the overall displacement and tilt of the pile foundation can continue to increase with progress of the shield tunnel excavation. The sensitivity analysis of construction parameters reveals that: increasing the excavation speed can effectively control the displacement of the pile foundation, but when the excavation speed increases to a certain extent, the impact of the excavation speed on the pile foundation is significantly reduced; The effect of simultaneous excavation of the double-route tunnel on the pile foundation is less significant than that of the separated double-route excavation.