软土地区桥隧合建桩基布置数值模拟研究

Numerical Simulation Study on Pile Foundation Layout of Bridge and Tunnel Co-construction in Soft Soil Area

摘要:

依托宁波某明挖隧道工程项目，针对桥梁、桥隧合建结构和隧道标准段结构，利用有限元软件PLAXIS 3D建立了三维数值模型。该模型考虑了不同桩基分布方案、桩间距和桩长等多种因素，分析它们对差异沉降的影响。研究结果表明，在桥梁段及桥隧合建段，采用桩基础能够确保承载力满足使用要求；在隧道过渡段，采用减沉桩可以通过桩土共同作用来减小沉降，实现沉降的平稳过渡；在隧道常规段，可不采用桩基础。此外，研究还发现，隧道过渡段采用10~ 30 m的桩长可以有效地降低沉降，桩长超过30 m时，对沉降的影响作用会明显下降。隧道过渡段采用加密桩间距对改善节段间的差异沉降不明显，对过渡段的整体沉降有改善效果。

Abstract:

Relying on an excavated tunnel project in Ningbo, aiming at the co-construction structure of bridge and tunnel, and the structure of tunnel standard section, a three-dimensional numerical model is established using the finite element software PLAXIS 3D. The model incorporates various factors, including different pile foundation layouts, pile spacing and pile lengths, to analyze the impacts on differential settlement. The research findings indicate that the use of pile foundations in the section of bridge and the co-construction section of bridge and tunnel can ensure the bearing capacity to meet the operational requirements. In the tunnel transition section, the use of settlement-reducing piles can reduce the settlement through the combined action of piles and soil, which can realize a smooth transition of settlement. And the pile foundations can not be used in the conventional tunnel sections. Furthermore, the study reveals that pile lengths ranging from 10m to 30m in the tunnel transition section effectively reduce the settlement. When pile lengths exceed 30m, the impact on settlement will obviously reduce. In the tunnel transition section, the adoption of increased pile spacing has no obvious effect on improving the differential settlement between segments, but has an improvement effect on the overall settlement of the transition section.