明挖隧道下穿桥梁工程中既有桩注浆加固方法与应用
张海东
Grouting Reinforcement Method and Application for Existing Piles in Open-excavation Tunnel Under-passing Bridge Engineering
ZHANG Haidong
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作者信息:中铁上海设计院集团有限公司，200070，上海
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Affiliation:China Railway Shanghai Design Institute Group Co., Ltd., 200070, Shanghai, China
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关键词:
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Key words:
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DOI:10.16037/j.1007-869x.2024.07.025
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中图分类号/CLCN:U433.17
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栏目/Col:研究报告
摘要:
［目的］明挖法新建隧道下穿桥梁时，需重点保护坑内既有桥梁桩基体系。基于湖滨南路隧道下穿广清高速公路桥梁工程中基坑开挖导致既有桥梁桩暴露，影响桥梁整体刚度及造成桥墩沉降的问题，拟采用注浆加固方式进行坑底及桩周加固。需研究注浆加固范围（加固宽度及厚度）变化对桥梁变形的影响。［方法］通过有限元软件MidasGTS进行三维建模，对比不同注浆加固范围下桥梁墩顶位移及桩身轴力分布情况，分析桩周注浆加固宽度和注浆加固厚度变化对桥梁变形的影响及对桩承载力的提高效果。结合数值计算结果及变形控制需求，制定施工加固方案，并对隧道施工过程中墩台沉降现场进行监测。［结果及结论］桩周注浆加固可有效补偿摩擦桩侧摩阻力损失，提高加固区段荷载传递效率，从而更好地分担上部结构荷载；增加桩周加固厚度可有效改善墩顶沉降及邻墩差异沉降。隧道注浆加固施工现场监测结果表明，桥梁沉降变形及差异沉降均满足控制需求。
Abstracts:
［Objective］ When constructing a new tunnel under-passing bridge with open-excavation method, it is crucial to protect the existing pile foundation system within the excavation pit. In the project of South Hubin Road Tunnel under-passing Guangqing Highway Bridge, the foundation pit excavation leads to the exposure of existing bridge piles, affecting the bridge overall stiffness and causing pier settlement. Grouting reinforcement is proposed to stabilize the pit bottom and the pile surrounding. It is aimed to investigate the impact of variation in the grouting reinforcement range (thickness and width) on bridge deformation. ［Method］ Using finite element software Midas GTS for three-dimensional modeling, the bridge pier top displacement and the axial force distribution along the pile shafts are compared under different grouting reinforcement ranges. The impact of changes in grouting reinforcement width and thickness around the piles on bridge deformation, and the effect of improving pile bearing capacity are analyzed. Based on numerical calculation results and deformation control requirements, a construction reinforcement plan is formulated, and the pier abutment settlement is monitored on-site during tunnel construction. ［Result & Conclusion］ Grouting reinforcement around the piles can effectively compensate for the loss of friction pile side friction resistance, improving the load transfer efficiency in the reinforced section and better distributing the load from the superstructure. Increasing the thickness of reinforcement around the piles can significantly improve pier top settlement and differential settlement between adjacent piers. On-site monitoring of tunnel grouting reinforcement construction shows that both bridge settlement deformation and differential settlement meet the control requirements.
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