土岩复合地层地铁车站深基坑锚索预应力损失规律及变形控制研究
孙超1辛庆飞1孙志成2吴宇飞2周浩1徐东明2杨恩泽1
Prestress Loss Law of Anchor Cables and Deformation Control for Metro Station Deep Foundation Pit in Soil-rock Composite Strata
SUN Chao1XIN Qingfei1SUN Zhicheng2WU Yufei2ZHOU Hao1XU Dongming2YANG Enze1
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作者信息:1.中铁四局集团有限公司， 230023， 合肥
2.中国矿业大学(北京)力学与建筑工程学院， 100083， 北京
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Affiliation:1.China Railway Fourth Bureau Group Co., Ltd., 230023, Hefei, China
2.School of Mechanics and Civil Engineering, China University of Mining and Technology, 100083, Beijing, China
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关键词:
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Key words:
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DOI:10.16037/j.1007-869x.20230632
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中图分类号/CLCN:TU753
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栏目/Col:土建工程
摘要:
［目的］为控制土岩复合地层地铁车站深基坑施工风险，应分析施工过程中的锚索受力与基坑变形特性，据此制定控制措施，并实施现场效果验证。［方法］以青岛地铁某在建车站深基坑为例，采用无损检测方法获取锚索预应力短期与长期演化规律；通过FLAC3D软件建立三维基坑-地层模型，分析锚索预应力损失工况下桩体位移与塑性区分布特征；基于桩体位移和钢支撑轴力数据对支护措施的合理性进行验证。［结果及结论］锚索一次张拉合格率达75%以上，5 d后预应力降低值超过锁定值的10%，短期预应力损失值较高。当锚索预应力损失发生后，基坑开挖结束的水平位移是其设计值的2.5倍，最大水平位移为35.4 mm，与现场监测结果保持一致；在锚索低预应力条件下，基坑两侧塑性区分布广，面积大，易发生围岩变形。布设的钢支撑分担了主动土压力，改变了桩体的水平位移分布；布设的钢支撑发挥效用后，钢支撑轴力先上升，随后逐渐降低，最终趋于稳定。采用增设钢支撑的加强措施有效控制了围岩变形。
Abstracts:
［Objective］ To control construction risks associated with deep metro station foundation pit in soil-rock composite strata, it is essential to analyze the stress characteristics of anchor cables and excavation-induced deformation during construction, formulate appropriate control measures accordingly, and verify their effectiveness on-site. ［Method］ Taking the deep foundation pit project construction at a metro station in Qingdao as a case study, non-destructive testing methods are employed to obtain the short- and long-term evolution law of anchor cable prestress. A 3D foundation pit–stratum model is developed using FLAC3D software to analyze the displacement of the retaining piles and the distribution characteristics of plastic zones under prestress loss conditions. The rationality of the support measures is verified based on pile displacement and steel strut axile force. ［Result & Conclusion］ Non-destructive testing results show that over 75% of the anchor cables passed the initial tensioning acceptance criteria. However, within 5 days, the prestress loss exceeded 10% of the lock-in value, indicating a relatively high level of short-term prestress loss. After the occurrence of prestress loss, the final horizontal displacement of the excavation is 2.5 times of the design value, with a maximum displacement of 35.4 mm, consistent with field monitoring results. Under conditions of low anchor cable prestress, wide and extensive plastic zones developed on both sides of the foundation pit, increasing the likelihood of the surrounding rock deformation. The installed steel struts shared part of the active earth pressure and altered the horizontal displacement distribution of the retaining piles. Following their deployment, the steel strut axile force initially increased, then gradually decreased, and eventually stabilized. The reinforcement measures of adding steel struts effectively controlled the deformation of the surrounding rock.
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