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| Field investigation on heave behavior of pile groups induced by deep excavation |
| LI Jian1, QIN Shanglin1, LI Shichang2, YU Fei1*, DAI Zhangjun1 |
(1. State Key Laboratory of Geomechanics and Geotechnical Engineering Safety, Institute of Rock and Soil Mechanics,
Chinese Academy of Sciences, Wuhan, Hubei 430071, China; 2. School of Civil Engineering,
Henan Polytechnic University, Jiaozuo, Henan 454003, China) |
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Abstract To investigate the heave deformation law of group pile foundations under deep excavation conditions, this study is conducted based on the background of an actual high-speed railway bridge project. A full-scale field model test of group pile foundations with dimensions completely consistent with the engineering prototype is carried out. Through precise monitoring and systematic analysis, the deformation characteristics, force transmission laws, and key influencing factors of group pile foundations under deep excavation conditions are thoroughly revealed. The test results show that soil unloading rebound is the core inducement of heave deformation of pile foundations under deep excavation. When the excavation depth of the soil around the pile foundations reaches 9.5 m, the maximum heave deformation at the pile top is only about 1mm, and the overall deformation amplitude is at a relatively small level. Under symmetric excavation conditions, the horizontal displacement of the pile top shows no significant change, and the stress state remains stable. However, when the asymmetric excavation thickness is 3.5m, the horizontal displacement of the pile top slightly shifts towards the soil-unloading side, with the displacement amplitude ranging between 0.2–0.3 mm and the deformation influence range being limited. The study confirms that the main reason for the small heave deformation of group pile foundations is the limited amplitude of soil unloading rebound deformation. This research achievement can provide important references for the deformation prediction and design optimization of pile foundations in major projects such as high-speed railway bridges under deep excavation conditions. It is clarified that in relevant deformation calculations or numerical simulations, it is crucial to reasonably select the rebound modulus parameter based on the current stress level and unloading state of the unloaded soil, which is the key to ensuring the accuracy of calculation results.
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