既有建筑地下增层改造桩基承载特性离心模型试验

doi:10.3724/1000-6915.jrme.2024.0362

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摘要为了厘清既有建筑地下增层改造对既有桩基影响，采用土工离心模型试验模拟在砂土地层下既有建筑地下增层开挖地下室工况。离心模型中考虑桩顶作用的既有荷载，研究增层开挖对既有桩基承载特性的影响，试验结果为地下增层改造过程中对桩基承载力评估及再设计提供了借鉴和参考。结果表明：(1) 考虑桩顶既有荷载影响，原型状态下桩顶荷载在0.94倍承载力特征值持载约9 d再进行载荷试验，比未考虑既有荷载持载的试验桩承载力提高约6%，在既有桩基再设计中可适当考虑桩顶既有荷载引起桩侧、桩端土压密及承载力提高；(2) 对于长20 m的摩擦型桩在既有载荷作用下，当开挖深度为桩长20%，40%时承载力损失率分别为11.5%和37.9%；当开挖深度为桩长40%时，桩端阻力分担比大幅增加，桩由端承摩擦桩变为摩擦端承桩，过程中桩身轴力增加、沉降大幅增大，实际工程中应对桩身抗压强度验算，并规避沉降增大带来的风险；(3) 当地下开挖桩长40%时桩侧摩阻力减小，这可能与侧阻软化有关，也可能与开挖卸荷桩周土竖向应力减小有关，具体原因尚需进一步验证；在对既有桩基承载力估算中宜考虑这一影响。

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	张敬一1
	马兵2

关键词 ：桩基础, 地下开挖, 离心模型试验, 承载特性, 桩基, 既有建筑

Abstract：In order to clarify the impact of basement-addition on existing pile foundations，a geotechnical centrifugal was carried out to simulate the basement-addition excavations in sandy strata. Considering existing working load at pile head in the geotechnical centrifugal，the effect of bearing characteristics of existing pile foundation during basement-addition excavations was studied. A reference for the assessment and redesign of the pile foundation for basement-addition construction of the existing building is provided. The results show that：(1) Considering the influence of the existing load，the load test is carried out after the load at pile head is held for about 9 days with 0.94 times the bearing capacity characteristic value at the prototype state. The bearing capacity of the test pile is about 6% higher than that of the test pile without considering the existing working load. In the redesign of existing pile foundations，duo to soil compaction at pile side and pile end caused by existing load at pile head，the improvement of bearing capacity can be properly considered. (2) For a friction pile with length of 20 m under the existing load，the bearing capacity loss rate is 11.5% and 37.9% when the excavation depth is 20% and 40% of the pile length，respectively. When the excavation depth is 40% of the pile length，the pile changes from friction end-bearing pile to friction end-bearing pile，and the axial force and the settlement of the pile increase greatly during the process. In practical engineering，the compressive strength of pile should be checked and the risk caused by the increase of settlement should be avoided. (3) When the excavation depth is 40% of the pile length，the side friction resistance decreases. This may be related to the softening of the side resistance，or the reduction of vertical soil stress around the pile caused by excavation. The specific reason needs further verification. In the estimation of bearing capacity of existing pile foundation，this effect should be considered.

Key words： pile foundation underground excavation centrifugal model test bearing characteristics pile foundation existing building

引用本文:

张敬一1，马兵2. 既有建筑地下增层改造桩基承载特性离心模型试验[J]. 岩石力学与工程学报, 2025, 44(S1): 219-229.
ZHANG Jingyi1，MA Bing2. Geotechnical centrifugal model test on bearing characteristics of existing building pile foundations under excavation conditions. , 2025, 44(S1): 219-229.

链接本文:

https://rockmech.whrsm.ac.cn/CN/10.3724/1000-6915.jrme.2024.0362 或 https://rockmech.whrsm.ac.cn/CN/Y2025/V44/IS1/219

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