大间距桩筏基础地震响应离心模型试验研究

杨敏; 杨军

doi:10.11779/CJGE201612006

大间距桩筏基础地震响应离心模型试验研究 English Version

杨敏^{1, 2},
杨军^1,2, ,

1. 同济大学岩土及地下工程教育部重点实验室,上海 200092;
2. 同济大学地下建筑与工程系,上海 200092

基金项目: 国家自然科学基金项目（41372274）

详细信息

作者简介:
杨敏(1960- ),男,工学博士,教授,博士生导师,主要研究方向为桩基础和基坑工程。E-mail: yangmin@tongji.edu.cn。

通讯作者:
杨军，E-mail：yangjun851113@163.com

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出版历程
- 收稿日期: 2016-02-28
- 发布日期: 2016-12-24

Centrifuge tests on seismic response of piled raft foundation with large spacing

YANG Min^{1, 2},
YANG Jun^1,2, ,

1. Key Laboratory of Geotechnical and Underground Engineering of the Ministry of Education, Tongji University, Shanghai 200092, China;
2. Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China

摘要

摘要: 针对饱和软土地基中大间距摩擦型桩筏基础抗震问题,采用离心振动台开展了桩筏基础地震响应的试验研究。为模拟实际软土场地浅部超固结黏土和深部正常固结黏土的地层特征,试验在高岭土土样表面预铺砂层,然后在50g离心加速度下进行固结。上部结构简化为质点和杆构件,基础形式包括桩头刚接和桩头自由2种类型的大间距桩筏基础模型。试验分析了模型的加速度和位移、土层内部孔隙水压力以及桩身应变等响应。试验结果表明：在软土场地自振频率范围内,结构-基础-地基三者相互作用十分明显,基础与结构加速度放大系数高于其它频率范围;桩头刚接与桩头自由的基础在地震时均产生了较周围地表土体更大的竖向沉降,但震后较长时间内基础与地表沉降速率基本一致;地震结束时,桩头刚接的上部结构侧向位移与基础倾斜值均较桩头自由时减少一半以上,但上部结构加速度放大作用更加明显;桩筏基础承载能力因土体软化行为有所降低,震后部分上部荷载由群桩转移到筏板,但桩筏荷载分担比例总体变化不大。试验揭示了软土震陷时桩基的变形控制机理,为软土地基减沉桩基础的抗震设计提供参考。
- 桩筏基础 /
- 软土 /
- 震陷 /
- 减沉桩 /
- 地震响应 /
- 离心试验 /
- 荷载分担比
Abstract: Centrifuge tests are performed to study the seismic response of piled raft foundation with large spacing in saturated soft clay. By laying sand on clay surface before centrifuge consolidation under 50g, the soil layer with upper over-consolidated clay and lower normally-consolidated clay is simulated. Structural models are simplified to mass points and members. Two foundation types of connected and non-connected piled rafts are considered in tests. The responses of earthquake acceleration, displacements, pore water pressures and pile strains are investigated. The test results show that in the natural vibration frequency range of soft clay ground, the interaction of superstructure-foundation-soil is very remarkable, and the acceleration amplification factors of structure and foundation are higher than those in other frequency ranges. The earthquake induced instant settlements of the connected and non-connected piled rafts are larger than those of the surrounding ground, but a long time after the earthquake the settlement velocities of foundation and ground are almost the same. At the end of the earthquake, more than half of lateral displacement of superstructure and foundation inclination of the connected piled raft are reduced compared with those of the non-connected piled raft, but with higher acceleration amplification effects of superstructure. After the earthquake some loads transfer from pile group to raft on account of soil degradation and loss of bearing capacity of piled raft. However, there are generally few changes of load sharing ratio between piles and raft. The research has revealed the deformation control mechanisms of pile foundation under seismic subsidence in soft clay, and it may provide evidence for the design of settlement-reducing piles.
- piled raft foundation /
- soft clay /
- seismic subsidence /
- settlement-reducing pile /
- seismic response /
- centrifuge test /
- load shearing ratio

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参考文献(15)

[1]	DGJ 08—11—2010上海市地基基础设计规范[S]. 2010. (DGJ 08—11—2010 Foundation design code of Shanghai[S]. 2010. (in Chinese))
[2]	JGJ94—2008 建筑桩基技术规范[S]. 2008. (JGJ 94—2008 Technical code for building pile foundations[S]. 2008. (in Chinese))
[3]	YANG M. Study on reducing-settlement pile foundation based on controlling settlement principle[J]. Chinese Journal of Geotechnical Engineering, 2000, 22(4): 481-486.
[4]	宰金珉. 塑性支承桩——卸荷减沉桩的概念及其工程应用[J]. 岩土工程学报, 2001, 23(3): 273-278. (ZAI Jin-min. Concept of plastically bearing pile and its practical application[J]. Chinese Journal of Geotechnical Engineering, 2001, 23(3): 273-278. (in Chinese))
[5]	POULOS H G. Piled raft foundations: design and applications [J]. Géotechnique, 2001, 51(2): 95-113.
[6]	REUL O, RANDOLPH M F. Piled rafts in overconsolidated clay: comparison of in situ measurements and numerical analyses[J]. Géotechnique, 2003, 53(3): 301-315.
[7]	HORIKOSHI K, MATSUMOTO T, HASHIZUME Y, et al. Performance of piled raft foundations subjected to dynamic loading[J]. International Journal of Physical Modelling in Geotechnics, 2003, 3(2): 51-62.
[8]	MATSUMOTO T, FUKUMURA K, HORIKOSHI K, et al. Shaking table tests on model piled rafts in sand considering influence of superstructures[J]. International Journal of Physical Modelling in Geotechnics, 2004, 4(3): 21-38.
[9]	NAKAIA S, KATOA H, ISHIDAA R, et al. Load bearing mechanism of piled raft foundation during earthquake[C]// Proceedings of 3rd UJNR Workshop on Soil-Structure Interaction, March, 2004: 29-30.
[10]	BANERJEE S, GOH S H, LEE F H. Earthquake-induced bending moment in fixed-head piles in soft clay[J]. Géotechnique, 2014, 64(6): 431-446.
[11]	马亢, 许强, 李庶林, 等. 高低承台桩基地震行为差异研究[J]. 岩石力学与工程学报, 2015, 34(6): 1250-1258. (MA Kang, XU Qiang, LI Shu-lin, et al. Difference of seismic behavior of high and low caps of pile foundations[J]. Chinese Journal of Rock Mechanics and Engineering, 2015, 34(6): 1250-1258. (in Chinese))
[12]	DGJ 08—9—2013 上海市建筑抗震设计规程[S]. 2013. (DGJ 08—9—2013 Code for seismic design of buildings of Shanghai[S]. 2013. (in Chinese))
[13]	钟锐, 黄茂松. 沉箱加桩复合基础地震响应离心试验[J]. 岩土力学, 2014, 35(2): 380-388. (ZHONG Rui, HUANG Mao-song. Centrifuge tests for seismic response of caisson-pile composite foundation[J]. Rock and Soil Mechanics, 2014, 35(2): 380-388. (in Chinese))
[14]	YAMADA T, YAMASHITA K, KAKURAI M, et al. Long-term behaviour of tall building on raft foundation constructed by top-down method[C]// Proceedings of the 5th International Conference on Deep Foundation Practice. Singapore, 2001: 411-417.
[15]	YAMASHITA K, HAMADA J, WAKAI S, TANIKAWA T. Settlement and load sharing behavior of piled raft foundations based on long-term monitoring[J]. Takenaka Technical Research Report, 2014, 70: 29-40.