Centrifuge Test on Bearing Capacity of Energy Piles in Sand Affected by Thermal－Cool Cycles
-
摘要:
为研究砂土中能源桩在热冷循环温度作用下的承载能力，开展不同密实度奉浦砂土中细长能源桩的离心机模型试验. 试验中进行20次热—冷温度循环作用，获得能源桩轴力、侧摩阻力、单桩承载力等的变化规律，并进行对比研究. 试验结果表明：随着温度循环次数增加，能源桩桩身轴力均逐渐衰减并趋于稳定，且中密砂中能源桩最大轴力衰减值远高于密砂中能源桩；在热冷温度循环过程中，中密砂中能源桩桩身中下部存在中性点，在冷循环过程中中性点以上存在正的附加侧摩阻力，下部存在负的附加侧摩阻力，而在热循环过程中中性点以上存在负的附加侧摩阻力，下部存在正的附加侧摩阻力；密砂对能源桩下部存在明显的约束作用，使其在冷循环过程中全桩身相对桩周土体存在向下的位移趋势，产生全桩身正的附加侧摩阻力，而热循环过程中产生负的附加侧摩阻力；长期循环荷载作用使得能源桩的桩基承载力发生折减，与相应原型桩相比，埋设于中密砂和密砂中的能源桩承载力分别减小了7.3%和15.6%；密砂中的原型桩及能源桩承载力均高于中密砂中原型桩约11%；当实际工程中能源桩处于不同密实度的砂土层中时，需采取合理的措施，以满足能源桩的承载要求.
Abstract:To study the bearing capacity of energy piles in sand affected by thermal－cool cycles, a centrifuge model test on slender energy piles buried in Fengpu sand with different compactions was carried out. The change rules of the axial force, side friction, and individual bearing capacity of energy piles were obtained and compared under 20 thermal－cool cycles in the test. The test results show that the axial force of the energy pile decays gradually and tends to be stable with increasing thermal－cool cycles. The maximum axial force attenuation value of the energy pile buried in the sand with medium compaction is much larger than that buried in the dense sand. During thermal－cool cycles, for energy piles buried in the sand with medium compaction, a neutral point is located at the bottom half of the pile. Positive additional side friction is generated above the neutral point during cool cycles, and negative additional side friction is generated underneath the neutral point. Oppositely, during thermal cycles, negative additional side friction appears above the neutral point, and positive additional side friction is underneath the neutral point. The dense sand has an obvious constraint effect on the lower part of energy piles. Positive additional side friction is distributed along the pile during cool cycles because the pile moves downward relative to the surrounding soil. During thermal cycles, the additional side friction is negative. The bearing capacity of the energy piles will be reduced because of the long-term temperature cycles. The bearing capacity of the energy piles buried in the dense sand and sand with medium compaction is reduced by 7.3% and 15.6%, compared with the prototype pile. The bearing capacity of the prototype pile and energy piles buried in the dense sand is 11% larger than that of the prototype pile buried in the sand with medium compaction. Therefore, reasonable measures should be taken to meet the bearing requirements of energy piles when buried in sandy layers with different compactions in actual engineering.
-
Key words:
- energy pile /
- centrifuge test /
- bearing capacity /
- temperature cycle /
- compaction
-
图 6 不同循环次数下能源桩桩身轴力衰减曲线
Figure 6. Axial force attenuation curves of energy pile under different cycles times
图 7 末次热循环过程不同温度下桩身轴力
Figure 7. Axial force of energy pile at different temperatures during last thermal cycle
图 8 末次热循环过程中不同温度下桩身附加轴力
Figure 8. Additional axial force of energy pile at different temperatures during last thermal cycle
图 9 末次冷循环过程中不同温度下桩身轴力和附加轴力
Figure 9. Axiad force and additional axial force of energy pile at different temperatures during last cool cycle
图 10 循环温度荷载作用下桩侧摩阻力变化
Figure 10. Side friction variation of energy pile with temperature cycle
图 11 末次热循环过程中不同温度下桩身附加侧摩阻力
Figure 11. Additional side friction of energy pile at different temperatures during last thermal cycle
图 12 末次冷循环过程中不同温度下桩身附加侧摩阻力
Figure 12. Additional side friction of energy pile at different temperatures during last cool cycle
-
[1] 鲍旭明. 地源热泵国内外发展状况对比[J]. 山西建筑,2016,42(20): 126-128. doi: 10.3969/j.issn.1009-6825.2016.20.070BAO Xuming. The development comparison of ground source heat pump at home and abroad[J]. Shanxi Architecture, 2016, 42(20): 126-128. doi: 10.3969/j.issn.1009-6825.2016.20.070 [2] BRANDL H. Energy piles and diaphragm walls for heat transfer form and into the ground[C]//Procssding of the 3-h international Geotechnical Seminar on Deep Foundations on Bored and Auger Piles. Vienna: CRC Press, 1998: 38-60. [3] LALOUI L, NUTH M, VULLIET L. Experimental and numerical investigations of the behaviour of a heat exchanger pile[J]. International Journal for Numerical and Analytical Methods in Geomechanics, 2006, 30(8): 763-781. [4] LALOUI L. In situ testing of a heat exchanger pile[M]//Geo-Frontiers 2011: Advances in Geotechnical Engineering. Dallas: ASCE, 2011: 410-419. [5] BOURNE-WEBB P J, AMATYA B, SOGA K, et al. Energy pile test at Lambeth College, London: geotechnical and thermodynamic aspects of pile response to heat cycles[J]. Géotechnique, 2009, 59(3): 237-248. [6] FAIZAL M, BOUAZZA A, HABERFIELD C, et al. Axial and radial thermal responses of a field-scale energy pile under monotonic and cyclic temperature changes[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2018, 144(10): 4018072.1-4018072.14. [7] KALANTIDOU A, TANG A M, PEREIRA J M, et al. Preliminary study on the mechanical behaviour of heat exchanger pile in physical model[J]. Géotechnique, 2012, 62(11): 1047-1051. [8] YAZDANI S, HELWANY S, OLGUN G. Investigation of thermal loading effects on shaft resistance of energy pile using laboratory-scale model[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2019, 145(9): 04019043.1-04019043.12. [9] NG C W W, SHI C, GUNAWAN A, et al. Centrifuge modelling of energy piles subjected to heating and cooling cycles in clay[J]. Géotechnique Letters, 2014, 4(4): 310-316. [10] NG C W W, SHI C, GUNAWAN A, et al. Centrifuge modelling of heating effects on energy pile performance in saturated sand[J]. Canadian Geotechnical Journal, 2015, 52(8): 1045-1057. doi: 10.1139/cgj-2014-0301 [11] GOODE J C I. Centrifuge Modeling of the Thermo-Mechanical Response of Energy Foundations[D]. Boulder: University of Colorado at Boulder, 2013. [12] 路宏伟,蒋刚,王昊,等. 摩擦型能源桩荷载-温度现场联合测试与承载性状分析[J]. 岩土工程学报,2017,39(2): 334-342 doi: 10.11779/CJGE201702018LU Hongwei, JIANG Gang, WANG Hao. et al. In-situ tests and thermo-mechanical bearing characteristics of friction geothermal energy piles[J]. Chinese Journal of Geotechnical Engineering, 2017, 39(2): 334-342. doi: 10.11779/CJGE201702018 [13] FANG J C, KONG G Q, YANG Q. Group performance of energy piles under cyclic and variable thermal loading[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2022, 148(8): 04022060.1-04022060.10 [14] LEI G H, NG C W W, RIGBY D B. Stress and displacement around an elastic artificial rectangular hole[J]. Journal of Engineering Mechanics, 2001, 127(9): 880-890. doi: 10.1061/(ASCE)0733-9399(2001)127:9(880) [15] CHIU C F, NG C W W. A state-dependent elasto-plastic model for saturated and unsaturated soils[J]. Géotechnique, 2003, 53(9): 809-829. [16] WU D, LIU H L, KONG G Q, et al. Displacement response of an energy pile in saturated clay[J]. Proceedings of the Institution of Civil Engineers- Geotechnical Engineering, 2018, 171(4): 285-294. doi: 10.1680/jgeen.17.00152 [17] 郭易木,钟鑫,刘松玉,等. 自由约束条件下分层地基中PHC能源桩热力响应原型试验研究[J]. 岩石力学与工程学报,2019,38(3): 582-590.GUO Yimu, ZHONG Xin, LIU Songyu, et al. Prototype experimental investigation on the thermo-mechanical behaviors of free constrained full-scale PHC energy piles in multi-layer strata[J]. Chinese Journal of Rock Mechanics and Engineering, 2019, 38(3): 582-590. [18] GHAAOWD I, MCCARTNEY J S. Centrifuge modeling methodology for energy pile pullout from saturated soft clay[J]. Geotechnical Testing Journal., 2022, 45(2): 332-354 . doi: 10.1520/GTJ20210062 [19] NG C W W, FARIVAR A, GOMAA S M M H, et al. Performance of elevated energy pile groups with different pile spacing in clay subjected to cyclic non-symmetrical thermal loading[J]. Renewable Energy, 2021, 172: 998-1012. doi: 10.1016/j.renene.2021.03.108 [20] ZHAO R, LEUNG A K, VITALI D, et al. Small-scale modeling of thermomechanical behavior of reinforced concrete energy piles in soil[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2020, 146(4): 04020011.1-04020011.10. [21] 李伟伟,钱建固,黄茂松,等. 等截面抗拔桩承载变形特性离心模型试验及数值模拟[J]. 岩土工程学报,2010,32(增2): 17-20.LI Weiwei, QIAN Jiangu, HUANG Maosong, et al. Centrifugal model tests and numerical simulation on bearing capacity and deformation of uplift piles with uniform sections[J]. Chinese Journal of Geotechnical Engineering, 2010, 32(S2): 17-20. [22] TAYLOR R N. Geotechnical centrifuge technology[M]. London: Blackie Academic & Professional, 1995: 27-42. [23] 蒋刚,李仁飞,王昊,等. 摩擦型能源桩热–力耦合全过程承载性能分析[J]. 岩石力学与工程学报,2019,38(12): 2525-2534.JIANG Gang, LI Renfei, WANG Hao, et al. Numerical analysis of the bearing capacity of floating energy piles during the full process of thermal-mechanical coupling[J]. Chinese Journal of Rock Mechanics and Engineering, 2019, 38(12): 2525-2534. [24] 常虹,朱万里,王琰,等. 温度荷载作用下能源桩的力学特性[J]. 中国科技论文,2022,17(6): 660-666. doi: 10.3969/j.issn.2095-2783.2022.06.011CHANG Hong, ZHU Wanli, WANG Yan, et al. Mechanical properties of energy pile under temperature load[J]. China Sciencepaper, 2022, 17(6): 660-666. doi: 10.3969/j.issn.2095-2783.2022.06.011 [25] 中华人民共和国住房和城乡建设部. 建筑桩基技术规范:JGJ 94—2008[S]. 北京:中国建筑工业出版社,2008. [26] 汤炀,刘干斌,郑明飞,等. 饱和粉土中相变能源桩力响应模型试验研究[J]. 岩土力学,2022,43(增2): 282-290.TANG Yang, LIU Ganbin, ZHENG Mingfei, et al. Model test on thermal response of phase change pile in saturated silt ground[J]. Rock and Soil Mechanics, 2022, 43(S2): 282-290. [27] 中国建筑科学研究院. 建筑基桩检测技术规范:JGJ 106—2014[S]. 北京:中国建筑工业出版社,2003. -
下载:
点击查看大图
计量
- 文章访问数: 113
- HTML全文浏览量: 60
- PDF下载量: 8
- 被引次数: 0