XCC桩单桩荷载传递特性的离心机模型试验研究
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摘要
XCC桩是根据等截面异形周边扩大原理改造而来的异形截面桩,通过改变截面形状来改变桩土荷载传递机理。为了得到真实应力状态下XCC桩-土荷载传递机理,开展了单一均质Toyoura干砂中XCC单桩与等截面面积的圆形单桩的离心机对比模型试验,得到了真实应力状态下XCC异形桩的极限承载力、轴力和侧摩阻力分布特性。结果表明,以10%桩径沉降作为承载力判别标准时,XCC单桩极限承载力较圆形单桩提高了约30%,其主要来源于桩侧摩阻力的提高; XCC桩侧摩擦力稍大于圆形桩,其总侧摩阻力至少是等截面面积圆形桩的1.65倍,侧摩阻力的提高部分来源于截面周长的增大,其余来源于XCC单桩的"异形效应"。
XCC pile is a special-shaped cross-sectional pile,which is developed according to the principle of expanding the cross-sectional perimeter with special cross-sections. The load transfer mechanism between pile and soil is changed due to its unique cross-sectional shape. In order to understand the unique load transfer mechanism of XCC pile-soil system under actual stress state,comparative centrifugal modeling tests on a XCC pile and a circular pile with an identical cross-sectional area in homogeneous Toyoura sand were carried out. The ultimate bearing capacity and distributions of axial load and skin friction were measured and analyzed. It is found that,when the settlement of 10% pile diameter is used as the criterion, the ultimate bearing capacity of the XCC pile is approximately 1.3 times that of the circular pile. The more bearing capacity of XCC pile is attributed to its side resistance. Although the skin friction on the XCC pile is slightly larger than that on the circular pile,the total side resistance of the XCC pile is at least 1.65 times that of the circular pile. Part of the increment in side resistance of XCC pile is contributed by the cross-sectional perimeter and the remaindering is contributed by the "geometrical effects".
XCC pile is a special-shaped cross-sectional pile,which is developed according to the principle of expanding the cross-sectional perimeter with special cross-sections. The load transfer mechanism between pile and soil is changed due to its unique cross-sectional shape. In order to understand the unique load transfer mechanism of XCC pile-soil system under actual stress state,comparative centrifugal modeling tests on a XCC pile and a circular pile with an identical cross-sectional area in homogeneous Toyoura sand were carried out. The ultimate bearing capacity and distributions of axial load and skin friction were measured and analyzed. It is found that,when the settlement of 10% pile diameter is used as the criterion, the ultimate bearing capacity of the XCC pile is approximately 1.3 times that of the circular pile. The more bearing capacity of XCC pile is attributed to its side resistance. Although the skin friction on the XCC pile is slightly larger than that on the circular pile,the total side resistance of the XCC pile is at least 1.65 times that of the circular pile. Part of the increment in side resistance of XCC pile is contributed by the cross-sectional perimeter and the remaindering is contributed by the "geometrical effects".
引文
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[23]Ng C W W,Yau T L Y,Li J H M,et al.New failure load criterion for large diameter bored piles in weathered geomaterials[J].Journal of Geotechnical and Geoenvironmental Engineering,2001,127(6):488-498.
[24]Meyerhof G G.Bearing capacity and settlement of pile foundations[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,1976,102(3):197-227.
[2]LüY,Liu H,Ng C W W,et al.Three-dimensional numerical analysis of the stress transfer mechanism of XCC piled raft foundations[J].Computer and Geotechnics,2014,55:365-377.
[3]张敏霞.现浇X形桩单桩竖向承载性状足尺模型试验与计算方法研究[D].南京:河海大学,2011.(Zhang Minxia.Full-scale model test and calculation method study on the bearing behavior of cast-in-situ X-section pile[D].Nanjing:Hohai University,2011.(in Chinese))
[4]吕亚茹,刘汉龙,王新泉,等.现浇X形桩产生地基附加应力的修正Geddes应力解[J].岩石力学与工程学报,2013,32(2):349-362.(LüYaru,Liu Hanlong,Wang Xinquan,et al.A modified Geddes’s solution for foundation additional stress induced by X-section pile[J].Chinese Journal of Rock Mechanics and Engineering,2013,32(2):349-362.(in Chinese))
[5]LüY,Liu H,Ng C W W,et al.A modified analytical solution of soil stress distribution for XCC pile foundations[J].Acta Geotechnica,2014,9(3):529-546.
[6]王智强.现浇X形桩竖向承载力学特性研究[D].南京:河海大学,2009.(Wang Zhiqiang.Study on the vertical bearing characteristics of Cast-in-place X-section concrete pile[D].Nanjing:Hohai University,2009.(in Chinese))
[7]王智强,刘汉龙,张敏霞,等.现浇X形桩竖向承载特性足尺模型试验研究[J].岩土工程学报,2010,32(6):903-907.(Wang Zhiqiang,Liu Hanlong,Zhang Minxia,et al.Full scale model tests on vertical bearing characteristics of cast-in-place X-section piles[J].Chinese Journal of Geotechnical Engineering,2010,32(6):903-907.(in Chinese))
[8]张敏霞,刘汉龙,丁选明,等.现浇X形混凝土桩与圆形桩承载性状对比试验研究[J].岩土工程学报,2011,33(9):1469-1476.(Zhang Minxia,Liu Hanlong,Ding Xuanming,et al.Comparative tests on bearing capacity of cast-in-situ X-shaped concrete piles and circular pile[J].Chinese Journal of Geotechnical Engineering,2011,33(9):1469-1476.(in Chinese))
[9]张敏霞,丁选明,陈育民.现浇X形混凝土桩竖向承载特性试验及其极限承载力预测[J].煤炭学报,2011,36(2):267-272.(Zhang Minxia,Ding Xuanming,Chen Yumin.Test on vertical behavior of cast-in-situ X-shaped concrete pile and its ultimate bearing capacity prediction[J].Journal of China Coal Society,2011,36(2):267-272.(in Chinese))
[10]张敏霞,刘汉龙,丁选明.加固软土路基的现浇X形混凝土桩力学特性[J].中国公路学报,2011,24(5):11-17.(Zhang Minxia,Liu Hanlong,Ding Xuanming.Mechanical property for cast-in-situ X-shaped concrete pile of reinforced soft roadbed[J].China Journal of Highway and Transport,2011,24(5):11-17.(in Chinese))
[11]雍君.现浇X形混凝土桩抗拔性能研究[D].南京:河海大学,2010.(Yong Jun.Study on anti-pulling property of X-section concrete pile[D].Nanjing:Hohai University,2010.(in Chinese))
[12]雍君,陆晓敏,刘汉龙.X形混凝土桩抗拔特性试验研究[J].岩土力学,2010,31(11):3430-3434.(Yong Jun,Lu Xiaomin,Liu Hanlong.Model test study of anti-pulling property of X-shaped concrete pile[J].Rock and Soil Mechanics,2010,31(11):3430-3434.(in Chinese))
[13]金辉.路堤荷载下现浇X形桩负摩阻力特性试验与数值模拟研究[D].南京:河海大学,2012.(Jin Hui.Field test and numerical analysis on negative skin friction of X-section cast-in-place pile under highway embankment[D].Nanjing:Hohai University,2012.(in Chinese))
[14]刘汉龙,金辉,丁选明,等.现浇X形混凝土桩沉桩挤土效应现场试验研究[J].岩土力学,2012,33(增2):219-228.(Liu Hanlong,Jin Hui,Ding Xuanming,et al.Field test research on squeezing effects of X-section Cast-in-place concrete pile[J].Rock and Soil Mechanics,2012,33(Supp.2):219-228.(in Chinese))
[15]於慧.高速公路拓宽现浇X形桩复合地基加固机理研究[D].南京:河海大学,2013.(Yu Hui.Study on reinforcement mechanism of Cast-in-place X-section concrete pile composite foundation under widening embankment[D].Nan Jing:Hohai University:,2013.(in Chinese))
[16]Ishihara K.Liquefaction and flow failure during earthquakes[J].Géotechnique,1993,43(3):351-451.
[17]Bolton M D.The strength and dilatancy of sands[J].Géotechnique,1986,36(1):65-78.
[18]Hicher P Y,Chang C S.Anisotropic nonlinear elastic model for particulate materials[J].Journal of Geotechnical and Geoenvironmental Engineering,2006,132(8):1052-1061.
[19]Jáky J.New theory of earth pressure[A]//Proceedings of the 2nd ICSMFE[C].Rotterdam,Hollandia,1948.
[20]Ng C W W.The state-of-art centrifuge modelling of geotechnical problems at HKUST[J].Journal of Zhejiang University-Science A(Applied Physics&Engineering),2014,15(1):1-20.
[21]O’Neil M W,Reese L C.Drilled shaft:construction procedures and design methods[J].Tunnelling&Underground Space Technology,2010,5(1-2):156-157.
[22]Russo G.Experimental investigations and analysis on different pile load testing procedures[J].Acta Getechnica,2013,8(1):17-31.
[23]Ng C W W,Yau T L Y,Li J H M,et al.New failure load criterion for large diameter bored piles in weathered geomaterials[J].Journal of Geotechnical and Geoenvironmental Engineering,2001,127(6):488-498.
[24]Meyerhof G G.Bearing capacity and settlement of pile foundations[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,1976,102(3):197-227.