砂土中抗拔斜桩性状模型试验研究
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摘要
为研究抗拔斜桩的承载变形性状及荷载传递机制,在中密干砂中进行10根单斜桩抗拔试验,研究桩身倾角、长径比对斜桩抗拔承载力的影响,分析斜桩桩身轴力、弯矩、剪力及桩侧摩阻力的分布特征,比较斜桩与相应直桩抗拔承载变形性状的差异。结果表明:斜桩的抗拔承载力并不总是大于相应直桩,其大小受到桩身倾角及长径比的重要影响;在上拔荷载作用下,斜桩轴力大于相应直桩轴力,桩身倾角越大,斜桩轴力超过直桩轴力越多;抗拔斜桩桩身上部区段截面存在弯矩及剪力,斜桩最大弯矩受到桩身倾角及长径比的影响,斜桩除了在桩顶处存在最大剪力外,桩顶下一定深度处还存在极值剪力;抗拔斜桩桩身上部为负摩阻力,下部为正摩阻力。
In order to reveal the uplift bearing behaviors and load transfer mechanism of vertically loaded batter piles, 10 model tests were conducted for single batter piles embedded in dry medium dense sand. The influence of shaft inclined angle and the ratio of the pile length to shaft diameter(L/D) on the uplift bearing capacity was investigated;and the characteristics of the axial force,the bending moment,the shear force and the average skin friction on pile shaft was analyzed. The difference of the uplift bearing capacity between the batter piles and its vertical counterparts was also studied. Results indicate that the uplift bearing capacity of the batter pile is not always bigger than that of the vertical pile,which notably depends on the shaft inclined angle and the ratio of the L/D. The magnitude of the axial force in batter pile induced by uplift is greater than that in vertical pile,the bigger the inclined angle,the greater the axial force of the batter piles over that of the vertical piles. Both the bending moment and shear force caused by uplifting on the upper segment of batter piles are influenced by the inclined angle and the ratio of L/D. With the exception of a maximum shear force occurring on the pile head for batter pile,an extreme value of shear force will also be caused in the inclined shaft below the pile head. Negative skin friction exists on the upper segment while positive skin friction on the lower segment of the inclined piles.
In order to reveal the uplift bearing behaviors and load transfer mechanism of vertically loaded batter piles, 10 model tests were conducted for single batter piles embedded in dry medium dense sand. The influence of shaft inclined angle and the ratio of the pile length to shaft diameter(L/D) on the uplift bearing capacity was investigated;and the characteristics of the axial force,the bending moment,the shear force and the average skin friction on pile shaft was analyzed. The difference of the uplift bearing capacity between the batter piles and its vertical counterparts was also studied. Results indicate that the uplift bearing capacity of the batter pile is not always bigger than that of the vertical pile,which notably depends on the shaft inclined angle and the ratio of the L/D. The magnitude of the axial force in batter pile induced by uplift is greater than that in vertical pile,the bigger the inclined angle,the greater the axial force of the batter piles over that of the vertical piles. Both the bending moment and shear force caused by uplifting on the upper segment of batter piles are influenced by the inclined angle and the ratio of L/D. With the exception of a maximum shear force occurring on the pile head for batter pile,an extreme value of shear force will also be caused in the inclined shaft below the pile head. Negative skin friction exists on the upper segment while positive skin friction on the lower segment of the inclined piles.
引文
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[8]靳彩,赵瑜,李风兰,等.送电线路铁塔复合式斜桩基础试验研究[J].工业建筑,2001,31(9):45-47.(JIN Cai,ZHAO Yu,LIFenglan,et al.The experimental research on the complex inclined pile foundation for power line tower[J].Industrial Construction,2001,31(9):45-47.(in Chinese))
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[10]MEYERHOF G G.Uplift resistance of inclined anchors and piles[C]//Proceedings of 8th International Conference on Soil Mechanics and Foundation Engineering.[S.l.]:[s.n.],1973:167-172.
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[12]AWAD A,AYOUB A.Ultimate uplift capacity of vertical and inclined piles in cohesionless soil[C]//Proceedings of the 5th International Conference on Soil Mechanics and Foundation Engineering.Budapest:[s.n.],1976:221-227.
[13]AL-SHAKARCHI Y J,FATTAH M Y,KASHAT I K.The behaviour of batter piles under uplift loads[C]//Proceedings of International Conference on Geotechnical Engineering.Sharjah:[s.n.],2004:105-114.
[14]HANNA A M,AFRAM A.Pull-out capacity of single batter piles in sand:Reply[J].Revue Canadienne De Géotechnique,1987,24(3):468-468.
[15]CHATTOPADHYAY B C,PISE P J.Axial uplift capacity of inclined piles[J].Indian Geotechnical Journal,1986,16(3):197-214.
[16]MROUEH H,SHAHROUR I.Numerical analysis of the response of battered piles to inclined pullout loads[J].International Journal for Numerical and Analytical Methods in geomechanics,2009,33(10):1 277-1 288.
[17]BHARDWAJ S,SINGH S K.Ultimate capacity of battered micropiles under oblique pullout loads[J].International Journal of Geotechnical Engineering,2014,9(2):190-200.
[18]中华人民共和国行业标准编写组.JGJ94-2008建筑桩基技术规范[S].北京:中国建筑工业出版社,2008.(The Professional Standards Compilation Group of People’s Republic of China.JGJ94-2008 Technical code for building pile foundations[S].Beijing:China Architecture and Building Press,2008.(in Chinese))
[19]JAMES R G.Some aspects of soil mechanics model testing[C]//Stress-strain Behaviour of Soils,Roscoe Memorial Symp.[S.l.]:[s.n.],1972:417-440.
[2]GEROLYMOS N,GIANNAKOU A,ANASTASOPOULOS L,et al.Evidence of beneficial role of inclined piles:Observations and summary of numerical analyses[J].Bulletin of Earthquake Engineering,2008,6(4):705-722.
[3]徐江,龚维明,张琪,等.大口径钢管斜桩竖向承载特性数值模拟与现场试验研究[J].岩土力学,2017,38(8):2 434-2440.(XUJiang,GONG Weiming,ZHANG Qi,et al.Numerical simulation and field test study on vertical bearing behavior of large diameter steel of inclined piles[J].Rock and Soil Mechanics,2017,38(8):2 434-2 440.(in Chinese))
[4]杨征宇,杨剑,王天慧,等.输电塔基础斜桩非线性p-y曲线[J].河海大学学报:自然科学版,2010,38(1):104-108.(YANGZhengyu,YANG Jian,WANG Tianhui,et al.Nonlinear p-y curve for batter piles in foundation of transmission towers[J].Journal of Hohai University:Natural Science,2010,38(1):104-108.(in Chinese))
[5]魏鉴栋,陈仁朋,陈云敏,等.微型桩抗拔特性原型试验研究[J].工程勘察,2006,8(2):14-19.(WEI Jiandong,CHEN Renpeng,CHENYunmin,et al.Field test on uplift behavior of micropiles[J].Geotechnical Investigation and Surveying,2006,8(2):14-19.(in Chinese))
[6]吕凡任,陈仁朋,陈云敏,等.软土地基上微型桩抗压和抗拔特性试验研究[J].土木工程学报,2005,38(3):99-105.(LV Fanren,CHEN Renpeng,CHEN Yunmin,et al.Field test on compression and uplift behavior of micropiles in soft ground[J].China Civil Engineering Journal,2005,38(3):99-105.(in Chinese))
[7]范书立,陈健云,张俊清.波浪荷载作用下斜向抗拔桩的承载特性分析[J].岩土力学,2012,33(1):301-306.(FAN Shuli,CHENJianyun,ZHANG Junqing.Research on bearing capacity of inclined uplift pile under wave cyclic loading[J].Rock and Soil Mechanics,2012,33(1):301-306.(in Chinese))
[8]靳彩,赵瑜,李风兰,等.送电线路铁塔复合式斜桩基础试验研究[J].工业建筑,2001,31(9):45-47.(JIN Cai,ZHAO Yu,LIFenglan,et al.The experimental research on the complex inclined pile foundation for power line tower[J].Industrial Construction,2001,31(9):45-47.(in Chinese))
[9]NAZIR A,NASR A.Pullout capacity of batter pile in sand[J].Journal of advanced research,2013,4(2):147-154.
[10]MEYERHOF G G.Uplift resistance of inclined anchors and piles[C]//Proceedings of 8th International Conference on Soil Mechanics and Foundation Engineering.[S.l.]:[s.n.],1973:167-172.
[11]AFRAM A.Uplift capacity of battered piles in sand[M.S.Thesis][D].Concordia,Canada:Concordia University,1984.
[12]AWAD A,AYOUB A.Ultimate uplift capacity of vertical and inclined piles in cohesionless soil[C]//Proceedings of the 5th International Conference on Soil Mechanics and Foundation Engineering.Budapest:[s.n.],1976:221-227.
[13]AL-SHAKARCHI Y J,FATTAH M Y,KASHAT I K.The behaviour of batter piles under uplift loads[C]//Proceedings of International Conference on Geotechnical Engineering.Sharjah:[s.n.],2004:105-114.
[14]HANNA A M,AFRAM A.Pull-out capacity of single batter piles in sand:Reply[J].Revue Canadienne De Géotechnique,1987,24(3):468-468.
[15]CHATTOPADHYAY B C,PISE P J.Axial uplift capacity of inclined piles[J].Indian Geotechnical Journal,1986,16(3):197-214.
[16]MROUEH H,SHAHROUR I.Numerical analysis of the response of battered piles to inclined pullout loads[J].International Journal for Numerical and Analytical Methods in geomechanics,2009,33(10):1 277-1 288.
[17]BHARDWAJ S,SINGH S K.Ultimate capacity of battered micropiles under oblique pullout loads[J].International Journal of Geotechnical Engineering,2014,9(2):190-200.
[18]中华人民共和国行业标准编写组.JGJ94-2008建筑桩基技术规范[S].北京:中国建筑工业出版社,2008.(The Professional Standards Compilation Group of People’s Republic of China.JGJ94-2008 Technical code for building pile foundations[S].Beijing:China Architecture and Building Press,2008.(in Chinese))
[19]JAMES R G.Some aspects of soil mechanics model testing[C]//Stress-strain Behaviour of Soils,Roscoe Memorial Symp.[S.l.]:[s.n.],1972:417-440.