浅覆盖层软质岩中抗拔桩承载特性现场试验研究
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摘要
我国西部地区的电力工程正日益增加,浅覆盖层软质岩中抗拔桩在输电线路工程的杆塔基础设计中极为常见,而目前对此的相关研究相对较少,现行规范对软质岩层的桩侧摩阻力取值也有待完善。在广元市清江河南侧采用现场试验的方法研究了5根抗拔桩的承载特性,整理分析了Q-s关系曲线、桩身轴力分布和桩侧摩阻力发挥情况,得到了强风化砂岩和中风化砂岩的桩侧极限摩阻力标准值。拟合出软质砂岩的平均桩侧极限摩阻力与岩石单轴抗压强度之间的关系,进一步总结出抗拔桩极限承载力的预测公式,并将现行规范计算结果与现场试验测试结果作对比分析。结果表明,软质砂岩的平均桩侧极限摩阻力与岩石单轴抗压强度可用指数函数形式表示;强风化砂岩、中风化砂岩的桩侧极限摩阻力标准值分别为472、1 027 kPa,可为实际工程提供参考依据。
The uplift piles in soft rock with shallow overburden are common in the design of tower foundation of transmission line projects in western China, but there are relatively few studies on the uplift piles at present. The choice of pile side friction resistance value in soft rock in current codes needs to be improved. In this study, field tests in the south side of the Qingjiang river in Guangyuan City were conducted to investigate the bearing performance of 5 uplift piles. By analyzing the Q-s curve, the axial force distribution of pile shaft and the exertion of pile side friction, the standard values of pile side ultimate friction of severely weathered sandstone and weathered sandstone were obtained. The relationship between the average ultimate friction resistance and the uniaxial compressive strength(UCS) of the soft sandstone was obtained as well. A formula to predict the ultimate bearing capacity of an uplift pile was also proposed. In addition, comparison was made between the field test measurements and the value calculated using the existing standards. Our study found an exponential relation between the average side resistance of piles and the UCS of soft sandstone.The standard values of the ultimate side friction found in heavily and medium weathered sandstones were 472 kPa and 1,027 kPa,respectively. This finding provides an engineering reference for future projects.
The uplift piles in soft rock with shallow overburden are common in the design of tower foundation of transmission line projects in western China, but there are relatively few studies on the uplift piles at present. The choice of pile side friction resistance value in soft rock in current codes needs to be improved. In this study, field tests in the south side of the Qingjiang river in Guangyuan City were conducted to investigate the bearing performance of 5 uplift piles. By analyzing the Q-s curve, the axial force distribution of pile shaft and the exertion of pile side friction, the standard values of pile side ultimate friction of severely weathered sandstone and weathered sandstone were obtained. The relationship between the average ultimate friction resistance and the uniaxial compressive strength(UCS) of the soft sandstone was obtained as well. A formula to predict the ultimate bearing capacity of an uplift pile was also proposed. In addition, comparison was made between the field test measurements and the value calculated using the existing standards. Our study found an exponential relation between the average side resistance of piles and the UCS of soft sandstone.The standard values of the ultimate side friction found in heavily and medium weathered sandstones were 472 kPa and 1,027 kPa,respectively. This finding provides an engineering reference for future projects.
引文
[1]MEYERHOF G G,ADAMS J I.The ultimate uplift capacity of foundations[J].Canadian Geotechnical Journal,1968,5(4):225-244.
[2]DESHMUKH V B,DEWAIKER D M,CHOUDHURY D.Computations of uplift capacity of pile anchors in cohesionless soil[J].Acta Geotechnica,2010,5(2):87-94.
[3]CHATTOPADHAY B S,PISH P J.Uplift capacity of piles in sand[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,1989,112(9):888-904.
[4]SHANKER K,BASUDHAR P K,PATRA N R.Uplift capacity of single pile:predictions and performance[J].Geotechnical and Geotechnical Engineering,2007,25(2):151-161.
[5]SHELKE A,MISHRA S.Uplift capacity of single bent pile and pile group considering arching effects in sand[J].Geotechnical and Geotechnical Engineering,2010,28(4):337-347.
[6]董金荣.大直径灌注桩抗拔承载性状分析[J].岩土力学,2009,31(2):254-258.DONG Jin-rong.Analysis on uplift resistance of cast-in situ piles with large diameter[J].Rock and Soil Mechanics,2009,31(2):254-258.
[7]阮孝政.嵌岩桩与扩底桩抗拔承载特性数值分析[D].大连:大连理工大学,2009.RUAN Xiao-zheng.Numerical analysis of uplift bearing capacity behavior of rock-socketed piles and belled piles[D].Dalian:Dalian University of Technology,2009.
[8]宋兵,蔡健.桩-岩摩擦黏着特性的试验与分析[J].岩土力学,2011,32(8):2313-2317.SONG Bing,CAI Jian.Test and analysis of friction and adhesive characters of pile and rock[J].Rock and Soil Mechanics,2011,32(8):2313-2317.
[9]唐孟雄,陈达.基岩内抗拔桩极限承载力的计算方法[J].岩土力学,2015,36(增刊2):633-638.TANG Meng-xiong,CHEN Da.A computational method of ultimate capacity of uplift piles in basement rock[J].Rock and Soil Mechanics,2015,36(Suppl.2):633-638.
[10]何思明,吴永,李新坡.嵌岩抗拔桩作用机制研究[J].岩土力学,2009,30(2):333-337.HE Si-ming,WU Yong,LI Xin-po.Research on mechanism of uplift rock-socketed piles[J].Rock and Soil Mechanics,2009,30(2):333-337.
[11]何思明,张晓曦,王东坡.分层地基中抗拔桩破裂面的确定方法与极限抗拔承载力计算方法研究[J].岩土力学,2012,33(5):1433-1437.HE Si-ming,ZHANG Xiao-xi,WANG Dong-po.Study of computation methods of ultimate uplift capacity and determining position of failure surface of uplift piles in layered soil[J].Rock and Soil Mechanics,2012,35(5):1433-1437.
[12]中国建筑科学研究院.JGJ106-2014建筑基桩检测技术规范[S].北京:中国建筑工业出版社,2014.China Academy of Building Research.JGJ106-2014Technical code for testing of building foundation piles[S].Beijing:China Architecture&Building Press,2014.
[13]钱建固,马霄,李伟伟,等.桩侧注浆抗拔桩离心模型试验与原位测试分析[J].岩土力学,2014,35(5):1241-1247.QIAN Jian-gu,MA Xiao,LI Wei-wei,et al.Centrifuge model test and in-site observation on behaviors of side-grouting uplift pile[J].Rock and Soil Mechanics,2014,35(5):1241-1247.
[14]中国建筑科学研究院.JGJ94-2008建筑桩基技术规范[S].北京:中国建筑工业出版社,2008.China Academy of Building Research.JGJ94-2008Technical code for building pile foundations[S].Beijing:China Architecture&Building Press,2008.
[15]中华人民共和国住房和城乡建设部.GB50021-2001岩土工程勘察规范[S].北京:中国建筑工业出版社,2009.Ministry of Housing and Urban-Rural Development of the PRC.GB50021-2001 Code for investigation of geotechnical engineering[S].Beijing:China Architecture&Building Press,2009.
[16]ROSENBERG P,JOURNEAUX N L.Friction and end bearing tests on bedrock for high capacity socket design[J].Canadian Geotechnical Journal,1976,13(3):324-333.
[17]HORVATH R G,KENNEY T C.Shaft resistance of rock-socketed drilled piers[C]//Symposium on Deep Foundations.New York:ASCE,1979:182-214.
[18]MEIGH A C,WOLSKI W.Design parameters for weak rocks[C]//Proceedings of the Seventh European Conference on Soil Mechanics and Foundation Engineering,Brighton:British Geotechnical Society,1979:59-79.
[19]WILLIAMS A F,JOHNSTON I W,DONALD I B.The design of socketed piles in weak rock[C]//Proceedings of International Conference on Structure Foundations in Rock.Netherlands:[s.n.],1980:327-347.
[20]KADERABEK T J,REYNOLDS R T.Miami limestone foundation design and construction[J].Journal of the Geotechnical Engineering Devision,1981,107(7):859-872.
[21]ROWE R K,ARMITAGE H H.Theoretical solutions for axial deformation of drilled shafts in rock[J].Canadian Geotechnical Journal,1987,24(1):114-125.
[22]REESE L C,O’NEILL M W.Drilled shaft:Construction procedures and design methods[R].Washington,D.C.:Federal Highway Administration,1988.
[23]TOH C T,OOI T A,CHIU H K,et al.Design parameters for bored piles in a weathered sedimentary Formation[C]//Proceedings of 12th International Conference on Soil Mechanics and Foundation Engineering.Rio de Janerio:[s.n.],1989:1073-1078.
[24]ZHANG L Y,EINSTEIN H H.End bearing capacity of drilled shafts in rock[J].Journal of Geotechnical and Geoenvironmental Engineering,1998,124(7):574-584.
[25]NG C W W,YAN T L Y,LI J H M,et al.Side resistance of Large diameter bored piles socketed into decomposed rocks[J].Journal of Geotechnical and Geoenvironmental Engineering,2001,127(8):642-657.
[26]中国建筑科学研究院.GB50007-2011建筑地基基础设计规范[S].北京:中国建筑工业出版社,2011.China Academy of Building Research.GB50007-2011Code for design of building foundation[S].Beijing:China Architecture&Building Press,2011.
[27]中交公路规划设计院有限公司.JTG D63-2007公路桥涵地基与基础设计规范[S].北京:人民交通出版社,2007.CCCC Highway Consultants Co.Ltd.JTG D63-2007Code for design of ground base and foundation of highway bridges and culverts[S].Beijing:China Communications Press,2007.
[28]铁道第三勘察设计院集团有限公司.TB10093-2017铁路桥涵地基与基础设计规范[S].北京:中国铁道出版社,2017.The Third Survey and Design Institute of China Railway.TB10093-2017 Code for design on subsoil and foundation of railway bridge and culvert[S].Beijing:China Railway Publishing House,2017.
[29]中交第三航务工程勘察设计院有限公司.JTS 167-4-2012港口工程桩基规范[S].北京:人民交通出版社,2012.CCCC Third Harbor Consultants Co.Ltd.JTS 167-4-2012 Code for pile foundation of harbor engineering[S].Beijing:China Communications Press,2012.
[2]DESHMUKH V B,DEWAIKER D M,CHOUDHURY D.Computations of uplift capacity of pile anchors in cohesionless soil[J].Acta Geotechnica,2010,5(2):87-94.
[3]CHATTOPADHAY B S,PISH P J.Uplift capacity of piles in sand[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,1989,112(9):888-904.
[4]SHANKER K,BASUDHAR P K,PATRA N R.Uplift capacity of single pile:predictions and performance[J].Geotechnical and Geotechnical Engineering,2007,25(2):151-161.
[5]SHELKE A,MISHRA S.Uplift capacity of single bent pile and pile group considering arching effects in sand[J].Geotechnical and Geotechnical Engineering,2010,28(4):337-347.
[6]董金荣.大直径灌注桩抗拔承载性状分析[J].岩土力学,2009,31(2):254-258.DONG Jin-rong.Analysis on uplift resistance of cast-in situ piles with large diameter[J].Rock and Soil Mechanics,2009,31(2):254-258.
[7]阮孝政.嵌岩桩与扩底桩抗拔承载特性数值分析[D].大连:大连理工大学,2009.RUAN Xiao-zheng.Numerical analysis of uplift bearing capacity behavior of rock-socketed piles and belled piles[D].Dalian:Dalian University of Technology,2009.
[8]宋兵,蔡健.桩-岩摩擦黏着特性的试验与分析[J].岩土力学,2011,32(8):2313-2317.SONG Bing,CAI Jian.Test and analysis of friction and adhesive characters of pile and rock[J].Rock and Soil Mechanics,2011,32(8):2313-2317.
[9]唐孟雄,陈达.基岩内抗拔桩极限承载力的计算方法[J].岩土力学,2015,36(增刊2):633-638.TANG Meng-xiong,CHEN Da.A computational method of ultimate capacity of uplift piles in basement rock[J].Rock and Soil Mechanics,2015,36(Suppl.2):633-638.
[10]何思明,吴永,李新坡.嵌岩抗拔桩作用机制研究[J].岩土力学,2009,30(2):333-337.HE Si-ming,WU Yong,LI Xin-po.Research on mechanism of uplift rock-socketed piles[J].Rock and Soil Mechanics,2009,30(2):333-337.
[11]何思明,张晓曦,王东坡.分层地基中抗拔桩破裂面的确定方法与极限抗拔承载力计算方法研究[J].岩土力学,2012,33(5):1433-1437.HE Si-ming,ZHANG Xiao-xi,WANG Dong-po.Study of computation methods of ultimate uplift capacity and determining position of failure surface of uplift piles in layered soil[J].Rock and Soil Mechanics,2012,35(5):1433-1437.
[12]中国建筑科学研究院.JGJ106-2014建筑基桩检测技术规范[S].北京:中国建筑工业出版社,2014.China Academy of Building Research.JGJ106-2014Technical code for testing of building foundation piles[S].Beijing:China Architecture&Building Press,2014.
[13]钱建固,马霄,李伟伟,等.桩侧注浆抗拔桩离心模型试验与原位测试分析[J].岩土力学,2014,35(5):1241-1247.QIAN Jian-gu,MA Xiao,LI Wei-wei,et al.Centrifuge model test and in-site observation on behaviors of side-grouting uplift pile[J].Rock and Soil Mechanics,2014,35(5):1241-1247.
[14]中国建筑科学研究院.JGJ94-2008建筑桩基技术规范[S].北京:中国建筑工业出版社,2008.China Academy of Building Research.JGJ94-2008Technical code for building pile foundations[S].Beijing:China Architecture&Building Press,2008.
[15]中华人民共和国住房和城乡建设部.GB50021-2001岩土工程勘察规范[S].北京:中国建筑工业出版社,2009.Ministry of Housing and Urban-Rural Development of the PRC.GB50021-2001 Code for investigation of geotechnical engineering[S].Beijing:China Architecture&Building Press,2009.
[16]ROSENBERG P,JOURNEAUX N L.Friction and end bearing tests on bedrock for high capacity socket design[J].Canadian Geotechnical Journal,1976,13(3):324-333.
[17]HORVATH R G,KENNEY T C.Shaft resistance of rock-socketed drilled piers[C]//Symposium on Deep Foundations.New York:ASCE,1979:182-214.
[18]MEIGH A C,WOLSKI W.Design parameters for weak rocks[C]//Proceedings of the Seventh European Conference on Soil Mechanics and Foundation Engineering,Brighton:British Geotechnical Society,1979:59-79.
[19]WILLIAMS A F,JOHNSTON I W,DONALD I B.The design of socketed piles in weak rock[C]//Proceedings of International Conference on Structure Foundations in Rock.Netherlands:[s.n.],1980:327-347.
[20]KADERABEK T J,REYNOLDS R T.Miami limestone foundation design and construction[J].Journal of the Geotechnical Engineering Devision,1981,107(7):859-872.
[21]ROWE R K,ARMITAGE H H.Theoretical solutions for axial deformation of drilled shafts in rock[J].Canadian Geotechnical Journal,1987,24(1):114-125.
[22]REESE L C,O’NEILL M W.Drilled shaft:Construction procedures and design methods[R].Washington,D.C.:Federal Highway Administration,1988.
[23]TOH C T,OOI T A,CHIU H K,et al.Design parameters for bored piles in a weathered sedimentary Formation[C]//Proceedings of 12th International Conference on Soil Mechanics and Foundation Engineering.Rio de Janerio:[s.n.],1989:1073-1078.
[24]ZHANG L Y,EINSTEIN H H.End bearing capacity of drilled shafts in rock[J].Journal of Geotechnical and Geoenvironmental Engineering,1998,124(7):574-584.
[25]NG C W W,YAN T L Y,LI J H M,et al.Side resistance of Large diameter bored piles socketed into decomposed rocks[J].Journal of Geotechnical and Geoenvironmental Engineering,2001,127(8):642-657.
[26]中国建筑科学研究院.GB50007-2011建筑地基基础设计规范[S].北京:中国建筑工业出版社,2011.China Academy of Building Research.GB50007-2011Code for design of building foundation[S].Beijing:China Architecture&Building Press,2011.
[27]中交公路规划设计院有限公司.JTG D63-2007公路桥涵地基与基础设计规范[S].北京:人民交通出版社,2007.CCCC Highway Consultants Co.Ltd.JTG D63-2007Code for design of ground base and foundation of highway bridges and culverts[S].Beijing:China Communications Press,2007.
[28]铁道第三勘察设计院集团有限公司.TB10093-2017铁路桥涵地基与基础设计规范[S].北京:中国铁道出版社,2017.The Third Survey and Design Institute of China Railway.TB10093-2017 Code for design on subsoil and foundation of railway bridge and culvert[S].Beijing:China Railway Publishing House,2017.
[29]中交第三航务工程勘察设计院有限公司.JTS 167-4-2012港口工程桩基规范[S].北京:人民交通出版社,2012.CCCC Third Harbor Consultants Co.Ltd.JTS 167-4-2012 Code for pile foundation of harbor engineering[S].Beijing:China Communications Press,2012.
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