土岩组合岩体中抗拔桩极限承载力的确定
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摘要
为全面探究土岩组合岩体中抗拔桩的极限承载力,结合工程岩土参数及试验数据,运用Flac~(3D)数值分析软件对其进行数值模拟分析,即可得到土岩组合岩体中抗拔桩的极限承载力。基于被动状态下的Kotter极限平衡方程式求解土层提供的抗拔力,根据岩石强度,基于Hoek-Brown破坏准则求解抗拔桩嵌岩端岩体的抗拉强度,从而可计算得到嵌岩端岩体的抗拔力;由静力平衡原理,叠加土层及嵌岩端岩体提供的抗拔力及破坏锥体重量,即可得到土岩组合岩体中嵌岩抗拔桩的极限承载力理论解析式。在嵌岩深度较小的情况下,该解析式的理论计算值与数值模拟分析值相接近,但随着嵌岩深度的增加,理论计算值会偏离数值计算值。故结合数值模拟试验值,对提出的极限承载力理论解析式作进一步的修正,得到修正后的极限承载力解析式能反映嵌岩端岩石风化程度、嵌岩深度、土层厚度、桩长对极限承载力的影响。运用修正后的解析式对该地质条件下不同抗拔桩的极限承载力计算表明:数值模拟结果与理论计算结果相吻合,说明所建立的抗拔桩极限承载力解析式的方法是可行的。同时,运用该方法可确定类似工程中嵌岩抗拔桩的极限承载力。
In order to comprehensively explore the ultimate bearing capacity of uplift piles in combined soil and rock masses, combined with engineering geotechnical parameters and experimental data, the Flac~(3D) numerical analysis software is adopted to carry out numerical simulation analysis to obtain the ultimate bearing capacity of uplift piles in the composite rock mass. The Kotter limit equilibrium passive equation is employed to solve the pull-out force provided by the soil layer. And based on the rock strength, the strength of the rock mass embedded in the rock pile can be determined by the Hoek-Brown failure criterion. In turn, the pull-out force of the rock mass embedded in the rock can also be obtained. In addtion, based on the principle of force balance, the ultimate bearing capacity of rock in lay uplift piles in the combined rock mass can be obtained by superimposing the pull-out resistance provided by failure rock layer and the rock mass on the gravity of failure cone. The theoretical calculation value obtained from the analytical formula is close to the numerical simulation analysis value in the case of small rock-socketed depth. However, with the increase of the rock-socketed depth, the theoretical calculation value fluctuates within a certain range around the experimental value. Therefore, combining with the numerical results, the theoretical formula of the ultimate bearing capacity is modified. Finally, by taking the consideration of the effect of rock wathering, rock-sockering depth, soil thickness and pile length, the improved ultimate bearing capacity analytical formula is obtained. The modified analytical formula is used to predict the ultimate bearing capacity of different uplift piles under different geological conditions. The predicted results show that the numerical simulation results are consistent with the theoretical calculation results, which means the analytical method of the ultimate bearing capacity of uplift piles in this paper is feasible. Based on a part of test result, the ultimate bearing capacity of different rock-socked piles with different rock-socked depths in similar projects can be determined by this method.
In order to comprehensively explore the ultimate bearing capacity of uplift piles in combined soil and rock masses, combined with engineering geotechnical parameters and experimental data, the Flac~(3D) numerical analysis software is adopted to carry out numerical simulation analysis to obtain the ultimate bearing capacity of uplift piles in the composite rock mass. The Kotter limit equilibrium passive equation is employed to solve the pull-out force provided by the soil layer. And based on the rock strength, the strength of the rock mass embedded in the rock pile can be determined by the Hoek-Brown failure criterion. In turn, the pull-out force of the rock mass embedded in the rock can also be obtained. In addtion, based on the principle of force balance, the ultimate bearing capacity of rock in lay uplift piles in the combined rock mass can be obtained by superimposing the pull-out resistance provided by failure rock layer and the rock mass on the gravity of failure cone. The theoretical calculation value obtained from the analytical formula is close to the numerical simulation analysis value in the case of small rock-socketed depth. However, with the increase of the rock-socketed depth, the theoretical calculation value fluctuates within a certain range around the experimental value. Therefore, combining with the numerical results, the theoretical formula of the ultimate bearing capacity is modified. Finally, by taking the consideration of the effect of rock wathering, rock-sockering depth, soil thickness and pile length, the improved ultimate bearing capacity analytical formula is obtained. The modified analytical formula is used to predict the ultimate bearing capacity of different uplift piles under different geological conditions. The predicted results show that the numerical simulation results are consistent with the theoretical calculation results, which means the analytical method of the ultimate bearing capacity of uplift piles in this paper is feasible. Based on a part of test result, the ultimate bearing capacity of different rock-socked piles with different rock-socked depths in similar projects can be determined by this method.
引文
[1]袁文忠,于志强,谢涛.岩基强度对嵌岩抗拔桩承载力影响的试验研究[J].西南交通大学学报,2003,38(2):178-182.YUAN Wen-zhong,YU Zhi-qiang,XIE Tao.Experimental study on the influence of rock embankment strength on bearing capacity of rock-embedded anti-torsion piles[J].Journal of Southwest Jiaotong University,2003,38(2):178-182.
[2]吴兴序,于志强,庄卫林.岩层中抗拔桩的承载力计算方法探讨[J].西南交通大学学报,2002,37(2):190-194.WU Xing-xu,YU Zhi-qiang,ZHUANG Wei-lin.Discussion on calculation methods of bearing capacity of uplift piles in rock stratum[J].Journal of Southwest Jiaotong University,2002,37(2):190-194.
[3]吴孟松.上覆土软质岩等截面嵌岩桩抗拔承载特性研究[D].成都:西南交通大学,2017.WU Meng-song.Overburden soft rock cross-section of rock-socketed load-bearing characteristics[D].Chengdu:Southwest Jiaotong University,2017.
[4]MEYERHOF G G.Uplift resistance of inclined anchors and piles[C]//Proceedings of the 8th International Conference on Soil Mechanics and Foundation Engineering.Moscow:Kluwer Academic Publisher Plenum Publishers,1973.
[5]DAS B M.A procedure for estimation of uplift capacity of rough piles[J].Soils and Foundations,1983,23(3):122-126.
[6]CHATTOPADHYAY B C,PISE P J.Uplift capacity of piles in sand[J].Journal of Geotechnical Engineering,1986,112(9):888-904.
[7]SHIN E C,DAS B M,PURIVK,et al.Ultimate uplift capacity of model rigid metal piles in clay[J].Geotechnical and Geological Engineering,1993,11(3):203-215.
[8]DESHMUKH V B,DEWAIKAR D M,CHOUDHURY D.Computations of uplift capacity of pile anchors in cohesionless soil[J].Acta Geotechnica,2010,5(2):87-94.
[9]KHATRI V N,KUMAR J.Uplift capacity of axially loaded piles in clays[J].International Journal of Geomechanics,2011,11(1):23-28.
[10]张继红,朱合华.抗拔桩极限平衡方程及其应用[J].岩土力学,2015,36(8):2339-2344.ZHANG Ji-hong,ZHU He-hua.Limit equilibrium equation for uplift piles and its application[J].Rock and Soil Mechanics,2015,36(8):2339-2344.
[11]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.WU Meng-xiong,CHEN Da.Computational method of ultimate capacity of uplift piles in basement rock[J].Rock and Soil Mechanics,2015,36(Suppl.2):633-638.
[12]柳晓科,鹿群,路士伟,等.低裙式吸力桩真空沉贯及抗拔极限承载力[J].岩土力学,2018,39(6):2089-2098.LIU Xiao-ke,LU Qun,LU Shi-wei,et al.Vacuum penetration and ultimate pull-out capacity of low skirted suction caissons[J].Rock and Soil Mechanics,2018,39(6):2089-2098.
[13]WYLLIE D C,GOODMAN R E.Foundations on rock[M].[S.l.]:E&FN Spon,1999.
[14]MEYERHOF G G,ADAMS J I.The ultimate uplift capacity of foundations[J].Canadian Geotechnical Journal,1968,5(4):225-244.
[15]K?TTER F.Die Bestimmung des Drucks an gekrümmten Gleitfl?chen,eine Aufgabe aus der Lehrevom Erddruck[C]//Proceedings of der Akademie der Wissenschaften.Berlin:[s.n.],1903.
[16]孔德顺.Kotter方程在挡土墙被动土压力求解中的应用[D].南京:河海大学,2008.KONG De-shun.Application of Kotter's equation in solving passive earth pressure on retaining wall[D].Nanjing:Hohai University,2008.
[17]HOEK E,BROWN E T.Underground excavations in rocks[M].London:Institution of Mining and Metallurgy,1980:527.
[18]刘佑荣,唐辉明.岩体力学[M].北京:化学工业出版社,2008.LIU You-rong,TANG Hui-ming.Rock mechanics[M].Beijing:Chemical Industry Press,2008.
[19]中国建筑工业出版社.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 Building Industry Press.JGJ106-2014 Building foundation pile testing technology specification[S].Beijing:China Building Industry Press,2014.
[20]中国建筑科学研究院.DBJ52/T079-2016基桩承载力自平衡检测技术规程[S].北京:中国建筑工业出版社,2016.China Academy of Building Research.DBJ52/T079-2016 Technical specification for self-balance detection of bearing capacity of piles[S].Beijing:China Architecture&Building Press,2016.
[21]中国建筑工业出版社.GB50007-2011建筑地基基础设计规范[S].北京:中国建筑工业出版社,2012.China Building Industry Press.GB50007-2011Specification for foundation design of building foundation[S].Beijing:China Architecture&Building Press,2012.
[22]孙书伟,林杭,任连伟.FLAC3D在岩土工程中的应用[M].北京:中国水利水电出版社,2011.SUN Shu-wei,LIN Hang,REN Lian-wei.FLAC3D in geotechnical engineering[M].Beijing:China Water Power Press,2011.
[23]刘衡,杨波,王铁行.厚层沉渣嵌岩桩承载性能试验分析与数值模拟[J].铁道建筑,2012(12):93-95.LIU Heng,YANG Bo,WANG Tie-hang.Experimental analysis and numerical simulation of bearing capacity of rock-socketed piles with thick layers[J].Railway Construction,2012(12):93-95.
[24]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 Specification for Pile Foundations[S].Beijing:China Architecture&Building Press,2008.
[25]李海霞.嵌岩抗拔桩承载力特性研究[D].合肥:合肥工业大学,2012.LI Hai-xia.Study on bearing capacity of rock-fill anti-pull pile[D].Hefei:Hefei University of Technology,2012.
[2]吴兴序,于志强,庄卫林.岩层中抗拔桩的承载力计算方法探讨[J].西南交通大学学报,2002,37(2):190-194.WU Xing-xu,YU Zhi-qiang,ZHUANG Wei-lin.Discussion on calculation methods of bearing capacity of uplift piles in rock stratum[J].Journal of Southwest Jiaotong University,2002,37(2):190-194.
[3]吴孟松.上覆土软质岩等截面嵌岩桩抗拔承载特性研究[D].成都:西南交通大学,2017.WU Meng-song.Overburden soft rock cross-section of rock-socketed load-bearing characteristics[D].Chengdu:Southwest Jiaotong University,2017.
[4]MEYERHOF G G.Uplift resistance of inclined anchors and piles[C]//Proceedings of the 8th International Conference on Soil Mechanics and Foundation Engineering.Moscow:Kluwer Academic Publisher Plenum Publishers,1973.
[5]DAS B M.A procedure for estimation of uplift capacity of rough piles[J].Soils and Foundations,1983,23(3):122-126.
[6]CHATTOPADHYAY B C,PISE P J.Uplift capacity of piles in sand[J].Journal of Geotechnical Engineering,1986,112(9):888-904.
[7]SHIN E C,DAS B M,PURIVK,et al.Ultimate uplift capacity of model rigid metal piles in clay[J].Geotechnical and Geological Engineering,1993,11(3):203-215.
[8]DESHMUKH V B,DEWAIKAR D M,CHOUDHURY D.Computations of uplift capacity of pile anchors in cohesionless soil[J].Acta Geotechnica,2010,5(2):87-94.
[9]KHATRI V N,KUMAR J.Uplift capacity of axially loaded piles in clays[J].International Journal of Geomechanics,2011,11(1):23-28.
[10]张继红,朱合华.抗拔桩极限平衡方程及其应用[J].岩土力学,2015,36(8):2339-2344.ZHANG Ji-hong,ZHU He-hua.Limit equilibrium equation for uplift piles and its application[J].Rock and Soil Mechanics,2015,36(8):2339-2344.
[11]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.WU Meng-xiong,CHEN Da.Computational method of ultimate capacity of uplift piles in basement rock[J].Rock and Soil Mechanics,2015,36(Suppl.2):633-638.
[12]柳晓科,鹿群,路士伟,等.低裙式吸力桩真空沉贯及抗拔极限承载力[J].岩土力学,2018,39(6):2089-2098.LIU Xiao-ke,LU Qun,LU Shi-wei,et al.Vacuum penetration and ultimate pull-out capacity of low skirted suction caissons[J].Rock and Soil Mechanics,2018,39(6):2089-2098.
[13]WYLLIE D C,GOODMAN R E.Foundations on rock[M].[S.l.]:E&FN Spon,1999.
[14]MEYERHOF G G,ADAMS J I.The ultimate uplift capacity of foundations[J].Canadian Geotechnical Journal,1968,5(4):225-244.
[15]K?TTER F.Die Bestimmung des Drucks an gekrümmten Gleitfl?chen,eine Aufgabe aus der Lehrevom Erddruck[C]//Proceedings of der Akademie der Wissenschaften.Berlin:[s.n.],1903.
[16]孔德顺.Kotter方程在挡土墙被动土压力求解中的应用[D].南京:河海大学,2008.KONG De-shun.Application of Kotter's equation in solving passive earth pressure on retaining wall[D].Nanjing:Hohai University,2008.
[17]HOEK E,BROWN E T.Underground excavations in rocks[M].London:Institution of Mining and Metallurgy,1980:527.
[18]刘佑荣,唐辉明.岩体力学[M].北京:化学工业出版社,2008.LIU You-rong,TANG Hui-ming.Rock mechanics[M].Beijing:Chemical Industry Press,2008.
[19]中国建筑工业出版社.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 Building Industry Press.JGJ106-2014 Building foundation pile testing technology specification[S].Beijing:China Building Industry Press,2014.
[20]中国建筑科学研究院.DBJ52/T079-2016基桩承载力自平衡检测技术规程[S].北京:中国建筑工业出版社,2016.China Academy of Building Research.DBJ52/T079-2016 Technical specification for self-balance detection of bearing capacity of piles[S].Beijing:China Architecture&Building Press,2016.
[21]中国建筑工业出版社.GB50007-2011建筑地基基础设计规范[S].北京:中国建筑工业出版社,2012.China Building Industry Press.GB50007-2011Specification for foundation design of building foundation[S].Beijing:China Architecture&Building Press,2012.
[22]孙书伟,林杭,任连伟.FLAC3D在岩土工程中的应用[M].北京:中国水利水电出版社,2011.SUN Shu-wei,LIN Hang,REN Lian-wei.FLAC3D in geotechnical engineering[M].Beijing:China Water Power Press,2011.
[23]刘衡,杨波,王铁行.厚层沉渣嵌岩桩承载性能试验分析与数值模拟[J].铁道建筑,2012(12):93-95.LIU Heng,YANG Bo,WANG Tie-hang.Experimental analysis and numerical simulation of bearing capacity of rock-socketed piles with thick layers[J].Railway Construction,2012(12):93-95.
[24]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 Specification for Pile Foundations[S].Beijing:China Architecture&Building Press,2008.
[25]李海霞.嵌岩抗拔桩承载力特性研究[D].合肥:合肥工业大学,2012.LI Hai-xia.Study on bearing capacity of rock-fill anti-pull pile[D].Hefei:Hefei University of Technology,2012.
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