基于地震波孔压静力触探(SCPTU)刚性桩承载力预测及荷载响应分析
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摘要
基于地震波孔压静力触探(SCPTU)资料对桩侧摩阻力和桩端承载力进行预测,同时提供了土层剖面特征。应用弹性理论通过实测的剪切波速估算初始桩土刚度。提出了修正双曲线法应用于弹性模量随着轴向荷载增大的非线性响应,实现了对刚性桩的荷载-沉降-承载力分析。结合不同土质条件工程实例分析,并通过统计和现场载荷试验验证了此方法的有效性和准确性。结果表明:考虑孔压修正的承载力估算法完全满足工程要求,新方法略微低估了承载力,可视为安全储备;新方法累计概率图平缓、离散性小,接近对数正态分布,具有更高可靠性;利用修正双曲线模量衰减法进行荷载响应分析具有较强的实用性。
Based on the seismic piezocone penetration test(SCPTU),pile side friction and base capacity were predicted and soil profile characteristics were also provided.According to the elastic theory,initial stiffness was estimated by the measured shear wave velocity.The modified hyperbola method was applied in axial load increases with the nonlinear responses,the rigid pile load-settlement-capacity was analyzed.In different soil conditions,the rigid piles case histories were conducted,also the effectiveness and accuracy of the method were verified by statistics and load tests.It is concluded that the new method based on revised pore pressure can completely satisfy the requirements,and it can be regarded as safety.The new method has small discrete,whose cumulative probability graph is flat,close to the lognormal distribution and higher reliability.Modified hyperbolic decay modulus method is useful for load response analysis.
Based on the seismic piezocone penetration test(SCPTU),pile side friction and base capacity were predicted and soil profile characteristics were also provided.According to the elastic theory,initial stiffness was estimated by the measured shear wave velocity.The modified hyperbola method was applied in axial load increases with the nonlinear responses,the rigid pile load-settlement-capacity was analyzed.In different soil conditions,the rigid piles case histories were conducted,also the effectiveness and accuracy of the method were verified by statistics and load tests.It is concluded that the new method based on revised pore pressure can completely satisfy the requirements,and it can be regarded as safety.The new method has small discrete,whose cumulative probability graph is flat,close to the lognormal distribution and higher reliability.Modified hyperbolic decay modulus method is useful for load response analysis.
引文
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[14]Eslami A,Fellenius B H.Pile capacity by direct CPT and CPTUmethods applied to 102 case histories[J].Canadian GeotechnicalJournal,1997,34(6):886-904.
[15]Takesue K,Sasao H,Matsumoto T.Correlation between ultimatepile skin friction and CPTdata[J].Balkema,Rotterdam:Geotech-nical Site Characterization,1998,2:1 177-1 182.
[16]Senneset K,Sandven R,Janbu N.Evaluation of soil parameters frompiezocone tests[R].Washington D C:Transportation ResearchBoard,National Research Council,1989:24-37.
[17]Lunne T,Christophersen HP,Tjelta TI.Engineering use of piezo-cone data in North Sea clays[A].Proceedings of the 11th Interna-tional Conference on Soil Mechanics and Foundation Engineering[C].San Francisco,Rotterdam:Balkema Pub.,1985.
[18]Lunne T,Robertson P K,Powell J J M.Cone penetration testing ingeotechnical practice[M].UK:Blackie Academic&Professional,1997:50-56.
[19]Salgado R.Analysis of penetration resistance in sands[D].Berke-ley,Calif.:University of California,1993.
[2]Burns S E,Mayne P W.Small-and high-strain soil properties usingthe seismic piezocone[M].Washington D C:National AcademyPress,1996.
[3]蔡国军,刘松玉,童立元,等.现代数字式多功能CPTU与中国CPT对比试验研究[J].岩石力学与工程学报,2009,28(3):914-928.Cai Guojun,Liu Songyu,Tong Liyuan,et al.Comparative perform-ance of the international 10 cm2piezocone and China 15 cm2CPTofquaternary clay deposits in Jiangsu[J].Chinese Journal of Rock Me-chanics and Engineering,2009,28(3):914-928.
[4]Cai G J,Liu S Y,Tong LY,et al.Assessment of direct CPTand CP-TU methods for predicting the ultimate bearing capacity of single pile[J].Engineering Geology,2009,104(3-4):211-222.
[5]Abu-Farsakh M Y,Titi H H.Assessment of direct cone penetrationtest methods for predicting the ultimate capacity of friction drivenpiles[J].Journal of Geotechnical and Geo-environmental Engineer-ing,ASCE,2004,130(9):935-944.
[6]苗永红,陆建飞,赵翔.饱和土中单桩的数值计算及实测分析[J].煤炭学报,2007,32(2):127-130.Miao Yonghong,Lu Jianfei,Zhao Xiang.The numerical computationand actual measurement analysis of single pile in saturated soil[J].Journal of China Coal Society,2007,32(2):127-130.
[7]Randolph MF,Wroth C P.Analysis of deformation of vertically load-ed piles[J].Journal of the Geotechnical Engineering Division,1978,104(GT12):1 465-1 488.
[8]Randolph MF,Wroth C P.Asimple approach to pile design and theevaluation of pile tests[A].Behavior of Deep Foundations,STP670,ASTM[C].West Conshohocken/PA,1979:484-499.
[9]Poulos H G,Davis E H.Pile foundation analysis and design[M].New York:Wiley&Sons,1980.
[10]Burland J B.Small is beautiful:the stiffness of soils at small strains[J].Canadian Geotechnical Journal,1989,26(4):499-516.
[11]LoPresti D C F,Pallara O,Lancellotta R,et al.Monotonic and cy-clic loading behavior of two sands at small strains[J].ASTMGeotechnical Testing Journal,1993,16(4):409-424.
[12]LoPresti D C F,Pallara O,Puci I.A modified commercial triaxialtesting system for small-strain measurements[J].ASTMGeotechni-cal Testing Journal,1995,18(1):15-31.
[13]Almeida MS S,Danziger F AB,Lunne T.Use of the piezocone testto predict the axial capacity of driven and jacked piles in clay[J].Canadian Geotechnical Journal,1996,33(1):23-41.
[14]Eslami A,Fellenius B H.Pile capacity by direct CPT and CPTUmethods applied to 102 case histories[J].Canadian GeotechnicalJournal,1997,34(6):886-904.
[15]Takesue K,Sasao H,Matsumoto T.Correlation between ultimatepile skin friction and CPTdata[J].Balkema,Rotterdam:Geotech-nical Site Characterization,1998,2:1 177-1 182.
[16]Senneset K,Sandven R,Janbu N.Evaluation of soil parameters frompiezocone tests[R].Washington D C:Transportation ResearchBoard,National Research Council,1989:24-37.
[17]Lunne T,Christophersen HP,Tjelta TI.Engineering use of piezo-cone data in North Sea clays[A].Proceedings of the 11th Interna-tional Conference on Soil Mechanics and Foundation Engineering[C].San Francisco,Rotterdam:Balkema Pub.,1985.
[18]Lunne T,Robertson P K,Powell J J M.Cone penetration testing ingeotechnical practice[M].UK:Blackie Academic&Professional,1997:50-56.
[19]Salgado R.Analysis of penetration resistance in sands[D].Berke-ley,Calif.:University of California,1993.
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