桩身参数与边界条件对低应变反射波影响研究
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摘要
在基桩完整性检测中,利用低应变法准确的确定桩身缺陷位置、判断缺陷的种类和缺陷的严重程度是低应变法亟待解决的问题。为提高反射波法检测基桩完整性的准确性,有必要通过建立实验模型并结合数值分析,系统地研究桩身参数、地质条件对低应变反射规律的影响。本文主要做了以下几项工作：
介绍了低应变反射波法一维波动理论,应力波的相互作用,应力波的三维效应,应力波受桩周土影响的拟合方程,用波阻抗法判断应力波传播规律的方法以及时域分析法判断缺陷位置。
建立了完整桩、断桩、扩颈、缩颈、离析以及夹泥夹石六种模型桩；阐述了低应变法试验前需要注意的问题；通过研究桩周地质环境对完整桩反射波的影响,得到了桩周土与应力波衰减之间的规律；通过大量的实验研究,提出了较为准确的判断断桩位置的方法；通过研究孔底沉渣厚度不同时低应变反射规律的变化,总结了判断孔底沉渣时需要注意的问题；通过比较三种不同的局部扩颈桩低应变反射波曲线,获得了局部扩颈大小与低应变反射波之间的关系；通过三种局部缩颈桩波形图比较,获得了局部缩颈大小与低应变反射波之间的关系,并提出了判断局部扩颈和局部缩颈的方法；测得了三种不同离析层厚度的桩的波形图,确定了离析层厚度对低应变反射波的影响规律；提出了利用低应变反射法检测夹泥、夹石桩的方法。
介绍了ANSYS/LS-DYNA动力显式分析方法的基本原理,并建立了此方法的有限元数值模型。对断桩、扩颈、缩颈、离析、桩周边界条件不同五种情况进行了模拟,通过与实验结果进行对比,提出了将现场试验和数值模拟结合起来,综合考虑准确的试验材料参数和桩周地质环境参数,利用数值模拟结果反推缺陷种类、缺陷位置以及缺陷程度的方法。
In the Pile Integrity Testing, there is an important unresolved issue which is using Low Strain Method to fix the pile defect, judge the kind and level of the defect. To improve the accuracy of testing the pile integrity with Reflected Wave Method, it is necessary to build an experiment model with numerical analysis to systematically study the impact of pile parameter and geological conditions on the low strain reflection rule. Several aspects are made in this paper.
One-dimension wave theory, the interaction of the stress wave, three-dimension effect of the stress wave and the fitting equation of the stress wave impacted by the pile in soil are introduced. Meanwhile the methods judging the stress wave propagation rule with the wave impedance and the defect location with time domain analysis are recommended.
Six models of integrate pile, broken pile, expanding, necking, segregation, clod in pile and stone in pile are built. Besides some issues which should be pay more attention before the experiment with Low Strain Method are dedicated. Meanwhile the relationship between the pile in soil and the stress wave attenuation by studying the impact of the pile geological conditions on the reflected wave is proposed. According to amount of experiments, a more accurate method of judging the broken pile location has been got; Some issues have been summarized which should be paid more attention by studying the thickness of the sediment in the bottom of the hole; The relationship between the size of the local expanding and the low strain reflected wave has been got by comparing three kinds of low strain reflected wave curve of the local expanding; The relationship between the size of local necking and Low Strain Reflected Method has been got by comparing the oscillograms of three kinds of local necking, including the method to judge local expanding and necking. The pile oscillograms of three kinds of segregation thickness are reviewed and the rule of the impact about the segregation thickness on the low strain reflected wave is confirmed. The method to detect clod in pile and stone in pile with low strain reflected method is summarized.
The limited numerical model of this method based on ANSYS/LS-DYNA dynamic explicit analysis is built. Meanwhile through the comparison of the experimental results with the models such as broken pile, expanding, necking, segregation, the conditions around the pile, a new method which combines with field test and numerical simulation, also including the exact experimental material parameter and the parameter of the geological conditions around the pile has been got. This method reversely judges the defect kind and location, as well as the defect level.
介绍了低应变反射波法一维波动理论,应力波的相互作用,应力波的三维效应,应力波受桩周土影响的拟合方程,用波阻抗法判断应力波传播规律的方法以及时域分析法判断缺陷位置。
建立了完整桩、断桩、扩颈、缩颈、离析以及夹泥夹石六种模型桩；阐述了低应变法试验前需要注意的问题；通过研究桩周地质环境对完整桩反射波的影响,得到了桩周土与应力波衰减之间的规律；通过大量的实验研究,提出了较为准确的判断断桩位置的方法；通过研究孔底沉渣厚度不同时低应变反射规律的变化,总结了判断孔底沉渣时需要注意的问题；通过比较三种不同的局部扩颈桩低应变反射波曲线,获得了局部扩颈大小与低应变反射波之间的关系；通过三种局部缩颈桩波形图比较,获得了局部缩颈大小与低应变反射波之间的关系,并提出了判断局部扩颈和局部缩颈的方法；测得了三种不同离析层厚度的桩的波形图,确定了离析层厚度对低应变反射波的影响规律；提出了利用低应变反射法检测夹泥、夹石桩的方法。
介绍了ANSYS/LS-DYNA动力显式分析方法的基本原理,并建立了此方法的有限元数值模型。对断桩、扩颈、缩颈、离析、桩周边界条件不同五种情况进行了模拟,通过与实验结果进行对比,提出了将现场试验和数值模拟结合起来,综合考虑准确的试验材料参数和桩周地质环境参数,利用数值模拟结果反推缺陷种类、缺陷位置以及缺陷程度的方法。
In the Pile Integrity Testing, there is an important unresolved issue which is using Low Strain Method to fix the pile defect, judge the kind and level of the defect. To improve the accuracy of testing the pile integrity with Reflected Wave Method, it is necessary to build an experiment model with numerical analysis to systematically study the impact of pile parameter and geological conditions on the low strain reflection rule. Several aspects are made in this paper.
One-dimension wave theory, the interaction of the stress wave, three-dimension effect of the stress wave and the fitting equation of the stress wave impacted by the pile in soil are introduced. Meanwhile the methods judging the stress wave propagation rule with the wave impedance and the defect location with time domain analysis are recommended.
Six models of integrate pile, broken pile, expanding, necking, segregation, clod in pile and stone in pile are built. Besides some issues which should be pay more attention before the experiment with Low Strain Method are dedicated. Meanwhile the relationship between the pile in soil and the stress wave attenuation by studying the impact of the pile geological conditions on the reflected wave is proposed. According to amount of experiments, a more accurate method of judging the broken pile location has been got; Some issues have been summarized which should be paid more attention by studying the thickness of the sediment in the bottom of the hole; The relationship between the size of the local expanding and the low strain reflected wave has been got by comparing three kinds of low strain reflected wave curve of the local expanding; The relationship between the size of local necking and Low Strain Reflected Method has been got by comparing the oscillograms of three kinds of local necking, including the method to judge local expanding and necking. The pile oscillograms of three kinds of segregation thickness are reviewed and the rule of the impact about the segregation thickness on the low strain reflected wave is confirmed. The method to detect clod in pile and stone in pile with low strain reflected method is summarized.
The limited numerical model of this method based on ANSYS/LS-DYNA dynamic explicit analysis is built. Meanwhile through the comparison of the experimental results with the models such as broken pile, expanding, necking, segregation, the conditions around the pile, a new method which combines with field test and numerical simulation, also including the exact experimental material parameter and the parameter of the geological conditions around the pile has been got. This method reversely judges the defect kind and location, as well as the defect level.
引文
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[2]Issacs D V. Reinfored concrete pile formulas[J]. Transaction of the Institution of Engineers Austialia.1931,7:312-323.
[3]Fox E N. Stress Phenomena occurring in pile driving[J]. Engineering.1932,134:263-265.
[4]Smith E. A. L. Pile driving analysis by the wave equation[J]. Journal of the Soil Mechanics and Poundtions Division.1960,86(SM4):35-61.
[5]Goble G. G. et al. Dynamic studies on the bearing capacity of piles. Division of Solid Mechanics, Structure and Mechanical Design, Case Wesern Reserve University.1970: 58-60.
[6]Goble G. G, et al. Bearing capacity of piles from dynamic measurements. find report, Case western Reserve University.1975:160-165.
[7]杨克己.实用桩基工程[M].北京：人民交通出版社,2004.
[8]Rausche. F., Goble. G. G.. Determination of pile damage by top measurements. Behavior of deep foundations ASTM.1979, STP670:500-506.
[9]王靖涛,丁美英,李国成.桩基础设计与检测.武汉：华中科技大学出版社,2005.
[10]刘兴录,周镜,刘金砺等.桩基工程手册.北京：中国建筑工业出版社,1995.
[11]Steinbach J., Vey E.. Caisson evaluation by stress wave:propagation method. J. Geotech. Eng. Div., Am. Soc. Civ. Eng..1975,101(4):361-378
[12]Milos Novak. Vertieal vibration of floating Piles[J]. Journal of the Engineering Mechanics Division.1977,103(EMI):153-168.
[13]Milos Novak, Toyoaki Nogami, Fakhry Aboul-Ella. Dynamic soil reaction for Plane strain case[J]. Journal of the Engineering Mechanics Division.1978,104(EM4):953-959.
[14]Smith I M, Chow Y K. Three-dimensional analysis of pile drivability. Proc.,2nd Int. Conf. on Numerical Methods in Off shore Piling, Austin,1982:1-20.
[15]Smith J M, Chow Y K. A Numerical Model for the Analysis of Pile Driveability. The Second Inrternational Conference on the Application of Stress-Wave Theory on Piles, Rotterdam,1984:319-325
[16]Fukuhara T, Kakurai M, Sugimoto M. Analytical evaluation of defective piles. Proc.,4th Int. Conf. on Application of Stress-Wave Theory to Piles, Hague, The Netherlands,1992:563-569.
[17]Liao S T, Roesset J M. Dynamic response of intact piles to impulse loads. Int. J. Numer. Analyt. Meth. Geomech.1997,21:255-275.
[18]Militano G, Rajapakse P K N D. Dynamic response of a Pile in a multi-layered soil to transient torsional and axial loading[J]. Geotechnique.1999,49(1):91-109.
[19]Seidel J P. Presentation of low strain integrity testing in the time-frequency domain. Proceeding of The 16th International Conference on The Application of Stress-Wavelet Theory to Piles, Sao Paulo, Brazil,2000.
[20]Chow Y K, Phoon K K, Chow W F et al. Low Strain Integrity Testing of Piles: Three-Dimensional Effects[J]. Geotech Geoenviron Eng, ASCE.2003,129(11):1057-1062.
[21]周光龙.桩基参数动测法.见：中国土木工程学会第三界土力学及基础工程学术会议论文集.北京：中国建筑工程出版社,1981.
[22]Zhou Guanglong. A new method for dynamic pile testing. ASCE 1981 International Convention & Exposition, NewYork,1981:81-96.
[23]王东阳.桥梁桩基承载特性的模拟试验法研究：(博士学位论文).西安：长安大学,2006.
[24]唐念慈.一维应力波理论应用及桩的动测法.海峡两岸土力学及基础工程地工技术学术研讨会论文集,西安,1994：302-306.
[25]王靖涛.桩基完整性动力检测的定量分析[J].施工技术.1994,(2)：18-20.
[26]王雪峰,张岚,吴世明.基桩完整性检测中的振源特性分析[J].工程勘察.2000,(6)：32-34.
[27]陈凡,王仁军.尺寸效应对基桩低应变完整性检测的影响[J].岩土工程报.1998,20(5)：92-95.
[28]徐攸在,刘家林,刘杰.用小应变动测法测定码头桩完整性的初步探讨[J].港工技术.2001,(4)：36-37.
[29]Huayou Chai, Kok-Kwang Phoon, Dianji Zhang. Effects of the Source on Wave Propagation in Pile Integrity Testing[J]. Journal of Geotechnical and Geoenvironmental Engineering.2010,136:1200-1208.
[30]柴华友,贺怀建,唐念慈.桩土相互作用模型及模型试验[J].岩体力学.1993,14(2)：75-82.
[31]Xuanming Ding, Hanlong Liu, Bo Zhang. High-frequency interference in low strain integrity testing of large-diameter pipe piles[J]. Science China Technological Sciences.2011,54(2):420-430.
[32]刘东甲.不均匀土中多缺陷桩的轴向动力响应[J].岩土工程学报,2000,22(4)：391-395.
[33]张献民.时间域中基桩缺陷低应变动测的定量分析[J].土木工程学报.2004,37(6)：64-69.
[34]王礼力.应力波基础[M].北京：国防工业出版社,2005.
[35]Achenbach J D著.徐植信,洪锦如译.弹性固体中波的传播[M].上海：同济大学出版社,1992.
[36]杜修力.工程波动理论与方法[M].北京：科学出版社,2009.
[37]谭海立.基于小波分析的基桩完整性检测：(硕士学位论文).武汉：武汉理工大学,2010.
[38]王靖涛.桩基应力波理论及工程应用[M].北京：地震出版社,1999.
[39]王致富.低应变反射波振源特性仿真分析：(硕士学位论文).成都：西南交通大学,2010.
[40]王宏志,陈云敏,陈仁朋.多层图中桩的半解析解[J].振动工程学报.2000,13(4)：660-665.
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