CPTU确定饱和土体水平渗透系数的改进方法
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摘要
目前采用的球面流或半球面流模型所预测的饱和土体渗透系数普遍低于实测值,为提高孔压静力触探(CPTU)测试技术确定饱和土体水平渗透系数的准确性,针对初始超孔隙水压力的分布形式、孔压过滤环的位置和渗流模型3个主要问题,在回顾前人方法基础上,提出一种基于CPTU确定饱和土体水平渗透系数kh的改进方法.根据已有研究成果,将锥肩附近初始超孔隙水压力视为负指数型衰减分布,结合圆柱面径向渗流模型,推导出饱和土体水平渗透系数的计算公式,应用算例验证了本文方法的合理性,再结合上海某地的实测数据,将本文方法与已有方法进行对比分析,研究结果显示:本文方法计算的渗透系数大于已有方法,更接近室内渗透试验的结果;CPTU测试技术可用于连续且快速地计算饱和土体水平渗透系数.
To increase accuracy of estimating permeability coefficient of saturated soils using piezocone penetration tests( CPTU),taking account that the permeability coefficient of saturated soils estimated by the existing flow model to the spherical or the hemispherical surface is generally lower than the measured value,a modified approach was proposed,in which the initial excess pore water pressure,the location of filter element and seepage model were studied after the researches on evaluation of permeability coefficient of saturated soils were briefly reviewed. Based on the existing results,the initial excess pore water pressure around the shoulder of the cone was regarded as negative exponential attenuation distribution. Combined with the radial flow model to a cylindrical surface,the expression of horizontal permeability coefficient of saturated soils was derived. The comparison between the predicted and measured values demonstrates that the modified approach is reasonable and effective. The results show that the horizontal permeability coefficient determined by the modified approach is larger than that of previous approaches and more close to the corresponding measured value in laboratory tests. The horizontal permeability coefficient of saturated soils can be continuously and rapidly determined by CPTU.
To increase accuracy of estimating permeability coefficient of saturated soils using piezocone penetration tests( CPTU),taking account that the permeability coefficient of saturated soils estimated by the existing flow model to the spherical or the hemispherical surface is generally lower than the measured value,a modified approach was proposed,in which the initial excess pore water pressure,the location of filter element and seepage model were studied after the researches on evaluation of permeability coefficient of saturated soils were briefly reviewed. Based on the existing results,the initial excess pore water pressure around the shoulder of the cone was regarded as negative exponential attenuation distribution. Combined with the radial flow model to a cylindrical surface,the expression of horizontal permeability coefficient of saturated soils was derived. The comparison between the predicted and measured values demonstrates that the modified approach is reasonable and effective. The results show that the horizontal permeability coefficient determined by the modified approach is larger than that of previous approaches and more close to the corresponding measured value in laboratory tests. The horizontal permeability coefficient of saturated soils can be continuously and rapidly determined by CPTU.
引文
[1]邹海峰,蔡国军,刘松玉.基于位错理论的饱和土渗流特性CPTU评价研究[J].岩土工程学报,2014,36(3):519-528.DOI:10.11779/CJGE201403015.ZOU Haifeng,CAI Guojun,LIU Songyu.Evaluation of coefficient of permeability of saturated soils based on CPTU dislocation theory[J].Chinese Journal of Geotechnical Engineering,2014,36(3):519-528.DOI:10.11779/CJGE201403015.
[2]刘松玉,蔡国军,邹海峰.基于CPTU的中国实用土分类方法研究[J].岩土工程学报,2013,35(10):1765-1776.LIU Songyu,CAI Guojun,ZOU Haifeng.Practical soil classification methods in China based on piezocone penetration tests[J].Chinese Journal of Geotechnical Engineering,2013,35(10):1765-1776.
[3]ROBERTSON P K.Estimating in-situ soil permeability from CPT&CPTU[C]//Proceedings of the 2nd International Symposium on Cone Penetration Testing(CPT'10).Huntington Beach,California:California State Polytechnic University Pomona,2010:535-542.
[4]ELSWORTH D,LEE D S.Permeability determination from on-thefly piezocone sounding[J].Journal of Geotechnical and Geoenvironmental Engineering,2005,131(5):643-653.DOI:10.1061/(ASCE)1090-0241(2005)131:5(643).
[5]ELSWORTH D,LEE D S.Limits in determining permeability from on-the-fly CPTu sounding[J].Géotechnique,2007,57(8):679-686.DOI:10.1680/geot.2007.57.8.679.
[6]CHAI J C,AGUNG P M A,HINO T,et al.Estimating hydraulic conductivity from piezocone soundings[J].Géotechnique,2011,61(8):1-10.DOI:10.1680/geot.10.P.009.
[7]王君鹏,沈水龙.基于孔压静力触探确定土体的渗透系数[J].岩土力学,2013(11):3335-3339.WANG Junpeng,SHEN Shuilong.Determination of permeability coefficient of soil based on CPTU[J].Rock and Soil Mechanics,2013(11):3335-3339.
[8]WANG J P,XU Y S,MA L,et al.An approach to evaluate hydraulic conductivity of soil based on CPTU test[J].Marine Georesources and Geotechnology,2013,31(3):242-253.DOI:10.1080/1064119X.2012.676154.
[9]朱小林,唐世栋.利用孔隙水压力-静力触探探头估算软黏土固结系数的理论分析[J].工程勘察,1986(6):8-12,23.ZHU Xiaolin,TANG Shidong.Theoretical analysis of the coefficient of consolidation in soft clay estimated by pore water pressure-cone of cone penetration test[J].Geotechnical Investigation&Surveying,1986(6):8-12,23.
[10]马淑芝,汤艳春,孟高头,等.孔压静力触探测试机理、方法及工程应用[M].武汉:中国地质大学出版社,2007.MA Shuzhi,TANG Yanchun,MENG Gaotou,et al.Mechanism,methods and engineering application of piezocone penetration tests[M].Wuhan:China University of Geosciences Press,2007.
[2]刘松玉,蔡国军,邹海峰.基于CPTU的中国实用土分类方法研究[J].岩土工程学报,2013,35(10):1765-1776.LIU Songyu,CAI Guojun,ZOU Haifeng.Practical soil classification methods in China based on piezocone penetration tests[J].Chinese Journal of Geotechnical Engineering,2013,35(10):1765-1776.
[3]ROBERTSON P K.Estimating in-situ soil permeability from CPT&CPTU[C]//Proceedings of the 2nd International Symposium on Cone Penetration Testing(CPT'10).Huntington Beach,California:California State Polytechnic University Pomona,2010:535-542.
[4]ELSWORTH D,LEE D S.Permeability determination from on-thefly piezocone sounding[J].Journal of Geotechnical and Geoenvironmental Engineering,2005,131(5):643-653.DOI:10.1061/(ASCE)1090-0241(2005)131:5(643).
[5]ELSWORTH D,LEE D S.Limits in determining permeability from on-the-fly CPTu sounding[J].Géotechnique,2007,57(8):679-686.DOI:10.1680/geot.2007.57.8.679.
[6]CHAI J C,AGUNG P M A,HINO T,et al.Estimating hydraulic conductivity from piezocone soundings[J].Géotechnique,2011,61(8):1-10.DOI:10.1680/geot.10.P.009.
[7]王君鹏,沈水龙.基于孔压静力触探确定土体的渗透系数[J].岩土力学,2013(11):3335-3339.WANG Junpeng,SHEN Shuilong.Determination of permeability coefficient of soil based on CPTU[J].Rock and Soil Mechanics,2013(11):3335-3339.
[8]WANG J P,XU Y S,MA L,et al.An approach to evaluate hydraulic conductivity of soil based on CPTU test[J].Marine Georesources and Geotechnology,2013,31(3):242-253.DOI:10.1080/1064119X.2012.676154.
[9]朱小林,唐世栋.利用孔隙水压力-静力触探探头估算软黏土固结系数的理论分析[J].工程勘察,1986(6):8-12,23.ZHU Xiaolin,TANG Shidong.Theoretical analysis of the coefficient of consolidation in soft clay estimated by pore water pressure-cone of cone penetration test[J].Geotechnical Investigation&Surveying,1986(6):8-12,23.
[10]马淑芝,汤艳春,孟高头,等.孔压静力触探测试机理、方法及工程应用[M].武汉:中国地质大学出版社,2007.MA Shuzhi,TANG Yanchun,MENG Gaotou,et al.Mechanism,methods and engineering application of piezocone penetration tests[M].Wuhan:China University of Geosciences Press,2007.