静力触探参数自相关距离确定方法与影响因素分析
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摘要
在岩土工程可靠性分析中,土性参数空间变异性的分析至关重要,其中土体的固有变异性可以通过随机场理论获取方差折减函数和自相关距离值进行分析。基于天津临港静力触探试验(CPT)得到的锥尖阻力,对波动函数法确定自相关距离过程中所遇到的问题进行深入研究,并分析了去趋势化方法、取样间距、取样范围等影响自相关距离的因素。结合空间递推平均法的改进方法,首次对应用波动函数法确定自相关距离时出现的多个峰值的选择开展分析,结果表明对于所分析场地的地层静力触探数据而言,应选取波动函数曲线中第一个峰值作为该土层的自相关距离值。通过去趋势化后的随机分量统计特性及对应自相关距离计算结果的对比发现,去趋势化方法要依实际情况而定,并不是所有情况都可以使用线性去趋势化方法,建议最高选用二次非线性拟合结果对原始数据去趋势化;当取样范围较大,即触探孔数量较多时自相关距离随取样间距的增大而增大。分析还表明,对于同样的样本间距,随着触探孔数量的增加,自相关距离是逐渐减小的,但这种差距随着取样间距的增大而逐渐缩小。
The spatial variability of soil properties in reliability analysis is of great importance, of which the inherent variability of soil can be analyzed through random field theory by determination of coefficient of variance and scale of fluctuation. In this paper, efforts have been devoted to the fluctuation function method to determine scale of fluctuation. Meanwhile, factors such as trend removal method, sampling spacing and sampling range are analyzed based on tip resistance from cone penetration test(CPT), modeling as a random field. It turned out that, as to analyzed data in this paper, if more than one peak point exists when employing the fluctuation function method, the first peak point should be taken as the scale of fluctuation of the soil, which has never been analyzed before. As to affecting factors, some very useful conclusions are obtained. Firstly, selection of the trend removal method should be based on the condition of soil properties; and the quadratic trend removal method is suggested if nonlinear method adopted. Secondly, the scale of fluctuation increases with increasing of sampling spacing when the number of CPTs is large. Last but not the least, as to a same sampling spacing, the scale of fluctuation decreases with increasing of the number of penetration tests; but such difference gradually becomes not obvious for large sampling spacing.
The spatial variability of soil properties in reliability analysis is of great importance, of which the inherent variability of soil can be analyzed through random field theory by determination of coefficient of variance and scale of fluctuation. In this paper, efforts have been devoted to the fluctuation function method to determine scale of fluctuation. Meanwhile, factors such as trend removal method, sampling spacing and sampling range are analyzed based on tip resistance from cone penetration test(CPT), modeling as a random field. It turned out that, as to analyzed data in this paper, if more than one peak point exists when employing the fluctuation function method, the first peak point should be taken as the scale of fluctuation of the soil, which has never been analyzed before. As to affecting factors, some very useful conclusions are obtained. Firstly, selection of the trend removal method should be based on the condition of soil properties; and the quadratic trend removal method is suggested if nonlinear method adopted. Secondly, the scale of fluctuation increases with increasing of sampling spacing when the number of CPTs is large. Last but not the least, as to a same sampling spacing, the scale of fluctuation decreases with increasing of the number of penetration tests; but such difference gradually becomes not obvious for large sampling spacing.
引文
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[17]林军,蔡国军,邹海峰,等.基于随机场理论的江苏海相黏土空间变异性评价研究[J].岩土工程学报,2015,37(7):1278-1287.LIN Jun,CAI Guo-jun,ZOU Hai-feng,et al.Assessment of spatial variability of jiangsu marine clay based on random field theory[J].Chinese Journal of Geotechnical Engineering,2015,37(7):1278-1287.
[18]郭林坪,杨爱武,闫澍旺,等.天津港地区土层剖面随机场特征参数的估计[J].工程地质学报,2016,24(1):130-135.GUO Lin-ping,YANG Ai-wu,YAN Shu-wang,et al.Estimation of random field characteristic parameters of soil layers in Tianjin port[J].Journal of Engineering Geology,2016,24(1):130-135.
[19]闫澍旺,郭林坪,曹永华.岩土工程可靠度分析中方差折减函数确定的一般规律[J].岩土力学,2014,35(8):2286-2292.YAN Shu-wang,GUO Ling-ping,CAO Yong-hua.Regularity of the reduction function of variance in eliability analysis in geotechnical engineering[J].Rock and Soil Mechanics,2014,35(8):2286-2292.
[20]YAN Shu-wang,GUO Lin-ping.Calculation of scale of fluctuation and variance reduction function[J].Transactions of Tianjin University,2015,21(1):41-49.
[21]常士骠,张苏民.工程地质手册[M].北京:中国建筑工业出版社,2007.CHANG Shi-biao,ZHANG Su-min.Manual of engineering geology[M].Beijing:China Architecture&Building Press,2007.
[22]COMPANELLA R G,WICKREMESINGHE D,ROBERTSON P K.Statistical treatment of cone penetrometer test data[C]//The Fifth International Conference on Applications of Statistics and Probability in Soil and Structural Engineering.Canada;[s.n.],1987.
[2]朱红霞.随机场理论在地基可靠度分析中的应用研究[D].天津:天津大学,2007.ZHU Hong-xia.Study of using random field theory in soil foundation reliability analysis[D].Tianjin:Tianjin University,2007.
[3]JAKSA M B,KAGGWA W S,BROOKER P I.Experimental evaluation of the scale of fluctuation of a stiff clay[C]//International Conference on Applications of Statistics and Probability.Sydney:[s.n.],1999.
[4]JAKSA M B,BROOKER P I,KAGGWA W S.Inaccuracies associated with estimating random measurement errors[J].Journal of Geotechnical and Geoenvironmental Engineering,1997,123(5):393-401.
[5]CAFARO F,CHERUBINI C.Large sample spacing in evaluation of vertical strength variability of clayey soil[J].Journal of Geotechnical and Geoenvironmental Engineering,2002,128(7):558-568.
[6]DASAKA,S M,ZHANG,L M.Spatial variability of in situ weathered soil[J].Geotechnique,2012,62(5):375-384.
[7]LLORET-CABOT M,FENTON G A,HICKS M A.On the estimation of scale of fluctuation in geostatistics[J].Georisk,2014,8(2):129-140.
[8]ONYEJEKWE S,KANG Xin,GE Louis.Evaluation of the scale of fluctuation of geotechnical parameters by autocorrelation function and semivariogram function[J].Engineering Geology,2016,9(14):43-49.
[9]闫澍旺,贾晓黎,郭怀志.土性剖面随机场模型的平稳性和各态历经性验证[J].岩土工程学报,1995,17(3):1-9.YAN Shu-wang,JIA Xiao-li,GUO Huai-zhi.Inspection of stationary and ergodicity of random field model of soil profile[J].Chinese Journal of Geotechnical Engineering,1995,17(3):1-9.
[10]丁继辉,宇云飞,张庆宏,等.土性相关距离计算的非线性曲线拟合法[J].勘察科学技术,2000,17(3):13-22.DING Ji-hui,YU Yun-fei,ZHANG Qing-hong,et al.Nonlinear curve fitting method of the soil property correlative distance calculation[J].Site Investigation Science and Technology,2000,17(3):13-22.
[11]李小勇,谢康和,虞颜.土性指标相关距离性状的研究[J].土木工程学报,2003,36(8):91-95,108.LI Xiao-yong,XIE Kang-he,YU Yan.Research on the characteristics of correlation distance on soil properties indexes[J].China Civil Engineering Journal,2003,36(8):91-95,108.
[12]闫澍旺,朱红霞,刘润,等.关于土层相关距离计算方法的研究[J].岩土力学,2007,28(8):1581-1586.YAN Shu-wang,ZHU Hong-xia,LIU Run,et al.Study on methods for estimating correlation distance of soil layers[J].Rock and Soil Mechanics,2007,28(8):1581-1586.
[13]杨勇,范文,赵治海,等.用于计算西安黄土相关距离的空间范围的探讨[J].土木工程学报,2014,47(11):92YANG Yong,FAN Wen,ZHAO Zhi-hai,et al.Investigations of spatial range associated with the calculation of the correlation distance for Xi’an loess[J].China Civil Engineering Journal,2014,47(11):92-97.
[14]傅旭东.静力触探参数相关范围的估算[J].岩土力学,1999,20(4):76-80.FU Xu-dong.Estimation on scale of fluctuation of cone penetration test parameters[J].Rock and Soil Mechanics,1999,20(4):76-80.
[15]张继周,缪林昌,陈俊波.苏中腹地湖相软土土性参数变异性统计描述[J].岩土力学,2010,31(2):471-477.ZHANG Ji-zhou,MIAO Lin-chang,CHEN Jun-bo.Statistical characterization of variability of lacustrine soft soil in central region of Jiangsu Province[J].Rock and Soil Mechanics,2010,31(2):471-477.
[16]李新生,刘超.相关距离分析与勘察钻孔取样间距的合理确定[J].水文地质工程地质,2011,38(4):74-77.LI Xin-sheng,LIU Chao.Analysis on scale of fluctuation and determination of sampling space of borehole[J].Hydrogeology and Engineering Geology,2011,38(4):74-77.
[17]林军,蔡国军,邹海峰,等.基于随机场理论的江苏海相黏土空间变异性评价研究[J].岩土工程学报,2015,37(7):1278-1287.LIN Jun,CAI Guo-jun,ZOU Hai-feng,et al.Assessment of spatial variability of jiangsu marine clay based on random field theory[J].Chinese Journal of Geotechnical Engineering,2015,37(7):1278-1287.
[18]郭林坪,杨爱武,闫澍旺,等.天津港地区土层剖面随机场特征参数的估计[J].工程地质学报,2016,24(1):130-135.GUO Lin-ping,YANG Ai-wu,YAN Shu-wang,et al.Estimation of random field characteristic parameters of soil layers in Tianjin port[J].Journal of Engineering Geology,2016,24(1):130-135.
[19]闫澍旺,郭林坪,曹永华.岩土工程可靠度分析中方差折减函数确定的一般规律[J].岩土力学,2014,35(8):2286-2292.YAN Shu-wang,GUO Ling-ping,CAO Yong-hua.Regularity of the reduction function of variance in eliability analysis in geotechnical engineering[J].Rock and Soil Mechanics,2014,35(8):2286-2292.
[20]YAN Shu-wang,GUO Lin-ping.Calculation of scale of fluctuation and variance reduction function[J].Transactions of Tianjin University,2015,21(1):41-49.
[21]常士骠,张苏民.工程地质手册[M].北京:中国建筑工业出版社,2007.CHANG Shi-biao,ZHANG Su-min.Manual of engineering geology[M].Beijing:China Architecture&Building Press,2007.
[22]COMPANELLA R G,WICKREMESINGHE D,ROBERTSON P K.Statistical treatment of cone penetrometer test data[C]//The Fifth International Conference on Applications of Statistics and Probability in Soil and Structural Engineering.Canada;[s.n.],1987.