概率性分析在黄土场地动力沉降评价中的应用
摘要
天然黄土动残余应变研究主要依赖室内动三轴试验,如何将有限室内试验数据合理地应用于场地动力沉降的定量评价,是岩土地震工程领域中研究涉足尚少的重要科学问题。应用概率统计与蒙特卡洛模拟等非确定性分析方法,借助综合考虑固结应力、结构强度、空间体积特性和地震动荷载等动残余应变关键影响参量的估算模型,提出有效弱化土体物性参量不确定性(离散性与随机性)的场地动力沉降概率性评价的思路与方法。应用结果显示,利用该方法得出的场地动力沉降的概率分布特征,能够反映天然黄土动残余应变的基本认知特点,对明晰地震作用下天然黄土场地精细动力沉降特性以及据此采用适当合理的地基处理方法,具有理论意义与实用价值。
Dynamic triaxial test in laboratory is the main approach to investigate the dynamic residual strain(seismic subsidence) of natural loess under seismic loadings.How to reasonably apply the little test data in laboratory into the quantitative evaluation of dynamic settlement in loess field is one key problem within the practice of geotechnical earthquake engineering.Based on a magnitude estimation model for dynamic residual strain of natural loess,which comprehensively considers the critical influence parameters of the dynamic subsidence,consolidation stress,structure strength,spatial volume property and seismic loadings,the authors propose a probability-based evaluation method for ground settlement of natural loess under seismic loadings by means of theoretical analysis methods of probability statistics and Monte Carlo simulation.For the application of this new probability-based evaluation method,here,we provide one practical case on a typical loess field.The relevant Chi-square test show that frequency features of the four critical parameters influencing dynamic residual strain of natural loess determined by the above-mentioned theoretical model could be described by normal distribution.In order to minimize the uncertainties(scattering and randomness) of physico-mechanical property of the soil,furthermore,Monte Carlo simulation technique is adopted to extend the laboratory data into huge numbers.Then the corresponding huge numbers of dynamic residual strain of natural loess in the case field calculated by the evaluation method could be used to analyze the probability features of dynamic settlement behaviors of the loess ground.According to occurrence probabilities of different magnitude-grades of dynamic settlement,we could acquire the detailed behaviors of dynamic residual strain of natural loess in the target field under seismic loadings.The probability distribution reveals that the quantitative evaluation method reported here can obviously decrease the influence of parameter uncertainty associated with the soil.Meanwhile,those probability characteristics of dynamic settlement in the example field accord with the existing basic-behavior knowledge of dynamic residual strain of natural loess under seismic loadings.These results mean that the probability method could provide a better/reasonable reference not only to understand dynamic settlement behaviors of natural loess ground under seismic loadings,but also to select the proper treatment method for the potentially dangerous ground.
Dynamic triaxial test in laboratory is the main approach to investigate the dynamic residual strain(seismic subsidence) of natural loess under seismic loadings.How to reasonably apply the little test data in laboratory into the quantitative evaluation of dynamic settlement in loess field is one key problem within the practice of geotechnical earthquake engineering.Based on a magnitude estimation model for dynamic residual strain of natural loess,which comprehensively considers the critical influence parameters of the dynamic subsidence,consolidation stress,structure strength,spatial volume property and seismic loadings,the authors propose a probability-based evaluation method for ground settlement of natural loess under seismic loadings by means of theoretical analysis methods of probability statistics and Monte Carlo simulation.For the application of this new probability-based evaluation method,here,we provide one practical case on a typical loess field.The relevant Chi-square test show that frequency features of the four critical parameters influencing dynamic residual strain of natural loess determined by the above-mentioned theoretical model could be described by normal distribution.In order to minimize the uncertainties(scattering and randomness) of physico-mechanical property of the soil,furthermore,Monte Carlo simulation technique is adopted to extend the laboratory data into huge numbers.Then the corresponding huge numbers of dynamic residual strain of natural loess in the case field calculated by the evaluation method could be used to analyze the probability features of dynamic settlement behaviors of the loess ground.According to occurrence probabilities of different magnitude-grades of dynamic settlement,we could acquire the detailed behaviors of dynamic residual strain of natural loess in the target field under seismic loadings.The probability distribution reveals that the quantitative evaluation method reported here can obviously decrease the influence of parameter uncertainty associated with the soil.Meanwhile,those probability characteristics of dynamic settlement in the example field accord with the existing basic-behavior knowledge of dynamic residual strain of natural loess under seismic loadings.These results mean that the probability method could provide a better/reasonable reference not only to understand dynamic settlement behaviors of natural loess ground under seismic loadings,but also to select the proper treatment method for the potentially dangerous ground.
引文
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[11]王兰民,孙军杰,徐舜华,等.爆破模拟地震动条件下黄土场地震陷研究[J].岩石力学与工程学报,2008,27(5):913-921.WANG Lan-min,SUN Jun-jie,XU Shun-hua,et al.Characteristics of seismic subsidence of loess site inducedby blasting ground motion[J].Chinese Journal of RockMechanics and Engineering,2008,27(5):913-921.
[2]沈珠江.非饱和土力学实用化之路探索[J].岩土工程学报,2006,28(2):256-259.SHEN Zhu-jiang.Exploitation of practical use ofunsaturated soil mechanics[J].Chinese Journal ofGeotechnical Engineering,2006,28(2):256-259.
[3]谢定义.21世纪土力学的思考[J].岩土工程学报,1997,19(4):111-114.XIE Ding-yi.The thinking of development of soilmechanics in the 21st Century[J].Chinese Journal ofGeotechnical Engineering,1997,19(4):111-114.
[4]黄雨,叶为民,唐益群,等.上海深厚饱和覆盖土层的动力耦合地震反应分析[J].岩土力学,2002,23(4):411-416.HUANG Yu,YE Wei-min,TANG Yi-qun,et al.Coupledseismic response analysis of deep saturated soil coveringlayers in Shanghai[J].Rock and Soil Mechanics,2002,23(4):411-416.
[5]王建华.软土地基震陷的弹塑性分析[J].天津大学学报,1996,29(3):336-341.WANG Jian-hua.Elastoplastic analysis on seismicsettlement of soft clay foundation[J].Journal of TianjinUniversity,1996,29(3):336-341.
[6]李宁,程国栋,谢定义.西部大开发中的岩土力学问题[J].岩土工程学报,2001,23(3):268-272.LI Ning,CHENG Guo-dong,XIE Ding-yi.Geo-mechanics development in civil construction in WesternChina[J].Chinese Journal of Geotechnical Engineering,2001,23(3):268-272.
[7]孙军杰,徐舜华,王兰民,等.非饱和黄土动残余应变关键影响参量与量值估算[J].岩石力学与工程学报,2012,31(2):382-391.SUN Jun-jie,XU Shun-hua,WANG Lan-min,et al.Critical influence parameters and magnitude estimation ofdynamic residual strain of unsaturated loess[J].ChineseJournal of Rock Mechanics and Engineering,2012,31(2):382-391.
[8]沈珠江.广义吸力和非饱和土的统一变形理论[J].岩土工程学报,1996,18(2):1-9.SHEN Zhu-jiang.Generalized suction and unifieddeformation theory for unsaturated soil[J].ChineseJournal of Geotechnical Engineering,1996,18(2):1-9.
[9]王兰民.黄土动力学[M].北京:地震出版社,2003:47-63.
[10]谢定义.试论我国黄土力学研究中的若干新趋向[J].岩土工程学报,2001,23(1):3-13.XIE Ding-yi.Exploration of some new tendencies inresearch of loess soil mechanics[J].Chinese Journal ofGeotechnical Engineering,2001,23(1):3-13.
[11]王兰民,孙军杰,徐舜华,等.爆破模拟地震动条件下黄土场地震陷研究[J].岩石力学与工程学报,2008,27(5):913-921.WANG Lan-min,SUN Jun-jie,XU Shun-hua,et al.Characteristics of seismic subsidence of loess site inducedby blasting ground motion[J].Chinese Journal of RockMechanics and Engineering,2008,27(5):913-921.
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