液化判别应力折减系数分布特征研究  

STUDY OF DISTRIBUTION FEATURES OF STRESS REDUCTION COEFFICIENT IN LIQUEFACTION EVALUATION

作　　者：韩超[1,2] 周燕国[1,2] 凌道盛[1,2] 陈云敏[1,2] 

机构地区：[1]浙江大学软弱土与环境土工教育部重点实验室,浙江杭州310058 [2]浙江大学岩土工程研究所,浙江杭州310058

出　　处：《岩石力学与工程学报》2010年第9期1833-1839,共7页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家重点基础研究发展计划(973)项目(2007CB714203);国家自然科学基金资助项目(50908207;50778163);中国地震局地震行业科研专项(200808022)

摘　　要：基于FLAC3D软件对饱和砂土离心机振动台模型试验进行数值标定,以获取合理的分析模型,然后采用数值模拟分析不同地震波和简谐波下模型地基内部应力折减系数rd的分布规律。研究表明,已有经验公式能较好地描述土体未液化时应力折减系数的分布形式,但土体液化后土层剪应力分布与经验公式预测值存在显著差别。地震动作用的作用时间对折减系数也有较大影响,其中,孔隙水压力增长水平和土体软化程度是重要影响因素。而地震动频率对rd的影响则主要与场地卓越频率相关,地震动频率越接近场地卓越频率,rd沿土层深度的变化越剧烈。因此,液化评价中采用Seed-Idriss简化公式估算CSR时,需要综合考虑地震动特征和场地条件对rd分布的影响。To investigate the distribution features of rd under different types of excitations,firstly FLAC 3D is used to calibrate the results of dynamic centrifuge tests on saturated sand;and then the validated numerical model is used to study the variation of rd curves with soil depth under seismic and harmonic excitations.The results show that the proposed empirical equation of rd is fairly accurate in non-liquefied cases;whereas larger differences exist between the distribution of shear stresses and the predicted values by empirical equation in liquefied cases.Besides,the duration of seismic excitation also influences rd,where the generation level of pore water pressure and the softening degree of soil are major factors.As for the effect of seismic input frequency,it is closely related to the predominant frequency of the site;i.e.the closer the two frequencies become,the more drastic the variation of rd curve is.Therefore,the effects of seismic motion and site conditions should be considered when the Seed-Idriss equation is used to calculate CSR in liquefaction evaluation.

关 键 词：土力学 液化 地震循环剪应力比 应力折减系数 饱和砂土 数值模拟 离心机试验 

分 类 号：TU431[建筑科学—岩土工程]