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通过对石碑塬黄土进行室内动三轴液化试验,研究不同动荷载水平下不同层位黄土的动应变和孔隙水压力发展特征,分析海原地震中石碑塬黄土地震液化的机制,并根据黄土所具有的特殊性质,探讨饱和黄土液化的判别标准。结果表明:饱和黄土液化时孔隙水压力发展受动荷载、颗粒组成和塑性指数等多因素的影响,相对于动残余应变的发展具有滞后性,因此往往达不到有效围压;而动残余应变的发展特征主要受初始孔隙比的影响,且当其超过3%后急剧增大,因此可选取该应变作为饱和黄土液化破坏的判别标准。
Through the dynamic triaxial liquefaction tests on the loess in Shibeiyuan area, the dynamic strain and pore water pressure development characteristics of loess at different layers under different dynamic load are studied. The mechanism of loess earthquakes liquefaction in Shi Bei Yuan of Haiyuan earthquake is analyzed. This paper discusses the criterion of liquefaction of saturated loess. The results show that the pore water pressure in liquefaction process of saturated loess is affected by many factors, such as dynamic load, particle composition and plasticity index, which lags behind the development of dynamic residual strain. Therefore, the effective confining pressure is often not reached. The development characteristics are mainly affected by the initial porosity ratio, and when it exceeds 3%, it increases sharply. Therefore, this strain can be selected as the criterion for liquefaction damage of saturated loess.