【摘要】 砂砾土的地震液化至今仍存较大的争议,相应的液化机理解释主要沿用传统的砂土液化分析思路和方法。利用动态圆柱扭剪仪开展了100 mm直径、3组典型级配(含砾量分别为37%,45%和60%)的饱和砂砾土试样循环动三轴实验。基于实验得到的应力–应变率关系曲线,定义了反应饱和砂砾土流动性的平均流动系数和流动性水平。实验发现,初始动应力比对不同含砾量下的平均流动系数–孔压比关系曲线无影响;相对密度越大、含砾量越大,饱和砂砾土的流动性水平越低;有效固结压力对饱和砂砾土平均流动系数–孔压比关系曲线的影响与含砾量相关。推测饱和砂砾土在循环荷载下的流动性由其粗粒接触状态和数量决定;粗粒间的接触在高孔压状态下不能顺利解除是饱和砂砾土与饱和细粒土抗液化性能的本质区别。提出的基于流动性的饱和砂砾土液化机理较好地解释了以上现象。更多还原

【Abstract】 There is still much controversy over earthquake liquefaction of gravelly soils,and the mechanism explanation about earthquake liquefaction of saturated gravelly soils is similar to that of sand liquefaction. The cyclic dynamic triaxial experiments on some saturated gravel samples with 3 groups of typical gradations(gravel contents of 37%,45% and 65%) and the diameter of 100 mm are carried out by employing the dynamic hollow cylinder apparatus. Based on the relationship curves of the shear stress-strain rate from experimental results,an obvious phenomenon is discovered that the saturated gravelly soils possess the similar curve characteristics with the saturated sands. The curve shape is altered from the elliptical shape under low pore water pressure state to the dumbbell one under high pore water pressure state. According to this phenomenon,the average flow coefficient and fluidity level describing the flowing property of the saturated gravelly soils are defined. The influences of the initial dynamic stress ratio,effective consolidation pressure,relative dense and gravel content on the relationship curves between the average flow coefficient and the pore water pressure ratio are discovered and discussed. The experimental results show that the initial dynamic stress ratio has little effects on the relationship between the average flow coefficient and the pore water pressure ratio. The flow level of saturated gravelly soils decreases as the relative density or gravel content increases. The influences of effective consolidation pressure on the relationship curves between the average flow coefficient and the pore water pressure ratio are relative to the gravel content. It is conjectured that the fluidity of saturated gravelly soils under cyclic loading should be determined by the contact state and the scale between gravels in the soils. It might be the fundamental distinction between the anti-liquefaction performance of saturated gravelly soils and sands that the contact state between gravels can not be released favorably under high pore water pressure. A new mechanism of the liquefaction of the gravelly soils is proposed and used to interpret those phenomena mentioned above.更多还原