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为了研究饱和砂土动剪切模量在振动孔隙水压力(简称孔压)升高和消散阶段的变化规律,开展了饱和南京细砂的大型振动台试验研究。基于试验数据,分析了加速度二次积分时合理选择带通滤波的低频和高频阀值的重要性,提出了由土层加速度时程确定土体动剪切模量的方法。分析孔压升高和消散阶段土体的动剪切模量比与循环周数、孔压比、剪应变幅值的关系,结果表明:与孔压升高阶段相比,孔压消散阶段的动剪切模量比明显要低,将孔压升高与消散阶段的土体动剪切模量视为相同是不合适的;大型振动台试验给出的饱和南京细砂动剪切模量比随剪应变幅值增大而衰减的速度大于室内循环三轴试验给出的结果。
In order to study the variation law of dynamic shear modulus of saturated sand in the stage of rising and dissipating of pore water pressure, a large-scale shaking table experiment of saturated fine sand was carried out. Based on the experimental data, the importance of choosing the low-frequency and high-frequency thresholds for the reasonable selection of band-pass filter is analyzed. The method for determining the dynamic shear modulus of soil from the acceleration time histories of soil layers is proposed. The relationship between dynamic shear modulus ratio and cycle number, pore pressure ratio and shear strain amplitude was analyzed. The results show that compared with the pore pressure increasing stage, the pore pressure dissipation stage The dynamic shear modulus ratio is obviously lower, it is not suitable to consider the dynamic shear modulus of soil as the same as the pore pressure rise and dissipation phases. The large-scale shaker test gives the saturated dynamic shear modulus of fine sand The rate of decay is greater than the amplitude of shear strain, which is larger than the result of indoor cyclic triaxial test.