A large earthquake may lead to the generation of excess pore water pressure in soils. With the increasement of excess pore water pressure, the stiffness degradation may lead to noticeable levels of deformation even without liquefaction. More than 20 cyclic triaxial tests were conducted in this study to investigate the stiffness degradation of soils during loading under an undrained condition. These tests involved four variables: cyclic stress ratio, void ratio, loading frequency, and fine particle concentration. The test results indicated that the average axial strain in the first cycle determined the degradation path of soils. The average axial strain in the first cycle changed in response to the variation in void ratio and cyclic stress ratio. By adding fine particles, we found that the equivalent granular void ratio was more effective in modeling the collected data on the average axial strain in the first cycle than the void ratio was. The relationships among average axial strain in the first cycle, cyclic stress ratio, and equivalent granular void ratio were investigated. Excess pore water pressure is a factor that is usually considered to weaken soils. A simple stiffness degradation model was proposed as a function of the excess pore water pressure ratio. This model was further transformed as a function of the factor of safety against liquefaction. The average axial strain in the first cycle and the stiffness degradation ratio were used to evaluate the developing axial strain in the degradation process.

大地震可能会导致土壤中产生过多的孔隙水压力。随着过量孔隙水压力的增加，即使没有液化，刚度降低也可能导致明显的变形水平。在这项研究中进行了20多次循环三轴试验，以研究不排水条件下土壤在加载过程中的刚度退化。这些测试涉及四个变量：循环应力比，空隙比，加载频率和细颗粒浓度。试验结果表明，第一个循环的平均轴向应变决定了土壤的降解路径。响应于空隙率和循环应力比的变化，第一循环中的平均轴向应变发生了变化。通过添加细颗粒，我们发现，等效的颗粒空隙率在建模第一个循环的平均轴向应变数据方面比空隙率更有效。研究了第一个循环中的平均轴向应变，循环应力比和等效颗粒空隙率之间的关系。孔隙水压力过高通常被认为是削弱土壤的一个因素。提出了一个简单的刚度退化模型，作为过量孔隙水压力比的函数。该模型根据抗液化的安全系数进一步进行了转换。使用第一周期的平均轴向应变和刚度退化比来评估退化过程中发展中的轴向应变。研究了第一个循环中的平均轴向应变，循环应力比和等效颗粒空隙率之间的关系。孔隙水压力过高通常被认为是削弱土壤的一个因素。提出了一个简单的刚度退化模型，作为过量孔隙水压力比的函数。该模型根据抗液化的安全系数进一步进行了转换。使用第一周期的平均轴向应变和刚度退化比来评估退化过程中发展中的轴向应变。研究了第一个循环中的平均轴向应变，循环应力比和等效颗粒空隙率之间的关系。孔隙水压力过高通常被认为是削弱土壤的一个因素。提出了一个简单的刚度退化模型，作为过量孔隙水压力比的函数。该模型根据抗液化的安全系数进一步进行了转换。使用第一周期的平均轴向应变和刚度退化比来评估退化过程中发展中的轴向应变。提出了一个简单的刚度退化模型，作为过量孔隙水压力比的函数。该模型根据抗液化的安全系数进一步进行了转换。使用第一周期的平均轴向应变和刚度退化比来评估退化过程中发展中的轴向应变。提出了一个简单的刚度退化模型，作为过量孔隙水压力比的函数。该模型根据抗液化的安全系数进一步进行了转换。使用第一周期的平均轴向应变和刚度退化比来评估退化过程中发展中的轴向应变。