不排水循环荷载作用过程中累积孔压对细砂弹性剪切模量G_(max)的影响

Effect of accumulated pore pressure on shear modulus G_(max) of saturated fine sand during undrained cyclic loading

在土工结构物地震有效应力分析中,往往采用Hardin经验公式计算动荷作用过程中由于孔压变化对砂土初始弹性剪切模量Gmax的影响,但由于以往试验手段的限制,这种方法的有效性至今没有得到验证。为此,采用多功能三轴仪和压电陶瓷弯曲元剪切波速测试系统,研究了不排水循环荷载过程中孔压对细砂Gmax的影响。试验结果表明,细砂Gmax可由Hardin型经验公式计算,但材料参数应通过试验确定;不排水循环荷载作用过程中,细砂Gmax随孔压上升而降低,其值可由其实际平均有效应力和固结后的孔隙比通过由试验得到的Hardin型经验公式计算。

The Hardin equation (1968) is usually adopted to calculate the elastic shear modulus Gmax of the saturated sand during earthquake in the dynamic effective stress analysis of soil structure. But the validity has not been confirmed because of the limitation of test facilities before. The effect of accumulated pore water pressure on Gmax is investigated based on a series of cyclic triaxial tests with piezoceramic bender element system. The test results indicate that the elastic shear modulus Gmax of fine sand can be calculated from the Hardin equation, but the material parameter must be determined by tests; and the elastic shear modulus decreases with the increase of pore water pressure and can also be calculated from the Hardin equation by adopting the actual average effective stress and void ratio during undrained cyclic loading.