Coupling effects of bidirectional cyclic loading and loading frequency on pore water pressure of saturated soft clay
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摘要: 利用GDS变围压动三轴试验系统模拟真实交通荷载下轴向循环正应力与水平循环正应力的耦合作用,对宁波饱和重塑软黏土进行一系列变围压不排水循环加载试验,对循环轴向偏应力和循环围压耦合作用下饱和软黏土的孔压变化规律进行了研究,分析了循环应力比、循环围压及振动频率对孔压的影响。研究结果表明：变围压作用下,孔压随循环应力比、循环围压的增加而增大,随振动频率的增加而减小。不同应力路径斜率、振动频率影响下,孔压率随加载时间的变化规律一致,循环应力比CSR、应力路径斜率η对孔压率-时间关系影响明显,随着循环应力比CSR、应力路径斜率η的增大,孔压率也增大,而振动频率对孔压率-时间关系影响不显著。在上述试验结果基础上得知,估算交通荷载作用下产生的孔压,不能忽视循环围压及振动频率的影响。Abstract: A series of undrained cyclic tests with variable confining pressures are conducted on Ningbo saturated soft clay by using the GDS cyclic triaxial system. In this study, the coupling effects of cyclic deviatoric stress and cyclic confining pressure on the pore water pressure of Ningbo saturated soft clay in real traffic loading are simulated. The developments of pore water pressure of saturated soft clay subjected to bidirectional cyclic loading are investigated with different cyclic stress ratios, cyclic confining pressures and vibration frequencies. It is observed that the pore water pressure increases with higher cyclic stress ratios and cyclic confining pressure, but decreases with higher frequencies under bidirectional cyclic loading. The relationships between pore water pressure ratio and cyclic time are identical under different values of η and frequencies. The slope of stress paths η and cyclic stress ratios CSR affect the relationship between pore water pressure ratio and cyclic time significantly, and the pore water pressure ratio increases with the increase of η and CSR. However, the effect of frequency on the curves of pore water pressure ratio and loading time is indistinct. The observations imply that the coupling effects of cyclic confining pressure and loading frequency on the pore water pressure should also be considered to estimate the values of pore water pressure.
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