循环荷载波形变化对天津滨海软土刚度软化特性的影响

Effect of cyclic loading waveforms on stiffness softening characteristics of soft soil in Tianjin Binhai New Area

为研究循环荷载波形对结构性软土刚度软化的影响,以天津滨海新区天津港保税区海积软土为研究对象,对其施加不同波形、不同幅值的循环荷载。试验结果表明:当循环荷载应力幅值较小时,软土刚度软化速率慢,不同波形循环荷载对软土刚度软化影响差别不大;当循环荷载较大时,软土刚度软化速率加快,荷载波形变化对结构性软土刚度软化速率影响明显,其中方波循环荷载作用下软土刚度软化的速率最大,正弦波次之,三角波最小。通过对比分析不同波形、不同应力幅值荷载作用下软土软化指数衰减曲线,得到综合考虑荷载波形和应力幅值的软化指数经验公式。

In order to investigate the effect of cyclic loading waveforms on stiffness softening of structural soft soil,marine soft soil samples taken from Tianjin Harbor Bonded Area in Tianjin Binhai New Area will subject to cyclic loadings with varying waveforms and amplitudes. It is observed that the effects of varying loading waveforms like square wave,sinusoidal wave, and triangular wave do not have an apparent influence on the rate of stiffness softening when the loading amplitude is below the threshold stress. On the contrary, when the amplitude is much higher than the threshold,the rate of stiffness degradation for square wave is the fastest,and sinusoidal wave comes the second,while triangular wave is the last. Analyses are conducted on softening indices degradation curves under cyclic loadings with varying waveforms and amplitudes. Finally, the expression of softening index degradation considering both loading waveforms and stress amplitude is obtained.