循环荷载水平与加载频率耦合作用下的软粘土特性研究

通过不排水循环三轴试验,并考虑不同循环应力水平及加载频率的影响,研究了软粘土在循环荷载作用下的孔隙水压力及变形特性,分别探讨了这些特性随循环加载时间和加载次数的不同变化规律。研究结果表明,对于相同循环应力水平,相同加载次数下不同加载频率的软粘土特性有所不同,而相同加载时间下不同加载频率的软粘土特性基本相同。此外,无论加载频率为何数值,一旦循环应力水平超过临界值,软粘土破坏必将发生。为了深入研究应力水平和加载频率的耦合作用,该文从应力控制循环加载试验中的应变速率着手,对软粘土的特性进行了分析。结果表明,在应力水平相同的情况下,软粘土在不同加载频率下的应变速率是基本相同的,由此可得对于软粘土在循环荷载作用下特性的影响,应力水平比加载频率更为重要。

EXPERIMENTAL STUDY OF THE COMBINED EFFECT OF CYCLIC STRESS LEVEL AND LOADING FREQUENCY ON THE PERFORMANCE OF SOFT CLAYS

Undrained cyclic triaxial tests were conducted on soft clay to investigate the combined effect of cyclic stress level and loading frequency on the generation of excess pore water pressures and axial strains with the number of loading cycles or time. The results indicate that for a given cyclic stress level, the soil properties under various loading frequencies are slightly different if an identical number of loading cycles is considered, whereas they do not deviate from each other if an identical time is considered. In addition, failure occurs when the cyclic stress level exceeds a critical value irrespective of the loading frequency. The combined effect of a cyclic stress level and a loading frequency was studied by analyzing the strain rate in this stress-controlled cyclic loading test. It is shown that for a given cyclic stress level, the strain rate at various loading frequencies are almost same, implying that the influence of a cyclic stress level on the soft clay behavior is stronger compared to a loading frequency.