中文摘要：

利用浙江大学5Hz空心圆柱扭剪仪，通过轴力和扭矩的耦合，模拟波浪荷载下主应力轴动态旋转的应力路径，对杭州原状软黏土的孔压累积、应变发展及模量衰减等动力特性进行研究，研究频率、循环应力比的影响，并与动三轴试验相比较。通过对试验数据的回归分析，给出主应力轴动态旋转下原状软黏土模量衰减的经验公式。结果表明：频率越低或循环应力比越大，孔压累积、应变发展及模量衰减的速率越快，破坏所需要的循环次数越少；虽然各应变分量开展程度不同，但应变曲线均在同一循环次数时出现拐点；循环加载过程中，压缩模量和剪切模量的衰减规律基本相同，但压缩模量衰减速率稍快于剪切模量。与动三轴试验结果相比，主应力轴连续旋转试验中土体模量衰减规律基本不变，但衰减速度更快，试样破坏所需的循环次数明显减少，因此，建议实际工程应用时要考虑主应力轴旋转的影响。

英文摘要：

Dynamic principal stress rotation tests were conducted on Hangzhou intact soft clay by ZJU-5 Hz hollow cylinder apparatus. The stress paths achieved by coupling variation of axial force and torque were designed to simulate wave loading. Dynamic properties such as pore water pressure accumulation, strain development and modulus degradation were investigated. The influence of frequency, cyclic stress ratio and continuous rotation of principal stress axes were studied and the results were compared with dynamic triaxial tests. Finally, an empirical equation for dynamic modulus degradation was proposed by the regression analyses. The results showed that the pore pressure accumulated faster at lower frequency or higher stress ratio. Similar phenomenon were found in strain development and modulus degradation, and specimen approached failure at fewer cycles. Big differences in strain development were noticed while the turning points appeared at the same cycles. The compression modulus degraded in the similar mode of shear modulus but with faster speed. Compared with the results of dynamic triaxial tests, the attenuation law remained unchanged, but compression and shear modulus decreased rapidly and the cycles corresponding to sample failure reduced significantly. Therefore, it is recommended that the impact of the principal stress axes rotation should be taken into account in practical engineering.