中文摘要：

长期循环荷载下，结构性软土的力学变形特性已被广泛研究。但以往的研究主要集中在一种循环荷载波形下结构性软土的动力特性，而原状软土地基实际上承受着不同的外部循环荷载，如地震、高速交通、波浪荷载、油罐及水库液面的升降等，其等效的循环波形不同。通过应力控制式动三轴试验，分别在方形波、三角形波和正弦波3种循环荷载作用下，考虑加载次数、振动幅值、振动频率等因素的影响，对海积结构性软土的动力特性与变形特征进行分析，并类比了在不同循环荷载波形下软土刚度软化性状；通过借鉴由循环剪切模量定义的软化指数，分析出3种波形下软化指数随着振动次数的变化规律，得出在3种循环荷载下海积结构性软土的刚度软化过程。

英文摘要：

Dynamic characteristics of natural soft clay under long-term cyclic loading have been widely studied. However, the previous researches focued on the dynamic characteristics under only one kind of cyclic loading waveform. Different kinds of exterior cyclic loading affect the natural soft clay subgrade, such as earthquakes, high buildings, high speed rails, wave loads, oil tanks, reservoirs and so on, and they demonstrate different wave patterns. Stress-controlled dynamic triaxial tests are performed under the square, triangle, sine cyclic loading, and considering the effects of cyclic numbers, dynamic amplitudes, and frequencies, the dynamic characteristics of natural soft clay are studied and analyzed, and the dynamic characteristics under different cyclic loading waveforms are compared. For comparing the stiffness degradation of soft clay under different cyclic loading waveforms, degradation index defined by cyclic shear modulus is used to analyze the stiffness degradation process.