应变控制下舟山岱山海相软土动弹性模量及阻尼比试验研究

 为探究舟山岱山海域海底岩土地质层动力学特性，借助GDS动三轴系统对应变控制循环荷载作用下舟山原状海相软土动弹性模量和阻尼比变化规律进行研究。得到舟山岱山海相软土动应力、动应变、动孔压时程曲线以及应力–应变关系曲线，讨论各围压下动弹性模量和阻尼比随动应变幅值的变化趋势。结果表明：舟山岱山海相软土的应力–应变关系曲线为不完全封闭的滞回圈；循环加载过程中土样发生应变软化；同级加载下动弹性模量和阻尼比数据点围绕某恒值作小幅波动，故可采用代表该恒值的均值来表征该级加载下的动弹性模量和阻尼比，由此所得的各围压下动弹性模量–动应变幅值、阻尼比–动应变幅值关系曲线呈收敛趋势；由修正Hardin-Drnevich (H-D)模型建立的应变控制下舟山岱山海相软土动弹模及阻尼比归一化模型可揭示深海环境中海相土受围压影响的动力学机制。将共振柱试验结果与动三轴研究作比较，得到结论：两类试验成果可以互为补充，前者可揭示海相土的弹性特征，后者可反映海相土弹塑性阶段的动力学特性；舟山岱山海相软土在两类试验中均对围压敏感。

DYNAMIC ELASTIC MODULI AND DAMPING RATIOS OF MARINE SEDIMENTS AT ZHOUSHAN DAISHAN BASED ON DYNAMIC TRIAXIAL TESTS UNDER STRAIN CONTROL

The strain controlled dynamic triaxial tests to measure the dynamic moduli and the damping ratios were conducted on intact marine samples from sea area at Daishan，in Zhoushan Archipelago. The experimental results show that the hysteresis curves of Zhoushan Daishan marine sediments are not completely closed loops and are strain softening. The values of dynamic modulus and damping ratio under certain strain amplitude fluctuate around constant values respectively which are designated as the representative values of the dynamic moduli and damping ratios under the corresponding strain amplitude. As such，relationships between dynamic moduli and strain amplitude and between damping ratio and strain amplitude under different confining pressures are established，which converge asymptotically. Hardin-Drnevich(H-D) model is modified to fit the experimental data. Meanwhile，the resonant column tests are conducted to measure the elastic moduli of the marine sediments under wave loading. The results from two tests show that the marine sediments from Daishan are sensitive to the confining pressure.