应力、应变控制下压实黄土动力特性研究

Dynamic Characteristics of Compacted Loess under Controlled-stress and Controlled-strain Modes

摘要:

基于动三轴试验研究了不同围压条件下，加载控制方式对压实黄土动应力应变关系的影响规律，对比了不同控制方式下压实黄土的动应力应变时程曲线的差异。研究表明：压实黄土的动应力应变关系符合双曲线模型；加载控制方式不会改变压实黄土骨干曲线的类型，但会显著影响拟合参数的大小。相同围压下，采用应变控制测定的初始动模量较小；随着围压的增大，应变控制下初始动模量随围压的增长速率反而越小，二者之间的差距越来越大。应力控制和应变控制加载过程中，动模量在某一振级下随着动循环次数的增加而逐渐衰减，且应力控制方式下衰减的幅度较大。对于土体结构受力较为敏感的原状土，使用应变控制加载方式可能会获得更为准确的试验结果。

Abstract:

In this study, we performed dynamic triaxial tests to investigate the effect of loading control mode on the dynamic stress-strain relationship of compacted loess at different confining pressures. We also compared the time-history differences between the dynamic stresses and strains of samples under controlled-stress and controlled-strain modes. The results indicate that the dynamic stress-strain relationship in compacted loess accords with that of the hyperbolic model and that the control mode does not change the type of backbone curve of the compacted loess, but significantly affects the fitting parameters. At the same confining pressure, the initial dynamic modulus obtained by strain-control is smaller than that obtained by stress-control. The growth rate of the initial dynamic modulus obtained by strain-control is relatively small and the gap between the two modes increases with increases in the confining pressure. In the process of stress-control and strain-control loading, the dynamic modulus decreases with increases in the loading cycles at a certain load, and the attenuation amplitude is greater under the stress-control mode than under the strain-control mode. For undisturbed soil with a more sensitive soil structure, more accurate test results can be obtained using the strain-control mode.