动荷载作用下冻结兰州黄土的动应变幅变化特征研究

采用分级循环正弦荷载模拟车辆振动, 通过动三轴试验对冻土的动应变幅进行了研究. 结果表明: 对于频率为0.1 Hz的前5级加载和频率≥0.5 Hz的各级加载作用下的动应变幅, 可以采用等价应变幅描述每一级动荷载作用下的动应变幅. 存在一个临界频率(约为7 Hz), 当加载频率小于该临界频率时, 等价应变幅变化复杂; 当加载频率大于该临界频率时, 等价应变幅随加载级数基本保持不变. 当加载频率≥0.5 Hz时,不同加载级数下等价应变幅随加载频率的增大而减小. 围压对等价应变幅影响较小; 当频率≤0.5 Hz时, -0.5 ℃条件下的等价应变幅略大于-1.0 ℃条件下的等价应变幅; 当频率>0.5 Hz时, 不同温度下的等价应变幅近似相等.

Characteristics of Dynamic Strain Amplitude of Frozen Lanzhou Loess under Dynamic Loading

Based on dynamic tri-axial tests at low temperature,dynamic strain amplitude of frozen soil was studied under vehicle vibration load,which was simplified as staged and cyclic sinusoidal load.The research results show that the equivalent dynamic strain amplitude can be used to describe the dynamic strain amplitude under each stage load when the vibration frequency is greater than or equal to 0.5 Hz for each stage load and is equal to 0.1 Hz for the initial five stage loads.The equivalent dynamic strain amplitude is very complicated with the increasing load when the vibration frequency is less than the critical vibration frequency,approximately equal to 7 Hz,and basically remains constant when the vibration frequency is greater than the critical vibration frequency.The equivalent dynamic strain amplitude decreases with increasing vibration frequency when the vibration frequency is greater than or equal to 0.5 Hz.Confining pressure has nearly no impact on the equivalence dynamic strain amplitude.The equivalent dynamic strain amplitude under-0.5 ℃ is slightly greater than that under-1 ℃ when the vibration frequency is less than or equal to 0.5 Hz.The value of the equivalent dynamic strain amplitude is approximately unanimous when the vibration frequency is greater than 0.5 Hz.