分级加载下冻土阻尼比的试验研究

Experimental study of damping ratio of frozen soil under stepwise loading

利用MTS-810型振动三轴试验机对不同加载频率、围压和温度下冻结黏土和冻结黄土的阻尼比变化规律进行研究。结果表明：不同频率、围压和温度下，对于冻结黏土，随动应变幅的增大，阻尼比呈先减小再缓慢增大的变化趋势；对于冻结黄土，阻尼比随动应变幅的增加先减小再逐渐保持不变。相同动应变幅下，冻结黏土和冻结黄土的阻尼比随加载频率的增加而减小，随围压的增加变化不大，温度为-0.2- -1 ℃时，阻尼比的变化规律不明显，温度为-2 ℃时，阻尼比的取值显著小于-0.2- -1 ℃时的阻尼比取值。当动应力水平较低时，阻尼比受频率的影响程度较大；当动应力水平较高时，阻尼比受温度的影响程度较大；在整个加载过程中，阻尼比受围压的影响程度最小。当动应变幅较小时，频率对冻结黄土的影响程度要大于冻结黏土，随动应力水平的增高，冻结黄土受频率的影响程度逐渐小于冻结黏土。在整个加载过程中，温度对冻结黄土的影响程度大于冻结黏土，而围压对冻结黄土的影响程度小于冻结黏土。

The MTS-810 vibration triaxial testing machine is used to study the change law of damping ratio of frozen clay and loess with different loading frequencies, confining pressures and temperatures. The results show that for frozen clay, the damping ratio firstly decreases and then gradually increases with the increase of dynamic strain amplitude under the conditions mentioned above. For frozen loess, the damping ratio firstly decreases and then tends to be a stable value with the increase of dynamic strain amplitude. Damping ratios of frozen clay and frozen loess decrease with the increase of loading frequencies, and changes slightly with the increase of confining pressure under the same dynamic strain amplitude. The change of damping ratio is insignificant with the confining pressure when the temperature is in the range of -0.2 to -1 ℃, the value of damping ratio of frozen soil at the temperature of -2 ℃ is apparently less than that at the temperature of -0.2 to -1 ℃. Damping ratio is greatly affected by frequency at a relatively low dynamic stress level and is greatly affected by temperature at a relatively high dynamic stress level. In the whole loading process, damping ratio is minimally affected by confining pressure. The influence of frequency on frozen loess is greater than that on frozen clay when the dynamic strain amplitude is at relative low level. With the increase of dynamic stress, the influence of frequency on frozen loess is gradually less than that on frozen clay. In the whole loading process, temperature has greater influence on frozen loess than on frozen clay, while confining pressure has less influence on frozen loess than on frozen clay.