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基于黏弹性理论,将动态弹性模量的最大值定义为冻土的动模量,通过计算滞回曲线中直线斜率的方法来计算冻土的动模量。通过动三轴试验,对不同频率、围压和负温条件下冻土的动模量随动应变幅的变化规律进行了试验研究,结果表明:在不同频率(0.1～20 Hz)、围压(0.3～2 MPa)和负温(-0.2～-2℃)条件下,青藏黏土的动模量取值范围为393～1749 MPa,兰州黄土的动模量取值范围为101～713 MPa;同一级加载下,动模量随着振次的增加基本不变,可以采用平均值来表征该级加载下的动模量;对于青藏黏土和兰州黄土,不同频率条件下,动模量随动应变幅的增加最终趋于一稳定值,该稳定值随加载频率的增加而增大;不同温度和围压条件下,随着动应变幅的增加,动模量先减小再趋于一个稳定值,该稳定值随围压的变化较复杂,随温度的降低而增大。
Based on the theory of viscoelasticity, the maximum value of dynamic elastic modulus is defined as the dynamic modulus of frozen soil. The dynamic modulus of frozen soil is calculated by calculating the slope of the line in the hysteretic curve. The dynamic variation of dynamic modulus of permafrost with different frequency, confining pressure and negative temperature was studied by dynamic triaxial test. The results show that the dynamic strain amplitude of permafrost varies with different frequency (0.1 ~ 20 Hz), confining pressure (0.3 ~ 2 MPa) and negative temperature (-0.2 ~ -2 ℃), the range of dynamic modulus of Qinghai-Tibet clay is 393 ~ 1749 MPa and the dynamic modulus of Lanzhou loess is 101 ~ 713 MPa. Under the same stage of loading, the dynamic modulus is basically unchanged with the increase of the vibration times, and the average dynamic modulus can be expressed by the average load. For the Qinghai-Tibet clay and Lanzhou loess, The increase of strain amplitude finally tends to a stable value, which increases with the increase of loading frequency. Under different temperature and confining pressure, the dynamic modulus decreases first and then stabilizes with the increase of dynamic strain amplitude Value, the steady value with the confining pressure changes more complex, with the temperature decreases.