Abstract: Dynamic triaxial test is performed to study dynamic strain amplitude of Qinghai-Tibet frozen clay and Lanzhou loess under staged dynamic loading with different loading frequencies, confining pressures and negative temperature conditions. The results show that the dynamic strain amplitude is basically unchanged with increasing vibration cycles under the same load level; and average values are used to characterize dynamic strain amplitude. The law of that dynamic strain amplitude changes with dynamic stress amplitude are the same; namely dynamic strain amplitude increases with increasing of dynamic stress amplitude with different loading frequencies, confining pressure and negative temperature conditions. Dynamic strain amplitude decreases with increasing of loading frequencies, but the decreased rate is becoming more and more small that it tends to be a stable value, which increases with the increasing of loading series. With increasing of confining pressure, dynamic strain amplitude for Qinghai-Tibet clay is basically unchanged and for Lanzhou loess decreases gradually. Dynamic strain amplitude decreases with decreasing temperature. The most important effect on dynamic strain amplitude is dynamic stress amplitude, vibration frequencies of dynamic load secondly, temperature thirdly, and confining pressure with minimal impact.

Key words: Qinghai-Tibet frozen clay, Lanzhou loess, dynamic triaxial test, stage loading, dynamic stress amplitude, dynamic strain amplitude