Experimental study on dynamic elastic modulus of frozen soils under stepped axial cyclic loading

Based on the viscoelastic theory, the slope of the middle straight line in the hysteresis curve is adopted to define dynamic elastic modulus. Dynamic triaxial tests are employed to study the variation tendency of dynamic elastic modulus with dynamic strain amplitude varing under different vibration frequencies, confining pressures and negative temperatures conditions. The results show that the dynamic elastic modulus values of Qinghai-Tibet clay range from 393 to 1749 MPa, and those of Lanzhou loess range from 101 to 713 MPa with vibration frequencies of 0.10007E;20 Hz, confining pressure of 0.30007E;2 MPa and negative temperatures of -0.20007E;-2℃. Because the dynamic elastic modulus changes slightly with the increasing vibration cycles at the same loading level, the average value is adopted. The dynamic elastic modulus tends to be stable eventually with the increasing dynamic strain amplitude. The stable value of dynamic elastic modulus increases with the increasing vibration frequencies and decreasing temperatures. When the confining pressure changes, the stable value of dynamic elastic modulus changes without unified law.