Study of microstructures of soft clay under dynamic loading considering effect of cyclic stress ratio and frequency

The fractal theory is used to study the microstructure of Hangzhou intact clay under wave loading by scanning electron microscope (SEM) and PCAS quantitative testing technology. The characteristics and variation of pores distribution under different cyclic stress ratios and different frequencies are investigated. The study results show that fewer cycles are required at higher stress ratio or lower frequency when the specimen approached failure. The levels of critical failure strain tend to increase with the increasing of cyclic stress ratio, but almost the same under different frequencies. The characteristics of pore distribution such as scale, arrangement and pattern would change regularly with the cyclic stress ratio; but no apparent regularity varies with frequency. Both contraction and dilatation exist on the shear band, caused by the pores which are broking while merging at the same time under cyclic shear stress; also, the pore's orientation is consistent with the shear band's direction. According to the variation of microstructure characteristic parameters before and after cyclic loading, the effects of cyclic stress ratio and frequency on microstructure of soft clay under wave loading are revealed; and the microscopic mechanism of wave loading is disclosed.