Abstract: Basic properties and microstructures of two typical silty clays collected along Beijing-Tianjin high-speed railway and Hangzhou metro line are studied. Using triaxial testing apparatus by GDS Company, static tests under consolidated undrained condition and dynamic tests under high cycles for simulating long-term traffic loading are carried out on these two soils. The undrained static strength, dynamic strength, critical dynamic stress ratio, development of accumulated dynamic strain, and shear strength after vibration of both soils have been studied for comparison. It is found that the soil along the Hangzhou metro line is with high water content, low density, large void ratio, which leads to weak strength and high sensitivity compared with those of Beijing-Tianjin’s. After small amplitude cyclic loading, both of the undisturbed specimens behave higher shear strength than that under static condition, while after large amplitude cyclic loading, vice versa. The remolded specimens always show a strength reduction after cyclic loading, no matter the amplitude of dynamic loading.

Key words: traffic loading, dynamic triaxial test, scanning electron microscope, residual strain, shear strength after dynamic loading