Abstract: To comprehensively evaluate the improvement effects of cement improvement on mechanical properties of argillaceous-slate coarse-grained soil, cyclic dynamic loading and monotonic loading tests under undrained condition are conducted using large-scale static-dynamic triaxial apparatus. The cyclic dynamic responses of the modified soil and the static and dynamic properties under the monotonic loading with medium and low strain rates are examined. The results show that, in cyclic loading tests, both the confining pressure and the loading frequency are the key factors influencing the dynamic elastic modulus and the damping ratio, respectively. The dynamic strength under cycle loading decreases in logarithmic scale with cycle number. The ratio of dynamic strength to static strength of cement-improved argillaceous-slate coarse-grained soil under monotonic loading increases significantly with the strain rate increasing. Compared with the properties of untreated soil, stiffness of improved raises remarkably whereas viscous damping decreases. The effect of strain rate on strength under monotonic loading becomes remarkable. The static strength also increases greatly. There is no difference in the internal friction angles in soil treatment while the cohesion increases significantly through the cement.

Key words: soil mechanics, strain rate effects, cycle loading, monotonic loading, dynamic elastic modulus, damping ratio