Abstract: Saturated silt is prone to liquefaction and deformation under earthquake action, which can lead to severe damage to structures built on it. In natural conditions, saturated silt often experiences initial static shear stress  τ_s . To explore the impact of initial shear stress on the liquefaction characteristics of saturated silt, a series of cyclic torsional shear tests were conducted on liquefied silt, treating it as a fluid. The experimental results showed that the initial shear stress τ_s had a significant impact on the relationship curve of the shear stress-strain rate of saturated silt. When the initial shear stress  τ_s  equals zero, the pattern of the relationship curve transitions from the shape of an ellipse to the shape of a dumbbell as the number of loading cycles N increases. The pattern of the relationship curve successively appears as the shape of a sickle, ellipse, and hammer with increasing initial shear stress  τ_s . Meanwhile, the initial shear stress  τ_s  has a significant influence on the development of the apparent viscosity  η and the average flow coefficient κ⁻  of the saturated silt. As the initial shear stress increased, theκ⁻-N curve decreased first and then increased, while the development speed of the η -N curve showed a trend from fast to slow. Additionally, the excess pore water pressure ratio r_uth  at the solid-liquid phase transformation state first decreased and then increased as the initial shear stress increased. When the initial shear stress reached 5 kPa, the excess pore water pressure ratio of the saturated silt was the lowest.

Key words: saturated silt, initial shear stress, liquefaction flow characteristics, cyclic torsional shear test