Abstract: A vacuum compression device is developed for preparing silt soil samples with different strengths, and triaxial test is performed for measuring liquefaction characteristics of those soil samples. The relationship between soil strength and cyclic shear stress ratio, pore pressure growth model and its parameters are established; and the impact of the soil strength and the dynamic stress on the liquefaction is discussed. Some conclusions are drawn as follows. (1) During soil samples preparation in the vacuum compression device, excess pore pressure dissipated completely within 24 hours, penetration resistance up to 300-400 N; undrained shear strength up to 8 kPa, reached weak soil strength at the Yellow River estuary. (2) The relationship between soil strength and cyclic shear stress ratio is basically linear; and the higher soil strength, curve of pore pressure on the growth showing the more convex trend, the greater pore pressure ratio reached when destroyed. (3) Index model can better simulate pore-water pressure growth of silt at the Yellow River estuary, where the parameters a and b are located between 0.77-5.63 and 0.17-4.65, respectively; for the pore pressure ratio upper limit, the parameters a and b are 0.92 and 4.65 respectively; for pore pressure lower limit, the parameters a and b are 1.25 and 0.89 respectively.

Key words: Yellow River estuary, silt, liquefaction, strength