Experimental Study on Strength Weakening of Silty Soil of Subaqueous Yellow River Delta Under Cyclic Loadings

Silty soil seabed of Yellow River Delta is prone to sliding and liquefaction, which usually leads to geological hazards including landslides of seabed and failures of marine structures. The failure of silty soil is closely correlated with its strength change induced by wave actions. In this paper, silty soil samples of various clay contents were prepared, and cyclic triaxial experiments modeling wave actions were carried out on the samples to study the relationship between cyclic shear stress and number of cycles of silty soil taken from Subaqueous Yellow River Delta. Research results indicated that there existed a critical value in the cyclic stress exerting on the soil; the cyclic stress could cause failure of soil only when it’s value was higher than that of the critical stress; in this paper, critical cyclic stress ratio was defined as K_cr = ((σ_d+σ₁)/σ₃)_cr, where K_cr is critical cyclic stress ratio, σ_d is axial pressure, σ₁ is cyclic stress, σ₃ is confining pressure. For the sake of the safety of design and construction of marine engineering structures, 1.30 was taken as the critical cyclic stress ratio of remolded silty soil in the Yellow River Delta, and 1.40 as that of the undisturbed silty soil. Also the results show that the dynamic strength weakening of silty soil followed the rule of power function attenuation. In addition, cyclic loading vibration experiments in a soil tank were carried out to study the weakening law of shear strength and penetration resistance with the variation of oscillation times.