Abstract: Desaturation is a method to improve the liquefaction resistance of ground by decreasing the degree of saturation of saturated sandy soils. A simplified single-phase fluid numerical method considering water-air flow in desaturated sand as a saturated pore fluid, a modified single-phase fluid numerical method is proposed to investigate the static liquefaction behavior considering the change of pore fluid bulk modulus. The numerical simulations of the undrained triaxial test are carried out in this study. By comparing the numerical results with laboratory tests, it indicates that the modified method can predict static liquefaction performance of saturated sand accurately. Moreover, some conclusions are obtained from numerical results of different methods, namely, simplified single-phase fluid method, modified single-phase fluid method, and two-phase flow method. First, the initial value of pore fluid bulk modulus will have a significant impact on the prediction of the undrained behavior of desaturated sand in simplified single-phase fluid numerical method due to the constant pore fluid bulk modulus. When the initial value of pore fluid bulk modulus increases from 100 kPa to 200 kPa, the peak deviator stress can decrease by 30% and the pore pressure can increase by 40%. Second, the stress-strain response and volumetric strain curve of modified method agree with that of two-phase flow method and the error is less than 5%. Overall, the modified numerical method is a simple and reasonable method for describing the static liquefaction of desaturated sand.

Key words: desaturation method, modified single-phase fluid numerical method, bulk modulus of pore fluid, static liquefaction