In order to investigate the influence of the vertical vibration loading on the liquefaction of saturated sand,one dimensional model for the saturated sand with a vertical vibration is presented based on the two phase continuous media theory.The development of the liquefaction and the lique- faction region are analyzed.It is shown that the vertical vibration loading could induce liquefaction. The rate of the liquefaction increases with the increase of the initial limit strain or initial porosity or amplitude and frequency of loading,and increases with the decrease of the permeability or initial modulus.It is shown also that there is a phase lag in the sand column.When the sand permeability distribution is non-uniform,the pore pressure and the strain will rise sharply where the permeability is the smallest,and fracture might be induced.With the development of liquefaction,the strength of the soil foundation becomes smaller and smaller.In the limiting case,landslides or debris flows could occur.
The formation mechanism of ＂water film＂ （or crack） in saturated sand is analyzed theoretically and numerically. The theoretical analysis shows that there will be no stable ＂water film＂ in the saturated sand if the strength of the skeleton is zero and no positions are choked. It is shown by numerical simulation that stable water films initiate and grow if the choking state keeps unchanged once the fluid velocities decrease to zero in the liquefied sand column. The developments of ＂water film＂ based on the model presented in this paper are compared with experimental results.
