DYNAMIC RESPONSE ANALYSIS OF SATURATED-UNSATURATED DOUBLE-LAYERED SOIL UNDER RECTANGULAR MOVING LOAD¹⁾

Under the assumption that the foundation is a double-layered half-space of saturated-unsaturated soil, the unified dynamic governing equations of the double-layered foundation are constructed and solved by using the theory of continuum mechanics and multiphase porous media. By using Dirac-delta function and Heaviside step function, the action of rectangular moving load is described as an analytic function of temporal and spatial coordinates. Then the load function is substituted into the ground dynamic governing equation, and the equation is solved with Fourier transform. The results are verified by degradation. The dynamic response of saturated-unsaturated soil double-layer foundation is also analyzed. The results show that when the load moving velocity is smaller than the Rayleigh wave velocity, the peak value of the vertical vibration is very small, and the amplitude increases slightly with the increase of the velocity. However, when the load velocity reaches the Rayleigh wave velocity, the vertical vibration increases sharply, and the vertical displacement exhibits peak value many times. The saturation of unsaturated soil and the thickness of soil layer also affect the amplitude of foundation significantly.