This article investigates the problem of Rayleigh (R) waves propagation in double unsaturated soils. Firstly

wave equations of three-phase porous medium are extended by introducing the tortuosity of fluid phases into the conservation of momentum

then decomposed with the aid of Helmholtz theorem and the sum of potential functions of body waves. The dispersion equations are established with the boundary condition and the continuities of soil layers. The influences of saturation degree

tortuosity and cover thickness on the velocity and attenuation are discussed. The results show that the R wave velocity decreases linearly with the saturation

and increases with the intrinsic permeability ? in the intermediate range. The influence of tortuosity of water phase on R wave velocity is significant in high frequency domain. The tortuosity of air phase is negligible. For a ground system of upper-soft and lower-hard layers

the R wave velocity becomes smaller for thicker surface layer

and approaches the velocity in overlaying soil

especially for high frequency or surface layer with low stiffness.