Abstract: Based on the propagation theory of elastic waves in unsaturated porous medium and single-phase elastic medium, considering that a composite multilayer wave impeding block(WIB) with a certain thickness is set in unsaturated soil (composite multilayer wave impeding block with three layers as an example), analytical solutions of transmitted/reflected amplitude ratio of S-wave passing through a composite multilayer wave impeding block in unsaturated soil foundation are derived by using Helmholtz vector decomposition theorem. The influences of physical and mechanical parameters such as shear modulus and density of interlayer wave impeding block on the propagation characteristics of S-wave passing through composite multilayer wave impeding block in unsaturated soil are analyzed by numerical examples. The results show that the shear modulus and the density of interlayer wave impeding block material have significant influences on the transmission/reflection coefficient. Therefore, the composite multilayer wave impeding block is an effective vibration isolation barrier, and a better vibration isolation performance can be obtained by strictly controlling the shear modulus and density of interlayer wave impeding block, which provides theoretical guidance for the application of composite multilayer wave impeding block in the field of foundation vibration control.

Key words: unsaturated soil, composite multilayer wave impeding block, isolation effect, reflection amplitude ratio, transmission amplitude ratio