Isolation Effect of P-Wave By Double-Layer Wave Impeding Barrier in Unsaturated Foundations

Wave impeding block (WIB) barriers are often used to reduce vibration from different sources, but traditional vibration isolation of WIB has been limited to homogeneous materials and single-phase elastic or two-phase saturated foundations by many researchers. In fact, soils in nature are usually tri-phase unsaturated materials, and the propagation characteristics of elastic waves in unsaturated medium are completely different from those in single-phase elastic medium or two-phase saturated porous medium. In addition, the conventional WIB barrier has better vibration isolation only at low frequencies. Therefore, this paper improves the vibration isolation of the WIB by double-layer WIB with the same thickness on the basis of traditional WIB. Based on the wave theory of unsaturated porous media and elastic media, and according to the Helmholtz principle, we can obtain the solution of surface vertical displacement after setting double-layer WIB in unsaturated foundation, and then the isolation effect of double-layer WIB in unsaturated foundation under [Formula: see text]-wave incidence is investigated. The wave impedance ratio at the interface between WIB and unsaturated soil and wave impedance ratio at the interfaces among the layers of WIB is first analyzed on the vibration isolation effect of double-layer WIB, and the wave impedance ratio corresponding to the optimal vibration isolation effect of WIB barrier is achieved. Then the key factors such as incidence angle, incidence frequency, saturation, thickness, and burial depth of the double-layer WIB are evaluated on its vibration isolation properties. Finally, the isolation effects of single-layer homogeneous WIB and double-layer non-homogeneous WIB with the same thickness are compared. For the same thickness isolation barrier, the vibration isolation efficiency of double-layer WIB is 42.73% higher than single-layer at the incidence angle of [Formula: see text]–[Formula: see text]. The double-layer WIB has better isolation effect at low, medium and high frequencies than single-layer WIB.