Reflection and Transmission of P Waves at Interfaces of Saturated Sandwiched Coarse Granular Structure

In order to study the reflection and transmission of stress wave at interfaces of the sandwiched coarse granular structure in embedded pile-board subgrade, an interface effect model for the coupled elastic solid-saturated coarse granular layer-elastic solid sandwich structure is established according to the structure characteristic of embedded pile-board subgrade, taking into consideration the superimposed effect of plane P waves reflected from the coarse granular interlayer. Based on the Biot theory and the elastic wave theory, reflection and transmission coefficients at the upper and lower interfaces in the model are derived theoretically by introducing scalar and vector potential functions. Using the derived theoretical formulas, influences of various factors on the reflection and transmission coefficients are discussed through numerical examples. The results show that thickness, porosity and shear modulus of the sandwiched coarse granular structure will change the energy distribution on interfaces, and make it present a periodic resonance characteristic. As the porosity varies from 0.2 to 0.4, the reflection coefficient increases by about 25%. In addition, the propagation of shear wave causes the reflection coefficient to oscillate with damping at the resonant frequencies of the shear wave, and the permeability and flow conditions also have significant effect on the wave reflection. © 2017, Editorial Department of Journal of Southwest Jiaotong University. All right reserved.