Elastic Wave Propagation through a Layered Rock Mass with Adhesive Bedding Planes

Wave propagation in a layered rock mass is a common problem in geotechnical engineering. The bedding planes in a layered rock mass are generally in situ stressed and adhesively bonded. This study extended the time-domain recursive method to analyze the wave propagation in a layered rock mass with adhesive bedding planes. The maximum stress criterion was used to indicate the adhesive failure of bedding planes. The Bandis-Barton and Coulomb slip models were used to characterize the normal and tangential behaviors of bedding planes after the adhesive bond fails. Based on the backward differentiation formula, an analytical solution reflecting four possible states of the bedding plane and the in situ stresses in rock mass was established. Subsequently, the solution was verified for various conditions. Besides, parametric studies were carried out to assess the influences of adhesive properties of bedding planes and in situ stresses on wave transmission. The transmission coefficient of seismic waves increases linearly as the adhesive strength of the bedding plane increases. The in situ normal stress could facilitate wave transmission across the bedding plane, while the in situ shear stress causes the direction-dependency of transmitted waves. Furthermore, the impacts of bedding plane adhesion and in situ stresses on wave propagation were influenced by the amplitude, frequency, and impinging angle of incident waves. The welded model that ignores the adhesion failure of the bedding plane and the unbonded models that neglect the interface adhesion could overestimate or underestimate the transmitted wave across a bedding plane.