Analytical solution for calculating three-dimensional responses due to dynamic loads acting on an underwater tunnel in stratified soil

Abstract

Hydroacoustic noise generated by trains running in underwater tunnels significantly impacts aquatic ecosystems, particularly fish breeding grounds and the habitats of endangered species. This underscores the necessity of investigating the characteristics of wave propagation and noise radiation emanating from underwater tunnels. This study proposes a novel analytical method for calculating 3D responses due to a dynamic point load acting on an underwater tunnel in stratified soils that considers dynamic tunnel–soil–fluid interactions. Stratified soils consist of multiple sediment layers, which are simulated as saturated porous media, overlying substrate layers, which are modeled as phase elastic media. The transfer matrix method is applied to simulate wave propagation in a layered fluid–solid system. The functions describing various types of waves scattered at the layer interfaces and the tunnel–soil interface are unified by wave transformation, thereby deriving an analytical solution for dynamic tunnel–soil–fluid interactions. A comparison with existing methods via numerical cases confirms the accuracy of the proposed method. Vibrations and hydroacoustic noise owing to dynamic loads acting on an underwater tunnel buried either in a saturated sediment layer or a single-phase substrate layer are investigated. The influences of tunnel burial depth, layering, as well as the porosity and permeability of saturated sediment are systematically analyzed. This research enhances the understanding of wave propagation and noise radiation in water emanating from underwater tunnels, facilitating the development of vibration isolation measures and protecting aquatic ecosystems.