Abstract
Seabed instability surrounding an immersed tunnel is a vital engineering issue regarding the design and maintenance for submarine tunnel projects. In this study, a numerical model based on the local radial basis function collocation method (LRBFCM) is developed to evaluate the seabed behaviour in a marine environment, in which the seabed is treated as the porous medium and governed by Biot’s “ u − p ” approximation. As for the flow field above the seabed, the VARANS equations are used to simulate the fluid motion and properties. The present model is validated with analytical solutions and experimental data which show a good capacity of the integrated model. Both wave and current loading are considered in this study. Parametric studies are carried out to investigate the effects of wave characteristics and soil properties. Based on the numerical results, the maximum liquefaction depth around the immersed tunnel could be deeper under the wave loading with long wave period (T) and large wave height (H). Moreover, a seabed with lower permeability ( K s ) and degree of saturation ( S r ) is more likely to be liquefied.
Highlights
In recent years, to meet the continual improvement requirements in coastal transportation, the immersed tunnel has become one of the choices to fundamentally transform the transport in the region of oceans and rivers, replacing the conventional methods such as the ferry
The immersed tunnel has a history of about 100 years and it shows a good performance in reliability and applicability under complex natural dynamic loading; for example, the longest immersed tunnel in the world, the Hongkong–Zhuhai–Macao Bridge immersed tunnel
The transient liquefaction is motivated by the oscillatory excess pore water pressures under wave pressure vibration which usually happens with amplitude reduction and phase lag of pore pressure in seabed soil [4]
Summary
To meet the continual improvement requirements in coastal transportation, the immersed tunnel has become one of the choices to fundamentally transform the transport in the region of oceans and rivers, replacing the conventional methods such as the ferry. [12,13] simulated the seabed transient and residual response around the immersed tunnel under wave loading based on Biot’s consolidation equations neglecting the inertial terms for soil skeleton and fluid phase. On the basis of the multiquadric RBF [30], Lee et al [31] proposed the local RBF collocation method (LRBFCM) for the first time This method has been applied in various fields, such as the solutions of diffusion problem [32], Darcy flow in porous media [33], water wave scattering [34], macro-segregation phenomena [35] and so on. An integrated numerical model is proposed to simulate the sandy seabed dynamic response and transient liquefaction in the vicinity of an immersed tunnel under natural complex loading. Parametric studies are conducted in regard of the different wave characteristics and soil properties
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