Impacts of extreme events on hydrodynamic characteristics of a submerged floating tunnel

P.X Zou,Jeremy D Bricker,Wim S.J Uijttewaal

doi:10.1016/j.oceaneng.2020.108221

P.X Zou, Jeremy D Bricker + Show 1 more

Open Access

https://doi.org/10.1016/j.oceaneng.2020.108221

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Abstract

A submerged floating tunnel (SFT) is a promising alternative to conventional bridges and tunnels, and can be potentially built in the Qiongzhou Strait in China. However, this area is under the threat of disasters including mega tsunamis and severe storm surges. To evaluate the hydrodynamic loads of the SFT in this hazardous zone subject to severe tsunami and typhoon impacts, the Delft3D-FLOW hydrodynamic model and SWAN wave model are coupled, and a Computational Fluid Dynamics (CFD) method is adopted. The maximum probable tsunami and typhoon Rammasun (July 2014) are selected as hazard assessment conditions in the Qiongzhou Strait. Whether the tsunami and hindcast storm surge cause extreme forcing and bring challenges to the SFT engineering design, operation, and maintenance in the Qiongzhou Strait are discussed in this study. We reveal that the typhoon impacts are more devastating than tsunami for an SFT in the Qiongzhou Strait. In order to determine the optimal SFT cross-section under extreme events, we use a parametric Bezier curve profile compared with two simpler shapes including circular and elliptical cross sections. In-line force and lift are respectively applied to evaluate the SFT's hydrodynamic behaviour. Our results reveal that the gross horizontal force on the parametric Bezier curve shape is more sensitive to flow acceleration, while the circular cross-section is dominated by current speed. The parametric Bezier curve cross-section shape has the preferable property of reducing the in-line force and postponing serious vortex shedding compared with the two simpler shapes.

Highlights

The Submerged Floating Tunnel (SFT) is a novel sea-crossing infra structure moored afloat from the seafloor, with the advantage of shortened travel distance, increased environmental adaptability, and reduced construction cost compared with traditional alternatives such as immersed tunnels, bored tunnels, and bridges (Fig. 1)
Throughout the simulation, our results show that the Qiongzhou Strait is sheltered by Hainan Island, preventing the devastating inun dation that could occur in Hainan, Guangdong, Taiwan, and Hong Kong (Wu and Huang, 2009; Ren et al, 2017)
Since the optimal submerged floating tunnel (SFT) heading is generally transverse to the strait, the components of current speed and wave direction parallel to the strait heading are most relevant for evaluation of the SFT cross-section hy draulic performance

Summary

Introduction

The Submerged Floating Tunnel (SFT) is a novel sea-crossing infra structure moored afloat from the seafloor, with the advantage of shortened travel distance, increased environmental adaptability, and reduced construction cost compared with traditional alternatives such as immersed tunnels, bored tunnels, and bridges (Fig. 1). A potential SFT construction site, the Qiongzhou Strait (Fig. 2), located between Hainan Island and Leizhou Peninsula (Guangdong) in the South China Sea (SCS), is subject to extreme events (Zhang et al, 2010)– (Jiang et al, 2018). Liu et al (2009) discussed the characteristics of tsunamis generated by earth quakes along the Manila subduction zone and proposed an early warn ing system for the SCS region. Zhao et al (2017) discussed a range of potential tsunami source magnitudes in the Manila Trench and analysed the tsunami impacts near Haikou. Ren et al (2017) investigated the po tential extreme hazard of the Manila Trench, and the impacts on Hainan Island, Taiwan Island, and Lingding Bay. As one of the most devastating natural coastal disasters, tsunamis frequently occur and caused

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