| Summary: | In order to ensure the safety and reliability of the submerged tunnel covering layer at the junction of an artificial island and tunnel under extremely bad conditions, the wave current characteristics and the stability of the protective structure in the variable slope section were studied. By conducting model tests, the coupling effect of wave and current is revealed in this study. The hydrodynamic field, including the varying angles between waves and currents, is simulated in the model test. The ratio (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mi>H</mi><mi mathvariant="normal">s</mi><mo>′</mo></msubsup><mo>/</mo><msub><mi>H</mi><mi mathvariant="normal">s</mi></msub></mrow></semantics></math></inline-formula>) of the wave height and the ratio (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi>U</mi><mo>′</mo></msup><mo>/</mo><mi>U</mi></mrow></semantics></math></inline-formula>) of the velocity with and without the existence of a current, the relative velocity (<i>U</i><inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>/</mo><mi>C</mi></mrow></semantics></math></inline-formula><i>)</i>, the wave steepness (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>H</mi><mi mathvariant="normal">s</mi></msub><mo>/</mo><mi>L</mi></mrow></semantics></math></inline-formula>), the relative water depth (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>d</mi><mo>/</mo><mi>L</mi></mrow></semantics></math></inline-formula>) and the angle (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>α</mi></semantics></math></inline-formula>) between wave and current are obtained, and the corresponding calculation expression is derived, by checking the test results, the empirical formula can better predict the changes of wave height and water flow after wave current coupling. The stable weight of the surface protection rock is obtained through an optimization test. Based on the relationship between the stable weight of the protection rock and the wave height under the wave–current coupling effect, a modified expression for calculating the stable weight of the armor block is derived. The modified calculation method can support estimating the stable weight of the armor rocks of an overburden structure of a similar immersed tunnel under the wave–current coupling effect. This study can not only solve the practical problems of major projects of the Shenzhen–Zhongshan channel but also provide valuable basic data and technical support for the construction of overburden of subsea-immersed tube tunnels in the future.
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