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Numerical Analysis on Influence of Sinking Processes of Immersed Tube Tunnels on Stability of Seabed Foundation Trench Slopes
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摘要: 海洋动力环境下沉管隧道基槽边坡稳定性的评价具有重要研究价值。管节沉放作为沉管隧道施工过程中的关键环节,可能会对基槽边坡稳定性带来不利影响。针对管节下沉阶段中海底基槽边坡动力稳定性进行数值模拟和分析。将波流场计算得到的波流压力施加于基槽边坡及其附近的海床表面,通过达西定律算出波压在海床内部引起的孔隙压力。海床土体采用摩尔-库仑模型,边坡稳定系数采用强度折减法计算。连续获得边坡在不同时刻的安全系数,并将其最小值作为边坡在整个波浪动态作用过程中的稳定性评价指标。对有无波浪荷载、波流环境下有无管节、波流同异向、管节下沉不同位置等各种工况下基槽边坡流场的分布及其对基槽边坡稳定性的影响进行模拟。结果显示:管节下沉对于基槽边坡有着不利影响,且波流环境中管节下沉到某一位置时基槽边坡稳定性最差,波流同向时且沿着边坡向下时最为不利。因此,考虑管节下沉影响有助于提高沉管隧道基槽边坡的设计和施工的科学性和精准性。Abstract: The stability evaluation of foundation trench slopes of immersed tube tunnels in the marine dynamic environment has an important research value. As a key link in the construction process of immersed tube tunnels, the sinking of tube segments of tunnels may have an adverse impact on the stability of foundation trench slopes. The dynamic stability of submarine foundation trench slopes in the sinking stage of tube segments of tunnels was numerically simulated and analyzed. The wave-current pressure calculated by wave-current fields was applied to the slope of the foundation trench and the ambient seabed surface near it, and the pore pressure caused by the wave pressure in the seabed was calculated by Darcy's law. Mohr-Coulomb model was used for seabed soil, and the slope stability coefficient was calculated by the strength reduction method. The safety factors of the slope at different times were continuously obtained, and the minimum value of the dynamic safety factor was taken as the stability evaluation index of the slope in the whole process under wave dynamic action. The flow field distribution of the foundation trench slope and its influence on the stability of foundation trench slope were discussed in the cases of with or without wave loads, with or without tube segments of tunnels in the wave-current environment, in the same or different directions between waves and currents, different sinking depths of tube segments of tunnels and other working conditions. The results indicated that the sinking of tube segments of tunnels had an adverse impact on the foundation trench slope, and the stability of the foundation trench slope was the worst when the tube segments of tunnels sinked to a certain position in the wave-current environment. When the waves and currents were in the same direction and descended along the slope, the slope was most prone to lose stability. Therefore, considering the influence of skining of tube segments of tunnels was helpful to improve the scientificity and accuracy of design and construction for foundation trench slopes of immersed tunnels.
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