Mechanism of seabed scour and its critical condition estimation by considering seepage forces
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摘要: 从波浪引起的海床内部渗流与床面泥沙运动耦合的角度出发，研究波浪作用下海床临界冲刷机理及计算方法。研究表明，波浪作用下床面泥沙起动及冲刷是一个不断向下发展的过程，最终达到一个临界冲刷深度。波浪引起的渗流力能够显著降低泥沙的临界起动切应力，促进泥沙起动，是影响海床冲刷的一个重要因素。将渗流力引入到传统泥沙起动公式中，推导并给出了波浪作用下海床临界冲刷深度的计算方法。结合室内和现场两个算例，很好地解释了波浪水槽试验中海床"流化"现象和黄河水下三角洲粉砂流冲沟等灾害地貌特征及成因，初步验证了该方法用于评价和计算海床冲刷的有效性。Abstract: The phenomena in the vicinity of seabed surface such as sediment movement are closely related to the wave-induced seepage in the seabed. In this study, the mechanism of seabed scour is investigated, and the estimation of critical conditions for the scouring due to wave-induced seepage force is discussed in detail. Results show that the incipient motion of sediment and the scouring under wave actions are a process that goes progressively downward from seabed surface until reaching a critical scour depth eventually. The critical incipient shear stress of sediment can be reduced and the incipient motion of sediment can certainly be promoted due to the wave-induced seepage force. The wave-induced seepage force is considered as an important driving factor in the estimation of critical conditions for the scouring. The seepage force is supplemented to the traditional formula for estimating the incipient motion of sediment, and a new method for the estimation of critical scour depth due to wave-induced seepage can thus be derived. Two case studies are performed. The "fluidization" phenomenon in the laboratory flume and the genetic mechanism of the submarine geological hazards such as the gully of the silt flow in the Yellow River delta are well explained. The effectiveness of the new method for estimating and assessing seabed scouring has been preliminary tested.
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Keywords:
- wave /
- seabed /
- scour /
- seepage force /
- incipient motion of sediment
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