WAVE FLUME EXPERIMENT ON SEABED RECONSTRUCTION BY LIQUEFACTION
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摘要: 通过分析模拟波浪连续作用后的液化土床粒度成分、结构及强度变化特征,研究波浪导致底床土液化过程对海床土体性质的改造效应。现场采集黄河口潮滩粉质土,制备波浪水槽的底床进行试验;试验过程中,先后连续施加5、10、15 cm波高的模拟波浪荷载,重复作用两次。选取土床典型区域,分别在模拟波浪作用前后采集原状样品和表层重塑土样,观测土床液化前后土体成分与结构的变化规律,每隔2 h测试贯入强度,并观察土床液化界面变化情况。研究发现,随着液化作用的产生,土床沉积物一定深度范围内出现粒度粗化现象,细粒物质减少,强度增加。土床的成分、结构和强度与液化界面的变化规律及发展速率密切相关。研究成果表明,液化渗流作用对海床成分结构的改造具有重要影响,促使土床中的细粒物质向上输运,液化区域边界粗化,导致成分与结构的变化,而这种分选作用造成了土床强度的大幅提高,揭示出液化是影响粉质土海床成分及强度非均匀化的一个重要因素。Abstract: In this paper, we studied the variation of the granular composition, microstructure and strength of seabed sediments under continuous wave actions and the contribution of wave-induced seabed fluidization to the physical properties of seabed sediments. The silt sediment used in the experiment was taken from the modern Yellow River delta. The experiment includes two rounds under the continuous wave actions of 5cm, 10cm, 15cm in height. Undisturbed samples and surface remould samples taken from selected areas of the soil bed were used for testing of granular composition and microstructure property variations before and after liquefaction, and the penetration strength and the evolution of liquefying failure interface were measured every 2h during the experiment. The results show that the grain size of seabed sediments within a certain depth was getting coarser with the seabed liquefaction due to the sieving away of fine-grained materials and the increase in sediment strength. The features of bed granular composition, microstructure properties and strength are closely related to the variation and the development rate of the liquefied failure interface. It is observed that the liquefaction seepage plays an important role in the reconstruction of bed and the changes in granular composition and microstructure properties, which resulted in the upward transportation of fine-grained materials at certain depths inside the seabed and coarsening of the sediment in the vicinity of liquefied boundary. The grain size sorting of seabed sediments in turn caused a substantial increase in the strength of the soil bed. Therefore, liquefaction is an important factor to the non-lunification of the composition and strength of the silty seabed.
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