Study of boulder transport by tsunamis is challenging because boulder size, shape, and composition vary greatly; furthermore, flow conditions, topography, and initial conditions are generally unknown. To investigate the mechanism of boulder pickup, experiments of tsunami-like flow past spherical boulders partially buried in a sediment bed are conducted. The experiments are performed in a large centrifuge facility to reduce scale effects and the corresponding dynamic similitude is discussed. The traditional approach to determine boulder pickup is adapted for the case of a half-buried spherical boulder. The adapted model predicts that the boulders are transported, but does not accurately predict the timing of pick up. To investigate the difference in pickup timing, two physical phenomena are discussed: pore-water-pressure dissipation in the soil, and the impact of the free-surface flow on hydrodynamic forces. For a spherical shaped boulder, vertical forces (i.e. buoyant and lift forces) are critical for the initiation of boulder pickup. It was found that spherical boulders that are three-quarter buried in the soil are not transported, even when exposed to flow conditions that would otherwise predict transport.

中文翻译：

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Tsunami Surge 的 Boulder Pickup

由于巨石的大小、形状和成分差异很大，因此研究海啸带来的巨石运输具有挑战性。此外，流动条件、地形和初始条件通常是未知的。为了研究巨石拾取的机制，进行了海啸般的流经部分埋在沉积物床中的球形巨石的实验。实验在大型离心机设施中进行，以减少规模效应，并讨论了相应的动态相似性。确定巨石拾取的传统方法适用于半埋球形巨石的情况。调整后的模型预测巨石会被运输，但不能准确预测拾取的时间。为了研究拾取时间的差异，讨论了两种物理现象：土壤中的孔隙水压力消散，以及自由表面流动对水动力的影响。对于球形巨石，垂直力（即浮力和升力）对于启动巨石拾取至关重要。结果发现，四分之三埋在土壤中的球形巨石不会被运输，即使暴露在本来可以预测运输的流动条件下也是如此。