AN EXPERIMENTAL STUDY ON THE TSUNAMI BOULDER MOVEMENT
AN EXPERIMENTAL STUDY ON THE TSUNAMI BOULDER MOVEMENT
复制标题
海啸巨石运动的实验研究
DOI：
10.9753/icce.v34.currents.16
复制
发表时间：
2014
期刊：
影响因子：
--
通讯作者：
Shinji Sato
中科院分区：
文献类型：
--
作者：
Hai;Taiki Sakashita;Shinji Sato
2011年东北海啸事件发生后，通过随后的现场调查，观察到了一些流离失所的海啸巨石。为了模拟海啸引起的巨石陆上运动过程，在滩面上方水平河床上设置了混凝土砌块，在明渠中进行了一系列溃坝式水力试验。采用三种不同的初始水头设置和三种不同的海啸-巨石相互作用角。测量了瞬时水位和涌流速度，并用摄像机记录了巨石移动的整个过程。实验中观察到了巨石的滑动运动。与正常入射海啸相比，斜入射海啸波由于海流投射面积较大，导致巨石位移较长。据证实，块体移动不是由水柱到达立即引发的，但在海啸到达和巨石运动开始之间存在一段可测量的时间间隔。初始水头设置的微小差异可能会导致巨石总位移的显著差异。对于巨石的移动过程，从实验中可以识别出三个阶段，即加速阶段(开始阶段)、减速阶段(中期阶段)和相对稳定的移动阶段(结束阶段)。通过实验证实，巨石总位移的差异主要归因于减速阶段和稳定移动阶段的巨石移动速度的差异。
A number of displaced tsunami boulders were observed through the subsequent in-site surveys after the 2011 Tohoku tsunami event. In this study, a series of dam-break type hydraulic experiments were carried out in an open channel with a concrete block setting on a horizontal bed just above the beach face to simulate the tsunami-induced boulder overland movement process. Three different initial water head settings were applied with three different tsunami- boulder interaction angles. Instantaneous water level and bore current velocity were measured, and the entire boulder moving process was recorded using a video camera. Sliding boulder movement was observed in the experiments. Comparing to the normal incident tsunami, oblique incoming tsunami wave resulted in a longer boulder displacement owing to the larger current-projected area. It was confirmed that the block dislodgement is not triggered immediately by the arriving of the water bore, but there exists a measurable time lag between the tsunami arrival and the inception of boulder movement. A small difference in the initial water head settings could lead to a significant difference on the total boulder displacement. As for the boulder moving process, three phases were identified from the experiment, i.e., the acceleration phase (at the beginning stage), the deceleration phase (in the middle stage), and the relatively steady moving phase (in the end). From the experiment, it was confirmed that the difference in the total boulder displacement is mainly ascribed to the boulder moving velocity difference during the deceleration and steady moving phases.