基于内嵌传感器的单层护面块体摇动实测研究

摘要

随机安放的单层护面块体广泛应用于世界各地的斜坡式抛石防波堤。对于这类护面层，块体因摇动而破碎可能是主要的损坏机理，但目前尚无有效方法对摇动加以评价和量化。本文采用新型内嵌式摇动传感器，首次获得了单层块体摇动冲击速度的实测数据。物理模型试验在不规则波作用下针对 Xbloc® 块体护面层开展。一组包含五个波高递增工况的试验序列被多次重复，九个测量单元分别布置于三个不同高程。对于块体高程与波高的每一种组合，均获得了 42 次以上的重复实测（实现），共计 640 次。由摇动传感器可得到冲击次数与转动冲击速度。结果表明，护面层中块体发生摇动的频次远高于目视观测所得。最大冲击速度出现在水线附近以及波浪的上爬阶段。本文给出了单层块体摇动冲击速度的初步设计表达式。此外，可视化技术显示，块体沿坡向下的沉降是一个连续过程，它改变了块体的取向与安放密度，进而影响摇动行为。本文表明，除统计移位块体数量之外，摇动传感器等新型量测技术与可视化技术能够、也应当用于量化抛石防波堤单层护面层的损坏机理。

Abstract

Single layer randomly placed armour units are used in many rubble mound breakwaters around the world. For these armour layers, breakage of armour units due to rocking could be a major damage mechanism, but no good methods exist to evaluate and quantify rocking. This paper utilizes novel embedded Rocking Sensors to obtain the first measurements of rocking impact velocities of single layer units. Physical model tests were performed on an armour layer with Xbloc® units under irregular waves. A test series with five test runs with increasing wave height was repeated several times, with the nine instrumented units being positioned at three different elevations. Over 42 repeated measurements (realizations) of the rocking motion of a unit were obtained for each combination of unit elevation and wave height (640 in total). From the Rocking Sensors the number of impacts and rotational impact velocities were obtained. It appears that the units in the armour layer experience rocking much more often than visually observed. Highest impact velocities are seen to occur around the water line, and in the uprush phase of the waves. A preliminary design expression for rocking impact velocities of single layer units is given. Additionally, a visualization technique shows that the downslope settlement of the units is a continuous process, which changes unit orientation and placement density, and thereby influences the rocking behaviour. The paper shows that novel measurement techniques like the Rocking Sensors and visualization techniques can and should be used to quantify damage mechanisms to rubble mound single layer armour, in addition to counting the number of displaced units.