DEVELOPMENT CENTRIFUGAL FLUID-WAVE GENERATING SYSTEMS

为研究波浪与海床的相互作用提供了一种新的研究手段，研制了一种用于土工离心机的流体波发生系统。本研究所开发之造波系统包括一伺服马达驱动之襟翼式造波机、一波浪水槽、一垂直槽壁结构之消波器及一沉积槽。利用该系统，已证明可以在波浪水槽中产生一系列接近前进的波浪，并在规定的稳态离心加速度下观察沉积物对波列通过的响应，其中一个重要的考虑因素是根据施加的离心加速度水平选择流体，以便于控制流体的动态粘度。这种特殊的程序是有效的，以满足相似的要求，同时波的传播以及固结过程。本研究的实验方案包括两个系列的波浪试验。第一系列的实验是关于在“非变形”基础上的波浪试验，目的是评估具有一系列结构参数的波浪吸收器的性能，例如开槽面积比和波浪吸收器后面的储层的长度。结果表明，在最佳试验条件下，吸波材料的反射系数可低至15%。第二组试验涉及桑迪沉积物的近行波试验。由于波浪作用，沉积物中的超孔隙压力的积累已被清楚地观察到，这表明该实验系统的能力，调查波浪引起的液化或其他重要的物理过程。

A fluid-wave generating system for use in geotechnical centrifuges has been developed, with the aim of providing a new research tool for investigating into wave-seabed interaction. The wave generating system developed in this research included a servo-motor driven flap-type wave generator, a wave tank, a wave absorber of vertical slotted wall construction, and a sediment trench. With this system it has proven possible to generate a range of nearly progressive waves in a wave tank, and to look at the response of sediments to passage of wave trains, under a prescribed steady-state centrifugal acceleration.One of the important considerations was to select a fluid so as to facilitate the control of dynamic viscosity of the fluid, according to the level of the centrifugal acceleration imposed. This particular procedure was effective to meet simultaneously the requirements of similitude as to wave propagation as well as consolidation processes. The experimental program in this research consisted of two series of wave tests. The first series of experiments was concerned with wave tests over a "non-deforming" base and aim to assess the performance of the wave-absorbers with a range of structural parameters, such as the slotted area ratio and the length of a reservoir behind the wave absorber. It was found that under most favorable test conditions, the reflection coefficient of the wave absorbers was as low as 15%. The second series of experiments was concerned with nearly progressive wave tests with sandy sediments. The accumulation of excess pore pressures in the sediments due to wave action has clearly been observed, indicating the capability of this experimental system for investigating into wave-induced liquefaction or such other important physical processes.