Kiraga Marta, Popek Zbigniew
Department of Hydrotechnics, Technology and Management, Institute of Civil Engineering, Warsaw University of Life Sciences WULS-SGGW, Warsaw, Poland.
Department of Water Engineering and Applied Geology, Institute of Environmental Engineering, Warsaw University of Life Sciences WULS-SGGW, Warsaw, Poland.
PeerJ. 2020 Oct 30;8:e10282. doi: 10.7717/peerj.10282. eCollection 2020.
In order to regulate water flow, hydraulic structures such as weirs or checks, frequently equipped with gates, are used. Water can flow below or over the gate or, simultaneously, over and below the gate. Both diversifications of hydraulic gradient, being an effect of damming up a river by the structure and shear stresses at the bed, which exceeds the critical shear stress value, invoke the local scouring downstream the structure. This phenomenon has been studied in laboratory and field conditions for many years, however Researchers do not agree on the parameters that affect the size of the local scour and the intensity of its formation. There are no universal methods for estimating its magnitude However, solutions are sought in the form of calculation formulas typical for the method of flow through the structure, taking into account the parameters that characterize a given structure. These formulas are based on factors that affect the size of the local scours, that is, their dimensions and location. Examples of such formulas are those contained in this article: Franke (1960), Straube (1963), Tarajmovič (1966), Rossinski & Kuzmin (1969) equations. The need to study this phenomenon results from the prevalence of hydrotechnical structures equipped with gates (from small gated checks to large weirs) and from potential damage that may be associated with excessive development of local erosion downstream, including washing of foundations and, consequently, loss of stability of the structure.
This study verifies empirical formulas applied to estimate the geometry parameters of a scour hole on a laboratory model of a structure where water is conducted downstream the gate with bottom reinforcements of various roughness. A specially designed remote-controlled measuring device, equipped with laser scanner, was applied to determine the shape of the sandy bottom. Then the formula optimization is conducted, using Monte Carlo sampling method, followed by verification of field conditions.
The suitability of a specially designed device, equipped with laser scanner for measuring the bottom shape in laboratory conditions was demonstrated. Simple formula describing local scour geometry in laboratory conditions was derived basing on the Straube formula. The optimized formula was verified in field conditions giving very good comparative results. Therefore, it can be applied in engineering and designing practices.
为了调节水流，常使用诸如堰或节制闸等水工建筑物，这些建筑物通常配备闸门。水可以从闸门下方或上方流过，或者同时从闸门上方和下方流过。水力学梯度的这两种变化形式，即结构对河流的壅水作用以及河床处超过临界剪应力值的剪应力，都会引发建筑物下游的局部冲刷。多年来，这一现象已在实验室和现场条件下进行了研究，然而研究人员对于影响局部冲刷尺寸及其形成强度的参数尚未达成共识。目前尚无估算其规模的通用方法。不过，人们正在寻求以流经该结构的水流方法的典型计算公式形式的解决方案，同时考虑表征给定结构的参数。这些公式基于影响局部冲刷尺寸的因素，即其尺寸和位置。此类公式的示例包括本文中的Franke（1960年）、Straube（1963年）、Tarajmovič（1966年）、Rossinski & Kuzmin（1969年）方程。研究这一现象的必要性源于配备闸门的水工建筑物的普遍性（从小型有闸节制闸到大型堰）以及下游局部侵蚀过度发展可能带来的潜在损害，包括基础冲刷以及结构稳定性丧失。
本研究验证了用于估算建筑物实验室模型上冲刷坑几何参数的经验公式，该模型中水流经带有不同粗糙度底部加筋的闸门后向下游流动。应用专门设计的配备激光扫描仪的遥控测量装置来确定砂质底部的形状。然后使用蒙特卡洛采样方法进行公式优化，随后在现场条件下进行验证。
证明了专门设计的配备激光扫描仪的装置在实验室条件下测量底部形状的适用性。基于Straube公式推导得出了描述实验室条件下局部冲刷几何形状的简单公式。优化后的公式在现场条件下得到验证，给出了非常好的对比结果。因此，它可应用于工程和设计实践。
