简谈抗冲磨混凝土的缺陷处理

水工泄洪建筑物泄洪流量大、流速高,对抗冲磨混凝土的质量要求高,其质量缺陷处理对保证建筑物的安全运行至关重要。本文结合长河坝水电站泄洪建筑物抗冲磨混凝土缺陷的处理方式,总结了施工经验,供其他工程参考。     

三峡工程泄水建筑物抗冲磨防空化设计

1泄水建筑物抗冲磨特征1.1抗悬沙冲磨设计水流挟带钢沙磨蚀泄流建筑物表面，与抗冲磨层厚度，冲磨的时间，检修的时间间隔和抗磨材料的强度有关，在相同的检修时间内，抗冲磨层厚度又与冲磨材料的强度成反比。根据泄水建筑物特征，拟定检修年限内要求抗冲磨强度，按干式计算：R—24KnT／3（l）式中：R抗冲磨强度（h／cm·m勺，即单位面积上磨蚀Icm深所需的小时数。也可以用磨损率表示：单位面积上单位小时磨去的深度（c／b·m’），目前的试验都是把磨去的深度用重量（kg）表示；T一年内冲磨天数，对于径流电站来说冲磨天数为大于河流造…     

泄水建筑物抗冲磨防空蚀设计

以长江葛洲坝水利枢纽为例，分析挟沙水流对混凝土的冲磨特征，总结出泄流建筑物表面抗冲磨的经验关系式，认为对于抗悬沙中磨，表面抗冲磨层厚度与水流流速，水中挟沙量，１年内冲磨天数，检修年限成正比，与混凝土材料抗压强度成反比。根据已建工程经验，提出泄流底表面抗悬沙冲磨层厚度不应小于０．４－０．５ｍ；对于抗石碴，推移质冲磨，其表面抗冲磨层厚度以０．５－０．６ｍ为宜，抗冲磨层材料强度在Ｃ５０左右。     

我国水电站混凝土建筑物耐久性分析

我国大、中型水电站混凝土建筑物受到裂缝，冻融冻胀，渗漏和溶蚀，冲磨和空蚀，水质侵蚀等比较严重的危害，耐久性较差，有的已危及到工程的稳定安全，需投入巨额资金进行修复或加固，目前应全面开展耐久性问题的检查评价和分析研究工作，对遭到严重危害的工程及时加以处理，保证工程的安全，同时应反馈设计，施工，运行全过程的经验和教训，指导工程的建设和管理，提高水电站混凝土建筑物的耐久性。     

水利工程抗冲磨混凝土的实验研究及其应用

高速水流对水工建筑物的冲磨破坏极大,这就对水工混凝土的抗冲磨性能提出了很高的要求。合理选用混凝土的组成材料,能够提高混凝土的抗冲磨强度,避免冲磨破坏,保证工程正常运行就有着极其重要的意义。通过对混凝土拌合料中加入适当的橡胶粉材料进行试验,研究了胶粉材料对混凝土抗冲磨性能的影响,并对其原理进行了分析。     

水工建筑物抗冲磨蚀性能提升对策分析

文章深入探讨了水工建筑物受含沙水流冲磨蚀破坏的特点和机理,并分析了运行管理、施工工艺、材料选择、体型设计与抗冲磨性能间的关系,通过试验研究提出喷涂聚脲弹性体、参数设计等有效提升水工建筑物抗冲磨蚀性能的对策.     

加拿大美国混凝土泄水建筑物抗空蚀：磨冲材料的研究

水利水电工程中泄水建筑物混凝土表面往往在水流急、涡旋度大的条件下,因空蚀和磨冲而严重损坏和破坏,从而缩短了建筑物的寿命,有时甚至会导致发电设施长时间停止运转,造成很大的经济损失。泄水建筑物因空蚀和磨冲而破坏程度与暴     

山区多泥沙河流水电站闸室及护坦修复处理技术研究

我国西南地区河流的河道坡陡流急,泥沙问题十分突出,尤其是推移质来量丰富,粒径级配分布宽,对水电工程冲磨破坏作用更为强烈。由于泥沙含量大,尤其是推移质含量大,水流速度高,泄水建筑物的冲磨和空蚀问题已经成为山区多泥沙河流水电站运行中的主要病害之一。本文以某水闸为例,分析了过流建筑物发生破坏的原因,介绍山区多泥沙河流闸室及护坦修复设计的经验。     

水工泄水结构的抗磨防蚀设计探讨

含沙高速水流对水工泄水结构的冲磨、空蚀破坏已引起人们的高度重视,电力行业标准DL/T5207—2005《水工建筑物抗冲磨防空蚀混凝土技术规范》中的一些规定不尽合理,对水工泄水结构抗冲磨与防空蚀设计的指导性不足。根据当前高速水流对泄水结构冲磨与空蚀的研究成果,提出了进行水工泄水结构抗磨防蚀设计的一些建议。     

聚氨酯(聚脲)弹性体抗冲耐磨材料在水工泄水建筑物上的应用研究

水工泄水建筑物表面涂复一层具有优异抗冲耐磨性能的聚氨酯(聚脲)高分子弹性体材料,抵抗过流时高速水流(有时含推移质)冲磨对建筑物的破坏,起到"以柔克刚"的功效,为减缓水工建筑物高速水流冲磨、气蚀破坏提出了一条新的解决途径.     

乌江渡发电厂尾水右岸冲坑治理措施的探索

在弄清乌江渡水电站尾水河道冲坑及两岸“耳状”崩塌区发展过程的基础上 ,探讨了以往冲坑治理的经验和教训 ,分析了尾水右岸冲坑目前尚存在的问题 ,提出了今后如何治理及对主要混凝土护坡基础进行彻底加固的的建议     

冰盖下桥墩局部最大冲刷深度试验研究

冬季寒冷的北方河流易形成冰盖或冰塞,冰盖的存在对桥墩附近局部冲刷产生影响。在清水冲刷条件下,试验研究了有无冰盖条件下,不同流速和水深对桥墩附近局部冲刷的影响。研究结果表明：对比明流条件,冰盖的存在导致更大的近底流速和近底流速梯度,从而桥墩局部最大冲刷深度更大;其它条件相同的情况下,随流速的增大,桥墩局部最大冲刷深度增大;随着桥墩墩径增大,桥墩局部最大冲刷深度增加;水深增加时桥墩局部最大冲刷深度相对减小。根据试验数据,给出了有冰盖条件下桥墩局部最大冲刷深度的计算公式,与国内外相关试验数据吻合较好。     

枢纽下游河床冲刷深度和水位降落估算方法

通过清水冲刷水槽试验,在探索非恒定输沙及床沙调整等规律的基础上,结合沙量平衡原理,建立了一种枢纽下游河床冲刷深度和水位降落的计算模式。洪峰过程可以概化为一种恒定的"当量流量",深槽冲刷以枯水边界作为脱离体,可将该模式延伸于天然河道。能够计算冲刷过程及终期河床冲刷纵剖面和不同流量下的水位降落。     

Log‐Vane Scour in Clear Water Condition

Log‐Vane is a grade‐control structure of common use to stabilize river bed and river banks. The purpose of this paper is to study the scour phenomena downstream of Log‐Vanes in straight rivers. The main goal is to obtain design equations to determine the main scour parameters and the scour morphology. All the experiments have been carried out in a horizontal channel and in clear water conditions. Log‐Vanes made of wood, with different heights and vane angles, were tested. Different hydraulic conditions including densimetric Froude numbers, water drops and tail water values were tested. Results show that the tail water depth is an important variable to determine the maximum scour depth. The vane angle results to be an important parameter to predict the scour parameters. Dimensional analysis allows to derive design equations useful to estimate the maximum scour depth, maximum length of the scour and maximum height and length of the dune. Copyright © 2014 John Wiley & Sons, Ltd.     

Engineering application of submerged water jets for sediment removal in a tidal riverbed

Sediment deposition problems have attracted the interest of engineers and researchers. Several experimental studies have been conducted on scour depth using turbulent jets. However, field observation and monitoring have rarely been reported. This study aimed to eliminate sediments on a tidal riverbed using a prototype device, which consisted of a set of submerged vertical water nozzles and submerged horizontal air nozzles. The effectiveness of the water jet in sediment removal during spring and neap tides was evaluated. The quantitative relationships of dimensionless parameters, such as (1) the relative sediment scour volume versus the number of flows from the jet exit, (2) the relative sediment scour volume versus the relative scour depth, and (3) the relative scour size versus the relative jet intensity, were analyzed. The results showed that the freshwater flowing to the sea affected the sediment scour volume during the falling cycle of spring tides. In contrast, the rising cycle of spring tides retarded the freshwater flow, resulting in a decrease in the sediment scour volume. A steep water surface slope accelerated the river flow and further influenced the cross-flow current around the study area. As a result, a highly diffusive turbulent flow was produced, causing suspended sediments to be rapidly removed from the scour hole center. An increase in the number of flows from the jets led to intensified diffusion of turbulent energy into the flow. The rapidly varying water depth caused jet energy to be dissipated before approaching the riverbed, and it significantly affected the scour process during the spring-tide period. The proposed equations can be used to estimate the scour volume, scour size, and re-suspended sediments in tidal rivers within defined ranges of parameters.     

三峡工程泄洪坝段下游动床冲刷形态演变过程研究

为验证模型试验坝下动床冲刷坑形态与原型之间的差异,探讨下游冲刷演变过程,用散粒料模拟冲刷岩基,选取3组典型工况复演三峡枢纽蓄水以来泄洪坝段下游冲刷情况。研究表明不同阶段的典型试验工况与相对应条件的原型实测地形整体形态基本相似,说明冲坑形态演变与岩基地质特性有关。     

RANDOM ANALYSIS OF HYDRODYNAMIC CHARACTERIS-TICS OF TRAJECTORY JET CAUSED BY DIFFERENT TYPES OF PIERS

1.　INTRODUCTIONThe energy dissipation problem of overflow damsisalwaysofgreatconcern to hydraulicengineers.Friction and collision,which can be produced by bottom current,surface currentand water jetlashing,are two primary ways of energy dissipation.Designers can deal withthe problem according to their own situation.In this paper,some experiments are reportedon the tail pattern ofpiers.Itis well known thatdeep pithole and far horizontal distance ofthe jet trajectory occur when a flat-tail…     

Sensitivity of river sediment transport and bridge scour to effects of flow,temperature, and sea level

Sediment transport has implications for activities such as fishing, flood control, scour countermeasures, and dredging through altered flow depths and sediment transport, bank erosion, and bridge scour. To estimate the changes in sediment transport and bridge scour, river discharge, water surface slope, water temperature, and tailwater depth (to simulate sea‐level rise) were altered in existing sediment transport and scour models. It was found that (a) in uniform flow upstream of sea‐level rise effects, sediment transport is sensitive to discharge but not to temperature; (b) in non‐uniform flow affected by sea‐level rise, sediment transport is sensitive to water surface slope and discharge but not to temperature; (3) the discharge value to restore the sediment transport rate existing before sea‐level rise is proportional to the water surface slope ratio to the fourth power; (4) the discharge value to restore the bed sediment size existing before sea‐level rise is proportional to the water surface slope ratio to the three‐fourth power; (5) abutment scour is weakly inversely proportional to the water surface slope but more strongly proportional to the discharge in a logarithmic relation; (6) pier scour is weakly proportional to the water surface slope but more strongly proportional to the discharge in a logarithmic relation; and (7) the discharge to restore both abutment and pier scour depths to their original values prior to sea‐level rise is proportional to the water surface slope ratio to the 9/25^th power. Full equations for each of these relationships are given in the article. These relationships can be used for future application and planning purposes.     

Scour around submarine pipes due to high-amplitude transient waves

Estimation of scour dimensions below submarine pipelines is a vital step in designing offshore infrastructure. Extreme events like tsunami waves produce strong erosive forces below the underwater pipes, apt to create scour holes, jeopardizing the safety of the structure. Despite the importance of this issue, previous studies have mainly focused on steady flow cases, and the scour pattern below submarine pipes induced by high-amplitude transient waves has rarely been investigated. This paper reports the results of 40 experimental runs on transient wave-induced scour below a model pipe in a laboratory flume under a variety of initial conditions. The variables included the bed particle size and gradation,initial water depth, wave height, and slope of the bed layer. Waves were generated by a sudden release of water from a sluice gate, installed in the middle of the flume. A pressure transducer data acquisition system was used to record the wave heights at different time steps. The results indicate that, with a shallower initial depth of flow, the scour depth is relatively large. It was also found that there exists a direct correlation between the induced wave height and the size of the scour hole. It was observed that, in clear water conditions, the size of the scour hole in coarse sediments is smaller, while in live-bed conditions, larger scour holes are created in coarser sediments. It was also observed that at high wave amplitudes, the live-bed conditions are dominant, and consequently the bed elevation is altered.     

含沙水流挑流消能对卵石河床冲刷的试验研究

本文通过室内浑水模型试验,探讨了卵石床质河流上泄水建筑物挑流消能对河床的局部冲刷问题。试验结果表明:浑水水流的单宽流量大小、含沙量的多少以及含沙粒径的变化都对冲刷坑深度有一定的影响。本文就浑水冲刷特性问题,与清水挑流消能作了对比,提出了一些初步认识。