Reservoir Sedimentation Rates in the Little Washita River Experimental Watershed,Oklahoma: Measurement and Controlling Factors

Forty‐five flood control reservoirs, authorized in the Watershed Protection and Flood Prevention Act 1954, were installed by United States Department of Agriculture (USDA) between 1969 and 1982 in the Little Washita River Experimental Watershed (LWREW), located in central Oklahoma. Over time, these reservoirs have lost sediment and flood storage capacity due to sedimentation, with rates dependent on upstream land use and climate variability. In this study, sedimentation rates for 12 reservoirs representing three major land use categories within LWREW were measured based on bathymetric surveys that used acoustic profiling system. Physiographic and climate attributes of drainage area of surveyed reservoirs were extracted from publicly available data sources including topographic maps, digital elevation models, USDA Natural Resource Conservation Service soils, and weather station databases. Correlation, principal component analysis, and stepwise regression were utilized to analyze the relationship between normalized reservoir sedimentation rates (ReSRa) and the drainage area characteristics to determine the major variables controlling sedimentation within the LWREW. Percent of drainage area with extreme slopes, saturated hydraulic conductivity, and maximum daily rainfall event recorded in spring explained most of the variability in ReSRa. It was also found that percent reduction in reservoir surface area can be used as a surrogate for estimating ReSRa. The implications of the results are discussed.     

Potential Impacts of Climate Change on the Reliability of Water and Hydropower Supply from a Multipurpose Dam in South Korea

Future climate change is a source of growing concerns for the supply of energy and resources, and it may have significant impacts on industry and the economy. Major effects are likely to arise from changes to the freshwater resources system, due to the connection of energy generation to these water systems. Using future climate data downscaled by a stochastic weather generator, this study investigates the potential impacts of climate change on long‐term reservoir operations at the Chungju multipurpose dam in South Korea, specifically considering the reliability of the supply of water and hydropower. A reservoir model, Hydrologic Engineering Center‐Reservoir System Simulation (HEC‐ResSim), was used to simulate the ability of the dam to supply water and hydropower under different conditions. The hydrologic model Soil and Water Assessment Tool was used to determine the HEC‐ResSim boundary conditions, including daily dam inflow from the 6,642 km² watershed into the 2.75 Gm³ capacity reservoir. Projections of the future climate indicate that temperature and precipitation during 2070‐2099 (2080s) show an increase of +4.1°C and 19.4%, respectively, based on the baseline (1990‐2009). The results from the models suggest that, in the 2080s, the average annual water supply and hydropower production would change by +19.8 to +56.5% and by +33.9 to 92.3%, respectively. Model simulations suggest that under the new climatic conditions, the reliability of water and hydropower supply would be generally improved, as a consequence of increased dam inflow.     

筋带密度对尾矿坝漫顶破坏规律影响研究

基于相似理论和溃决侵蚀原理,进行不同加筋密度条件下尾矿坝洪水漫顶破坏模 型试验,探析了筋带密度对尾矿坝漫顶破坏影响规律。试验结果发现:①随着筋带密度 的增加显著提升了尾矿坝的力学强度,但也导致了坝体内的浸润线升高;②筋带密度的 增加使溃口由“Y”型逐渐向“H”型转变;③筋带密度的增加阻滞了漫坝破坏的发展, 坝体位移及内部应力变化量明显减小;④增加筋带密度提高了坝体的抗冲刷能力,减弱 了洪水对蚀沟两岸尾砂的拉拽作用,保证了蚀沟两翼坝体的稳定;⑤随着筋带密度增加 ,可有效减小坝体位移和溃口深度、宽度的发展,当筋带超过2层后,筋带层数的增加 对坝体溃口宽、深基本无影响。研究成果深入探析了筋带密度对漫顶破坏影响规律,在 尾矿坝加筋研究方面提供了科学依据。     

尾矿坝地震液化评价可靠度模型及应用

为适应计算参数本身具有的随机性和未确知性,将可靠度理论引入尾矿坝地震液化评价中。以测试数据的统计分析结果为基础,应用一次二阶矩法建立尾矿坝地震液化分析可靠度模型,探讨了可靠度指标与抗液化安全系数之间的关系,并将该模型应用到某尾矿坝地震液化分析中。结果表明,新建可靠度模型各参数的物理意义与统计指标明确,相比传统的确定性分析方法,不仅能判断液化的发生与否,还能给出液化发生的概率;可靠度理论在液化分析中能更好地考虑计算参数的变异性,进一步完善了尾矿坝地震液化分析理论,为进行基于风险分析的尾矿坝抗震设计和地震安全评价提供更全面的依据。     

尾矿库溃坝风险定量评价方法探讨

针对目前尾矿库安全评价中无定量评价尾矿库溃坝风险的现状,坝体稳定性计算中未考虑到坝体实际为非均质体的特点,本文提出将容重、内摩擦角和凝聚力三者视为随机变量,采用蒙特卡洛模型计算尾矿坝溃坝失效概率;综合运用水文学、水动力学、非牛顿流体的运动理论,建立尾矿库溃坝后尾矿下泄模型,以计算溃坝淹没范围;综合考虑尾矿库溃坝后生命损失、财政损失和环境损失,计算尾矿库溃坝风险损失度;最终确定尾矿库溃坝风险度,以期提高尾矿库安全评价技术、确保尾矿库安全健康运行.     

基于灰色系统理论的尾矿库坝体形变位移预测方法

为了降低尾矿库在金属非金属矿山安全生产中的危险,提高尾矿库在线监测数据的准确性,提高尾矿库工程溃决的预报预测水平,将尾矿库坝体形变位移作为研究重点,以在线监测技术测得的数值为原始数据,利用灰色系统理论的方法,以时间为主线,建立尾矿库坝体位移数学模型.最后,进行了工程实际坝体形变位移预测,结果表明,利用灰色系统理论建立的模型进行预测可以排除天气、人工、现场条件等许多因素的影响,为人工监测提供可靠依据.     

大坝安全评价的可接受风险研究与评述

评述了国内外安全领域可接受风险研究的历史和现状.根据事故后果对风险进行分类,对不同类型风险给出风险定量表示方法,针对不同的风险定量表示方法,应用F-N曲线和ALARP准则研究相应的可接受风险确定方法,并就其在大坝安全风险评价领域的应用进行探讨.     

深厚黄土覆盖层上土石坝地震响应特性分析

采用非线性有限单元法和笔者曾提出的动孔压试验曲线法,对某深厚黄土覆盖层上土石坝进行了有效应力法地震响应分析,重点分析大坝的绝对加速度、动位移和动应力等动力响应及动孔隙水压力分布情况。分析结果表明,在现有设计条件下,由于坝基软弱黄土覆盖层较厚,大坝在7度地震作用下地震响应不强烈,但坝基黄土覆盖层会出现液化情况,需采取相应的抗液化工程措施。     

考虑拦污栅-坝体相互作用的混凝土重力坝抗震安全性分析

对考虑拦污栅-坝体的动力相互作用的弹性连接和刚性连接的拦污栅-坝体以及不作耦联分析的拦污栅-坝体这三种不同模型结构形式的动力特性和动力响应进行了比较分析。研究发现,拦污栅的不同模型结构形式对大坝的抗震安全性分析有重要影响,考虑拦污栅-坝体的动力相互作用后,坝体损伤开裂的程度明显加大,坝顶的水平位移响应也明显提高。按《规范》规定的对拦污栅和坝体不作耦联分析的抗震计算方法,所得结果对坝体是偏于不安全的,而如考虑拦污栅-坝体之间的弹性连接,所得结果则是偏于安全的。     

溢流堰形态对水体营养盐及有机污染的影响

定期监测两种不同形态的溢流堰坝体上下点的溶解氧及水质变化,研究溢流堰形态对水体营养盐及有机污染的影响。结果表明:两种不同形态的溢流堰均可较好地提高水体的DO含量,且阶梯式溢流堰较斜面式溢流作用明显;高锰酸盐指数IMn、NH3-N、TP含量均减少,平均去除率阶梯式溢流堰均优于斜面式溢流堰。