Experimental Study on Permeability Characteristics of Geotubes for Seepage Analysis on Safety Assessment of Dams

Geotubes are heterogeneous structures composed of filling sand and bag material,and its pemeability characteristics are different from that of flling sand.The uncertainty of geotubes permeability characteristics results in the failure of seepage analysis of geotube dams,which restricts the safety assessment of the dams.As the basis of the study on the seepage mechanism of the geotubes,the influence of particle grading on pemeability cofficient of flling sand and sand covered with geotextiles were explored by the pemmeability tests of flling sand with different particle grading under the condition of sand covered with or without geotextiles.And the infuence of geotextiles on the permeability coefficient was analyzed by comparing permeability coefficient of sand covered with and without geotextiles.The test results show that the influence of single particle size content on permeability coe ficient is consistent under the condition of sand covered with and without geotextiles.The content of powder,fine,medium and coarse particles is linearly related to their respective permeability cofficients.And the content of powder,fine,medium particles is negatively correlated with their permeability coefficients,while the content of coarse particles is positively correlated with the permeability coefficient.But the pemeability coefficient of sand covered with geotextiles is smaller than that of flling sand under the same conditions.Finally,the parameter d2 50 Cc/Cu was selected as a variable representing the particle grading to fit the empirical formula of permeability coefficient of flling sand and sand covered with geotextiles.

Stability analysis of a concrete gravity dam and its foundation

The stability of dams and their foundations is an important problem to which dam engineers have paid close attention over the years. This paper presented two methods to analyze the stability of a gravity dam and its foundation. The direct analysis method was based on a rigid limit equilibrium method which regarded both dam and the rock foundation as undeformable rigid bodies. In this method, the safety factor of potential sliding surfaces was computed directly. The second method, the indirect analysis method, was based on elasto-plastic theory and employs nonlinear finite element method (FEM) in the analysis of stresses and deformation in the dam and its foundation. The determination of the safety degree of the structure was based on the convergence and abrupt the change criterion. The results obtained showed that structures' constituent material behavior played an active role in the failure of engineered structures in addition to the imposed load.

Research advance in safety analysis methods for high concrete dam

High tensile stresses occurred in high concrete dams and in their foundation lead to the growing importance of their safety with the increase of concrete dam height. Without any exiting specification or successful experiences of concrete dams up to 300 m at home and abroad for reference, experts feel obliged to figure out how to perform safety analysis on high concrete dam. This paper involves the main contents and mechanical features of the safety analysis on high concrete dam and shows the current state and progress of the analysis methods. For the insufficiency and problems existing in normative methods, study on modern numerical method such as finite element method must be strengthened to find out the stress control criterion which is in accordance with the methods. Two aspects of the safety analysis of high dam—— local damage from material level and integral destruction from structure level——should be considered. For the local damage, we should consider the non-homogeneity of material and strengthen the research of meso-damage mechanics. While for integral destruction of the system of high dam and its foundation, a study on non-strength theory should receive enough concerns. Further, attention should be paid to the research on the failure modes and criterions of high concrete dam failure analysis and safety evaluation, and the effect of uncertainty and classification of safety should be considered too.

Safety of Dams： A Pathological Approach of Qualitative and Quantitative Risks

Dams are critical and essential elements in any infrastructure and, in front of accidents occurred in many countries, it is extremely important to know the risk of these structures. Inserted in this context, it was found in the technical literature, methods and tools capable of measuring the exposure value by means of indicators. In the study, the highlights were 12 methods of qualitative, semiquantitative and quantitative risk analysis, representing an overview of risk analysis methods available in the literature with potential use in dams, that it has been done into electronic spreadsheets. The case study is performed on a sample of concrete dam and earth/rockfill built and operated by Eletrobr^s Furnas Company, supported by documentary research, projects, field inspections and interviews with experts. After applying the methods and the analysis thereof, has been prepared the Eletrobras Fumas dam risk analysis method which is characterized by adapting the criteria analyzed to the reality of the company＇s dams and it was also performed the portfolio risk analysis of 18 dams. In spite of the variety and subjectivity of qualitative and semiquantitative methods, the results show that they tend to converge on the analysis of dam based on risk. The application methodology demonstrates the feasibility assessment stage, covering the preliminary analysis for portfolio dams, followed by formal and individual risk analyzes for the most critical structures. These results confirm the applicability of risk analysis techniques, contributing to the consolidation of this toot as fundamental in the dam safety.

Multivariate analysis in dam monitoring data with PCA

Given the limitation of traditional univariate analysis method in processing the multicollinearity of dam monitoring data,this paper reconstructs the multivariate response variables by introducing principal component analysis(PCA) method,explores the ways of determining principal components(PCs),and extracts a few PCs that have major influence on data variance.For steady observation series,a control field for the whole observation values has been established based upon PCA;for unsteady observation series that have significant tendency,a control field for the future observation values has been constructed according to PC statistical predication model.These methods have already been applied to an actual project and the results showed that data interpretation method with PCA can not only realize data reduction,lower data redundancy,and reduce noise and false alarm rate,but also be effective to data analysis,having a broad application prospect.

Effect of Seismic Permanent Deformation on Safety and Stability of Earth-Rock Dam Slope

In order to study the effect of seismic permanent deformation on the safety and stability of earth-rock dam, the permanent deformation is considered as the non-design permanent load, and the stress-strain hysteresis curve is also considered when the earth is under cyclic load. The research work can make the calculation results of plastic collapse more accurate by including the effect of the post-earthquake degree of plastic deformation on the stability of the earth-rock dam, and the dam safety factor decreases from 2.50 to 1.90 after the magnitude-8 earthquake. Moreover, the research work will also improve the design of the earth-rock dam under abnormal operating conditions.

Singular value diagnosis in dam safety monitoring effect values

Based on the principal component analysis, principal components that have major influence on data variance are determined by the energy percentage method according to the correlation between monitoring effects. Then principal components are extracted through reconstructing multi effects. Moreover, combining with the optimal estimation theory, the method of singular value diagnosis in dam safety monitoring effect values is proposed. After dam monitoring information matrix is obtained, single effect state estimation matrix and multi effect fusion estimation matrix are constructed to make diagnosis on singular values to reduce false alarm rate. And the diagnosis index is calculated by PCA. These methods have already been applied to an actual project and the result shows the ability of the monitoring effect reflecting dam evolution behavior is improved as dam safety monitoring effect fusion estimation can take accurate identification on singular values and achieve data reduction, filter out noise and lower false alarm rate effectively.

融合异质层次因果图的尾矿堆积坝安全状态分析

为探究尾矿堆积坝内外部因素对堆积坝体安全状态的影响,提出基于异质层次图的尾矿堆积坝安全状态分析方法。该方法通过构建异质层次因果图,将环境、渗流场和应力场等关键因素与堆积坝安全状态建立联系,并结合异质节点属性特征,形成环-渗-应安全状态分析指标体系;通过提出定量指标动态等级区间计算方法和安全状态等级计算模型,将坝体安全状态定性问题的模糊性转化为定量化表达,实现对尾矿堆积坝安全等级评价;以洛阳某尾矿坝为例验证模型的科学性。结果表明:该模型能合理定量分析因素与状态之间联系,并找出堆积坝负向演化的敏感性因素,给后续筑坝过程的安全管理提供决策依据。

基于CEEMDAN-改进小波阈值的大坝变形数据处理方法

针对现有方法对大坝变形监测数据去噪精度低、易将部分高频有用信息误判为噪声的问题,提出了一种自适应噪声完备集合经验模态分解(CEEMDAN)和改进小波阈值联合去噪的方法。该方法利用CEEMDAN对原始数据进行分解,通过t检验对分解获得的多个本征模态函数(IMF)分量进行特征分析,筛选出含噪分量并利用Pearson相关系数和方差贡献率进行校验,最后采用改进的小波阈值对筛选出的含噪分量进行精细化去噪,并重构去噪后的模态函数分量,得到去噪后的数据。仿真试验和工程实例验证结果表明,该方法在多种不同指标上均优于对比的3种方法,同时能够更有效地保留数据的高频有用信息,提高准确度和平滑性,可用于大坝中的非线性变形数据去噪处理。

不同工况下水库大坝固化灰浆防渗墙防渗效果数值分析

针对山东东营孤东水库坝体渗漏问题,提出了大坝的防渗加固方案,对加固后的大坝渗流及稳定性进行数值计算。结果表明,固化灰浆防渗墙方案能很好地解决大坝渗漏问题,加固后设计蓄水位下出逸比降低于允许渗透比降。在水位骤降的条件下,大坝内部压力水头线下降,安全系数提高到1.40;在地震荷载的工况下,安全系数提高到1.32~1.44。加固后围坝的安全系数满足规范值,保证满足大坝的防渗要求,各工况的安全系数也都符合规范要求,可为类似加固工程提供可靠参考。

混凝土重力坝变形监测数据的相关性分析

混凝土重力坝的变形量可直观反映大坝的综合运行性态,而变形监测数据是坝体变形的直接体现。因此,从时间和空间上掌握坝体变形监测数据之间的规律与相关性,对于大坝后续的异常检测及安全评价等研究具有重要意义。结合大坝变形监测数据实例,分析了环境因素对位移影响存在的滞后性,利用时空相似指数对大坝不同测点间位移构建了综合相似度指标,运用皮尔逊相关系数、斯皮尔曼等级相关系数和最大信息系数法分析了环境因素与测点位移的相关性以及各测点之间变形位移的相关性,为后续建立健康服役诊断模型等更深层次的研究奠定了坚实的基础。

BBN水电站混凝土面板砂砾石坝渗流安全分析

采用GeoStudio岩土软件SEEP/W模块对BBN水电站混凝土面板砂砾石坝进行渗流稳定计算分析,计算正常蓄水位、设计洪水位、校核洪水位3个高水位工况下的渗透比降,与坝基岩土的允许渗流比降进行比较,并通过与渗流安全监测实测资料分析成果进行对比分析,评价坝体及坝基的渗流安全性态,同时复核渗流计算的合理性。研究成果可对类似混凝土面板砂砾石坝设计和安全评价中的渗流稳定计算和复核分析提供一定的参考。

基于BFAST时间序列分解与分段建模的混凝土坝多测点变形定量分析方法

大坝运行环境复杂,其变形与外部荷载之间往往存在明显的非线性关系。为此,提出一种基于BFAST时间序列分解与分段建模的混凝土坝多测点变形定量分析方法,基于重力坝垂线监测数据,首先使用主成分分析提取多个测点的综合位移;其次使用BFAST时间序列分解方法将综合位移分解为季节性和趋势性两部分;然后通过合理选择改变点,建立分段统计回归模型,分时段量化各环境量对大坝位移的影响;最后通过对安康水电站水平位移规律的分时段定量分析验证了所提方法可行、有效。研究结果为更好地分析大坝变形性态演变历程和定量解释大坝变形机理提供了有力的技术支持。

数字孪生小浪底大坝安全监测管理平台建设与应用研究

基于数字孪生小浪底总体框架,开展了小浪底大坝安全监测管理平台建设,打破了多套原有业务系统的技术壁垒,构建了安全监测数据底板、模型平台和业务应用,已在小浪底水利枢纽高水位运行、调水调沙、汛期防洪运用中发挥了关键作用。文章详细介绍了小浪底大坝安全监测管理平台的建设背景、总体架构、建设内容和应用成效,可为同类工程建设提供借鉴与参考。

德兴铜矿四号尾矿库头顶库尾矿堆积坝稳定性分析及评价

针对德兴铜矿4号特大型尾矿库中采用中线法堆坝技术工艺所形成的尾矿堆积坝,通过现场地质调查和室内试验充分调查了尾矿库工程地质特性,定性分析了该尾矿库稳定性。通过上述稳定性计算模型的建立,运用Slide软件自动搜索尾矿库坝内潜在的滑动面并计算分析尾矿库坝可能存在的最危险滑坡的稳定性系数,使用Geostuido中的Seep模块进行计算,计算出各工况下坝体内的压力水头、流场分布情况和地下水流动矢量,对形成坝体高边坡的稳定性进行了分析和预测,并作出了相应分析及评价。

尾矿库溃坝风险分析与安全监测技术研究

本文对尾矿库风险评估进行了全面分析,并有针对性地提出应对对策。结合传统与现代监测技术的应用,通过对尾矿库结构设计、地质条件、运行管理等方面的探讨,希望尾矿库能够在提高安全性能的同时,降低溃坝的潜在危险,为环保提供保障,也为人员的安全提供保障。

某水库大坝保护范围内爆破开挖对大坝结构安全性影响分析

当爆破开挖施工距离大坝较近时,爆破振动必然会对大坝的结构安全性产生一定程度的不良影响。分析爆破振动对大坝结构安全性的影响范围和影响程度,并对爆破开挖方案和施工期大坝安全防护提出合理建议是设计和施工中必须考虑的一个重要问题。结合南一水库大坝保护范围内左岸新建取水口及隧洞工程,建立混凝土重力坝爆破振动响应数值模型,对大坝在爆破振动过程中的应力特征和坝体振速进行分析,评价爆破振动对大坝结构安全性的影响,对类似爆破开挖工程有一定的参考价值。

某水库混凝土重力坝渗流性态分析与评价

某水库建成运行多年,坝体出现不同程度的渗漏,需要进行大坝渗流安全分析评价。笔者通过对水库大坝坝基扬压力、渗流量监测资料进行分析,结合水库大坝运行表现,对大坝渗流安全进行分析评价。结果表明:坝体内部渗流通道复杂,防渗体系存在薄弱环节,坝体渗流量监测手段落后,监测精度和效率较低;水库大坝渗流性态不安全,建议进一步采取处理措施,及时消除隐患,确保大坝运行安全。

基于统计模型因子优选和异常时段温度因子的拱坝变形异常数据分析

拱坝变形是各种环境因素、材料因素等共同作用的结果,正常工作状况下,拱坝整体工作状态处于线弹性工作状态,局部部位呈现非线性。在拱坝运行中往往存在某些明确的事故或异常,导致坝体发生异常变形甚至改变其变形规律。为精确分析异常事件对大坝变形规律的影响,平衡模型精度和模型可解释性的研究需求,进一步优化拱坝变形统计模型,以某保温板失效的拱坝为例,选取典型垂线测点,以拟合的良好性、模型的简单性和检验的有效性为原则,考虑水压滞后效应、实测温度的影响等因素,使用偏最小二乘回归进行统计模型因子优选,并在模型优选的基础上,加入异常时段温度因子,开展保温板异常时段的定量分析,以确定保温板失效对大坝变形的影响。结果表明:相比于使用周期函数,将实测气温及前期平均气温作为输入变量,可提高统计模型拟合、预测精度;加入异常时段温度因子后统计模型的拟合精度明显提高;夏季温升期间保温板失效会减小坝体变形幅度;在冬季温降作用下,坝顶拱冠处PL4-1测点向下游发生3.5 mm的异常变形,右岸1/4拱处PL2-1测点向下游发生1.5 mm的异常变形。

基于专利视角的大坝安全监测技术发展分析

随着大数据、物联网、人工智能的兴起,如何将新兴技术融入大坝安全监测成为水利工程研究的热点问题。现有文献多从理论上对监测方法和系统进行改进,仍未能指导新理论与新方法的实际应用。基于专利文献,从专利申请态势、申请人、技术地域分布、技术构成、技术主题与功效等角度对大坝安全监测技术进行专利分析,发现大坝安全监测的专利申请竞争日趋激烈,理论方法的创新与实际应用存在一定差距。分析与结论可以帮助从业人员了解大坝安全监测技术发展趋势、发现技术创新点以及促进成果转化。