Rock engineering design of post-tensioned anchors for dams - A review

High-capacity, post-tensioned anchors have found wide-spread use, originally in initial dam design and construction, and more recently in the strengthening and rehabilitation of concrete dams to meet modern design and safety standards. Despite the advances that have been made in rock mechanics and rock engineering during the last 80 years in which post-tensioned anchors have been used in dam en- gineering, some aspects of the rock engineering design of high-capacity rock anchors for dams have changed relatively little over the last 30 or 40 years. This applies, in particular, to the calculations usually carried out to establish the grouted embedment lengths required for deep, post-tensioned anchors. These calculations usually make simplified assumptions about the distribution and values of rock-grout interface shear strengths, the shape of the volume of rock likely to be involved in uplift failure under the influence of a system of post-tensioned anchors, and the mechanism of that failure. The resulting designs are generally conservative. It is concluded that these aspects of the rock engineering design of large, post- tensioned rock anchors for dams can be significantly improved by making greater use of modern, comprehensive, numerical analyses in conjunction with three-dimensional （3D） models of the rock mass structure, realistic rock and rock mass properties, and the results of prototype anchor tests in the rock mass concerned.

Using Hydraulic Engineering Model Experiment to Study the Sediment Trapping Efficiency of Adjustable Check Dam

The construction of fully closed check dam (CD) is a conventional flood prevention mechanism implemented on rivers. Fully closed CDs trap large amounts of sediments in rivers to stabilize the river slopes and control erosion. However, fully closed CDs cannot selectively trap sediment and may easily overflow, causing them to losing their ability to mediate and hold sediments. Previous studies proposed the concept of “breathable CDs”. The researcher introduced metal slit dam (SD) that could be assembled and disassembled quickly and conveniently. Once a CD reaches maximum capacity, operators must ensure that the water channels of the dam are free from blockage. Moreover, they must inspect the internal accumulation conditions of the dam periodically or immediately following heavy typhoon rains. When necessary, either the sediment buildup in the upriver blockage must be cleared, or the transverse structure of the dam must be removed to allow fine particles to be discharged along with a moderate amount of water. These actions can free up the sediment-storing capacity of the dam for the next heavy typhoon rains. In addition, operators should also inspect the damages inflicted on the dam, such as erosion, wear and tear, and deformation conditions. Damaged components should be disassembled and repaired if possible, or recycled and reused. The present study performed channel tests to simulate closed CDs, SDs, steel pipe dam (SPDs), and steel pipe plus slit dam (SPSDs) for 50-year and 100-year frequency floods. Results were then analyzed to determine the sediment trapping (ST) effects of various CDs, the effects of “adjustable CDs”, and the changes of moderated riverbeds.

Reducing risks in the investigation, design and construction of large concrete dams

An overview of the GeoSafe 2016 Symposium topic is provided using the example of large concrete dams for purposes of illustration.It is essential that the risks associated with large dams be evaluated rigorously and managed proactively at all stages of their lives so that the risk of failure remains As Low As Reasonably Practicable(ALARP).Rock engineering features of large concrete dams that require particular attention,assessment and monitoring during the investigation,design,construction,initial filling,inservice operation,and subsequent repair and upgrade stages of the lives of concrete dams are identified and illustrated by examples from recorded experiences.A number of major concrete dam failures,including that of the St.Francis dam,California,U.S.A.,in 1928,have led to significant developments in rock mechanics and rock engineering knowledge and techniques,as well as in dam design and review processes.More recent advances include a range of analytical,numerical modelling,probabilistic,reliability,failure mode and risk assessment approaches.

Variation in hydraulic conductivity of fractured rocks at a dam foundation during operation

Characterizing the permeability variation in fractured rocks is important in various subsurface applications,but how the permeability evolves in the foundation rocks of high dams during operation remains poorly understood.This permeability change is commonly evidenced by a continuous decrease in the amount of discharge(especially for dams on sediment-laden rivers),and can be attributed to fracture clogging and/or hydromechanical coupling.In this study,the permeability evolution of fractured rocks at a high arch dam foundation during operationwas evaluated by inverse modeling based on the field timeseries data of both pore pressure and discharge.A procedure combining orthogonal design,transient flow modeling,artificial neural network,and genetic algorithm was adopted to efficiently estimate the hydraulic conductivity values in each annual cycle after initial reservoir filling.The inverse results show that the permeability of the dam foundation rocks follows an exponential decay annually during operation(i.e.K/K0=0.97e^(-0.59t)+0.03),with good agreement between field observations and numerical simulations.The significance of the obtained permeability decay function was manifested by an assessment of the long-term seepage control performance and groundwater flow behaviors at the dam site.The proposed formula is also of merit for characterizing the permeability change in riverbed rocks induced by sediment transport and deposition.

Influence of Dams on River Ecosystem and Its Countermeasures

Dam construction is an important engineering measure in dealing with the relationship between water and human being. However, with dam construction, some disadvantages to the river basin may be caused, including flow flux of downstream changed, flooded area reduced, river species and other organisms changed and substance sedimentation. Furthermore, it brings some diseases to human being and human residential areas reduced too. Based on the basic principles of ecohydralic engineering, some countermeasures to minimize the negative effects on rivers were put forward. They are reservoir ecological regulation, ecohydraulic engineering construction and comprehensive water pollution treatment.

基于ArcGIS Engine与AutoCAD的重力坝三维建模系统研究

采用VB6.0作为编程语言对ArcGis Engine与AutoCAD进行二次开发建立了重力坝三维建模系统。该系统采用地形数据生成TIN的建模方法建立地形模型,采用二维图形还原三维模型的图形化建模方法生成坝体模型,利用ArcGis功能将水利枢纽的地理信息加入到建模过程中,并建立数据库Geodatabase储存上述海量信息,进而实现三维分析查询功能。实例表明,该系统具有通用性强、使用快捷、建模效率高等优点。

The siltation of debris flow behind check dam in the midstream of Bailong River

Siltation gradient and siltation length are important parameters for designing gravity check dams for debris flows,which directly affect the accuracy of estimates of interception capacity.At present,siltation gradient calculations are based primarily on empirical values,and range from 0.4 to 0.95 times the channel slope coefficient.The middle reaches of the Bailong River are one of the four areas in China that are most severely affected by debris flow hazards.Gravity dams are widely employed in this mountainous area.However,field studies of their capacity are lacking.In this paper,the operations of check dams were investigated.Based on field investigation results and theoretical analysis,calculations for siltation gradient,siltation length,and dam storage capacity are established.The impact of debris flow density,channel slope,and particle size weight percentages are discussed.The calculations show that the theoretical values for siltation gradient are consistent with measured values with 83.6% accuracy;and theoretical values of siltation length are consistent with measured values with 91.6% accuracy.The results of this research are an important reference for optimal height and spacing of dams,estimation of dam storage capacity,and disaster prevention.

250 m级特高面板堆石坝混凝土面板顺坡向应力控制措施研究

面板应力变形控制是建设250 m级特高混凝土面板堆石坝的关键难题.大量工程实测案例和研究计算表明,特高面板坝压应力常处于较高水平,对于坝轴向应力来说,采用柔性缝降低压应力措施已被工程界普遍接受,然而,目前对于如何降低面板顺坡向压应力尚缺少有效的解决方法.本文以拟建的240 m级GS面板坝为研究对象,从特殊增模区布置、面板施工顺序、面板低高程柔性横缝、高压力区高强度混凝土材料等4个方面提出改善面板顺坡向应力的工程措施.文中通过三维有限元精细模拟方法分析了提出的顺坡向应力改善措施的效果,文中提出的措施可为250 m面板堆石坝面板应力控制提供借鉴.

特高拱坝变形机理可解释性智能预测模型

针对传统“黑箱”模型可以预测却无法解释拱坝变形的缺陷,利用Shapley Additive Explanation(SHAP)理论对特高拱坝的机器学习变形预测模型进行解构分析,分析水压、温度、时效对特高拱坝不同部位径向水平位移的影响规律。构建特高拱坝变形监测数据的轻量梯度提升算法(Light Gradient Boosting Machine,LightGBM)黑箱预测模型,利用SHAP对存在多重共线性的因子进行剔除,再从整个因子集和单个样本两个角度分析不同影响因子对模型变形预测的贡献度;通过分析拉西瓦特高拱坝坝肩、坝基、拱冠等不同部位的径向水平位移与影响因子间的关系,发现时效因子对高程越高、越靠近拱冠位置的径向水平位移影响越大,温度因子主要影响靠近拱冠位置的径向水平位移,水压因子主要影响高程较高位置的径向水平位移,而坝基和深入坝肩岩体测点的径向水平位移几乎不受水位、温度的影响。解决了以往“黑箱”变形预测模型可视性差、内部机理不明的问题,根据可解释模型得到的相关规律可为特高拱坝的工作性态分析和运行管理提供借鉴。

引江补汉工程丹江口下游近坝段枯水期通航水位恢复试验研究

引江补汉工程补水口位于丹江口大坝下游安乐河出口约5 km处,且补水量与调水量基本一致,工程对航道的影响主要体现在减水段,为恢复枯水期通航水位需要开展航道综合治理。利用河工模型试验论证了综合治理方案的效果,并对方案进行了优化及进一步论证。结果表明,减水-补水212 m 3/s方案尾门水位分别为86.47、85.90 m条件下,引航道口—黄家港段水位下降,黄家港以下水位保持不变,其中引航道口水位下降幅度最大,分别下降0.08、0.19 m;综合治理方案1实施后引航道口水位下降均为0.02 m,减水段的水位仍未恢复至调水前的水平,主因是从安乐河口补水的水流并未能进入到左侧主航道内;基于试验研究结果,建议对综合治理方案进行优化,在沧浪洲出水口下沿布置2道护底带;通过试验论证了护底带的4个高程,建议护底带高程为85.5 m,并对护底带高程进一步细化论证;优化后的方案可使引航道口至黄家港段的水位略超过调水前的水平,其中引航道口处最大水位抬高0.06 m。

不同计算方法的云南省永胜县下院滑坡堰塞湖沉积物粒度特征及沉积历史重建

【研究目的】滑坡堰塞湖灾害链危害大,其形成和溃决过程中受外部环境影响大。堰塞湖沉积物作为记录堰塞湖全生命周期的载体,具有良好的古环境和古气候的指示作用,采用最佳解析方法对其进行解读有利于还原沉积物沉积过程及古环境变化。【研究方法】通过野外调查采样和室内测试分析相结合的方法,采用图解法和矩值法计算下堰塞湖沉积物统计特征的适用性问题,使用粒度结合有机质含量重建了堰塞湖沉积环境,对堰塞湖的发育过程进行还原。【研究结果】(1)堰塞湖沉积物分层沉积层序明显,为单一水动力湖相沉积,物质来源稳定,非多物源沉积;综合有机质变化和沉积物粒度特征表明该堰塞湖经历了4次干湿周期,在气候和地质活动的共同作用下至少存在3次堵塞−泄流沉积过程,估算沉积旋回周期约为1750 a,该沉积历史应该是断裂带长期复杂的活动和气候−河流共同作用的结果。(2)通过对图解法和矩值法进行统计分析结果表明,两种方法对平均粒径和分选系数评价一致性较好,可直接进行替换;矩值法对偏态峰态整体计算结果比图解法大,在使用中需进行线性代换。由于描述参照值的缘故,偏态、峰态在统计表述中有所偏差。【结论】堰塞湖沉积物粒径分布简单,采用图解法计算更加便捷,与其他沉积物对比方便,推荐图解法对堰塞湖沉积进行计算。研究结果表明粒度特征对堰塞湖的沉积和溃决过程以及滑坡灾害对气候变化的响应研究具有一定的指导意义,可为还原该堰塞湖沉积期的古环境和古气候提供理论依据。

尾矿坝位移分级预警阈值研究及规律分析

针对尾矿坝在线监测重建设、轻利用的现状,基于尾矿坝位移在线监测时间序列,通过多步逆向云变换算法(Multi-step Backward Cloud Transformation Algorithm Based on Sampling with Replacement,MBCT-SR)改进云模型,根据“3E_(n)原则”和内外包络曲线确定在线监测位移的正常运行值,从而建立尾矿坝位移分级预警阈值模型,并利用某尾矿坝全球导航卫星(Global Navigation Satellite System,GNSS)技术表面位移在线监测数据进行实例验证。结果表明:该尾矿坝水平方向位移的黄、橙、红预警阈值分别为8.41 mm/d、12.94 mm/d、19.41 mm/d,呈现出坝体中间预警阈值最大、并由中间向两侧减小的空间变化规律;尾矿坝垂直方向位移的黄、橙、红预警阈值分别为16.56 mm/d、25.48 mm/d、38.22 mm/d,且随着子坝的堆积,预警阈值逐渐增大。

基于云模型-模糊FMECA法的水库大坝安全性分析

模糊FMECA法通过对水库大坝隐患出现的频率、影响程度进行评价,并通过赋予权重及模糊综合评判对大坝进行风险评估,具有一定的科学性及实用性,但仍存在无法体现大坝隐患因子的随机性及无法准确反应专家主观偏好关系的缺陷。基于此,提出了云模型-模糊FMECA法的水库大坝安全性分析方法,将模糊FMECA法中的评判矩阵、权重矩阵、对应的评语集进行逆向计算,得出了云模型数字特征值,通过模糊评判得到水库大坝风险评判结果的云模型;根据约束条件确定相应评语集的云模型的数字特征值,将大坝风险评判结果的云模型及各评语集云模型通过MATLAB仿真化,以此实现对水库大坝的安全性评价;将该方法运用到云南省某大坝中,得到了该大坝的内部安全评估等级为A,与现场专家组评判结果一致。证明了基于云模型-模糊FMECA法的水库大坝安全性分析具有一定的可行性及科学性。

隧道爆破施工对邻近水坝安全性影响分析

以义东高速防军隧道项目为依托,针对隧道爆破施工对邻近麻车坑水库坝体安全性影响进行研究。从混凝土损伤理论阐述了坝体的破坏过程,采用有限元软件MIDAS GTS NX建立隧道-水坝三维数值模型,通过分析坝体监测点的振速峰值、应力、位移及坝体边坡动安全系数,对其整体稳定性进行评估。结果表明,爆心距为100 m时,所产生的拉应力为0.1 kPa,此时隧道爆破对大坝的损伤几乎忽略不计;隧道爆破振动会导致坝体发生微小沉降变形,最大位移点在坝体中部,爆心距为70 m时,最小Y向位移约0.42 mm;水库大坝现场监测振速峰值为5.65 cm/s,模拟结果中振速峰值最大为2.6 cm/s,坝体边坡动安全系数最小值为1.034,结果均在安全范围内,这表明隧道出口段爆破施工结束后邻近水库坝体仍处于相对稳定状态,研究方法可为今后类似工程提供参考。

数字孪生丹江口工程建设

文章介绍了数字孪生丹江口工程的建设背景及目标需求,重点阐述围绕大坝安全、水质安全、库区安全等核心业务创新研发的多项关键技术,总结梳理了数字孪生丹江口工程后续工作及数字孪生建设面临的挑战,提出数字孪生技术发展展望。

基于序贯高斯模拟法的水利工程坝址区速度建模

水利工程坝址的选取不仅关系着安全性,也影响着后期的投入使用以及稳定运行。通常坝址区选择需要对区域的速度和岩性进行分析,其中高精度的速度建模至关重要。针对水利坝址选取,提出了一种地震信息约束的地质统计学建模方法对坝址区进行高精度速度建模,在此基础上分析坝址选取的安全性及合理性。通过地质统计学理论,分析坝址区速度的区域变异性,利用地震层位的横向信息以及测井资料的纵向信息联合进行序贯高斯模拟,从而建立速度模型,建模结果更加符合实际情况,能有效反映速度的空间分布情况。最后通过建立的速度模型合成地震记录,与实际地震记录相对比,吻合程度较高,表明建立的模型能反映坝址区的速度分布情况,能基于此圈定出有利于修建坝址的区域,验证了方法的可行性。

结合CNN-LSTM优化模型在尾矿坝浸润线预测中的应用

浸润线是尾矿库的生命线,准确地预测浸润线仍是目前较难解决的重要课题。为了能够有效地预测尾矿坝浸润线的演变态势,提出了一种适用于尾矿坝浸润线预测的高精度卷积神经网络-长短期记忆(Convolutional Neural Network-Long Short-Term Memory,CNN-LSTM)网络优化模型。以云南省某铜矿尾矿库为研究对象,运用CNN提取浸润线数据在高维空间的联系,并捕捉浸润线时序特性的空间关联特征,运用LSTM捕捉及解析其长期依赖关系的特点,优化CNN的卷积层层数与LSTM隐含层层数,选取最优组合,实现对浸润线变化趋势的精确预测。试验结果表明:与单一的CNN模型和LSTM模型相比,CNN-LSTM优化模型的收敛速度快,泛化能力强,且该模型的决定系数、平均绝对误差、均方误差、平均绝对百分比误差、均方根误差均达到了非常高的拟合优度及预测精度,显示了基于CNN-LSTM优化模型进行尾矿坝浸润线预测的优越性,为保障尾矿库长期安全运行提供依据。

水利工程中的橡胶坝锚固与安装施工技术研究

橡胶坝作为当前水利工程建设领域拦水调蓄中较为流行的全新低水头建筑物,在水利工程领域有着确切的应用价值。随着工程应用经验的累积,发现此类橡胶坝最典型漏水部位出现在锚固部位,而锚固部位漏水会受到一系列因素的影响。如何控制风险因素,提高锚固件安装质量,对橡胶坝运行产生积极影响。尝试对水利工程中橡胶坝锚固与安装施工技术要点展开分析,对关键施工技术要点以及质量控制的具体内容进行分析,以锚固槽施工、充排水管安装、泵房混凝土施工以及坝袋安装为施工要点,在参建单位的共同协作与努力下,能够顺利完成橡胶坝锚固与安装作业,且通过验收达到合格标准,后期投入使用后,未见质量缺陷,所取得的工程实践应用效果是非常显著与确切的。希望能够引起业内重视,以更好地保障橡胶坝整体施工质量。

新型单组分喷涂聚氨酯对改进蓄水大坝工程止水性的试验研究

以某抽水蓄能电站大坝工程混凝土面板为例,采用新型单组分喷涂聚氨酯防水涂料对改进大坝工程止水性进行试验研究,分析涂料本身性能、涂层抗渗能力、涂层附着力以及耐候性能。结果表明,该新型单组分喷涂聚氨酯防水涂料具有优异的拉伸性能、良好的耐久性能和优异的黏结性能,可有效改进蓄水大坝工程的止水性。

高碾压混凝土拱坝整体稳定安全评估与工程类比研究

为分析高碾压混凝土拱坝的整体安全性,综合模拟主要断层、软弱夹层、裂隙、岩体材料分区以及坝体结构特征,建立拱坝整体稳定三维有限元模型。采用非线性有限元法分析正常运行条件下拱坝-地基的整体工作性态;在此基础上采用水容重超载法,计算拱坝的极限承载能力。结果表明,正常运行条件下,拱坝整体稳定性较好;通过对水容重安全系数进行工程类比,该拱坝具有较高的超载安全系数,处于拱坝工程的中等偏上水平。