A simplified physically-based breach model for a high concrete-faced rockfill dam:A case study

A simplified physically-based model was developed to simulate the breaching process of the Gouhou concrete-faced rockfill dam （CFRD）, which is the only breach case of a high CFRD in the world. Considering the dam height, a hydraulic method was chosen to simulate the initial scour position on the downstream slope, with the steepening of the downstream slope taken into account; a headcut erosion formula was adopted to simulate the backward erosion as well. The moment equilibrium method was utilized to calculate the ultimate length of a concrete slab under its self-weight and water loads. The calculated results of the Gouhou CFRD breach case show that the proposed model provides reasonable peak breach flow, final breach width, and failure time, with relative errors less than 15% as compared with the measured data. Sensitivity studies show that the outputs of the proposed model are more or less sensitive to different parameters. Three typical parametric models were compared with the proposed model, and the comparison demonstrates that the proposed physically-based breach model performs better and provides more detailed results than the parametric models.

Preliminary Studies on Base Substitutions and Repair of DNA Mismatch Damage Stimulated by Low Energy N^+ Ion Beam Implantation in Escherichia coli

Ever since the low energy N+ ion beam has been accepted that the mutation effects of ionizing radiation are attributed mainly to direct or indirect damage to DNA. Evidences based on naked DNA irradiation in support of a mutation spectrum appears to be consistent, but direct proof of such results in vivo are limited. Using mutS, dam and/or dcm defective Eschericha coli imitator strains, an preliminary experimental system on induction of in vivo mutation spectra of low energy N+ ion beam has been established in this study. It was observed that the mutation rates of rifampicin resistance induced by N+ implantation were quite high, ranging from 9.2 x 10~8 to 4.9× 10~5 at the dosage of 5.2×1014 ions/cm2. Strains all had more than 90-fold higher mutation rate than its spontaneous mutation rate determined by this method. It reveals that base substitutions involve in induction of mutation of low energy nitrogen ion beam implantation. The mutation rates of mutator strains were nearly 500-fold (GM2929), 400-fold (GM5864) and 6-fold larger than that of AB1157. The GM2929 and GM5864 both lose the ability of repair DNA mismatch damage by virtue of both dam and dcm pathways defective (GM2929) or failing to assemble the repair complex (GM5864) respectively. It may explain the both strains had a similar higher mutation rate than GM124 did. It indicated that DNA cytosine methylase might play an important role in mismatch repair of DNA damage induced by N+ implantation. The further related research were also discussed.

Probabilistic analysis for the response of nonlinear base isolation system under the ground excitation induced by high dam flood discharge

According to theoretical analysis, a general characteristic of the ground vibration induced by high dam flood discharge is that the dominant frequency ranges over several narrow frequency bands, which is verified by observations from the Xiangjiaba Hydropower Station. Nonlinear base isolation is used to reduce the structure vibration under ground excitation and the advantage of the isolation application is that the low-frequency resonance problem does not need to be considered due to its excitation characteristics, which significantly facilitate the isolation design. In order to obtain the response probabilistic distribution of a nonlinear system, the state space split technique is modified. As only a few degrees of freedom are subjected to the random noise, the probabilistic distribution of the response without involving stochastic excitation is represented by the δ function. Then, the sampling property of the δ function is employed to reduce the dimension of the Fokker-Planck-Kolmogorov （FPK） equation and the low-dimensional FPK equation is solvable with existing methods. Numerical results indicate that the proposed approach is effective and accurate. Moreover, the response probabilistic distributions are more reasonable and scientific than the peak responses calculated by conventional time and frequency domain methods.

数字孪生技术助力南四湖防洪调度与二级坝工程管理

数字孪生建设是“十四五”期间推进智慧水利建设的重要内容之一,为提高南四湖流域防洪调度水平和二级坝工程运行管理能力,采用南四湖防洪调度、二级坝泄量纠偏及调度仿真等关键技术,建立和完善二级坝感知体系,提升算力能力建设;建设数据底板,加强算据能力建设;研发多种模型,智能展示数据成果;开发具有“四预”功能的防洪调度和水闸综合管理业务应用等系统。系统的建成可全面提高南四湖防洪调度及二级坝工程管理安全运行管理水平,为后续数字孪生沂沭泗建设提供经验样本和技术模板。

Crucial technologies in the design of Xiluodu Super High Arch Dam

Some super high arch dams （ SHADs）, like Xiluodu Arch Dam, after their heights reaching the magnitude of 300 m, confront lots of technical challenges in design and construction. Several crucial technologies of 6 SHADs will be reviewed and discussed in this and consecutive papers, including Xiluodu, Jinping I in China, Baktiary in Iran, ete. , on the topics of the research method, criterion for evaluation and engineering application of dam safety analysis and evaluation, reasonable dam base interface, dam shape optimization, comprehensive treatments of complex foundation, anti-seismic engineering, dam construction material, concrete placement and temperature control, instrumentation and monitoring of dam operation, etc. This paper will mainly focus on the overall safety of SHADs, reasonable dam base interface analysis and evaluation and their engineering application.

不同基座高度对沥青混凝土心墙堆石坝受力特性的影响研究

为研究不同基座高度对沥青混凝土心墙坝受力特性的影响,采用邓肯-张E-B模型作为坝体及心墙的本构模型,对大坝施工和蓄水过程进行模拟,并依据基座与心墙的高度关系拟定5种计算方案,对比不同基座高度下堆石体和心墙的受力特性。结果表明,基座越高,大坝堆石体竖向位移及第一、三主应力越小,而心墙第一、三主应力越大,竖向位移则随基座增高而减小。在此基础上,利用熵值法构建了基座影响定权模型,量化了基座高度变化对大坝不同部位的影响程度:基座高度变化对心墙的影响(权重56.06%)最显著,建议工程设计和安全评价需要考虑基座高度发生变化时对心墙第一主应力状态的影响。研究成果可为沥青混凝土心墙堆石坝工程设计和施工提供参考依据。

Analysis and evaluation on seepage stability of Hongxing reservoir dam,Heilongjiang

Hongxing reservoir was constructed on the floodplain of Hulan River in Heilongjiang. The geological problem of the reservoir is the seepage of the dam base and its related seepage stability. The leakage of the reservoir is caused by the water head differences between the upstream and downstream of the dam. Severe seepage could decrease the engineering benefits of the reservoir. Moreover,infiltration function of water will influence the safety of the dam. Through the analysis on the granule constitute and the formation of the dam base,the types of the seepage failure apt to happen were defined and the anti-infiltration and the permissible depression ratio were determined. Using the numerical simulation software GMS,the two-dimension numerical modeling has been carried out to analyze the seepage field of the reservoir. Through the two conditions modeling with concrete impervious wall and no concrete impervious wall,the largest flow rate,single-wide seepage discharge and the max infiltration gradient of the dam base were calculated. According to the permeable depression ratio of the dam base,the seepage stability of Hongxing reservoir dam base was analyzed.

基岩地基上心墙堆石坝基座体型对基座结构的影响

为研究合适的基座体型方案,以重庆巫山庙堂水库为例,采用数值模拟的方法分析了基座上游侧角、下游侧角和宽度对心墙与基座连接结构的影响,并提出了基座体型优化方案。结果表明,对于基座应力,影响程度由大到小依次为下游侧角>基座宽度>上游侧角;对于心墙竖向位移,影响程度由大到小依次为上游侧角>下游侧角>基座宽度;优化方案有利于连接结构的应力安全和变形控制,各项指标均有不同程度下降,尤其是拉应力最大值较初始方案降低了71.1%,此优化方案可供同类工程参考。

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。

水利枢纽坝基防渗措施分析

基于北京市某中型水库渗漏现状,分析渗漏特点,对比分析3种防渗加固方案,从技术方法和方案设计两方面对高喷灌浆施工方案进行介绍,同时从工艺流程及钻孔、浆液配制、喷浆、孔口回灌等对高喷灌浆施工要点进行详细探讨。

某水电站大坝坝体开孔生态基流下泄方案

生态基流是对在运水电站的一个全新要求。某水电站大坝下游产生了明显的减水河段,生态流量下泄迫在眉睫。笔者介绍了该大坝生态基流下泄的设计、实施方案,并经运行考验,综合评判方案合理性,可供其他在运水电站参考。

关于将斜拉坝技术运用于淤地坝建设的设想

均质土填筑的淤地坝易发生连锁溃坝,文中提出了将斜拉坝技术运用于淤地坝建设的设想,并与闸坝和液压升降坝2种方式进行了对比。在大厚度黄土地区修建斜拉坝,其主要技术难点是坝前拉索的锚固问题,对此开发设计了适用于深覆盖层上建设斜拉坝的抗拔基础结构。并对斜拉坝的防渗、泄洪等方式进行了探讨。

DNA-based方法及其在研究动物食物组成中的应用

了解动物的食物组成是研究生态系统的多样性和生态系统功能的基本要求,在动物生态学的研究中至关重要。DNA-based方法包括样本采集、DNA提取、PCR扩增、序列比对分析等一系列步骤,实验的成败取决于标记基因的选择、引物的设计及每个步骤的优化。文章综述了DNA-based方法的各个基本步骤及其优化方法,并对该方法在今后用于国内相关研究的可能性进行展望,关注用于研究国内三峡大坝这个大型水域生态系统的可能性,期望推动国内该领域的研究。

带有两端防渗墙坝基的各向异性渗流解析解

由于目前在坝基设计中通常需要设置两个或两个以上防渗墙,对带有两端防渗墙的坝基各向异性稳态渗流进行了解析研究,将土体分为4个规则的区域,采用坐标变换将各向异性土层转换成等效各向同性土层,利用分离变量法将4个区域内的水头分布表示为级数解的形式,结合区域间的连续条件得出带有两端防渗墙的坝基各向异性渗流场显式解析解。将解析解退化到各向同性情况下的渗流量、坝底扬压力与保角变换解析解和数值计算结果进行对比,各向异性情况下的水头值与有限元软件计算结果进行对比,结果均吻合较好,验证了解析解的正确性,且相比于保角变换解析解具有更高精度。最后对坝基渗流场进行了参数分析,发现土体各向异性对坝基渗流有着不可忽略的影响,其他条件相同的情况下,竖直渗透系数与水平渗透系数比值较大土体的渗流量和出口梯度会小于竖直渗透系数与水平渗透系数比值较小的土体,竖直渗透系数与水平渗透系数比值较大的土体的最大扬压力会大于竖直渗透系数与水平渗透系数比值较小的土体。

特高土心墙堆石坝坝基防渗体渗流-溶蚀特征研究

针对渗透溶蚀效应下特高土心墙堆石坝的渗流与溶蚀问题,构建了以孔隙水压力、固相钙浓度与钙离子浓度为自由度的水泥基材料渗流-溶蚀耦合模型。以长河坝工程为背景,研究了特高土心墙堆石坝的渗流溶蚀特征,探讨了渗透溶蚀效应下特高土心墙堆石坝的失效标准,预测了坝体的服役年限。渗透溶蚀效应降低了坝体的防渗能力,服役100 a后坝体浸润线逸出点将较初始时刻抬升1.95 m;随着服役年限的增加,覆盖层、副防渗墙的渗透坡降增加,心墙、主防渗墙和防渗帷幕的渗透坡降降低;水泥基材料固相钙溶蚀相对严重的区域集中在两道防渗墙中下部、固结灌浆靠下游侧及防渗帷幕,靠近复合土工膜和高塑性黏土的坝基防渗体溶蚀程度较低。从固相钙的分解率、渗透系数、渗流量、渗透坡降和边坡稳定等角度分析,认为考虑渗透溶蚀效应时长河坝的服役年限约为68.3 a,降低主防渗帷幕的初始渗透性可较为有效地延长坝体服役年限。特高土心墙堆石坝坝基水泥基结构渗透溶蚀效应不可忽视,其设计、运行及维护应充分考虑水泥基材料的渗透溶蚀效应。

代古寺面板堆石坝渗流场有限体积法数值分析

针对代古寺混凝土面板堆石坝的坝体、坝基、面板与防渗帷幕等结构进行了三维精细化建模,模型单元数量达千万级别。运用自主研发的有限体积三维渗流计算分析软件DUT-Seepage对面板堆石坝进行三维渗流计算,着重研究面板与帷幕作用下的渗流场分布特征及其防渗效果,探讨基岩渗透系数对面板堆石坝渗流量的影响,最后分析了当坝基中存在挤压破碎带时,其渗透系数对大坝浸润线位置及渗流场的影响。研究结果表明:该混凝土面板堆石坝的面板和防渗帷幕有效阻断了上游水流的渗透,起到较好的防渗效果,能够保证大坝的安全运行;挤压破碎带的渗透系数对大坝浸润线的位置影响较小,但对孔隙水压力与总水头的分布影响较大,且当破碎带渗透系数较大时,水力梯度也会增大,对破碎带周边产生潜在渗透破坏风险。

Potential application of particle based simulations in reservoir security management

In order to model the movement progress in case of risks such as dam collapse and coastal inundation, particle-based simulation methods, including the discrete-element method and smoothed particle hydrodynamics, which have specific advantages in modeling complex three-dimensional environmental fluid and particulate flows, are adopted as an effective way to illustrate environmental applications possibly happening in the real world. The theory of these methods and their relative advantages compared with traditional methods are discussed. Examples of 3-D flows on realistic topography including the flooding of a river valley as a result of a dam collapse and coastal inundation by a tsunami are introduced. Issues related to validation and quality data availability are also discussed. The results show that the simulations provide a valuable insight in a given situation for the security management of reservoir dams. Validation can only be performed where both the initial and final states can be very well characterized.

基于深度学习融合OBIA的黄土高原小流域淤地坝系提取

淤地坝对于防治黄土高原水土流失有不可替代的作用,因此精确提取淤地范围和淤地坝点位对研究黄土高原水土有重要意义。现有图像分类方法中缺乏对淤地坝地形特征的考虑,容易被误判为梯田或土堆。除此之外,自动提取研究多集中于淤地范围提取,淤地坝点位仍依赖人工判读。因此,提出一种自动提取淤地坝系的方法:通过深度学习融合面向对象的影像分析(OBIA)方法提取韭园沟流域淤地范围,再利用水文分析方法提取淤地坝点位。结果表明:本方法提取的淤地范围精准率、召回率、F1Score分别为81.97%、90.94%、89.70%,F1Score与仅使用OBIA方法相比提升了21.94%。淤地坝点位的自动识别准确率为81.08%,完整率为88.89%,与前人目视解译的准确度相近,并实现了淤地坝范围和淤地坝点位的全要素提取。研究结果可为黄土高原淤地坝空间布局优化和水土流失评估等分析提供重要基础数据。

庙堂沥青混凝土心墙堆石坝心墙基座嵌岩深度对基座应力的影响分析

沥青混凝土心墙堆石坝基座作为连接心墙与坝基的特殊结构,其受力状态对大坝的稳定至关重要。以在建的重庆庙堂沥青混凝土心墙堆石坝为例,选取其最大断面,建立二维模型进行有限元计算,分析探讨了基座在未嵌入基岩、半嵌入基岩、全嵌入基岩三种不同布置形式下的应力分布情况。结果表明,基座在基岩中的嵌入深度与基座内部的拉应力之间关联性较强。在蓄水期,不同布置形式之间拉应力相差最大可达334%,同时,由于廊道在蓄水期时受基座内部较大拉应力的影响,容易造成拉裂破坏,通过改变廊道在基座中的位置,降低廊道周围的拉应力,避免廊道产生破坏。廊道位置改变后,周围拉应力相比于原来下降幅度最大可达87%。

沥青混凝土心墙坝基座坡角研究

为研究基座坡角对沥青混凝土心墙坝基座应力变形的影响,以重庆巫山庙堂水库为例,采用非线性有限元方法分析了竣工期和蓄水期混凝土基座的应力变形特性及不同基座体型的拉应力图形。结果表明:在竣工期,基座上游侧或下游侧坡角增大时,基座水平位移、沉降和主应力值缓慢增大;在蓄水期,基座水平位移和沉降随基座上游侧或下游侧坡角减小逐渐减小,基座上游侧坡角增大可降低基座主应力值,而增大基座下游侧坡角会产生相反的效果;2种工况中基座两侧坡角同时增大会使基座压应力值增大,拉应力值减小;基座单侧坡角变化对拉应力图形的影响强于两侧坡角变化,建议在58~90°范围内采用上游侧坡角较大而下游侧坡角较小的基座,以改善基座应力变形情况。