海绵吸收层法在坝-库水瞬态动力相互作用分析中的应用

将海绵层与Sommerfeld人工边界结合起来模拟无穷水库的辐射阻尼效应,并结合有限元法在时域内分析坝—库水动力相互作用。计算了刚性坝面瞬态动水压力及柔性坝—库水动力相互作用的分析,结果说明这种方法在时域内模拟无穷水库动水压力波向上游的辐射阻尼效应是适合的。但需注意海绵层的体积阻力系数不能取得太大。

基于SBFEM的坝-库水相互作用分析

将W o lf和Song提出的比例边界有限元法(sca led boundary fin ite e lem en t m ethod,简称SBFEM)应用于坝-库水相互作用分析.在库水不可压缩假定的前提下推导了坝面动水压力与附加质量矩阵的基本方程.二维重力坝和三维拱坝坝面动水压力的算例表明,与有限元法比较,SBFEM计算精度明显提高,同时由于具有降维的特点,计算工作量也在很大程度上有所节约.还分析了库底和水面坡度变化以及水库边界形状适当变化对动水压力分布和数值大小的影响.结果表明,一般情况下水库边界的变化对动水压力的分布形状基本上不发生影响,对动水压力数值大小也影响不大.

基于FEM-SBFEM的坝-库水动力耦合简化分析方法

在坝-库水动力流固耦合分析中,比例边界有限元方法(SBFEM)仅需对流固交界面进行离散,就可以模拟半无限域库水,节省了节点自由度个数,具有较高效率。但采用数值方法处理动水压力时得到的附加质量阵为满阵,进行大规模的面板坝弹塑性动力分析时用于求解方程的时间较多。该文根据动水压力附加质量阵的物理意义与分布特点,提出了一种基于FEM-SBFEM的坝与库水的动力耦合简化计算方法,仅需提供一个保留系数β(0≤β≤1.0)即可实现不同程度的动水压力附加质量阵化简,简单易行;将其应用在面板坝与库水的动力弹塑性耦合计算中,建议了β的取值范围,在保证具有良好精度的前提下大幅提高了计算效率。

基于高阶时域人工边界条件的坝-水相互作用分析方法

在大坝的抗震分析和设计中,应该考虑大坝与半无限库水之间的动力相互作用。地震作用下结构与可压缩水之间动力相互作用分析的关键问题是模拟波在无限域水中的传播。基于一种稳定且便于工程应用的时空局部高阶人工边界条件,建立地震作用下坝-水相互作用的有限元分析方法。该时域整体分析方法恒稳定,且对倾斜坝面或有库底淤积泥砂等复杂工况下的坝-水相互作用分析都具有高精度。通过数值算例揭示了坝面坡角和淤砂层厚度对刚性坝面动水力的影响:动水压力最不利位置约靠近坝水交界面底部,坝面底部动水力峰值随坝面坡角的增大而增大,垂直坝面的坝底动水力峰值最大。另外,淤积泥砂有吸收库水地震反应能量的吸能作用,淤砂层越厚,吸能效果越明显。

大坝坝址地下水质的演变及其示踪意义——以新安江大坝为例

蓄水条件下 ,坝址渗流场内液 固两相间的物理化学作用由于人类工程活动而趋于更加的广泛、深入而剧烈 ,从而导致场内地下水质的复杂多变。本文以新安江水电站为例 ,论述了坝址区地下水质演变的基本特征 ,如水的酸碱度的异常变化 (pH =6 3 2～ 11 5 5 )、水质组分存在形式的多样性、以及水化学类型的多样性等 ,强调了大坝工程对于地下水质的演变所施加的影响。此外 ,还揭示了区内地下水质演变所具有的示踪意义 ,即不仅反映了水 岩系列间的相互作用 ,而且还反映了坝址渗流的宏观动态以及坝踵帷幕体的防渗效果及其时效。

深覆盖层上心墙堆石坝动力分析中库水影响研究

应用有限元方法对深覆盖层地基和岩石地基上的堆石坝分别进行计及和忽略动水压力的动力分析， 探讨了针对堆石坝而异于混凝土坝与库水相互作用的一些规律， 并对此作出物理成因解释， 较系统地研究了动水压力对深覆盖层地基上的心墙堆石坝动力响应的影响。

地震作用下水库坝体与水体相互作用数值模拟

地震作用下水库坝体受迫振动,推动坝后水体波动,造成水体动压作用于坝体,形成坝-水耦合作用,影响坝体安全。为了评估坝体振动引起的水面波动及坝体所受动水荷载作用,建立坝体动边界条件下的不可压水体运动数学模型,模拟了地震波作用下的坝后水体波动和动力荷载。结果表明,在忽略坝体自身弹性变形的条件下,地震作用下坝体激发的水体表面波动、波高和波能随地震波振幅增大呈线性增长;波高随水深呈非线性增长;坝体所受动水压力主要来自附加质量力和静水压力,地震作用下库区地面的水平运动对涌浪波高和坝体动水压力影响较弱。

坝——水动力耦合作用分析的数学模型及其求解方法

坝－水动力耦合作用分析是现代水工抗震设计的重要课题之一。本文描述了该问题的数学模型及其求解方法，重点报告我们在这个领域应用加权残量法所获得的重要成果，研究结果表明，我们所提出的分析方法简便有效，具有较高的计算效率，值得在工程中推广应用。

Impacts of Agricultural Non-point Pollution on Water-source Area in Songhua Dam

[Objective] The aim was to research impacts of agricultural non-point pol- lution on water-source region in Songhua Dam, laying foundation for control of water pollution and scientific protection of water-source region. [Method] Water in Muyang River, lengshui River and Zizania aquatica region were sampled to measure content of pollutants in water and conclude relation between water contamination and agri- cultural non-point pollution to find the major cause of pollution. [Result] Organic pollu- tant in Muyang River was higher; N and P contents in Lengshui River were higher; the measured indices in Zizania aquatica region excessively exceeded related stan- dard. [Conclusion] The chemical fertilizers and pesticides are the toxic materials lead- ing to water contamination and constitute a major cause of pollution in Songhua Dam water-source region. Agricultural non-point pollution should be controlled in a scientific way.

Influence of a large dam on the longitudinal patterns of fish assem- blages in Qingyi Stream

Using seasonally collected data(2009-2010) from 15 sampling sites that represent first- to fifth-order streams within the Qingyi watershed,we examined the spatio-temporal patterns of fish assemblages along two longitudinal gradients to explore the effects of a large dam on fish assemblages at the watershed scale.No significant variation was observed in either species richness or assemblage structure across seasons.Species richness significantly varied according to stream order and gradient.Dam construction appeared to decrease species richness upstream substantially,while a significant decrease between gradients only occurred within fourth-order streams.Along the gradient without the large dam,fish assemblage structures presented distinct separation between two neighboring stream orders,with the exception of fourth-order versus fifth-order streams.However,the gradient disrupted by a large dam displayed the opposite pattern in the spatial variation of fish assemblages related with stream orders.Significant between-gradient differences in fish assemblage structures were only observed within fourth-order streams.Species distributions were determined by local habitat environmental factors,including elevation,substrate,water depth,current discharge,wetted width,and conductivity.Our results suggested that dam construction might alter the longitudinal pattern in fish species richness and assemblage structure in Qingyi Stream,despite the localized nature of the ecological effect of dams.

Real-Time Spreading Thickness Monitoring of High-core Rockfill Dam Based on K-nearest Neighbor Algorithm

During the storehouse surface rolling construction of a core rockfilldam, the spreading thickness of dam face is an important factor that affects the construction quality of the dam storehouse' rolling surface and the overallquality of the entire dam. Currently, the method used to monitor and controlspreading thickness during the dam construction process is artificialsampling check after spreading, which makes it difficult to monitor the entire dam storehouse surface. In this paper, we present an in-depth study based on real-time monitoring and controltheory of storehouse surface rolling construction and obtain the rolling compaction thickness by analyzing the construction track of the rolling machine. Comparatively, the traditionalmethod can only analyze the rolling thickness of the dam storehouse surface after it has been compacted and cannot determine the thickness of the dam storehouse surface in realtime. To solve these problems, our system monitors the construction progress of the leveling machine and employs a real-time spreading thickness monitoring modelbased on the K-nearest neighbor algorithm. Taking the LHK core rockfilldam in Southwest China as an example, we performed real-time monitoring for the spreading thickness and conducted real-time interactive queries regarding the spreading thickness. This approach provides a new method for controlling the spreading thickness of the core rockfilldam storehouse surface.

Experimental study on characteristics of trapping and regulating sediment with an open-type check dam in debris flow hazard mitigation

Beam dams are a highly effective and commonly used open-type check dam in debris-flow hazard mitigation. In this study, dimensional analysis was used to obtain empirical equations for quantitatively determining the sediment-trapping and flow-regulating characteristics of a beam dam. To determine the coefficients of the empirical equations, flume experiments were conducted to simulate the trapping and regulating processes. The flow pattern, trapping, and regulating characteristics were investigated when debris flows passed through a beam dam. Debris-flow bulk density and peak discharge, and sediment-trapping ratios, were measured directly and indirectly. The results showed that three blocking actions occurred, and that blockage-breaking considerably influenced the trapping and regulating performance of the beam dam. The relative opening size and the sediment concentration were the two main factors affecting the performance of the beam dam. The ratio of trapping sediment decreased with relative opening, and increased with sediment concentration as well as reducing ratio of bulk density and reducing ratio of peak discharge. The sediment concentration and relative opening were the leading factors influencing the trapping and regulating sediment of a beam dam, followed by flume gradient. The results showed that the calculated values obtained using empirical equations were in good agreement with the values derived from the experiments, and that the deviation was acceptable. Finally, taking Zechawa Gully as an example, using the empirical equations we designed the opening size of a beam dam aimed to trap sediment and regulate peak discharge of debris flow in the main gully.

Hydro-mechanical coupling mechanism on joint of clay core-wall and concrete cut-off wall

The joint of clay core-wall and concrete cut-off wall is one of the weakest parts in high earth and rockftll dams.A kind of highly plastic clay is always fixed on the joint to fit the large shear deformation between clay core-wall and concrete cut-offwall,so the hydro-mechanical coupling mechanisms on the joint under high stress,high hydraulic gradient,and large shear deformation are of great importance for the evaluation of dam safety.The hydro-mechanical coupling characteristics of the joint of the highly plastic clay and the concrete cut-off wall in a high earth and rockfill dam in China were studied by using a newly designed soil-structure contact erosion apparatus.The experimental results indicate that：1） Shear failure on the joint is due to the hydro-mechanical coupling effect of stress and seepage failure.The seepage failure will induce the final shear failure when the ratio of deviatoric stress to confining pressure is within 1.0-1.2; 2） A negative exponential permeability empirical model for the joint denoted by a newly defined principal stress function,which considers the coupling effect of confining pressure and axial pressure on the permeability,is established based on hydro-mechanical coupling experiments.3） The variation of the settlement before and after seepage failure is very different.The settlement before seepage failure changes very slowly,while it increases significantly after the seepage failure.4） The stress-strain relationship is of a strain softening type.5） Flow along the joint still follows Darcian flow rule.The results will provide an important theoretical basis for the further evaluation on the safety of the high earth and rockfill dam.

Theory and Application of System Integration for Real-Time Monitoring of Core Rock-Fill Dam Filling Construction Quality

The theory and method of system integration for the real-time monitoring of core rock-fill dam filling con- struction quality are studied in this paper. First, the importance analysis of system integration factors is carried out with the analytic hierarchy process. Then, according to the analysis result of integration factors, the conceptual model of system integration is built based on function integration, index integration, technology integration and information integration, the index structure of core rock-fill dam filling construction quality control is constructed and the method of function integration and technology integration is studied. The mathematical model of process monitoring is built according to monitoring objective, process and indexes. Research results have been applied in Nuozhadu core rock-fill dam construction management, realizing system integration through building appropriate monitoring work flow and comprehensive information platform of digital dam.

Dam-break Flood Simulation under Various Likely Scenarios and Mapping Using GIS:Case of a Proposed Dam on River Yamuna,India

The precision modeling of dam break floods can lead to formulation of proper emergency action plan to minimize flood impacts within the economic lifetime of the assets.Application of GIS techniques in integration with hydrological modeling for mapping of the flood inundated areas can play a momentous role in further minimizing the risk and likely damages.In the present study,dam break analysis using DAMBRK model was performed under various likely scenarios.Probable Maximum Flood (PMF)calculated for a return period of 1000 years using deterministic approach was adopted for dam break analysis of the proposed dam under various combinations of breach dimensions.The available downstream river cross-sections data sets were used as input in the model to generate the downstream flood profile.Dam break flow depths generated by the DAMBRK model under various combinations of structural failure are subsequently plotted on Digital Elevation Model(DEM)of the downstream of dam site to map the likely affected area.The simulation results reveals that in one particular case the flood without dam may be more intense if a rainfall of significant intensity takes place.

SEFIDROOD RIVER SUB-WATERSHED-DAM-ESTUARY AND DEGRADATION MODEL:A HOLISTIC APPROACH IN IRAN

The major concern of this article is to address the shortcoming and outgoing effects of the human activities on the landscape patterns and their consequences in the Sefidrood River watershed in Iran. A flow of data includes three inputs; each of them belongs to one part of three zones of a fluvial system. The three parts of the Sefidrood River fluvial system include Zone 1,a sub-watershed as degradation modeling site,Zone 2,Sefidrood Dam as dam site,and Zone 3,17km away from the Sefidrood River path to the Caspian Sea as ending point site. The degradation model in the Zone 1 provides a suitable mean for decision support system to decrease the human impacts on each small district. The maximum number for degradation coefficient belongs to the small district with the highest physiographic density,relatively cumulative activities,and a lower figure for the habitat vulnerability. The human degradation impact were not limited to the upstream. The investigation to the Sefidrood Dam and ending point of the Sefidrood River depicts that sedimentation continues as a significant visual impact in the Sefidrood Dam reservoir and the estuary.

Optimizing Earth Allocation for Rock-Fill Dam Construction

An optimal allocation of earth is of great significance to reduce the project cost and duration in the construction of rock-fill dams. The earth allocation is a dynamic system affected by various time-space constraints. Based on previous studies, a new method of optimizing this dynamic system as a static one is presented. In order to build a generalized and flexible model of the problem, some man-made constraints were investigated in building the mathematic model. Linear programming and simplex method are introduced to solve the optimization problem of earth allocation. A case study in a large-scale rock-fill dam construction project is presented to demonstrate the proposed method and its successful application shows the feasibility and effectiveness of the method.

Coupled 2D Hydrodynamic and Sediment Transport Modeling of Megaflood due to Glacier Dam-break in Altai Mountains,Southern Siberia

One of the largest known megafloods on earth resulted from a glacier dam-break,which occurred during the Late Quaternary in the Altai Mountains in Southern Siberia.Computational modeling is one of the viable approaches to enhancing the understanding of the flood events.The computational domain of this flood is over 9460 km2 and about 3.784 × 106 cells are involved as a 50 m × 50 m mesh is used,which necessitates a computationally efficient model.Here the Open MP(Open Multiprocessing) technique is adopted to parallelize the code of a coupled 2D hydrodynamic and sediment transport model.It is shown that the computational efficiency is enhanced by over 80% due to the parallelization.The floods over both fixed and mobile beds are well reproduced with specified discharge hydrographs at the dam site.Qualitatively,backwater effects during the flood are resolved at the bifurcation between the Chuja and Katun rivers.Quantitatively,the computed maximum stage and thalweg are physically consistent with the field data of the bars and deposits.The effects of sediment transport and morphological evolution on the flood are considerable.Sensitivity analyses indicate that the impact of the peak discharge is significant,whilst those of the Manningroughness,medium sediment size and shape of the inlet discharge hydrograph are marginal.

Dynamic analysis of dam-reservoir-foundation interaction using finite difference technique

Time domain dynamic analysis of inclined dam-reservoir-foundation interaction was conducted using finite difference method （FDM）. The Timoshenko beam theory and the Euler-Bemoulli beam theory were implemented to draw out governing equation of beam. The interactions between the dam and the soil were modeled by using a translational spring and a rotational spring. A Sommerfeld＇s radiation condition at the infinity boundary of the fluid domain was adopted. The effects of the reservoir bottom absorption and surface waves on the dam-reservoir-foundation interaction due to the earthquake were studied. To avoid the instability of solution, a semi-implicit scheme was used for the discretization of the governing equation of dam and an explicit scheme was used for the discretization of the governing equation of fluid. The results show that as the slope of upstream dam increases, the hydrodynamic pressure on the dam is reduced. Moreover, when the Timoshenko beam theory is used, the system response increases.

Long-term stability analysis of large-scale underground plant of Xiangjiaba hydro-power station

Numerical analysis of the optimal supporting time and long-term stability index of the surrounding rocks in the underground plant of Xiangjiaba hydro-power station was carried out based on the rheological theory. Firstly,the mechanical parameters of each rock group were identified from the experimental data; secondly,the rheological calculation and analysis for the cavern in stepped excavation without supporting were made; finally,the optimal time for supporting at the characteristic point in a typical section was obtained while the creep rate and displacement after each excavation step has satisfied the criterion of the optimal supporting time. Excavation was repeated when the optimal time for supporting was identified,and the long-term stability creep time and the maximum creep deformation of the characteristic point were determined in accordance with the criterion of long-term stability index. It is shown that the optimal supporting time of the characteristic point in the underground plant of Xiangjiaba hydro-power station is 5-8 d,the long-term stability time of the typical section is 126 d,and the corresponding largest creep deformation is 24.30 mm. While the cavern is supported,the cavern deformation is significantly reduced and the stress states of the surrounding rock masses are remarkably improved.