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1.
Finite element method (FEM) is effectively used for evaluating roller-compacted concrete (RCC) dams, especially in high seismicity zones. The aim of this study is to investigate the effect of various reservoir lengths on the seismic response of a selected RCC dam under strong ground motion effects. Six different reservoir lengths, the lengths varies from h/2 to 10h (h, the height of dam), are used within finite element models. The hydrodynamic pressure of the reservoir water is modelled with the 2D fluid finite elements based on the Lagrangian approach. The horizontal and vertical components of the 1989 Mw 6.9 Loma Prieta earthquake are utilized in numerical analyses. The non-linear time-history analyses of those six models are investigated by using Drucker-Prager material model. According to the numerical analysis, it is obvious that the seismic behavior of the RCC dams is considerably dependent on the reservoir length. By increasing the length, we have obtained higher displacement values, which exist until the reservoir length reaches the 3h; at increased lengths, the values remain stable. This result proposes that 3h reservoir length is adequate to assess the seismic response of RCC dams. The principal tensile stresses are relatively lower in non-linear analysis compared to linear analyses. However, the principal compression stresses are close to each other in linear and non-linear analyses. The results imply that the non-linear response is influential on the total seismic response of a dam, which cannot be neglected in numerical analysis. 相似文献
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3.
The effect of reservoir length on seismic performance of gravity dams to near- and far-fault ground motions 总被引：1，自引：1，他引：0
In this article, the effect of reservoir length on seismic performance of gravity dams to near- and far-fault ground motions
is investigated. For this purpose, four finite element models of dam–reservoir–foundation interaction system are prepared
by using the Lagrangian approach. In these models, the reservoir length varies from H to 4H (H: the height of dam). The Folsom gravity dam is selected as a numerical application. Two different ground motion records of
1989 Loma Prieta earthquake are used in the analyses. One of ground motions is recorded in near fault; the other is recorded
in far fault. Also, the two records have the same peak ground acceleration. The study mainly consists of three parts to assess
the effects of reservoir length on the seismic performance of the concrete gravity dam. In the first part, the linear time-history
analyses of the four finite element models prepared for the Folsom gravity dam are performed. In the second part, the seismic
performance of the dam is evaluated according to demand–capacity ratio and cumulative inelastic duration. Finally, the nonlinear
time-history analyses of the finite element models of the dam are carried out by using Drucker–Prager yield criteria for dam
concrete. It is seen from the analyses results that the seismic behavior of the concrete gravity dams is considerably affected
from the length of the reservoir. The reservoir length of 3H is adequate for concrete gravity dams. The selection of ground motion is on of the important parts of seismic evaluation
of gravity dams. Also, the frequency characteristics of the ground motion having the same peak ground acceleration affect
the seismic performance of the dam. The near-fault ground motions are generally creates more stress on the dam body than far-fault
ground motions. The used performance approach provides a systematic methodology for assessment of the seismic performance
and necessity of nonlinear analyses for dam systems. 相似文献
4.
Landsliding triggered by reservoir operation: a general conceptual model with a case study at Three Gorges Reservoir 总被引：3，自引：0，他引：3
The Three Gorge Reservoir, one of the largest civil engineering projects in human history, dams the Yangtze River to form a 660-km-long and 1.13-km-wide reservoir. Today, although the project has been completed and is in normal operation, the on-going landslide initiation and movement in response to the reservoir operating is one of the main geologic hazards. The Huangtupo (meaning “yellow soil slope” in Chinese) Slope typifies such on-going landslides along the reservoir. Observations from a multi-year monitoring program conducted on this slope indicate that there are multiple slides on the reservoir banks that move episodically into the reservoir and their movements appear to be highly correlated with the initial and seasonal changes in the reservoir pool level. A hydro-mechanical numerical model is constructed to investigate the quantitative links among the episodic movements and the variations in pore water pressure, suction stress, hydrostatic reservoir water loading, and slope self-weight induced by the fluctuating water levels. Modeling results identify regions within the variably saturated slope where significant changes in stress occur during the periods of the initial impoundment that raised water levels from 68 to 135 m and that occur in response to seasonal fluctuations of the reservoir pool level between 145 and 175 m. We find that the rise or decline of reservoir pool level can either increase or decrease the stability of landslide. In general, hydrostatic reservoir water loading has positive correlation with the stability; pore water pressure and suction stress have negative correlation with the stability; and the effects of slope self-weight depend on the dip angle and mechanical properties of sliding surface. 相似文献
5.
在深厚覆盖层上建筑的高砾石土心墙堆石坝得到迅猛发展的同时,正确地认识坝体变形规律和合理地数值模拟是不可忽视的问题。堆石坝变形的影响因素多且复杂,监测成果的分析对研究上述问题具有重要意义。以硗碛大坝的监测资料为基础,结合坝体的填筑和蓄水过程,对位于深厚覆盖层上的百米级砾石土心墙堆石坝的变形规律进行了系统分析,并与其坝高、覆盖层深度、河谷宽度等方面都具有相似性的毛尔盖大坝监测资料进行了对比分析。通过分析两座大坝监测结果,对坝体的变形特性进行了规律性总结,对湿化和蠕变作用以及水库填筑和蓄水过程对坝体变形的影响有了一定认识。分析结论可为正确认识以及合理模拟和预测同类坝体的变形特性提供参考和依据。 相似文献
6.
Several small reservoirs and a large number of check dams had been constructed in the Wangkuai reservoir watershed after 1970s, and flood time series lacked stationarity, which affected the original design flood hydrographs for the Wangkuai reservoir. Since the location, storage capacity and drainage area of the large number of check dams were unknown, we present a method to estimate their total storage capacities (TSC) and total drainage areas (TDA) by using the recorded rainstorm and flood data. On the basis of TSC and TDA, the flood events which occurred in an undisturbed period were reconstructed under current conditions to obtain a stationary flood series. A frequency analysis was subsequently performed to assess the design flood peak and volume for both small and medium design floods with a 10–200 year return period. For large and catastrophic floods, it was assumed that the upstream check dams and small reservoirs would be destroyed, and water stored in these hydraulic structures were re-routed to the Wangkuai reservoir by unit hydrograph. The modified flood peak and volume decreased for floods with a 10–200 year return period when compared to the current design flood. But for large design floods with a return period exceeding 500 years, peak discharge increased. This study provides a new method for design flood calculation or modification of the original design flood in watersheds with a large number of check dams. 相似文献
7.
库水升降作用下浮托减重型滑坡稳定性研究 总被引：3，自引：0，他引：3
大坝建成后形成众多涉水滑坡。为研究库水位升降作用对涉水边坡稳定性的影响机制,基于重大涉水滑坡分类,针对浮托减重型滑坡,运用自主研制的滑坡模型试验系统,建立浮托减重型滑坡模型进行库水升降作用试验。试验结果表明,库水位升高,滑坡模型体内有效应力随之减小;库水位降低,有效应力随之增大。对于模型试验过程,运用Geo-studio软件进行渗流及稳定性计算,对照试验结果与数值模拟结果得出土压力及孔隙水压力渗流模拟变化情况与试验实测变化情况基本吻合。库水位上升阶段,滑坡稳定性系数随之减小;库水位下降阶段,滑坡稳定性系数随之降低。由此分析得出库水升降对浮托减重型滑坡稳定性的影响规律是：库水位上升引起滑坡体内阻滑段有效应力随之减小,导致滑坡稳定性降低;库水位下降引起滑坡体内阻滑段有效应力随之增加,使得滑坡稳定性提高。 相似文献
8.
The dams are built to supply water needs of people, to produce electricity and to supply irrigation water in agricultural activities since ancient times. They are very important because of their contribution to energy production. The construction of dams is very difficult and costly. It is vital that they are resistant to all kinds of effects, since they are built to prevent flooding in the region. The most important and dangerous of these effects are earthquake forces. It is very important that the dams are designed to be durable. In this study, the Darideresi-II Dam reservoir located in Isparta was examined in terms of the behavior under various earthquake loads. To reflect the behavior of the dam in a more realistic way, the finite element method is used. While developing this model, the material specifications and boundary conditions are taken into account. The dam reservoir was modeled using ANSYS program, and its behavior under different earthquake accelerations was investigated. The deformation and stress forces under earthquake accelerations are taken into account. By examining these results, it is interpreted how the Darideresi-II Dam reservoir will behave during earthquake. 相似文献
9.
In this paper, the gravity dam–water–foundation system including the physical and mechanical properties of the sediment at the reservoir bottom is modelled using a finite element and infinite element coupling model. The sediment at the reservoir bottom has been assumed to be a viscoelastic solid medium. The effects of thickness, elastic modulus, Poisson's ratio and material damping of the sediment on the response of the dam have been studied. The related numerical results from this study illustrated that the existence of the sediment at the bottom of the reservoir has significant effects on the response of concrete gravity dams since the soft layer of the sediment plays two main roles in the dam–water–foundation system, the energy dissipation of the system and the amplification of the incident wave on the water–sediment interface. It is the amplified acceleration on the water–sediment interface that results in different mechanisms of the effect of the sediment on the response of the dam. Therefore, apart from the incident wave, the thickness, the softness and the damping ratio of the sediment can also affect the response of the dam. 相似文献
10.
Gang Deng Kui Cao Rui Chen Xingxing Zhang Qi Yin Hao Zhou 《Environmental Earth Sciences》2018,77(1):25
Internal erosion is the most common reason which induces failure of embankment dams besides overtopping. Relatively large leakage is frequently concentrated at defects of impervious element, and this will lead to eventual failure. The amount of leakage depends not only on integrity of impervious element, but also on dam height, shape of valley, shape of impervious element and water level in reservoir. The integrity of impervious element, which represents the relative level of seepage safety, is not easy to be determined quantitatively. A simple method for generalization of steady seepage state of embankment dams with thin impervious element is proposed in this paper. The apparent overall value of permeability coefficient for impervious element can be obtained by this method with reasonable accuracy and efficiency. A defect parameter of impervious element is defined as an index to characterize seepage safety of embankment dams. It equals the ratio of the apparent overall value of permeability coefficient to the measured value in laboratory for intact materials. Subsequently, seepage safety of three dams is evaluated and the evolution of defect level of impervious element of dams is investigated. It is proved that the newly proposed method in this paper is feasible in the evaluation of relative seepage safety level of embankment dams with thin impervious element. 相似文献
11.
针对澜沧江高坝大库对物质迁移转化的影响问题, 自主研发了深库智慧采样设备和潜流带动态监测系统, 于2016年、2017年、2018年开展了澜沧江上游1 290 km的9个梯级水库的监测分析, 实现了280 m最大工作水深的垂向分层水样与沉积物样无扰动采集和潜流带水土环境界面的多指标监测。研究发现: 梯级水库促进了水体中生物有效磷、氨氮占比和沉积物中生物有效磷释放的沿程增加;沉积物中甲基汞的分布与泥沙颗粒沉降有关, 受到水力停留时间和库龄的共同调控;温室气体的排放通量因建坝有所提升, 但远低于世界平均水平;潜流带因干湿交替频率和面积的增加, 加强了水库关键带脱氮和温室气体削减效应;水库中微生物群落并未因建坝隔离, 在沿程和垂向上, 水温都是其关键影响因子。 相似文献
12.
小型水坝随着服役时间的增长,其面临的安全、经济和生态方面问题日益突出,针对一些修复价值较低的病险水坝,实施降等或报废拆除已成为一种综合最佳的管理措施。拆坝后,原库区大量淤沙无控释放将改变原有河道形态,对水生生物栖息地造成影响。为预测拆坝后河道在不同时间尺度上的变化特征,以长江流域乌江水系内的西河水坝为研究对象,建立二维水沙数学模型,分别研究了拆坝后水沙输运造成的短期和长期河床形态变化。结果表明:拆坝后短期内,坝址上游主河道发生了强烈的冲刷下切,且水库淤沙前缘部分出现了显著的淤积抬高,相比而言,坝址下游河床变化并不明显,只有坝下河段及河口附近出现较显著的泥沙淤积;在拆坝后长期的河床演变过程中,坝址上下游河道均发生了不同程度的冲刷下切,拆坝2年后下游河床逐渐趋于稳定,而上游主河道由冲刷下切转化为冲淤交替的演变趋势,河床形态不断调整变化。本研究可为病险坝和小水电报废拆坝后的河道治理、水生生物栖息地修复提供参考依据。 相似文献
13.
The geologic structures associated with several selected dam sites in Jordan and the tectonic effects on dam foundations and reservoir margins are reviewed. Rock defects, especially discontinuities represented by faults and closely spaced, open joints are investigated. Related problems, such as loss of water from the reservoir by seepage and leakage within the dam foundation are evaluated. The regional seismicity is analyzed and a design earthquake is established for each dam site.
Two major embankment dams are investigated, together with two large proposed dams and several small dams.
This paper discusses in some detail the regional setting and site-specific geology, and the occurrence, size and inclination of faults and joints at each dam site. Moreover, the effects of the faults on the operational performance of each dam are described and specific techniques are used or proposed for remediation are outlined.
The study shows that the combination of faults and joint features cause leakage problems at the operational dams in Jordan. Although, preventive measures such as grouting have been implemented, further leakage and/or seepage problems are anticipated and a monitoring system is needed to control and foresee such problems.
Jordan is an earthquake-prone region. Consequently, it is recommended that the design of embankment dams in the vicinity of the Dead Sea-Jordan Valley Rift should include such considerations as dynamic loading and associated hazards, including embankment acceleration zoning, foundation liquefaction risk and rockhead rupture. The magnitude of the design earthquake at each dam site can be estimated following the guidelines of ICOLD (1989), which are based on probabilistic seismic hazard analysis. 相似文献
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Zhang Wenbing Shen Zhenzhong Chen Guanyun Zhang Wanlin Xu Liqun Ren Jie Wang Fei 《Hydrogeology Journal》2021,29(5):1831-1855
Seepage analysis and assessment of the effect of seepage control at reservoir sites are essential parts of dam design and operations, and of considerable significance for the safe and economic design of the masses and hydraulic structures associated with reservoir sites. In this study, a systematic process is provided for the optimal design and assessment of seepage control of reservoir dams under karst development conditions. A reservoir dam planned for construction in the middle-upper reaches of the Huayang River in China is selected as a case example for illustration. A three-dimensional equivalent continuum seepage finite-element numerical model is applied to investigate the effectiveness of the proposed and optimized seepage-control schemes, and it is calibrated by an inversion analysis of the initial seepage field based on the flexible tolerance method and field penetration test data. By analyzing the sensitivity of seepage discharge to the length and depth of the grouting curtain, a safe and economic seepage-control optimization scheme is suggested. Additionally, the sensitivity of seepage discharge to the hydraulic conductivity of the limestone layer is analyzed, and the results show that the hydraulic conductivity of the limestone layer has a significant impact on the seepage discharge of the reservoir site. The methodology and results derived from this study can provide technical support and reference for the optimal design and assessment of seepage control for reservoir dam engineering under karst conditions.
相似文献16.
Khamis Naba Sayl Nur Shazwani Muhammad Ahmed El-Shafie 《Environmental Earth Sciences》2017,76(10):368
The major limitation in planning water harvesting is the lack of knowledge in the estimation of surface area and storage volume at any depth of dam reservoir. The area–volume–elevation (AVE) curve of a reservoir plays a key role in estimating the most suitable depth, optimum surface area and highest capacity of reservoir storage. The existing methods to estimate the AVE curve are costly and time-consuming and require laborious work. This study attempts to develop a method to optimize the AVE curve for earth dams, using the digital elevation model generated by the Shuttle Radar Topography Mission (SRTM) data, and integrate it with the geographic information system (GIS), known as the GIS–SRTM. The proposed method was tested using field data in the Western Desert of Iraq, which is an arid environment. Three constructed small earth dams were selected for this study. The AVE curves were extracted for Horan 2 (H2), Al-gara 2 (G2) and Al-gara 4 (G4) earth dams. Comprehensive analyses have been carried out to evaluate the performance of the AVE curves using the proposed GIS–SRTM method and the field data. From the comparison, the proposed GIS–SRTM method was able to produce reliable AVE curves with a relative error less than 20%. Additionally, the proposed method was less time-consuming and the AVE curves can be visualized immediately. The proposed GIS–SRTM method is relatively supportive in analyzing spatial data to select the optimal site for rainwater harvesting and prevent excessive evaporation losses. 相似文献
17.
Kiyoumars Roushangar Saeede Garekhani Farhad Alizadeh 《Geotechnical and Geological Engineering》2016,34(5):1313-1326
Because of their sensitive structure, earth dams might face failure due to seepage phenomenon. In order to prevent such failure, some equipment like piezometers are installed in the body or foundation of earth dams. This study investigated the importance of piezometer installation level in dam body or foundation using mutual information–wavelet–Gaussian process regression. 27 Piezometers in three section along with reservoir level were employed to predict one-step-ahead seepage discharge of Zonouz earth dam. The daily data of 1 year of piezometer level and reservoir level were collected for this purpose. In order to find the best possible input combination, three groups of modeling scenarios were defined using piezometers and reservoir level time series. As some input combinations had more than two variables, decomposed time series were imposed into mutual information (MI) tool in order to decrement input variables and find the most correlated input–output features. Afterward, mentioned features were imposed into optimized Gaussian process regression (GPR) to be predicted. Different kernels were selected as core tool of GPR, but results demonstrated the capability of radial basis function (RBF) kernel. GPR–RBF structure were optimized using cross-validation technique. Results indicated that input combination including piezometer level and reservoir level of section II, especially piezometer 203 time series led to the best result among all scenarios. 相似文献
18.
Nida Samad Muhammad Hamid Chauhdry Muhammad Ashraf Muhammad Saleem Qudsia Hamid Umair Babar Hassan Tariq Muhammad Shahid Farid 《Arabian Journal of Geosciences》2016,9(6):466
Sediment yield is the amount of erosional debris from drainage basin deposited in reservoirs. The economic life of storage reservoir depends upon the estimation of the time it takes for the reservoir to be filled with the deposition of sediments. This research is based on assessing the sediment yield in Rawal Dam catchment by using Soil and Water Assessment Tool (SWAT) model. Digital Elevation Model (DEM), land use maps, soil maps, and weather data of the study watershed were used as input to SWAT model. Monthly sedimentation data of year 2010 and discharge data from 1998 to 2005 is being used for model calibration and validation, respectively. Whereas simulations are being generated from 1998 to 2011 for both sedimentation and discharge. Modified Universal Soil Loss Equation (MUSLE) was used for the estimation of sediment yield. The Nash and Sutcliffe coefficient of the model was found to be 0.79 which depicts its effectiveness. After the estimation of the sediment yield and discharge by using SWAT model, double mass curve was used to evaluate the sedimentation rate. The rate of sediment transport can be reduced by the construction of check dams. Various sites have also been proposed for check dams construction to prevent the sediments transported into the Rawal Catchment. 相似文献
19.
心墙是否会发生水力劈裂关系土石坝的安全,该问题的难点和关键之一是水力劈裂的发生机制和条件。利用自制模型,在2种不同加压速率条件下,对有无初始裂缝和5种不同初始裂缝深度的试样进行了水力劈裂试验;结合数值模拟和CT观测试验,验证了水力劈裂的楔劈效应机制-当水压力作用在初始裂缝形成的劈背上,引起劈刃上的力超过临界值时就可能导致发生水力劈裂。研究结果表明：初始裂缝深度越大、加压速率越高,越容易发生水力劈裂。为避免土石坝发生水力劈裂破坏,应注意心墙迎水面的施工质量和平整性,宜采用较慢的蓄水方案。 相似文献
20.
广西岩溶区地下河分布特征与开发利用 总被引：5，自引：0，他引：5
广西岩溶地区已查明地下河445条,其分布受地质、地貌条件控制。地下河出口主要分布于灰岩地层,在白云岩地区分布最低。以峰丛洼地区地下河分布数量最多、规模大,其次为峰林谷地和平原区,岩溶丘陵区地下河数量少、规模小。不同岩溶地貌区的地下河及开发利用带来不同的环境问题,峰丛洼地区以内涝最严重,峰林谷地和平原区的地下河水开发常造成塌陷,岩溶丘陵地区的地下河水污染严重。开发利用方式主要为出口建坝蓄水,天窗提水,地下河堵洞成库,堵截地下河引水发电,建地表、地下联合水库。 相似文献