Seismic stability of earth-rock dams using finite element limit analysis     

《Soil Dynamics and Earthquake Engineering》2014

In this study, a finite element limit analysis method is developed to assess the seismic stability of earth-rock dams. A pseudo-static approach is employed within the limit analysis framework to determine the lower and upper bounds on the critical seismic coefficients of dams. The interlocking force in the soil is considered, and the rockfill material is assumed to follow the Mohr–Coulomb failure criterion and an associated flow rule. Based on the native form of the failure criterion, the lower and upper bound theorems are formulated as second-order cone programming problems. The nonlinear shear strength properties of rockfill materials are also considered. The developed finite element limit analysis is applied to two different types of earth-rock dams. The results indicate that the rigorous lower and upper bounds are very close even for rockfill materials with large internal friction angles. The failure surfaces are easily predicted using the contour of the yield function and the displacement field obtained by the limit analysis method. In addition, the pore water pressures are modelled as external forces in the limit analysis to assess the seismic stability of earth-rock dams in the reservoir filling stage.  相似文献   

陕北黄河中游淤地坝拦沙功能失效的判断标准   总被引：7，自引：0，他引：7  

高云飞  郭玉涛  刘晓燕  何兴照 《地理学报》2014,69(1):73-79

利用2011 年第一次全国水利普查中4157 座骨干坝数据、1989 年陕北淤地坝调查中1640座中小坝数据,分别计算了1950-2011 年期间骨干坝、1956-1989 年期间中小坝的逐年平均淤积比例,得到截至2011 年,1980 年前修建骨干坝的平均淤积比例基本稳定,平均值为0.77,1980 年后开始逐渐下降;截至1989 年,1980 年前修建中小坝的平均淤积比例基本稳定,平均值为0.88,1980 年后开始逐渐下降的变化趋势,确定平均淤积比例0.77、0.88 分别为骨干坝、中小坝拦沙能力失效的判断标准。利用陕北淤地坝调查数据计算得到的骨干坝拦沙功能失效判断一致;在无定河、延河流域,水文站输沙数据的变化趋势与淤地坝是否拦沙显著相关。最后从淤地坝工程结构的角度,剖析了排水排沙位置的改变是判断标准形成的原因。  相似文献   

泥石流拦砂坝底扬压力分布及影响因素试验     

陈兴长  陈慧  游勇  柳金峰 《岩土力学》2018,39(9):3229-3236

泥石流拦砂坝底的扬压力会抵消坝体的部分有效荷重,影响其抗倾覆稳定性。为了研究拦砂坝底扬压力的分布规律及其影响因素,设计制作了拦砂坝模型和扬压力采集系统,开展了不同沟床坡度和不同坝前堆积条件下的扬压力模拟试验。试验结果表明,扬压力自坝踵至坝趾不断减小,且与渗流距离呈线性关系,当坝前有堆积物时相关系数绝对值达到0.98以上;沟床坡度明显影响坝底扬压力的分布。随着沟床坡度的增加,扬压力不断减小,且对坝踵处扬压力的影响较坝趾处更大;坝底和坝前堆积物的渗透性对扬压力的影响也很显著,它们的渗透性越差,扬压力就越小;坝前堆积物的渗透性还显著影响扬压力的分布规律,渗透性越差,其分布规律性就越强。研究成果为深入研究泥石流拦砂坝底扬压力的作用过程和作用机制奠定了基础。  相似文献   

Effect of ground-motion asynchronism on the equivalent acceleration of earth dams     

Emilio Bilotta  Luca PaganoStefania Sica 《Soil Dynamics and Earthquake Engineering》2010

Under seismic loads the deformability of an earth dam may induce several effects, including ground-motion amplification and asynchronism between different points of the dam embankment. The paper analyses the asynchronous effects occurring in two existing earth dams, representing well-documented case histories: the El Infiernillo Dam (Mexico) and the Camastra Dam (Italy). Asynchronous effects are analysed by theoretical predictions of the dam seismic response by adopting an advanced dynamic approach, which takes into account the main features that dam soils exhibit under cyclic loading conditions. For different potentially unstable masses within the dam embankment, equivalent accelerations were computed as the ratio between the resultant of the inertial forces and the weight of the volume V associated to the unstable mass. With the exception of very cortical sliding surfaces – not significant for dam stability – in most of the analysed cases the equivalent seismic coefficients do not exceed the peak acceleration at the dam base.  相似文献   

Seismic performance sensitivity and uncertainty analysis of gravity dams          下载免费PDF全文

M. Alembagheri  M. Seyedkazemi 《地震工程与结构动力学》2015,44(1):41-58

Uncertainties in structural engineering are often arising from the modeling assumptions and errors, or from variability in input loadings. A practical approach for dealing with them is to perform sensitivity and uncertainty analysis in the framework of stochastic and probabilistic methods. These analyses can be statically and dynamically performed through nonlinear static pushover and IDA techniques, respectively. Of the existing structures, concrete gravity dams are infrastructures which may encounter many uncertainties. In this research, probabilistic analysis of the seismic performance of gravity dams is presented. The main characteristics of the nonlinear tensile behavior of mass concrete, along with the intensity of earthquake excitations are considered as random variables in the probabilistic analysis. Using the tallest non‐overflow monolith of the Pine Flat gravity dam as a case study, its response under static and dynamic situations is reliably examined utilizing different combinations of parameters in the material and the seismic loading. The sensitivity analysis reveals the relative importance of each parameter independently. It will be shown that the undamaged modulus of elasticity and tensile strength of mass concrete have more significant roles on the seismic resistance of the dam than the ultimate inelastic tensile strain. In order to propagate the parametric uncertainty to the actual seismic performance of the dam, probabilistic simulation methods such as Monte Carlo simulation with Latin hypercube sampling, and approximate moment estimation techniques will be used. The final results illustrate the possibility of using a mean‐parameter dam model to estimate the mean seismic performance of the dam. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

南京江宁区某退役小型硫铁矿尾矿库的治理方法     

邢姝  陈征宙  邹春江  韩非  缪世贤 《地质灾害与环境保护》2009,20(4):62-66

针对江宁区某退役小型硫铁矿出现的不良地质现象,对该尾矿坝进行了抗滑以及抗渗稳定性计算和分析,指出坝体处于不稳定状态,并提出具体治理方法。治理的方案包括降低坝体高度减载,在坡脚处反压坝体增加坝体稳定性,设置排渗设施降低浸润线高度,修筑排水沟阻止地表水停留在库区表面。最后需验证治理后尾矿坝在地震作用下的稳定性,运用时程分析法对设计后的坝体进行了动力有限元的分析,结果表明坝体内部和整体处于较稳定的状态。  相似文献   

Dynamic properties and liquefaction resistance of two soil materials in an earthfill dam—Laboratory test results     

V.C. Xenaki  G.A. Athanasopoulos 《Soil Dynamics and Earthquake Engineering》2008,28(8):605-620

Results are presented of laboratory resonant column and cyclic triaxial tests on specimens of two compacted soils (a sandy–silty clay and a sand–gravel mixture), planned to be used in the core and the shells, respectively, of a proposed earthfill dam. The values of low-amplitude shear modulus of the clayey material were found to increase with increasing confining pressure and decreasing water content, with deviations of ±20% from the predictions of the “Hardin equation”. On the other hand, the low-amplitude damping ratio was found to be at least four times higher than the values corresponding to natural undisturbed cohesive soils. The proposed G/G₀−γ_c curve for the compacted cohesive soil was found to be independent of confining pressure and small variations of the water content on either side of the optimum value and showed a remarkable agreement with recently published similar curves for natural cohesive soils. For the case of the sand–gravel mixture, normalized G/G₀–γ_c and D–γ_c curves are proposed, based on recently published results for gravelly soils and the limited data of the present study. The liquefaction resistance of the saturated sand–gravel mixture was found to be strongly dependent on its relative density, especially for high values of cyclic stress ratio. A relative density of at least 55% was found to be necessary to assure safety against earthquake-induced liquefaction of the material. The results presented herein may be used (directly or as guide) in the seismic analysis of (new or existing) earth dams constructed from similar soil materials and in addition they provide insight into the dynamic behavior of compacted soils.  相似文献   

Parametric study using FEM for the stability of the RCC Tannur dam     

Samer?A.?BarakatEmail author  Abdallah?I.?Husein?Malkawi  Maher?Omar 《Geotechnical and Geological Engineering》2005,23(1):61-78

Parametric study was carried out in this paper using the Finite Element Method (FEM) to study the effects of variations of the two parameters, i.e., variations in batter slope and foundation properties under static and dynamic loading conditions on the distribution of the peak stresses within the dam and foundation soils. The response spectra for the operating basis earthquake (OBE) and the maximum credible earthquake (MCE) were used in the dynamic analysis. It is shown that the distribution of peak stresses across base of dam and the extent of tensile zone on the foundation soils at the foundation level vary with the variations in the batter slope. Generally, as the batter slope increases the extent of the tensile zone at the foundation level decreases but not necessarily the maximum tensile stresses. However, an optimum batter slope could be achieved based on the results of this parametric study. It should be noted that the greatest tension is developed in the rock adjacent to the toe of the batter. For the foundation mechanical properties, it has been shown that the assessment of accurate soil mechanical properties has a great effect on the computed design stresses from finite element analysis. However, the greatest effect of the foundation properties was on the stresses at the base of dam while it has a negligible effect within the dam body.  相似文献   

深厚覆盖层300m级超高土质心墙坝应力变形特征   总被引：2，自引：0，他引：2  

徐晗  汪明元  程展林  饶锡保 《岩土力学》2008,29(Z1):64-68

目前我国高土心墙堆石坝的设计思想是在总结小浪底这类筑坝经验的基础上建立的,只有200 m级以下的资料可供参考,为此采用数值分析方法对居于心墙坝世界前列的深厚覆盖层300 m级高土心墙堆石坝进行进一步研究,探讨了心墙堆石坝填筑与蓄水的全过程,并分析了坝体、心墙的应力与变形特征.计算结果表明,300 m级高土质心墙堆石坝变形、应力均在可接受的范围内,理论上是可行的.  相似文献   

Strategies of Successful Anti-Dam Movements: Evidence from Myanmar and Thailand     

Julian Kirchherr 《社会与自然资源》2018,31(2):166-182

Scholars are rarely able to examine anti-dam movements that result in project suspensions or cancellations since these cases are rare empirically. Yet, they are central to understanding how anti-dam movements can succeed. This paper analyzes the movements against Myanmar’s Myitsone Dam and Thailand’s Kaeng Suea Ten Dam. Likely the most successful anti-dam movements in Southeast Asia in recent years, they achieved suspension over 6 and 37 years, respectively. The research is based on 60 semistructured interviews carried out over a period of 8 months. Leveraging thinking from both the constructionist and structural schools within the field of social movement studies, it is found that the framing of the Myitsone Dam as a project threatening the national cultural heritage of Myanmar (in combination with political change in the country in 2010/2011) largely explains the movement’s success. Meanwhile, the set of sophisticated tactics (including inter alia demonstrations, Thai Baan research, 24/7 monitoring of the dam site, and spiritual activities) was decisive for the efficacy of the movement against Thailand’s Kaeng Suea Ten Dam.  相似文献