汶川地震震损水库土坝动力反应与几何坝形的经验关系

在5·12汶川地震后的四川省水库土坝震害调查成果的基础上,选取汶川地震中受损的有完整资料的96座水库土坝为研究对象,应用等效线性模型对土坝进行了二维动力反应分析。选择3条有代表性的汶川地震实测记录,以三水准峰值加速度输入,得到土坝的动力反应（放大系数、最大动剪应力）与土坝几何形状（宽高比、上游坡比、坝高）间的经验关系。结果表明,土坝放大系数和最大动剪应力随着宽高比和上游坡比的增大而减小,随着坝高的增大而增大;输入波的频谱和峰值强度均对土坝动力反应与其几何形状的经验关系有重要影响。     

地震作用下均质土坡动力特性的振动台试验研究

设计并完成比例尺1∶100的边坡振动台模型试验,讨论模型的相似关系、传感器的布置及模型的建造,并编制相应的动荷载加载方案。通过输入不同类型、不同幅值、频率的动荷载,分析模型边坡在地震作用下的动力响应规律以及地震动参数对边坡动力特性和动力响应的影响。试验结果表明,在坡体的表面和坡内的竖直方向上,加速度放大系数均随着高程增加而明显增大。当输入不同压缩比的地震波时,压缩比越大坡体的动力响应越明显,即随着输入动荷载的频率增加,越接近土体的自振频率加速度放大效应越明显;在坡体的同一高程处,坡面的加速度放大系数略大于坡体内的加速度放大系数,表现出一定的趋表效应,同时随着输入地震波振幅的增加,加速度放大系数整体出现递减的趋势。实验结果分析有助于揭示土质边坡在地震作用下的失稳破坏机制,为今后边坡工程的抗震设计提供积极的参考。     

罗江县水库土坝汶川大地震震害调查与分析

5·12汶川8.0级大地震对德阳市罗江县的水库造成了不同程度的破坏,经济损失严重,若水库出现渍坝现象,将会带来更大的损失。对罗江县19座高危以上险情水库的土坝震害进行了调查研究.发现典型的震害现象包括裂缝、渗漏、防浪墙损坏以及泄水建筑物和附属设施的损毁等。根据水库土坝的震前病害调查资料可以看出：水库土坝在地震前多是带病运行,严重影响地震时水库运行的因素主要有土料或填筑质量差、坝基问题、坝体结构设计不当、蚁害、观测设施不全等。依据震后水库土坝的破坏形态,分析了水库大坝的震前病害对大坝震害现象的影响。为今后水库土坝的抗震设计提供基础性的资料。     

高聚物防渗墙土质堤坝地震加速度响应的动力离心试验研究

为研究高聚物防渗墙土质堤坝地震加速度反应规律,采用El Centro波,在0.05 g、0.1 g、0.2 g和0.4 g工况下进行了高聚物防渗墙土质堤坝和传统刚性防渗墙—混凝土防渗墙土质堤坝的离心机振动台的对比试验。试验采用非等应力离心模型,利用加速度传感器测量了坝体不同位置的加速度时程响应。结果表明:高聚物防渗墙土质堤坝峰值加速度随输入地震动增加而增加,随坝高增加而增加,最大峰值加速度在坝顶上;高聚物防渗墙土质堤坝最大峰值加速度随输入地震动的增大呈线性增加趋势,而最大峰值加速度放大系数随输入地震动增大而减小;从模型试验的角度来看,在同等水平地震作用下,混凝土防渗墙土质堤坝抗地震加速度反应能力好于高聚物防渗墙土质堤坝,但在强震下混凝土防渗墙体发生了破坏,这一点可由附近土体加速度突增判断。     

岳城水库土坝抗震加固有效应力动力分析

岳城水库土坝采用了上游压坡铺盖加固的方法,以防止坝体动力和静力坍滑。本文对该坝的有压坡铺盖断面和无压坡铺盖断面进行了大量的非线性静力计算和动力计算。静力计算采用应力和渗流一并考虑的计算方法,并考虑水位骤降的影响。动力计算采用非线性的二维有效应力方法。计算中都用等参数单元。文中分析比较了两个断面的静应力、流网、静力稳定安全系数、加速度反应曲线、剪应力反应曲线,最大动剪应力和动剪应变,振动孔隙水压力的分布、振动残余变形、残余位移、动力稳定系数等等。 分析指出,压坡铺盖加周措施对该坝是有效果的。     

基于液化流动模型的尾矿坝地震响应分析

针对传统等效线性法对尾矿坝地震响应分析结果与实际情况存在一定的出入的问题,通过振动台模型试验和数值计算结果比对验证数值计算方法的可行性,运用考虑液化后尾矿砂流动特性的孔压上升模型,基于完全非线性动力分析方法,对尾矿坝地震响应进行分析计算,通过对坝顶位移和加速度的监测结果进行分析,得出坝顶的加速度放大系数以及坝顶位移最大值;并由坝体水平方向位移云图、竖直方向位移云图及位移矢量图,判断可能发生局部滑坡的位置;对坝体内液化情况进行判定,得到尾矿坝的地震响应规律,为尾矿坝抗震设计提供一定的理论参考.     

特殊地形条件下面板堆石坝的动力反应特性及抗震能力研究

受地形地质条件所限,抽水蓄能电站上水库的面板堆石坝工程通常不得不修筑在山腰、山坡等地形条件复杂的区域,特殊地形条件对面板堆石坝抗震安全性能的影响如何是值得关心的问题。采用基于ABAQUS的UMAT子程序二次开发的等价黏弹性模型,研究了此类特殊地形条件下面板堆石坝的动力反应特性,提出应该从防渗系统的安全性、坝坡动力稳定性以及地震最大残余变形三个方面综合评价大坝的极限抗震能力,研究了此类特殊地形条件下面板堆石坝的地震破坏模式。研究结果表明:大坝在地震荷载作用下的动加速度,动位移,动应力等动反应值均较小,坝体竖向最大残余变形值小于坝高的1%,大坝具有较强的抗震能力;大坝沿顺河方向的最大动位移出现在坝高3/4靠近下游侧的坝坡处,倾斜的坝基地形会影响大坝的动力反应特性;倾斜坝基地形条件下大坝的破坏模式以防渗系统破坏和下游坝坡失稳为主,其极限抗震能力为0.50 g~0.58 g。     

110kV及以上变电站地震易损性研究

本文提出了根据变电站内高压电气设备和房屋建筑的地震破坏状态计算变电站震害指数的方法,统计了2008年汶川8.0级大地震中成都、绵阳、德阳、广元、阿坝地区国家电网的121座110kV及以上变电站的震害情况,通过震害指数进行了震害等级评价。采用对数正态分布的累积函数,拟合了变电站基于峰值加速度的地震易损性曲线。计算结果表明:当地震烈度在Ⅶ度及以下时,变电站和输电线路只有基本完好和轻微破坏状态,不发生中等及以上等级的破坏;当地震烈度为Ⅷ度时,有变电站开始出现严重破坏状态;当烈度达到Ⅸ度时,有少量变电站发生严重破坏,多数为中等破坏;当烈度为X度及以上时,多数变电站达到严重破坏和毁坏。     

汶川大地震中德阳市水库土坝的震害特征

汶川特大地震给四川省德阳市水库土坝造成了不同程度的震损。依据德阳市境内66座高危以上险情水库土坝震害考察资料和现场震害调查结果,对震损水库土坝进行了分类统计,研究其震害特征及震损原因,结果表明：小型水库均质土坝在此次地震中震损数量最多、险情严重,且震害类型丰富;典型震害包括裂缝、滑坡、沉陷、渗漏以及泄水建筑物与其它附属设施损坏。以德阳市3座典型震损水库土坝为例,分析了水库土坝的基本情况、震前运行状况及震损情况,进而提出了有效的震后抢险措施。     

汶川地震中绵阳市梓潼县水库土坝震害调查与分析

5·12汶川特大地震对绵阳市梓潼县170座水库造成了不同程度的破坏和严重的经济损失.依据绵阳市梓潼县水库地震灾害的现场科学考察资料,对绵阳市梓潼县48座高危以上险情水库土坝的震损情况做了初步总结和分析.典型震害现象包括裂缝、渗漏以及泄水建筑物和附属设施的损毁等;以梓潼县3座典型震损水库土坝为例,总结了震损水库的特点和经验教训,给出了一些建设性结论.     

Seismic behaviors of earth-core and concrete-faced rock-fill dams by dynamic centrifuge tests

The investigation on the seismic behavior of dams becomes crucial but is limited to lack of experimental or field data. This paper aims to experimentally simulate two major dam types of earth-core rock-fill dam and concrete-faced rock-fill dam by dynamic centrifuge tests to investigate the seismic response of the dam. A series of staged centrifuge tests was performed by applying real earthquake records from 0.05 to 0.5g. The distributions of amplification ratio differed depending on the magnitude of earthquake loading and the zoning condition. The amplification ratio at the crest increased in the bedrock acceleration that exceeds 0.3g and strongly influenced by the loosening behavior of the upper part. The residual settlements and horizontal displacement at the dam crest were small. Shallow surface sliding was dominant failure. The maximum tensile stress on the face slab by dynamic loading occurred at a height of around 4/5 near the upstream water level. Finally, two-dimensional numerical simulations were performed in an effort to simulate the centrifuge models. The centrifuge tests and numerical analysis obtained mostly comparable results, thus confirming that centrifuge modeling reasonably simulates the seismic behavior of dams.     

Analysis on residual strain of Zipingpu Concrete Faced Rockfill Dam after Wenchuan earthquake

The Zipingpu Concrete Faced Rockfill Dam (CFRD) was subjected to significant local damage in the “5.12” Wenchuan earthquake. It is the first rockfill dam of more than one hundred meters high to encounter a strong earthquake anywhere in the world. Based on the finite element smoothing method, the residual strains at a typical cross-section and a downstream slope of the dam were obtained by processing the dam monitored displacement data. The position of and reason for the dam settlement and deformation of rockfill dilatancy in the earthquake were analyzed according to the section residual strain. The results show that the maximum settlement ratio on the dam body approximately occurs at 2/3 of the dam height; dilatancy occurs from the dam crest to 25–30 m in the upstream and downstream slope; the immediate cause of the face slabs horizontal construction joint dislocation is excessive residual shear strain. Meanwhile, the position of and reason for the dam fissure in the earthquake were analyzed according to the dam slope residual strain.     

Numerical investigation of the response of the Yele rockfill dam during the 2008 Wenchuan earthquake

In this paper the seismic response of a well-documented Chinese rockfill dam, Yele dam, is simulated and investigated employing the dynamic hydro-mechanically (HM) coupled finite element (FE) method. The objective of the study is to firstly validate the numerical model for static and dynamic analyses of rockfill dams against the unique monitoring data on the Yele dam recorded before and during the Wenchuan earthquake. The initial stress state of the dynamic analysis is reproduced by simulating the geological history of the dam foundation, the dam construction and the reservoir impounding. Subsequently, the predicted seismic response of the Yele dam is analysed, in terms of the deformed shape, crest settlements and acceleration distribution pattern, in order to understand its seismic behaviour, assess its seismic safety and provide indication for the application of any potential reinforcement measures. The results show that the predicted seismic deformation of the Yele dam is in agreement with field observations that suggested that the dam operated safely during the Wenchuan earthquake. Finally, parametric studies are conducted to explore the impact of two factors on the seismic response of rockfill dams, i.e. the permeability of materials comprising the dam body and the vertical ground motion.     

汶川8.0级地震水坝震害调查

“5．12”汶川地震中水坝损毁严重,造成了巨大的经济损失。震后对69座溃坝险情和310座高危险情水库水坝进行了系统的调查,典型震害现象包括坝体裂缝、塌陷、滑坡、渗漏、启闭设施损坏和其他附属设施的损毁等。文中给出了不同烈度区的水坝震害分布,并对地震中水坝的震害现象做了初步总结和分析。     

卵石土场地地震反应特征振动台试验研究

为研究卵石土场地地震反应特征,基于四川成都典型卵石土场地,通过振动台模型试验研究卵石土场地在不同地震波、不同地震强度激励下的加速度峰值放大系数、加速度频谱反应及动土压力反应,并且对其场地地震反应非线性效应及土体动剪应力-动剪应变关系进行分析。结果表明：卵石土场地表层土层对地震波具有明显的放大效应,加速度峰值放大系数介于1～1.4之间,下部土层放大效应较小,加速度峰值放大系数介于0.9～1.2之间。卵石土场地对地震波具有低频放大,高频滤波的作用,滤波频率上、下限随激励强度的增大逐渐向低频方向移动。激励强度较小时,土体尚未破坏,动土压力在地震过程中逐渐增大;随着激励强度的增大,动土压力反应明显增大,表现出骤减后逐渐增大的现象。在激励强度较小时(SN1),中部土体最先进入非线性反应阶段,地震波在中部土层能量损耗最大;激励强度较大时(EL3),土体均发生了较大变形,土体最大动剪应变达到1.7%,此时卵石土场地对地震波的放大作用明显减弱。     

An investigation into the seismic behaviour of dams using dynamic centrifuge modelling

Dynamic response of dams is significantly influenced by foundation stiffness and dam-foundation interaction. This in turn, significantly effects the generation of hydrodynamic pressures on upstream face of a concrete dam due to inertia of reservoir water. This paper aims at investigating the dynamic response of dams on soil foundation using dynamic centrifuge modelling technique. From a series of centrifuge tests performed on model dams with varying stiffness and foundation conditions, significant co-relation was observed between the dynamic response of dams and the hydrodynamic pressures developed on their upstream faces. The vertical bearing pressures exerted by the concrete dam during shaking were measured using miniature earth pressure cells. These reveal the dynamic changes of earth pressures and changes in rocking behaviour of the concrete dam as the earthquake loading progresses. Pore water pressures were measured below the dam and in the free-field below the reservoir. Analysis of this data provides insights into the cyclic shear stresses and strains generated below concrete dams during earthquakes. In addition, the sliding and rocking movement of the dam and its settlement into the soil below are discussed.     

黄土斜坡动力响应特征分析

斜坡动力响应特征与斜坡形态密切相关,若入射地震波主频接近斜坡卓越频率就会放大斜坡动力响应,甚至造成斜坡失稳。汶川地震对远离震中的黄土地区造成了较为严重的破坏,局部场地震害和地震动放大效应显著。选取汶川地震典型黄土斜坡场地,利用地形台阵流动观测和数值模拟计算相结合的方法,系统开展强震动作用下黄土斜坡场地动力响应特征研究。结果表明:坡顶卓越频率最小,其PGA放大系数甚至达到坡底的1.98,这种现象可能与斜坡高差和入射波波长之比密切相关,比值0.2时坡顶放大效应达到最大。随斜坡坡度增加,放大效应增强,坡顶反应谱卓越周期放大系数可达5,说明斜坡地形对强震地面运动有显著影响。数值计算结果与实际强震观测基本吻合,其结果对黄土地区建设工程抗震设防具有重要的科学与实际意义。     

Estimation of shear wave velocity of earth dam materials using artificial blasting test

The objective of this study is to estimate the shear wave velocity of earth dam materials using the vibration generated from artificial blasting events, and to verify its applicability. In this study, near-field artificial blast testing and monitoring were carried out at the Seongdeok dam, Korea, as the first blasting tests to be carried out on an existing dam in Korea. Vibrations were induced by four different types of blasting, using various explosive charge weights and depths of blasting bore-holes. During the tests, acceleration time histories were measured at the rock outcrop adjacent to the point of the explosion, and at the crest of the dam. The fundamental frequency of the target dam was computed from the frequency analysis of measured acceleration histories. Numerical analyses were carried out, varying the shear modulus of the earth fill zone and using the acceleration histories measured at the rock outcrop as input ground motions. From a comparison between the fundamental frequencies calculated by numerical analyses and those of measured records, the shear wave velocities with depth, which are closely related to shear moduli, could be estimated. It is found that the effect of different blasting types on shear wave velocity estimation for the target dam materials is negligible, and that shear wave velocity can be consistently evaluated. Furthermore, by comparing the evaluated shear wave velocity with empirical formulae from previous research, the applicability of the method was verified. Therefore, in cases of mid-to-small earth dams, where the earthquake record is not available, the shear wave velocity of earth fill materials can be reasonably evaluated using blasting vibration records obtained at the site adjacent to the dam.