共查询到18条相似文献，搜索用时 109 毫秒
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土石坝振动台模型试验颗粒流数值模拟分析 总被引：2，自引：0，他引：2
目前一般采用振动台试验、离心振动台试验和有限元动力分析来获得土石坝在设计地震荷载作用下的形态和抗震性能。本文结合孔宪京等的土石坝振动台试验结果开展了颗粒流细观数值模拟研究,克服了传统连续介质力学的宏观连续性假设,形象而直观地表现出坝体在动力荷载作用下的破坏特征。数值模拟规律与振动台试验规律基本一致。同时还分析了坝体颗粒粘结强度和地震峰值加速度变化对坝体破坏特征的影响。数值结果表明,当颗粒间粘结强度较低时,表现为坝体表面颗粒的滑动破坏,粘结强度稍大时,会出现局部的小块颗粒团整体滑动破坏;随着峰值加速度的增大,坝顶沉降量在增大,坝体破坏特征不变。 相似文献
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爆炸荷载下土石坝动力响应特征的数值模拟 总被引：3，自引：0，他引：3
土石坝在爆炸荷载下的力学响应是一个非常复杂的力学问题,相关研究甚少。在LS-DYNA软件框架内,以两河口土石坝为研究对象,把坝体材料简化为混凝土、心墙、反滤层与堆石体等4种,用500 kg TNT在坝顶接触爆炸时的瞬态荷载作为荷载源,针对不同材料建立适合于爆炸高加载率特征的本构模型,用数值方法分析了土石坝在潜在爆炸荷载下的破坏与损伤演化规律。结果表明,在爆炸荷载作用下,由于土石坝材料组成的多样性,应力波传播规律异常复杂,土石坝的力学响应呈现出显著的分区特征。 相似文献
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对土石坝振动台模型试验理论和技术进行系统阐述,提出基于原型和模型坝料静、动力特性试验的模型相似设计方法和不同强度地震动递进输入(白噪声微振-设计地震-校核地震-破坏试验)的振动试验方法。基于1g大型振动台和ng超重力离心机振动台设备性能现状,结合高土石坝的结构特点和动力试验相似模拟要求,对土石坝振动台模型试验的优势及局限进行深入讨论。结合已有的工程实践,对土石坝振动台模型试验在工程中的应用进行总结,并以某实际高面板堆石坝为例研究面板坝生命周期内经历多次地震情况下结构动力特性的演化规律。 相似文献
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本文探讨了筑坝堆石料的空间变异性对土石坝坝坡动力稳定性的影响。以新疆某在建高面板堆石坝为例,在蒙特卡洛法的框架下,采用基于局部平均细分法的随机有限元法模拟考虑筑坝堆石料空间变异性时土石坝的地震响应及坝坡滑移情况,通过对比随机有限元法和常规确定性有限元法的计算结果,提出:在地震动作用下,考虑筑坝材料空间变异性时,坝坡滑动体的数量、规模以及滑移量和滑动历时都有不同程度的增大,因而坝坡整体危险程度显著高于不考虑材料空间变异性的情况。坝坡各项动力安全性指标对筑坝材料空间变异性非常敏感;因而,考虑筑坝材料空间变异性时,各项安全性指标的离散性较大。 相似文献
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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. 相似文献
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调查、搜集和研究了汶川地震中被评定为高危以上险情的147座小型水库土坝的地震破坏情况,给出了高危以上险情土坝的地震破坏程度划分为中等破坏、严重破坏和极严重破坏三个等级的原则和标准,以及土坝的地震破坏程度与地震烈度、土坝的宽高比、上游坡比、坝高的经验关系表,可发现:土坝的几何形状对其破坏程度起着重要的作用;对于6～8度地震烈度区,土坝的宽高比越小,或上游坡比越小,或坝体越高,则土坝的破坏程度越严重;对于9度以上地震烈度区,土坝通常发生极严重破坏。依据高危以上险情土坝的地震反应分析结果,给出了土坝地震破坏程度与土坝宽高比、坝高、土坝上游坡比及坝顶加速度放大系数、坝体最大动剪应力的经验关系曲线,发现在相同的地震烈度水平下,土坝的宽高比越小,或上游坡比越小,或坝高越大,且坝顶加速度放大系数越大或坝体最大动剪应力越大,则其地震破坏程度越严重;坝体最大动剪应力超过30kPa的土坝,通常发生严重或极严重破坏,坝体最大动剪应力大于100kPa的土坝,通常发生极严重破坏;土坝离发震断层越远,则其坝顶加速度放大系数越大。本文给出的高危以上险情土坝的地震破坏程度与坝体几何形状的经验关系,可为今后土坝抗震设计提供参考依据。 相似文献
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现行碾压土石坝设计规范（DL/T5395-2007）明确规定只适用于低于200 m土石坝,随着设计施工技术的发展对于超过200 m的高土石坝坝坡设计安全标准问题亟待解决。相对安全率理论把可靠指标和安全系数置于同一平台进行关联和映射。现行碾压土石坝设计规范规定的低于200 m的土石坝坝坡稳定允许可靠指标4.2。基于风险控制原则提出200~250 m高土石坝坝坡允许可靠指标取4.45,250~300 m高土石坝坝坡允许可靠指标取4.7,相应的地震工况高土石坝坝坡稳定安全系数1.35和1.4,高土石坝工程实例地震工况下坝坡稳定安全系数均满足所提安全系数标准值。 相似文献
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现行碾压土石坝设计规范（DL/T5395-2007）明确规定只适用于低于200 m土石坝,随着设计施工技术的发展对于超过200 m的高土石坝坝坡设计安全标准问题亟待解决。相对安全率理论把可靠指标和安全系数置于同一平台进行关联和映射。现行碾压土石坝设计规范规定的低于200 m的土石坝坝坡稳定允许可靠指标4.2。基于风险控制原则提出200~250 m高土石坝坝坡允许可靠指标取4.45,250~300 m高土石坝坝坡允许可靠指标取4.7,相应的地震工况高土石坝坝坡稳定安全系数1.35和1.4,高土石坝工程实例地震工况下坝坡稳定安全系数均满足所提安全系数标准值。 相似文献
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Two of China's highest earth-core rock-fill dams (ECRDs) and concrete-faced rock-fill dams (CFRDs) were simulated by large-scale earthquake simulation shaking table tests in this work. A series of staged tests were performed, including white noise, different types of earthquake excitations with different magnitudes etc. The seismic performance of the ECRD and CFRD models were analyzed and investigated. The test results indicated that reservoir impoundment influenced the structure and seismic characteristics of the ECRD model much more than the CFRD model. The average fundamental frequency of the CFRD decreased less than the ECRD model when subjected to strong excitation. The acceleration amplification factors decreased as the input peak acceleration increased. The maximum acceleration occurred at the top of the ECRD model, while it occurred at 0.6–0.9 dam height of the CFRD model. Seismic residual deformations of the two models were very small. When subjected to strong earthquake excitation, the residual deformation of the CFRD model was smaller than that of the ECRD model. The dominant failure pattern of the two models was shallow sliding at the height of 3/4 on the downstream slope. The above analysis indicated that seismic performance of CFRD was superior to ECRD. 相似文献
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An experimental study of non-linear mechanisms that may occur during intense seismic response of arch dams is described in this paper. The presentation deals with three types of non-linearity that were observed during shaking table model studies: monolith joint opening, cantilever cracking, and reservoir cavitation at the dam face. The monolith joint opening phenomenon was represented by a segmental arch ring model that simulated a horizontal slice of a prototype dam. The cantilever cracking and reservoir cavitation mechanisms were studied using a model gravity dam section. The principal conclusion of the investigation was that shaking table experiments provide a practical means of studying the non-linear earthquake response of concrete arch dams, including their actual failure mechanisms. 相似文献
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下蜀土边坡地震稳定性的大型振动台试验研究（Ⅱ）——试验结果及分析 总被引：2，自引：0，他引：2
选用天然下蜀土,设计并完成了一几何相似常数为20、坡高为0.5 m、坡角为45°的模型边坡1 g大型振动台试验,通过对模型边坡动力特性、动力反应及宏观变形等三方面的研究,揭示了下蜀土边坡的地震反应机理。试验结果表明,下蜀土边坡有着稳定的一、二阶自振频率和阻尼比,随着地震动加载幅值（PGA）逐渐增大,其一阶自振频率逐渐减小,一阶阻尼比逐渐增大;坡高范围内,PGA放大系数均大于1,且自下而上逐渐增大,并在坡肩处达到最大,其在坡脚处的值小于水平方向其他位置处的值,输入El Centro波（经时间相似常数4.47压缩）时的值分别大于输入El Centro原波和Kobe波（经时间相似常数4.47压缩）时的值;随着输入PGA的增大,土体非线性特征逐渐增强,边坡也逐渐趋于失稳破坏状态;震后模型边坡坡脚、坡顶等部位出现了不同程度的裂缝,说明边坡中出现了通过坡脚的（潜在）滑动面。 相似文献
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Study on the failure process of high concrete dams subjected to strong earthquakes is crucial to reasonable evaluation of their seismic safety. Numerical simulation in this aspect involves dynamic failure analysis of big bulk concrete dam subjected to cyclic loading. The Rock Failure Process Analysis (RFPA) proposed by C.A. Tang, with successful applications to failure modeling of rock and concrete specimens mainly subjected to static loading, is extended for this purpose. For using the proposed model, no knowledge on the cracking route needs to be known beforehand, and no remeshing is required. Simulation of the whole process of elastic deformation, initiation and propagation of microcracks, severe damage and ultimate failure of concrete dams in earthquakes with a unified model is enabled. The model is verified through a shaking table test of an arch dam. Finally a practical gravity dam is employed as a numerical example. Considering the uncertainty in ground motion input and concrete material, typical failure process and failure modes of gravity dam are presented. Several small cracks may occur due to tension particularly at dam neck, dam faces and dam heel, and a few of them evolve into dominant ones. Relatively smaller earthquake may cause damage to the dam neck while a bigger one may bring on cracks at lower parts of the dams. Cracking at the dam bottom may incline to a direction almost perpendicular to the downstream face after propagating horizontally for a certain distance when the shaking is strong enough. 相似文献
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《Soil Dynamics and Earthquake Engineering》2012,32(12):1678-1689
Study on the failure process of high concrete dams subjected to strong earthquakes is crucial to reasonable evaluation of their seismic safety. Numerical simulation in this aspect involves dynamic failure analysis of big bulk concrete dam subjected to cyclic loading. The Rock Failure Process Analysis (RFPA) proposed by C.A. Tang, with successful applications to failure modeling of rock and concrete specimens mainly subjected to static loading, is extended for this purpose. For using the proposed model, no knowledge on the cracking route needs to be known beforehand, and no remeshing is required. Simulation of the whole process of elastic deformation, initiation and propagation of microcracks, severe damage and ultimate failure of concrete dams in earthquakes with a unified model is enabled. The model is verified through a shaking table test of an arch dam. Finally a practical gravity dam is employed as a numerical example. Considering the uncertainty in ground motion input and concrete material, typical failure process and failure modes of gravity dam are presented. Several small cracks may occur due to tension particularly at dam neck, dam faces and dam heel, and a few of them evolve into dominant ones. Relatively smaller earthquake may cause damage to the dam neck while a bigger one may bring on cracks at lower parts of the dams. Cracking at the dam bottom may incline to a direction almost perpendicular to the downstream face after propagating horizontally for a certain distance when the shaking is strong enough. 相似文献
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汶川8.0级地震水坝震害调查 总被引：11，自引：1，他引：10
“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。 相似文献
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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。 相似文献