Numerical simulation of damage in high arch dam due to earthquake

Based on the assumption that concrete is macroscopic homogeneous, the cracking evolution process and damage mode of high arch dams are studied in consideration of the heterogeneity of concrete in mesoscale. The bilinear damage evolution model and the damage evolution model expressed in power function with descending section are adopted to combine with the Mohr-Coulomb criterion to investigate the crack development and fracture mode of high arch dams under the action of an earthquake. The analysis result of a high arch dam in China under design shows that cracks that take place in concrete are caused by excessive tensile stress. The cracks initiate at the middle of the dam top and distribute at the upper half of the dam while the rest of the parts remain intact. This conclusion agrees with the model test result.     

高拱坝坝肩岩体变形稳定性的三维数值模拟

以金沙江上游拟建某水电站高拱坝坝肩为研究对象,应用有限差分程序FLAC-3D对坝肩岩体在天然和荷载后的应力、变形和破坏的发展特征模拟分析,重点分析了坝肩岩体在正常工程荷载下的变形稳定性及坝肩超载特性,得到了坝肩岩体的变形破坏特征及超载安全系数。     

石笼拱柔性拦截坝新技术及其数值模拟

针对常见的泥石流拦挡结构被冲击破坏的问题,提出了柔性石笼拱拦截坝新技术。柔性石笼拱以石笼为主要材料,砌筑成拱形,上游面铺设废旧轮胎防冲垫层,拦截泥石流。利用ANSYS LS-DYNA软件,分析了柔性石笼拱结构对泥石流冲击的动力响应,并与刚性浆砌石结构进行对比。通过MIDAS GTS软件计算,分析了石笼拱拦蓄泥石流后孔隙水压力变化及静力稳定特性。数值计算结果表明,柔性石笼拱结构能合理地优化结构受力,变形自适应,减小巨石冲击荷载以及饱和泥石流的浆体压力对结构的不利影响。     

基于微震监测的大岗山高拱坝坝踵蓄水初期变形机制研究

 混凝土高拱坝坝踵是蓄水初期阶段拱坝安全的重点关注部位。通过构建国内首套高拱坝坝踵微震监测系统,实现对蓄水初期阶段大岗山拱坝坝踵区微破裂的实时监测,探究坝踵蓄水初期变形机制及其与微震活动性的关系。采用人工敲击试验确定坝踵等效P波波速为4 300 m/s,系统定位误差小于8 m。对系统获取的事件波形进行噪声滤除,并在自动定位基础上进行人工二次校核,提高定位精度,验证了微震监测技术应用于大体积混凝土工程的可行性。分析认为：蓄水初期阶段,大岗山高拱坝坝踵区微震活动性与库水位密切相关,微震事件聚集区实现从坝踵向坝趾的转移,坝踵压缩变形减小,而坝趾区变形量增加。此外,通过拱坝坝踵区微震变形演化过程,揭示了导流洞下闸蓄水前940 m高程基础廊道拱顶裂缝产生的根本诱因。研究成果可为混凝土高拱坝微震监测和真实工作性态研究提供参考。     

浆砌石双曲拱坝施工技术

结合工程实例 ,介绍了浆砌石双曲拱坝的施工技术 ,阐述了其施工工艺和作业方法 ,指出双曲拱坝已成为近年来较普遍采用的一种坝型 ,值得推广应用     

砌石面板坝变形的数值模拟

针对砌石面板坝的特点,采用离散元法对某砌石面板的变形进行了模拟,计算结果表明砌石面板坝的变形与一般堆石面板坝的变形有很大的不同,砌石面板坝的计算表明,该坝基本上不存在倾覆破坏的可能,水平滑移和整体滑移都有较高的安全系数.     

高拱坝混凝土工程施工工艺及施工方法初探

结合施工经验,对高拱坝混凝土工程施工工艺及施工方法进行了探讨,阐述了模板施工工艺及注意事项,着重介绍了混凝土养护方法及温度控制措施,以期指导今后同类水利工程施工。     

Numerical simulation of tensile damage and blast crater in brittle rock due to underground explosion

The prediction of blast crater in brittle rock due to an underground explosion has gained importance in recent years due to the great number of accidental events that affected engineering safety. This paper uses the Taylor–Chen–Kuszmaul (TCK) continuum damage model to analyze dynamic fracture behavior of rock in tension due to blast loading. The TCK damage model, together with an erosion algorithm, was implemented into the explicit FE code, LS-DYNA, as a constitutive augmentation. The damage pattern around the blasthole and the formation of blast crater near a free surface were subsequently simulated using the developed numerical tool. It is shown that the free surface is vitally responsible for the blast crater. Furthermore, the size and shape of the blast craters can be reasonably predicted if the erosion criterion of critical tensile damage is well calibrated. The effects of common charge modes on blast craters were also investigated numerically, and the mechanisms of the coupled, air-decoupled and water-decoupled charge mode are compared and presented.     

水电站坝体廊道温降效应数值模拟

以水电站坝体廊道通风系统为研究对象,建立了非稳态数学模型。运用FLUENT软件对气流和岩体间的耦合传热进行了模拟分析,给出了气流和岩体的温度场分布;分析了坝体廊道对气流的冷却效果。将数值模拟结果与理论计算结果及实测数据进行了比较,三者基本一致。     

Determination of symmetric arch dam vibration periods using empirical formulae

Some simple formulae which allow us to estimate the first six vibration periods of a symmetric arch dam (designed by following the guidelines of the US Bureau of Reclamation) are presented. Polynomial type expressions are indicated for both empty and full reservoir situations. Dam-reservoir interaction is taken into account by means of a modified three-dimensional Westergaard technique. Likewise, a tentative formulation, which accounts for the foundation flexibility effects is given.     

拱坝坝肩开挖及地基处理措施研究

结合实际工程，对天花板拱坝的坝肩开挖及地基处理措施进行了研究，根据实际地质情况提出了坝基开挖、固结灌浆、接触灌浆、帷幕灌浆、基础排水、断层破碎带处理和岸坡锚固支护等措施，以使坝基满足稳定、应力、变形、抗渗和耐久性等各方面的要求。     

金溪水电站拱坝变形性态分析

针对金溪水电站拱坝垂线水平位移实测资料建立回归模型,深入分析了金溪水电站拱坝的变形性态及变化规律。结果表明：金溪拱坝的水平位移变化符合拱坝变形的一般规律,整体变形性态较好,坝体变形处于弹性变形,工作状态基本正常。     

高拱坝坝肩裂隙岩体的三维非线性抗震稳定性分析

在高拱坝坝肩裂隙岩体的抗震稳定性分析中 ,采用传统刚体极限平衡法分析坝肩裂隙岩体潜在滑体的安全性态 ,坝肩稳定性评价未考虑裂隙岩体变形对坝体应力的影响 ,由此计算的抗滑安全系数并不能保证坝体的安全性 ;而采用基于连续介质理论的有限元法和基于碎散介质的离散单元法分析时 ,其物理数学模型和坝肩岩体的实际情况相距甚远。为此 ,本文在安全系数强度储备概念基础上提出了动抗滑变形安全系数法 ,该方法以坝体拉应力作为坝肩岩体抗滑稳定性评价标准 ,综合考虑非线性坝体和坝基节理、裂隙岩体的动静态耦合作用 ,坝肩岩体的抗滑安全系数保证了坝体的安全 ,较传统的分析方法更为科学、合理。采用该方法 ,本文将坝肩裂隙岩体作为可以考虑局部开裂、各向异性和大变形的非线性连续体用动态接触单元模型模拟 ,对在建的小湾高拱坝坝肩裂隙岩体的抗震稳定性进行了三维动力分析。数值分析结果表明 ,在综合考虑坝体应力影响后 ,坝肩裂隙岩体的变形安全系数小于强度安全系数。因此 ,在高拱坝坝肩岩体的抗震稳定性评价中必须计及坝体应力的影响因素。     

基于混凝土不均匀性面板堆石坝面板损伤分析

将混凝土面板堆石坝中面板混凝土视为宏观上均质、细观上不均匀的材料,结合统计学原理,考虑材料参数分布的随机性,通过二维有限元数值分析,研究了混凝土的弹性模量和抗拉强度随机性对面板堆石坝面板动力损伤分布规律的影响。计算结果表明:不考虑面板混凝土材料参数随机性时,(0.65~0.85)H(H为坝高)处面板顺坡向应力较大,拉损伤主要发生在0.8H(H为坝高)附近的面板处;随着混凝土材料不均匀性增大,发生拉损伤的部位趋于分散,但主要集中在(0.4~0.9)H范围内的面板。因此这部分面板应该是抗震设计的重点区域。采用混凝土弹脆性细观损伤模型,考虑材料参数的随机性,能够直观地阐明混凝土面板的地震破坏过程和损伤分布,便于了解面板薄弱环节,研究成果可以为混凝土面板堆石坝抗震设计提供参考。     

地质力学模型试验在某拱坝稳定分析中的应用

采用三维地质力学模型试验技术,研究某双曲拱坝坝基内的软弱夹层和裂隙对坝体整体稳定性的影响,以及在超载情况下的坝体的破坏形式和破坏发展过程,从而对大坝的安全性作出了科学评价。     

小湾水电站混凝土拱坝温度裂缝分析

针对小湾水电站双曲混凝土拱坝实际条件,参照相关的控制拱坝裂缝理论与实践,论述分析了在施工过程控制温度应力,从而控制拱坝裂缝的目标和具体方法,为混凝土拱坝施工过程提供指导。     

Seismic performance evaluation of a jointed arch dam

Seismic performance and safety of a jointed arch dam, as an arch-shaped mass concrete structure, are investigated through the nonlinear incremental dynamic analysis. In this way, 12 proper ground motions are selected, each of them is scaled to 12 successively increasing intensity levels and applied to the dam. Three and seven contraction joints are inserted within the dam body, and stage construction is taken into account. Several main assumptions including dam–reservoir–foundation dynamic interaction, absorbing boundary conditions at the far-ends of the reservoir and foundation, and material and joint nonlinearities are considered. The failure modes of the dam are determined according to the distribution of damaged zones through the dam body. The results of the static analysis under dam self-weight and hydrostatic load show that the inclusion of the contraction joints and the stage construction do not considerably alter the tensile principal stresses; however, they increase the compressive stresses. In seismic analysis, increasing the number of the contraction joints generally reduces the joints opening and sliding displacements. The contraction joints can significantly decrease the damage imposed to the dam body. Finally, it is concluded that inserting the contraction joints can increase the seismic safety of the arch dam.     

Modelling autogenous expansion for magnesia concrete in arch dams

Magnesia Concrete is a kind of expansive concrete used in Chinese hydraulic engineering more and more widely. To evaluate the effects of autogenous expansion on the stresses of arch dams, a simple model of autogenous expansion for Magnesia Concrete in dam engineering is presented. This model is based on three assumptions: 1) the total amount of autogenous expansion of Magnesia Concrete is related only to the properties of materials and mixing of concrete; 2) the autogenous expansion of Magnesia Concrete is irreversible due to the irreversibility of hydration reaction of Magnesia in the concrete; 3) the autogenous expansion strain rates of Magnesia Concrete bear a relation between temperature and residual Magnesia per unit volume of concrete. The model is verified by some experimental data of autogenous expansion of Magnesia Concrete and field-measured data of an arch dam in China. Embedded into finite element arch dam simulation software, this model is employed to simulate the effects of autogenous expansion of Magnesia Concrete in hydraulic engineering.     

岩体弹脆性损伤本构模型及工程应用

应用连续介质损伤力学理论，从岩体内部微裂纹产生和扩展的损伤机理出发，推导出应变空间表示的坚硬岩体的弹性－损伤耦合的各向异性弹脆性损伤本构模型，并给出相应的损伤变量演化方程。根据拉西瓦水电站坝址区花岗岩体的试验结果，及现场原位洞的反分析结果，计算得到岩体的弹脆性损伤本构关系式。