The Deformation and Stress Analysis of Na Ba Reservoir Concrete Face Rock-Fill Dam

Based on the APDL （ANSYS Parametric Design Language） and combined with the actual project related to parameters of filling material, imported Duncan-Chang constitutive model which has been widely applied in soil mass and rock-fill in the ANSYS software. With the three-dimensional nonlinear finite element analysis by the mid-point incremental method, what have been computed are the deformation and stress analysis ofNa Ba reservoir CFRD （Concrete Face Rock-fill Dam） in filling period. The calculation results provide practical reference for the dam during construction safety filling stress and deformation analysis and real-time monitoring.

Long-term deformation analysis of Shuibuya concrete face rockfill dam based on response surface method and improved genetic algorithm

Due to the size effects of rockfill materials, the settlement difference between numerical simulation and in situ monitoring of rockfill dams is a topic of general concern.The constitutive model parameters obtained from laboratory triaxial tests often underestimate the deformation of high rockfill dams.Therefore, constitutive model parameters obtained by back analysis were used to calculate and predict the long-term deformation of rockfill dams.Instead of using artificial neural networks (ANNs), the response surface method (RSM) was employed to replace the finite element simulation used in the optimization iteration.Only 27 training samples were required for RSM, improving computational efficiency compared with ANN, which required 300 training samples.RSM can be used to describe the relationship between the constitutive model parameters and dam settlements.The inversion results of the Shuibuya concrete face rockfill dam (CFRD) show that the calculated settlements agree with the measured data, indicating the accuracy and efficiency of RSM.

Seismic Deformation and Seismic Resistance Analysis of Shapai Roller Compacted Concrete Arch Dam Based on Field Monitoring and Dynamic Finite Element Method

Shapai Roller Compacted Concrete(RCC) Arch Dam is the highest RCC arch dam of the 20th century in the world with a maximum height of 132m,and it is the only concrete arch dam near the epicentre of Wenchuan earthquake on May 12th,2008.The seismic damage to the dam and the resistance of the dam has drawn great attention.This paper analyzed the response and resistance of the dam to the seismic wave using numerical simulations with comparison to the monitored data.The field investigation after the earthquake and analysis of insitu data record showed that there was only little variation in the opening size at the dam and foundation interface,transverse joints and inducing joints before and after the earthquake.The overall stability of the dam abutment resistance body was quite good except a little relaxation was observed.The results of the dynamic finite element method(FEM) showed that the sizes of the openings obtained from the numerical modeling are comparable with the monitored values,and the change of the opening size is in millimeter range.This study revealed that Shapai arch dam exhibited high seismic resistance and overload capacity in the Wenchuan earthquake event.The comparison of the monitored and simulated results showed that the numerical method applied in this paper well simulated the seismic response of the dam.The method could be useful in the future application on the safety evaluation of RCC dams.

Application of neural network merging model in dam deformation analysis

In order to improve the prediction accuracy and test the generalization ability of the dam deformation analysis model, the back-propagation（BP） neural network model for dam deformation analysis is studied, and the merging model is built based on the neural network BP algorithm and the traditional statistical model. The three models mentioned above are calculated and analyzed according to the long-term deformation observation data in Chencun Dam. The analytical results show that the average prediction accuracies of the statistical model and the BP neural network model are ~ 0.477 and ＋- 0.390 mm, respectively, while the prediction accuracy of the merging model is ~0. 318 mm, which is improved by 33% and 18% compared to the other two models, respectively. And the merging model has a better generalization ability and broad applicability.

Numerical stress-deformation analysis of cut-off wall in clay-core rockfill dam on thick overburden

The cut-off wall in a clay-core rockfill dam built on a thick overburden layer is subjected to a large compressive pressure under the action of the loads such as the dead weight of both the dam and the overburden layer, the frictional force induced by the differential settlement between the cut-off wall and surrounding soils, and the water pressure. Thus, reduction of the stress of the cut-off wall has become one of the main problems for consideration in engineering design. In this paper, numerical analysis of a core rockfill dam built on a thick overburden layer was conducted and some factors influencing the stress-strain behaviors of the cut-off wall were investigated. The factors include the improvement of the overburden layer, the modeling approach for interfacial contact between the cut-off wall and surrounding soils, the modulus of the cut-off wall concrete, and the connected pattern between the cut-off wall and the clay core. The result shows that improving the overburden layer,selecting plastic concrete with a low modulus and high strength, and optimizing the connection between the cut-off wall and the clay core of the dam are effective measures of reducing the deformations and compressive stresses of the cut-off wall. In addition, both the Goodman element and the mud-layer element are suitable for simulating the interfacial contact between the cut-off wall and surrounding soils.

Deformation warning index for reinforced concrete dam based on structural health monitoring data and numerical simulation

The material mechanical parameters of the dam body and foundation will change when a dam is reinforced during the aging process.This causes significant changes in the structural state of the project and makes it difficult to ensure its structural safety.In this study,a new deformation warning index for reinforced concrete dams was developed according to the prototype monitoring data,statistical models,three-dimensional finite element model(FEM)numerical simulation,and the critical conditions of the dam structure.A statistical model was established to separate the water pressure component.Then,a three-dimensional FEM of the reinforced concrete dam was constructed to simulate the water pressure component.Furthermore,the deformation components that affected the mechanical parameters of the dam under the same amount of reservoir water level change were separated and quantified accurately.In addition,the method for inversion of comprehensive mechanical parameters after dam reinforcement was used.The influence mechanisms of the deformation behavior of concrete dams under the reservoir water level and temperature changes were investigated.A new deformation warning index was developed by combining the forward-simulated critical water pressure component and temperature component in the period of extreme temperature decrease with the aging component separated by the statistical model.The new deformation warning index considers the structural state of the dam before and after reinforcement and links the structural strength criterion and the deformation evolution mechanisms.It provides a theoretical foundation and decision support for long-term service and operation management of reinforced dams.

Effect of Seismic Permanent Deformation on Safety and Stability of Earth-Rock Dam Slope

In order to study the effect of seismic permanent deformation on the safety and stability of earth-rock dam, the permanent deformation is considered as the non-design permanent load, and the stress-strain hysteresis curve is also considered when the earth is under cyclic load. The research work can make the calculation results of plastic collapse more accurate by including the effect of the post-earthquake degree of plastic deformation on the stability of the earth-rock dam, and the dam safety factor decreases from 2.50 to 1.90 after the magnitude-8 earthquake. Moreover, the research work will also improve the design of the earth-rock dam under abnormal operating conditions.

Modeling dam deformation using independent component regression method

In the application of regression analysis method to model dam deformation, the ill-condition problem occurred in coefficient matrix always prevents an accurate modeling mainly due to the multicollinearity of the variables. Independent component regression （ICR） was proposed to model the dam deformation and identify the physical origins of the deformation. Simulation experiment shows that ICR can successfully resolve the problem of ill-condition and produce a reliable deformation model. After that, the method is applied to model the deformation of the Wuqiangxi Dam in Hunan province, China. The result shows that ICR can not only accurately model the deformation of the dam, but also help to identify the physical factors that affect the deformation through the extracted independent components.

地震强度对Upper San Fernando土坝流动变形的影响

对UpperSanFernando土坝进行一组抗震性能分析,采用基于与状态相关的剪胀性理论的临界状态砂土模型,描述土在所有可能加载条件下的响应.除了给出土坝的总体位移及变形状况外,还提供了土在局部位置的应力路径和应力应变关系.堤坝变形的计算值与现场观测的结果非常接近.

基于Theil不等系数的IOWA算子最优变形组合预测模型

针对传统组合预测模型中各单项预测模型赋权问题的不足,提出一种基于Theil不等系数的IOWA算子最优变形组合预测模型。利用IOWA算子,依据各单项预测模型预测值各时间点精度的不同,赋予不同的权系数,建立最优组合预测模型,并将其应用于变形数据分析与预测。实验结果表明,本文方法的预测结果比各单项模型与传统组合模型的结果更准确。

机器视觉技术在大坝表面变形监测中的适用性研究

针对大坝表面变形自动化监测中GNSS系统垂直位移监测精度低、费用昂贵和静力水准仪布设难度大、维修成本高等问题,利用机器视觉技术对大坝表面变形进行监测。室内试验结果表明,相机与标靶距离在100 m范围内,机器视觉的测量精度可达到亚毫米级,且水平和垂直变形位移精度相近。由误差分析可知,标靶与相机的距离与测量精度有明显的相关性,而环境因素是影响远距离监测精度的重要因素,并利用大坝视准线原理优化了机器视觉监测系统。最后以浙江省大力塘水库为试点,对大坝表面变形进行实时监测,结果表明,机器视觉技术完全可满足实际工程需求,且优化后的机器视觉测量技术可明显提高监测数据的精度和稳定性。

基于SSA-LMD-GM的大坝变形组合预测模型

为提高大坝变形预测精度,针对大坝原始监测信号中的噪声,以及其非平稳性、非线性等特点,引入奇异谱分析(SSA)和局部均值分解(LMD)方法,提出SSA-LMD-GM模型。采用奇异谱分析(SSA)对原始监测信号进行去噪处理,为充分提取大坝形变信息特征,利用局部均值分解(LMD)对去噪后的监测信号进行分解。针对乘积函数(PF)分量的特征采用合适的模型预测分析,剩下余项则采用GM(1,1)模型。利用实际工程案例进行检验,结果表明,相较于其他模型,SSA-LMD-GM模型预测精度和拟合精度更加优秀,能较好地预测大坝变形趋势,具有一定的应用价值。

非线性剪胀模型土石坝变形计算适用性评价

以有限元方法为代表的高土石坝变形数值模拟的准确性极大依赖于本构模型对坝料应力应变关系描述的准确性。本文在邓肯-张EB模型基础上,建立了用于分析坝体变形的考虑剪胀的实用性非线性模型(EB-Dilatancy模型,简称为EBD模型)。基于阿尔塔什面板砂砾石坝的大坝变形监测数据,设计了3个反演方案,获得最优的EB模型和EBD模型参数。采用最优参数模拟常规三轴试验,并与实际物理试验进行比较。结果表明:在坝体变形方面,传统的EB模型难以同时准确模拟堆石坝的沉降和水平变形分布,而EBD模型则能够在维持沉降分布模拟精度的基础上提高水平变形的计算精度;EB模型无法实现在合理模拟大坝变形的前提下有效模拟材料单元应力-应变响应,相比之下EBD模型可以同时实现大坝变形和材料单元力学行为的良好模拟。

高心墙堆石坝材料本构模型计算的适用性研究

为研究不同材料本构模型对高心墙堆石坝应力、变形计算的适用性,以RM 300 m级高心墙堆石坝堆石料的室内试验成果为基础,分别对邓肯E-B模型、沈珠江双屈服面模型及MPZG模型进行材料本构验证和坝体有限元分析。研究结果表明:3种模型均能较好地表现堆石料三轴路径下的应力响应,而邓肯EB模型在低围压下体积响应表现效果欠佳;3种模型计算的坝体应力、变形分布均符合一般规律,应力相近,但变形计算中邓肯E-B模型得到的沉降与顺河向位移均较大;在高心墙堆石坝建设初期,可采用邓肯E-B模型进行早期分析,后期宜采用沈珠江双屈服面模型、MPZG模型等进行决策评价。

基于PS-InSAR的小浪底土石坝形变监测与稳定性模拟

探索土石坝形变规律及稳定性分析是全球水利工程所关注的一个重大问题,对保障人民群众生命安全和经济健康发展具有重大意义。采用2017年3月至2021年9月小浪底土石坝55景Sentinel-1A卫星SAR影像,利用PS-InSAR技术,监测到小浪底土石坝近5年从坝顶至坝底呈现“阶梯状”形变趋势,最大形变量达到-86.09 mm;并结合库水位、降雨量等因素,发现坝体整体呈现“夏急冬缓”的季节性形变趋势。进一步采用二维有限元方法,对小浪底土石坝的模拟模型进行渗流、应力分析。在高库水位情况下,相较于低水位情况,坝体渗流量更大、形变速率更大;在应力分析部分,发现坝体的垂直向形变趋势与InSAR监测结果相吻合,亦呈现“阶梯状”形变。研究成果不仅为小浪底土石坝运行稳定性分析及形变历史回溯提供理论基础和决策依据,也说明PS-InSAR技术与二维有限元模型模拟技术在水利工程监测方面具有巨大的应用潜力。

基于BP-PCA-WCA-SVM的混凝土大坝变形预测方法

传统基于单一模型的混凝土大坝变形预测方法预测精度低,噪声稳健性差,泛化能力弱。为解决该问题,提出一种基于贝塔先验主成分分析(BP-PCA)与水循环算法(WCA)优化支撑向量机(SVM)相结合的混凝土大坝变形组合预测方法。首先利用所提BP-PCA模型对变形数据进行多尺度降噪分解,将复杂非线性、非平稳随机过程分解为一系列结构简单的主分量;然后利用WCA优化的SVM(WCA-SVM)对每个主分量分别建立预测模型;最后将多个主分量的预测结果综合叠加得到最终预测结果。以我国中部地区某混凝土大坝变形监测数据开展试验,结果表明,所提BP-PCA模型能够有效挖掘数据中隐含的趋势性和规律性信息,BP-PCA-WCA-SVM模型能够获得较高的预测精度,预测结果的相对误差为1.07%,误差均方根为0.065。相对于Kalman滤液、SVM、CNN 3种方法,所提模型预测性能提升均超过62%,并且具有更强的噪声稳健性和泛化能力。

无人机摄影测量在尾矿坝变形监测分析中的应用

由于尾矿坝安全管理范围大,山地环境特殊,传统测绘手段难以开展,尾矿坝变形位移数据仅通过单点或多点的监测方式获得,因此本文提出一种基于无人机(UAV)摄影测量的尾矿坝变形监测分析方法。该方法通过无人机对尾矿坝两期空间三维地理信息数据的采集,将采集到的两期数据分别进行三维重建并生成点云模型,再利用地理信息三维时空对比分析技术对两期点云模型进行对比分析。结果表明:该方法实现了对尾矿坝由点到面的全方位监测,监测精度可达厘米级,为尾矿坝宏观变形监测及异常变形区域的快速核查及安全巡检等提供了依据。

某高面板堆石坝设计与研究

混凝土面板堆石坝是一种安全经济的坝型,对地形、地质和气候条件有广泛的适用性,在世界范围内得到了广泛的应用,近几十年来得到迅速的发展。本文对某高面板堆石坝进行了设计,采用邓肯张e-b模型,使用通用岩土分析软件MIDAS GTS NX软件对大坝建立了三维模型,拟定三种参数方案,对面板堆石坝的应力与变形进行了分析,确定了最优参数方案,得到了大坝在竣工期及蓄水期的应力与变形,分析结果对工程设计优化、类似工程借鉴、保证工程安全具有一定的参考价值。

软岩筑坝技术在某面板堆石坝的应用研究

本文采用邓肯张e-b模型,使用通用岩土分析软件MIDAS GTS NX软件对大坝建立了三维模型,设计四种不同分区使用软岩的方案,分别为主体、主堆石区、次堆石区以及次堆石区510~610 m高程部分使用软岩,并对四种方案下面板堆石坝的应力与变形进行了分析。得到以下结论:采用软岩的大坝应力与变形分布规律与传统堆石料类似,在次堆石区部分部位使用软岩可以大大降低大坝的应力与变形,软岩用于高面板坝坝体填筑是安全可行的。分析结果对工程设计优化、类似工程借鉴、保证工程安全具有一定的参考价值。

基于KPCA-NGO-LSSVM的混凝土坝变形预测模型

变形作为最直观的监测指标,常用来反映大坝的服役性态变化。为建立更加符合混凝土坝变形的预测模型,实现更高精度的混凝土坝变形预测,针对混凝土坝变形序列呈现不确定性和非线性的特征,将核主成分分析(KPCA)引入最小二乘支持向量机(LSSVM)来约简因子关系,降低预测模型的输入维数和复杂度,同时使用北方苍鹰优化算法(NGO)对最小二乘支持向量机进行参数寻优,构建了基于KPCA-NGO-LSSVM的混凝土坝变形预测模型。工程实例表明,KPCA-NGO-LSSVM模型相比传统多元线性回归(MLR)、LSSVM、KPCA-LSSVM的预测值与实际值的拟合效果更好,预测精度更高,能更有效地预测混凝土坝变形。