Technical Progress on Researches for the Safety of High Concrete-Faced Rockfill Dams

The concrete-faced rockfill dam(CFRD) is an important dam type in the selection of high dams to be constructed in Western China,owing to its direct utilization of local materials,good adaptability,and distinct economic advantages.Over the past decades,China has gained successful experience in the construction of 200 m CFRDs,providing the necessary technical accumulation for the development of 250–300 m ultra-high CFRDs.This paper summarizes these successful experiences and analyzes the problems of a number of major 200 m CFRDs around the world.In addition,it discusses the key technologies and latest research progress regarding safety in the construction of 250–300 m ultra-high CFRDs,and suggests focuses and general ideas for future research.

Seepage simulation of high concrete-faced rockfill dams based on generalized equivalent continuum model

This research focused on the three-dimensional(3 D) seepage field simulation of a high concrete-faced rockfill dam(CFRD) under complex hydraulic conditions. A generalized equivalent continuum model of fractured rock mass was used for equivalent continuous seepage field analysis based on the improved node virtual flow method. Using a high CFRD as an example, the generalized equivalent continuum range was determined, and a finite element model was established based on the terrain and geological conditions, as well as structural face characteristics of the dam area. The equivalent seepage coefficients of different material zones or positions in the dam foundation were calculated with the Snow model or inverse analysis. Then, the 3 D seepage field in the dam area was calculated under the normal water storage conditions, and the corresponding water head distribution, seepage flow, seepage gradient, and seepage characteristics in the dam area were analyzed. The results show that the generalized equivalent continuum model can effectively simulate overall seepage patterns of the CFRD under complex hydraulic conditions and provide a reference for seepage analysis of similar CFRDs.

A simplified physically-based breach model for a high concrete-faced rockfill dam:A case study

A simplified physically-based model was developed to simulate the breaching process of the Gouhou concrete-faced rockfill dam （CFRD）, which is the only breach case of a high CFRD in the world. Considering the dam height, a hydraulic method was chosen to simulate the initial scour position on the downstream slope, with the steepening of the downstream slope taken into account; a headcut erosion formula was adopted to simulate the backward erosion as well. The moment equilibrium method was utilized to calculate the ultimate length of a concrete slab under its self-weight and water loads. The calculated results of the Gouhou CFRD breach case show that the proposed model provides reasonable peak breach flow, final breach width, and failure time, with relative errors less than 15% as compared with the measured data. Sensitivity studies show that the outputs of the proposed model are more or less sensitive to different parameters. Three typical parametric models were compared with the proposed model, and the comparison demonstrates that the proposed physically-based breach model performs better and provides more detailed results than the parametric models.

Three-dimensional seismic response analysis of a concrete-faced rockfill dam on overburden layers

Reasonable seismic response analysis of a high rockfill dam is of great engineering significance in guiding its design and ensuring its seismic safety during operation,especially of a concrete-faced rockfill dam(CFRD)on overburden layers.The three-dimensional seismic behavior of the Miaojiaba CFRD is simulated and analyzed by the finite element method(FEM).The results indicate that:1)the amplification coefficient along the dam axis gradually increases with the altitude,and reaches maximum at the dam crest;2)the vertical residual deformation mainly exhibits downwards and reaches maximum near the dam crest;3)the earthquake significantly aggravates the deformation of peripheral joints;4)the impounding condition and overburden characteristics have great effects on the dam's seismic response.

300m级高面板堆石坝适应性及对策研究综述

"300 m级高面板堆石坝适应性及对策研究"课题对已建的200 m级高面板堆石坝建设进行了系统的技术总结,并围绕拟建的300 m级高面板堆石坝的主要技术问题开展研究,即:经济优势及筑坝条件,筑坝材料特性,坝体分区与变形控制,坝体稳定性评价与变形控制标准,防渗和止水结构适应性,坝体填筑程序及施工质量控制等,取得了一系列成果。研究认为,在适当条件下,采取适当的工程技术措施后,建设300 m级高面板堆石坝是可行的。研究报告还提出了进一步的研究方向和重点课题。

高面板堆石坝变形控制的若干问题

目前面板堆石坝的高度已从 10 0m级发展到 2 0 0m级 ,由于分期施工 ,高面板堆石坝的坝体变形性状更加复杂 .本文以 2 5 0m典型高面板坝为例 ,采用清华非线性K -G模型 ,分析了高面板坝的一些特殊变形问题 ,提出 :优化施工临时剖面 ,以防止坝体在施工期出现过大的差异变形而产生裂缝 ;分期面板的浇筑高程要与堆石体的顶部保持一定的高差 ,以防止面板与支承堆石体间出现脱空 ;对高坝、特别是峡谷地区的高面板坝 ,要注意减少面板的法向变形 ,以控制坝肩附近周边缝和垂直缝的三向变形 .

高面板堆石坝面板应力规律分析及改善应力状态的对策

本文分析了面板应力分布及其产生的原因,采用接触力学分析方法模拟混凝土面板和堆石体之间的接触关系,应用假设应变单元,消除因弯曲变形造成的面板单元剪切自锁问题,从而减少面板挠度和应力数值计算误差。在面板温度仿真计算方面,针对不同的入仓温度采用不同的混凝土绝热温升曲线。变形、温度和湿度等方面数值计算显示,弯曲应力场、遭遇寒潮后的温度应力场以及湿度应力场分布趋势相同,它们叠加后,易使面板发生裂缝。最后对某在建高面板堆石坝,提出采用增大面板与堆石体的高程差、推迟Ⅱ期面板浇筑和喷涂聚氨酯保温板等工程措施,以改善面板应力状态。计算结果表明,面板拉应力可降低一个数量级,由原来的1.0MPa量级下降到0.1MPa量级。

覆盖层上高面板堆石坝的极限抗震能力

针对地震作用下面板坝的非线性动力反应,为了准确评估大坝的极限抗震能力,从坝坡抗震稳定性、坝体震后残余变形、坝基覆盖层液化和面板接缝变形等方面探讨面板坝的地震破坏计算方法和评价标准。采用三维有限元法,对某覆盖层上高135 m的混凝土面板堆石坝进行极限抗震能力计算,结合多角度综合分析表明,大坝的极限抗震能力约为0.52g^0.54g,大坝具有较强的抗震能力。

洪家渡200m级高面板堆石坝面板混凝土防裂技术

面板混凝土裂缝防控是面板堆石坝的技术难题之一。洪家渡大坝除严格控制坝体变形,避免面板产生结构性裂缝外,在借鉴已有工程经验的基础上,结合洪家渡工程特点,从混凝土材料、面板结构和温度控制等方面,采取了"三双"防裂措施。施工期和运行初期检查结果表明,面板无结构性裂缝,温度性裂缝仅33条,每万m2裂缝少于5条,洪家渡大坝面板混凝土防裂技术取得了良好效果。

基于灰色理论的高面板堆石坝沉降预测研究

基于灰色系统理论,建立了进行高面板堆石坝坝体沉降预测的GM(1,1)模型,并用该模型对公伯峡面板坝的坝体沉降进行了灰色预测,结果表明,运用该模型对高面板堆石坝的坝体沉降进行预测是可行的,预测结果也是较为合理的。

覆盖层上高面板堆石坝地震反应特性研究

对西南强震区某拟建覆盖层上高面板堆石坝进行不同超越概率地震波作用下的地震反应计算分析,重点研究大坝在强震作用下动位移、加速度、面板动应力及坝基覆盖层液化等地震反应特性.研究表明:随着输入地震波峰值的增大,大坝动位移和加速度、面板动应力、覆盖层动孔压和液化度等反应均逐渐增大,但加速度放大倍数逐渐减小.在100年超越概率2%的校核地震作用下,大坝的抗震安全性依然在合理范围之内,大坝的抗震设计是合理的.

我国高坝建设和科技攻关

介绍了我国大坝建设的发展和特点 ,概括了高坝建设中的地质勘探、坝工技术、泄洪消能、坝基处理和高边坡处理等方面的科技成果和应用水平 ,展望了我国高坝发展前景并指出今后高坝科技攻关重点。

甘肃西流水面板堆石坝应力变形分析研究

采用非线性有限元分析方法,对甘肃省龙首二级(西流水)水电站面板堆石坝的应力变形特性进行了分析,给出了坝体及面板在施工期和蓄水期的应力和位移分布,并分析了高趾墙的应力变形特性。计算结果表明,由于西流水面板堆石坝位于狭窄河谷,坝体的变形受岸坡约束影响较大,面板在蓄水期沿坝轴线方向和坝坡方向呈双向受压状态,高趾墙大部分区域承受拉应力,但拉应力数值不大。本文的计算分析结果除可以为西流水工程的设计、施工提供依据外,对其它类似工程也具有一定的参考价值。

利用各向异性软岩筑高混凝土面板堆石坝关键技术研究

首先在混凝土面板堆石坝工程中提出各向异性软岩筑坝的概念,与纯粹的软、硬岩筑坝予以区别。通过研究各向异性软岩之绿泥石片岩和其衍生堆石料,揭示各项异性软岩的物理力学特性。然后,在硬岩、砂砾石筑坝坝体主要分区示意图的基础上,提出各向异性软岩筑坝坝体主要分区示意图及相关施工措施。以新疆某水电站面板堆石坝工程为例,就该坝址区特殊的地形地质条件,对标准断面3种分区方案建立三维模型,辅以非线性有限单元法数值仿真,并对结果进行分析、比较,给出推荐方案,达到充分利用当地各向异性软岩的目的。

高面板堆石坝软缝接触计算模型及其数值实现

设置软接触纵缝是防止高面板堆石坝发生面板挤压破损的常用工程措施。分析软缝填缝料的挤压特性,提出一个简单实用的双线性软缝挤压模型。通过将软缝概化为可发生相互贯入的软接触界面,提出基于计算接触力学的摄动Lagrange格式,发展相应的软缝接触算法,并采用三维接触分片试验验证算法的有效性。结合天生桥一级面板堆石坝进行计算分析,结果表明设置软缝可有效减低面板的坝轴向挤压应力。