Fluid solid coupling model based on endochronic damage for roller compacted concrete dam

According to the characteristics of thin-layer rolling and pouting construction technology and the complicated mechanical behavior of the roller compacted concrete dam （RCCD） construction interface, a constitutive model of endochronic damage was established based on the endochronic theory and damage mechanics. The proposed model abandons the traditional concept of elastic-plastic yield surface and can better reflect the real behavior of rolled control concrete. Basic equations were proposed for the fluid-solid coupling analysis, and the relationships among the corresponding key physical parameters were also put forward. One three-dimensional finite element method （FEM） program was obtained by studying the FEM type of the seepage-stress coupling intersection of the RCCD. The method was applied to an actual project, and the results show that the fluid-solid interaction influences dam deformation and dam abutment stability, which is in accordance with practice. Therefore, this model provides a new method for revealing the mechanical behavior of RCCD under the coupling field.

Influence of construction interfaces on dynamic characteristics of roller compacted concrete dams

To study the influence of construction interfaces on dynamic characteristics of roller compacted concrete dams(RCCDs),mechanical properties of construction interfaces are firstly analyzed. Then, the viscous-spring artificial boundary(VSAB) is adopted to simulate the radiation damping of their infinite foundations, and based on the Marc software, a simplified seismic motion input method is presented by the equivalent nodal loads. Finally, based on the practical engineering of a RCC gravity dam, effects of radiation damping and construction interfaces on the dynamic characteristics of dams are investigated in detail. Analysis results show that dynamic response of the RCC gravity dam significantly reduces about 25% when the radiation damping of infinite foundation is considered. Hot interfaces and the normal cold interfaces have little influence on the dynamic response of the RCC gravity dam.However, nonlinear fracture along the cold interfaces at the dam heel will occur under the designed earthquake if the cold interfaces are combined poorly. Therefore, to avoid the fractures along the construction interfaces under the potential super earthquakes,combination quality of the RCC layers should be significantly ensured.

Intelligent compaction theory of high roller compacted concrete dam

The concept and realization process of intelligent compaction for the construction of high roller compacted concrete dam were presented, as well as the theory of monitoring and intelligent feedback control. Based on the real-time analysis of the compaction index, a multiple regression model of the dam compactness was established and a realime estimation method of compaction quality for the entire work area of roller compacted concrete dam was proposed finally. The adaptive adjustment of the roiling process parameters was achieved, with the speed, the exciting force, the roller pass and the compaction thickness meeting the standards during the whole construction process. As a result, the compaction quality and construction efficiency can be improved. The research provides a new way for the construction quality control of roller compacted concrete dam.

Seepage Mitigation in Hydropower Dams by Optimization in Roller Compacted Concrete Interlayer (Monoliths) Joint Bonding Technology

Roller Compacted Concrete (RCC) has gained favorable recognition in hydropower and water resource dam construction. With optimization in construction technology and materials used for RCC Dams, cost is no longer a major disadvantage as compared to environmental impact, that is, wildlife habitat disruption. In as much as it has become optimal for investment in hydropower dam construction, the scourge for dam failure is still eminent, which is as a result of excessive seepage compromising the integrity of the mechanical properties of the dam. The aim of the paper is to highlight successful application methods in joint bonding to avoid excessive seepage and reduce the autogenous healing to a few years of operation. In view of optimization, this paper presents a comprehensive study on the influences of interlayer joints bonding quality from RCC mix performances and how it consolidates the RCC layers to withstand the shear strength along the interface, especially on the high dams. The case study is the RCC dam at the 750 MW Kafue Gorge Lower Hydropower Station. The scope of the study reviews the joint type judged by Modified Maturity Factor (MMF) with joint surface long time exposed in regions with dry and high temperature, technical measures of layer bonding quality control under condition of long time joint surface exposure, effects of joints shear strength and impermeability of the RCC layers when under the conditions of plastic and elasticity. The subtle observations made during the dam construction phases were with respect to the optimal use of materials in relation to RCC mix designs and the basis for equipment calibration for monitoring important data that can be referenced during analysis of shear forces acting on the RCC dam over time.

RCC坝料改进刚度指标及压实质量综合评估研究

有效控制碾压混凝土压实质量是确保大坝安全稳定运行的前提。本文提出了考虑滞后相位角的碾压混凝土坝料改进刚度指标,并给出了滞后相位角的测定方法;结合耦合滞后相位角改进刚度指标、坝料特性参数、碾压参数和频域压实指标,提出了基于XGBoost算法的碾压混凝土压实质量综合评估方法。实例分析表明,改进刚度指标能够更好表征坝料压实质量,综合评估模型的决定系数约为0.86,表明模型精度较高,计算压实度与实测压实度的相对误差平均值为0.47%。本文方法为碾压混凝土坝施工压实质量控制提供了新的有效途径。

RCC坝仓面碾压质量与进度的增强现实反馈方法

碾压混凝土(RCC)坝仓面碾压质量与进度等施工信息大多以报表和图片等传统方式反馈传递,不利于施工质量缺陷的及时发现和施工进度的总体把握。针对上述问题,本文基于Tsai两步标定法,提出了一种固定相机三维注册求解方法,实现了施工质量固定型增强现实反馈;结合混合注册,提出了仓面施工进度信息的移动型增强现实反馈表达方法。同时,施工质量信息与施工进度信息基于关系型数据库和建筑信息模型(BIM)进行相互关联,实现了施工信息互补增值。通过系统研发和工程应用检验,本文提出的坐标映射方法在施工区域实际配准最大偏差不超过0.5m,同时该模块响应平均时间为5.06s,满足现场使用精度和时效要求;基于移动增强现实的施工进度反馈模块,手机使用时平均帧率达29.55,帧率大于27时间占比96.17%,满足现场使用流畅度要求。本文基于增强现实(AR)所提出的方法为现场管理人员提供了多视角施工信息表达和反馈渠道。

Study on equivalent strength for crack directors of RCC arch dam based on size effect rule

The size effect rule of roller compacted concrete (RCC) fracture toughness was reached on the analysis of fracture toughness of RCC specimens, which have been done by project team. And then the rule was applied to the calculation formula of equivalent strength of crack director in the RCC arch dam, thus a simple and useful formula was reached. The study shows that the equivalent strength of crack directors increases with the increasing intensity of concrete, but the surplus rate of strength of crack directors section decreases with the increasing intensity of concrete and the distance between centers of adjacent crack directors, and that bilateral interval crack directors are more efficient in weakening the strength of section than unidirectional interval crack directors in the case of the same distance between adjacent crack director centers. A good design for crack directors of RCC arch dam is proposed via the rule.

某水库大坝挡水坝段坝后渗漏探测及有限元分析

混凝土坝坝体渗漏影响大坝的安全性和耐久性,危及电器设备正常运行,应及时探查渗漏位置,消除渗漏隐患。为查明某混凝土挡水坝坝后渗漏原因,采用自然电位、跨孔声波、单孔声波、钻孔电视、钻孔取芯、注水试验、压水试验等多种方法对坝体混凝土质量进行检测,并基于检测成果开展有限元分析。检测发现:4号—5号坝段横缝存在渗漏异常,挡水坝段混凝土渗透系数不满足设计抗渗要求,各坝段混凝土存在不同程度蜂窝、离析、空洞和不密实现象,4号坝段520廊道与494廊道存在垂向渗漏通道,5号坝段钻孔之间混凝土存在渗漏通道,且廊道以下及向下游方向混凝土存在渗漏通道。有限元分析结果表明:515 m高程碾压混凝土与常态混凝土交界处为主要渗漏通道。

双峰寺水库大坝上游柔性防渗设计和施工要点分析

碾压混凝土大坝上游防渗设计和施工是这类坝型需要重视的关键环节,而碾压混凝土层面结合质量直接影响坝体的抗渗性,往往是碾压混凝土大坝防渗的薄弱环节。从碾压混凝土上游防渗设计、表面辅助防渗方案选择、原材料性能和施工要点等方面开展研究,最后选定双峰寺水库大坝上游防渗设计方案,明确施工要点,保证工程顺利实施。

翁结水库碾压混凝土重力坝动力特性及其抗滑稳定分析

重力坝是水利工程中最常用的主要水工建筑物之一,混凝土重力坝在地震作用下的动力稳定是坝工设计中的重要问题.本文以翁结碾压混凝土重力坝为对象,取位于河谷中的7、8号溢流坝段和9号非溢流坝段,建立三维有限元模型,通过计算分析了碾压混凝土重力坝在不同工况下的应力变形规律及抗滑稳定性.结果表明:静力荷载作用下,坝体位移符合重力坝一般规律,坝踵主拉应力范围较小;动力荷载作用下,位移等响应在坝顶达到最大,符合鞭鞘效应特征,同时坝体残余位移较小,坝体在一些部位出现瞬时拉应力超标现象,坝基塑性区未发生贯通;对7、8号坝段和9号坝段在建基面及碾压层面进行抗滑稳定验算,坝体坝基均满足稳定要求.

碾压混凝土(RCC)在不同水力梯度下渗透和溶蚀特性研究

通过试验获得了碾压混凝土在不同水力梯度下的渗透特性及溶蚀特性 ,结合孔结构测试结果 ,研究了影响碾压混凝土渗透溶蚀特性的因素 ,为解决碾压混凝土在高水力梯度下是否会造成渗透溶蚀破坏提供依据 .

基于遗传算法的碾压混凝土重力坝温度场多测点反演

由于碾压混凝土重力坝施工现场条件复杂,实验获得的参数与实际参数存在一定的差异。为获得高精度的温度场仿真结果,根据某碾压混凝土重力坝现场实测温度数据,利用遗传算法反演该碾压混凝土坝的绝热温升Q 0、温升常数n和导热系数λ,并运用所得的反演参数进行温度场仿真模拟分析,对比不同测点个数下反演所得参数的可靠性和精确性。结果表明:通过遗传算法进行参数反演可有效提高反演的速度与精度,并且反演所依据的测点个数越多反演结果越接近实测数据,9个测点反演比3个测点反演误差减少了1.43%,比6个测点反演误差减少了0.44%。因此,在利用遗传算法进行参数反演时应尽量选择较多的测点个数,以提高仿真计算的精度。研究结果可为碾压混凝土重力坝热学参数反演提供理论指导和依据。

三峡三期RCC围堰拆除爆破倾倒效果DDA模拟

三峡工程三期RCC围堰采用“以预置集中药室倾倒爆破为主、两端钻孔炸碎爆破为辅”的拆除爆破方案,其中预置集中药室的围堰爆破尤其令人关注.在围堰拆除爆破实施前,应用DDA程序对预置药室按设计顺序依次起爆后,形成围堰倾倒缺口以及围堰倾倒全过程进行了模拟.通过爆破实测振动监测资料分析,围堰倾倒的实际触地时间与模拟触地时间基本一致;通过爆破后水下地形测量,围堰倾倒的缺口形状、倾倒后的形态与模拟计算的结果也基本一致.证明运用DDA程序对三峡三期RCC围堰倾倒爆破效果的爆前预测是成功的,该方法对类似工程的爆破设计、施工和安全防护等具有积极的指导意义.

生长连接模型在RCC施工期温度场仿真分析中的应用

在碾压混凝土(RCC)结构的施工过程中,温控分析是专家学者关注的重点之一。根据RCC薄层浇筑的特点,人们采用层合单元进行网格划分,能有效减少计算模型的节点和单元数;但层合单元模拟浇筑过程需要进行网格重组,且在薄层新浇混凝土与相邻老混凝土的连接部位,层合单元无法直接应用,这些都增加了仿真分析的难度。从有限元单元技术出发,提出的生长连接模型能有效模拟RCC结构的连续浇筑过程,并避免了网格重组,同时解决了新老混凝土单元的连接问题,在保证计算精度的同时提高了计算效率。通过对典型RCC大坝工程施工期温度场的仿真分析,验证了生长连接模型的有效性、合理性。

东南亚地区某碾压混凝土坝裂缝成因及防治措施研究

混凝土裂缝是影响水工结构强度和耐久性的主要因素之一,东南亚地区全年高温多雨,月均最大温差较小(8.6℃),年均温差大(20.2℃),混凝土温度容易控制,但裂缝问题时有发生。依托东南亚地区某碾压混凝土坝,采用有限元研究施工期温度应力的变化规律,分析混凝土开裂的敏感因素,并就其温控防裂措施开展详细研究。结果表明,浇筑长间歇及寒潮侵袭显著影响混凝土温度应力的变化,老混凝土的强约束作用及新老混凝土的温差影响叠加寒潮应力,导致混凝土应力超标出现温度裂缝。在上述研究的基础上,进一步探讨了降低新浇混凝土温度应力的温控措施,为东南亚地区大体积混凝土工程的建设提供一定的参考。

基于碾压混凝土破坏特征研究

以目前碾压混凝土重力坝坝体破坏特点为背景,利用扩张有限元数值方法,对碾压层厚度对大坝应力分布规律和裂缝扩展的影响进行了研究,并将在同一超载系数下的计算结果进行了比较,其中,超载系数从1.04~3.04,一共9种。在同样的过载条件下,裂缝的垂直延伸长度随碾压层的加厚而略有下降,裂缝的垂直延伸长度比正常情况下要小,仅在K=2.29、K=2.79两个位置与正常情况相当。大坝的压应力和物质的抗压强度相近,表明大坝在这个时候会出现总体失稳,而且裂缝的发展会转向沿河流的流向;在坝体各部位的材料达到对应的强度后,裂缝的横向发展速率会迅速增加,直至整个坝体的断裂。通过对4种不同荷载作用下坝体裂缝扩展深度、坝顶位移、坝踵及坝址处的受力情况进行了比较,结果显示,不同荷载作用下坝体裂缝呈现出脆性突发性破坏特征;结果表明:在荷载作用下,坝体裂缝扩展深度和坝顶位移均有一定程度的降低。

国产设备及仪器在60cm厚RCC碾压试验中的应用

推广碾压混凝土厚层碾压施工方法,采用国内自主研发的垂直振动碾压设备、压实度检测仪器及检测孔成孔装置,在贵州盐井水利枢纽工程进行60 cm厚RCC碾压试验。试验所得混凝土压实度及芯样抗压、抗渗、抗冻强度和压水试验成果均满足规范要求,表明国产LDV 150型双钢轮垂直振动碾碾压60 cm厚RCC的振动频率、激振力及振幅大小适宜,H型核子快速密度仪和厚层RCC压实度检测孔的成孔装置应用于检测RCC压实度方法简捷,国产设备及仪器应用于RCC厚层碾压施工技术可行。

干热河谷气候环境对碾压混凝土性能的影响研究

采用大型步入式极端气候模拟器模拟干热河谷地区低湿度、强日照复杂气候环境,深入开展了大坝碾压混凝土力学性能、体积变形性能演化规律研究。结果表明,干热河谷气候环境对大坝三级配碾压混凝土的立方体抗压强度、轴压性能、轴拉性能等均存在较大影响,混凝土标准养护时间越短,干热河谷气候环境作用下混凝土的力学性能下降越明显;干热河谷气候环境下大坝三级配碾压混凝土的干缩变形呈双曲线模型演化规律,在干热河谷地区实施碾压混凝土工程应特别注意加强早期养护。

论RCC筑坝技术中的几个关键性问题

文章通过分析论证，提出：①低、中、高胶凝材料的ＲＣＣＤ，各有其优缺点，应根据１程的具体情况采用，不宜过份强调某一种。②已建ＲＣＤ的渗漏主要是＂漏＂的问题，因而坝面防渗措施是最为有效的。在靠近坝面部位采用细骨科高胶ＲＣＣ，并对层面进行喷净浆等简易有效的处理措施，将是今后防渗措施的发展方向。③ＲＣＣＤ的层面抗剪（断）强度较低，应认真对待。文章通过综合分析，提出了不同类型ＲＣＣＤ层面抗剪断参数的数值，以及多种提高抗滑稳定的结构措施（并提出了对防渗和抗滑都有利的一种＂金包银＂或＂银包银＂坝体的新概念），说明对于高坝，乃至特高的坝，采用ＲＣＣＤ也不是不可能的。

RCC重力坝防渗体温度场的三维有限元浮动网格法仿真分析

利用三维有限元浮动网格法,对采用不同厚度的常态混凝土、二级配碾压混凝土、变态混凝土防渗结构的碾压混凝土坝温度场进行了仿真计算。结果表明,不同形态的混凝土防渗结构对碾压混凝土坝体温度场的影响不大;而防渗体厚度对其自身温度的影响较大,防渗体厚度过大或过小,都对其温控不利;对三级配碾压混凝土坝采用二级配碾压混凝土中等厚度(D=3m)的防渗体已能满足温控要求。