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.

Vibration sensitive admixture for roller compacted concrete

In order to further speed up the construction progress,shorten the rolling time and reduce the rolling times of roller compacted concrete after analyzing work of construction progress improvement measures of roller compacted concrete,research on vibration sensitive admixture is carried out and satisfactory results are acquired.The new type vibration sensitive admixture was used in the project of Jinghong hydropower station in Yunnan Province,China.The engineering experimental results show that various indexes have been verified.Meanwhile,the compactness of roller compacted concrete is improved under the same rolling times,the rolling times and the duration time can be reduced under the same compactness requirement in construction practice.

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.

基于融合GNSS/UWB/RTS的RCC坝智能监控定位补偿方法研究

近年来,大坝压实质量的智能监控技术逐渐成为研究热点。现有的碾压混凝土(RCC)坝碾压作业过程实时监控技术依赖于全球导航卫星系统(GNSS),然而,对于建设在深窄河谷地区的RCC坝,GNSS系统易受两侧山体信号遮挡干扰。针对上述问题,本研究提出一种基于融合GNSS/UWB/RTS的RCC坝碾压施工智能定位补偿技术。首先,依据悬崖边壁、倒悬体遮挡处的环境特征建立了适用于深窄河谷地区的RCC坝碾压实时监控数学模型;其次,引入了超宽带(UWB)和机器人全站仪(RTS)定位补偿技术,采用耦合新息阈值与最小二乘的改进卡尔曼滤波算法融合GNSS/UWB/RTS的定位数据,实现了遮挡环境下卫星信号的连续稳定定位监控;最后,在西南某大型RCC坝工程中得到应用。结果表明,该方法能够实现对深窄河谷中RCC坝碾压施工的全地形、全过程实时监控,可弥补单纯依赖GNSS进行碾压过程实时监控所不足。

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 .

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.

RCC拱坝的封拱温度与温度荷载研究

在对RCC拱坝封拱温度与温度荷载特点分析的基础上,用4座不同坝高的RCC拱坝分别以坝体多年平均温度和由仿真分析计算得到的蓄水时的实际温度作为温度荷载的计算起点,用有限元等效应力法计算不同坝高的坝体应力,根据计算结果讨论不同坝高时RCC拱坝的封拱温度与温度荷载。计算表明,以多年平均温度作为封拱温度计算温度荷载与仿真方法计算的温度荷载的差距随着坝高的增大而增大。对于100m以上的拱坝应该用仿真分析的方法研究温度荷载,以确定真实的封拱温度;不进行二期水冷和封拱灌浆时,对于100m以上的高拱坝,要进行充分论证,一般坝踵可能会出现较大拉应力而引起坝踵开裂;对于RCC高拱坝应采用冷却水管和分缝相结合的方式,在蓄水前通过二期水冷使坝体温度下降到设计封拱温度后进行封拱灌浆,以减小运行期的温度荷载。

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。

不同VC值下基于压实功的RCC碾压参数控制标准确定方法

碾压混凝土(RCC)的压实质量主要由VC值及各施工碾压参数(碾压机静压力、激振力、行驶速度、碾压遍数等)控制。若对单个碾压参数分别加以控制,不但会增加控制难度,而且由于现场施工情况的多变性,不易保证压实质量。本文基于压实功这一综合反映施工碾压参数的指标,利用自主研制的多参数可调式RCC碾压模拟试验装置,开展了不同VC值下RCC碾压试验,分别建立了考虑VC值的改进单位体积压实功与RCC本体压实密度、改进单位面积压实功与层面抗剪强度比的关系模型,进而提出了基于压实功的不同VC值下碾压参数控制标准的确定方法。结果表明:所建立的关系模型相关性良好,利用提出方法确定的碾压遍数标准与实际施工基本一致,从而可为应对现场VC值变化情况下的RCC碾压参数的动态调整提供依据和途径。

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。

三峡三期RCC围堰倾倒法拆除涌浪测试模型试验

长江三峡工程三期上游碾压混凝土围堰中段380 m采用预埋药室(孔)向上游倾倒爆破法予以拆除,围堰倾倒时产生的涌浪是否会对周围建筑物和环境造成危害,一直是人们关注的问题,通过1∶100的围堰倾倒模型试验,测得了围堰倾倒时的涌浪特性、传播规律,并预测了实际围堰爆破时将产生的涌浪高度,对围堰爆破的安全防护设计具有重要的指导意义。实际围堰爆破时的涌浪观测资料也验证了模型试验成果的正确性。

主要掺合料对RCC抗裂性能影响的研究

本文在试验的基础上,就粉煤灰、硅粉和氧化镁等主要掺合料对碾压混凝土(RCC)抗裂性能的影响进行了研究,提出抗折强度与折压强度之和的百分比来量化标定这些掺合料对碾压混凝土的抗裂性能的影响,得到比较理想的结果。在此基础上,得到当粉煤灰掺量为60%,硅粉和氧化镁掺量均为5%复合掺入时,对碾压混凝土的抗裂性能的改善最佳。

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。

基于RCC及SFRC的振动拌和方案选择

通过对几种振动拌和方案的分析,讨论了对振动拌和方案的选择方法及影响因素,认为对于RCC和SFRC,较好的振动拌和方案为振动与搅拌相结合:根据RCC和SFRC的物理力学性能及结构流变特性,选择了周期式立轴振动拌和方案,并对其试验样机的设计进行了详细分析,提出使用该样机并合理选择参数,可使搅拌达到较好效果。

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。

基于单因素试验的三级配RCC施工配合比研究

根据坝体碾压混凝土性能指标和施工要求,利用单因素试验研究了坝体不同标号三级配混凝土的粗细骨料组合、粉煤灰掺量、水胶比和砂率,并采用绝对体积法给出了施工配合比。试验结果表明,当采用玄武岩与灰岩为粗细骨料组合、大石∶中石∶小石为35∶35∶30、砂率为32%、用水量为88kg/m3、粉煤灰掺量为50%时,能满足C25、C20和C15坝体碾压混凝土各项性能指标和施工要求。

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。

基于Delphi的RCC大坝施工过程仿真

计算机仿真技术为水利水电施工过程的研究开创了新的方法。与现代化的计算手段相结合,使水电工程施工方案的选择从凭经验和类比的方法进入到更为科学的方法。本文以Delphi为系统仿真开发工具,对碾压混凝土坝施工过程进行仿真,实现了以缆机为浇筑机械的施工方案比选。