Major Technologies for Safe Construction of High Earth-Rockfill Dams

The earth-rockfill dam is one of the primary dam types in the selection of high dams to be constructed in Western China, since it is characterized by favorable adaptability of the dam foundation; full utilization of local earth, rock, and building-excavated materials; low construction cost; and low cement consumption. Many major technical issues regarding earth-rockfill dams with a height of over 250 m were studied and solved successfully in the construction of the 261.5 m Nuozhadu earth core rockfill dam. This paper describes research achievements and basic conclusions; systematically summarizes the accumulated experiences from the construction of the Nuozhadu Dam and other high earth-rockfill dams; and discusses major technical issues, such as deformation control, seepage control, dam slope stability, safety and control of flood discharging, safety and quality control of dam construction, safety assessments, early warning, and other key technical difficulties. This study also provides a reference and technological support for the future construction of 300 m high earth-rockfill dams.

Prediction of Concrete Faced Rock Fill Dams Settlements Using Genetic Programming Algorithm

In the present study a Genetic Programing model (GP) proposed for the prediction of relative crest settlement of concrete faced rock fill dams. To this end information of 30 large dams constructed in seven countries across the world is gathered with their reported settlements. The results showed that the GP model is able to estimate the dam settlement properly based on four properties, void ratio of dam’s body (e), height (H), vertical deformation modulus (Ev) and shape factor (Sc) of the dam. For verification of the model applicability, obtained results compared with other research methods such as Clements’s formula and the finite element model. The comparison showed that in all cases the GP model led to be more accurate than those of performed in literature. Also a proper compatibility between the GP model and the finite element model was perceived.

The Effect of Alluvial Foundation on the Earth Dams Settlement

Careful monitoring in the earth dams, to measure deformation caused by settlement and movement has always been a concern for engineers in the field. In order to measure settlement and deformation of earth dams, usually the precision instruments of settlement set and combined Inclinometer that is commonly referred to IS instrument, will be used. In some dams, because the thickness of alluvium is high and there is no possibility of alluvium removal (technically and economically and in terms of performance), there is no possibility to place the end of IS instrument (precision instruments of Inclinometer-settlement set) in the rock foundation. Inevitably, have to accept installing pipes in the weak and the deformable alluvial foundation that this leads to errors in the calculation of the actual settlement (absolute settlement) in different parts of the dam body. The purpose of this paper is to present new and refine criteria for predicting settlement and deformation in earth dams. The study is based on conditions in three dams with a deformation quite alluvial (Agh Chai, Narmashir and Gilan-e Gharb) to provide settlement criteria affected by alluvial foundation. To achieve this goal, the settlement of dams was simulated by using finite difference method with FLAC3D software and then the modeling results were compared with reading IS instrument. In the end, the caliber of the model and validate the results, by using regression analysis techniques and scrutinized modeling parameters with real situations and then by using MATLAB software and Curve Fitting Toolbox, a new criteria for the settlement based on elasticity modulus, cohesion, friction angle, density of earth dam and alluvial foundation was obtained. The results of these studies show that, by using the new criteria measures, the amount of settlement and deformation for the dams with alluvial foundation can be corrected after instrument readings and the error rate in reading IS instrument can be greatly reduced.

DAMS静力水准自动化监测系统在广州地铁中的实践

DAMS静力水准自动化监测系统是一种高精密液位测量系统,该系统适用于测量多点的相对沉降,具有精度高、自动化性能好等特点。主要用于大型水利枢纽工程等各测点不均匀沉降的测量。本文通过案例,介绍了该系统在广州地铁变形监测中的应用,可为类似的监测项目提供参考。

Nonlinear finite element analysis of effect of seismic waves on dynamic response of Shiziping dam

Many high earth-rockfill dams are constructed in the west of China. The seismic intensity at the dam site is usually very high, thus it is of great importance to ensure the safety of the dam in meizoseismal area. A 3D FEM model is established to analyze the seismic responses of Shiziping earth-rockfill dam. The nonlinear elastic Duncan-Chang constitutive model and the equivalent viscoelastic constitutive model are used to simulate the static and dynamic stress strain relationships of the dam materials, respectively. Four groups of seismic waves are inputted from the top of the bedrock to analyze the dynamic responses of the dam. The numerical results show that the calculated dynamic magnification factors display a good consistency with the specification values. The site spectrum results in larger acceleration response than the specification spectrum. The analysis of relative dynamic displacement indicates that the displacement at the downstream side of the dam is larger than that at the upstream side. The displacement response reduces from the center of river valley to two banks. The displacement responses corresponding to the specification spectrum are a little smaller than those corresponding to the site spectrum. The analysis of shear stress indicates that a large shear stress area appears in the upstream overburden layer, where the shear stress caused by site waves is larger than that caused by specification waves. The analysis of dynamic principal stress indicates that the minimum dynamic stresses in corridor caused by specification and site waves have little difference. The maximum and minimum dynamic stresses are relatively large at two sides. The largest tensile stress occurs at two sides of the floor of grouting corridor, which may result in the crack near the corridor side. The numerical results present good consistency with the observation data of the grouting corridor in Wenchuan earthquake.

Deformation prediction model of concrete face rockfill dams based on an improved random forest model

The unique structure and complex deformation characteristics of concrete face rockfill dams(CFRDs)create safety monitoring challenges.This study developed an improved random forest(IRF)model for dam health monitoring modeling by replacing the decision tree in the random forest(RF)model with a novel M5'model tree algorithm.The factors affecting dam deformation were preliminarily selected using the statistical model,and the grey relational degree theory was utilized to reduce the dimensions of model input variables.Finally,a deformation prediction model of CFRDs was established using the IRF model.The ten-fold cross-validation method was used to quantitatively analyze the parameters affecting the IRF algorithm.The performance of the established model was verified using data from three specific measurement points on the Jishixia dam and compared with other dam deformation prediction models.At point ES-10,the performance evaluation indices of the IRF model were superior to those of the M5'model tree and RF models and the classical support vector regression(SVR)and back propagation(BP)neural network models,indicating the satisfactory performance of the IRF model.The IRF model also outperformed the SVR and BP models in settlement prediction at points ES2-8 and ES4-10,demonstrating its strong anti-interference and generalization capabilities.This study has developed a novel method for forecasting and analyzing dam settlements with practical significance.Moreover,the established IRF model can also provide guidance for modeling health monitoring of other structures.

Evaluation of behaviors of earth and rockfill dams during construction and initial impounding using instrumentation data and numerical modeling

In this study,the behavior of Gavoshan dam was evaluated during construction and the first impounding.A two-dimensional（2D） numerical analysis was conducted based on a finite difference method on the largest cross-section of the dam using the results of instrument measurements and back analysis.These evaluations will be completed in the case that back analysis is carried out in order to control the degree of the accuracy and the level of confidence of the measured behavior since each of the measurements could be controlled by comparing it to the result obtained from the numerical model.Following that,by comparing the results of the numerical analysis with the measured values,it is indicated that there is a proper consistency between these two values.Moreover,it was observed that the dam performance was suitable regarding the induced pore water pressure,the pore water pressure ratio r;,settlement,induced stresses,arching degree,and hydraulic fracturing probability during the construction and initial impounding periods.The results demonstrated that the maximum settlement of the core was 238 cm at the end of construction.In the following 6 years after construction（initial impounding and exploitation period）,the accumulative settlement of the dam was 270 cm.It is clear that 88% of the total settlement of the dam took place during dam construction.The reason is that the clay core was smashed in the wet side,i.e.the optimum moisture content.Whereas the average curving ratio was 0.64 during dam construction; at the end of the initial impounding,the maximum amount of curving ratio in the upstream was 0.81,and the minimum（critical） amount in the downstream was 0.52.It was also concluded that this dam is safe in comparison with the behaviors of other similar dams in the world.

Climate,Ecosystem and Migration:The Three Gorges Dam Study

The Three Gorges Dam,known as one of the biggest project items throughout the history,is a milestone for the development of China.Since it was completed in 2006,the dam has been persistently supplying ample electricity to the southern and eastern part of China.Despite its impressive output and benefits notwithstanding,we have to objectively pay our attention to the long-term impact that the Three Gorges Dam leaves to the place where we live,especially the influence on the climate,the ecosystem and the migration pattern of the reservoir area.

高纬度高寒区面板堆石坝防渗面板修复方案及经验

JLBLK水电站大坝是建于高纬度高寒区的百米级全断面堆石面板坝,最大坝高140.3 m。通过降水处理,现场发现18^(#)、19^(#)面板挤压破损程度严重且有加剧趋势,25^(#)、26^(#)、27^(#)面板断裂。经与国内外同类工程比较,水库渗漏量总体偏大,变形量偏大,且尚未收敛,三维流变反演成果表明后期尚有17%的沉降量。为保证修复效果满足后期变形和渗透稳定需要,针对18^(#)、19^(#)面板水上破损区采用高于原设计强度混凝土分小区进行补强,并结合工程特点和设计方案提出适合本工程的修复施工方案,修复后面板各项指标均满足要求。

采用Karhunen-Loève分解计算堤坝沉降区间场

大坝的建造以及运行过程中受多种内外部多因素耦合作用,其沉降分析是复杂、非线性问题,采用非概率区间方法构造大坝沉降区间有利于定量描述多源不确定信息,使计算更加吻合实际情况。本文将基于Karhunen-Loève分解的区间场有限元方法由线弹性模型扩展至邓肯-张模型中,通过引入平方指数形式的空间依赖函数描述切线模量的空间变异性。采用以Legendre多项式为基函数的Galerkin方法计算模量变化区域的特征值与特征函数。在区间有限元的框架下,编写非线性区间本构模型Abaqus用户子程序UMAT,结合Python脚本计算大坝沉降针对于模量参数变化的响应区间,并与传统顶点集区间方法进行对比。工程实例分析表明,所提方法可以有效计算大坝沉降区间,所得到的沉降区间能涵盖顶点集区间,且有限元计算次数由指数级减少为多项式级。本文方法可以进一步扩展至大坝长期变形区间计算问题。

筑坝土石料填筑干密度数字特征的动态优化方法研究

提出了一种现场填筑过程中坝料压实质量控制指标的调整优化方法。利用土石坝填筑现场取得的实测干密度,确定已填筑坝料干密度的随机场数字特征(均值、标准差和相关距离),根据坝料变形参数与干密度相关关系,构建坝体变形参数的随机场,进行坝体随机有限元计算,预测未来大坝的结构响应,从而预判大坝的安全性。并在此基础上,基于二次多项式,建立了各分区坝料干密度随机场数字特征与大坝变形响应的统计特征(均值、标准差)的响应面方程,进而推求大坝变形响应的超越概率表达式,为坝料碾压施工参数优化提供指导,提高大坝安全性。以一实际工程为例,根据不同填筑阶段各分区坝料现场干密度的数字特征,分析了坝料参数的不确定性与大坝结构响应之间的规律。研究表明,随着填筑进度的变化,大坝不确定变形响应分析趋于稳定,心墙料干密度数字特征对坝体最大沉降和倾度影响最大。在此基础上,通过调整大坝变形响应的超越概率变化规律,可以得到优化后的各分区坝料现场干密度的随机场数字特征,从而指导下一填筑阶段大坝的现场碾压施工,以提高大坝变形的控制水平和安全评价精度。

某平原水库坝顶裂缝成因分析及评价

某平原水库增容后围坝出现不均匀沉降,导致局部坝段坝顶出现不同程度的裂缝,影响大坝正常运行。为评价裂缝是否影响水库运行安全,通过现场检查和地质勘察,并查阅设计、施工及运行管理资料,对坝顶裂缝产生的原因进行分析和评价。结果表明:局部坝段坝顶裂缝主要是由于坝基不均匀沉降和坝体局部密实度较差引起的,虽然围坝现状未出现短期急速下沉,但不排除裂缝继续发展危及坝坡稳定和破坏防渗完整性的风险,建议对围坝进行灌浆加固。

基于光纤陀螺的堆石坝内部沉降分布式监测技术研究

针对传统堆石坝内部沉降监测技术已难于满足超高堆石坝内部沉降监测需求。文章开发了基于光纤陀螺仪(FOG)的堆石坝内部沉降分布式监测系统,该系统主要由监测管道、监测小车和牵引装置组成。推导FOG监测系统测量坝体内部沉降的原理,考虑监测小车不匀速问题,建立监测小车运行速度函数关系,引进经验模态(EMD)-小波混合降噪方法滤除监测小车运行过程中的振动噪声和FOG漂移误差。该监测系统成功应用于猴子岩面板堆石坝。现场监测结果表明,FOG2次独立测量结果的相关系数为0.986,说明FOG监测系统工作性能稳定,与水管式沉降仪测量结果基本一致,验证了该系统的可行性和准确性。

基于EMD-MGWO-LSTM的大坝沉降预测模型

大坝变形预测的准确性对大坝结构稳定和整体安全至关重要。近年来,为提升预测精度,优化算法广泛应用于大坝预测模型。然而,传统优化算法易陷入局部最优解,制约模型性能。为此,引入一种随机搜索机制至灰狼算法(grey wolf optimizer,GWO),通过Metropolis接受准则进一步改进GWO,优化算法性能。然后,创新性地将经验模态分解(empirical mode decomposition,EMD)、改进灰狼算法(modify GWO,MGWO)以及长短期记忆网络(long short-term memory network,LSTM)相融合构建一个先进的大坝沉降预测模型。以新疆五一水库实测数据作验证,采用EMD对实测数据进行处理,深入分析各分量不同的变化特征;随后,利用MGWO对LSTM的超参数精确调优,实现大坝沉降的精准预测。最后将EMD分解前后模型进行了对比分析。结果表明,提出的EMD-MGWO-LSTM大坝沉降预测模型在4个误差性能指标上均表现出显著优势,具有更高的拟合精度和卓越的预测性能。研究成果增强了其适应性,在复杂多变的大坝动态运行环境中仍然能够保持快速的响应和准确的预测,为大坝安全监测与预警提供技术支撑,有力地推动了水利现代化防洪减灾技术的发展与升级。

兰州新区庙儿沟水库心墙堆石坝沉降计算分析

兰州新区庙儿沟水库工程地处兰州新区,为注入式水库,库容比较大,坝体采用壤土心墙土石坝。以Midas GTS NX软件为计算工具,采用邓肯-张(E-B)材料本构模型对坝体进行施工分层模拟以及蓄水期沉降计算。通过计算分析可知,坝体在施工期以及蓄水期的沉降和应力均满足规范要求,表明坝体结构设计合理。

富水地层大直径顶管穿江过堤三维模拟及实测变形分析

针对顶管法在富水地层穿江过堤时对周围土体及建筑物的扰动问题,分析杭州市取水口上移工程现状,通过理论计算、数值模拟及现场监测的方法对超长距离大直径顶管穿江过堤产生的沉降变形影响进行研究。结果表明修正公式与数值结果吻合较好,但与实测值不完全吻合;随顶管机头掘进,地表变形表现为先隆起再沉降,隆起最大值2.86 mm位于距轴线15 m,最大沉降10.33 mm位于轴线处;堤坝沉降变形量约为地表沉降的1/2,隆起不明显且远小于控制值。

水库面板堆石坝防渗面板修复方案及处理效果研究

以广东XFJ水电站为例,通过对水库面板堆石坝的防渗面板修复方案及处理效果进行深入研究。首先,对水电站的工程概况、运行背景以及存在的渗漏和变形问题进行详细分析。其次,提出了综合应对渗漏和变形问题的方案,包括现场检查、设计方案制定、施工方案制定等关键步骤。特别是针对夏季和冬季气温条件下的施工考虑,提出了相应的机械利用、遮阳措施等建议。最后,通过在修复区域进行的实际施工,验证了修复方案的可行性和效果。

超长阵列式位移计在土石坝监测中的应用

阵列式位移计作为新型监测仪器,具有自动实时采集、3D测量、精度高、运输储存方便、安装灵活、易于实现远程监测等优点。笔者介绍了阵列式位移计的工作原理及其在新疆某土石坝监测中的应用案例,监测结果表明阵列式位移计在土石坝沉降变形监测中应用效果良好,具有广阔的应用前景。

旺隆水库泥岩心墙坝施工期安全监测数据分析

泥岩是西南地区的典型岩层,为了确保旺隆水库泥岩心墙坝施工安全,根据泥岩防渗心墙结构特征,在坝顶和坝内布置检测点,监控大坝的水平位移、垂直沉降及渗流渗压等特征值及发展规律。安全监测数据分析表明:坝体内、外各测点的监测量及其月变化速率均较小,均在正常范围内;坝基渗透压力测值变化平稳,无突变等不利情况,大坝安全性态正常稳定。分析成果验证了防渗心墙泥岩掺配比等指标准确可靠,可为大坝填筑施工提供重要的技术指导。

广州市梅州水库土坝险情原因分析与加固处理

2012年,广州市梅州水库水位降到死水位以下,降水过程中土坝出现较为严重的病害现象,主坝上游混凝土护坡发现错缝沉降和折断裂缝,坝顶混凝土路面沿坝轴线的结构缝张开。经分析认为,坝体土质松散不均匀,大坝清基不彻底存在软土层,左坝段不利的地形地质条件等是险情发生的内部因素,在库水位持续下降至建库以来最低水位这一外部因素作用下诱发了险情。在最新勘测成果基础上对土坝上游坝坡进行抗滑稳定分析,发现各种工况下安全系数均大于1,但在库水位非常降落条件下,左坝段上游坝坡的抗滑稳定安全系数小于规范要求最小值1.20,因此,在坝脚新设一反压平台使得坝坡抗滑最小安全系数为1.22,并对坝顶裂缝进行开挖回填处理。