Stress-strain analysis of Aikou rockfill dam with asphalt-concrete core

Aikou rockfill dam with asphalt-concrete core is situated in a karst area in Chongqing City, China. In order to study the operative conditions of the rockfill dam, especially those of the asphalt-concrete core, the Duncan model is adopted to compute the stress and strain of both the rockfill dam and the asphalt-concrete core after karst grouting and other treatments. The results indicate that the complicated stress and deformation of both the dam body and the core are within reasonable ranges. It is shown that structure design and foundation treatment of the dam are feasible and can be used as a reference for other similar projects.

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.

Real-Time Spreading Thickness Monitoring of High-core Rockfill Dam Based on K-nearest Neighbor Algorithm

During the storehouse surface rolling construction of a core rockfilldam, the spreading thickness of dam face is an important factor that affects the construction quality of the dam storehouse' rolling surface and the overallquality of the entire dam. Currently, the method used to monitor and controlspreading thickness during the dam construction process is artificialsampling check after spreading, which makes it difficult to monitor the entire dam storehouse surface. In this paper, we present an in-depth study based on real-time monitoring and controltheory of storehouse surface rolling construction and obtain the rolling compaction thickness by analyzing the construction track of the rolling machine. Comparatively, the traditionalmethod can only analyze the rolling thickness of the dam storehouse surface after it has been compacted and cannot determine the thickness of the dam storehouse surface in realtime. To solve these problems, our system monitors the construction progress of the leveling machine and employs a real-time spreading thickness monitoring modelbased on the K-nearest neighbor algorithm. Taking the LHK core rockfilldam in Southwest China as an example, we performed real-time monitoring for the spreading thickness and conducted real-time interactive queries regarding the spreading thickness. This approach provides a new method for controlling the spreading thickness of the core rockfilldam storehouse surface.

Research on the Seepage Safety Monitoring Indexes of the High Core Rockfill Dam

The study on developing the reasonable safety monitoring indexes plays a most importantly role in the health monitoring of high core rockfill dams. However, researches on this topic are relatively scarce both at home and abroad. In this paper, the characteristics and failure modes of seepage in high core rockfill dam are analyzed firstly. Then, a safety monitoring index based on seepage quantity, which reflects the overall seepage behavior, is developed, using the real-time monitoring data and its safety monitoring model. Moreover, another safety monitoring index based on seepage gradient, reflecting the local seepage behavior, is proposed, combining the spatial layout of osmo- meters and local failure mechanisms of core wall. Additionally, one more safety monitoring index based on permeability coefficient, which considers the overall and local seepage behaviors, is developed, on the basis of establishing the finite element analysis model and real-time seepage coefficient inversion analysis model of high core rockfill dam. A case study on these indexes of Nuozhadu high core rockfill dam is developed, which improves the reliability of seepage safety evaluation of the dam.

Theoretical research on construction quality real-time monitoring and system integration of core rockfill dam

With the enlargement of core rockfill dam construction scale and the improvement of construction mechanization level, the traditional manual construction quality control method is now difficult to meet the quality and safety demands of modern dam construction, so automatic and real-time dam construction quality monitoring with high-techs is urgently needed. The paper makes theoretical research on construction quality real-time monitoring and system integration of core rockfill dam, proposes implementation method and integrated solution of construction quality real-time monitoring of core rockfill dam construction process, realizes refining, all-whether, entire-process and real-time control and analysis on key links of dam construction, and introduces the application of the construction quality real-time monitoring and system integration technology to a practical core rockfill dam project.

Real-time compaction quality monitoring of high core rockfill dam

The conventional quality control method of core rocldill dam construction exhibit difficulty controlling compaction parameters accurately or ensuring construction quality. This is because it is easily influenced by human behavior or lack of adequate management. We therefore establish the timely monitoring indexes and control criteria of compaction processes by considering the characteristics and quality requirements of high core rockffll dam construction. Based on the established indexes and criteria, integrating GPS, GPRS and PDA technologies, a real-time compaction quality monitoring method is proposed. The relevant key techniques are proposed as well, including automatic collection of information and a graphic algorithm for rolling-process visualization. By the proposed method and techniques, a real-time monitoring system is provided to realize the precise automatic online entire-process monitoring of compaction parameters, including compaction pass, rolling trajectory, nmning speed of roller, vibration status and rolled pavement thickness. The application of the Nuozhadu project shows that the proposed system can control compaction parameters effectively and ensure better construction quality. Therefore, it might become a new way towards construction quality control of high core rockfill dam.

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。

鸭寨水库料场爆破方案设计及评价

结合工程实例,对鸭寨水库工程的坝体石方料开采以及爆破方案进行简要阐述。鸭寨水库沥青心墙土石坝工程区位于贵州省三都县,坝体石料开采条件较差。为满足施工工期,提高工程施工进度和施工效率,根据钻孔揭露地层岩性,采用浅孔与中深孔爆破法相结合的爆破方案,自上而下、分层台阶式施工。通过爆破效果原因分析以及对爆破参数和措施进行改进,有效解决了爆破石料级配不连续的问题。总结和积累的相关施工经验,对推动原岩节理和软弱夹层岩体爆破技术管控措施的改进、土石坝料场等类似工程的爆破方案设计具有一定借鉴意义。

考虑压实质量和改进本构的沥青心墙坝性态分析

针对邓肯-张模型对沥青混凝土心墙料力学性质描述偏离的不足,改进了心墙沥青混凝土本构模型;同时,考虑实际施工中各分区坝料压实质量空间差异导致的物理力学特性空间差异,提出了考虑坝料实际压实质量的大坝有限元分析方法。首先,通过数字大坝系统采集到的施工数据,对大坝各坝料分区进行压实质量空间估计;其次,建立各坝料分区本构模型参数与压实质量的定量关系,实现对任意单元材料参数的空间估计,并通过Abaqus软件的二次开发,实现坝料本构模型参数的每个单元赋值;最后,结合工程实例,对沥青混凝土心墙堆石坝施工期结构性态进行精细数值分析。结果表明,考虑坝料实际压实质量的数值模拟可以更好地反映大坝实际施工过程的应力变形情况;改进后的本构模型提高了心墙变形计算的准确性,为精确分析沥青混凝土心墙堆石坝结构安全提供了有效途径。

高心墙堆石坝接触黏土与岸坡接触特性的离心模型研究

为了提高砾石土心墙与岸坡之间的变形协调性,高心墙堆石坝通常在心墙与岸坡之间设置高塑性黏土,统称为接触黏土,接触黏土的变形特性对高心墙的应力变形性状和心墙的安全性有重大影响。开展了4组接触黏土与岸坡接触面的局部离心模型试验,通过调整施加的上覆荷载大小来探讨原型坝体不同高程处的接触面剪切位移发展规律。基于理论分析,提出了一个计算接触黏土与岸坡接触面离心模型试验中边界效应影响范围的解析表达式,以确定接触面离心试验中试验模型的相似比尺。试验结果表明:在原型坝体的不同高程处,接触黏土与岸坡之间均会产生一定的剪切位移,但不会出现分离现象;接触黏土和砾质心墙土变形主要以竖向下沉为主,并且接触黏土与砾质心墙土之间的沉降等值线变化较为连续,未出现陡变情况,这说明接触黏土起到了很好地协调变形的作用,因此在进行高心墙堆石坝的结构安全性分析过程中应考虑接触黏土与岸坡的接触效应。

考虑坝基防渗体渗透溶蚀效应的特高土心墙堆石坝服役年限可靠性分析

特高土心墙堆石坝坝基防渗体非均质特征显著,影响渗透溶蚀效应下长期服役性能的准确评估。本文基于KL展开法离散了水泥基材料参数随机场,构建了水泥基材料渗流-溶蚀耦合随机模型,利用神经网络,建立了随机场与服役年限的映射关系,发展了服役年限可靠性分析方法。以长河坝工程为背景,研究了坝基防渗体渗透系数、孔隙率和固相钙浓度为随机场情况下特高土心墙堆石坝的渗流与溶蚀特征,并对特高土心墙堆石坝服役年限进行了可靠性分析。渗透溶蚀效应会增大坝基防渗体渗透系数的空间变异性;坝基防渗体渗透系数、孔隙率和固相钙浓度为随机场情况下坝体与坝基总单宽渗流量是均质情况下的0.87~1.19倍;坝基防渗体95%保证率的服役年限为63.4 a;降低主防渗帷幕区与固结灌浆区渗透系数均值、减小固结灌浆区渗透系数空间变异性,是延长服役年限较为有效的方法。特高土心墙堆石坝设计、施工、运行与维护过程中应重视渗透溶蚀效应下坝基防渗体的空间变异性。

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LHS-ISSA-SVR的心墙堆石坝渗流参数反演方法及应用

高效合理地确定大坝的渗流参数是科学分析大坝渗流性态的关键。针对心墙堆石坝复杂多渗流参数反演问题,提出了一种基于LHS-ISSA-SVR组合代理模型的心墙堆石坝渗流参数反演新方法。基于饱和—非饱和渗流理论,建立了心墙堆石坝渗流有限元模型,采用拉丁超立方抽样(LHS)获取均匀性更优的渗透系数组合样本集,并代入有限元模型模拟监测点水头,通过支持向量回归机(SVR)准确建立监测点水头与材料渗流参数的映射关系。融合佳点集、莱维飞行与柯西反向学习策略改进麻雀搜索算法(SSA),基于改进的麻雀搜索算法实现了SVR模型参数的优化调整和渗流参数的智能反演。工程实例应用表明,各监测点渗压水头反演值与实测值相对误差均在2.5%内,心墙堆石坝渗流场位势分布规律合理,渗流参数反演结果准确可靠。该方法为准确反演长期服役的心墙堆石坝渗流参数提供了新途径。

基于ABAQUS的心墙堆石坝湿化流变耦合数值模拟方法

针对库水作用下心墙堆石坝湿化与流变耦合影响下的坝体变形问题,结合邓肯—张E-B模型、修正沈珠江湿化模型和沈珠江三参数流变模型,提出了湿化流变耦合计算模型,同时基于ABAQUS平台子程序开发,实现了考虑坝体堆石料湿化流变耦合分析,并进行了相应的验证及坝高从100~300 m的敏感性分析。结果表明,耦合作用下的上游堆石体沉降量较非耦合作用下增加约12%~16%,向上游位移减小约5%~10%,且耦合作用对坝体变形的影响随坝高增大而愈发显著。该研究可更为准确地考虑湿化与流变耦合作用下的坝体变形,对心墙堆石坝的设计、施工具有现实的理论意义和应用价值。

考虑岩土特性的心墙堆石坝坝基廊道断面优选方法

基于大型有限元软件ANSYS平台,采用APDL语言编写参数化控制的邓肯-张E-B模型计算程序模块,制定堆石坝结构计算流程,并通过具体算例验证程序的正确性,在此基础上对某在建水电站心墙堆石坝坝基廊道进行三维线性和非线性有限元分析,优选廊道断面型式。结果表明:在大型有限元软件平台上进行邓肯-张E-B本构模型的二次开发是可行的;外围岩土的材料特性对廊道受力状态影响很大;不同底板衬砌厚度对廊道应力的影响较大,随着底板厚度的增加,廊道底板表面最大拉应力数值逐渐减小,而拱顶内侧拉应力则呈现先减小后增大的趋势,综合廊道变形、应力、破坏区域及经济性来看,推荐采用城门洞形断面,同时底板厚度1.8 m~2.0 m。该方法通用性强,操作简便。

坝基廊道开裂对心墙坝渗流特性的影响

以某110 m高的沥青混凝土心墙堆石坝为例,采用有限元数值模拟方法对大坝开展三维渗流分析,研究心墙底部廊道出现不同深度、长度以及位置的裂缝对大坝渗流特性的影响。结果表明:廊道浅表裂缝对大坝渗流场基本无影响,但当廊道顶部出现贯穿性裂缝时,附近区域渗流场的分布规律显著改变,且渗流量加大;而廊道底部贯穿性裂缝对渗流量影响相对较小;当廊道产生多条贯穿性裂缝时,渗漏量增加明显,同时会引起上游侧地层和过渡Ⅰ区渗透坡降的增大,需引起重视。

深厚覆盖层上沥青心墙堆石坝智能建设关键技术研究及应用

当前众多沥青心墙堆石坝建设于深厚覆盖层上,给工程建设与运行安全带来了较大考验。针对该问题,本文基于大坝智能建设理念,以巴塘沥青混凝土心墙坝为主要研究对象,构建了深厚覆盖层上沥青心墙堆石坝智能建设体系,实现了振冲桩施工、防渗墙施工、沥青混凝土温度控制及大坝填筑全过程监控,构建了巴塘水电站坝体-坝基施工质量全方位智能监控体系,提升了施工过程管控水平。

黏土心墙堆石坝防渗土料掺配加工技术研究

针对土石坝项目因周边环境、水文地质不良以及征地问题造成的土料场料源储量少、质量不合格等问题,笔者以广西蒙山古皂水库为例,分析土料加工控制原理,研究土料开采、加工、运输等环节的控制措施,总结出控制黏土心墙堆石坝防渗土料质量优化的施工技术,提出适用于该项目的防渗土料掺配加工工艺。结果表明:所提出的工艺将土料生产效率从600 m3/d提高到850 m3/d,效率提高了41.67%;大坝心墙填筑工期由原计划的12个月缩减至9个月。研究成果可为土石坝土料加工提供参考。

库水骤升条件下特高心墙堆石坝渗流及坝坡稳定性分析

为分析库水骤升对特高心墙堆石坝的渗流特性及坝坡稳定性的影响,以某特高心墙堆石坝实际情况为例,建立有限元分析模型,采用饱和-非饱和非稳定渗流理论,对库水骤升阶段渗流场进行了数值模拟,并将非稳定渗流场与极限平衡法相结合分析了坝坡稳定性。研究结果表明:库水骤升过程中,心墙内浸润线变化相对库水位变化表现出明显的滞后性,浸润线呈现“下凹”形状,且水位骤升速率越快,向下弯的程度也越大;库水骤升阶段,心墙内非稳定渗流等势线整体向上游偏移;库水骤升对上游坝坡稳定性具有有利影响,下游坝坡由于心墙较好的防渗性,基本保持不变。

黏土心墙堆石坝填筑受力特性有限元数值分析

笔者以蒙山县古皂水库黏土心墙堆石坝为例,采用岩土工程有限元软件Plaxis 3D对大坝填筑过程进行数值模拟分析,研究在掺入膨润土和不同碾压方式等工况下大坝变形和内力变化规律。结果表明:1)随着掺入膨润土及增加碾压遍数,大坝沉降量有所减小,振碾效果优于静碾效果;2)掺入膨润土对大坝基础灌浆部位变形几乎无影响,碾压方式和碾压遍数对大坝基础灌浆部位的变形及内力变化影响较明显;3)掺入膨润土后采取静碾2遍和动碾6遍的方案进行施工,大坝变形和内力变化均处于可控范围内,此方案是较为合理的。研究成果可为大坝填筑施工提供理论依据。