A new classification of seepage control mechanisms in geotechnical engineering

Seepage flow through soils,rocks and geotechnical structures has a great influence on their stabilities and performances,and seepage control is a critical technological issue in engineering practices.The physical mechanisms associated with various engineering measures for seepage control are investigated from a new perspective within the framework of continuum mechanics;and an equation-based classification of seepage control mechanisms is proposed according to their roles in the mathematical models for seepage flow,including control mechanisms by coupled processes,initial states,boundary conditions and hydraulic properties.The effects of each mechanism on seepage control are illustrated with examples in hydroelectric engineering and radioactive waste disposal,and hence the reasonability of classification is demonstrated.Advice on performance assessment and optimization design of the seepage control systems in geotechnical engineering is provided,and the suggested procedure would serve as a useful guidance for cost-effective control of seepage flow in various engineering practices.

Groundwater flow through fractured rocks and seepage control in geotechnical engineering: Theories and practices

Groundwater flow through fractured rocks has been recognized as an important issue in many geotechnical engineering practices.Several key aspects of fundamental mechanisms,numerical modeling and engineering applications of flow in fractured rocks are discussed.First,the microscopic mechanisms of fluid flow in fractured rocks,especially under the complex conditions of non-Darcian flow,multiphase flow,rock dissolution,and particle transport,have been revealed through a com-bined effort of visualized experiments and theoretical analysis.Then,laboratory and field methods of characterizing hydraulic properties(e.g.intrinsic permeability,inertial permeability,and unsaturated flow parameters)of fractured rocks in different flow regimes have been proposed.Subsequently,high-performance numerical simulation approaches for large-scale modeling of groundwater flow in frac-tured rocks and aquifers have been developed.Numerical procedures for optimization design of seepage control systems in various settings have also been proposed.Mechanisms of coupled hydro-mechanical processes and control of flow-induced deformation have been discussed.Finally,three case studies are presented to illustrate the applications of the improved theoretical understanding,characterization methods,modeling approaches,and seepage and deformation control strategies to geotechnical engi-neering projects.

STUDY ON COUPLING MODEL OF (SEEPAGE-FIELD) AND STRESS-FIELD FOR ROLLED CONTROL CONCRETE DAM

Based on the construction interfaces in rolled control concrete dam(RCCD), the methods were proposed to calculate the influence thickness of construction interfaces and the corresponding physical mechanics parameters. The principle on establishing the coupling model of seepage_field and stress_field for RCCD was presented. A 3_D Finite Element Method(FEM) program was developed. Study shows that such parameters as the thickness of construction interfaces,the elastic ratio and the (Poisson's) ratio obtained by tests and theoretical analysis are more reasonable, the coupling model of seepage_field and stress_field for RCCD may indicate the coupling effect between the two fields scientifically, and the developed 3_D FEM program can reflect the effect of the construction interfaces more adequately. According to the study, many scientific opinions are given both to analyze the influence of the construction interfaces to the (dam's) characteristic, and to reveal the interaction between the stress_field and the seepage_field.

Study on Seepage Control in Complicated Hydrogeological Conditions on the Right Bank of JinPing-I Hydropower Station

With consideration of the special hydrogeological conditions and layout characteristics of the hydraulic structures, the seepage control measures of dam abutment and underground powerhouse on the right bank of JinPing-I hydropower station is drawn up. Based on the three dimensional finite element analysis of seepage control with dry area virtual flow constant mesh analysis method, the rationality of the seepage control measures of dam abutment and underground powerhouse has been verified and the key factors affecting the effect of seepage have been compared. In combination with the curtain of dam abutment, the curtain of underground powerhouse is reasonable. The results showed that the steel liner of penstock after the curtain is necessary.

Comparative Analysis of Tunnel Seepage Field under Different Waterproof and Drainage System Using Analytical Methods

Tunnel seepage is an important factor affecting the progress and safety of tunnel construction. In this paper, the mining method tunnel construction in the water-rich weathered granite stratum is taken as the research object. Through the analytical calculation method, the distribution law of tunnel seepage field under different waterproof and drainage types is studied, and the comparative analysis is carried out. According to the analytical solution, the influencing factors of grouting parameters are proposed. The sensitivity of the tunnel seepage field to the variation of grouting parameters is analyzed. A novel waterproof and drainage system, and construction technology suitable for subway tunnels with large buried depth below groundwater level were proposed.

An integrated self-healing algorithm for resilient packet ring

Resilient Packet Ring (RPR) is a Media Access Control (MAC) layer protocol that operates over a double counter-rotating ring network topology. RPR is designed to enhance Synchronous Digital Hierarchy(SDH) in order to handle data traffic more efficiently. Since Intelligent Protection Switching(IPS) is one of the key technologies in ring networks, RPR provides two intelligent protection algorithms: steering and wrapping. While wrapping in RPR in essence inherits the automatic protection switching(APS) algorithm of SDH, it also wastes the bandwidth on the wrapping ringlets and may result in severe congestion. Whereas steering in RPR provides high bandwidth utilization, its switching speed is low, because it is indeed a high layer's restoration algorithm. In this paper, integrated self-healing(ISH) algorithm as an effective algorithm for RPR is proposed, which synthesizes the merits of the two algorithms by transporting healing signal and computing routing in MAC layer. At last, the performance of ISH algorithm is analyzed and simulated.

Study of the Seepage Mechanism in Thick Heterogeneous Gas Reservoirs

The seepage mechanism plays a crucial role in low-permeability gas reservoirs.Compared with conventional gas reservoirs,low-permeability sandstone gas reservoirs are characterized by low porosity,low permeability,strong heterogeneity,and high water saturation.Moreover,their percolation mechanisms are more complex.The present work describes a series of experiments conducted considering low-permeability sandstone cores under pressuredepletion conditions(from the Xihu Depression in the East China Sea Basin).It is shown that the threshold pressure gradient of a low-permeability gas reservoir in thick layers is positively correlated with water saturation and negatively correlated with permeability and porosity.The reservoir stress sensitivity is related to permeability and rock composition.Stress sensitivity is generally low when permeability is high or in the early stage of gas reservoir development.It is also shown that in sand conglomerates,especially the more sparsely filled parts,the interstitial materials among the conglomerates can be rapidly dislodged from the skeleton particles under stress.This material can therefore disperse,migrate,and block the pore throat producing serious,stress-sensitive damage.

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.

水电工程深厚覆盖层地基防渗设计与潜蚀问题

我国西部一些水电站的坝址存在超深厚覆盖层,给工程的渗流控制和设计带来巨大的困难。垂直防渗墙是深厚覆盖层地基渗流控制最常用的措施。通过回顾泸定水电站深厚覆盖层悬挂式防渗墙地基异常渗漏治理的案例,指出对于西部河流中广泛存在的不稳定砂砾石地层,在关注渗流出口保护的同时,还应重视地基内部高流速和高水力梯度区域的潜蚀风险。为定量评价砂砾石地基内部潜蚀及其导致的后果,应开展深厚覆盖层内部稳定性评价准则、高上覆压力下砂砾石潜蚀试验技术、潜蚀数值模拟方法及潜蚀本构模型等关键技术问题的研究。

中高渗储层乳状液注入参数优化设计方法研究

乳状液作为一种新型的调驱体系,可以通过在多孔介质中的贾敏效应发挥流度控制作用,抑制驱油体系的窜进。在实施乳状液调驱时,不但要考虑体系的调堵能力,同时还需要综合考虑体系的注入性能。乳状液渗流不同于传统的牛顿流体渗流,其在多孔介质中的渗流压力不但受到自身黏度的影响,同时还受到吸附、滞留等作用的影响。本文基于乳状液的等效流动黏度建立了注入压力预测模型,采用Matlab编程软件定量计算了不同注入参数和注入方式下的流动阻力,该计算方法可以根据现场注采设备的基本性能,优选出复合体系的注入速度与注入量,在保证复合体系具有良好的调驱能力下还有良好的注入性,本研究为现场乳状液调驱施工提供了一种可行的定量设计方法。

广东某高速公路隧道衬砌混凝土腐蚀成因与规律研究

长期处于侵蚀性水环境中所引起的化学侵蚀是公路隧道混凝土的常见病害之一。这种侵蚀会导致混凝土耐久性下降,进而对隧道结构安全构成威胁并需要大量资金进行养护。然而,现有研究普遍缺乏工程实例依托,试验和模拟参数设置与工程实际的关联性较弱,难以准确、全面地反映现实中复杂侵蚀水环境下混凝土腐蚀的机制。为此,选取我国广东某高速公路隧道为工程实例,采用原位和实验室水化学指标测试、XRF测试手段确定混凝土化学侵蚀来源,并以隧道地下水渗流模拟试验复现化学侵蚀过程,研究混凝土的腐蚀成因、化学侵蚀规律和控制因素。结果表明:(1)隧道衬砌混凝土与低Ca^(2+)、高HCO_(3)^(-)浓度的地下水接触、混合后发生钙溶蚀,形成了高pH值、高饱和的CaCO_(3)溶液及过饱和沉淀,并在地下水经裂隙快速喷出进入隧道的过程中,CO_(2)分压下降促使CaCO_(3)进一步过饱和析出;(2)在隧道衬砌混凝土钙溶蚀初期,混凝土液相Ca(OH)_(2)与地下水Ca^(2+)浓度差较大,钙溶蚀速率较快,而随着钙溶蚀的进行,固相Ca(OH)_(2)持续被消耗且隧道排水中Ca^(2+)浓度持续升高,与地下水中Ca^(2+)浓度差缩小,钙溶蚀速率趋缓,最终在动水条件下达到动态平衡,隧道排水水化学特征维持相对稳定;(3)低Ca^(2+)、高HCO_(3)^(-)浓度的地下水有利于混凝土的钙溶蚀和CaCO_(3)过饱和析出沉淀,而过高或过低的地下水渗流流速(固液停留时间)均不利于相关化学反应的进行。

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。

临水强透水地层船闸基坑帷幕防渗与管井降水措施研究

临水强透水地层总是伴随着高地下水的特点,对于该地层的基坑施工易造成许多危害和不利影响,因此需要采用帷幕和管井的防渗降水措施,目前对于帷幕和管井的防渗降水效果的评价方式仍处于探索阶段。利用ABAQUS有限元计算软件,分别对帷幕和管井作用下的基坑渗流特征进行研究,采用单宽渗流量、帷幕降水深度、边坡水位作为帷幕防渗效果的评价标准,采用管井流量和边坡水位作为管井降水效果的评价标准,对帷幕深度和帷幕距基坑的距离以及管井深度、管井间距和管井半径进行敏感性分析,并对帷幕管井共同作用下帷幕和管井的防渗降水效果进行分析,为船闸基坑工程中帷幕和管井的布置方案提供设计依据。

FINITE ELEMENT NUMERICAL SIMULATION OF THREE-DIMENSIONAL SEEPAGE CONTROL FOR DEEP FOUNDATION PIT DEWATERING

For deep foundation pit dewatering in the Yangtze River Delta, it is easy to make a dramatic decrease of the underground water level surrounding the dewatering area and cause land subsidence and geologic disasters. In this work, a three-dimensional finite element simulation method was applied in the forth subway of Dongjiadu tunnel repair foundation pit dewatering in Shanghai. In order to control the decrease of the underground water level around the foundation pit, the foundation pit dewatering method was used to design the optimization project of dewatering ,which was simulated under these conditions that the aquifers deposited layer by layer, the bottom of the aquifers went deep to 144.45 m, the retaining wall of foundation pit shield went deep to 65 m, the filters of the extraction wells were located between 44 m to 59 m, the water level in the deep foundation pit was decreased by 34 m, and the maximum decrease of water level outside the foundation pit was 3 m. It is shown that the optimization project and the practical case are consistent with each other. Accordingly, the three-dimensional finite element numerical simulation is the basic theory of optimization design of engineering structures of dewatering in deep foundation pit in such areas.

NEW METHOD OF SIMULATING CONCENTRATED DRAIN HOLES IN SEEPAGE CONTROL ANALYSIS

In this paper, based upon the basic solution of sink, the approximate solution of single drain hole in finite elements is derived by use of the superposition principle. Then, the theoretical solution is extended to the case of some drain holes in one finite element, and the method is used in seepage control analysis with quick convergence and high accuracy. On the other hand, if the positions of the drain holes are changed, only some control factors of drain holes are changed, but the finite element grid need not to be reformed. Therefore, the method is more suitable in optimal research of seepage control.

THE UNITED METHOD FOR THE CALCULATION OF SEEPAGE CONTROL BY ADOPTING WEIGHTING SOIL LAYER ON THE BACK SIDE OF DIKE

Constructing a weighting soil layer at the downstream toe of dike on layered ground is an effective measure to prevent the foundation from blowout failures. In this paper, a series of differential equations describing the seepage flow in layered dike foundation were established, and a united method combining analytic method with one-dimensional finite difference method was proposed for solving the equations. The case study shows that the results calculated by the united method are considerably identical to the computational results of Finite Element Method (FEM), and the united method is very simple and easy compared to the FEM.

Towards an optimization design of seepage control：A case study in dam engineering

High dams generally suffer from higher seepage risks in their foundations, and seepage control is an important technology for limiting the amount of leakage and improving the stability of the foundations. In this study, a procedure was proposed for optimization design of seepage control system in large-scale hydropower projects, which relies on sufficient characterization of site conditions and proper quantification of the performance of the seepage control system. The proposed procedure was applied to the design of seepage control system in the Mengdigou Hydropower Station consisting of a double-curvature arch dam201 m in height. An optimized layout of the seepage control system, including the extended length of grout curtain, the rows of grouting holes and the spacing of drainage holes, was suggested. The proposed procedure provides a guide with lower risk and higher confidence for performance assessment and optimization design of seepage control systems in high dam engineering.

防渗体系破损条件下混凝土面板堆石坝的渗流分析

在分析总结多座高混凝土面板堆石坝面板开裂特征的基础上,结合某高混凝土面板堆石坝工程,将局部防渗体系单元作为破损模拟对象,基于等效均质渗透系数法,利用Midas GTS开展了不同破损部位和破损程度条件下大坝的渗流场分析,并研究了垫层和过渡层是否发生破损对大坝渗流性态的影响。通过对大坝渗流量、浸润线形态等方面的分析,研究结果表明:相同的混凝土面板破损部位条件下,破损程度是影响大坝渗流性态的重要因素;当面板破损程度相同,垫层和过渡层未破损时,其防渗能力仍起到关键作用,大坝渗流场变化不明显;当整个防渗体系均发生严重破损时,大坝渗流性态恶化,渗透安全性明显降低。

新时代背景下课程思政要素解析及实践路径探究——以渠道防渗工程技术课程为例

新时代水利人才高质量发展背景下,对专业课程教师探讨知识传授与思政引领间关系提出新要求,实现专业课程与思想政治理论课的同向同行和协同育人。渠道防渗工程技术课程专业性及目的性强,知识串联与课程思政引领结合待突破。该文以渠道防渗工程技术课程为例,解析课程思政的潜在价值,明晰课程思政教学目标,深入重点挖掘其蕴含的思政要素,探究课程思政融入关键路径,以期实现教学与育人的有机结合,更好地落实立德树人根本任务。

某化工园区地下水污染迁移及控制数值模拟研究

某化工园区潜水中氟化物超标,为控制受污染地下水扩散,沿下游河堤修建防渗帷幕。通过分析研究区水文地质条件,应用FEFLOW 7.0建立地下水数值模型,预测防渗帷幕修建前后受污染地下水迁移情况,并评估防渗帷幕污染控制效果。结果表明:化工园区受污染地下水在以粉砂、粉细砂等岩性为主的潜水含水层中迁移速度快,第200天时污染物对源强附近及下游大片范围地下水造成污染;在污染源下游沿堤修建防渗帷幕短期虽可有效阻断污染物持续迁移,但会导致污染物在帷幕前端聚集,一段时间后地下水污染羽会绕过防渗帷幕发生渗流污染,须配合其他治理措施综合控制地下水污染。