DOCSLIB.ORG

Hazard Classification and Hydraulic Remediation Options for Flat- Topped and Ogee-Crested Low-Head Dams

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Hazard Classification and Hydraulic Remediation Options for Flat- Topped and Ogee-Crested Low-Head Dams View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by DigitalCommons@USU Utah State University DigitalCommons@USU All Graduate Theses and Dissertations Graduate Studies 5-2013 Hazard Classification and Hydraulic Remediation Options for Flat- Topped and Ogee-Crested Low-Head Dams Riley J. Olsen Utah State University Follow this and additional works at: https://digitalcommons.usu.edu/etd Part of the Civil Engineering Commons Recommended Citation Olsen, Riley J., "Hazard Classification and Hydraulic Remediation Options for Flat-Topped and Ogee- Crested Low-Head Dams" (2013). All Graduate Theses and Dissertations. 1538. https://digitalcommons.usu.edu/etd/1538 This Thesis is brought to you for free and open access by the Graduate Studies at DigitalCommons@USU. It has been accepted for inclusion in All Graduate Theses and Dissertations by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. i HAZARD CLASSIFICATION AND HYDRAULIC REMEDIATION OPTIONS FOR FLAT-TOPPED AND OGEE-CRESTED LOW-HEAD DAMS by Riley J. Olsen A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in Civil and Environmental Engineering Approved: ________________________________ ________________________________ Michael C. Johnson Steven L. Barfuss Major Professor Committee Member ________________________________ ________________________________ Joseph A. Caliendo Mark R. McLellan Committee Member Vice President for Research and Dean of the School of Graduate Studies UTAH STATE UNIVERSITY Logan, Utah 2013 ii Copyright © Utah State University 2013 All Rights Reserved iii ABSTRACT Hazard Classification and Hydraulic Remediation Options for Flat-Topped and Ogee-Crested Low-Head Dams by Riley J. Olsen, Master of Science Utah State University, 2013 Major Professor: Dr. Michael C. Johnson Department: Civil and Environmental Engineering The dangerous hydraulic conditions that can form downstream of a low-head dam were investigated. These dangerous hydraulic conditions have been the cause of hundreds of drowning incidents since the construction of the first low-head dams. Two primary objectives were identified for this study, each of which were primarily performed using the Computational Fluid Dynamics software, Flow-3D ®, with physical models used to verify the numerical results. The first objective was the identification of a risk factor made up of easily measured parameters that could accurately predict when the dangerous hydraulic conditions are present at a low-head dam. The risk factor that was found to achieve this objective was calculated as (h u – hd)/P , where hu and hd are the upstream and downstream water depths, respectively, and P is the dam height. For the flat-topped dams tested, the dangerous condition was present within the range of risk factors from 0.343 to 0.708. For the ogee-crested dams tested, the dangerous conditions were present between risk factors of 0.093 and 0.798. The second objective was to identify possible remediation options that would be capable of eliminating the dangerous hydraulic iv conditions, therefore reducing risk to the public. It was also desired to keep the options easily and inexpensively implemented. Two different remediation options were found to this end, and consisted of either upstream facing ramps spaced along the width of the channel below a low-head dam, or spaced platforms protruding from the downsteam face of the dam slightly below its crest. Three different designs of each configuration were tested, with those for the ramp configuration being identified as R1, R2, and R3. The platform designs were identified as P1, P2, and P3. The options were evaluated based on how long it took for human dummies introduced into the flow to pass through the high risk region of the simulations, with the maximum allowed time being 50 seconds. Any test in which a dummy remained in the danger region for longer than 50 seconds was deemed ineffective. The option found to perform the best was the P2 design, which had an overall performance time of about 17.4 seconds. (81 pages) v PUBLIC ABSTRACT Hazard Classification and Hydraulic Remediation Options for Flat-Topped and Ogee-Crested Low-Head Dams by Riley J. Olsen, Master of Science Utah State University, 2013 The dangerous hydraulic conditions that can form downstream of a low-head dam were investigated. These dangerous hydraulic conditions have been the cause of hundreds of drowning incidents since the construction of the first low-head dams. Two primary objectives were identified for this study, each of which were primarily performed using the Computational Fluid Dynamics software, Flow-3D ®, with physical models used to verify the numerical results. The first objective was the identification of a risk factor made up of easily measured parameters that could accurately predict when the dangerous hydraulic conditions are present at a low-head dam. The risk factor that was found to achieve this objective was calculated as (h u – hd)/P , where hu and hd are the upstream and downstream water depths, respectively, and P is the dam height. For the flat-topped dams tested, the dangerous condition was present within the range of risk factors from 0.343 to 0.708. For the ogee-crested dams tested, the dangerous conditions were present between risk factors of 0.093 and 0.798. The second objective was to identify possible solutions to the danger created by low-head dams, therefore reducing risk to the public. It was also desired to keep the options easily and inexpensively implemented. Two different solutions were found to this end, and consisted of either upstream facing ramps vi spaced along the width of the channel below a low-head dam, or spaced platforms protruding from the downsteam face of the dam slightly below its crest. Three different designs of each of these configurations were tested. The options were evaluated based on how long it took for human dummies introduced into the flow to pass through the high risk region of the simulations, with the maximum allowed time being 50 seconds. Any test in which a dummy remained in the danger region for longer than 50 seconds was deemed ineffective. The option found to perform the best was the P2 design, which had an overall performance time of about 17.4 seconds. vii ACKNOWLEDGMENTS I am very grateful for the many people who have aided in the process of this research. I would like to thank the Utah Water Research Laboratory for the financial support and facilities in which I was able to perform the research. I would also like to thank my major professor, Dr. Michael C. Johnson, for allowing me to perform the research and gain first-hand experience with hydraulics problems that will aid me in my professional career. I would also like to thank my other committee members, Steven L. Barfuss and Dr. Joseph A. Caliendo, for all of the support and guidance they provided during the entire process. I would also like to give special thanks to my friends and family, who have not only supported me while working on this project, but also throughout my entire school career. They have been a major influence on this project, and without them I would not be the person I am today and would not be completing the requirements for a master’s degree. Riley J. Olsen viii CONTENTS Page ABSTRACT ....................................................................................................................... iii PUBLIC ABSTRACT .........................................................................................................v ACKNOWLEDGMENTS ................................................................................................ vii LIST OF TABLES ...............................................................................................................x LIST OF FIGURES ........................................................................................................... xi NOTATIONS .................................................................................................................... xii CHAPTER I. INTRODUCTION .............................................................................................1 II. BACKGROUND AND LITERATURE REVIEW ...........................................5 Hydraulic Background .....................................................................5 Statistics .........................................................................................10 Studies ............................................................................................13 Flow-3D ® Theoretical Background ...............................................19 III. HAZARD CLASSIFICATION AT LOW-HEAD DAMS ..............................22 Abstract ..........................................................................................22 Introduction ....................................................................................22 Background ....................................................................................24 Experimental Procedure .................................................................27 Results ............................................................................................35 Discussion ......................................................................................38 Conclusion .....................................................................................40 Revised Data ..................................................................................41
Load more

Recommended publications
  • Hydrogeology
    Hydrogeology Principles of Groundwater Flow Lecture 3 1 Hydrostatic pressure The total force acting at the bottom of the prism with area A is Dividing both sides by the area, A ,of the prism 1 2 Hydrostatic Pressure Top of the atmosphere Thus a positive suction corresponds to a negative gage pressure. The dimensions of pressure are F/L2, that is Newton per square meter or pascal (Pa), kiloNewton per square meter or kilopascal (kPa) in SI units Point A is in the saturated zone and the gage pressure is positive. Point B is in the unsaturated zone and the gage pressure is negative. This negative pressure is referred to as a suction or tension. 3 Hydraulic Head The law of hydrostatics states that pressure p can be expressed in terms of height of liquid h measured from the water table (assuming that groundwater is at rest or moving horizontally). This height is called the pressure head: For point A the quantity h is positive whereas it is negative for point B. h = Pf /ϒf = Pf /ρg If the medium is saturated, pore pressure, p, can be measured by the pressure head, h = pf /γf in a piezometer, a nonflowing well. The difference between the altitude of the well, H, and the depth to the water inside the well is the total head, h , at the well. i 2 4 Energy in Groundwater • Groundwater possess mechanical energy in the form of kinetic energy, gravitational potential energy and energy of fluid pressure. • Because the amount of energy vary from place-­­to-­­place, groundwater is forced to move from one region to another in order to neutralize the energy differences.
    [Show full text]
  • CPT-Geoenviron-Guide-2Nd-Edition
    Engineering Units Multiples Micro (P) = 10-6 Milli (m) = 10-3 Kilo (k) = 10+3 Mega (M) = 10+6 Imperial Units SI Units Length feet (ft) meter (m) Area square feet (ft2) square meter (m2) Force pounds (p) Newton (N) Pressure/Stress pounds/foot2 (psf) Pascal (Pa) = (N/m2) Multiple Units Length inches (in) millimeter (mm) Area square feet (ft2) square millimeter (mm2) Force ton (t) kilonewton (kN) Pressure/Stress pounds/inch2 (psi) kilonewton/meter2 kPa) tons/foot2 (tsf) meganewton/meter2 (MPa) Conversion Factors Force: 1 ton = 9.8 kN 1 kg = 9.8 N Pressure/Stress 1kg/cm2 = 100 kPa = 100 kN/m2 = 1 bar 1 tsf = 96 kPa (~100 kPa = 0.1 MPa) 1 t/m2 ~ 10 kPa 14.5 psi = 100 kPa 2.31 foot of water = 1 psi 1 meter of water = 10 kPa Derived Values from CPT Friction ratio: Rf = (fs/qt) x 100% Corrected cone resistance: qt = qc + u2(1-a) Net cone resistance: qn = qt – Vvo Excess pore pressure: 'u = u2 – u0 Pore pressure ratio: Bq = 'u / qn Normalized excess pore pressure: U = (ut – u0) / (ui – u0) where: ut is the pore pressure at time t in a dissipation test, and ui is the initial pore pressure at the start of the dissipation test Guide to Cone Penetration Testing for Geo-Environmental Engineering By P. K. Robertson and K.L. Cabal (Robertson) Gregg Drilling & Testing, Inc. 2nd Edition December 2008 Gregg Drilling & Testing, Inc. Corporate Headquarters 2726 Walnut Avenue Signal Hill, California 90755 Telephone: (562) 427-6899 Fax: (562) 427-3314 E-mail: [email protected] Website: www.greggdrilling.com The publisher and the author make no warranties or representations of any kind concerning the accuracy or suitability of the information contained in this guide for any purpose and cannot accept any legal responsibility for any errors or omissions that may have been made.
    [Show full text]
  • DETERMINING the LOCATION of HYDRAULIC JUMP by MODEL TEST and HEC-2 FLOW ROUTING/ a Thesis Presented to the Faculty of the Fritz
    L-DETERMINING THE LOCATION OF HYDRAULIC JUMP BY MODEL TEST AND HEC-2 FLOW ROUTING/ A Thesis Presented to The Faculty of the Fritz J. and Dolores H. Russ College of Engineering and Technology Ohio University In Partial Fulment of the Requirement for the Degree Master of Science by Chen-Feng Li, 4 August, 1995 ACKNOWLEDGEMENTS The author gratefdly acknowledges the hanicial support fiom my family, advisor Dr. Chang (Civil Engineering Dept., Ohio University) and Feng Chia University (Taiwan). The author would like to thank the Civil Engineering Department for the help they provided by supplying the various equipment used for my studies. The author also wants to thank those who have helped in my thesis writing. TABLE OF CONTENTS TABLE OF CONTENTS ................................iv LIST OF TABLES ...................................vii LIST OF FIGURES .................................. viii LIST OF SYMBOLS ..................................xii I. INTRODUCTION .................................. 1 I. 1 Background of Study .......................... 1 1.2 Purpose of Study ............................ 2 1.3 Buckingham PI Theorem and Dynamic Simulation ........... 2 1.4 Experiments and Requirements ..................... 3 I .5 The FUTURE Development of the Study ................ 4 I1 . SELECTED LITERATURE REVIEW ..................... 6 11 . 1 Theoretical Development of Hydraulic Jump .............. 6 II.2 Studies of Hydraulic Jump ....................... 6 LI.3 Channel Slope and Hydraulic Jump ................... 8 v 11.4 Length and Location of Hydraulic Jump .................11 II.5 Force and Hydraulic Jump ........................14 II.6 Hydraulic Structures and Hydraulic Jump ................16 II.6.1 Hydraulic Jump in A Stilling Basin ...............17 II.6.2 Sluice Gate and Hydraulic Jump ................17 11.6.3 Sill and Hydraulic Jump ....................19 11.7 Computer Simulation ofHydraulic Jump Surface Profiles ........24 m .
    [Show full text]
  • Characteristics of Undular Hydraulic Jump Downstream of a Sluice Gate
    CHARACTERISTICS OF UNDULAR HYDRAULIC JUMP DOWNSTREAM OF A SLUICE GATE KARAKTERISTIK LONCATAN HIDROLIK UNDULAR DI HILIR PINTU AIR Komang Arya Utama 1), Bambang Yulistiyanto 2), and Budi S. Wignyosukarto 2) 1) Lecturer in Civil Engineering Department, Faculty of Engineering, Gorontalo State University 2) Lecturer in Civil and Environmental Engineering Department, Faculty of Engineering, Gadjah Mada University ABSTRACT Undular hydraulic jump is a hydraulic jump with a low Froude number which is marked by the emergence of a fixed roller. Information about the characteristics of undular hydraulic jump is still very poor. In order for the interests of the development of science, it is necessary to in-depth study of the hydraulic characteristics and phenomenon that appear on the undular hy- draulic jump. This research is applying the 2D physical model that used a tilting flume. Sluice gate is used as a tool to gene- rate the undular hydraulic jump. Measurement of distance and depth using a point gauge while the flow velocity was measu- red using a Nixon Streamflo 422 Currentmeter. Circulation flow is driven by using water pumps with discharge 15 l/s and 30 l/s. The results of this study indicate that the maximum flow velocity of dimensionless velocity distribution are at 0.5 - 0.9. Lowest value of Froude number obtained in running model Q9A1 is Fr1 = 1.197 and its highest value obtained in running mo- del Q3A1 is Fr1 limit = 2.258. The wave steepness is mild with a slope range are 0.1 to 0.3 or 10% to 30%. The length and height of the wave form are reduce at the first, second, third and so on until the condition of conjugate depth (y3).
    [Show full text]
  • Analysis of Turbulent Hydraulic Jump Over a Transitional Rough Bed of a Rectangular Channel: Universal Relations Noor Afzal Aligarh Muslim University, India
    University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Civil Engineering Faculty Publications Civil Engineering 2011 Analysis of Turbulent Hydraulic Jump over a Transitional Rough Bed of a Rectangular Channel: Universal Relations Noor Afzal Aligarh Muslim University, India A. Bushra University of Nebraska-Lincoln Abu Seena Korea Advanced Institute of Science and Technology, Daejeon, Korea Follow this and additional works at: http://digitalcommons.unl.edu/civilengfacpub Part of the Hydraulic Engineering Commons Afzal, Noor; Bushra, A.; and Seena, Abu, "Analysis of Turbulent Hydraulic Jump over a Transitional Rough Bed of a Rectangular Channel: Universal Relations" (2011). Civil Engineering Faculty Publications. 54. http://digitalcommons.unl.edu/civilengfacpub/54 This Article is brought to you for free and open access by the Civil Engineering at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Civil Engineering Faculty Publications by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Published in Journal of Engineering Mechanics 137:12 (2011), pp. 835-845; doi: 10.1061/(ASCE)EM .1943-7889.0000294 Copyright © 2011 American Society of Civil Engineers. Used by permission. Submitted August 9, 2010; approved June 27, 2011; published online June 29, 2011. digitalcommons.unl.edu Analysis of Turbulent Hydraulic Jump over a Transitional Rough Bed of a Rectangular Channel: Universal Relations Noor Afzal,1 A. Bushra,2 and Abu Seena3 1. Visiting Professor, Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea, and Faculty of Engineering, Aligarh Muslim University, Aligarh, India 2. Department of Civil Engineering, University of Nebraska 3. Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea.
    [Show full text]
  • Table of Common Symbols Used in Hydrogeology
    Common Symbols used in GEOL 473/573 A Area [L2] b Saturated thickness of an aquifer [L] d Diameter [L] e void ratio (dimensionless) or e1 is a constant = 2.718281828... f Number of head drops in a flow of net F Force [M L T-2 ] g Acceleration due to gravity [9.81 m/s2] h Hydraulic head [L] (Total hydraulic head; h = ψ + z) ho Initial hydraulic head [L], generally an initial condition or a boundary condition dh/dL Hydraulic gradient [dimensionless] sometimes expressed as i 2 ki Intrinsic permeability [L ] K Hydraulic conductivity [L T-1] -1 Kx, Ky , Kz Hydraulic conductivity in the x, y, or z direction [L T ] L Length from one point to another [L] n Porosity [dimensionless] ne Effective porosity [dimensionless] q Specific discharge [L T-1] (Darcy flux or Darcy velocity) -1 qx, qy, qz Specific discharge in the x, y, or z direction [L T ] Q Flow rate [L3 T-1] (discharge) p Number of stream tubes in a flow of net P Pressure [M L-1T-2] r Radial coordinate [L] rw Radius of well over screened interval [L] Re Reynolds’ number [dimensionless] s Drawdown in an aquifer [L] S Storativity [dimensionless] (Coefficient of storage) -1 Ss Specific storage [L ] Sy Specific yield [dimensionless] t Time [T] T Transmissivity [L2 T-1] or Temperature (degrees) u Theis’ number [dimensionless} or used for fluid pressure (P) in engineering v Pore-water velocity [L T-1] (Average linear velocity) V Volume [L3] 3 VT Total volume of a soil core [L ] 3 Vv Volume voids in a soil core [L ] 3 Vw Volume of water in the voids of a soil core [L ] Vs Volume soilds in a soil
    [Show full text]
  • Darcy's Law and Hydraulic Head
    Darcy’s Law and Hydraulic Head 1. Hydraulic Head hh12− QK= A h L p1 h1 h2 h1 and h2 are hydraulic heads associated with hp2 points 1 and 2. Q The hydraulic head, or z1 total head, is a measure z2 of the potential of the datum water fluid at the measurement point. “Potential of a fluid at a specific point is the work required to transform a unit of mass of fluid from an arbitrarily chosen state to the state under consideration.” Three Types of Potentials A. Pressure potential work required to raise the water pressure 1 P 1 P m P W1 = VdP = dP = ∫0 ∫0 m m ρ w ρ w ρw : density of water assumed to be independent of pressure V: volume z = z P = P v = v Current state z = 0 P = 0 v = 0 Reference state B. Elevation potential work required to raise the elevation 1 Z W ==mgdz gz 2 m ∫0 C. Kinetic potential work required to raise the velocity (dz = vdt) 2 11ZZdv vv W ==madz m dz == vdv 3 m ∫∫∫00m dt 02 Total potential: Total [hydraulic] head: P v 2 Φ P v 2 h == ++z Φ= +gz + g ρ g 2g ρw 2 w Unit [L2T-1] Unit [L] 2 Total head or P v hydraulic head: h =++z ρw g 2g Kinetic term pressure elevation [L] head [L] Piezometer P1 P2 ρg ρg h1 h2 z1 z2 datum A fluid moves from where the total head is higher to where it is lower. For an ideal fluid (frictionless and incompressible), the total head would stay constant.
    [Show full text]
  • Comparative Performance Evaluation of Pelton Wheel and Cross Flow Turbines for Power Generation
    EUROPEAN MECHANICAL SCIENCE Research Paper e-ISSN: 2587-1110 Comparative Performance Evaluation of Pelton Wheel and Cross Flow Turbines for Power Generation Oyebode O. O.1* and Olaoye J. O.2 1Department of Food, Agricultural and Biological Engineering, Kwara State University, Malete, Kwara State, Nigeria. 2Department of Agricultural and Biosystems Engineering, University of Ilorin, Ilorin, Kwara State, Nigeria. ORCID: Oyebode (0000-0003-1094-1149) Abstract The performance of two micro hydro power turbines (Pelton Wheel and Cross Flow Turbines) were evaluated at the University of Ilorin (UNILORIN) dam. The Dam has a net head of 4 m, flow rate of 0.017m3 and theoretical hydropower energy of 668W. The two turbines were tested and the optimized value of operating conditions namely; angle of inclination (15o above tangent, tangential and 15o below tangent), height to impact point (200mm, 250mm and 300mm) and length to impact point (50mm, 100mm and 150mm) were pre-set at their various levels for both Turbines. The optimum values of the process output or measured parameters were determined statistically using a 33X2 factorial experiment in three replicates. An optimum Turbine speed (538.38rpm) in off load condition was achieved at 250mm height to impact point, 150mm length to impact point and angle at tangential inclination. Similar combination also yielded an optimum turbine torque of 46.16kNm for Pelton Wheel Turbine. For the Crossflow Turbine, an optimum turbine speed of 330.09rpm was achieved by pre-setting 250mm height to impact point, 100mm length to impact point and 15º below tangent. Same combination also yielded an optimum turbine torque of 39.07kNm.
    [Show full text]
  • Undular Jump, Numerical Model and Sensitivity
    Alma Mater Studiorum - Università di Bologna FACOLTÀ DI SCIENZE MATEMATICHE, FISICHE E NATURALI Corso di Laurea specialistica in Fisica Dipartimento di Fisica UNDULAR JUMP NUMERICAL MODEL AND SENSITIVITY ANALYSIS Tesi di laurea di: Relatore: MICHELE RAMAZZA Prof. RAMBALDI SANDRO Correlatori: Prof. MANSERVISI SANDRO Dott. CERVONE ANTONIO Sessione III Anno Accademico 2007-2008 2 CONTENTS Abstract................................................................................................................................................5 Sommario.............................................................................................................................................5 List of symbol ....................................................................................................................................6 1.Introduction ....................................................................................................................................8 1.1.Open channel flow.................................................................................................................8 1.1.1.Introduction....................................................................................................................8 1.1.2.Classification of open channel flows.........................................................................8 1.1.3.Complexity ....................................................................................................................8 1.2.Bases of open channel hydraulics ...................................................................................10
    [Show full text]
  • Helical Turbine for Hydropower
    Tidewalker Engineering / Optimization of GHT Production Marine and Hydrokinetic Technology Readiness Advancement Initiative Funding Opportunity Announcement Number: DE-FOA-0000293 CFDA Number: 81.087 PROJECT NARRATIVE Tidewalker Engineering Trescott, Maine Title: Optimization of Gorlov Helical Turbine Production June 2010 Table of Contents: SUBJECT PAGE NUMBER Introduction: Project Narrative 2 Project Objectives 3 Merit Review Criteria Discussion 7 Project Timetable 13 Relevance and Outcomes / Impacts 14 Role of Participants 14 Facilities and Other Resources 15 Equipment 15 Bibliography and References 16 Appendix- A / Letter of Commitment 17 Appendix – B / Velocity Measurements 18 Appendix – C / GHT Applications 19 Appendix – D / Cost Sharing Grant 32 1 Tidewalker Engineering / Optimization of GHT Production Project Narrative: Under this proposal Tidewalker Engineering with the assistance of Dr. Alexander Gorlov and other specialists will investigate the feasibility of placing a hydro-kinetic device into a flexible dam system to generate electricity from tidal flows at sites with a substantial tidal range (average value of 18’). The study will also include the design of a turbo-generator unit which optimizes electrical production from this proposed mode of operation. Environmental issues associated with the placement of a flexible dam into a tidal flow will be analyzed in terms of regulatory licensing requirements. The applicability of this proposed mode of operation will be addressed as part of expected project benefits from the development potential of this concept. The eligibility standard as expressed in published responses within the Federal Connect network for this grant application directly addressed the issue of diversionary structures as excerpted below: DOE will not consider any application under this FOA for the development of a technology that would require blocking or severely altering existing tidal or river flows, as this would be considered a dam or diversionary structure.
    [Show full text]
  • Salt Flow Example
    GEO-SLOPE International Ltd, Calgary, Alberta, Canada www.geo-slope.com Salt Flow Example 1 Introduction Total hydraulic head consists of elevation head and pressure head. Pressure head is dependent on the density of the pore fluid, which is a function of both temperature and chemical composition. For density- dependent groundwater flow problems, the driving forces for flow include the hydraulic gradient, as well as a buoyancy force term caused by variations in density. Consequently, spatial variations in salinity generate a total hydraulic head gradient that governs density-dependent groundwater flow. The objective of this detailed example is to verify, by means of some simple calculations, the hydraulic head and groundwater fluxes calculated by CTRAN/W for coupled one-dimensional density-dependent groundwater flow problems. 2 Background Only a brief summary of the theory for density-dependent flow is provided here. A more comprehensive review can be found in the CTRAN/W Engineering book and the literature (e.g. Fetter, 1998; Frind, 1982a, b). As noted in the introduction, the pore fluid density affects the pressure head component of total hydraulic head. Consider the two point measurements of hydraulic head shown in Figure 1. The actual hydraulic pressure at P1 in the saline-water aquifer is P1 ss gh [1] where s = saline pore fluid density; g = acceleration due to gravity; and, hs = height of saline water in the piezometer. Figure 1 Equivalent fresh water head (after Fetter, 1988) Assume that another piezometer was completed in the saline-water aquifer at P2 , but that it was filled with fresh water.
    [Show full text]
  • The Cause and Statistical Analysis of the River Valley Contractions at the Xiluodu Hydropower Station, China
    water Article The Cause and Statistical Analysis of the River Valley Contractions at the Xiluodu Hydropower Station, China Mingwei Li 1 , Zhifang Zhou 1,*, Chao Zhuang 1 , Yawen Xin 1 , Meng Chen 2 and Jian Wu 1 1 School of Earth Sciences and Engineering, Hohai University, Nanjing 210098, China; [email protected] (M.L.); [email protected] (C.Z.); [email protected] (Y.X.); [email protected] (J.W.) 2 College of Hydrology and Water Resources, Hohai University, Nanjing 210098, China; [email protected] * Correspondence: [email protected] Received: 2 January 2020; Accepted: 8 March 2020; Published: 12 March 2020 Abstract: The Xiluodu Dam is a concrete double-curvature arch dam with a crest elevation of 610 m and a height of 285.5 m. Since the impoundment of the Xiluodu reservoir, remarkable river valley contractions (RVCs) have been observed upstream and downstream of the reservoir, potentially threatening the safety of the dam. However, the cause of these RVCs remains unclear. Based on an analysis of hydrogeological conditions, the RVCs were determined a result of the expansion of the aquifer, within which the effective stress decreased due to an increase in the hydraulic head after reservoir impoundment. Referring to the hydrostatic seasonal time (HST) model, a groundwater hydrostatic seasonal (GHS) model is proposed for simulating and predicting the development of the RVCs. Unlike the HST model, the GHS model can provide information on aquifer hydraulic diffusivity. The calibration results illustrate that the GHS model can accurately fit the observed RVCs data. The calculation results revealed that the RVCs were mainly affected by the hydraulic head of the confined aquifer, and that seasonal effects gave rise to less than 10% of the total RVCs.
    [Show full text]