1382 Pages
    by CRC Press

    1382 Pages
    by CRC Press

    Geotechnical Engineering of Dams, 2nd edition provides a comprehensive text on the geotechnical and geological aspects of the investigations for and the design and construction of new dams and the review and assessment of existing dams. The main emphasis of this work is on embankment dams, but much of the text, particularly those parts related to geology, can be used for concrete gravity and arch dams.

    All phases of investigation, design and construction are covered. Detailed descriptions are given from the initial site assessment and site investigation program through to the preliminary and detailed design phases and, ultimately, the construction phase. The assessment of existing dams, including the analysis of risks posed by those dams, is also discussed. This wholly revised and significantly expanded 2nd edition includes a lengthy new appendix on the assessment of the likelihood of failure of dams by internal erosion and piping.

    This valuable source on dam engineering incorporates the 200+ years of collective experience of the authors in the subject area. Design methods are presented in combination with their theoretical basis, to enable the reader to develop a proper understanding of the possibilities and limitations of a method. For its practical, well-founded approach, this work can serve as a useful guide for professional dam engineers and engineering geologists and as a textbook for university students.

    Author Biographies

    1 Introduction
    1.1 Outline of the book
    1.2 Types of embankment dams and their main features
    1.3 Types of concrete dams and their main features

    2 Key geological issues
    2.1 Basic definitions
    2.2 Types of anisotropic fabrics
    2.3 Defects in rock masses
    2.3.1 Joints
    2.3.2 Sheared and crushed zones (faults)
    2.3.3 Soil infill seams (or just infill seams)
    2.3.4 Extremely weathered (or altered) seams
    2.3.5 The importance of using the above terms to describe defects in rock
    2.4 Defects in soil masses
    2.5 Stresses in rock masses
    2.5.1 Probable source of high horizontal stresses
    2.5.2 Stress relief effects in natural rock exposures
    2.5.3 Effects in claystones and shales
    2.5.4 Special effects in valleys
    2.5.5 Rock movements in excavations
    2.6 Weathering of rocks
    2.6.1 Mechanical weathering
    2.6.2 Chemical decomposition
    2.6.3 Chemical weathering Susceptibility of common minerals to chemical weathering Susceptibility of rock substances to chemical weathering
    2.6.4 Weathered rock profiles and their development Climate and vegetation Rock substance types and defect types and pattern Time and erosion Groundwater and topography Features of weathered profiles near valley floors
    2.6.5 Complications due to cementation
    2.7 Chemical alteration
    2.8 Classification of weathered rock
    2.8.1 Recommended system for classification of weathered rock substance
    2.8.2 Limitations on classification systems for weathered rock
    2.9 Rapid weathering
    2.9.1 Slaking of mudrocks
    2.9.2 Crystal growth in pores
    2.9.3 Expansion of secondary minerals
    2.9.4 Oxidation of sulphide minerals Sulphide oxidation effects in rockfill dams – some examples Possible effects of sulphide oxidation in rockfill dams Sulphide oxidation – implications for site studies
    2.9.5 Rapid solution
    2.9.6 Surface fretting due to electro-static moisture absorption
    2.10 Landsliding at dam sites
    2.10.1 First-time and “reactivated’’ slides Reactivated slides First-time slides
    2.10.2 Importance of early recognition of evidence of past slope instability at dam sites
    2.10.3 Dams and landslides: Some experiences Talbingo Dam Tooma Dam Wungong Dam Sugarloaf Dam Thomson Dam
    2.11 Stability of slopes around storages
    2.11.1 Vital slope stability questions for the feasibility and site selection stages Most vulnerable existing or proposed project features, and parts of storage area? – Question 1 Currently active or old dormant landslides? – Questions 2 and 4 to 7 Areas where first-time landsliding may be induced (Questions 3 to 7) What is the likely post failure velocity and travel distance? What is the size of impulse waves which may be created?
    2.12 Watertightness of storages
    2.12.1 Models for watertightness of storages in many areas of non-soluble rocks
    2.12.2 Watertightness of storage areas formed by soluble rocks
    2.12.3 Features which may form local zones of high leakage, from any storage area
    2.12.4 Watertightness of storages underlain by soils
    2.12.5 Assessment of watertightness Storages in non-soluble rock areas – assessment of watertightness Storages in soluble rock areas – assessment of watertightness Storages formed in soils – assessment of watertightness
    2.12.6 Methods used to prevent or limit leakages from storages

    3 Geotechnical questions associated with various geological environments
    3.1 Granitic rocks
    3.1.1 Fresh granitic rocks, properties and uses
    3.1.2 Weathered granitic rocks, properties, uses and profiles
    3.1.3 Stability of slopes in granitic rocks
    3.1.4 Granitic rocks: check list
    3.2 Volcanic rocks (intrusive and flow)
    3.2.1 Intrusive plugs, dykes and sills
    3.2.2 Flows Flows on land Undersea flows
    3.2.3 Alteration of volcanic rocks
    3.2.4 Weathering of volcanic rocks
    3.2.5 Landsliding on slopes underlain by weathered basalt
    3.2.6 Alkali-aggregate reaction
    3.2.7 Volcanic rocks (intrusive and flow) check list of questions
    3.3 Pyroclastics 1
    3.3.1 Variability of pyroclastic materials and masses
    3.3.2 Particular construction issues in pyroclastics
    3.3.3 Pyroclastic materials – check list of questions
    3.4 Schistose rocks
    3.4.1 Properties of fresh schistose rock substances
    3.4.2 Weathered products and profiles developed in schistose rock
    3.4.3 Suitability of schistose rocks for use as filter materials, concrete aggregates and pavement materials
    3.4.4 Suitability of schistose rocks for use as rockfill
    3.4.5 Structural defects of particular significance in schistose rocks Minor faults developed parallel and at acute angles to the foliation Kink bands Mica-rich layers
    3.4.6 Stability of slopes formed by schistose rocks
    3.4.7 Schistose rocks – check list of questions
    3.5 Mudrocks
    3.5.1 Engineering properties of mudrocks
    3.5.2 Bedding-surface faults in mudrocks
    3.5.3 Slickensided joints or fissures
    3.5.4 Weathered products and profiles in mudrocks
    3.5.5 Stability of slopes underlain by mudrocks
    3.5.6 Development of unusually high pore pressures
    3.5.7 Suitability of mudrocks for use as construction materials
    3.5.8 Mudrocks – check list of questions
    3.6 Sandstones and related sedimentary rocks
    3.6.1 Properties of the rock substances
    3.6.2 Suitability for use as construction materials
    3.6.3 Weathering products
    3.6.4 Weathered profile and stability of slopes
    3.6.5 Sandstones and similar rocks – list of questions
    3.7 Carbonate rocks
    3.7.1 Effects of solution Rock masses composed of dense, fine grained rock substances comprising more than 90% of carbonate (usually Category O) Rock masses composed of dense fine grained rock substance containing 10% to 90% of carbonate (usually Category O) Rock masses composed of porous, low density carbonate rock substance (usually Category Y)
    3.7.2 Watertightness of dam foundations Dams which have experienced significant leakage problems
    3.7.3 Potential for sinkholes to develop beneath a dam, reservoir or associated works
    3.7.4 Potential for continuing dissolution of jointed carbonate rock in dam foundations
    3.7.5 Potential for continuing dissolution of aggregates of carbonate rock particles and of permeable carbonate substances (Category O carbonate, in each case)
    3.7.6 Discussion – potential for continuing dissolution of carbonate rocks in foundations Category O carbonate rocks Category Y carbonate rocks
    3.7.7 Potential problems with filters’ composed of carbonate rocks Category O carbonate rocks Category Y carbonate materials
    3.7.8 Suitability of carbonate rocks for embankment materials
    3.7.9 Suitability of carbonate rocks for concrete and pavement materials
    3.7.10 Stability of slopes underlain by carbonate rocks
    3.7.11 Dewatering of excavations in carbonate rocks
    3.7.12 Carbonate rocks – check list of questions
    3.8 Evaporites
    3.8.1 Performance of dams built on rocks containing evaporites
    3.8.2 Guidelines for dam construction at sites which contain evaporites
    3.8.3 Evaporites – checklist of questions
    3.9 Alluvial soils
    3.9.1 River channel deposits
    3.9.2 Open-work gravels
    3.9.3 Oxbow lake deposits
    3.9.4 Flood plain, lacustrine and estuarine deposits
    3.9.5 Use of alluvial soils for construction
    3.9.6 Alluvial soils, list of questions
    3.10 Colluvial soils
    3.10.1 Occurrence and description Scree and talus Slopewash soils Landslide debris
    3.10.2 Properties of colluvial soils Scree and talus Slopewash Landslide debris
    3.10.3 Use as construction materials
    3.10.4 Colluvial soil – list of questions
    3.11 Laterites and lateritic weathering profiles
    3.11.1 Composition, thicknesses and origin of lateritic weathering profiles
    3.11.2 Properties of lateritic soils
    3.11.3 Use of lateritic soils for construction
    3.11.4 Karstic features developed in laterite terrain
    3.11.5 Recognition and interpretation of silcrete layer
    3.11.6 Lateritic soils and profiles – list of questions
    3.12 Glacial deposits and landforms
    3.12.1 Glaciated valleys
    3.12.2 Materials deposited by glaciers Properties of till materials Disrupted bedrock surface beneath glaciers
    3.12.3 Glaciofluvial deposits
    3.12.4 Periglacial features
    3.12.5 Glacial environment – list of questions

    4 Planning, conducting and reporting of geotechnical investigations
    4.1 The need to ask the right questions
    4.1.1 Geotechnical engineering questions
    4.1.2 Geological questions Questions relating to rock and soil types, climate and topography Questions relating to geological processes, i.e. to the history of development of the site
    4.1.3 Geotechnical questions for investigations of existing dams
    4.2 Geotechnical input at various stages of project development
    4.3 An iterative approach to the investigations
    4.4 Progression from regional to local studies
    4.4.1 Broad regional studies Objectives Activities
    4.4.2 Studies at intermediate and detailed scales Objectives Activities
    4.5 Reporting
    4.6 Funding of geotechnical studies
    4.7 The site investigation team

    5 Site investigation techniques
    5.1 Topographic mapping and survey
    5.2 Interpretation of satellite images aerial photographs and photographs taken during construction
    5.2.1 Interpretation of satellite images
    5.2.2 Interpretation of aerial photographs Coverage Interpretation
    5.2.3 Photographs taken during construction
    5.3 Geomorphological mapping
    5.4 Geotechnical mapping
    5.4.1 Use of existing maps and reports
    5.4.2 Geotechnical mapping for the project Regional mapping Geotechnical mapping
    5.5 Geophysical methods, surface and downhole
    5.5.1 Surface geophysical methods Seismic refraction Self potential Electrical resistivity Electromagnetic conductivity Magnetic Microgravity Ground penetrating radar
    5.5.2 Down-hole logging of boreholes
    5.5.3 Cross-hole and up-hole seismic
    5.6 Test pits and trenches
    5.6.1 Test pits
    5.6.2 Trenches
    5.7 Sluicing
    5.8 Adits and shafts
    5.9 Drill holes
    5.9.1 Drilling objectives
    5.9.2 Drilling techniques and their application
    5.9.3 Auger drilling
    5.9.4 Percussion drilling
    5.9.5 Rotary drilling
    5.9.6 Sonic drilling
    5.10 Sampling
    5.10.1 Soil samples
    5.10.2 Rock samples
    5.11 In situ testing
    5.11.1 In situ testing in soils
    5.11.2 In situ testing of rock Borehole orientation Borehole impression packer Borehole imaging
    5.12 Groundwater
    5.13 In situ permeability tests on soil
    5.14 In situ permeability tests in rock
    5.14.1 Lugeon value and equivalent rock mass permeability
    5.14.2 Test methods
    5.14.3 Selection of test section
    5.14.4 Test equipment Packers Water supply system Selection of test pressures
    5.14.5 Test procedure Presentation and interpretation of results
    5.15 Use of surface survey and borehole inclinometers
    5.15.1 Surface survey
    5.15.2 Borehole inclinometers
    5.16 Common errors and deficiencies in geotechnical investigation

    6 Shear strength, compressibility and permeability of embankment materials and soil foundations
    6.1 Shear strength of soils
    6.1.1 Drained strength – definitions
    6.1.2 Development of drained residual strength φR
    6.1.3 Undrained strength conditions
    6.1.4 Laboratory testing for drained strength parameters, and common errors Triaxial test Direct shear test Ring shear test Comparison of field residual with laboratory residual strength obtained from direct shear and ring shear
    6.1.5 Laboratory testing for undrained strength
    6.1.6 Estimation of the undrained strength from the Over-Consolidation Ratio (OCR), at rest earth pressure coefficient Ko, and effective stress strengths Estimation of undrained strength from OCR Estimation of undrained strength from effective stress shear parameters
    6.1.7 Estimation of the undrained strength of cohesive soils from in situ tests Cone Penetration and Piezocone Tests Vane shear Self Boring Pressuremeter
    6.1.8 Shear strength of fissured soils The nature of fissuring, and how to assess the shear strength Triaxial testing of fissured soils
    6.1.9 Estimation of the effective friction angle of granular soils Methods usually adopted In situ tests Laboratory tests Empirical estimation
    6.1.10 Shear strength of partially saturated soils
    6.2 Shear strength of rockfill
    6.3 Compressibility of soils and embankment materials
    6.3.1 General principles Within the foundation Within the embankment
    6.3.2 Methods of estimating the compressibility of earthfill, filters and rockfill Using data from the performance of other dams – earthfill Using data from the performance of other dams – rockfill In situ testing Laboratory testing Tensile properties of plastic soils
    6.4 Permeability of soils
    6.4.1 General principles
    6.4.2 Laboratory test methods
    6.4.3 Indirect test methods Oedometer and triaxial consolidation test Estimation of permeability of sands from particle size distribution
    6.4.4 Effects of poor sampling on estimated permeability in the laboratory
    6.4.5 In situ testing methods

    7 Clay mineralogy, soil properties, and dispersive soils
    7.1 Introduction
    7.2 Clay minerals and their structure
    7.2.1 Clay minerals
    7.2.2 Bonding of clay minerals Primary bonds Secondary bonds
    7.2.3 Bonding between layers of clay minerals
    7.3 Interaction between water and clay minerals
    7.3.1 Adsorbed water
    7.3.2 Cation exchange
    7.3.3 Formation of diffuse double layer
    7.3.4 Mechanism of dispersion
    7.4 Identification of clay minerals
    7.4.1 X-ray diffraction
    7.4.2 Differential Thermal Analysis (DTA)
    7.4.3 Electron microscopy
    7.4.4 Atterberg limits
    7.4.5 The activity of the soil
    7.5 Engineering properties of clay soils related to the types of clay minerals
    7.5.1 Dispersivity
    7.5.2 Shrink and swell characteristics
    7.5.3 Shear strength
    7.5.4 Erosion properties
    7.6 Identification of dispersive soils
    7.6.1 Laboratory tests Emerson class number Soil Conservation Service test Pinhole dispersion classification Chemical tests Recommended approach
    7.6.2 Field identification and other factors
    7.7 Use of dispersive soils in embankment dams
    7.7.1 Problems with dispersive soils
    7.7.2 Construction with dispersive soils Provide properly designed and constructed filters Proper compaction of the soil Careful detailing of pipes or conduits through the embankment Lime or gypsum modification of the soil Sealing of cracks in the abutment and cutoff trench
    7.7.3 Turbidity of reservoir water

    8 Internal erosion and piping of embankment dams and in dam foundations
    8.1 The importance of internal erosion and piping to dam safety
    8.2 Description of the internal erosion and piping process
    8.2.1 The overall process leading to failure of a dam
    8.2.2 Initiation of internal erosion
    8.2.3 Continuation of erosion
    8.2.4 Progression of erosion
    8.2.5 Detection and intervention
    8.2.6 Breach
    8.3 Concentrated leak erosion
    8.3.1 The overall process
    8.3.2 Situations where cracking and low stress zones may be present in an embankment or the foundation Cracking and hydraulic fracture due to cross valley differential settlement of the core Cracking and hydraulic fracture due to cross valley arching Cracking and hydraulic fracture due to differential settlement in the foundation under the core Cracking and hydraulic fracture due to small scale irregularities in the foundation profile under the core Cracking due to lack of support for the core by the shoulders of the embankment Cracking and hydraulic fracture due to arching of the core onto the shoulders of the embankment Crack or gap adjacent to a spillway or abutment walls and where concrete dams abut embankment dams Crack or hydraulic fracture in poorly compacted layers in the embankment Internal erosion associated with conduits embedded in the embankment Cracking due to desiccation Transverse cracking caused by settlement during earthquakes Cracking or high permeability layers due to freezing Internal erosion initiated by the effects animal burrows and vegetation Relative importance of conduits, spillway walls cracking mechanisms, and poorly compacted zones
    8.3.3 Estimation of crack width and depth of cracking Cracking due to differential settlement, adjacent walls Cracks formed by collapse settlement of poorly compacted soil
    8.3.4 The mechanics of erosion in concentrated leaks The procedure for assessing whether erosion will initiate The estimation of hydraulic shear stresses in cracks and pipes Erosion properties of soils in the core of embankment dams – basic principles Effect of degree of saturation of the soil Effect of the testing method on the critical shear stress to initiate erosion (τc) and the erosion rate index Effect of dispersion, slaking, soil structure and shear strength on erosion properties
    8.3.5 Comparison of the hydraulic shear stress in the crack (τ) to the critical shear stress which will initiate erosion for the soil in the core of the embankment (τc)
    8.4 Backward erosion
    8.4.1 General description of backward erosion
    8.4.2 Experimental modelling of backward erosion piping
    8.4.3 Methods for predicting whether backward erosion piping will initiate and progress Empirical rules for estimating a factor of safety Terzaghi and Peck (1948) Sellmeijer and co-workers at Deltares method Schmertmann method
    8.4.4 Some field observations
    8.4.5 Suggested approach to design for and assessing backward erosion piping
    8.4.6 Guidance on whether the overlying soil will form a roof to the pipe
    8.4.7 Methods for prediction of initiation and progression of global backward erosion
    8.5 Suffusion of internally unstable soils
    8.5.1 General description of suffusion
    8.5.2 Methods of identifying soils which are internally unstable and potentially subject to suffusion General requirements Some methods for assessing whether a soil is internally unstable Some general comments
    8.5.3 Assessment of the gradation after suffusion
    8.5.4 Assessment of the seepage gradient which will cause suffusion
    8.5.5 Some general comments Need for project specific laboratory tests Do not use “average’’ soil gradations Allow for the effects of segregation when assessing suffusion
    8.6 Contact erosion
    8.6.1 General description of contact erosion
    8.6.2 Methods for predicting initiation and progression of contact erosion Non plastic sand below a coarse soil layer Non plastic silt and clay (particles <75μm) below a coarse layer Non-plastic silt above a coarse soil layer General comment
    8.6.3 Contact erosion or scour of the dam core into open joints in rock in the foundation
    8.7 Continuation and filter action
    8.8 Progression of erosion
    8.8.1 General description
    8.8.2 Overall approach for assessing progression for concentrated leak erosion
    8.8.3 Assessing whether the soil will hold a roof to a developing pipe
    8.8.4 Assessing whether crack filling action will occur Internal erosion in the embankment Internal erosion through the foundation Internal erosion of the embankment into or at the foundation 
    8.8.5 Assessing whether upstream flow limitation will occur
    8.8.6 Assessing the rate of development of the pipe
    8.9 Detection of internal erosion and piping
    8.9.1 General principles
    8.9.2 Some information on the rate of internal erosion and piping
    8.9.3 The likelihood of detection and intervention
    8.10 Intervention and repair
    8.11 Initiation of breach
    8.11.1 General principles
    8.11.2 Breach by gross enlargement
    8.11.3 Breach by slope instability
    8.11.4 Breach by unravelling or sloughing
    8.11.5 Breach by sinkhole development leading to loss of freeboard
    8.12 Assessment of the likelihood of internal erosion and piping in existing dams
    8.12.1 General procedure
    8.12.2 The importance of having complete and reliable information upon which to make the assessment of internal erosion Geometric model Geological model of the foundation Geotechnical model of the embankment and foundations Hydraulic or seepage model Stress state in the dam and its foundation General comments
    8.12.3 Loading conditions Reservoir level loading Earthquake loading
    8.12.4 Potential Failure Modes Analysis (PFMA)
    8.12.5 Screening of potential failure modes Screening of PFM on the zoning of the dam and the properties of the core of the embankment Screening of PFM on foundation geology and properties Screening of PFM on details of the embankment foundation geometry, compaction of the core, and conduits and retaining walls
    8.12.6 Estimation of likelihoods of failure for the Potential Failure Modes applicable to the dam Some general principles Summary of how to estimate conditional probabilities within the event tree Ways in which the safety of the dam against internal erosion and piping can be considered Quantitative risk analysis methods for internal erosion and piping

    9 Design, specification and construction of filters
    9.1 General requirements for design and the function of filters
    9.1.1 Functional requirements
    9.1.2 Flow conditions acting on filters
    9.1.3 Critical and non critical filters
    9.1.4 Filter design notation and concepts Notation Filtering concepts Laboratory test equipment
    9.2 Design of critical and non-critical filters
    9.2.1 Particle size based methods for designing no erosion filters with flow normal to the filter Original USBR method Sherard and Dunnigan method Foster and Fell method Vaughan and Soares method
    9.2.2 Methods based on constriction or opening size
    9.2.3 Methods based on the permeability of the filter Delgardo and co-workers Vaughan and Soares, Vaughan and Bridle method
    9.2.4 Recommended method for design of critical no erosion filters, with flow normal to the filter
    9.2.5 Recommended method for design of less critical and non-critical filters Filters upstream of the dam core Filters under rip-rap
    9.2.6 Review of available methods for designing filters with flow parallel to the filter
    9.2.7 Design criteria for pipe drains and pressure relief well screens Pipe drains Pressure relief well screens
    9.2.8 Other factors affecting filter design and performance Criteria to assess internal instability or suffusion Segregation Ability of the filter to hold a crack Permeability “Blow-out’’ or “heave’’ of the filter
    9.3 Assessing filters and transition zones in existing dams
    9.3.1 Some general issues and concepts
    9.3.2 Continuing and excessive erosion criteria
    9.3.3 Discussion of continuation scenarios in existing dams Internal erosion in the embankment, from the embankment into the foundation or into openings in conduits passing through the embankment Internal erosion in the foundation Internal erosion of the embankment at or into the foundation
    9.3.4 Assessment of the likelihood of continuation where a filter/transition zone does not satisfy no-erosion filter criteria General principles Details of how to apply the Foster and Fell (1999a, 2001) method for assessing the likelihood of continuation of erosion for filters and transitions which do not meet modern filter design criteria
    9.3.5 Assessment of the likelihood of continuation for internal erosion into an open defect, joint or crack in the foundation, in a wall or conduit
    9.4 Specification of particle size and durability of filters
    9.4.1 Particle size distribution
    9.4.2 Durability Standard tests for durability and particle shape Possible effects if carbonate rocks are used as filter materials Effects if rocks containing sulphide minerals are used as filter materials Other investigations for filter materials
    9.4.3 Contractual difficulties associated with gradation and durability of filters Fines content Use of crushed rock for fine filters
    9.5 Dimensions, placement and compaction of filters
    9.5.1 Dimensions and method of placement of filters Some general principles Placement methods
    9.5.2 Sequence of placement of filters and control of placement width and thickness
    9.5.3 Compaction of filters
    9.6 Use of geotextiles as filters in dams
    9.6.1 Types and properties of geotextiles
    9.6.2 Geotextile filter design criteria General requirements Filtering requirement Clogging and blinding resistance Permeability requirement Durability or “survivability’’ requirement Use of geotextile filters in dams Construction factors Sources of detailed information

    10 Embankment dams, their zoning and design for control of seepage and internal erosion and piping
    10.1 Historic performance of embankment dams and the lessons to be learned
    10.2 Types of embankment dams, their advantages and limitations
    10.2.1 The main types of embankment dams and zoning
    10.2.2 The general principles of control of seepage pore pressures and internal erosion and piping
    10.2.3 Taking account of the likelihood and consequences of failure in selecting the type of embankment
    10.2.4 Types of embankment dams, their advantages, limitations and applicability
    10.3 Zoning of embankment dams and typical construction materials
    10.3.1 General principles
    10.3.2 Examples of embankment designs Zoned earthfill dams Earthfill dams with horizontal and vertical drains Central core earth and rockfill dams Sloping upstream core earth and rockfill dam Concrete face rockfill dams
    10.4 Selection of embankment type
    10.4.1 Availability of construction materials Earthfill Rockfill Filters and filter drains
    10.4.2 Foundation conditions
    10.4.3 Climate
    10.4.4 Topography and relation to other structures
    10.4.5 Saddle dam
    10.4.6 Staged construction
    10.4.7 Time for construction
    10.5 General requirements and methods of control of seepage and internal erosion and piping in embankment dams and their foundations
    10.6 Some particular features of rock and soil foundations which affect seepage and internal erosion control
    10.7 Details of some measures for pore pressure and seepage flow control
    10.7.1 Horizontal and vertical drains in the embankment
    10.7.2 Treatment of the sides of the cutoff trench
    10.7.3 Prevention of critical seepage gradients and heave of the foundation
    10.7.4 Design of pressure relief wells
    10.8 Control of foundation seepage and internal erosion and piping by cutoffs
    10.8.1 General effectiveness of cutoffs
    10.8.2 Cutoff trench
    10.8.3 Slurry trench cutoff backfilled with bentonite-sand-gravel
    10.8.4 Grout diaphragm wall
    10.8.5 Diaphragm wall using rigid or plastic concrete
    10.8.6 Methods of excavation of diaphragm walls
    10.8.7 Permeability and performance of cutoff walls
    10.8.8 We live in a three dimensional world
    10.9 Examples of dam upgrades to address deficiencies in internal erosion and piping control
    10.9.1 Upgrades to reduce the likelihood of continuation of erosion by providing filters and cutoffs
    10.9.2 Upgrades to reduce the likelihood of breach

    11 Analysis of stability and deformations
    11.1 Analysis of stability and deformations methods of analysis
    11.2 Limit equilibrium analysis methods
    11.2.1 General characteristics
    11.2.2 Some common problems
    11.2.3 Three dimensional analysis
    11.2.4 Shear strength of partially saturated soils
    11.3 Selection of shear strength for design
    11.3.1 Drained, effective stress parameters Peak, residual or fully softened strength in clay soils? Selection of design parameters in clay soils Selection of design parameters – granular soils and rockfill
    11.3.2 Undrained, total stress parameters Triaxial compression, extension or direct simple shear strength Selection of design parameters
    11.3.3 Inherent soil variability
    11.4 Estimation of pore pressures and selection of strengths for steady state, construction and drawdown conditions 11.4.1 Steady state seepage condition Steady state pore pressures Pore pressures under flood conditions
    11.4.2 Pore pressures during construction and analysis of stability at the end of construction Some general principles Estimation of construction pore pressures by Skempton (1954) method Estimation of construction pore pressures from drained and specified undrained strengths Estimation of pore pressures using advanced theory of partially saturated soil Undrained strength analysis Summing up
    11.4.3 Drawdown pore pressures and the analysis of stability under drawdown conditions Some general issues Estimation of drawdown pore pressures, excluding the effects of shear-induced pore pressures Methods for assessment of the stability under drawdown conditions Some detailed issues for drawdown analyses
    11.5 Design acceptance criteria
    11.5.1 Acceptable factors of safety
    11.5.2 Post failure deformation assessment
    11.6 Examples of unusual issues in analysis of stability
    11.6.1 Hume No. 1 Embankment
    11.6.2 Eppalock Dam
    11.6.3 The lessons learnt
    11.7 Analysis of deformations
    11.7.1 Analyses of embankment cross sections
    11.7.2 Cross valley deformation analyses
    11.8 Probabilistic analysis of the stability of slopes

    12 Design of embankment dams to withstand earthquakes
    12.1 Effect of earthquake on embankment dams
    12.2 Earthquakes and their characteristics
    12.2.1 Earthquake mechanisms and ground motion
    12.2.2 Earthquake magnitude and intensity
    12.2.3 Attenuation and amplification of ground motion
    12.2.4 Earthquakes induced by the reservoir
    12.3 Evaluation of seismic hazard
    12.3.1 Terminology
    12.3.2 General principles of seismic hazard assessment Probabilistic approach Seismic hazard from known active or capable faults
    12.3.3 Other forms of expression of seismic hazard
    12.3.4 Selection of design seismic loading Deterministic approach Risk based approach Which approach to use?
    12.3.5 Modelling vertical ground motions
    12.3.6 The need to get good seismological advice
    12.4 Principles of risk based analyses for earthquake loads
    12.4.1 General principles
    12.4.2 Failure by loss of freeboard and overtopping
    12.4.3 Failure by cracking and internal erosion and piping
    12.5 Liquefaction of dam embankments and foundations
    12.5.1 Definitions and the mechanics of liquefaction Definitions Some consideration of the mechanics of liquefaction of granular soils Suggested flow chart for evaluation of soil liquefaction
    12.5.2 Soils susceptible to liquefaction Methods based on soil classification and in situ moisture content Discussion and recommended approach Methods based on geology and age of the deposit
    12.5.3 The “simplified procedure’’ for assessing liquefaction resistance of a soil Background to the simplified method Discussion of differences between the Youd et al. (2001), Seed et al. (2003) and Idriss and Boulanger (2008) methods The simplified method – outline Evaluation of Cyclic Stress Ratio (CSR) Evaluation of Cyclic Resistance Ratio for M7.5 earthquakes (CRR7.5) from the Standard Penetration Tests using the Boulanger and Idriss (2012), Idriss and Boulanger (2008) method Evaluation of the Cyclic Resistance Ratio for M7.5 earthquake (CRR7.5) from Cone Penetration Tests using the Idriss and Boulanger (2008) method Evaluation of Cyclic Resistance Ratio for M7.5 earthquake (CRR7.5) from shear wave velocity using the Andrus and Stokoe (2000) method Earthquake magnitude scaling factors and factor of safety against liquefaction Corrections for overburden stress and static shear stress Allowance for the age of the soil deposit
    12.6 Liquefied undrained shear strength and post earthquake stability analysis
    12.6.1 Some general principles
    12.6.2 Background to the assessment of the liquefied shear strength Su(LIQ)
    12.6.3 Some methods for assessing the strength of liquefied soils in the embankment and foundation “Critical State’’ based methods Normalized strength ratio methods Other methods
    12.6.4 Some other factors to consider
    12.6.5 Recommended approach to assessing the liquefied undrained strength soils of in the embankment and foundation
    12.6.6 Methods for assessing the post earthquake strength of non-liquefied soils in the embankment and foundation Saturated potentially liquefiable soils Cyclic softening in clays and plastic silts Compacted plastic and non-plastic soils
    12.6.7 Liquefaction potential and limit equilibrium stability analysis
    12.6.8 Site investigations requirements and development of geotechnical model of the foundation
    12.7 Seismic deformation analysis of embankment dams
    12.7.1 Preamble
    12.7.2 Performance of embankment dams during earthquakes
    12.7.3 The methods available and when to use them
    12.7.4 Suggested approach to estimation of deformations
    12.7.5 Screening methods USACE method Hynes-Griffin and Franklin (1984) pseudo-static seismic coefficient method
    12.7.6 Empirical database methods Swaisgood (1998, 2003) empirical method for estimating crest settlements Pells and Fell empirical method for estimating settlement, damage and cracking
    12.7.7 Simplified methods of deformation analysis for dams where liquefaction and significant strain weakening do not occur General principles Makdisi and Seed (1978) method Bray and Travasarou (2007) method
    12.7.8 Advanced numerical methods for estimating deformations during and post earthquake for non-liquefied and liquefied conditions Total stress codes Effective stress codes Summary
    12.8 Defensive design principles for embankment dams
    12.9 Methods for upgrading embankment dams for seismic loads
    12.9.1 General approaches
    12.9.2 Upgrading of embankment dams not subject to liquefaction
    12.9.3 Embankment dams subject to liquefaction

    13 Embankment dam details
    13.1 Freeboard
    13.1.1 Definitions and overall requirements
    13.1.2 Examples of freeboard requirements New embankment dams Existing embankment dams Suggested approach for determining freeboard
    13.1.3 Estimation of wave run up freeboard for design of small dams and for feasibility and preliminary design
    13.1.4 Estimation of wind setup and wave run-up for detailed design Fetch Design wind Wave height Wave length and wave period Wave run-up Wind set-up
    13.2 Slope protection
    13.2.1 Upstream slope protection General requirements Sizing and layer thickness Selection of design wind speed and acceptable damage Rock quality and quarrying Design of filters under rip-rap Use of soil cement and shotcrete for upstream slope protection
    13.2.2 Downstream slope protection General requirements Grass and rockfill cover
    13.3 Embankment crest details
    13.3.1 Camber
    13.3.2 Crest width
    13.3.3 Curvature of crest in plan
    13.4 Embankment dimensioning and tolerances
    13.4.1 Dimensioning
    13.4.2 Tolerances
    13.5 Conduits through embankments
    13.5.1 Piping into the conduit
    13.5.2 Piping along and above the conduit
    13.5.3 Flow out of the conduit
    13.5.4 Conclusions
    13.5.5 Recommendations
    13.6 Interface between earthfill and concrete structures
    13.6.1 Interface between retaining walls and embankment
    13.6.2 Interface between concrete gravity dam and embankment
    13.7 Flood control structures
    13.8 Design of dams for overtopping during construction
    13.8.1 General design concepts
    13.8.2 Types of steel mesh reinforcement
    13.8.3 Design of steel reinforcement
    13.9 Design of rip rap for minor overtopping of levees or small dams during floods
    13.10 Other overtopping protection methods for embankment dams

    14 Specification and quality control of earthfill and rockfill
    14.1 Specification of rockfill
    14.2 Specification of earthfill
    14.3 Specification of filters
    14.4 Quality control
    14.4.1 General
    14.4.2 ‘Methods,’ and ‘performance’ criteria
    14.4.3 Quality control
    14.4.4 Influence of non technical factors on the quality of embankment dams
    14.5 Testing of rockfill
    14.5.1 Particle size, density and permeability
    14.5.2 Field rolling trials
    14.6 Testing of earthfill
    14.6.1 Compaction-test methods
    14.6.2 Compaction control – some common problems
    14.6.3 Compaction control – some other methods

    15 Concrete face rockfill dams
    15.1 General arrangement and reasons for selecting this type of dam
    15.1.1 Historic development of concrete face rockfill dams
    15.1.2 General arrangement – modern practice
    15.1.3 Site suitability, and advantages of concrete face rockfill dams
    15.2 Rockfill zones and their properties
    15.2.1 Zone 2D – Transition rockfill
    15.2.2 Zones 2E, 3A and 3B – Fine rockfill, rockfill and coarse rockfill General requirements Layer thickness and compaction Use of gravel as rockfill
    15.2.3 Effect of rock properties, compaction and addition of water during compaction on modulus of rockfill
    15.2.4 Estimation of the modulus of rockfill Estimation of the secant modulus Erc Estimation of the first filling ‘pseudo modulus’ Erf Effect of valley shape
    15.2.5 Selection of side slopes and analysis of slope stability
    15.3 Concrete face
    15.3.1 Plinth
    15.3.2 Face slab Face slab thickness Reinforcement Vertical and horizontal joints
    15.3.3 Perimetric joint General requirements Water stop details
    15.3.4 Crest detail
    15.4 Construction aspects
    15.4.1 Plinth construction and special details
    15.4.2 River diversion
    15.4.3 Embankment construction
    15.5 Some non-standard design features
    15.5.1 Use of dirty rockfill
    15.5.2 Dams on erodible foundation
    15.5.3 Leaving alluvium in the dam foundation
    15.5.4 Plinth gallery
    15.5.5 Earthfill cover over the face slab
    15.5.6 Spillway over the dam crest
    15.6 Observed settlements, and displacements of the face slab, and joints
    15.6.1 General behaviour
    15.6.2 Post construction crest settlement
    15.6.3 Face slab displacements and cracking
    15.6.4 Cracks in CFRD dams
    15.7 Observed leakage of CFRD
    15.7.1 Modern CFRD
    15.7.2 Early CFRD and other dams which experienced large leakage
    15.8 Framework for assessing the likelihood of failure of CFRD
    15.8.1 Overview of approach
    15.8.2 Assessment of likelihood of initiation of a concentrated leak
    15.8.3 Assessment of the likelihood of continuation of a concentrated leak
    15.8.4 Assessment of the likelihood of progression to form a pipe
    15.8.5 Assessment of the likelihood of a breach forming
    15.8.6 Concluding remarks
    15.9 Further reading

    16 Concrete gravity dams and their foundations
    16.1 Outline of this chapter
    16.2 Analysis of the stability for normal operating and flood loads
    16.2.1 Design loads
    16.2.2 Load combinations
    16.2.3 Kinematically feasible failure models
    16.2.4 Analysis of stability
    16.2.5 Acceptance criteria
    16.3 Strength and compressibility of rock foundations
    16.3.1 Some general principles
    16.3.2 Assessment of rock shear strength General requirements Shear strength of clean discontinuities Shear strength of infilled joints and seams showing evidence of previous displacement Shear strength of thick infilled joints, seams or extremely weathered beds with no previous displacement Shear strength of jointed rock masses with no persistent discontinuities
    16.3.3 Tensile strength of rock foundations
    16.3.4 Compressibility of jointed rock foundation
    16.3.5 Ultimate bearing capacity of rock foundations
    16.4 Strength of the concrete in the dam
    16.4.1 What is recommended in guidelines
    16.4.2 Measured concrete strengths from some USA dams Background to the data Tensile strength of concrete and lift joints Shear strength of concrete
    16.5 Strength of the concrete – rock contact
    16.6 Uplift in the dam foundation and within the dam
    16.6.1 What is recommended in guidelines?
    16.6.2 Some additional information on uplift pressures Effects of geological features and deformations on foundation uplift pressures Analysis of EPRI (1992) uplift data Design of drains Hydro-dynamic forces Aprons ‘Contact’ or ‘box’ drains
    16.7 Silt load
    16.8 Ice load
    16.9 The design and analysis of gravity dams for earthquake loading
    16.9.1 Introduction
    16.9.2 Gravity dams on soil foundations
    16.9.3 Gravity dams on rock foundations General The Westergaard pseudo-static method The Fenves-Chopra refined pseudo-static method The US Corps of engineers method Finite Element Method (FEM) Design earthquake input motion Should vertical ground motion be included? Reservoir level variation What do the results of analyses mean? Post-earthquake analyses Dams on rock foundations with potentially deep-seated failure mechanisms Dams on foundations that could be subjected to ground displacement
    16.9.4 Concluding remarks

    17 Foundation preparation and cleanup for embankment and concrete dams
    17.1 General requirements
    17.1.1 Embankment dams
    17.1.2 Concrete dams
    17.1.3 Definition of foundation requirements in geotechnical terms
    17.2 General foundation preparation for embankment dams
    17.2.1 General foundation under earthfill Rock foundation Soil foundation
    17.2.2 General foundation under rockfill
    17.2.3 General foundation under horizontal filter drains
    17.3 Cutoff foundation for embankment dams
    17.3.1 The overall objectives
    17.3.2 Cutoff in rock
    17.3.3 Cutoff in soil
    17.4 Width and batter slopes for cutoff in embankment dams
    17.4.1 Cutoff width W
    17.4.2 Batter slope
    17.4.3 Setting out
    17.5 Selection of cutoff foundation criteria for embankment dams
    17.6 Slope modification and seam treatment for embankment dams
    17.6.1 Slope modification
    17.6.2 Seam treatment
    17.6.3 Dental concrete, pneumatically applied mortar, and slush concrete
    17.6.4 The need for good records of foundation treatment
    17.7 Assessment of existing embankment dams
    17.8 Foundation preparation for concrete gravity dams on rock foundations
    17.8.1 The general requirements
    17.8.2 Excavation to expose a suitable rock foundation
    17.8.3 Treatment of particular features
    17.8.4 Treatment at sites formed by highly stressed rock

    18 Foundation grouting
    18.1 General concepts of grouting dam foundations
    18.2 Grouting design – cement grout
    18.2.1 Staging of grouting
    18.2.2 The principles of ‘closure’
    18.2.3 The design and quality control of cement grouts The cement and additives used for grouting Water cement ratio Rheological properties of grout High, medium and low mobility grouts Field quality control testing of grouts Grout pressure Recommended closure criteria for embankment and concrete dams
    18.2.4 Effect of cement particle size, viscosity, fracture spacing and Lugeon value on the effectiveness of grouting
    18.2.5 The effectiveness of a grout curtain in reducing seepage
    18.2.6 The depth and lateral extent of grouting
    18.2.7 Grout hole position and orientation 1
    18.3 Some practical aspects of grouting with cement
    18.3.1 Grout holes
    18.3.2 Standpipes
    18.3.3 Grout caps
    18.3.4 Grout mixers, agitator pumps and other equipment
    18.3.5 Monitoring of grouting program
    18.3.6 Water pressure testing
    18.4 Prediction of grout takes
    18.5 Durability of cement grout curtains
    18.6 Chemical grouts in dam engineering
    18.6.1 Types of chemical grouts and their properties
    18.6.2 Grout penetrability in soil and rock
    18.6.3 Grouting technique
    18.6.4 Applications to dam engineering

    19 Mine and industrial tailings dams
    19.1 General
    19.2 Tailings and their properties
    19.2.1 What are mine tailings?
    19.2.2 Tailings terminology and definitions
    19.2.3 Tailings properties General Particle size Mineralogy Dry density and void ratio Permeability Properties of water in tailings
    19.3 Methods of tailings discharge and water recovery
    19.3.1 Tailings discharge
    19.3.2 Cyclones
    19.3.3 Sub-aqueous vs sub-aerial deposition
    19.3.4 Water Recovery
    19.4 Prediction of tailings properties
    19.4.1 Beach slopes and slopes below water
    19.4.2 Particle sorting
    19.4.3 Permeability
    19.4.4 Dry density
    19.4.5 The prediction of desiccation rates
    19.4.6 Drained and undrained shear strength 1 Drained shear strength Undrained shear strength
    19.5 Methods of construction of tailings dams
    19.5.1 General
    19.5.2 Construction using tailings Upstream method Downstream method Centreline method
    19.5.3 Construction using conventional water dams
    19.5.4 Selection of embankment construction method
    19.5.5 Control of seepage by tailings placement, blanket drains and under-drains Tailings placement Drainage blankets and under-drains
    19.5.6 Some factors affecting the potential for internal erosion and piping of tailings dams
    19.5.7 Some factors to consider for seismic design of tailings dams Conventional dams and downstream construction Upstream construction
    19.5.8 Storage layout
    19.5.9 Other disposal methods Thickened discharge or Robinsky method Co-disposal Paste disposal Belt filtration Disposal into open cut and underground mine workings Discharge into rivers or the sea
    19.6 Seepage from tailings dams and its control
    19.6.1 General
    19.6.2 Principles of seepage flow and estimation
    19.6.3 Some common errors in seepage analysis
    19.6.4 Seepage control measures Controlled placement of tailings Foundation grouting Foundation cutoffs Clay liners Under-drains Synthetic liners (geomembranes) Geomembrane liners
    19.6.5 Seepage collection and dilution measures Toe drains Pump wells Seepage collection and dilution dams
    19.6.6 Rehabilitation Long term stability and settlement Erosion control Seepage control Return of area to productive use

    20 Monitoring and surveillance of embankment dams
    20.1 What is monitoring and surveillance?
    20.2 Why undertake monitoring and surveillance?
    20.2.1 The objectives
    20.2.2 Is it really necessary?
    20.2.3 Some additional information on embankment dam failures and incidents
    20.2.4 Time for development of internal erosion and piping failure of embankment dams and ease of detection
    20.2.5 The ability of monitoring to detect slope instability
    20.3 What inspections and monitoring is required?
    20.3.1 General principles
    20.3.2 Some examples of well instrumented embankment dams
    20.3.3 Dam safety inspections
    20.4 How is the monitoring done?
    20.4.1 General principles
    20.4.2 Seepage flow measurement and observation
    20.4.3 Surface displacements
    20.4.4 Pore pressures Why and where are pore pressures measured?
    20.4.5 Pore air and pore water pressure Fluctuations of pore pressure with time and the lag in response of instruments Types of instruments and their characteristics
    20.4.6 Should piezometers be installed in the cores of earth and earth and rockfill dams?
    20.4.7 Displacements and deformation Vertical displacements and deformation Horizontal displacements and deformations
    20.4.8 Thermal monitoring of seepage General Distributed fibre optic temperature sensing Thermotic sensors in stand pipes in the dam Infra-red imaging of the downstream face of the dam and foundations
    20.4.9 Use of geophysical methods to detect seepage Self potential Resistivity Other methods

    Appendix A: Methods for estimating the probability of failure by internal erosion and piping
    Subject index


    Robin Fell is Emeritus Professor of Civil Engineering at the University of New South Wales, Australia, and also works as a consultant. He has more than 40 years of experience in geotechnical engineering of dams, landslides and civil and mining projects in Australia and Asia. He has worked on over 100 dams worldwide and has been involved in all aspects of planning, site investigation, design and construction of embankment dams.

    Patrick MacGregor is a Consulting Engineering Geologist with more than 40 years experience in the assessment of geological constraints for major civil engineering projects in a number of countries. He has been involved in dam investigation, design and construction, and particularly worked on hydroelectric developments at all stages from inception to operation.

    David Stapledon spent many years investigating large dam construction sites in various countries. He was a Professor of Engineering Geology at the University of South Australia (1964 -1993) and worked as a Consultant in Engineering Geology, contributing to major dam projects in Australia, New Zealand and South East Asia. He has more than 50 years of experience and was awarded the John Jaeger Memorial Medal for Contributions to Geomechanics in 1995.

    Graeme Bell has been a Consulting Dam Engineer since 1962. His role has varied from providing the full technical input, design management and construction advice for new dams to the preparation of complex structural analyses of existing dams. From 1979, he has acted as an independent reviewer on many dam projects, mainly in Australia, but also in several overseas locations.

    Mark Foster has 20 years of experience in dam engineering and geotechnical engineering. This has involved a wide variety of projects including dam safety reviews, design of dam upgrade projects and dam safety risk assessments for embankment and concrete dams. He has a particular interest in the assessment of piping and internal erosion of embankment dams which was the topic of his doctoral research studies at the University of New South Wales.

    Eleven years after the publication of the first edition of the excellent book Geotechnical Engineering of Dams, the geotechnical and dam engineering community can enjoy reading and analyzing the second edition, completely revised, updated, enlarged and enriched. [...] All chapters are almost equally important and interesting for any dam and geotechnical engineer, but I especially like chapters 8 and 9, dealing with internal erosion, piping and filters at embankment dams and in foundation. Apparently, a great experience and original research knowledge of part of the authors of the book is embedded in these thoroughly executed chapters. I cannot also avoid mentioning chapter 12 – Design of embankment dams to withstand earthquakes – in which an up-to-date review and analysis of this sensitive aspect of embankment dam design is given, still under intensive development.
    Dam builders have always been aware of the fact that dams are firmly bonded to the foundation. But, with this extraordinary book, the bond seems even stronger! I am sure this book will be an unavoidable professional reference and guide in the libraries of all dam and geotechnical engineers. Also, I strongly recommend the book to advanced university students as a textbook, as well as a source of ideas for further research works.

    Ljubomir Tanchev, Professor on dams and hydraulic structures, University of Skopje, Macedonia

    This book fills a lacuna in the available comprehensive literature on Geotechnical Engineering of Dams. […] It covers dimensions not seen in normally available and commonly prescribed textbooks. An intuitive sense of amalgamating both theory and practice is the distinguished and remarkable feature of the book. […]
    A very important and useful aspect of the book is that it covers common errors in the five major aspects of safe dams and provides insight in these aspects by dealing with practical problems and case studies.
    The book very well covers all important geotechnical aspects of dam engineering for civil engineering students at undergraduate as well as at post graduate level and for practitioners. […] Academicians & practicing engineers will be able to sharpen their knowledge with the help of input provided by the book. The book is useful to civil engineers […] working in the area of geotechnical dam engineering and ground improvement.

    Prof. Gautam N. Gandhi, President, Indian Geotechnical Society, New Delhi, Formerly Principal, IDS, Nirma University, India

    The book is an excellent contribution in the area of dam engineering. Dam Engineering has become an important area in providing efficient infrastructure for water supply, power generation as well as resources generation and conservation. The revision of the previous edition is timely and up to date. [...] In summary, the treatise is comprehensive, up-to-date and needs to be studied by scientists and engineers, organizations, professional bodies, policy makers and builders connected with dam engineering.

    Prof. G.L. Sivakumar Babu, Chairman, International Technical Committee on Forensic Geotechnical Engineering ISSMGE / Governor, Region 10, American Society of Civil Engineers, USA / Editor-in Chief, Indian Geotechnical Journal, Department of Civil Engineering, Indian Institute of Science, Bangalore, India