Geotechnical Engineering of Dams  book cover
2nd Edition

Geotechnical Engineering of Dams

ISBN 9781138749344
Published February 20, 2018 by CRC Press
1382 Pages

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Book Description

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.

Table of Contents

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

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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