Contenido Geotechnical Engineering of Dams

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.

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

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

                2.6.3.1 Susceptibility of common minerals to chemical weathering
                2.6.3.2 Susceptibility of rock substances to chemical weathering

      2.6.4 Weathered rock profiles and their development

                2.6.4.1 Climate and vegetation
                2.6.4.2 Rock substance types and defect types and pattern
                2.6.4.3 Time and erosion
                2.6.4.4 Groundwater and topography
                2.6.4.5 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
                 2.9.4.1 Sulphide oxidation effects in rockfill dams – some examples
                 2.9.4.2 Possible effects of sulphide oxidation in rockfill dams
                 2.9.4.3 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
                  2.10.1.1 Reactivated slides
                  2.10.1.2 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
                              2.10.3.1 Talbingo Dam
                              2.10.3.2 Tooma Dam
                              2.10.3.3 Wungong Dam
                              2.10.3.4 Sugarloaf Dam
                              2.10.3.5 Thomson Dam

2.11 Stability of slopes around storages

         2.11.1 Vital slope stability questions for the feasibility and site selection stages
                     2.11.1.1 Most vulnerable existing or proposed project features, and parts of storage area? – Question 1
                     2.11.1.2 Currently active or old dormant landslides? – Questions 2 and 4 to 7
                     2.11.1.3 Areas where first-time landsliding may be induced (Questions 3 to 7)
                     2.11.1.4 What is the likely post failure velocity and travel distance?
                     2.11.1.5 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
                     2.12.5.1 Storages in non-soluble rock areas – assessment of watertightness
                     2.12.5.2 Storages in soluble rock areas – assessment of watertightness
                     2.12.5.3 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
                 3.2.2.1 Flows on land
                 3.2.2.2 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
                 3.4.5.1 Minor faults developed parallel and at acute angles to the foliation
                 3.4.5.2 Kink bands
                 3.4.5.3 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
                 3.7.1.1 Rock masses composed of dense, fine grained rock substances comprising more than 90% of carbonate (usually Category O)
                 3.7.1.2 Rock masses composed of dense fine grained rock substance containing 10% to 90% of carbonate (usually Category O)
                 3.7.1.3 Rock masses composed of porous, low density carbonate rock substance (usually Category Y)
       3.7.2 Watertightness of dam foundations
                 3.7.2.1 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
                 3.7.6.1 Category O carbonate rocks
                 3.7.6.2 Category Y carbonate rocks
       3.7.7 Potential problems with filters’ composed of carbonate rocks
                 3.7.7.1 Category O carbonate rocks
                 3.7.7.2 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
                  3.10.1.1 Scree and talus
                  3.10.1.2 Slopewash soils
                  3.10.1.3 Landslide debris
      3.10.2 Properties of colluvial soils
                  3.10.2.1 Scree and talus
                  3.10.2.2 Slopewash
                  3.10.2.3 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
                    3.12.2.1 Properties of till materials
                    3.12.2.2 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
                 4.1.2.1 Questions relating to rock and soil types, climate and topography
                 4.1.2.2 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
                4.4.1.1 Objectives
                4.4.1.2 Activities
      4.4.2 Studies at intermediate and detailed scales
                4.4.2.1 Objectives
                4.4.2.2 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
               5.2.2.1 Coverage
               5.2.2.2 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
                 5.4.2.1 Regional mapping
                 5.4.2.2 Geotechnical mapping
5.5 Geophysical methods, surface and downhole
       5.5.1 Surface geophysical methods
                 5.5.1.1 Seismic refraction
                 5.5.1.2 Self potential
                 5.5.1.3 Electrical resistivity
                 5.5.1.4 Electromagnetic conductivity
                 5.5.1.5 Magnetic
                 5.5.1.6 Microgravity
                 5.5.1.7 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
                  5.11.2.1 Borehole orientation
                  5.11.2.2 Borehole impression packer
                  5.11.2.3 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
                      5.14.4.1 Packers
                      5.14.4.2 Water supply system
                      5.14.4.3 Selection of test pressures
         5.14.5 Test procedure
                     5.14.5.1 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
                 6.1.4.1 Triaxial test
                 6.1.4.2 Direct shear test
                 6.1.4.3 Ring shear test
                 6.1.4.4 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
                 6.1.6.1 Estimation of undrained strength from OCR
                 6.1.6.2 Estimation of undrained strength from effective stress shear parameters
       6.1.7 Estimation of the undrained strength of cohesive soils from in situ tests
                 6.1.7.1 Cone Penetration and Piezocone Tests
                 6.1.7.2 Vane shear
                 6.1.7.3 Self Boring Pressuremeter
       6.1.8 Shear strength of fissured soils
                 6.1.8.1 The nature of fissuring, and how to assess the shear strength
                 6.1.8.2 Triaxial testing of fissured soils
       6.1.9 Estimation of the effective friction angle of granular soils
                6.1.9.1 Methods usually adopted
                6.1.9.2 In situ tests
                6.1.9.3 Laboratory tests
                6.1.9.4 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
                6.3.1.1 Within the foundation
                6.3.1.2 Within the embankment
       6.3.2 Methods of estimating the compressibility of earthfill, filters and rockfill
                6.3.2.1 Using data from the performance of other dams – earthfill
                6.3.2.2 Using data from the performance of other dams – rockfill
                6.3.2.3 In situ testing
                6.3.2.4 Laboratory testing
                6.3.2.5 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
                 6.4.3.1 Oedometer and triaxial consolidation test
                 6.4.3.2 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
                 7.2.2.1 Primary bonds
                 7.2.2.2 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
                 7.6.1.1 Emerson class number
                 7.6.1.2 Soil Conservation Service test
                 7.6.1.3 Pinhole dispersion classification
                 7.6.1.4 Chemical tests
                 7.6.1.5 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
                 7.7.2.1 Provide properly designed and constructed filters
                 7.7.2.2 Proper compaction of the soil
                 7.7.2.3 Careful detailing of pipes or conduits through the embankment
                 7.7.2.4 Lime or gypsum modification of the soil
                 7.7.2.5 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
                 8.3.2.1 Cracking and hydraulic fracture due to cross valley differential settlement of the core
                 8.3.2.2 Cracking and hydraulic fracture due to cross valley arching
                 8.3.2.3 Cracking and hydraulic fracture due to differential settlement in the foundation under the core
                 8.3.2.4 Cracking and hydraulic fracture due to small scale irregularities in the foundation profile under the core
                 8.3.2.5 Cracking due to lack of support for the core by the shoulders of the embankment
                 8.3.2.6 Cracking and hydraulic fracture due to arching of the core onto the shoulders of the embankment
                 8.3.2.7 Crack or gap adjacent to a spillway or abutment walls and where concrete dams abut embankment dams
                 8.3.2.8 Crack or hydraulic fracture in poorly compacted layers in the embankment
                 8.3.2.9 Internal erosion associated with conduits embedded in the embankment
                 8.3.2.10 Cracking due to desiccation
                 8.3.2.11 Transverse cracking caused by settlement during earthquakes
                 8.3.2.12 Cracking or high permeability layers due to freezing
                 8.3.2.13 Internal erosion initiated by the effects animal burrows and vegetation
                 8.3.2.14 Relative importance of conduits, spillway walls cracking mechanisms, and poorly compacted zones
       8.3.3 Estimation of crack width and depth of cracking
                 8.3.3.1 Cracking due to differential settlement, adjacent walls
                 8.3.3.2 Cracks formed by collapse settlement of poorly compacted soil
       8.3.4 The mechanics of erosion in concentrated leaks
                 8.3.4.1 The procedure for assessing whether erosion will initiate
                 8.3.4.2 The estimation of hydraulic shear stresses in cracks and pipes
                 8.3.4.3 Erosion properties of soils in the core of embankment dams – basic principles
                 8.3.4.4 Effect of degree of saturation of the soil
                 8.3.4.5 Effect of the testing method on the critical shear stress to initiate erosion (τc) and the erosion rate index
                 8.3.4.6 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
                 8.4.3.1 Empirical rules for estimating a factor of safety
                 8.4.3.2 Terzaghi and Peck (1948)
                 8.4.3.3 Sellmeijer and co-workers at Deltares method
                 8.4.3.4 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
                 8.5.2.1 General requirements
                 8.5.2.2 Some methods for assessing whether a soil is internally unstable
                 8.5.2.3 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
                 8.5.5.1 Need for project specific laboratory tests
                 8.5.5.2 Do not use “average’’ soil gradations
                 8.5.5.3 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
                 8.6.2.1 Non plastic sand below a coarse soil layer
                 8.6.2.2 Non plastic silt and clay (particles <75μm) below a coarse layer
                 8.6.2.3 Non-plastic silt above a coarse soil layer
                 8.6.2.4 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
                 8.8.4.1 Internal erosion in the embankment
                 8.8.4.2 Internal erosion through the foundation
                 8.8.4.3 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
                    8.12.2.1 Geometric model
                    8.12.2.2 Geological model of the foundation
                    8.12.2.3 Geotechnical model of the embankment and foundations
                    8.12.2.4 Hydraulic or seepage model
                    8.12.2.5 Stress state in the dam and its foundation
                    8.12.2.6 General comments
        8.12.3 Loading conditions
                    8.12.3.1 Reservoir level loading
                    8.12.3.2 Earthquake loading
                    8.12.4 Potential Failure Modes Analysis (PFMA)
                    8.12.5 Screening of potential failure modes
                                8.12.5.1 Screening of PFM on the zoning of the dam and the                                                                properties the  core of the embankment
                                8.12.5.2 Screening of PFM on foundation geology and properties
                                8.12.5.3 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
                                8.12.6.1 Some general principles
                                8.12.6.2 Summary of how to estimate conditional probabilities within the                                          event tree
                                8.12.6.3 Ways in which the safety of the dam against internal erosion and                                         piping can be considered
                                8.12.6.4 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
                 9.1.4.1 Notation
                 9.1.4.2 Filtering concepts
                 9.1.4.3 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
                 9.2.1.1 Original USBR method
                 9.2.1.2 Sherard and Dunnigan method
                 9.2.1.3 Foster and Fell method
                 9.2.1.4 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
                  9.2.3.1 Delgardo and co-workers
                  9.2.3.2 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
                  9.2.5.1 Filters upstream of the dam core
                  9.2.5.2 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
                  9.2.7.1 Pipe drains
                  9.2.7.2 Pressure relief well screens
        9.2.8 Other factors affecting filter design and performance
                  9.2.8.1 Criteria to assess internal instability or suffusion
                  9.2.8.2 Segregation
                  9.2.8.3 Ability of the filter to hold a crack
                  9.2.8.4 Permeability
                  9.2.8.5 “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
                   9.3.3.1 Internal erosion in the embankment, from the embankment into the foundation or into openings in conduits passing                                         through the embankment
                   9.3.3.2 Internal erosion in the foundation
                   9.3.3.3 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
                   9.3.4.1 General principles
                   9.3.4.2 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
                   9.4.2.1 Standard tests for durability and particle shape
                   9.4.2.2 Possible effects if carbonate rocks are used as filter materials
                   9.4.2.3 Effects if rocks containing sulphide minerals are used as filter materials
                   9.4.2.4 Other investigations for filter materials
         9.4.3 Contractual difficulties associated with gradation and durability of filters
                   9.4.3.1 Fines content
                   9.4.3.2 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
                   9.5.1.1 Some general principles
                   9.5.1.2 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
                 9.6.2.1 General requirements
                 9.6.2.2 Filtering requirement
                 9.6.2.3 Clogging and blinding resistance
                 9.6.2.4 Permeability requirement
                 9.6.2.5 Durability or “survivability’’ requirement
                 9.6.2.6 Use of geotextile filters in dams
                 9.6.2.7 Construction factors
                 9.6.2.8 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
                    10.3.2.1 Zoned earthfill dams
                    10.3.2.2 Earthfill dams with horizontal and vertical drains
                    10.3.2.3 Central core earth and rockfill dams
                    10.3.2.4 Sloping upstream core earth and rockfill dam
                    10.3.2.5 Concrete face rockfill dams

10.4 Selection of embankment type
         10.4.1 Availability of construction materials
                     10.4.1.1 Earthfill
                     10.4.1.2 Rockfill
                     10.4.1.3 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
                    11.3.1.1 Peak, residual or fully softened strength in clay soils?
                    11.3.1.2 Selection of design parameters in clay soils
                    11.3.1.3 Selection of design parameters – granular soils and rockfill
        11.3.2 Undrained, total stress parameters
                    11.3.2.1 Triaxial compression, extension or direct simple shear strength
                    11.3.2.2 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
                    11.4.1.1 Steady state pore pressures
                    11.4.1.2 Pore pressures under flood conditions
        11.4.2 Pore pressures during construction and analysis of stability at the end of construction
                   11.4.2.1 Some general principles
                   11.4.2.2 Estimation of construction pore pressures by Skempton (1954) method
                   11.4.2.3 Estimation of construction pore pressures from drained and specified undrained strengths
                   11.4.2.4 Estimation of pore pressures using advanced theory of partially saturated soil
                   11.4.2.5 Undrained strength analysis
                   11.4.2.6 Summing up
        11.4.3 Drawdown pore pressures and the analysis of stability under drawdown conditions
                   11.4.3.1 Some general issues
                   11.4.3.2 Estimation of drawdown pore pressures, excluding the effects of shear-induced pore pressures
                   11.4.3.3 Methods for assessment of the stability under drawdown conditions
                   11.4.3.4 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
                    12.3.2.1 Probabilistic approach
                    12.3.2.2 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
                    12.3.4.1 Deterministic approach
                    12.3.4.2 Risk based approach
                    12.3.4.3 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
                    12.5.1.1 Definitions
                    12.5.1.2 Some consideration of the mechanics of liquefaction of granular soils
                    12.5.1.3 Suggested flow chart for evaluation of soil liquefaction
        12.5.2 Soils susceptible to liquefaction
                    12.5.2.1 Methods based on soil classification and in situ moisture content
                    12.5.2.2 Discussion and recommended approach
                    12.5.2.3 Methods based on geology and age of the deposit
        12.5.3 The “simplified procedure’’ for assessing liquefaction resistance of a soil
                    12.5.3.1 Background to the simplified method
                    12.5.3.2 Discussion of differences between the Youd et al. (2001), Seed et al. (2003) and Idriss and Boulanger (2008) methods
                    12.5.3.3 The simplified method – outline
                    12.5.3.4 Evaluation of Cyclic Stress Ratio (CSR)
                    12.5.3.5 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
                    12.5.3.6 Evaluation of the Cyclic Resistance Ratio for M7.5 earthquake (CRR7.5) from Cone Penetration Tests using the Idriss and Boulanger (2008) method
                    12.5.3.7 Evaluation of Cyclic Resistance Ratio for M7.5 earthquake (CRR7.5) from shear wave velocity using the Andrus and Stokoe (2000) method
                    12.5.3.8 Earthquake magnitude scaling factors and factor of safety against liquefaction
                    12.5.3.9 Corrections for overburden stress and static shear stress
                    12.5.3.10 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
                    12.6.3.1 “Critical State’’ based methods
                    12.6.3.2 Normalized strength ratio methods
                    12.6.3.3 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
                    12.6.6.1 Saturated potentially liquefiable soils
                    12.6.6.2 Cyclic softening in clays and plastic silts
                    12.6.6.3 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
                    12.7.5.1 USACE method
                    12.7.5.2 Hynes-Griffin and Franklin (1984) pseudo-static seismic coefficient method
        12.7.6 Empirical database methods
                    12.7.6.1 Swaisgood (1998, 2003) empirical method for estimating crest settlements
                    12.7.6.2 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
                    12.7.7.1 General principles
                    12.7.7.2 Makdisi and Seed (1978) method
                    12.7.7.3 Bray and Travasarou (2007) method
        12.7.8 Advanced numerical methods for estimating deformations during and post earthquake for non-liquefied and liquefied conditions
                    12.7.8.1 Total stress codes
                    12.7.8.2 Effective stress codes
                    12.7.8.3 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
                    13.1.2.1 New embankment dams
                    13.1.2.2 Existing embankment dams
                    13.1.2.3 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
                    13.1.4.1 Fetch
                    13.1.4.2 Design wind
                    13.1.4.3 Wave height
                    13.1.4.4 Wave length and wave period
                    13.1.4.5 Wave run-up
                    13.1.4.6 Wind set-up
13.2 Slope protection
         13.2.1 Upstream slope protection
                    13.2.1.1 General requirements
                    13.2.1.2 Sizing and layer thickness
                    13.2.1.3 Selection of design wind speed and acceptable damage
                    13.2.1.4 Rock quality and quarrying
                    13.2.1.5 Design of filters under rip-rap
                    13.2.1.6 Use of soil cement and shotcrete for upstream slope protection
        13.2.2 Downstream slope protection
                    13.2.2.1 General requirements
                    13.2.2.2 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
                     15.2.2.1 General requirements
                     15.2.2.2 Layer thickness and compaction
                     15.2.2.3 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
                     15.2.4.1 Estimation of the secant modulus Erc
                     15.2.4.2 Estimation of the first filling ‘pseudo modulus’ Erf
                     15.2.4.3 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
                     15.3.2.1 Face slab thickness
                     15.3.2.2 Reinforcement
                     15.3.2.3 Vertical and horizontal joints
         15.3.3 Perimetric joint
                     15.3.3.1 General requirements
                     15.3.3.2 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
                   16.3.2.1 General requirements
                   16.3.2.2 Shear strength of clean discontinuities
                   16.3.2.3 Shear strength of infilled joints and seams showing evidence of previous displacement
                   16.3.2.4 Shear strength of thick infilled joints, seams or extremely weathered beds with no previous displacement
                   16.3.2.5 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
                    16.4.2.1 Background to the data
                    16.4.2.2 Tensile strength of concrete and lift joints
                    16.4.2.3 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
                     16.6.2.1 Effects of geological features and deformations on foundation uplift pressures
                     16.6.2.2 Analysis of EPRI (1992) uplift data
                     16.6.2.3 Design of drains
                     16.6.2.4 Hydro-dynamic forces
                     16.6.2.5 Aprons
                     16.6.2.6 ‘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
                     16.9.3.1 General
                     16.9.3.2 The Westergaard pseudo-static method
                     16.9.3.3 The Fenves-Chopra refined pseudo-static method
                     16.9.3.4 The US Corps of engineers method
                     16.9.3.5 Finite Element Method (FEM)
                     16.9.3.6 Design earthquake input motion
                     16.9.3.7 Should vertical ground motion be included?
                     16.9.3.8 Reservoir level variation
                     16.9.3.9 What do the results of analyses mean?
                     16.9.3.10 Post-earthquake analyses
                     16.9.3.11 Dams on rock foundations with potentially deep-seated failure mechanisms
                     16.9.3.12 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
                     17.2.1.1 Rock foundation
                     17.2.1.2 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
                     18.2.3.1 The cement and additives used for grouting
                     18.2.3.2 Water cement ratio
                     18.2.3.3 Rheological properties of grout
                     18.2.3.4 High, medium and low mobility grouts
                     18.2.3.5 Field quality control testing of grouts
                     18.2.3.6 Grout pressure
                     18.2.3.7 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
                  19.2.3.1 General
                  19.2.3.2 Particle size
 19.2.3.3 Mineralogy
19.2.3.4 Dry density and void ratio
19.2.3.5 Permeability
19.2.3.6 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
                     19.4.6.1 Drained shear strength
                     19.4.6.2 Undrained shear strength
19.5 Methods of construction of tailings dams
         19.5.1 General
         19.5.2 Construction using tailings
                     19.5.2.1 Upstream method
                     19.5.2.2 Downstream method
                     19.5.2.3 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
                     19.5.5.1 Tailings placement
                     19.5.5.2 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
                     19.5.7.1 Conventional dams and downstream construction
                     19.5.7.2 Upstream construction
                     19.5.8 Storage layout
                     19.5.9 Other disposal methods
                                 19.5.9.1 Thickened discharge or Robinsky method
                                 19.5.9.2 Co-disposal
                                 19.5.9.3 Paste disposal
                                 19.5.9.4 Belt filtration
                                 19.5.9.5 Disposal into open cut and underground mine workings
                                 19.5.9.6 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
                                 19.6.4.1 Controlled placement of tailings
                                 19.6.4.2 Foundation grouting
                                 19.6.4.3 Foundation cutoffs
                                 19.6.4.4 Clay liners
                                 19.6.4.5 Under-drains
                                 19.6.4.6 Synthetic liners (geomembranes)
                                 19.6.4.7 Geomembrane liners
                      19.6.5 Seepage collection and dilution measures
                                  19.6.5.1 Toe drains
                                  19.6.5.2 Pump wells
                                  19.6.5.3 Seepage collection and dilution dams
                      19.6.6 Rehabilitation
                                  19.6.6.1 Long term stability and settlement
                                  19.6.6.2 Erosion control
                                  19.6.6.3 Seepage control
                                  19.6.6.4 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
                  20.4.4.1 Why and where are pore pressures measured?
         20.4.5 Pore air and pore water pressure
                  20.4.5.1 Fluctuations of pore pressure with time and the lag in response of instruments
                  20.4.5.2 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
                  20.4.7.1 Vertical displacements and deformation
                  20.4.7.2 Horizontal displacements and deformations
         20.4.8 Thermal monitoring of seepage
                  20.4.8.1 General
                  20.4.8.2 Distributed fibre optic temperature sensing
                  20.4.8.3 Thermotic sensors in stand pipes in the dam
                  20.4.8.4 Infra-red imaging of the downstream face of the dam and foundations
                  20.4.9 Use of geophysical methods to detect seepage
                               20.4.9.1 Self potential
                               20.4.9.2 Resistivity
                               20.4.9.3 Other methods
References

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

Subject index