Geotechnical Engineering of Dams: 2nd Edition (Paperback) book cover

Geotechnical Engineering of Dams

2nd Edition

By Robin Fell, Patrick MacGregor, David Stapledon, Graeme Bell, Mark Foster

CRC Press

1,348 pages

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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.

Reviews

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

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

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 of 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

About the Authors

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.

Subject Categories

BISAC Subject Codes/Headings:
TEC009020
TECHNOLOGY & ENGINEERING / Civil / General
TEC009110
TECHNOLOGY & ENGINEERING / Civil / Dams & Reservoirs
TEC063000
TECHNOLOGY & ENGINEERING / Structural