1st Edition

Earthworks Theory to Practice - Design and Construction

By Burt G. Look Copyright 2023
    610 Pages 473 Color Illustrations
    by CRC Press

    Case studies are used to show how theory is applied in practice. In the design and construction process, various models are used – geotechnical, laboratory, analytical, delivery, and economic models as the project is developed from planning to construction. This book explores the use and limitations of these earthwork models to be understood and appropriately applied.

    This book evolved from an earthworks course to practicing engineers over a 10-year period. Theory alone is not enough. Experience alone without relating back to theory can sometimes be misleading if transferred without understanding the fundamentals. The book benefited from the experiences of those many practicing engineers and the author’s experience in multi-disciplinary consulting companies as well as specialist geotechnical companies and government departments.

    The basics of soil, rock and compaction mechanics as applied to field conditions are covered. Material typically not covered in other textbooks, include the applications and limitations of associated "standard" laboratory and field testing. Specific chapters are dedicated to excavation, subgrade and expansive clay assessment and treatment. Useful design practices as well as the development and application of specifications is covered. A specification, test or design in one climatic condition or geology may not apply in another.

    Chapter 1 – Introduction 
    1.1. Introduction 
    1.2. Why an Earthworks book 
    1.3. A short history of earthworks 
    1.4. Ground models 
    Geological model 
    Geotechnical model 
    Earthworks model 
    1.5. Earthworks cost 
    1.6. The business of geotechnical engineering 
    1.7. Case study - Geological model for a deep basement excavation 
    1.8. Summary 
    Chapter 2 – Site Investigation 
    2.1. Influence of the ground 
    2.2. Planning and staging of a site investigation 
    Depth of site investigation 
    Extent of investigation 
    Sampling 
    2.3. Field work of site investigation 
    Deep investigation 
    Shallow investigation and subgrade assessment 
    2.4. Testing variation 
    Shallow foundations 
    Deep foundations 
    Counting blows 
    Energy transfer 
    N-value to strength varies with geology 
    High and low SPT values 
    2.5. Case study 1 – No geotechnical investigation 
    2.6. Case study 2 – Auger and cored drilling 
    2.7. Summary 
    Chapter 3 – Site Safety 
    3.1. Site safety awareness 
    3.2. Failure of trenches 
    Temporary supports and slopes 
    3.3. General safety considerations 
    3.4. Operating plant 
    3.5. Safe work method statement 
    3.6. Case study 1 – Sink hole failure from pile installation 
    3.7. Case study 2 – Incorrect as-constructed services drawings 
    3.8. Case study 3 – Slope failure 
    3.9. Summary 
    Chapter 4 – Phase Relationships and Soil Classification 
    4.1. Soil elements and classification 
    4.2. Phase definitions 
    4.3. Soil types 
    Water retention 
    4.4. Soil classification 
    Gradings 
    Atterberg limits 
    4.5. Engineering use chart 
    4.6. Case study – Gradings pre and post compaction 
    4.7. Summary 
    Chapter 5 – Theory of Compaction 
    5.1. Introduction 
    5.2. Mechanics of densification 
    Theory of compaction 
    Compactive effort 
    Compaction curves for different materials 
    5.3. Strength from compaction 
    5.4. Sample preparation 
    5.5. Field vs laboratory compaction 
    Oversize correction 
    5.6. CBR test 
    5.7. Compactor performance in the field 
    5.8. Case Study 1 – Importance of curing times 
    5.9. Case Study 2 – Representative sampling 
    5.10. Summary 
    Chapter 6 – Soil and Rock Strength 
    6.1. Introduction to soil and rock types 
    6.2. Rock types 
    6.3. Soil types 
    6.4. Types of soil strength 
    Critical strength 
    Residual strength 
    Compaction induced strength 
    6.5. Classification of clay strength 
    6.6. Classification of strength of granular soils 
    Standard penetration test 
    Dynamic cone penetration test 
    Cone penetration test 
    6.7. California bearing ratio 
    Interaction with underlying layer 
    Laboratory vs field conditions 
    CBR soaking 
    CBR from DCP test 
    6.8. Various methods of subgrade investigation 
    Plate load test 
    Dynamic cone penetrometer to estimate modulus 
    LFWD to estimate modulus 
    6.9. Rock properties 
    Rock weathering 
    Rock strength 
    Rock modulus 
    6.10. Degradable materials 
    6.11. Case study 1 – CBR subgrade assessment 
    6.12. Case study 2 – SPT field values 
    6.13. Summary 
    Chapter 7– The Compaction Process 
    7.1. Prequel to compaction 
    7.2. Principles of compaction equipment 
    Number of passes and lift thickness 
    Travel speed 
    7.3. Targeted moisture content 
    Water required for compaction 
    7.4. Productivity of compaction plant 
    7.5. Influence depth 
    7.6. Compaction equipment 
    Small-sized equipment 
    Large-sized equipment 
    Impact compaction 
    7.7. Deep compaction 
    7.8. Case study 1 – Targeted field moisture ratios 
    7.10. Case study 3 – Effect of roller type: Dynamic force monitoring 
    7.11. Summary 
    Chapter 8 – Excavations and Bulking 
    8.1. Introduction 
    8.2. Definition of rock in contract documents 
    8.3. Excavation equipment 
    8.4. Open excavation assessment 
    Excavation assessment based on rock mass rating 
    Excavation assessment based on seismic wave velocities 
    Excavation assessment based on various ratings 
    Excavation assessment based on production rates 
    8.5. Equipment balance 
    Plant output 
    8.6. Confined space excavation assessment 
    Diggability index 
    Trench, shaft, and tunnel excavations in rock 
    8.7. Bulking factors 
    8.8. Case study 1 – Unit weight of excavated material placed as fill 
    8.9. Case study 2 – Variation of material through a cutting 
    8.10. Summary 
    Chapter 9 – Slope Stability in Cuttings and Embankments 
    9.1. Introduction 
    9.2. Causes of slope failure 
    9.3. Quantitative risk analysis 
    Landslides as compared with other hazard events 
    The perception of risk 
    Case study of landslides with varying consequences 
    9.4. Factors of safety 
    Factors of safety for new slopes 
    Factors of safety for existing slopes 
    Factors of safety based on consequences class 
    Factors of safety for dam walls 
    9.5. Typical slopes for cuttings and embankments 
    Rock slopes 
    Rock cut stabilisation measures 
    9.6. Soil erodibility 
    Erodibility hierarchy 
    Erosion control 
    Benching of slopes 
    9.7. Case study 1 - Mechanisms of landslide failures 
    9.8. Case study 2 - Riverbank failure 
    9.9. Case study 3 – Landslide zonation by GIS analysis 
    9.10. Summary 
    Chapter 10 – Expansive Soils 
    10.1. Introduction 
    Pavement design and distress 
    10.2. Cost of damage 
    10.3. Mechanical damage from tree roots 
    10.4. Volume change behaviour 
    Index tests 
    Embankments and cuttings 
    10.5. Calculation of movement using the shrink – swell index 
    10.6. Weighted plasticity index (WPI) for residual soils 
    WPI = PI x % passing the 425-micron sieve 
    10.7. Soil suction and saturation 
    10.8. Relationship of WPI with CBR test 
    10.9. Compaction 
    10.10. Design CBR 
    10.11. Equilibrium moisture content compaction 
    Index parameters which indicate the seasonal changes 
    10.12. Swell pressure tests for assessment of stable zone 
    10.13. Zonal use of expansive clay 
    10.14. Effect of trees on ground movement 
    10.15. Case study 1 – Long-term monitoring of existing embankments 
    Trial embankment 
    Construction monitoring 
    Key considerations 
    10.16. Case study 2 - Effect of desiccation cracks on modulus 
    10.17. Summary 
    Chapter 11 – Subgrades 
    11.1. Introduction 
    11.2. Sampling survey 
    11.3. Subgrade considerations 
    Site investigation vs construction requirements 
    11.4. Analytical proof of subgrade depth 
    Boussinesq analysis 
    Finite element analysis 
    Hertz contact mechanics 
    11.5. Proof rolling for subgrade assessment 
    Tyred equipment for proof rolling tests 
    Rollers for proof rolling tests 
    11.6. Rail track permissible pressure on the formation 
    11.7. Case study - Subgrades for heavy loads 
    11.8. Summary 
    Chapter 12 – Improved Subgrades 
    12.1. Introduction 
    12.2. Remove and replace 
    Design basis for remove and replace 
    12.3. In-situ stabilisation 
    Lime stabilisation 
    Cement stabilisation 
    Soil stabilisation with bitumen 
    12.4. Geosynthetics 
    Geotextiles for separation and reinforcement 
    Establishing geotextile strength class 
    Geotextile strength class for horizontal and vertical placement 
    Establishing geotextile strength class adjacent to walls and slopes 
    Geotextile overlap 
    Geogrids for subgrade improvement 
    Bearing capacity factors using geotextiles 
    Modulus improvements with geosynthetic inclusions 
    Geotextiles as a soil filter 
    12.5. Working platforms 
    Subgrade testing 
    BR470 design considerations 
    Adjacent to a slope 
    Platform maintenance 
    Track bearing pressure 
    Platform material 
    Design alternative using geotextiles
    12.6. Case study 1 - Adjacent to a creek 
    12.7. Case study 2 - Dredged sand subgrade over very soft clays
    Approach
    Track pressure loads
    Geotechnical parameters 
    Risk based analysis
    Acceptable displacement criterion 
    Allowable stress criterion 
    Analysis summary 
    Proof rolling deflections 
    12.8. Case study 3 – Lime stabilisation and a reinforced soil slope 
    12.9. Summary 
    Chapter 13 – Design Considerations
    13.1. Introduction
    13.2. Embankment considerations 
    13.3. Factors of safety for slopes 
    Factors of safety for new and existing slopes
    13.4. Probability of failure
    13.5. Stable slope batters
    13.6. Embankment foundations
    13.7. Foundation movements
    Immediate to total settlements
    Free surface movements for light buildings
    Free surface movements for road pavements
    Tolerable deflection for proof rolling
    Rail track deformations
    Road surface movements on compressible soils
    Differential settlement of reinforced soil structures
    13.8. Design value – risk based
    13.9. Typical CBR values
    13.10. Applying CBR values 
    13.11. Design interface with hydraulics
    13.12. Case study 1 – Back-analysis of a failed slope
    13.13. Case study 2 – Design detailing and analysis input
    13.14. Summary
    Chapter 14 – Construction Considerations
    14.1. Introduction
    14.2. Quality control
    14.3. Specifications 
    Characteristic values 
    Frequency of testing
    Specification development
    Effect of climate and geology
    Effect of traffic
    14.4. Blending
    14.5. Rock specifications for roadway embankment fills
    14.6. Rock durability 
    14.7. Ballast grading 
    14.8. Backfill 
    14.9. Observation and instrumentation 
    14.10. The zero air voids line
    14.11. Compaction specifications
    14.12. Non-density quality control
    14.13. Case study 1 – Uneven rock surface
    14.14. Case study 2 – Earthworks tender considerations 
    14.15. Case study 3 – Spatial variation and blending
    14.16. Summary 
    Abbreviations 
    References 
    Standards publications 
    Other publications 
    Additional reading

    Biography

    Burt G. Look has 40 years professional engineering experience with his early years in structural and civil works before specialising in geotechnics. He obtained his postgraduate degree from Imperial College, London in soil mechanics and engineering seismology. His PhD was obtained from The University of Queensland through part time studies, while working at Queensland Main Roads.

    He has been a consulting geotechnical engineer for most of his career, and most recently a senior principal and director at FSG – Geotechnics and Foundations. He was previously the Global Geotechnical Practice Leader in SKM (now Jacobs), and the Global Geotechnical Group leader at Aurecon. Burt is the 2014 Queensland Professional Engineer of the year and the Australian Geomechanics Society (AGS) Practitioner 2018 – a biennial award. He was awarded the Medal of the Order of Australia (OAM) in 2020.

    He is widely recognised in the areas of earthworks, expansive clays, landslides, risk assessment and site characterisation. He has been a technical advisor and expert witness in these areas. Burt developed and presented "Earthworks"- a course for practicing engineers, and over 1,000 professionals attended to date. Burt has published three geotechnical engineering books and over 90 technical publications focused on industry practice developments within Australia.