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.
