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.
Author(s): Burt G. Look
Publisher: CRC Press/Balkema
Year: 2022
Language: English
Pages: 610
City: Leiden
Cover
Half Title
Title Page
Copyright Page
Table of Contents
Preface
1 Introduction
1.1 Introduction
1.2 Why an earthworks book
1.3 A short history of earthworks
1.4 Ground models
1.4.1 Geological model
1.4.2 Geotechnical model
1.4.3 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
2 Site investigation
2.1 Influence of the ground
2.2 Planning and staging of a SI
2.2.1 Depth of SI
2.2.2 Extent of investigation
2.2.3 Sampling
2.3 Field work of SI
2.3.1 Deep investigation
2.3.2 Shallow investigation and subgrade assessment
2.4 Testing variation
2.4.1 Shallow foundations
2.4.2 Deep foundations
2.4.3 Counting blows
2.4.4 Energy transfer
2.4.5 N-value strength varies with geology
2.4.6 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
3 Site safety
3.1 Site-safety awareness
3.2 Failure of trenches
3.2.1 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 failures
3.9 Summary
4 Phase relationships and soil classification
4.1 Soil elements and classification
4.2 Phase definitions
4.3 Soil types
4.3.1 Water retention
4.4 Soil classification
4.4.1 Gradings
4.4.2 Atterberg limits
4.5 Engineering use chart
4.6 Case study – Gradings pre and post compaction
4.7 Summary
5 Theory of compaction
5.1 Introduction
5.2 Mechanics of densification
5.2.1 Theory of compaction
5.2.2 Compactive effort
5.2.3 Compaction curves for different materials
5.3 Strength from compaction
5.4 Sample preparation
5.5 Field versus laboratory compaction
5.5.1 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
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
6.4.1 Critical strength
6.4.2 Residual strength
6.4.3 Compaction induced strength
6.5 Classification of clay strength
6.6 Classification of strength of granular soils
6.6.1 Standard penetration test
6.6.2 Dynamic cone penetration test
6.6.3 Cone penetration test
6.7 California bearing ratio
6.7.1 Interaction with underlying layer
6.7.2 Laboratory versus field conditions
6.7.3 CBR soaking
6.7.4 CBR from DCP test
6.8 Various methods of subgrade investigation
6.8.1 Plate load test
6.8.2 DCP to estimate modulus
6.8.3 LFWD to estimate modulus
6.9 Rock properties
6.9.1 Rock weathering
6.9.2 Rock strength
6.9.3 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
7 The compaction process
7.1 Prequel to compaction
7.2 Principles of compaction equipment
7.2.1 Number of passes and lift thickness
7.2.2 Travel speed
7.3 Targeted moisture content
7.3.1 Water required for compaction
7.4 Productivity of compaction plant
7.5 Influence depth
7.6 Compaction equipment
7.6.1 Small-sized equipment
7.6.2 Large-sized equipment
7.6.3 Impact compaction
7.7 Deep compaction
7.8 Case study 1 – Targeted field moisture ratios
7.9 Case study 2 – Laboratory testing variation
7.10 Case study 3 – Effect of roller type: dynamic force monitoring
7.11 Summary
8 Excavations and bulking
8.1 Introduction
8.2 Definition of rock in contract documents
8.3 Excavation equipment
8.4 Open excavation assessment
8.4.1 Excavation assessment based on rock mass rating
8.4.2 Excavation assessment based on seismic wave velocities
8.4.3 Excavation assessment based on various ratings
8.4.4 Excavation assessment based on production rates
8.5 Equipment balance
8.5.1 Plant output
8.6 Confined space excavation assessment
8.6.1 Diggability index
8.6.2 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
9 Slope stability in cuttings and embankments
9.1 Introduction
9.2 Causes of slope failure
9.3 Quantitative risk analysis
9.3.1 Landslides as compared with other hazard events
9.3.2 The perception of risk
9.3.3 Case study of landslides with varying consequences
9.4 Factors of safety
9.4.1 Factors of safety for new slopes
9.4.2 Factors of safety for existing slopes
9.4.3 Factors of safety based on consequences class
9.4.4 Factors of safety for dam walls
9.5 Typical slopes for cuttings and embankments
9.5.1 Rock slopes
9.5.2 Rock cut stabilisation measures
9.6 Soil erodibility
9.6.1 Erodibility hierarchy
9.6.2 Erosion control
9.6.3 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
10 Expansive soils
10.1 Introduction
10.1.1 Pavement design and distress
10.2 Cost of damage
10.3 Mechanical damage from tree roots
10.4 Volume change behaviour
10.4.1 Index tests
10.4.2 Embankments and cuttings
10.5 Calculation of movement using the shrink – swell index
10.6 Weighted plasticity index (WPI) for residual soils
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
10.11.1 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
10.15.1 Trial embankment
10.15.2 Construction monitoring
10.15.3 Key considerations
10.16 Case study 2 – Effect of desiccation cracks on modulus
10.17 Summary
11 Subgrades
11.1 Introduction
11.2 Sampling survey
11.3 Subgrade considerations
11.3.1 Site investigation versus construction requirements
11.4 Analytical proof of subgrade depth
11.4.1 Boussinesq analysis
11.4.2 Finite element analysis
11.4.3 Hertz contact mechanics
11.5 Proof rolling for subgrade assessment
11.5.1 Tyred equipment for proof rolling tests
11.5.2 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
12 Improved subgrades
12.1 Introduction
12.2 Remove and replace
12.2.1 Design basis for R&R
12.3 In-situ stabilisation
12.3.1 Lime stabilisation
12.3.2 Cement stabilisation
12.3.3 Soil stabilisation with bitumen
12.4 Geosynthetics
12.4.1 Geotextiles for separation and reinforcement
12.4.2 Establishing geotextile strength class
12.4.3 Geotextile strength class for horizontal and vertical placement
12.4.4 Establishing geotextile strength class adjacent to walls and slopes
12.4.5 Geotextile overlap
12.4.6 Geogrids for subgrade improvement
12.4.7 Bearing capacity factors using geotextiles
12.4.8 Modulus improvements with geosynthetic inclusions
12.4.9 Geotextiles as a soil filter
12.5 Working platforms
12.5.1 Subgrade testing
12.5.2 BR470 design considerations
12.5.3 Adjacent to a slope
12.5.4 Platform maintenance
12.5.5 Track bearing pressure
12.5.6 Platform material
12.5.7 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
12.7.1 Approach
12.7.2 Track pressure loads
12.7.3 Geotechnical parameters
12.7.4 Risk based analysis
12.7.5 Acceptable displacement criterion
12.7.6 Allowable stress criterion
12.7.7 Analysis summary
12.7.8 Proof rolling deflections
12.8 Case study 3 – Lime stabilisation and a reinforced soil slope
12.9 Summary
13 Design considerations
13.1 Introduction
13.2 Embankment considerations
13.3 Factors of safety for slopes
13.3.1 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
13.7.1 Immediate to total settlements
13.7.2 Free surface movements for light buildings
13.7.3 Free surface movements for road pavements
13.7.4 Tolerable deflection for proof rolling
13.7.5 Rail track deformations
13.7.6 Road surface movements on compressible soils
13.7.7 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
14 Construction considerations
14.1 Introduction
14.2 Quality control
14.3 Specifications
14.3.1 Characteristic values
14.3.2 Frequency of testing
14.3.3 Specification development
14.3.4 Effect of climate and geology
14.3.5 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 for buried pipes
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
Permissions
Abbreviations
References
Index
