Advanced Unsaturated Soil Mechanics: Theory and Applications

Cover
Half Title
Title Page
Copyright Page
Table of Contents
Preface to the Second Edition
About the Authors
Acknowledgements
Notations
Nomenclature
Chapter 1 Introduction
	Overview
		The Vadose Zone
		Climate Changes and the Vadose Zone
		Some Common Unsaturated Soils
		Definitions of Suctions
		Stress State Variables
		The Stress State Variable for Saturated Soil
		Possible Sets of Stress State Variables for Unsaturated Soil
		Summary
	Cavitation
		Overview
		Definitions
		Cavitation Inception and Nuclei
		Physics of Pore Water Under Tension in Unsaturated Soils
		Avoiding Cavitation
Chapter 2 Measurement and Control of Suction
	Suction Measuring Devices (Fredlund and Rahardjo, 1993; Ridley and Wray, 1996; Feng and Fredlund, 2003)
		Overview
		Psychrometer
			Thermistor/transistor Psychrometers
			Thermocouple Psychrometer
		The Filter Paper Method
		Porous Block (E.g., Gypsum Block)
		Thermal Conductivity Sensor (Feng and Fredlund, 2003)
		Suction Plate and Pressure Plate (Ridley and Wray, 1996)
		Jet-fill Tensiometer
		Mercury Manometer
		Vacuum Gauge
		Pressure Transducer
		Small Tip Tensiometer
		High Suction Tensiometer Probe
		Squeezing Technique
		Summary
	Suction Control and Measurement Methods (Ng and Chen, 2005, 2006; Ng Et Al., 2007)
		Overview
		Axis-translation Technique
			Working Principle
			Applications
		Osmotic Technique
			Working Principle
			Applications
			Advantages and Limitations
		Humidity Control Techniques
			Working Principle
			Applications
			Advantages and Limitations
		Influence of Suction Equalisation
	Comparisons of Different Suction Control Techniques (Ng Et Al., 2007; Ng Et Al., 2015a)
		Introduction
		Theoretical Considerations of Soil Moisture Transfer
		Water Retention Curves Determined Using Different Suction Control Techniques
		Summary
Chapter 3 Retention Characteristics and Permeability Functions for Water and Gas Flows
	Introduction (Ng and Shi, 1998)
	Soil-water Characteristic Curve (SWCC) and Water Permeability Function (Fredlund Et Al., 2001a, 2002)
		Introduction
		Descriptions of Water Content
		Terminology Used to Quantify a WRC
		Mathematical Forms of SWCC Or WRC
	A New and Simple Model for SDSWCC Or SDWRC (Zhou and Ng, 2014)
		Introduction
		Development of a New Water Retention Model
			Predictability of the New Model
		Summary
	Laboratory Measurements of Drying and Wetting Stress-Dependent Permeability Functions (Ng and Leung, 2012b)
		Theoretical Consideration
		Design of the Apparatus and Instrumentation
		Experimental Results
			Permeability-matric Suction Relationship, K(ψ)
			Permeability-volumetric Water Content Relationship, K(θw)
		Summary
	A Field Study of SDSWCC and Permeability Function (Ng Et Al., 2011)
		Introduction
		The Test Site and Soil Properties
		Instrumentation and Testing Procedures
		Observed Field Performance
			Distributions of Pore-Water Pressure and Volumetric Water Content With Depth
			In Situ SDSWCCs
			Comparisons Between Field and Laboratory SDSWCCs
			Comparisons Between Field-Measured SDSWCCs and Predictions From PSDs
			Comparisons Between Field-Measured Permeability Functions and Predictions From PSDs
		Summary
	Gas Breakthrough and Emission Through Landfill Final Cover (Ng Et Al., 2015b)
		Introduction
		Theoretical Considerations
		Test Program
		Experimental Apparatus and Instrumentation
		Testing Soil and Sample Preparation
		Test Procedures
		Experimental Results
			Gas Breakthrough Pressure at Different Degrees of Saturation
			Influence of Clay Thickness On Gas Breakthrough Pressure
			Gas Emission Rates at Different Degrees of Saturation
			Influence of Clay Thickness On Gas Emission Rate
		Summary
	Numerical Investigation of Gas Emission From Three Types of Landfill Covers Under Dry Weather Conditions (Ng Et Al., 2015b, C; Ng Et Al., 2016b)
		Introduction
		Working Principle of the Alternative Three-Layer Capillary Barrier Cover
		Numerical Modelling
			Numerical Parametric Scheme
			Finite Element Software and Mesh
			Material Properties
			Numerical Simulation Procedure
		Computed Results
			Variations of Pore-Water Pressure
			Variations of Pore-Air Pressure
			Variations of Gas Emission Rate
			Distribution of Gas Emission Rate
		Summary
	Gas Permeability of Biochar-Amended Clay (Wong Et Al., 2016)
		Introduction
		Materials and Methods
			Preparation of Biochar
			Measurements of Gas Permeability
		Results and Discussion
		Summary
	Influence of Biopolymer On Gas Permeability (Ng Et Al., 2020c)
		Introduction
		Material and Methods
			Test Program
			Soil and Biopolymers
		Results and Discussion
			Reducing the Gas Permeability at Different Degrees of Compaction (DOC) Using Biopolymers
			Effects of Compaction Water Content On the Gas Permeability With and Without Biopolymers
		Summary
	Effects of Grass Roots On Gas Permeability (Ni and Ng, 2019)
		Introduction
		Materials and Methods
		Interpretation of Test Results
		Summary
	Effects of Biofilm On Gas Permeability (Ng Et Al., 2019b)
		Introduction
		Materials and Methods
		Interpretation of Test Results
		Summary
Chapter 4 Shear Strength and Behaviour
	Extended Mohr–Coulomb Failure Criterion (Fredlund and Rahardjo, 1993)
		Relationships Between Fb and .
	Comparisons of Axis-Translation and Osmotic Techniques for Shear Testing of Unsaturated Soils (Ng Et Al., 2007)
		Introduction
		Testing Equipment
		Testing Material and Specimen Preparation
		Testing Programme
		Testing Procedures
		Test Results From Using the Axis-Translation Technique
		Test Results From Using the Osmotic Control Technique
		Comparison Between Test Results From the Axis-Translation and Osmotic Control Techniques
		Summary
	Effects of Soil Suction On the Dilatancy of an Unsaturated Soil (Ng and Zhou, 2005)
		Introduction
		Soil Type and Test Procedures
		Evolution of Dilatancy During Shear
		Stress-dilatancy Relationship
		Maximum Dilatancy
		Summary
	Shear Strength Characteristics of Compacted Loess at High Suctions (Ng Et Al., 2017a)
		Introduction
		Test Apparatus and Measuring Devices
		Soil Type and Its Water Retention and Compression Behaviour
			Shear Strength and Shear-Induced Volume Change
			Dilatancy
			Significance of Suction
		Summary
	Effects of Microstructure On Dilatancy (Ng Et Al., 2020b)
		Introduction
		Pore-size Distributions of Recompacted and Natural Loess Specimens
		Significance of Macrovoid Ratio
		Summary
	Comparisons of the Shear Strength of Weathered Lateritic, Granitic and Volcanic Soils: Compressibility and Shear Strength (Ng Et Al., 2019c)
		Introduction
		Soil Types and Grain Size Distribution
		Mineralogy, Chemical and Microstructure Analysis
			Isotropic Compression Behaviour
		Stress-strain Relationship During Shearing
			Soil Dilatancy
			Critical State Shear Strength
		Summary
Chapter 5 Shear Stiffness and Damping Ratio
	Overview
	Anisotropic Shear Stiffness at Very Small Strains (Ng and Yung, 2008)
		Introduction
		Theoretical Considerations
		Testing Apparatus and Measuring Devices
		Soil Types and Test Specimen Preparation
		Test Programme and Procedures
		Interpretations of Experimental Results
			Effects of Changes in Soil Suction and Net Mean Stress On Void Ratio
			Relationships Between Shear Wave Velocities (Vs(vh), Vs(hv), Vs(hh)) and Matric Suction
			Influence of Suction On the Degree of Fabric Anisotropy
			Influence of Net Mean Stress On the Degree of Anisotropy
		Summary
	Effects of Current Suction Ratio and Recent Suction History On Shear Stiffness (Ng and Xu, 2012)
		Introduction
		Theoretical Considerations
		Experimental Study
		Interpretations of Test Results
			Effects of Suction Magnitude On Small-Strain Shear Behaviour
			Effects of Current Suction Ratio On Small-Strain Shear Behaviour
			Effect of Direction of Recent Suction Path On Small-Strain Shear Behaviour
			Effect of Magnitude of Recent Suction Path On Small-Strain Shear Behaviour
		Summary
	Effects of Wetting-Drying and Stress Ratio On Anisotropic Stiffness (Ng Et Al., 2009)
		Introduction
		Interpretations of Experimental Results
			Variations in Axial and Radial Strains During Drying and Wetting Tests
			Variations in Shear Moduli During Drying and Wetting Tests
			Comparison Between Shear Moduli Determined in Drying and Wetting Tests and Isotropic Compression Tests
			Variations in the Degree of Stiffness Anisotropy During Drying and Wetting Tests
		Summary
	Resilient Modulus Under Cyclic Shearing (Ng Et Al., 2013)
		Introduction
		Theoretical Considerations
		Experimental Study
		Interpretations of Experimental Results
			Influence of Number of Load Applications On Resilient Modulus
			Coupled Effects of Number of Load Applications and Suction On Resilient Modulus
			Influence of Cyclic Stress On Resilient Modulus
			Influence of Suction On Resilient Modulus
			Influence of Wetting and Drying History On Resilient Modulus
		Verification of the Proposed Equation
		Summary
	Shear Modulus and Damping Ratio at High Suction of 40 MPa of Specimens With Different Initial Microstructures (Ng Et Al., 2017b)
		Introduction
		Interpretations of Experimental Results
			Shear Modulus Degradation Curves of Unsaturated Loess at Initial Suctions
			Shear Modulus Degradation Curves After Suction-Induced Desiccation
			Effect of Desiccation-Induced Suction of 40 MPa On Normalised Shear Modulus
			Effects of Microstructure On Cyclic Threshold Shear Strain at Different States
			Effects of Soil Microstructure On Shear Stiffness
			Damping Ratio
			Comparison of Test Results With Design Charts
		Summary
Chapter 6 Thermal Effects On Soil Behaviour and Properties
	Cyclic Shear Behaviour of Silt at Various Suctions and Temperatures (Ng and Zhou, 2014)
		Introduction
		Test Apparatus
		Test Program and Procedures
		Interpretation of Experimental Results
			Suction Effects On Axial Plastic Strain Accumulation
			Thermal Effects On Axial Plastic Strain Accumulation
			Influence of Temperature On Resilient Modulus
			Influence of Suction On Resilient Modulus at Various Temperatures
		Summary
	Effects of Soil Microstructure On the Shear Behaviour of Loess at Different Suctions and Temperatures (Ng Et Al., 2016c)
		Introduction
		Test Apparatus and Program
		Test Procedure
		Interpretations of Experimental Results
			Microstructures of Intact and Recompacted Specimens
			Comparison of the Shear Behaviour of Intact and Recompacted Unsaturated Specimens
			Thermal Effects On the Shear Behaviour of Unsaturated Intact and Recompacted Specimens
			Effects of Suction and Temperature On Soil Dilatancy
		Summary
	Effects of Temperature and Suction On Secant Shear Modulus (Zhou Et Al., 2015)
		Introduction
		Interpretations of Experimental Results
			Suction Effects On Secant Shear Modulus
			Thermal Effects On Secant Shear Modulus
			Effects of Suction and Temperature On Shear-Induced Volume Change
		Summary
	Thermal Effects On Yielding and Wetting-Induced Collapse of Recompacted and Intact Loess (Ng Et Al., 2018; Cheng Et Al., 2020)
		Introduction
		Test Programme
		Test Apparatus
		Test Procedures
		Interpretations of Experimental Results
			Thermal Effects On Yielding Behaviour of Recompacted Loess
			Comparison Between the Yielding Characteristics of Recompacted and Intact Loess
			Thermal Effects On Wetting-Induced Collapse of Recompacted Loess
			Comparisons Between Wetting-Induced Collapse of Recompacted and Intact Loess
			Influence of Soil Micro-Structure On Thermal Softening
		Summary
	Volume Changes of an Unsaturated Clay During Heating and Cooling (Ng Et Al., 2016d)
		Introduction
		Test Programme and Test Apparatus
		Test Procedures
		Interpretation of Experimental Results
			Typical Thermally Induced Volumetric Behaviour
			Suction Effects On Volume Changes During Heating and Cooling
			Effects of Soil Micro-Structure On Volume Changes During Heating and Cooling
		Summary
Chapter 7 Constitutive Modelling of State-Dependent Behaviour of Soils
	Elastoplastic Modelling of State-Dependent Saturated and Unsaturated Soil Behaviour (Ng Et Al., 2020a)
		Introduction
		A Unified and Simple Framework for Simulating the State-Dependent Behaviour of Soils
			Determination of the Variable I11
			Determination of the Variable I12
			Determination of the Variable I13
			Determination of the Variable I21
			Determination of the Variable I22
			Determination of the Variable I23
			Determination of the Variable I31
			Determination of the Variable I32
			Determination of the Variable I33
		Discussion On the Simple and Unified Framework
		Summary
	Simulating the Cyclic Behaviour of Soils at Different Temperatures Using Bounding Surface Plasticity Approach (Zhou Et Al., 2015a; Zhou and Ng, 2016)
		Introduction
		Mathematical Formulations
			Constitutive Variables
			State Parameters
			Normal Compression Line (NCL)
			The Critical State Line (CSL)
			Water Retention Curve (WRC)
			Elastoplasticity
			Elastic Moduli
			Bounding Surfaces
			Yield Surfaces
			Mapping Rule
			Flow Rule
			Hardening Law
		Experimental Program to Verify the SOA Model
		Determination of Soil Parameters
			Parameters for Water Retention
			Elastic Parameters
			Parameters for Normal Compression and the Critical State
			Parameters for Dilatancy
			Parameters for Hardening
		Comparisons Between Measured and Computed Results
		Summary
Chapter 8 Field Monitoring and Engineering Applications
	The South-To-North Water Diversion Project, China (Ng Et Al., 2003)
		The Test Site
		Soil Profile and Properties
		Field Instrumentation Programme
			Monitoring Soil Suction and Water Content
			Monitoring Horizontal Total Stresses
			Monitoring Horizontal Movements and Surface Heave
			Monitoring Rainfall Intensity, Runoff and Evaporation
		Artificial Rainfall Simulations
		Observed Field Performance
			Effects of Simulated Rainfall On Pore-Water Pressures (PWP) and Soil Suction
			Responses of Soil Suction Or Pore-Water Pressure (PWP)
			Responses of Piezometric Level
			Variations of In-Situ PWP Profiles
			Response of Volumetric Water Content (VWC)
			Variations of In-Situ Water Content Profiles
			Response of Horizontal Total Stresses to Changes of Pore-Water Pressure Or Suction
			Response of Ground Deformations in Response to the Simulated Rainfalls
			Soil Swelling at Shallow Depths Upon Wetting
		Summary
	Field Monitoring of an Unsaturated Saprolitic Hillslope On Lantau Island in Hong Kong (Leung Et Al., 2011)
		Introduction
		Description of the Study Area
		Features of Active Landslide Mass
		Geological–hydrogeological Model
		Soil Properties
		Instrumentation Programme and Monitoring Results
		Rainfall Characteristics
		Response of PWP and VWC
		Piezometric-level Variation
		Subsurface Total Horizontal Stress
		Subsurface Horizontal Deformation Characteristic
		Investigation of Hillslope Behaviour
		Infiltration Characteristic and Groundwater Condition
		Deformation Characteristics and Failure Modes
		Summary
	Field Performance of Non-Vegetated and Vegetated Three-Layer Landfill Cover Systems Using Construction Waste Without Geomembrane (Ng Et Al., 2016b, 2019d, 2022b)
		Introduction
		Theoretical Considerations of Newly Proposed Landfill Cover
		Fundamental Principle of Reducing Water Infiltration and Percolation
		Long-term Field Test of the New Vegetated Cover System Using Recycled Concretes Without Geomembrane
			Introduction
			Site Description
			Material Properties
			Field Instrumentation and Monitoring
		Numerical Analysis
			Hydrological Model for Vegetated Three-Layer Landfill Cover System
			Model Implementation and Boundary Conditions
		Field Monitoring Results
			Seasonal Variations of Climate Conditions
			Seasonal Responses of Pore-Water Pressure
			Responses of Pore-Water Pressure Along Depth Under Heavy Rainfall
			Seasonal Responses of Volumetric Water Content
			Responses of Volumetric Water Content Along Depth Under Heavy Rainfall
			Effects of Grass On Measured Percolation
			Effects of Grass On Soil-Water Balance
		Summary
	Use of Unsaturated Small-Strain Soil Stiffness in the Design of Wall Deflection and Ground Movement Adjacent to Deep Excavations (Ng Et Al., 2020d)
		Introduction
		The Excavation Site
		Theoretical Basis
		Design Analysis
			Finite Element Mesh and Boundary Conditions
			Input Parameters for Soil and Pile Wall
			Construction Stages and Simulation Procedures
		Comparison of Analyses With and Without Considering Suction Effects On Soil Stiffness
			Deflection of Pile Wall
			Ground Surface Settlement
			Basement Heave
		Summary
References
Author Index
Subject Index