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Table of Contents
                            INTRODUCTION
	Overview
	Historical Background
	Research Objective and Scope
	Research Methodology
	Outline of Report
	Key Findings
LITERATURE REVIEW
	Introduction
	Factors Affecting Swell and Moisture Migration
	Moisture Variation within Soil Profile
		Infiltration and Wetting Front
		Soil Profile
		Definition of Active Zone Depth and Related Terms
			Active Zone Depth
			Zone of Seasonal Moisture Fluctuation
			Depth of Wetting
			Depth of Potential Heave
		Edge Moisture Variation Distance
	Causes of Water Content Change; Field Observations of Moisture Migration and Heave
		Monotonic Water Content Change
		Seasonal Water Content Change
CURRENT PRACTICE
	Factors Affecting Residential Building Performance
	Drainage Design Standards and Standard of Practice
	Residential Foundation Design in USA
	Residential Foundation Design in Other Countries
	Design and Construction Practice – Interviews with Industry
		Geotechnical Engineering Interviews
			Site Investigation and Soil Testing
			Site Monitoring
			Communication
			Geotechnical Report
			Design Procedure
			Mitigation Measures
			Areas of Problems
			SWCC and Suction
		Structural Engineering Interviews
			Occurrence of Expansive Soils
			Communication
			Geotechnical Report
			Structural Analysis and Design Procedure
			Mitigation Measures
			Areas of Problems and Concerns
		Home Builder Interviews
			Site Assessment
			Budget and Design
			Site Preparation Process
			Site Monitoring
			Communication
			Mitigation Measures
			Sources of Problems
			Litigation
		Forensic Investigation
			Failure Modes
				Center Lift
				Edge Lift
				Settlement
			Remediation Methods
	Failure Criteria
	Summary
LABORATORY DATA
	Field Exploration
		Equipment
		Field Sampling
	Soil Testing for Input Parameters
		Moisture Content and Dry Density
		Atterberg Limits
		Sulfate Content
		Cation Exchange Capacity
		Specific Gravity
		Expansion Index
			Arizona Modified Expansion Index Procedure
			Expansion Index Procedure as per ASTM D 4829
		Constant Volume Oedometer Testing
		Consolidation Test and Correction Factors
		Saturated Hydraulic Conductivity
		Soil Suction
			Pressure Plate
				Equipment
				Issues Associated with SWCC Testing
				One Point Method of SWCC Determination
				Complete SWCC
			Filter Paper
			Dessicator
		Summary of Laboratory Results
			Sampling Locations
			Summary Tables
		Selection of Input for Modeling
MAP OF EXPANSIVE SOIL DISTRIBUTION IN PHOENIX VALLEY
PTI RESIDENTIAL FOUNDATION DESIGN
	Introduction
	Historical Background
	Definitions
	PTI 2nd Edition Design Procedure, 1996
THORNTHWAITE  MOISTURE INDEX
	PTI 3rd Edition Design Procedure, 2004
		Additional Definitions Provided in the Procedure.
		Assumptions.
		Procedure.
	Design Parameters for Arizona
	Discussion
	Sensitivity Analysis
		Influence of Suction Profiles on Geotechnical Parameters
		Influence of Geotechnical Parameters on Slab Thickness
		Sensitivity of ym to Suction Profile
		Comparison of Different Suction Compression Index Methodologies
		Influence of Gravel Correction
	Conclusions
MODELING – NUMERICAL METHODS
	Modeling Challenges
	Selection of Program
		Convergence, Stability and Accuracy
		Experiment Set-Up
		Presentation of Results
		Discussion and Conclusions
	Sensitivity analysis of SWCC and k(h)
		Uncertainty of Unsaturated Soil Functions
		Problem Set-Up
			Soil Properties
			Initial and Boundary Conditions
			Modeling Software, Mesh Size and Time Step
		Numerical Simulation
			Hysteresis in SWCC
			Uncertainty in k(h)
				Infiltration
				Evaporation
		Conclusions
	SVFlux Program Behavior
		Numerical Oscillations – Lessons Learned
		Numerical Challenges
	Numerical Experiments
		Fixed vs. Adaptive Time Step
		Mixed Formulation
		Normalization
		Spatial Discretization - Pseudospectral Method
		Time Discretization - Exponential Integrator
		Time Discretization - ADI
	Conclusions
MODELING – NUMERICAL RESULTS
	Modeling Objective
	Design of Experiment
		Problem Assumptions and Restrictions
		Program
		SVFlux Specific Restrictions
		Boundary and Initial Conditions
		Domain Size
		Soil Input Parameters
		Determination of Appropriate Input Flux
			Evaporation
			Desert and Low Water Use Landscaping
				Irrigation Needs of Desert and Low Water Use Landscape
				Irrigation Systems
				Input Flux for Desert and Low Water Use Landscape
				Average Input Flux
			Turf Landscaping
				Irrigation Needs of Grass
				Irrigation Systems
				Typical Water Use on Turf Landscaping
				Flux Input for Turf Landscaping
				Average Input Flux
		Output Presentation - Definitions
	Convergence Studies
	Simplification of Flux
		Potential Evaporation
		Precipitation and Irrigation
			1-D Desert Landscape
FIELD EVIDENCE OF WETTING/DRYING INDUCED DAMAGE
	Depth of Wetting and Depth of Active Zone
	Forensic Investigations
		Type of Data Collected
		Sources of Suction Change Related Distress
		Degree of Saturation and Suction Conditions below Foundations
		Comparison of Landscape Type to Distress Magnitude
		Relative Slab Differential Data
	Comparison of forensic Investigation Incidence to Soil Properties
	Key Findings
CONCLUSIONS AND RECOMMENDATIONS
	Scope of Research Work
	Conclusions
	Future Research
REFERENCES
	SM-ML Soil: Desert Landscape
	1-D SM-ML Soil: Desert Landscape, year 1, hourly flux
	1-D SM-ML Soil: Desert Landscape, year 1-6, hourly flux
	1-D SM-ML Soil: Desert Landscape, year 1, average flux
	1-D SM-ML Soil: Roof Runoff Ponding, year 1, hourly flux
	SM-ML Soil: Turf Landscape
	1-D SM-ML Soil: Turf Landscape, year 1, average flux, Flux = 2.2PE
	1-D SM-ML Soil: Turf Landscape, year 1, hourly flux, Flux = PE, IC=5th year desert
	CH Soil: Desert Landscape
	1-D CH Soil: Desert Landscape, year 1, hourly flux
	1-D CH Soil: Desert Landscape, years 1-6, hourly flux
	1-D CH Soil: Desert Landscape, year 1, average flux
	1-D CH Soil: Roof Runoff Ponding, year 1, hourly flux
	CH Soil: Turf Landscape
	1-D CH Soil: Turf Landscape, 1st year, hourly flux, Flux = 2.2PE
	1-D CH Soil: Turf Landscape, years 1-34, hourly flux, Flux = 2.2PE
	1-D CH Soil: Turf Landscape, 1st year, average flux, Flux = 2.2PE
	1-D CH Soil: Turf Landscape, 1st year, hourly flux, Flux = 1.3PE, IC=-153 m.
	1-D CH Soil: Turf Landscape, 1st year, hourly flux, Flux = 1.3PE, IC=34the year of turf
                        
Document Text Contents
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oscillations with depth and at the soil surface with time. The determined maximum dx for the

most challenging flux period was then used in the entire analysis, while maximum dt was allowed

to change from one flux period to another based on the results of convergence studies.

Convergence studies were not performed on average flux scenarios. It was assumed that the

stringent convergence criteria developed for the hourly flux analyses are sufficient for the

average flux scenarios; the anticipated program runtime with average flux is smaller than the

time required for convergence study.

An illustrative example of convergence analysis is presented in Figure 8.14, through

Figure 8.16. They show results obtained with 1-D analyses of the SM-ML soil for January desert

landscape flux. The solution of SM-ML soil required the implementation of constant dt with

increased number of Newton iterations (adaptive dt generation lead to unstable behavior during

precipitation events). The mesh discretization for the 10-m deep profile was implemented with

an exponential function, )( byae −− with origin of the domain at the base boundary. The results are

presented in terms of the node spacing at the soil surface.

For problems involving only evaporation, Figure 8.14a, convergence criteria require dx

smaller than 0.00048-m. Implementation of larger mesh size results in overestimation of both,

domain accumulation and cumulative AE. When the applied flux consists of PE only, for 1-D

problems the domain accumulation and cumulative AE should be identical. Figure 8.14 further

illustrates that these values differ when the solution is obtained with large mesh spacings, and

converges to a single value as the mesh size decreases. Figure 8.14b shows that modeling of

evaporation (PE) alone is insensitive to dt. Time step of 0.5 h was found to be adequate.

Figure 8.15 illustrates the convergence study performed on precipitation period in

January for 1-D analyses of the SM-ML soil. The flux consists of precipitation and PE. The

figure shows that when AE is almost equal to PE (this is always true when flux into the soil

exceeds PE), AE result is insensitive to considered variation in both dx and dt. As the mesh

spacing decreases for constant dt, the domain accumulation values approach a converged value

exponentially. A reduction in dt produces similar results, where these two solutions plot parallel

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to each other; see Figure 8.15a. The same general behavior was observed when keeping dt

constant and varying dx. When a small enough dx is used, the curves obtained overlap and vary

with dt in the same way. Based on the results presented in Figure 8.15b, it was determined that

dt of 0.01-h and dx of 0.00024-m are required to obtain a stable and convergent solution for this

particular soil type and applied flux scheme.

a) b)

-0.040

-0.035

-0.030

-0.025

-0.020

-0.015

0.00001 0.0001 0.001 0.01 0.1

Node Spacing [m]

V
ar

ia
b

le
[

m
]

Net AE

Domain Accumulation

0 0.1 0.2 0.3 0.4 0.5 0.6

Time Step [h]




Figure 8.14. Convergence analysis, January, PE only, desert landscape, SM-ML.


a) b)

0.0138

0.0140

0.0142

0.0144

0.0146

0.0148

0.0150

0.0001 0.001
Node Spacing [m]

V
ar

ia
bl

e
[m

]

ICum. AEI ΔVw, dt = 0.001h ΔVw, dt = 0.01h

ΔVw, dt = 0.025h ΔVw, dt = 0.05h ΔVw, dt = 0.075h

0.0001 0.001 0.01 0.1

Time step [h]
Cum. AEI ΔVw, dx = 9e-4

ΔVw, dx=5e-4m ΔVw, dx = 2e-4

ΔVw, dx = 1e-4


Figure 8.15. Convergence analysis, January, precipitation, desert landscape, SM-ML.

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-3

0

3

6
x 10

-3

Precipitation
and Irrigation [m/h]

Applied Prec. and Irrg. = 1.54 [m/year]



-2

-1

0
x 10

-4

PE [m/h]

PE = 1.18 [m/year]



-2

-1

0
x 10

-4

Instant. AE [m/h]

0 50 100 150 200 250 300 350
-3

0

3

6
x 10

-3

Instant. Flux [m/h]

Time [day]


Figure 86: Instantaneous Flux Data

CH; turf landscape, 1 st year, hourly flux, Flux =1.3PE, IC=turf

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Table 12: Cumulative Flux Data (CH; turf landscape, 1 st year, hourly flux, Flux =1.3PE,
IC=turf)

Input Output
Time

Irrig.+Prec. PE Flux AE
Domain
Accum.

Profile
Water

Volume

[Year] [Month] [Day] [m] [m] [m] [m] [m] [m]
0 0 0 0 0 0 0 3.8821
1 31 0.075 -0.0331 0.042 -0.0330 -0.0536 3.8291
2 59 0.145 -0.0758 0.069 -0.0758 -0.0759 3.8071
3 90 0.232 -0.1471 0.084 -0.1471 -0.1054 3.7771
4 120 0.293 -0.2475 0.045 -0.2334 -0.1487 3.7341
5 151 0.465 -0.3824 0.082 -0.3624 -0.1661 3.7161
6 181 0.63 -0.5342 0.096 -0.4978 -0.1883 3.6941
7 212 0.842 -0.6945 0.148 -0.6484 -0.2005 3.6821
8 243 1.038 -0.8415 0.197 -0.7883 -0.2140 3.6691
9 273 1.223 -0.9656 0.257 -0.9103 -0.2240 3.6591

10 304 1.408 -1.0686 0.339 -1.0127 -0.2283 3.6541
11 334 1.477 -1.1387 0.338 -1.0822 -0.2443 3.6381

1

12 365 1.544 -1.1815 0.362 -1.1248 -0.2364 3.6461

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