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Geosynthetic Reinforcement Technologies and Recent Developments

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Title: Geosynthetic Reinforcement Technologies and Recent Developments


1
Geosynthetic Reinforcement Technologies and
Recent Developments
Jie Han, Ph.D., PE Associate Professor
The University of Kansas, USA
2
Outline of Presentation
  • Introduction
  • Reinforcement Mechanisms
  • Reinforcement for Earth Retaining
  • Reinforcement for Foundation Support
  • Concluding Remarks

3
Introduction
4
Ancient Reinforcement Technology
Han Great Wall
Courtesy of Xue
5
Modern Reinforcement Technology
In the 1960s, noted engineer and architect, Henri
Vidal introduced reinforced earth technology
Source Reinforced Earth Company
6
Geosynthetic Reinforcement
Woven Geotextile
GSI
New Geogrid
Geocell
7
Evolution of Geosynthetic Reinforcement
  • 1926 Woven cotton textiles were used in test
    sections in highways in South Carolina, USA
  • 1977 International Conference on the use of
    fabrics in geotechnics - Paris, France. The words
    "geotextiles" and "geomembranes" were coined by
    Dr. J.P. Giroud.
  • 1980 The first book on Geosynthetics by Koerner
    Welsh
  • 1983 The International Geotextile Society (IGS)
    was founded in Paris, France
  • 1986 Giroud, J.P., From geotextiles to
    geosynthetics a revolution in geotechnical
    engineering, Proceeding III International
    Conference on Geotextiles, Vienna, Austria
  • Two Terzaghi Lectures Koerner (2000) and Giroud
    (2008)

8
Reinforcement Mechanisms
9
Reinforcement Mechanisms
  • Provide (tensile) strength necessary for soil
  • Increase shear (interlocking or confinement)
    resistance
  • Mechanisms anchorage (tensile resistance),
    lateral
  • and vertical confinement

Vertical Confinement (Tensioned Membrane)
Lateral Confinement
Anchorage
10
Confinement and Interlocking
Interlocking
11
Particle Movement Under Wheel Loading
Geogrid Reinforcement
No Reinforcement
Courtesy of Kinney
12

Effect of Confinement - Strength
Tensile force
13

Effect of Confinement - Modulus
Applied Pressure
E1
1
Vertical Displacement
3D reinforcement
Unreinforced
2D reinforcement
14
Original Research by US Army Corps of Engineers
- 1979
Beach Landing Tests - Virginia, USA - 1984
Wheels Sink into Sand
Support of Wheels on Geoweb Confined Sand
15
Vertical Stress Distribution in Two-Layer System
a
h1r
E1
E2
z/a
Burmister (1958)
16
Benefits of Geosynthetic Reinforcement
  • Increase bearing capacity
  • Increase factor of safety of slope stability
  • Increase stiffness of soil
  • Reduce differential settlement
  • Reduce permanent deformation under dynamic
  • loading
  • Minimize/slow down deterioration of base course

17
General Applications
Slopes
Earth retaining
Walls
Reinforcement
Embankments Foundations Roads Railroads Landfills
Foundation support
18
Reinforcement for Earth Retaining
19

Case History - Recreational Water Park
  • Design Requirements
  • Create artificial mountain 21m (70 ft) high
  • Highly irregular surface shape
  • Slopes from 3H1V to 0.35H1V
  • Compressible foundation soils

Orlando, FL
20
Facing Details
Orlando, FL
21
Placement of Geogrid in Slope
22
Complete Product
  • Lessons Learned
  • Fast track construction
  • Flexible facing
  • Onsite or low quality fill
  • Natural vegetation
  • Economic

Orlando, FL
23
Failure Modes of Reinforced Slopes
24
Search for Minimum Factor of Safety
Method 1
FS
Exit points
FS
Start points
Method 2
Critical surface
25
FS Safety Map
Courtesy of Leshchinsky
26
Surficial Failure
  • Shallow failure surface up to 1.2m (4ft)
  • Failure mechanisms
  • Poor compaction
  • Low overburden stress
  • Loss of cohesion
  • Saturation
  • Seepage force

27
Surficial Slope Stability
z
Saturated
Primary reinforcement
H
ß
Secondary reinforcement
Tg summation of geosynthetic resisting force
(controlled by pullout or rupture)
28
Full-Height Panel Wall System
29
(No Transcript)
30
(No Transcript)
31
(No Transcript)
32
(No Transcript)
33
(No Transcript)
34
(No Transcript)
35
Modular Block Wall System
36
Failure Modes of Retaining Walls
37
External and Internal Stability
External stability
S1/2hs
q gS
hs
z
qr gz
H
Internal stability
pa1KagH
pa2KagS
38
Water-induced Wail Failure
Courtesy of Leshchinsky
39
Geogrid-Reinforced Wall along JR Kobe Line (1992)
Courtesy of Leshchinsky
40
Geogrid-Reinforced Wall along JR Kobe Line (1995)
Courtesy of Leshchinsky
41
Case Study Limited Space MSE Walls
(Courtesy of Daryl Wurster)
42
(Courtesy of Daryl Wurster)
43
(Courtesy of Daryl Wurster)
44
(Courtesy of Daryl Wurster)
45
Modified Coefficient of Lateral Earth Pressure,
Ka
? 36o, m ?
46
Case Study Tiered Wall
47
Exterior/Interior Wall Cracks
48
Limit Equilibrium and Numerical Analyses
49
Tiered Wall Lessons Learned
  • Limit equilibrium and numerical analyses
  • yield nearly identical Factor of Safety (FoS)
  • FoS 1.20 (with c), FoS 1.05 (without c).
  • Cohesion should not be considered for a
  • long-term stability
  • FoS gt 1.3 is enough for slope stability but
  • FoS gt 1.5 is required to support sensitive
  • structures


50
Case Study Piles in MSE Wall
51
(No Transcript)
52
Wall and Pile Construction
53
Geogrid and Fill
54
Single Pile Test
55
Group Pile Test
56
Facing Deflection Horizontal Profile
Single Pile Test
Group Pile Test
57
Wall after Testing
Group after test at noon
Group after test
Group after test afternoon
58
Reinforcement for Foundation Support
59
Failure Modes of Basal Reinforcement
60
Geosynthetic-Reinforced Pile/Column-Supported
Embankments
Geosynthetic-reinforced fill platform
Ds?0
Geosynthetics
Embankment
Ds0
Small size Pile caps
Piles or columns
Firm soil or bedrock
61
Type of Columns
62
Piles and Caps
Geosynthetics
Courtesy of Chris Dumas
63
Applications of Pile-supported Embankments
64
Displacement Vector DEM Study
Soil Arching
Tensioned membrane
Unreinforced embankment
Reinforced embankment
Bhandari and Han (2008)
65
Current Design Method
Step 1
Soil arching
Pressure on geosynthetic
Step 2
Membrane or Beam theory
Tension in geosynthetic
Step 3
Slope stability
66
Field Performance
Courtesy of Huesker
67
Physical Model Simulation
68
Design Issues
  • Percent coverage of pile or cap 10 to 20
  • Pile type rigid pile is better
  • End-bearing condition preferred
  • Critical height (1.0 to 1.5) clear space of
    piles
  • Soil resistance a significant effect
  • Strain in geosynthetics 2 to 6 (design) and 0
    to 3
  • (measured)
  • Settlement more effective for differential
    settlement
  • and no reliable and simple method available

69
Subgrade Improvement for Unpaved Roads
70
Base Reinforcement for Paved Roads
  • Prevent lateral spreading of base aggregate
  • Increase confinement
  • Reduce plastic deformation - rutting

Courtesy of Reck
71
Failure of Base Courses
Unreinforced
Horizontal confinement
Vertical confinement
Geocell-Reinforced
72
Bearing Capacities for Unreinforced and
Reinforced Cases
p0?c
pu(?2)c
p
p
p
Base
Base
Elastic limit
Subgrade
Subgrade
Ultimate bearing capacity
s
73
Failure of Subgrade
Tire
Initial distribution
Distribution at failure
Distribution after N passes
Giroud and Han (2004)
74
Cyclic Plate Loading Test
75
(No Transcript)
76
Testing of Geocell-reinforced Bases
77
Moving Wheel Testing
78
Cumulative Plastic Deformation
79
Base Thickness - Reinforced
Giroud and Han (2004)
80
Landfill Slope Stability
Geogrid
Geomembrane
Courtesy of Giroud
81
Courtesy of Giroud
82
Landfill Liner Support
Geogrid
Void
Geosyntec
83
Concluding Remarks
  • Geosynthetic reinforcement has been successfully
  • used for many different applications
  • Geosynthetic reinforcement can provide tensile,
    shear,
  • and confinement resistance
  • Reinforced slope is flexible at different slope
    angles
  • but surficial slope stability is a major
    concern
  • FoS gt 1.3 is enough for slope stability but FoS
    gt 1.5 is
  • required to support sensitive structures
  • Geosynthetic-reinforced wall has a superior
    seismic
  • resistance
  • Reinforced wall can effectively carry lateral
    load from pile
  • Geosynthetic can reduce plastic deformation
    under
  • traffic loading


84
Thank You!
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