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Title: Vibrocompaction, Vibroreplacement, and Vibrodisplacement


1
Vibrocompaction, Vibroreplacement, and
Vibrodisplacement
  • Prof. Jie Han, Ph.D., PE
  • The University of Kansas

2
Outline of Presentation
  • Introduction
  • Installation Methods
  • Theories and Design
  • Quality Control

3
Introduction
4
Vibro Methods
  • Vibrocompaction
  • Densify insitu soil without removal and backfill
  • Vibroreplacement
  • Remove insitu soil backfilled with high-quality
    fill
  • Vibrodisplacement
  • - Displace soil backfilled with high-quality fill

5
Vibrocompaction
  • Blasting
  • Explode inside the ground
  • Vibro-probe or Vibroflotation
  • - Insert vibrating probes into the ground
  • Vibro-drain
  • Insert vibrating probes into the ground with
  • a back-drain system

6
Vibroreplacement
  • Vibroflotation
  • Insert vibrating probes into the ground, wash
  • out insitu soil, and backfill high-quality fill
  • Geopiers
  • Augered into the ground backfilled with
  • high-quality fill

7
Vibrodisplacement
  • Compaction sand pile
  • Insert a casing into the ground and backfill
  • sand inside the casing
  • Bottom-fed stone column
  • Insert vibrating probes into the ground and
  • bottom-feed aggregates
  • Vibro-concrete column
  • Insert vibrating probes into the ground and
  • bottom-feed low-strength concrete

8
Influence Factors of Effectiveness
  • Soil type, especially its gradation and fine
  • content
  • Degree of saturation and water table location
  • Initial relative density
  • Initial in-situ stresses
  • Initial soil structures, including the effects
    of
  • age, cementation, etc
  • Special characteristics of the method used

9
Mechanism of Densification
For saturated cohesionless soils
  • Breakdown of initial soil structure to a more
  • stable packing arrangement
  • Liquefaction under dynamic and cyclic
  • loadings

For partially saturated cohesionless soils
  • Collapse of soil structure and escape of gas
  • from voids

10
Installation Methods
11
Vibrocompaction
Woodward (2005)
12
Sand Compaction Pile
Tanimoto (1973)
Courtesy of Fudo Construction, Inc.
13
Casing Tip Movement
Tanimoto (1973)
14
Special Valve for Pressured Air
Barksdale (1987)
15
Casing Shoe
Barksdale (1987)
16
Vibro Wing Machine
Massarsch and Fellenius (2005)
17
Other Compaction Probes
Y probe
Terra probe
Vibro rod
18
Vibrocompaction
Woodward (2005)
19
Suitability Number
  • A rating system developed to judge the
    suitability of backfill
  • material for vibro-compaction based on the
    settling rate of
  • the backfill in water and project experience

Suitability Number
gt 50
0 - 10
10 - 20
20 - 30
30 - 40
Fair
Poor
Unsuitable
Rating
Excellent
Good
Brown (1977)
20
Vibratory or Impact Compactability
Massarsch (1991)
21
Performance Criteria
  • For most vibrocompaction projects, the following
    performance
  • criteria should be considered
  • 60 relative density for floor slabs, flat
    bottom tanks,
  • embankments
  • 70 75 relative density for column footings,
    bridge footings
  • 80 relative density for machinery and mat
    foundations

FHWA NHI-04-001 (2004)
22
Effectiveness of Vibrocompaction
Hayward Baker
23
Relative Density vs. Tributary Area
Relative Density (Percent)
Site Surface Area Per Compaction Probe (ft2)
Hayward Baker
24
Vibro-Drain
Hodge (1998)
25
Vibro-Drain
Hodge (1998)
26
Vibro-Drain Induced Settlement
Hodge (1998)
27
Vibroflotation/Stone Columns
28
Vibroreplacement Top Feed
Hayward Baker
29
(No Transcript)
30
(No Transcript)
31
Exposed Columns
32
Vibroreplacement
Woodward (2005)
33
Effectiveness of Vibroreplacement
Hayward Baker
34
Stone Columns
Woodward (2005)
35
Geopier Construction
36
Geopier Construction
37
Geopier Construction
Well-graded stone tampered in thin lifts
Beleved tamper increases lateral pressures
38
Geopiers
39
Geopiers under Footing
40
Vibro Concrete Column
Hayward Baker
41
Vibro Concrete Column
42
Vibro Concrete Column
43
Vibro Concrete Column
44
Theories and Design
45
Failure Modes
(2-3)d
Shear failure
d
Bulging failure
Punching failure
46
Suitability of Stone Columnsin Soft Clay
Undrained shear strength gt 15 kPa
47
Theoretical Solution for Bearing Capacity
?c
?s
h
?p 45o ?p/2
?p
?
r0
Ultimate bearing capacity
Brauns (1978)
48
Bearing Capacity of Single Column
?s 0
If ?p 38o, ?p 64o and ? 61o
Brauns (1978)
49
General Bearing Capacity Formula for Single
Column
cu (kPa)
Soil type
K
Kp K
References
4.0 3.0 6.4 5.0 5.0 - -
25.2 15.8-18.8 20.8 20.0 25.0 14.0-24.0 12.2-15.2
Hughes Withers(1974) Mokashi et al
(1976) Brauns (1978) Mori (1979) Broms (1979) Han
(1992) Guo Qian (1990)
Clay Clay Clay Clay Clay Clay Clay
19.4 19.0 - 20.0 - 15.0-40.0 -
Recommended
Ye et al. (1994)
50
Area Replacement Ratio
d
Contributory area, A
Ac
As
s
A Ac As
Area replacement ratio, as
as Ac / A
Equilateral triangular pattern
Square pattern
51
Typical Diameter and Area Replacement Ratio
Typical diameter of stone columns 2 to 3
feet VCC columns diameter 20 inches, base and
top 30 inches
Typical area replacement ratio 10 to 30
52
Volume of Backfill
Assume full displacement
A
A
Vf
Backfill
Void
Vv
Void
Vv
V0
V1
Vs
Solids
Solids
Vs
53
Required Column Spacing
Volume of backfill
Spacing for square pattern
Spacing for triangular pattern
54
Equal Stress vs. Equal Strain
?c
?s
?c
?s
?s
Ec
Ec
Es
(a) Equal strain
?c
?s
?c
?s
?s
Ec
Ec
Es
(b) Equal stress
55
Stress Concentration
?c
?s
?
Ec
Ec
Es
Es gt Ec
Stress concentration ratio
Stress reduction factor
56
Stress Concentration Ratio
Stress
?c2
?c3
?c4
?c1
?s4
?s3
?s2
?s1
Strain
57
Stress Concentration Ratio
Stress concentration ratio, n
1.0
0
Strain
58
Stress Concentration Ratio
59
Equivalent Modulus
?c
?s
?
?
Ec
Es
Equivalent modulus
60
Settlement Reduction Factor
Settlement of untreated ground
Settlement of treated ground
If assume mv mv
Settlement reduction factor
61
Improvement Factor
1/
Hayward Baker
62
Model for Ideal Vertical Drains
de1.06s (triangular pattern of drains,
sspacing) de1.13s (square pattern of drains)
63
Partial Differential Equation for Axisymmetric
Flow
General
Vertical flow
Terzaghis 1D consolidation theory
Horizontal flow
Barrons consolidation theory
64
Overall Rate of Consolidation (Carillo, 1942)
Ur rate of consolidation due to radial flow
Uv rate of consolidation due to vertical flow
65
Barrons Solution
Average rate of consolidation due to radial flow
Diameter ratio
Time factor in radial flow
cr - coefficient of consolidation due to radial
flow dc and de diameters of a drain well and
its influence zone, respectively t time period
for consolidation
66
Model for Free-Draining Stone Columns
de
p
Drainage surface
rc
z
H
Stone column
2H
kv
kh
r
Drainage surface
re
67
Han and Yes Solution
Average rate of consolidation due to radial flow
Diameter ratio
Time factor in radial flow
68
Degree of Consolidation
69
Comparison
70
Degree of Consolidation due to Vertical Drain
71
Degree of Consolidation due to Radial Drain
72
Dissipation of Excess Pore Pressure
73
Stress Variations with Time
74
Smear and Well Resistance Effects
de
p
Drainage surface
rs
rc
z
H
Drain well
2H
ks
kc
r
Drainage surface
re
75
Hansbos Solution
Average rate of consolidation due to radial flow
Diameter ratio of smeared zone to drain well
ds Diameter of smeared zone
kr - radial permeability of undisturbed
surrounding soil
ks - radial permeability of smeared soil H
longest drainage distance due to vertical flow z
depth in the ground at which the rate of
consolidation is computed
Discharge capacity of drain well
kc - permeability of drain well
76
Han and Yes Solution
Average rate of consolidation due to radial flow
Time factor in radial flow
77
Effect of Well Resistance
Han and Ye (2002)
78
Effect of Smear
Han and Ye (2002)
79
Stability Analysis
Aboshi et al. (1979)
80
Stability Analysis
typically, 0.4 to 0.6
Priebe (1978)
81
Stability Analysis
82
Soil Densification Effect
SPT N value
Clay
Depth
Sand
Treated
Test point
Untreated
Silt
83
SPT N Value mid-way between Sand Piles
84
SPT N Value at the Center of Sand Piles
85
Effect of Fine Content on SPT N Value
Saito (1977)
86
Effect of Grain Size on SPT N Value
87
Uniform Cyclic Shear Stress
?v the total stress, rd stress reduction
factor
88
Stress Reduction Factor
Seed Idriss (1971)
89

Cyclic Stress Ratio (CSR)
Cyclic stress ratio (CSR) is defined as
90
Factor of Safety against Liquefaction
 
91
Required Factor of Safety against Liquefaction
 
Martin and Lew (1999)
92
Magnitude Correction Factors
Magnitude, M
CSRM/CSRM7.5
5 ¼ 6 6 ¾ 7 ½ 8 ½
1.50 1.32 1.13 1.00 0.89
93
Effect of Fine Contents
Seed et al. (1975)
94
Zone of Liquefaction
95
Process of Earthquake-Induced Settlement
96
Settlement of Saturated Sands after Earthquake
Settlement
evi volumetric strain
Hi liquefiable soil thickness
97
Relation between Relative Settlement and Ground
Improvement Method
- Relative Settlement (cm) -
ltUnimproved Areagt
Relative settlement?0
- Ground Improvement Method -
ltImproved Areagt
Courtesy of Fudo Construction, Inc.
98
The 1995 Hyogo-Ken Nambu Earthquake
Outline of the Earthquake ?Occurrence time
01/17/95 ? Magnitude M7.2 ? Source Depth 20km
cracks and sand boils were observed
ltUnimproved Areagt
Courtesy of Fudo Construction, Inc.
99
Effectiveness at Leisure Facilities by Sand
Compaction Piles - the 1995 Hyogo-Ken Nambu
Earthquake
No Damage was observed
ltImproved Areagt
Courtesy of Fudo Construction, Inc.
100
Extent of Improvement
Improved area
Liquefaction
l
L
L 2/3 l and 5m lt L lt 10m
JGS (1998)
101
Quality Control
102
Quality Control Method
  • SPT/DCP tests into the columns and surrounding
    soil
  • CPT tests into the surrounding soil
  • Plate load tests
  • Geophysical methods

103
Dynamic Cone Penetration Test
Geopier
104
Plate Load Test
Geopier
105
Plate Load Tests
  • Untreated ground
  • Single column
  • Composite ground
  • Group columns

106
Plate Load Tests
Single column
Composite ground
Group columns
107
Single Column Load Test
White et al. (2007)
108
Group Column Load Tests
White et al. (2007)
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