7 tc211 hk maertens soil mix
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Belgian Building Research Institute – http://www.bbri.be
1 14 ARC Hong Kong - Workshop TC 211
SOIL MIX
Belgian research activities
SOIL MIX PROJECT – IWT 080736
Nicolas Denies and Noël Huybrechts Belgian Building Research Institute
Geotechnical Division
Belgian Building Research Institute – http://www.bbri.be
2 JFB “Soutènements” – Lille 12 mai 2011
Topics
1. Introduction
2. Purposes of the SOIL MIX Project
3. Test results
3.1 Mechanical characterization
3.2 Durability
3.3 Permeability
3.4 “Steel-soil mix” adherence
4. Perspectives
SOIL MIX Project
Belgian Building Research Institute – http://www.bbri.be
3 14 ARC Hong Kong - Workshop TC 211
1. Introduction
Since 2003 Laboratory testing
Unconfined compressive strength (UCS)
Elastic modulus (E)
Research project “Retaining structure” (2007-2013)
Berlin walls, secant piles walls, diaphragm walls, ...
Deep Soil Mix walls (DSM)
Quality assessment procedure – development of guidelines
New project “SOIL MIX” (2009-2013)
SOIL MIX – IWT 080736
BBRI, ABEF, KULeuven
permanent use and bearing capacity
SOIL MIX Project
Belgian Building Research Institute – http://www.bbri.be
4 14 ARC Hong Kong - Workshop TC 211
2. Purposes of the SOIL MIX Project
SOIL MIX Project
Current application of SOIL MIX Temporary retaining structure
Intended application Foundations – bearing capacity Permanent retaining structures
Gaps: 1. Mechanical characteristics 2. Durability 3. Permeability 4. „Steel – soil mix adherence‟
Belgian Building Research Institute – http://www.bbri.be
5 14 ARC Hong Kong - Workshop TC 211
3. Test results
3.1 Mechanical characterization
Sampling
- Boring
- Transport
- Conservation conditions
Analysis of soil inclusions in the soil mix
Density
- Test procedure and results
Unconfined compressive strength(UCS)
Elastic modulus (E)
Tensile splitting strength (T)
Guidelines have to be provided
SOIL MIX Project
Belgian Building Research Institute – http://www.bbri.be
6 14 ARC Hong Kong - Workshop TC 211
Soil inclusion analysis Soil or soft inclusions into the mix
Sawn column/panel: surface analysis
Surface % Volume % (Weibel, 1980)
Delesse principle (Weibel, 1980)
SOIL MIX Project
3. Test results
3.1 Mechanical characterization
Belgian Building Research Institute – http://www.bbri.be
7 14 ARC Hong Kong - Workshop TC 211
Soil inclusion analysis Soil or soft inclusions into the mix
Sawn column/panel: surface analysis
Surface % Volume % (Weibel, 1980)
Cores: line analysis
Line % Volume % (Weibel, 1980)
Inclusion percentage
- “Soil mix: influence of soil inclusions on structural behaviour” in ECSMGE – Athens 2011 - “Deep Mixing Technology in Belgium: Execution of Retaining Walls and Design Properties of Deep Mixed Material” in Grouting and Deep Mixing conference – New-Orleans 2012
SOIL MIX Project
3. Test results
3.1 Mechanical characterization
Belgian Building Research Institute – http://www.bbri.be
8 14 ARC Hong Kong - Workshop TC 211
Soil inclusion analysis Soil or soft inclusions into the mix
- “Soil mix: influence of soil inclusions on structural behaviour” in ECSMGE – Athens 2011 - “Deep Mixing Technology in Belgium: Execution of Retaining Walls and Design Properties of Deep Mixed Material” in Grouting and Deep Mixing conference – New-Orleans 2012
18 sites in Belgium
Tertiary and quaternary sands: [0 à 3.5%] Silty soils or alluvial clays: [3 à 10%] Clayey soils with organic material (peat) tertiary (overconsolidated) clays
35%
SOIL MIX Project
3. Test results
3.1 Mechanical characterization
Belgian Building Research Institute – http://www.bbri.be
9 14 ARC Hong Kong - Workshop TC 211
Unconfined compressive strength (UCS)
Density – UCS
Influence of the density?
22 sites in Belgium (clay - silt - sand)
SOIL MIX Project
3. Test results
3.1 Mechanical characterization
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
1200 1400 1600 1800 2000 2200
UC
S (
MP
a)
Density (kg/m³)
Columns firm a
Columns firm b
CSM firm c
CSM firm d
Belgian Building Research Institute – http://www.bbri.be
10 14 ARC Hong Kong - Workshop TC 211
Soil inclusion influence – numerical simulations
Unconfined compressive strength (UCS)
Calibration: soil mix block (large scale - 1.2 x 0.55 x 0.55m)
- “Plastic Numerical elasto-plastic simulations of soil mix: Study of the effect of inclusions”, research report, KUL (2011)
In a later phase, discontinuous simulations are planned, so that individual fracture growth can be investigated.
SOIL MIX Project
3. Test results
3.1 Mechanical characterization
Belgian Building Research Institute – http://www.bbri.be
11 14 ARC Hong Kong - Workshop TC 211
Soil mix block (large scale)
- “Uniaxial Compression Test on Large Soil Mix Block (Knokke site)”, rapport de recherche interne, KUL (2011) - “Rock mechanical tests on core samples from soil mix block (site of Knokke)”, research report, KUL (2011)
CSM – Knokke – sand
52.9cm × 60.9cm × 124.0cm
UCS = 8.3 MPa
After 91 days
SOIL MIX Project
3. Test results
3.1 Mechanical characterization
The UCS-value is 8.3 MPa.
At 50% of the peak strength, Et = 13.6 GPa and ES = 16.0 GPa.
Cores with a diameter of 113 mm, drilled inside the block after testing, resulted in an average UCS value of 11.9 MPa.
No significant decrease is observed when the sample is about 5 times larger. For typical rock material, one would expect a reduction by a factor 2 or 3. The reason why this is not observed is probably the fact that the soil mix material is relatively more homogeneous than most rocks.
Not many macro-fractures are observed
Belgian Building Research Institute – http://www.bbri.be
12 14 ARC Hong Kong - Workshop TC 211
- “Uniaxial Compression Test on Large Soil Mix Block (Knokke site)”, rapport de recherche interne, KUL (2011) - “Rock mechanical tests on core samples from soil mix block (site of Knokke)”, rapport de recherche interne, KUL (2011)
CSM – Wetteren – remolded soil (sand/silt)
54.9cm × 48.4cm × 89.9cm
UCS = 2.1 MPa
After 54 days
Soil mix block (large scale)
SOIL MIX Project
3. Test results
3.1 Mechanical characterization
UCS-value is 2.1 MPa.
At 50% of the peak strength: Et = 2.9 GPa and Es = 3.3 GPa.
Cores with a diameter of 113 mm, drilled inside the block after testing, resulted in a average UCS value of 4 MPa a decrease of
about a factor 2.
In comparison to Knokke, the reduction is larger, but the material was also much more heterogeneous than in Knokke.
The reduction is more similar as what one would expect for typical rock material, i.e. a reduction by a factor 2 or 3.
Belgian Building Research Institute – http://www.bbri.be
13 14 ARC Hong Kong - Workshop TC 211
Test on soil mix block (large scale)
Characteristic UCS-value
0
1
2
3
4
5
6
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 >
15
Drukweerstand [MPa]
Fre
qu
en
tie
Histogram of UCS-values [MPa] from cored samples of Knokke panel
Curve ε-σ for the Knokke block (large scale) Characteristic UCS-value = 7.0 MPa*next slide Lognormal distribution*next slide
Good correspondence?
CSTC KUL
- “Deep Mixing Technology in Belgium: Execution of Retaining Walls and Design Properties of Deep Mixed Material” in Grouting and Deep Mixing conference – New-Orleans 2012
After 91 days
After 91 days
UCS = 8.3 MPa
SOIL MIX Project
3. Test results
3.1 Mechanical characterization
Belgian Building Research Institute – http://www.bbri.be
0
2
4
6
8
10
Fre
qu
en
cy (
-)
UCS [MPa]
After 49 days- 25 values
After 91 days- 24 values
0
2
4
6
8
10
Fre
qu
en
cy (
-)
UCS (MPa)
After 49 days- 25 values
After 91 days- 24 values
14 14 ARC Hong Kong - Workshop TC 211
Good correspondence?
KUL
Curve ε-σ for the Wetteren block (large scale)
After 54 days
Representativeness of the cores: Samples with inclusions > 1/6 D are excluded
After 49 days : 1.7 2.5 MPa After 91 days : 2.4 2.7 MPa
BBRI
BBRI
Test on soil mix block (large scale)
Characteristic UCS-value
SOIL MIX Project
3. Test results
3.1 Mechanical characterization
Belgian Building Research Institute – http://www.bbri.be
0
5
10
15
0 200 400 600U
CS
(M
Pa
) Cement content (kg/m³)
7 days
28 days
56 days
0
5
10
15
0 20 40 60 80 100
UC
S (
MP
a)
Curing time (days)
15 14 ARC Hong Kong - Workshop TC 211
UCS – curing time
Sand, CEM III Cement content: 350 kg/m³
Silt, CEM I
mccm UCSttUCS )()(
))28
1(exp()(t
stcc
t = curing time (days) s = empirical parameter [-]
Soil type W/C Cement type
EN 1992-1-1
CSM : 0,96 <s<0,99 CVR : 1.28<s<1.71
“SOIL MIX walls as retaining structures – critical analysis of the material design parameters” in Geotechnical Challenges in Megacities Conference – Moscow 2010
SOIL MIX Project
3. Test results
3.1 Mechanical characterization
Belgian Building Research Institute – http://www.bbri.be
Tensile splitting strength
NBN EN 12390-6 Testing hardened concrete - Part 6: Tensile splitting
strength of test specimens
Sample diameter (D) = 100 mm ± 15% (113 mm)
Sample length (L) = 1 D
16 14 ARC Hong Kong - Workshop TC 211
SOIL MIX Project
3. Test results
3.1 Mechanical characterization
Belgian Building Research Institute – http://www.bbri.be
17 14 ARC Hong Kong - Workshop TC 211
9 sites in Belgium Tensile splitting strength
SOIL MIX Project
3. Test results
3.1 Mechanical characterization
0
1
2
3
0 5 10 15 20
Ten
sile s
tren
gth
(M
Pa)
(sp
litt
ing
)
UCS (MPa)
Columns firm a
CSM firm c
CSM firm d
EN 1992-1-1 : 2004
Engineering practice
EN 1992-1-1 : 2004
Tensile strength (splitting)
= Tensile strength / 0.9
= 0.1 * UCS/ 0.9
Tensile strength (splitting)
= Tensile strength / 0.9
= (0.3 *UCS2/3)/ 0.9
Belgian Building Research Institute – http://www.bbri.be
18 14 ARC Hong Kong - Workshop TC 211
3.2 Durability
Topics: - Mechanical characteristics:
• UCS, E, T in function of the time
• Creep Type of soil, σ, T°, cement type, humidity (RH), W/C
- Influence of environment:
• Degradation related to air-exposure
Humidity, porosity, pH and carbonation in function of the time
• Corrosion – carbonation Air-exposure or above the ground water
• Setting and hardening in polluted soils and in saltwater Internal and/or external pollution
• Corrosion – pollution Chlorides
SOIL MIX Project
3. Test results
Belgian Building Research Institute – http://www.bbri.be
-1200
-1000
-800
-600
-400
-200
0
2000 30 60 90 120 150 180 210 240 270 300 330 360 390 420
Defo
rmations (
µS
train
s)
Time (days)
2A1
2B1
2C1
2A2
0 kN
15 kN 20 kN 25 kN
30% UCS
40% UCS 50% UCS
19 14 ARC Hong Kong - Workshop TC 211
Creep Under water (T=20±4°C)
CSM – Leuven
Tertiary sand
UCS = 5.9 MPa
Age = 146 days Swelling caused by water absorption
Which humidity conditions?
3.2 Durability
SOIL MIX Project
3. Test results
Belgian Building Research Institute – http://www.bbri.be
20 14 ARC Hong Kong - Workshop TC 211
Cement content
Chemical determination: SiO2, CaO, CO2 and insoluble residue
CSM – Zeebrugge – quaternary sand - Parameters:
W/C Grout density
- Cement content: Injection volume <-> return?
Injected grout volume (kg/m³)
Depth
(m
)
W/C = 1.2
Grout density
= 1428 kg/m³
3.2 Durability
SOIL MIX Project
3. Test results
Belgian Building Research Institute – http://www.bbri.be
21 14 ARC Hong Kong - Workshop TC 211
Porosity NBN B15-215 Soil mix between 30 and 65 vol%
Microscopic analysis (thin films) –
fluorescent light (LM 3445)
“Microporosity” of cement
30
40
50
60
70
800 1000 1200 1400 1600 1800 2000 2200
Poro
sity (
%vol)
Density (kg/m³)
Knokke
Nieuwpoort
Leuven
Roeselare
Kattendijksluis
Aalst
Duffel
Antwerpen
Dry density
Wet density
P
S
C
P = pore, S = sand, C = porous cement
High capillary porosity (high W/C)
High creep for RH = 60%
3.2 Durability
SOIL MIX Project
3. Test results
Belgian Building Research Institute – http://www.bbri.be
1.0E-12
1.0E-11
1.0E-10
1.0E-09
1.0E-08
1.0E-07
30 40 50 60 70
Pe
rme
ab
ilit
y (
m/s
)
Porosity (vol%)
Columns firm a
CSM firm c
CSM firm d
22 14 ARC Hong Kong - Workshop TC 211
3.3 Permeability
Permeability DIN 18130-1 Laboratory tests for determining the coefficient
of permeability of soil
Porosity – Permeability
9 sites in Belgium
In situ permeability?
SOIL MIX Project
3. Test results
Belgian Building Research Institute – http://www.bbri.be
0
20
40
60
0 4 8 12 16 20
Pu
ll-o
ut
(kN
)
Displacement (mm)
Smooth bar f=30mm
23 14 ARC Hong Kong - Workshop TC 211
3.4 „Steel-soil mix‟ adherence
In situ pull-out tests (inspired by NBN EN 15184)
Displacement measurement
Profile
Hollow dynamometer
Hollow jack
Reaction device
CSM – Leuven – sand
Tpeak
Tresidual
SOIL MIX Project
3. Test results
Belgian Building Research Institute – http://www.bbri.be
Mechanical characterization: - Sampling - UCS, E, T - Curing time - Inclusion analysis
Laboratory tests >< gaps
+ Tests on blocks (large scale) Representativeness of the cores (inclusion >1/6D) ? Characteristic UCS-value
24 14 ARC Hong Kong - Workshop TC 211
5. Perspectives of the SOIL MIX – IWT 080736 project
Bending tests? NDT (sonic, sclerometer,...) ? SLT?
Permeability Laboratory tests >< gaps In situ permeability?
„Steel-soil mix‟ adherence: + In situ tests
Durability : Mechanical characterization: - UCS, E, T = f(t) - Cement content - Porosity + Creep tests
Minimal humidity condition ?
Influence of the environment: - Degradation ? - Pollution/Saltwater ? - Corrosion ? - Freeze/thaw ?
Temporary retaining structure – permanent – bearing capacity
SOIL MIX Project
Belgian Building Research Institute – http://www.bbri.be
25 14 ARC Hong Kong - Workshop TC 211
3 papers describing the results of the
SOIL MIX – IWT 080736 project:
SOIL MIX walls as retaining structures –
Belgian practice
SOIL MIX walls as retaining structures –
mechanical characterization
Mechanical characterization of SOIL MIX
material – procedure description
www.bbri.be/go/IS-GI-2012
5. Perspectives of the SOIL MIX – IWT 080736 project
SOIL MIX Project
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