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1
TC-211 ISSMGE
ETH ZÜRICH
COLLOQUIUM ON GROUND IMPROVEMENT
ZÜRICH – 24 October 2013
Concept & Geotechnical parameters for the
Design and Control of major ground
improvement works around the world
Serge VARAKSIN
Chairman T.C. Ground Improvement (TC 211)
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Thursday 31 May & Friday 1 June - International Symposium : Publications
4 Volumes >1600 pages VOL I : 7 general reports – 2 specialty lectures VOL II-III-IV = >140 papers
Contribution WTCB-CSTC - Edition of the 4 Volumes (N. Denies & N. Huybrechts) - Vol I :General report “Deep mixing” – 40 p. summary of 30 papers - Vol III : 4 publications with regard to BBRI soil mix research (54 p.)
www.bbri.be/go/tc211 [email protected]
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Vane test (VT)
Static Cone Penetration Test (CPT)
Dynamic Penetration Test (SPT)
Pressuremeter (PMT)
Parameters related to ground improvement : Differents types of in situ tests
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State of the Art Report
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Category Method Principle A1. Dynamic compaction Densification of granular soil by dropping a heavy weight from air onto ground. A2. Vibrocompaction Densification of granular soil using a vibratory probe inserted into ground. A3. Explosive compaction Shock waves and vibrations are generated by blasting to cause granular soil ground
to settle through liquefaction or compaction. A4. Electric pulse compaction Densification of granular soil using the shock waves and energy generated by electric
pulse under ultra-high voltage.
A. Ground improvement without admixtures in non-cohesive soils or fill materials A5. Surface compaction (including rapid
impact compaction). Compaction of fill or ground at the surface or shallow depth using a variety of compaction machines.
B1. Replacement/displacement (including load reduction using light weight materials)
Remove bad soil by excavation or displacement and replace it by good soil or rocks. Some light weight materials may be used as backfill to reduce the load or earth pressure.
B2. Preloading using fill (including the use of vertical drains)
Fill is applied and removed to pre-consolidate compressible soil so that its compressibility will be much reduced when future loads are applied.
B3. Preloading using vacuum (including combined fill and vacuum)
Vacuum pressure of up to 90 kPa is used to pre-consolidate compressible soil so that its compressibility will be much reduced when future loads are applied.
B4. Dynamic consolidation with enhanced drainage (including the use of vacuum)
Similar to dynamic compaction except vertical or horizontal drains (or together with vacuum) are used to dissipate pore pressures generated in soil during compaction.
B5. Electro-osmosis or electro-kinetic consolidation
DC current causes water in soil or solutions to flow from anodes to cathodes which are installed in soil.
B6. Thermal stabilisation using heating or freezing
Change the physical or mechanical properties of soil permanently or temporarily by heating or freezing the soil.
B. Ground improvement without admixtures in cohesive soils
B7. Hydro-blasting compaction Collapsible soil (loess) is compacted by a combined wetting and deep explosion action along a borehole.
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C1. Vibro replacement or stone columns Hole jetted into soft, fine-grained soil and back filled with densely compacted gravel or sand to form columns.
C2. Dynamic replacement Aggregates are driven into soil by high energy dynamic impact to form columns. The backfill can be either sand, gravel, stones or demolition debris.
C3. Sand compaction piles Sand is fed into ground through a casing pipe and compacted by either vibration, dynamic impact, or static excitation to form columns.
C4. Geotextile confined columns Sand is fed into a closed bottom geotextile lined cylindrical hole to form a column. C5. Rigid inclusions (or composite foundation, also see Table 5)
Use of piles, rigid or semi-rigid bodies or columns which are either premade or formed in-situ to strengthen soft ground.
C6. Geosynthetic reinforced column or pile supported embankment
Use of piles, rigid or semi-rigid columns/inclusions and geosynthetic girds to enhance the stability and reduce the settlement of embankments.
C7. Microbial methods Use of microbial materials to modify soil to increase its strength or reduce its permeability.
C. Ground improvement with admixtures or inclusions
C8 Other methods Unconventional methods, such as formation of sand piles using blasting and the use of bamboo, timber and other natural products.
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g D2. Chemical grouting Solutions of two or more chemicals react in soil pores to form a gel or a solid
precipitate to either increase the strength or reduce the permeability of soil or ground. D3. Mixing methods (including premixing or deep mixing)
Treat the weak soil by mixing it with cement, lime, or other binders in-situ using a mixing machine or before placement
D4. Jet grouting High speed jets at depth erode the soil and inject grout to form columns or panels D5. Compaction grouting Very stiff, mortar-like grout is injected into discrete soil zones and remains in a
homogenous mass so as to densify loose soil or lift settled ground.
D. Ground improvement with grouting type admixtures
D6. Compensation grouting Medium to high viscosity particulate suspensions is injected into the ground between a subsurface excavation and a structure in order to negate or reduce settlement of the structure due to ongoing excavation.
E1. Geosynthetics or mechanically stabilised earth (MSE)
Use of the tensile strength of various steel or geosynthetic materials to enhance the shear strength of soil and stability of roads, foundations, embankments, slopes, or retaining walls.
E2. Ground anchors or soil nails Use of the tensile strength of embedded nails or anchors to enhance the stability of slopes or retaining walls.
E. Earth reinforcement
E3. Biological methods using vegetation Use of the roots of vegetation for stability of slopes.
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8 ZÜRICH – 24.10.2013
Why Soil improvement ?
•To increase bearing capacity and stability (avoid failure)
•To reduce post construction settlements
• To reduce liquefaction risk (sismic area)
• avoid deep foundation (price reduction also on structure work like slab on pile)
• avoid soil replacement
• save time
•Avoid to change site
•Save money !
Advantages / classical solutions
Laboratory Engineering Properties
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9 ZÜRICH – 24.10.2013
Cohesive soil Peat , clay … Soil with friction Sand , fill
Without added materials
With added materials
1 Drainage 2 VAcuum
3 Dynamic consolidation 4 Vibroflottation
4 Dynamic replacement 5 Stone columns 6 CMC 7 Jet Grouting 8 Cement Mixing
Soil Improvement Techniques
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-Soil caracteristics -cohesive or non cohesive
- blocks ? - Water content, water table position - Organic materials -Soil thickness -Structure to support
-Isolated or uniform load -Deformability
-Site environment
-Close to existing structure
-Height constraints
-Time available to build
Parameters For Concept
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σ=σ’+u
high fines contents soils
Preloading with vertical drains
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Radial and Vertical consolidation
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High fines contents soils
5 cm , PVC vertical drain + geotextile Flat drain circular drain
Vertical drains: material
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Vertical Drains
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VACUUM (J.M. COGNON PATENT)
Vacuum Consolidation (high fines contents soils)
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Case history – EADS Airbus Plant, Hamburg
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General overview of Airbus site
Case history – EADS Airbus Plant, Hamburg
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Dyke construction to +6.5 in 8.5 month and to + 9.00 in 16 month
Columns GCC
Settlement 0,7 – 1.84 m
Settlement ≥ 2,0 – 5,5 m
Temporary sheet pile wall – in 5 month – dyke construction in 3 years
Dyke construction to +6.5 in 8.5 month and to + 9.00 in 16 month
Columns GCC Settlement 0,7 – 1.84 m
Settlement ≥ 2,0 – 5,5 m
Basic design and alternate concept of Moebius–Menard
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Subsoil characteristics
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Case history – EADS Airbus Plant, Hamburg
How to move on the mud !
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Case history – EADS Airbus Plant, Hamburg
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22 ZÜRICH – 24.10.2013
Case history – EADS Airbus Plant, Hamburg
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23 ZÜRICH – 24.10.2013
Dev
iato
ricSt
ress
(q
)
Mean Stress (p’)
Ko (εh = 0)
Kf (failure line)
Surcharge
σ’1= 80kPa
σ’2 = 40kPaσ’3 = 40kPa
Vacuum Consolidation
Active Zone εh < 0
Passive Zone εh > 0
Surcharge
p’ = 2/3 σ’1 Ko = 0.5
σ’1= 80kPa
σ’2 = 80kPaσ’3 = 80kPa
Vacuum
p’ = σ’1 ; Ko = 1 Isotropic
Dev
iato
ricSt
ress
(q
)
Mean Stress (p’)
Ko (εh = 0)
Kf (failure line)
Surcharge
σ’1= 80kPa
σ’2 = 40kPaσ’3 = 40kPa
Vacuum Consolidation
Active Zone εh < 0
Passive Zone εh > 0
Surcharge
p’ = 2/3 σ’1 Ko = 0.5
σ’1= 80kPa
σ’2 = 80kPaσ’3 = 80kPa
Vacuum
p’ = σ’1 ; Ko = 1 Isotropic
Dev
iatio
n St
ress
(q’)
Stress path for Vacuum Process
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24 ZÜRICH – 24.10.2013
Case history : Kimhae (Korea) - 1998
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25 ZÜRICH – 24.10.2013
Cohesive soil Peat , clay … Soil with friction Sand , fill
Without added materials
With added materials
1 Drainage 2 VAcuum
3 Dynamic consolidation 4 Vibroflottation
4 Dynamic replacement 5 Stone columns 6 CMC 7 Jet Grouting 8 Cement Mixing
Soil Improvement Techniques
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26 ZÜRICH – 24.10.2013
Nice airport runway consolidation
Very high energy (200 t , 24 m)
Granular soil
Case History
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Concept and application of ground improvement for a 2,600,000 m²
KAUST PROJECT
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Discovering the Habitants
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AREAS TO BE TREATED
•AL KHODARI (1.800.000 m2) •BIN LADIN (720.000 m2)
SCHEDULE
• 8 month
Areas to be treated
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30 ZÜRICH – 24.10.2013
Shock waves during dynamic consolidation – upper part of
figure after R.D. Woods (1968).
Dynamic Consolidation
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31 ZÜRICH – 24.10.2013
+ 1.2
+ 2.5
+ 4.0
2 meters arching layer
Depth of footing = 0.8m Below G.L.
Working platform (gravelly sand)
Compressible layer from loose sand to very soft sabkah
Engineered fill
0 to 9 meters
150 TONS
σz = 200 kn/m²
Concept
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0
+1
+2
+3
+4
+5
-5
-4
-3
-2
-1
-10
-9
-8
-7
-6
LAGOON FILLED BY SABKAH
RED SEA
ELEVATION (meters)
TYPICAL SITE CROSS SECTION OF UPPER DEPOSITS
+3
SITE ≅ 1,5 km
CORAL
BARRIER
LAYER USC w % % fines N QcBARS
FR % PLBARS
EPBARS
1 - SABKAH SM + ML 35-48 28-56 0-2 0-2 1,2-4 0,4-1,9 avr-17
2 - LOOSE SILTY SAND SM - 15-28 3-9 12-45 0,5-1,2 2,1-4 18-35
3 - CORAL - 26-35 - 6-12 - - 5,1-7,2 35-60
4 - LOOSE TO MED DENSE SAND SM - 12-37 3-18 15-80 0,5-1,8 4-12 28-85
Specifications
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Typical surface conditions
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BASIS
•60 grainsize tests
•180 PMT tests
PARAMETERS
•PL – Po = pressuremeter limit pressure
•kJ/m3 = Energy per m3 (E)
•% = % passing n°200 sieve
•I = improvement factor
•S.I : energy specific improvement factor
LEGEND
Average pre-treatment values
Average values between phases
Average post-treatment values
SPEC DC : PL – Po ≥ 0.75 MPa
SPEC DR : PL – Po ≥ 0.18 MPa
K.A.U.S.T. – Saudi Arabia
Li
LF
PP
EI 100×
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 100 200 300 400 500
I = 8 SI = 4,7
I = 6,25 SI = 2,3
I = 5,5 SI = 1,5
I = 3,1 SI = 0,72
I = 3 SI = 0,56
Energy (kJ/m3)
PL-Po (MPa)
DC DOMAIN
DR DOMAIN
10%
20%
30%
40%
50%
SPEC DC
SPEC DR
ANALYSIS OF (PL-Po) IMPROVEMENT AS FUNCTION OF ENERGY AND FINES
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VIBROFLOTS
Amplitude 28 – 48mm
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GENERAL ARRAGEMENT COUNTERFORTS INCLUDING RECLAMATION
PORT BOTANY EXPANSION PROJECT
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38 ZÜRICH – 24.10.2013
Cohesive soil Peat , clay … Granular soil Sand , fill
Without added materials
With added materials
1 Drainage 2 VAcuum
3 Dynamic consolidation 4 Vibroflottation
4 Dynamic replacement 5 Stone columns 6 CMC 7 Jet Grouting 8 Cement Mixing
Soil Improvement Techniques
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39 ZÜRICH – 24.10.2013
-Very soft to stiff soils
-Unsaturated soft clays
-Thickness of less than 6 meters
-Arching layer available
-C, ∅, µ, Ey of soil, column and arching
layers, grid
-or PL, EP, µ of soil, column and arching
layers, grid
CONCEPT PARAMETERS
Dynamic Replacement
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Vibrator penetration Material feeding Vibration of material during
extraction
Principle of the technology - bottom feed with air tank
Stone Columns – Bottom Feed
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41 ZÜRICH – 24.10.2013
Stone Columns – Bottom Feed
Stone Columns bottom feed to 22 m depth
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Construction principles and equipment
Wet soil-cement column systems SMET Tubular Soil Mix (TSM®) system
Denies et al. Soil Mix walls as retaining structures – Belgian practice. IS-GI 2012
Typical characteristics: Water/Cement weight ratio (W/C): 0.6 to 1.2 (-) Amount of cement: 200 to 450 kg/m3 Spoil return: up to 30%
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Construction principles and equipment
Cutter Soil Mixing (CSM®) system for soil mix panels
Gerressen and Vohs. CSM-Cutter Soil Mixing – Worldwide experiences of a young soil mixing method in challenging soil conditions. IS-GI 2012 Several case histories in the proceedings of the IS-GI 2012
Typical characteristics in Belgium: Water/Cement weight ratio (W/C): 0.6 to 1.2 (-) Amount of cement: 200 to 400 kg/m3 Spoil return: up to 30%
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44 ZÜRICH – 24.10.2013
Deep mixing – EN 14679 (CEN TC 288) : field of application
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Field of applications and case histories
Barrier against liquefaction and post-liquefaction damages 3D arrangement of Geomix® caissons
Benhamou and Mathieu. Geomix Caissons against liquefaction. IS-GI 2012
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46 ZÜRICH – 24.10.2013
Cohesive soil Peat , clay … Granular soil Sand , fill
Without added materials
With added materials
1 Drainage 2 VAcuum
3 Dynamic consolidation 4 Vibroflottation
4 Dynamic replacement 5 Stone columns 6 CMC 7 Jet Grouting 8 Cement Mixing
Soil Improvement Techniques
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47 ZÜRICH – 24.10.2013
RIGID INCLUSIONS - PARAMETERS
-C’, ∅’, Ey, µ, γ, ϕ
-Kv, Kh if consolidation is considered
-Ey, µ, γ, D (non porous medium)
SOIL INCLUSION
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48 ZÜRICH – 24.10.2013
CMC – Execution
Soft soil
Grout flow
Fleet of specilized equipment Displacement auger => quasi no spoil High torque and pull down
Fully integrated grout flow control
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CMC Principle
Stress concentration
CMC
Residual stress Arch effect between the
columns CMC
Transition layer
Create a composite material Soil + Rigid Inclusion (CMC) with: Increased bearing capacity Increased elastic modulus
Transfer the load from structure to CMC network with a transition layer
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50 ZÜRICH – 24.10.2013
δ
CMC Design – Specific case of non vertical loading
Ri
Ti
Calculation principle
1/ Estimation of the vertical stress in the column (% of the embankment load),2/ Thus maximum momentum so that M / N ≤ D / 8 (no traction in the mortar),3/ Thus maximum shear force taken by the includion (similar to a pile to which
a displacement is applied),4/ Modeling of the CMC as nails working in compression + imposed shear force
under TALREN software (or equivalent).
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Future Caisson Stability Analysis
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As built conditions
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Proposed solution
Layer I Layer II
15% rock (φ = 45°) + 85% clay (Cu = 50 kPa)
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View of pounder construction
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View of pounder ready to work
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General SFT up
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After compaction actual results
φ=48 degreeAr=22%C=0kPaColumn Dia=2.4m
φ=40 degree φ=40 degree
Cu=50kPa Cu=50kPa
Cu=250kPa
φ=48 degreeAr=22%C=0kPaColumn Dia=2.4m
φ=48 degreeAr=22%C=0kPaColumn Dia=2.4m1.3m
1.3m
0.2m
Original rock surface before compaction
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58
TC-211 ISSMGE
ETH ZÜRICH
COLLOQUIUM ON GROUND IMPROVEMENT
ZÜRICH – 24 October 2013
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