Concrete & DEEP FOUNDATIONS - Betonica · – Cast-in-situ • Bored – CFA – Kelly •...
Transcript of Concrete & DEEP FOUNDATIONS - Betonica · – Cast-in-situ • Bored – CFA – Kelly •...
Ir Maurice Bottiau
Concrete &DEEP FOUNDATIONS
Deep Foundations
Piling• Driven
– Precast– Cast-in-situ
• Bored– CFA– Kelly
• Displacement auger
Soil Improvement• Injections• Stone columns• Jetgrouting• Rigid inclusions• Soilmix
Retaining walls• Diaphragm
walls• Pile walls• Soilmix
Driven piles
Bored piles
Secant pile walls
Diaphragm walls
Foundation performance
It’s all about reliability
Soil type Construction Monitoring and testing
Soil characteristics
Importance of soil characterizationIntermediate or particular soil types
Layered conditions
Deep Foundation construction
Systems and installation parametersEquipment
Materials
Monitoring & Testing
Document pile installationCheck design and/or execution
Detect defaults
Codes : European execution codes
• Deep Foundations construction : – CEN TC 288 : Execution of
special geotechnical works(1992)
• Concrete :– TC 104 : NBN EN 206-
1:2013 and its annex D.• Testing:
– TC 341 :
EN 1536EN 1537EN 1538EN 12063EN 12699EN 12715EN 12716EN 14199EN 14475EN 14490EN 14679EN 14731EN 25237
Bored PIlesInjection AnchorDiaphragm Wall
Sheet PileDisplacement Pile
InjectionsJet GroutingMicro PIles
Reinforced EarthSoil Nailing
Deep Soil MixingDeep Vibro Densification
Vertical Drain
Deep Foundations and…
CONCRETE
Deep Foundations and concrete
Deep Foundations classification w.r.t concrete
Direct casting under gravity• Driven Cast-
in-situ• Some
displacement auger
Tremie pipe casting• Bored piles• Diaphragm
walls
Pumping through hollow stem • Augercast (CFA)• Cased auger
(pile walls)• Some
displacement auger
Direct casting under gravity
Execution sequence
Typical diameter driving tube and bottom plate (mm)273 (310, 330)300 (330, 350, 365)323 (365, 380, 400)365 (400, 410, 435)380 (435, 450, 465)406 (465, 480, 500)457 (520, 535, 560)508 (560, 580, 615)559 (615, 640, 660, 680)610 (660, 680, 710, 740)
Driven cast in situ concrete pile
Displacement cast in situ augercast type ATLAS
Direct casting under gravity
• Usually limited to diameters < 650 mm.• Casting “in dry conditions” but concrete
directly in contact with water and soil.• Plastic concrete with high resistance against
segregation.• Attention to bleeding due to installation
process (=displacement).
Pumping through hollow stem
Cased Augercast (FOW) piles
Pumping through hollow stem
• Augercast systems• Difference between closed and open circuits.• High slump concrete > 180 mm• Usually placed in submerged conditions• Usually small quantities of concrete per pile : 1-4
m³/pile.• Mixers stay on site for 2-4 hours…• Placement of reinforcement cage in fresh
concrete
Tremie pipe casting
Bored piles
Principle of execution
Bruface, Geotechnical Eng., C. Bauduin
BORED PILES
Concrete for bored piles
Diaphragm walls
Diaphragm walls
• Pour through tremie pipe to avoid segregation
• Pipe at pile/excavationbottom, concrete pushes aside residues and not cleaned deposits on bottom
• Continuous concrete pouring operation while tremie pipe remains 1,5 to 2 m in fresh concrete; pipe is retracted during pouring
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Tremie Concreting Process
Tremie pipe casting
• For large diameter bored piles and diaphragm walls.• High slump concrete.• Usually placed under submerged conditions• Large quantities (sometimes > 200 m³)• Concreting cadence : 50 to 80 m³/h• Concrete should remain workable through the whole
process. Attention to timeframe!• Concrete should be able to completely fill the
excavation and embed any reinforcement or box-out
D wall concreting process
D wall concreting process
• Concrete surface should be kept as horizontalas possible.
• Three measurement points.
D Wall concreting process
• Placement is usually in wet conditions• Sometimes casted at large depths (> 50 m), or pumped
on long distances• Through small diameters tremie pipes or hollow stem
of augers.• Against soil and/or supporting fluid• Sufficiently workable to fill the voids created by the
tubes/tools or present in the surrounding soil• Technological aspects linked with reinforcement
/cover/tolerances…• Attention to supply cadences and continuity
Deep Foundations and concrete
Concrete for Deep Foundations-General requirements (1)
Special properties in concrete’s fresh stage (during the casting process) :• completely fill the excavation and embed any
reinforcement or box-out, • allow self-levelling and self-consolidation, • not undergo excessive segregation, bleeding,
or filtration
Rheology
• Rheology determines the success of placement and the quality of the final product.
• The key rheological characteristics are:-– Workability (ability to completely fill the excavation
and compact by gravity);– Flow retention (how long specified fresh properties
will be retained); and– Stability (resistance to segregation, bleeding and
filtration).
Concrete for Deep Foundations-General requirements (2)
Design of concrete mix:• durability in addition to strength • tendency to specify
– higher strength classes (C35/45)– lower water/cement ratios.
• Higher dependence on chemical admixtures
5 components concrete mix
• Revised version of NBN EN 206-1:2013 : specification, performances, production and conformity of concrete
• Annex D : additonnal requirements for concrete for special geotechnical works(formerly in EN 1536:2010 and EN 1538:2010)
Revision of EN 206-1
Concrete for deep foundations
Mix proportions (acc EN 1536)Cement content
− Placement in dry conditions
− Placement in submerged conditions
≥ 325 kg/m³
≥ 375 kg/m³Water – cement ratio (W/C) < 0,6Fines content, d< 0,125( mm (inclusive cement)
− Coarse aggregate d > 8mm
− Coarse aggregate d≤ 8 mm
≥ 400 kg/m³
≥ 450 kg/m³
Consistency rate for fresh concrete in different conditions (acc EN 1536)Flow diameter range
mm
Slump range
mm
Typical conditions
(examples)500 150 Concrete placed in dry conditions560 180 Placed by pumping or
Concrete placed in submerged conditionsunder water by tremie
600 200 Concrete placed by tremie in submergedconditions under a stabilising fluid
Note: the measured slump (H) or flow diameter Φ is to be rounded up to the nearest10 mm
BORED or DISPLACEMENT PILES Concreting mix and propertiesaccording NBN EN 206-1:2013 - annex D
ABEF/CSTSC specs for D Walls
Control and testing
Controls on site• Rheology
– Rheometer• Workability
– SFlow table test acc. to EN 12350-5– Slump test acc. to EN 12350-2, ASTM
C143– Slump Flow test acc. to EN 12350-8,
ASTM C1611– L-Box test acc. to EN 12350-10
• Workability time– Knead bag test
• Stability– Static Segregation or Washout test acc.
to ASTM C1610– Bleeding test acc. to EN480-4, ASTM
C232 – Visual Stability Index Test (VSI) acc. to
ASTM C1611– Concrete Filter Press test acc. to tone –
Betone mit Konsistenz ≥ F 59– Bauer filter press acc. to Australian
Tremie Handbook
Tests after execution• Direct Testing methods
– Coring within the foundation – Closed circuit television (CCTV)
inspection of the foundation and its base, inside a drilled hole.
– Excavation to inspect the surface of the foundation.
– Extraction of a pile.
• Cross hole sonic logging• Thermal Integrity Profiling• Gamma logging
Control Timeframe
Bauer test
• Principle: The test simulates the water retention ability of fresh concrete under hydrostatic pressure and determines the filter loss through a filter.
• Procedure: A cylindrical container is filled with 1.5 l of fresh concrete and pressurized with compressed air (5 bar). The water which separates from bulk concrete through a filter paper is collected at the bottom of the container in a cylinder. The recorded filter loss is a measure for filter stability of the concrete.
Bored piles testing
• NDT : Non-Destructive Test methods to evaluate structural integrity is pulse echo or low strain testing
• CSL : Crosshole Sonic Logging uses the propagation time and relative energy of an ultrasonic pulse
• Core drilling of the base of the pile (or the defect zone identified by CSL)
TIP: Thermal Integrity Profiling (TIP)
Materials and execution processare closely linked…
…and should remain in the samehands!
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Concrete is key in structural capacityand essential to Deep Foundation Performance
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Concrete for Deep Foundations:• Specific requirements• Specific delivery aspects• Specific testing methods
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Deep foundations specialistswant to keep the full control of the deliveries!
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