15th ICSMFE: Workshop

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15th ICSMFE Workshop 7organised by
TC2Centrifuge TestingSome Achievements and
ChallengesMalcolm BoltonCambridge University
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What are the unique selling points of
centrifuge testing?

• Cheap replication of the response of
  geo-structures
• Weight-induced stresses gradients and rotations
• Coupling of intergranular and pore fluid
  pressures
• Access to severe distortions, drainage of clay,
  3D
• Realistic boundary conditions
• free surface, cracks
• soil-structure compatibility
• seismic shaking

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Some achievements actuators

• CITY University tunnelling kit
• TIT excavator
• NUS compaction sand piler
• UWA-COFS drag anchor deployment
• TUD wave generator
• CCORE static liquefaction actuator
• UCD earthquake simulator
• CU-SC atmospheric chamber

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CITY U. tunelling
slip rings
swinging platform
motor
Acutronic 661 Centrifuge
model container
clay sample with targets on front surface
swinging platform
swing hangers
perspex window
camera
lights
tunnel
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3D Surface settlements from digital image analysis
(a) left camera
(b) centre camera
(c) right camera
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TIT excavator
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NUS sand piler
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UWA - COFS drag anchor deployment
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TUD wave generator
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Liquefaction Event Geometry and Instrumentation
Settlement Gauge Piezometer
Clay Embankment
Contained
Compacted Sand
DAS
Sand
BBW Sand Deposit
BAW Sand Deposit
Tilt Sections
CANLEX
CCORE static flowslide actuator
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UCD earthquake shaker
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Some challenges

• Replicating the mechanics of processes
• Broadband data stream to characterise soil
  response
• Realistic soil profiles - grading, layering, OCR
  etc
• Assessment of size and rate effects
• The atmospheric boundary condition

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Atmospheric loading of embankments boundary
conditions
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Atmospheric loading of embankments boundary
conditions
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Atmospheric loading of embankments boundary
conditions
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Atmospheric loading of embankments pore water
pressures
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Atmospheric loading of embankments pore water
pressures
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Atmospheric loading of embankments pore water
pressures
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Atmospheric loading of embankments cyclical
deformations
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Modes I and II fracture mechanics
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PIV reveals slope deformation mechanisms
And remember - this was not collapse
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Rubblisation
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Discussion point

• We must not make complex models just for fun
• Our task is to reproduce essential complexity
• And then observe events intensively
• Ground layering is sometimes essential
• Anisotropy may be essential, and is automatic
• Construction process is essential
• In clays, the atmospheric boundary may be
  essential
• We need to make simple mechanistic models
• Numerical simulation would be useful but lags
  behind, and can not therefore be considered
  essential..