TA project: FLIQ

Click here to watch a video from the FLIQ tests.

Click here to read the final report of the FLIQ project.

A concise presentation of the project's aim and main outcomes is available in the Joint brochure of the TA facilities.

TITLE OF PROPOSAL: 
Experimental Verification of Shallow Foundation Performance under Earthquake-induced Liquefaction

HOST TA FACILITY: 
Turner Beam Centrifuge, Cambridge, UK

TA AGREEMENT BETWEEN USERS AND FACILITY:
3 February 2010

STARTING DATE:
November 2010

END DATE:
July 2011

NO. OF USERS (researchers):
4

LEAD USER:
George Bouckovalas - National Technical University of Athens (Greece)

ADDITIONAL USERS:
Achilleas Papadimitriou - University of Thessaly (Greece)
Ernesto Cascone - University of Messina (Italy)
Dimitios Loukidis - University of Cyprus

 Typical centrifuge model configuration

SUMMARY OF PROPOSED RESEARCH:

Research Outline:
Perform a series of centrifuge experiments simulating the seismic response (settlement accumulation and static bearing capacity degradation) of a square footing resting upon a two layer soil profile: a thin top layer of non-liquefiable soil crust overlaying a thick layer of liquefiable sand. The base excitation will be harmonic, while the main problem variables will be: (a) the thickness of the non-liquefiable soil crust Hcrust= 0.5B, B and 1.5B (B is the footing width), and (b) the average bearing pressure of the footing (q), which translates into the pre-shaking static Factor of Safety.

Scope:
Verify extensive theoretical research on performance-based design criteria for surface foundations resting upon liquefiable soils, previously carried out by the proposing team. This research has been based upon fully coupled, dynamic, elastoplastic numerical analyses, with critical state modeling of soil element response, properly calibrated against laboratory test (cyclic triaxial and simple shear tests). Nevertheless, the end results of this research (design charts and multi-variable relations) have never been verified against well-controlled physical models, but only case-studies from the literature with less than adequate documentation.

Expected outcome:
A theoretically and experimentally documented set of criteria for the performance-based design of surface foundations resting upon liquefiable soils with a nonliquefiable soil crust.

Significance:
The use of appropriately designed surface foundations in liquefiable soils, meeting safely the allowable settlement and bearing capacity requirements, may replace the more expensive use of combined pile foundations and soil improvement, commonly followed in practice today, at least for relatively light structures (with q=100-150 kPa).

 

In-flight images of the punching of the footing, immediately after soil liquefaction

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

What's next

Series logo small   SERIES Concluding Workshop
  Joint with US-NEES "Earthquake Engineering Research Infrastructures

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