Liquefaction Susceptibility of Reclaimed Calcareous Sand ...
Transcript of Liquefaction Susceptibility of Reclaimed Calcareous Sand ...
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Alaa K. AshmawySchool of Engineering
Liquefaction Susceptibility of Reclaimed Calcareous Sand Deposits
MAKING WAVES IN GEOTECHNICAL ENGINEERING Celebrating the career and achievements of V.P. Drnevich
Purdue University – May 1st, 2010
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Land Reclamation Projects in Dubai
5 miles
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Construction-Geotechnical Challenges
Reclamation done by rainbowing
seabed dredge material
Deposits consisting mainly of
calcareous sand with shell
fragments
Post-fill densification by
vibrocompaction
Surface layer of compacted fill
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Seismic risk
Dubai falls in low seismic hazard zone
Seismographic data – limited to none
Seismic geology data – abundant but proprietary
Design PGA = 0.25 g (under revision)
Cyclic test data on local sand – very limited
Liquefaction behavior of calcareous sand – limited
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Geologic Faults - UAE
Source: Ziegler (2001) GeoArabia, Vol. 6, No. 3.
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Vibrocompaction Data
Information collected from six reclaimed land sites in the
UAE
Data includes site layout, as well as locations of CPT and
SPT before and after vibrocompaction
Data can be used to evaluate soil profile vis-à-vis
liquefaction resistance, as well as spatial variability
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Geotechnical Data
Dense vibrocompaction grid
Hundreds of CPT profiles, both pre and post densification
Post densification CPT taken at fixed locations relative to
the vibrocompaction grid
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Liquefaction susceptibility of calcareous sand
Calcareous sands are much more susceptible to particle
crushing. As a result, CPT values are low
Need for undrained cyclic testing to properly define CSR
required to cause liquefaction
Discrete element modeling and image analysis of grain
shape can assist in evaluating liquefaction susceptibility of
calcareous sand
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Liquefaction Potential Assessment from CPT
Robertson & Wride, 1998
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Spatial Variability Pre and Post Densification
0
2
4
6
8
10
12
14
0 20 40 60
qc (MPa)
Depth
(m
)
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Quantification of Spatial Variability
Cross correlation of CPT soundings results in cross-
correlation functions of different characteristics
Similarity descriptors are obtained from the cross-
correlation function (Rabens 2000)
Technique used to determine best location for
subsequent CPT soundings
Can be extended to define spatial variability of site
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Implementation at Site A – Palm Jumeirah
Area
Mean
Mode
Standard Deviation
Skewness
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Acknowledgements
Shad Khan, Guido Freitag (Keller Grundbau)
Kathryn Gunberg, Russell Green (Virginia Tech)
Guy H. Rabens (UES Florida)