Actes du colloque - Volume 4 - page 668

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Proceedings of the 18th International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
Feb-08Mar-08Apr-08May-08Jun-08Jul-08Aug-08Sep-08Oct-08Nov-08Dec-08Jan-09Feb-09 Date (mm)
-14
-12
-10
-8
-6
-4
-2
0
2
Settlement (mm)
Prediction (eq.2)
Prediction (eq.3)
PS10
PS11
CPTU M1
0.0001 0.001 0.01
60
50
40
30
20
10
0
Depth (m)
0.0001 0.001 0.01
From eq. (2) From eq. (3)
C C
Figure 6. Settlement predictions using CPTU M1 data.
Feb-08Mar-08Apr-08May-08Jun-08Jul-08Aug-08Sep-08Oct-08Nov-08Dec-08Jan-09Feb-09 Date (mm)
-14
-12
-10
-8
-6
-4
-2
0
2
Settlement (mm)
Prediction (eq.2)
Prediction (eq.3)
PS10
PS11
CPTU M2
Figure 5. Profiles of the computed C from CPTU M2 data.
According to the so derived Cαε values, a prediction of the
secondary compression settlement Ssec occurred beneath the
breakwater in the period March 2008–January 2009 has been
carried out, using the well-known equation:
  







  
ref
i
n
i t
t
H C S 10
1
sec log
 (4)
where n is the number of H i-thick homogeneous soil layers
considered in the calculation, tref = March 2008 and t = January
2009. On the basis of previous experiences on Venetian
sediment behaviour, the analysis has been performed to a depth
of approximately 40 m from sea bottom.
Figure 7. Settlement predictions using CPTU M2 data.
cases is likely to provide a useful contribution to the practice of
geotechnical engineering in the Venice lagoon area.
Figures 6 and 7 show the results obtained from the
application of the method to CPTU M1 and CPTU M2 data
respectively, together with vertical displacements measured for
the radar reflectors PS10 and PS11, located between the
selected piezocone tests (Figure 2). The figures clearly show
that eqs. (2) and (3) result in similar settlement prediction and
that the calculated trend fits fairly well the PSI-derived
settlements.
6 REFERENCES
Augustesen A., Liingaard M. and Lade P.V. 2004. Evaluation of time-
dependent behaviour of soils. Int. J. Geomechanics, 4 (3), 137–156.
Bersan S., Cola S., Simonini P., Gottardi G. and Tonni L. 2012.
Secondary compression of Venice lagoon sands and silts from
CPTU. Proc. 4th International Conference on Geotechnical and
Geophysical Site Characterization, ISC-4, Vol. 1, 383-389.
Robertson P.K. 2009. Interpretation of cone penetration tests – a unified
approach. Can. Geotechnical J. 46 (11), 1337 – 1355.
5 CONCLUSIONS
Accurate measurements of long-term settlements of a
breakwater built along the Venetian coastline, outside the
Malamocco inlet, have allowed evaluating the predictive
capability of two slightly different empirical relationships
between piezocone measurements and the secondary
compression coefficient, recently calibrated on independent data
from the Venetian lagoon.
The application of the method has provided long-term
settlement predictions which agree fairly well with measured
displacements, thus confirming the effectiveness of both
available correlations.
Research is currently focusing on the verification of such
correlations at different areas of the Venetian lagoon, using site
investigations and settlement measurements available from
other defence structures located at the Chioggia and Lido inlets.
Indeed, the validation of the proposed solutions to independent
Schneider J.A., Randolph M.F., Mayne P.W. and Ramsey N.R. 2008.
Analysis of factors influencing soil classification using normalized
piezocone tip resistance and pore pressure parameters. J. Geotech.
Geoenviron. Eng., 134 (11), 1569-1586.
Simonini P. 2004. Characterization of the Venice lagoon silts from in-
situ tests and the performance of a test embankment. 2nd Int. Conf.
on Site Characterization, ISC-2, Vol.1, 187–207.
Tonni L. and Gottardi G., 2010. Interpretation of piezocone tests in
Venetian silty soils and the issue of partial drainage. In: Deep
Foundations and Geotechnical In Situ Testing, ASCE Geotechnical
Special Publication (205 GSP), 367–374.
Tonni L. and Gottardi G. 2011. Analysis and interpretation of piezocone
data on the silty soils of the Venetian lagoon (Treporti test site).
Canadian Geotechnical Journal 48, 616–633.
Tonni L. and Simonini P. 2012. Evaluation of secondary compression of
sands and silts from CPTU. Geomechanics and Geoengineering i-
First, 1-14. DOI:10.1080/17486025.2012.726748
Tosi L., Teatini P., Bincoletto, L., Simonini P. and Strozzi T. 2012.
Integrating geotechnical and interferometric SAR measurements for
secondary compressibility characterization of coastal soils. Surveys
in Geophysics 33 (5), 907-926.