2936
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
undrained shear strength. Similarly, the horizontal line
represents the mean value
s
u
estimated of each soil.
The calculated results from Equation (7) are included in
Figure 4(c). Values are generally higher than those of the
preceding Figures 4(a) and 4(b), this can be understood as such
calculation does not take into account the theoretical solution
(Equation 1), and the roughness of the pipeline is implied by the
value of the coefficient
a
and the exponent
b
of the numerical
curve fitting. In this case, the average value of the coefficient is
a
=5.12 with a standard deviation of
±0.48, to the exponent
average value of
b
=0.32 and
±0.09. Figure 5 shows the
variation of
a
and
b
values.
Experimental tests were performed on two soils with
different undrained shear strength, the results are close to the
value of
s
u
obtained with a laboratory miniature vane.
The standard deviation of the experimental results of this
paper is relatively high, which encourages study with a larger
number of soils.
One limitation of the test is the depth shallow for soil
characterization, however it is considered appropriate for the
case of marine pipeline design.
The estimated values of the undrained strength and standard
deviation for each soil are included in Table 2. There are
similarity of the values calculated from equations (4) and (6)
and roughness respectively. For the type of power adjustment,
which represents a simple solution compared to the strict
theoretical equation, the values are generally higher. It is
important to note that the value of the standard deviation is
high, which encourages to study this alternative to estimate
experimental undrained shear strength with a large number of
experimental test for different soils with different undrained
shear strength.
6 ACKNOWLEDGEMENTS
The authors acknowledge the
GéO
team of the
Laboratoire
3S-R
at Grenoble, France, for the facilities and support to
perform the experiments.
7 REFERENCES
AFNOR. 1990.
Essai scissométrique en laboratoire, sols:
reconnaissance et essais
, Norme NF P 94-072, Association
Française de Normalisation, Paris, La Défense, 325-337.
The technique using cylinders penetration in order to obtain
the soil shear strength provides good results, one limitation is
consider the undrained strength constant with depth.
Aubeny C.P., Shi H. and Murff J.D. 2005. Collapse load for cylinder
embedded in trench in cohesive soil,
International Journal of
Geomechanics
, Vol. 5(4), 320-325.
Equihua-Anguiano L.N., Orozco-Calderon M. and Foray P. 2012.
Numerical finite element method and experimental study of uplift
capacity anchors,
Seventh International Conference on Offshore
Site Investigation and Geotechnics, OSIG 2012
, London, U.K.
0
0.2
0.4
0.6
0.8
0
2
4
6
8
0
2
4
6
8 10
Exponent
b
Coefficient
a
Test No.
a b
Hansbo S. 1957. A new approach to the determination of the shear
strength of clay by the fall-cone test, Stockholm: Royal Swedish
Geotechnical Institute, Proceedings 14.
ISSMGE-TC1 2005. Geotechnical and geophysical investigations for
offshore and near shore developments, TC1, ISSMGE.
Murff J.D., Wagner D.A. & Randolph M.F. 1989. Pipe penetration in
cohesive soil,
Géotechnique
Vol. 39(2), 213-229.
Orozco-Calderon M. 2009.
Etude de l’interaction cyclique sol-pipe dans
les grands fonds marins
. Thèse, Institut Polytechnique de Grenoble,
Laboratoire Sols, Solides, Structures – Risques, France.
Figure 5. Variation coefficient
a
and exponent
b
for all experimental
tests, obtained from fitting of experimental values with equation (2).
Orozco-Calderon M. and Mendoza M.J. 2002. Quick and reliable
determinations of water content, liquid limit and undrained shear
strength for fine-grained soils (in Spanish),
XX National Meeting of
Soil Mechanics
, SMMS, Oaxaca, Mexico, Vol. 2, 53-62.
Table 2. Values of the average undrained shear strength calculated from
ertical penetration tests cylinder models.
Puech A., Orozco-Calderon M. and Foray P. 2010. Mini Tbar testing at
shallow penetration,
Proceedings Frontiers in Offshore
Geotechnics II
, Perth, W.A., Australia, 305-310.
Stewart D.P. and Randolph M.F. 1991. A new site investigation tool for
the centrifuge,
Proceedings of CENTRIFUGE 91
, 531-538.
v
Equations
(4)
(6)
(4) &
(6)
(7
)
So
il No.
Value
s*
=
0
=
1
=0
=
1
=0
and 1
...
u
s
(kPa)
7.0
5.8
7.
3
5.
9
6.5
7.
9
1
±
(kPa)
0.9
0.6
0.
8
0.
6
1.0
0.
8
u
s
(kPa)
2.9
2.4
3.
0
2.
4
2.7
3.
2
2
±
(kPa)
0.5
0.3
0.
4
0.
3
0.3
0.
2
*
u
s
: average undrained shear strength,
: standard deviation.
5 CONCLUSIONS
This article presents experimental tests, as an option to obtain
the undrained shear strength of soft soils using vertical
penetration of a cylinder into the soil.
Experimental results takes into account theoretical solution
for a pipe penetrated in a homogeneous medium, characterized
by a constant undrained strength with depth.
