477
Technical Committee 102 /
Comité technique 102
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
5.2. Parameter evaluation
The paper from
Tumay et al.
discusses the challenge for the
effective identification of organic content in the soil based on
traditional CPT and CPTU methodologies. It is very important
to overcome this interpretation limitation since the cone is a
popular and handy tool for subsurface investigations and soil
characterization. The paper presents a comprehensive
CPT/CPTU-based organic content identification method using a
probabilistic soil classification system. The paper describes the
probabilistic method, which employs a non-traditional modeling
approach that takes the uncertainty of the correlation between
soil composition and soil behavior into account. The authors
affirmed that the use of the compositional soil classification (U)
and in-situ behavior (V) indexes for organic profiling improves
the capability of determining organic material at any given
depth. A detailed description of the proposed methodology and
the discussion of its effective application are included in the
paper.
Mulabdic´s
paper presents the use of penetration testing
devices, including the CPT and SDMT, for site characterization
of a compacted earth dam. This is a case study of a small earth
dam for which the remediation work was necessary given
construction errors and the possible damage to the earth
structure during the filling stage of the reservoir. The site
investigation campaign consisted of drilling boreholes and
carrying out in-situ tests (4 CPTs and 3 SDMTs) along the crest
of the dam, complemented with laboratory tests. The paper
focused on assessing the potential of these in-situ tests in
describing physical and mechanical properties of the compacted
(man-made) clay strata, since the traditional interpretation
methods were developed for natural soils. The authors
concluded that both CPT and SDMT clearly detected the
inhomogeneous clay conditions. They also showed remarkable
repeatability and proved to be valuable tools in characterizing
the embankment quality, both in terms of non homogeneity and
of physical and mechanical properties.
Zabielska-Adamska & Sulewska
present the use of both
static (classic) and dynamic CBR methods to establish
relationships between the bearing ratio and degree of
compaction of fly ash. The objective was the use of the
compaction degree, and also the California Bearing Ratio, as an
indicator of the soil bearing capacity in compacted material. The
dynamic CBR test is described in the paper, where fly ash
samples were compacted by the standard and modified Proctor
methods without soaking to replicate field conditions during
earth structure construction. Test results indicate that both the
dynamic CBR as well as the classic CBR are closely connected
with the characteristics of compaction, and can therefore be
used to assess the compaction of fly ash and cohesive soils. The
authors suggested that the dynamic CBR test should be widely
used as an alternative way to the classical method of quality
control to assess the subgrade capacity of the soil.
The paper from
Chapuis
discusses “scale effects” in the
permeability of sandy aquifers. The author’s initial hypothesis is
that the large-scale tests are more likely to meet preferential
flow paths, so yielding larger K values than small-scale tests,
which may be viewed as some sort of scale effect. In the paper,
the small scale was simulated via lab soil samples, the middle
scale from field permeability tests, and the large scale with site
pumping tests. The paper presents and discusses some few real
case studies, observing that for all of them the K distributions
provided consistent images of the aquifers. It was finally
concluded that scale effect was not of importance for the test
interpretation in such phreatic deposits.
Mlynarek´s et al.
paper discusses the interrelationship
between deformation moduli from CPTU and SDMT tests in
overconsolidated soils. The authors point out that glaciations in
Poland overconsolidated its deep soil layers. So, it is imperative
to take it into account in calculations of differential settlements
of structures. The paper presents deformation characteristics
estimated from CPTU and SDMT tests in clays, and focuses on
a method to identify soil preconsolidation and to establish
relationships between deformation moduli derived from CPTU
and SDMT tools. The authors concluded that the simultaneous
use of CPTU and SDMT provides a continuous picture of the
changes in stiffness of heterogeneous subsoil. They emphasized
the need for establishing specific calibration functions for each
soil type, which may be a useful tool in the construction of a
model for the subsoil’s rigidity based on G
0
or M
0
values.
Liu´s et al.
paper reports the practice and development of
the piezocone test in the geotechnical engineering field of
China. In this paper, the history and current development status
of CPT and CPTu in China practice were systematically
presented. The most used (standard) cone has the 10 cm
2
tip
area, but both 15 and 20 cm
2
CPT probes are frequently used in
China. The relationship between international standardized
CPTu and China’s CPT is based on a large data bank of testing
results related to a great number of soils. The paper presents a
comparison review of the soil characterization methods in
China, including the determination of stress history,
deformation, consolidation and permeability characteristics.
The paper from
Espinace et al.
presents their 10 years of
experience on the use of Panda
®
penetrometer to assess the
stability of Chilean’s tailings dams. The authors report around
40 cases of mechanical instability from tailing dams in Chile,
which were mainly due to liquefaction, slipping of banks, or
settlement. The paper presents the main results that have
allowed the proposition of a new methodology to control and
diagnose tailing dams. It is based on in-situ determination of the
geomechanical parameters (internal friction angle and density
index) using the Panda
®
penetrometer in order to characterize
the constituent materials and their variability. The authors also
pointed out that this methodology allows taking into account the
variability concept for stability and liquefaction risk studies
when using a probabilistic approach.
Hamza & Shahien´s
paper studies the compressibility
parameters of Egyptian cohesive soils via piezocone tests. The
major objective was to provide additional data on drained
compressibility parameters, focusing on the constrained
modulus (M
o
) and on the overconsolidation ratio (OCR) for
cohesive soils from geotechnical investigations at seven major
sites of the Nile delta river deposit in Egypt. Enhanced
propositions to estimate the OCR and M
o
for the studied clays
are presented, allowing settlement analyses to be done with the
proposed equations. The authors believe that the presented data
and correlations are a valuable contribution, since it improves
the current state of the art in estimating the compressibility
parameters of sedimentary soils with the CPTU test.
6. FINAL REMARKS
Site characterization using in-situ testing techniques has
considerably changed in the last two decades along with the
rapid transformation and advances of the technology, either by
the development of newer and economical electronic devices
operated by laptop computers or by new mathematical and
software approaches based on multi-variable, statistical or
probabilistic calculations. Besides of such remarkable
accomplishments, the traditional “old fashion” (past century….)
laboratory and site investigation methods are still widely in use,
sometimes as the preferential or unique available method. It was
clear from aforementioned review that, on the 21
st
century, the
proper site investigation, material characterization and soil
behavior prediction for the geotechnical design cannot solely
rely in one isolated test technique, or on simple “local”
unadjusted correlations that are probably not universally valid.
Higher sensorial levels of testing tools and combined
investigation procedures are surely now available that can be
