596
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
city; there
n deg e
that water content w
according to Proctor test and t
ticity was used than t
latome
est of
dam. General interpretation of test results of these t
his c
erefore
stand
th tests
relev
was used
ne in CPT cone. It should be no
that there is not much experience presented in literat
d DMT testing in compacted clay.
for the
are based
Lunne et
r, exc t
for the part deeper than 9 m as measured from the crest.
That required careful cone filter saturation with glycerine.
CPT soil-type identification was done according to a
widely used chart (Robertson, 1990), and in doing so clay
of low plasticity was identified in most cases, with some
thin layers of silty clay (see plasticity chart in Fig. 2).
Pore pressures measured behind the cone (u
2
) were
almost zero, or slightly negative, in all depths.
Figure 2. The clay from the dam was of low plasti
were zones of silty clay at some depths
It was determined that generally clay compactio
was under 95 % of Proctor value,
re
as
hat
hat
a bit higher than w
opt
clay of somewhat lower plas
which was defined by the design solution.
2. CPT AND DMT TESTS
Four CPT test-boreholes and three flat di
(DMT) test-boreholes were realised, along the cr
ter
the
wo
ase
it
ard
.
ant
test types is established for natural soils, and in t
there is compacted clay – human made soil. Th
was necessary to check the applicability of
interpretation methods to compacted clay, for bo
Both tests were conducted according to
standards (EN 1997 – Part 2:2006). Glycerine
as fluid in porous sto
d te
ure
All
covering CPT an
empirical and theoretical expressions
interpretation of test results of these two tests
on natural soils (Larsson and Mulabdic, 1991,
al, 1996, Marchetti, 1980).
2.1. Soil identification
Clay in the embankment was never under wate
ep
Figure 3. DMT (M1, M2, M3) and CPT tes
dam height (c
ts (C1, C2), over the
ross-section along the crest). Both, CPT and DMT
bankment – it seems
ver the dam height;
ed Mv, and CPT test
d a sandy-silty to
clayey-silty thin
ata for undrained
ding to Marchetti
tion is related to I
d
pe it should satisfy
0.1 < I
d
< 0.6. Since the value of I
d
in compacted clay of
to be about or higher than 2
(suggesting a sandy or sandy-silty soil type), and there
ould be concluded
compacted soil
and
.
2.2. Undrained shear strength by CPT
test is calculated
et al, 1997)
tests revealed inhomogeinity in the clay em
that almost every lift of clay can be spotted o
DMT test illustrate interpreted versus requir
interpreted versus required c
u
On the other hand, DMT test detecte
silty-sandy soil type, with very rare
layers. Therefore there were almost no d
strength in DMT interpretation. Accor
(1980), soil type in DMT test interpreta
= (p
1
-p
0
) / (p
0
-u
0
), and for clay soil-ty
the dam was found
was no
in situ
pore pressure in soil, it c
that p
0
was too small, due to structure of
absence of
in situ
pore pressures
Undrained shear strength from CPT
according to common expression (Lunne
k
v
c
u
N
q s
0
(1)
Value for N
k
=15 was used in this case, which is the mean
value of proposed values for natural soils (suggested
values are N
k
=11-19), and it was confirmed to be
applicable for compacted clay as well (Fig. 4).
