1140
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
by Thakur et al. (2006), Campbell et al. (2007) and Agus and
Schanz (2007).
4
EXPERIMENTAL RESULTS
SWRC was measured with both methods on 29 soil samples.
Three samples belonged to the group of clean sands with less
than 5% fines (0.063 <mm), marked by SP-SW symbol, six
samples contained 5-12% fines (SP-SM), seven samples were
silty sands (SM), eight of them were clays (CH or CL) and five
samples were mixed soils with fines content between 40 and
70% (SC/CH). The last mentioned samples were undisturbed,
all other were artificially prepared in the laboratory.
Results of some grain size distributions are presented in
Figure 7 and the SWRC measurements of these samples are
presented in Figure 8. Initial conditions in HYPROP device of
specimens shown in Figure 8 are presented in Table 1.
Fig 7. Grain size distributions of samples with the SWRC, presented on
Figure 8.
Table 1. Initial conditions in HYPROP device of specimens shown in
igures 7 and 8.
F
classification
w
(%)
ρ
d
(t/m
3
)
e
Sr
(%)
SW-SP
15.5
1.80
0.528
81
SM
15.3
1.91
0.440
96
SC-CH
30.6
1.47
0.876
96
CH
91.0
0.740
2.80
92
At some samples double porosity was observed when
measurements with both methods were put together (Figure 9).
The first desorption could be correlated to soil structure or
capillary drying and the second is due to drying of fine particles.
This behaviour could be natural behaviour or it is inherent due
to laboratory compaction.
5
RESULTS AND DISCUSION
From Figure 8 it can be observed that both measurements
correlate well. It can be also observed that HYPROP device
measurements are sufficient only for sands with relatively small
amount of silty fines (< 20%). In case of mixed soils, where the
behaviour is defined by fines or in case of silts and clays
HYPROP device measurements are not sufficient and in this
case potentiometer WP4-T should be used as well.
Figure 8. Suction measurements with WP4-T and HYPROP on clean
sand, silty sand, mixed soil and fat clay (from the top to the bottom).
Add. point – addition point obtained from AEV of ceramic caps.
