19 Mud Shrinkage and Cracking Phenomenon Experimental …
389
Images were taken at intervals of 2 min during the test. The dimensions of the
images for analysis are 2452-2056 pixels and the analysis with Vic-2D is done with
a subset of 21 pixels and a step of 7 pixels. Calibration tests gave an accuracy of
ε/ε of about 5% in both x-axis and y-axis, and an accuracy of 7% in the vertical
direction (z-axis) with Vic-3D.
19.3.3 Shrinkage Development in a Square Form Sample
of Kaolin K13
As mentioned previously, the shrinkage is represented by the volumetric strains
related to the drying process and occurs independently of external imposed stress
tensor. Micro-macro-analyses of clay shrinkage during desiccation performed by
Wei et al. (2013) showed that, in most cases, the strains in the three directions can
be considered as isotropic when the soil microstructure organization is isotropic.
However, the anisotropy of strains in the three directions during shrinkage remains
an open question in the community and is still under discussion (Bronswijk 1990;
Cornelis et al. 2006; Tang et al. 2011; Péron et al. 2009; Auvray et al. 2014). The
geometric boundary conditions basically seem to be an important factor that has
a large impact on the anisotropy strains development (Bronswijk 1990; Rijniersce
1983; Wei et al. 2016).
Let us consider a square sample of kaolin K13 (Fig. 19.4b), set up initially as
slurry fully saturated clay at 1.2 w L of water content, as explained in the Materials
and Methods section. The plane smooth support in contact with the clay slurry was
lubricated by means of a fine grease layer so that the shrinkage can freely develop.
The RH-controlled chamber imposes RH = 5.8% and the temperature is maintained
at 20 °C.
Hence, the volumetric strain due to the shrinkage is:
ε v = ε xx + ε yy + ε zz
(19.5)
If one considers isotropic shrinkage, the shrinkage tensor can be expressed as:
ε
sh
i j =
ε ii
3
δ i j = ε
sh
δ i j
(19.6)
And, in terms of void ratio:
ε
sh
=
1
3
e
1 + e 0
(19.7)
The 2D map presented Fig. 19.7 shows the principal major strain field deduced
from Vic-3D program at the end of drying. Compression is obtained in every part of
the sample with negative value of ε 1 ranging from −6.3 to −3.7%. The white arrows
389
Images were taken at intervals of 2 min during the test. The dimensions of the
images for analysis are 2452-2056 pixels and the analysis with Vic-2D is done with
a subset of 21 pixels and a step of 7 pixels. Calibration tests gave an accuracy of
ε/ε of about 5% in both x-axis and y-axis, and an accuracy of 7% in the vertical
direction (z-axis) with Vic-3D.
19.3.3 Shrinkage Development in a Square Form Sample
of Kaolin K13
As mentioned previously, the shrinkage is represented by the volumetric strains
related to the drying process and occurs independently of external imposed stress
tensor. Micro-macro-analyses of clay shrinkage during desiccation performed by
Wei et al. (2013) showed that, in most cases, the strains in the three directions can
be considered as isotropic when the soil microstructure organization is isotropic.
However, the anisotropy of strains in the three directions during shrinkage remains
an open question in the community and is still under discussion (Bronswijk 1990;
Cornelis et al. 2006; Tang et al. 2011; Péron et al. 2009; Auvray et al. 2014). The
geometric boundary conditions basically seem to be an important factor that has
a large impact on the anisotropy strains development (Bronswijk 1990; Rijniersce
1983; Wei et al. 2016).
Let us consider a square sample of kaolin K13 (Fig. 19.4b), set up initially as
slurry fully saturated clay at 1.2 w L of water content, as explained in the Materials
and Methods section. The plane smooth support in contact with the clay slurry was
lubricated by means of a fine grease layer so that the shrinkage can freely develop.
The RH-controlled chamber imposes RH = 5.8% and the temperature is maintained
at 20 °C.
Hence, the volumetric strain due to the shrinkage is:
ε v = ε xx + ε yy + ε zz
(19.5)
If one considers isotropic shrinkage, the shrinkage tensor can be expressed as:
ε
sh
i j =
ε ii
3
δ i j = ε
sh
δ i j
(19.6)
And, in terms of void ratio:
ε
sh
=
1
3
e
1 + e 0
(19.7)
The 2D map presented Fig. 19.7 shows the principal major strain field deduced
from Vic-3D program at the end of drying. Compression is obtained in every part of
the sample with negative value of ε 1 ranging from −6.3 to −3.7%. The white arrows