Hydro-Mechanical Properties of an Unsaturated Frictional Material
Hydro-Mechanical Properties of an Unsaturated Frictional Material
Hydro-Mechanical Properties of an Unsaturated Frictional Material
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7.4. UNSATURATED HYDRAULIC CONDUCTIVITY 159<br />
one for the loose specimen. When saturated condition is reached, the unsaturated hydraulic<br />
conductivity for the loose specimen becomes larger.<br />
Exemplary main drainage <strong>an</strong>d imbibition curves derived from steady state tests in modified<br />
pressure plate apparatus for unsaturated hydraulic conductivity are plotted versus volumetric<br />
water content k(θ) in Fig. 7.17. Even at saturated conditions (S=1, S=0) the hydraulic con-<br />
ductivity is equal, the results show slight hysteresis between the drainage <strong>an</strong>d the imbibition<br />
curve. This could be due to the fact, that during drainage curve water is different distributed<br />
in the pores th<strong>an</strong> during imbibition curve. Differences may also occur from the best fitted<br />
soil-water characteristic curve <strong>an</strong>d the applied statistical model (see also different shape <strong>of</strong><br />
unsaturated hydraulic conductivity functions derived using several statistical model given in<br />
Fig.7.14).<br />
The results <strong>of</strong> unsaturated hydraulic conductivity function for both loose <strong>an</strong>d dense spec-<br />
imens achieved from modified pressure plate apparatus (steady state test) <strong>an</strong>d also s<strong>an</strong>d<br />
column tests I (tr<strong>an</strong>sient state test) show signific<strong>an</strong>t hysteresis behavior during drainage <strong>an</strong>d<br />
imbibition process. The derived unsaturated hydraulic conductivity functions from s<strong>an</strong>d col-<br />
umn tests I (tr<strong>an</strong>sient state tests) for the drainage procedure are in good agreement with the<br />
results derived from the modified pressure plate apparatus (steady state test). As expected<br />
the unsaturated hydraulic conductivity functions for drainage path from both steady state<br />
<strong>an</strong>d tr<strong>an</strong>sient state test results <strong>an</strong>d the unsaturated hydraulic conductivity functions for imbi-<br />
bition path from steady state tests enclose the imbibition sc<strong>an</strong>ning curves from the tr<strong>an</strong>sient<br />
Unsat. hydr. conductivity (10-4m/s)<br />
3.0<br />
2.5<br />
2.0<br />
1.5<br />
1.0<br />
0.5<br />
0.0<br />
Modified pressure plate apparatus<br />
Loose specimen - drainage<br />
Loose specimen - imbibition<br />
Dense specimen - drainage<br />
Dense specimen - imbibition<br />
0 10 20 30 40 50<br />
Volumetric water content (%)<br />
Figure 7.17: <strong>Unsaturated</strong> hydraulic conductivity versus volumetric water content resulting<br />
from modified pressure plate apparatus (loose <strong>an</strong>d dense specimen, steady state test)
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