Hydro-Mechanical Properties of an Unsaturated Frictional Material

192 CHAPTER 9. NUMERICAL SIMULATION OF COLUMN TEST BY FEM
Saturation (-)
Saturation (-)
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Results simulation Results experiment Depth 70 mm
Saturation (-)
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Results simulation Results experiment Depth 160 mm
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Results simulation Results experiment Depth 260 mm
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Results simulation Results experiment Depth 360 mm
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Figure 9.6: Comparison of pore-water pressure measurements and simulation including hysteresis
model from Parker and Lenhard (1987) - steady state test
In general, it can be stated that a good prediction of the flow process in the transient state
test has been obtained with a conceptually simple scaling approach for hysteresis.
In a further investigation an additional soil-water characteristic curve is determined from
steady state experiment on Hostun sand specimens and consequently used for a numerical
simulation. This is a common procedure in applications involving unsaturated flow. However,
the suction-water content curve determined with this approach demonstrates absence of air
residual saturation in imbibition, in contrast to the transient state test where a strong trapping
effect is observed. The numerical simulation carried out here incorporates the Parker and
Lenhard (1987) hysteresis, however cannot predict correctly the flow process in the transient
state experiment due to the inappropriate input soil-water characteristic curve.