Hydro-Mechanical Properties of an Unsaturated Frictional Material

2.3. HYDRAULIC FUNCTIONS 27
referenced studies date back almost 20 to 30 years. Precision of measurements related to
water content and suction must be carefully considered when deriving the final conclusions.
2.3.3 Methods for Determination of Hydraulic Functions
As already mentioned the important hydraulic functions in unsaturated soil mechanics are
both the soil-water characteristic curve θ(ψ) and the unsaturated hydraulic conductivity func-
tion k(ψ). Several methods are available to measure these two constitutive functions, e.g.:
- Determination of θ(ψ) from experiments conventionally performed in tempe cells or
pressure cells and deriving k(ψ) by combining θ(ψ) with different model assumptions.
- Determination of θ(ψ) and k(ψ) independently from experiments.
- Determination of one-step flow, multistep flow or continuous flow experiments and es-
timating both functions simultaneously using inverse modeling (see Section 2.6).
A literature review on flow experiments, that are used for predicting hydraulic functions of
unsaturated soils is given in Tab. 2.1. The table gives an extensive overview of flow exper-
iments carried out by several researchers. It gives the testing devices and the equipment
used (PT-Pressure transducer, T-Tensiometer, GRA-Gamma Ray Attenuation, TDR-Time
Domain Reflectometry sensor), the method applied (OM-One step Method, MM-Multistep
Method), the loading applied to the specimen (D-Drainage, I-Imbibition) and the material,
that was used for the investigation. Only few researches used tensiometer and TDR sensor
measurements in their investigation to study unsaturated flow.