Hydro-Mechanical Properties of an Unsaturated Frictional Material

4.3. SAND COLUMN I 79
by Vanapalli et al. (2008). There in detail the limitations of these techniques with respect to
air diffusion, water volume change and evaporation are discussed.
4.3 Sand Column I
The sand column device I (Fig. 4.3) enables to determine drainage and imbibition soil-water
characteristic curves of the tested material. Steady state flow tests and transient state flow
tests can be performed on the specimen.
A schematic sketch of the experimental setup of the sand column testing device I is
shown in Fig. 4.4. The setup consists of a Trase System including Multiplexer and 5 TDR
sensors (Time Domain Reflectometry), 5 Tensiometers connected to a datalogger, computers
for computing and saving experimental results, an electronic pump and a cylinder and the
column. In detail the column device is given in Fig. 4.5. Totally the column is 780 mm high
and 305 mm in diameter. The soil specimen has a height of maximal 630 mm. The bottom
part of the column consists of a water reservoir made of steel that is sufficiently rigid. It
consists of a 10 mm thick base plate, a cast iron pipe 100 mm high and 323 mm in diameter
and a muff. The base plate, the pipe and the muff are welded. A connection in the pipe
enables to inject or withdraw water to the reservoir. The top part consists of a PVC tube
that has also a muff on the bottom. The water reservoir and the PVC tube are departed
by a perforated plexiglas plate with 10 mm thickness. The plexiglas plate has 82 boreholes
3 mm in diameter that are uniformly distributed over the entire plate. This enables a uniform
inflow and outflow of water from and into the specimen. The water reservoir, the plexiglas
plate and the PVC tube are connected by 6 bolts to the muff. Between the PVC tube and
Trase Multiplexer
TDR and tensiometer
Pump
Column
Water reservior
Figure 4.3: Column testing device I
sensors