Hydro-Mechanical Properties of an Unsaturated Frictional Material

106 CHAPTER 5. MATERIAL USED AND EXPERIMENTAL PROGRAM
sensor
10 Tensiometer cm
20 TDR cm Supply for sensors cm 10 cm 17
for sensors Supply
Figure 5.9: Placement of TDR sensor and tensiometer in column testing device I
Similarly to the preparation procedure in the column testing device I specimens were
pluviated using a funnel (500 ml capacity) into the column filled with water. Whereas the
water in the column testing device I is injected from the bottom water reservoir into the cell, in
the column testing device II the water is carefully filled from the top into the cell. For both the
loose and dense specimen the mass of water required for saturated condition was poured into
the column before pluviating oven dry sand into the cell. When preparing loose specimen the
falling height of the sand was approximately 50 mm, when preparing the dense specimen the
falling height of the sand was approximately 300 mm. Every fifth centimeters the void ratio
in the column was checked using the mass of dry sand in the column. With a distance of 60
mm pairs of TDR sensor and tensiometer sensor were inserted into the specimen. Specimens
approximately 230 mm high and with a diameter of 240 mm were produced.
While the system was closed (all valves closed) an air-pressure of approximately 3.5 kPa
was applied from the top of the cell to the initially water saturated specimen. After 30 min
the valve of the water reservoir was opened and the drainage procedure started. The tests
were finished when the top tensiometer sensor reached a matric suction of 3.5 kPa.
During the whole testing procedure TDR and tensiometer sensors computed the measure-
ments every minute. The flow rate was measured and settlements were obtained continuously.
Specimen preparation and testing procedure - controlled-suction oedometer cell
As explained for the modified pressure plate apparatus the ceramic disk was saturated before
each experiment and the system below the ceramic disk was thoroughly flushed with deaired
water.
The specimen preparation in the controlled-suction oedometer cell is similar to the prepa-
ration procedure in the modified pressure plate apparatus. All specimen were prepared di-
rectly into the fixed oedometer ring 20 mm high and 50 mm in diameter. Loose and dense