Hydro-Mechanical Properties of an Unsaturated Frictional Material

11.2. TESTING DEVICES AND EQUIPMENT 207
+ The procedure is not time consuming.
+ Volumetric water content measurements θ(t) and suctions measurements ψ(t) can be
used to directly determine hydraulic functions (suction-water content relation, unsatu-
rated hydraulic conductivity).
- Expensive equipment is required (i.e., TDR sensors, tensiometers, 2 computers for com-
puting results).
- Careful calibration of the sensors is necessary.
- Preparation of the specimen is time consuming and a large mass of material to be tested
is needed.
- The specimen must be a disturbed specimen.
Following advantages and disadvantages were found when using the Sand Column Testing
Device II :
+ Drainage transient state tests can be performed under various flow rates. The influence
of flow rate on the hydraulic behavior of unsaturated sand can be determined using the
attached air-pressure system.
+ Measurements of changes in volume can be performed.
+ The procedure is not time consuming.
+ Volumetric water content measurements θ(t) and suctions measurements ψ(t) can be
used to directly determine hydraulic functions.
- Expensive equipment is required (i.e., TDR sensors, tensiometers, 2 computers for com-
puting results).
- Careful calibration of the sensors is necessary.
- It is not useful to carry out steady state tests in the sand column testing device II, due
to the size of specimen. The testing procedure would be very time consuming.
- The specimen is a disturbed specimen.
Even it is a time consuming procedure for prediction of soil-water characteristic curve in-
cluding initial drainage, main drainage and imbibition curve as well as scanning curves the
modified pressure plate apparatus was found to be the favorite equipment. Due to possibility
of application of small suction increments the equipment enables precise determination of the
shape of the soil-water characteristic curve during drainage and imbibition. For investigation
of influence of flow condition to the shape of the soil-water characteristic curve sand column