Hydro-Mechanical Properties of an Unsaturated Frictional Material

114 CHAPTER 5. MATERIAL USED AND EXPERIMENTAL PROGRAM
Table 5.9: Experimental programm for collapse tests
initial suction ψ0 Net stress σ
5.5 Summary
5.0 kPa 2 5 S=1 7 10 12 20 25 50 100
5.0 kPa 2 5 7 10 12 S=1 20 25 50 100
5.0 kPa 2 5 7 10 12 20 25 S=1 50 100
S = const Net stress σ
S=1 100 50 25 20 15 12 7 5 2
S=1 100 50 25 20 15 12 7 5 2
S=1 100 50 25 20 15 12 7 5 2
In this chapter the investigated material is classified. It was found, that homogeneous speci-
men were produced when pluviating the testing material directly into the oedometer ring of
the modified pressure plate apparatus. Investigations using computer tomography as well as
electron microscopy supported this. Saturated specimen, the initial condition for the tests
performed in column testing device I and II, are produced by pluviating sand directly into
the column filled with deaired water. Air-pluviated specimens were prepared in the modi-
fied pressure plate apparatus and in the controlled suction oedometer and saturated in an
additional step.
Overall the experimental programm consists of the investigation of the hydro-mechancial
behavior of unsaturated Hostun sand. Testing devices as the modified pressure plate appa-
ratus, the sand column testing device I and II as well as the controlled-suction oedometer
are used to determine the hydraulic functions of Hostun sand, the influence of suction on the
compression and swelling index as well as the stiffness modulus. Initial conditions (initial void
ratio, initial suction), applied loading paths (drainage, imbibition, loading, unloading with
vertical net stress) and flow conditions (steady state test, transient state test) are considered
in the experimental programm to estimate hydro-mechancial behavior of unsaturated sand
and to account for the phenomena (phenomenon of hysteresis, collapse, occluded air, dynamic
effect) associated with it.