Hydro-Mechanical Properties of an Unsaturated Frictional Material
Hydro-Mechanical Properties of an Unsaturated Frictional Material
Hydro-Mechanical Properties of an Unsaturated Frictional Material
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20 CHAPTER 2. STATE OF THE ART<br />
Volumetric water content (%)<br />
60<br />
50<br />
40<br />
30<br />
20<br />
10<br />
0<br />
drainage curve Main drainage curve Initial<br />
Main imbibition curve Sc<strong>an</strong>ning drainage curve<br />
0.1 1 10<br />
Suction (kPa)<br />
100<br />
Sc<strong>an</strong>ning imbibition curve<br />
Figure 2.9: Soil-water characteristic curve showing the initial drainage curve, main imbibition<br />
curve, main drainage curve <strong>an</strong>d sc<strong>an</strong>ning curves<br />
closed pores for most soils it is not possible to achieve fully saturated state by imbibition after<br />
drainage. The following drainage <strong>of</strong> the soil specimen is called main drainage curve. Whereas<br />
the initial drainage curve is irreversible, the main loop consisting <strong>of</strong> both the main drainage<br />
curve <strong>an</strong>d main imbibition curve c<strong>an</strong> occur in numerous cycles. Drainage sc<strong>an</strong>ning curves as<br />
well as imbibition sc<strong>an</strong>ning curves are located within the main soil-water characteristic loop.<br />
The names commonly used for the several drainage <strong>an</strong>d imbibition br<strong>an</strong>ches are summarized<br />
in the following:<br />
- Initial drainage curve (irreversible curve)<br />
- Main drainage curve <strong>an</strong>d main imbibition curve (reversible curves)<br />
- Sc<strong>an</strong>ning drainage curve <strong>an</strong>d sc<strong>an</strong>ning imbibition curve (infinite number <strong>of</strong> sc<strong>an</strong>ning<br />
curves available between main drainage <strong>an</strong>d imbibition curve)<br />
The phenomenon <strong>of</strong> hysteresis c<strong>an</strong> be found in several natural sciences such as magnetism<br />
<strong>an</strong>d in chemistry. A independent domain theory for modeling hysteresis as physical phe-<br />
nomenon in soil science was presented by Everett & Whitton (1952), Everett & Smith (1954).<br />
The phenomenon <strong>of</strong> hysteresis has been gained from experimental <strong>an</strong>d theoretical experi-<br />
ences (Haines 1930, Topp 1969, Poulovassilis 1970, Pavlakis & Barden 1972, Mualem 1984b,<br />
Nimmo 1992, Iwata et al. 1995, Pham et al. 2003) <strong>an</strong>d there is broad agreement in the re-<br />
search literature regarding the relev<strong>an</strong>ce <strong>an</strong>d phenomenological background <strong>of</strong> hysteresis in<br />
the soil-water characteristic curve. The phenomenon <strong>of</strong> hysteresis was first detected <strong>an</strong>d re-<br />
ported by Haines (1930) <strong>an</strong>d is attributed to several factors as the rain drop effect (Bear
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