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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206 CHAPTER 11. SUMMARY AND OUTLOOK<br />
study <strong>an</strong>d used to perform a series <strong>of</strong> imbibition <strong>an</strong>d drainage tests on Hostun s<strong>an</strong>d. The<br />
hydraulic behavior <strong>of</strong> unsaturated Hostun s<strong>an</strong>d was examined in these cells. In the following<br />
adv<strong>an</strong>tages <strong>an</strong>d disadv<strong>an</strong>tages <strong>of</strong> the cells are summarized that were found when performing<br />
experiments on unsaturated s<strong>an</strong>d.<br />
The following adv<strong>an</strong>tages (+) <strong>an</strong>d disadv<strong>an</strong>tages (-) were found when using the Modified<br />
Pressure Plate Apparatus :<br />
+ Only a small specimen needs to be prepared. The distribution <strong>of</strong> void ratio <strong>an</strong>d suction<br />
along the height <strong>of</strong> the specimen c<strong>an</strong> be assumed to be homogeneous.<br />
+ The application <strong>of</strong> small suction values along with small suction steps enables a pre-<br />
cise estimation <strong>of</strong> the shape <strong>of</strong> the soil-water characteristic curve <strong>an</strong>d the parameters<br />
near the air-entry value, residual suction, residual volumetric water content <strong>an</strong>d water-<br />
entry value. This is <strong>an</strong> import<strong>an</strong>t requirement when using the best-fit procedure on <strong>an</strong><br />
equation.<br />
+ The drainage curve, imbibition curve as well as sc<strong>an</strong>ning drainage <strong>an</strong>d imbibition curves<br />
c<strong>an</strong> be measured. Predefined suction values c<strong>an</strong> be applied.<br />
+ The application <strong>of</strong> vertical net stress enables the investigation <strong>of</strong> mech<strong>an</strong>ical loading on<br />
<strong>an</strong> unsaturated soil.<br />
+ Measurements <strong>of</strong> ch<strong>an</strong>ges in volume during drainage <strong>an</strong>d imbibition processes c<strong>an</strong> be<br />
carried out.<br />
+ The apparatus is relatively inexpensive, small <strong>an</strong>d user-friendly.<br />
+ The 1 bar ceramic disk c<strong>an</strong> be replaced with a 5 bar ceramic disk to investigate silty<br />
soils or conventional disk made <strong>of</strong> porous stone.<br />
- Only steady-state tests c<strong>an</strong> be performed.<br />
- The testing procedure is time consuming.<br />
- A perm<strong>an</strong>ent observation <strong>of</strong> water outflow <strong>an</strong>d inflow is necessary in order to find equi-<br />
librium conditions.<br />
Following adv<strong>an</strong>tages <strong>an</strong>d disadv<strong>an</strong>tages were found when using the S<strong>an</strong>d Column Testing<br />
Device I :<br />
+ Tr<strong>an</strong>sient state tests as well as steady state tests c<strong>an</strong> be performed under various flow<br />
rates. The influence <strong>of</strong> flow rate on the hydraulic behavior <strong>of</strong> unsaturated s<strong>an</strong>d c<strong>an</strong> be<br />
determined using the attached pump.<br />
+ The drainage curve, imbibition curve as well as sc<strong>an</strong>ning drainage <strong>an</strong>d imbibition curves<br />
c<strong>an</strong> be measured.
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