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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86 CHAPTER 4. EXPERIMENTAL SETUPS<br />
the middle part <strong>an</strong>d the top part are screwed by 8 bolts. A frame attached with a dial gauge<br />
enables the measurement <strong>of</strong> volume ch<strong>an</strong>ges during the loading paths.<br />
4.6 Equipment used<br />
Equipment used in this study are tensiometer sensors, TDR sensors <strong>an</strong>d a pump. The equip-<br />
ment is introduced in detail <strong>an</strong>d accuracy <strong>of</strong> the sensors is given.<br />
4.6.1 Tensiometer Sensors<br />
The type <strong>of</strong> tensiometer used in the present study is shown in Fig. 4.12 <strong>an</strong>d the corresponding<br />
calibration functions are given in Fig. 4.13. The tensiometer is a Miniature Pressure Tr<strong>an</strong>s-<br />
ducer Tensiometer (UMS-UmweltUmwelt<strong>an</strong>alytische Mess-Systeme). Typical applications for<br />
this type <strong>of</strong> tensiometer are:<br />
- Determination <strong>of</strong> soil-water characteristic curve <strong>of</strong> a soil<br />
- Determination <strong>of</strong> movement <strong>of</strong> water in the soil<br />
- Punctual measurement <strong>of</strong> pore-water pressure in the soil<br />
- Measurement <strong>of</strong> pore-water pressure <strong>of</strong> the soil in the laboratory<br />
- Measurement <strong>of</strong> pore-water pressure <strong>of</strong> the soil in the field<br />
As shown in Fig. 4.12 the tensiometer consists <strong>of</strong> a body <strong>an</strong>d a tensiometer cup including a<br />
ceramic cup <strong>an</strong>d a water filled shaft. The tensiomter has <strong>an</strong> overall length <strong>of</strong> 81 mm <strong>an</strong>d the<br />
body is 20 mm wide. The body consists <strong>of</strong> the pressure tr<strong>an</strong>sducer, the acrylic plastic body<br />
<strong>an</strong>d the lead.<br />
Based on the piezoresistive effect <strong>of</strong> the silicon semiconductor the sensor measures the<br />
ch<strong>an</strong>ge <strong>of</strong> the specific electric resist<strong>an</strong>ce due to deformations. These deformations are caused<br />
on the sensitive silicon chip by ch<strong>an</strong>ges in pore-water pressure. By using a Wheatstone Bridge<br />
the ch<strong>an</strong>ge <strong>of</strong> the specific electrical resist<strong>an</strong>ce is processed to a signal, which corresponds to<br />
Figure 4.12: Tensiometer sensor<br />
Tensiometer<br />
mm 50 mm 5 mm Cable ShaftCeramic cup Body<br />
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