Hydro-Mechanical Properties of an Unsaturated Frictional Material

88 CHAPTER 4. EXPERIMENTAL SETUPS
sensors are connected to a Multiplexer and then to a Trase System. The Multiplexer allows
measurements to be made automatically of several TDR sensors. A switching board with 16
channels for connecting up to 16 TDR sensors was used. Measurements, computations and
analysis of the data is done by the Trase system. A computer connected to the Trase system
is used to display the results.
The TDR probe measures the dielectric constant, which is related to the volumetric water
content. Therefore the speed, an electromagnetic pulse of energy needs to travel down a par-
Pore-water pressure (kPa)
Pore-water pressure (kPa)
Pore-water pressure (kPa)
0
-2
-4
-6
-8
-10
-12
0
-2
-4
-6
-8
-10
-12
0
-2
-4
-6
-8
-10
-12
Voltage (mV)
0 20 40 60 80 100
Voltage (mV)
Pore-water pressure (kPa)
Pore-water pressure (kPa)
0 20 40 60 80 100
Experimental results
Calibration function
Error band
Tensiometer T1
f(x)= -0.1055x+0.2522
Voltage (mV)
0 20 40 60 80 100
Tensiometer T3
f(x)= -0.1099x+0.3767
Tensiometer T5
f(x)= -0.1069x+0.1383
0
-2
-4
-6
-8
-10
-12
0
-2
-4
-6
-8
-10
-12
Voltage (mV)
0 20 40 60 80 100
Tensiometer T2
f(x)= -0.1078x+0.5243
Voltage (mV)
Figure 4.13: Calibration of the tensiometers
0 20 40 60 80 100
Tensiometer T4
f(x)= -0.1147x+0.7877