Appendix A
drying, (
W
–
W
) and its volume,
L
w
0
s
:
(
)
(
)
25
.
0
5
.
463
2
.
627
3
.
743
0
=
−
=
−
=
s
w
w
L
W
W
θ
θ
= 0.25
w
Calculate
a
In the wet soil
V
=
V
1
w
= 0.672 Volts and substituting
gives
91
.
3
=
w
ε
Finally
(
)
(
) (
) (
)
80
.
8
0
25
.
0
70
.
1
91
.
3
0
0
1
=
−
−
=
−
−
=
θ
θ
ε
ε
w
w
a
a
= 8.80
1
Laboratory calibration for clay soils
This technique is adapted to avoid the near-impossibility of inserting the
ThetaProbe into a completely dry clay soil. It requires taking measurements
at 2 significantly different, but still damp, moisture levels.
Equipment you will need:
ThetaProbe and meter
Soil corer
Heat-resistant beaker (
≥
500ml)
Weighing balance (accurate to < 1g)
Temperature controlled oven
Notes and example
Process
Collect a wet sample of the clay soil: 25 to 30%
water content would be ideal.
This sample needs to be unchanged from its in-
situ density, to be
≥
500ml, to have the correct
dimensions to fit the beaker, and to be generally
uniform in water content.
This is most easily done with soil-corer.
Measure the volume occupied by the sample.
= 463.5
ml
L
s
Profile Probe User Manual
3.0a
Soil-specific calibration
z
37
