Environmental Engineering Reference
In-Depth Information
Ta b l e 5 . 7
Resonant frequencies (
f
res
) associated to the pre-established water content level
(θ ) corresponding to the apparent permittivity values (ε
app
), for each type of sand (#1, #2,
#3) [12]
sand #1 (granulometry
≤
1
mm)
θ
(
cm
3
/
cm
3
MUT
)
ε
app
f
res
(GHz)
s1
0.000
2.75
1.958
s2
0.031
3.22
1.955
s3
0.062
3.94
1.949
s4
0.093
4.72
1.944
s5
0.124
5.39
1.909
s6
0.156
6.55
1.885
sand #2 (granulometry
2
÷
4
mm)
θ
(
cm
3
/
cm
3
MUT
)
ε
app
f
res
(GHz)
s1
0.000
2.80
1.965
s2
0.034
3.13
1.958
s3
0.067
3.54
1.949
s4
0.101
4.85
1.941
s5
0.137
6.29
1.906
s6
0.171
7.30
1.906
sand #3 (granulometry 2 mm)
θ
(
cm
3
/
cm
3
MUT
)
ε
app
f
res
(GHz)
s1
0.000
3.91
1.949
s2
0.038
4.13
1.947
s3
0.076
4.66
1.930
s4
0.114
5.69
1.912
s5
0.153
8.33
1.891
s6
0.191
10.14
1.866
Results reported herein show that the proposed method provides good results for
volumetric moisture content lower than 20% (e.g., in the considered cases
app
=
10). Fig. 5.18 shows the final calibration curves relating the resonant frequency
of each moistened sample to the corresponding moisture level. The curve of sand
#3 is evidently more linear than the curves referred to sand #1 and sand #2: this
is attributed to the different granulometric and porosimetric characteristics of the
considered sands. In fact, the grains of sand #3 have rather uniform dimensions
(2 mm). Conversely, the grains of sand #1 and of sand #2 have different dimensions
(in the ranges reported in Table 5.7). For this reason, for lower moisture levels sand
ε
Search WWH ::
Custom Search