Geoscience Reference
In-Depth Information
sandy soil, loam soil, silt loam, and clay soil are 1.6, 1.4, 1.3 and 1.1 gm/cm
3
.On
the other hand, the weight per unit volume of the solid portion of the soil is called as
particle density. The particle density is the true density of soil. The particle density
of normal soils is 2.65 gm/cm
3
. The particle density of coarse sand,
fine sand, silt
and clay are 2.655, 2.659, 2.798 and 2.837 gm/cm
3
respectively. The particle
density of the soil increases with decreasing the size of particles. The porosity can
be calculated by using the following method.
bulk density
particle density
¼
ð
2
:
4
Þ
%
solid space
100
of pore space
¼
100
%
%
of solid space
ð
2
:
5
Þ
%
In the present work, the total porosity in the soil has been derived using the
method applied by Brasher (
1966
).
ðÞ¼
ð
Þ
ð
2
:
6
Þ
Total porosity
particle density-bulk density
particle density
Loose, porous soils have lower bulk densities and greater porosities than tightly
packed soils. Porosity varies depending on particle size and aggregation. It is
greater in clayey and organic soils than in sandy soils. A large number of small
particles in a volume of soil produce a large number of soil pores. Compaction
decreases porosity as bulk density increases. So, there exists a inverse relationship
between bulk density and porosity. If compaction increases bulk density from 1.3 to
1.5 g/cm
3
, porosity decreases from 50 to 43 %. Pores of all sizes and shapes
combine to make up the total porosity of a soil. Porosity, however, does not tell us
anything about the size of pores (
http://www.agriinfo.in
)
(Table
2.12
).
The collection and testing of soil samples from different locations and their
laboratory results shows that at 14 Miles Basti water holding capacity and volume
Table 2.12 Friction angle (
φ
) and landslide potentiality index (LPIV)
Classes
Number of
pixels (F
1
)
Number of landslide
affected pixels (F
2
)
Landslide potentiality index
(LPI) = (F
2
/F
1
×
100)
<18.00
3,500
626
17.88
18.00
-
19.486
3,547
523
14.74
19.486
-
20.971
3,266
417
12.77
20.971
22.456
3,864
413
10.69
-
22.456
23.940
2,786
329
10.81
-
23.940
-
25.425
3,545
311
8.77
25.425
26.910
2,435
201
8.25
-
26.910
28.395
3,597
211
5.86
-
28.395
-
29.880
3,248
202
6.21
29.880
32.848
3,343
190
5.68
-
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