Geoscience Reference
In-Depth Information
Table 5.2 Calculated geotechnical parameters of two major landslide locations
Sl.No.
Parameters
Lower paglajhora
Tindharia
Major principal stress (kg/cm
2
)
1
1.83
2.553
Minor principal stress (kg/cm
2
)
2
0.76
0.92
Normal stress (kg/cm
2
)
3
1.10
1.4044
4
Angle of rupture (Degree)
35
°
30
′
33
°
5
Angle of internal friction (Degree)
21
°
24
°
Cohesion (kg/cm
2
)
6
0.06
0.06
Shear strength (kg/cm
2
)
7
0.5
0.73
The derived geo-technical parameters of two major landslide locations show
more or less identical results (Table
5.2
). The thickness of the soil and that of the
saturated soil during monsoon are measured to be 4.5 m (Tindharia T.E.) and
7.25 m (Lower Paglajhora). The wet soil buck density is measured to be 1.96 g/cc
and density of water is 1.07 g/cc. The angle of internal friction varies from 21
°
to
°
°
26
.
In the present study the angle of repose in sun dry condition for the concerned
material varies from 21
with an average of 24
. The basic requirement for the short term stability of
the slope at marginal escarpment of Tindharia and Lower Paglajhora are to maintain
the slope angle to be nearer or less than 21
26
°
-
(Table
5.3
). A steep slope will decline
by slope failure to an angle of repose slope to attain short term stability. This
concept leads to the concept of limiting or Threshold slope angle. It is clearly
observed from the Fig.
5.3
that middle section, extreme lower most part, Sep-
oydhura and some northern marginal parts are registering the slope angle of less
than 24
°
. Large parts of Tindharia, Gayabari, 14 Miles Bustee, Lower Paglajhora
and Shiviter are facing the slope angle of more than 24
°
and also are considered as
the most vulnerable part of the Shivkhola Watershed. Hill Cart Road is passing
through the escarpment slope which is greater than threshold slope (55
°
) and
also exhibiting as very high landslide prone section of the watershed. Analysis also
reveals that more than 60 % area of the Shivkhola watershed experiences above
threshold slope angle of 24
67
°
-
(Figs.
5.3
and
5.4
). In the Shivkhola Watershed high to
very high landslide hazard risk is being found at the place with slope angle between
24
°
. Low to moderate level of risk is observed in the area pertaining to the
slope angle of less than 24
°
and 40
°
. It could be demonstrated that 50 % area of the
Shivkhola basin is dominated by the high intensity of landslide with a slope more
than 24
°
°
.
Table 5.3 Threshold slope angle
Methods
Melnikov and
Chensokov (
1969
)
Borga et al.
(
1998
)
Carson (
1977a
,
b
,
c
)
Threshold
slope angle
θ
=21
26
°
θ
=21
26
°
ʱ
(Considering pore
water pressure)
=9
°
51
′
-
-
Search WWH ::
Custom Search