International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004
Soils containing fines (silt and clay) display the properties of
plasticity and cohesiveness where a lump of soil can have its
shape changed or remoulded with out the soil changing in
volume or breaking up. This property depends on the amount
and mineralogy of the fines and the amount of water present, or
moisture content. As the moisture content increases a clayey or
silty soil will become softer and stickier until it can not retain
its shape when it is described as being in a liquid state. If the
moisture content is increased further than there is less and less
interaction. between the soil particles and slurry, and a
suspension is formed. Typical moisture contents of soil are
shown in Table 1.
Soil type Moisture content
moist sand 5-15
‘wet’ sand 15-25
moist silt 10-20
*wet' silt 20-30
NC clay low plasticity 20-40
NC clay high plasticity 50-90
OC clay low plasticity 10-20
OC clay high plasticity 20-40
NC: Normally consolidated, OC: Overconsolidated
Table 1. Typical moisture contents of soil
For clays and silts the usual classification is derived from their
engineering properties under varying conditions of moisture.
The Atterberg limits are an empirically developed but widely
used procedure for establishing and describing the consistency
of cohesive soil. The Atterberg limits are of a somewhat
empirical nature, but frequently these limits to provide useful
information regarding soil strength, behavior, stability, type,
and state of consolidation, or classification of a clay as organic
or inorganic. Consistency limits of soil have been determined in
the clays occurring as a result of weathering Upper Cretaceous
aged andesitic rock and are given in Table 2. These samples
have been defined normally consolidated high plasticity soil.
Rock Consis. Result
Type limits
Completely Wi (96) 69
weathered
2
andesite We (%) 42
Ip (96) 27
Table 2. Consistency limits test results
The general definition for specific gravity is the ratio between
the unit weights of a substance and the unit weights of pure
water at 4 °C. The value commonly used for the specific gravity
of soil particles is 2.7 gr/cm’ (Cernica, 1995). Specific gravity
value of the clay has been determined as 2.68 gr/em”.
3.2 Photogrammetric Evaluation of Landslide
In this contribution, stereo photogrammetric evaluation was
performed by using aerial photographs of Ardesen region
(Ortaalan Village) in Rize. Digital Photogrammetric
Workstation Zeiss SSK by Z/1 Imaging was used for
photogrammetric evaluation. After pre-processing, the different
dated images scanned with 21 micron precision and covered the
selected area was transferred to the system. To establish the
relationship between object space and image space, the ground
control points were selected in model area to be able to do all
measurements in Natiaonal Coordinate System. These points
coordinates were measured using GPS (Global Position System)
technology. Then, inner, relative and absolute orientations were
respectively performed (Figure 4). At the result of the absolute
orientation, the accuracy was obtained 45 cm in planimetry (x,
y), 50 cm in height (z).
3 M
4 A^ caesi e p M p etc i
Figure 4. The aerial image of study area after landslide
The color aerial images were taken between 1996 and 2002 in
scale of 1/16000 and covered the landslide area were used. The
images were taken in 1996 before the landslide and the
landslide was occurred in 2001. The vectorel maps were
produced from determining the images using the existing
buildings, roads and morphology before and after landslides.
The morphological changes were investigated by taken the two
different direction profiles covered the landslide area (Figure
5). In addition, the goemetrical boundries of the area affected
by landslide was determined.
3. RESULT AND DISCUSSION
In this study, it is worked out that the geometrical changes in
the landslide area are determined with using the
photogrammetric techniques. It is seen that the desingnation
landslide area with photogrammetric techniques can be
determined easily, true and effectively according to classical
methods. Espacially, the geomorphological characteristics of
landslide area were obtained from the images taken before
landslide. The quantity of the surfacial changes in the landslide
area were investigated by taken the two different direction
profiles (Figure 6, 7). Landslide aera was calculated as 3.2
hectar. Main scarp, swelling aera and toe area were easily
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