slope stability gis by fardous rababah
TRANSCRIPT
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Fardous Rababah
GIS Methodology for zonication ofslope stability under
earthquakes
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Medellin,Colombia is
the study area
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Recent earthquakes inColombia have shown
the great importance of
landslide
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Geographic Information ystem!GI" in geotechnical
engineering
*)GIS(are tools for organizing, analyzing, and
presenting spatial data.
aboutgeological,geotechnical
studies,
analyses ofearthquake
groundresponse
This methodology coveredaccumulation of eistinginformation !
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GI in this study
*Different approaches have been developedworldwide in order to get reliable methodologies
for zonification of slope stability under
earthquakes.
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*This kind of approaches analyzes landslidehazard by dividing the area in a square-cell
grid,
*need of taking into account marked
relationships among the cells due to particular
slope geometry, potential failure surface and
sliding
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# a s i c
i n f o r m a t i o n
$he topographical and geologicalmaps
$he geotechnical and seismic%oni&cation of the region.
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If geotechnical %oni&cation isnot available, it is possible to
get this information based on:
-site investigations
-eld observations
-geophysical tests andlaboratory tests.
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-$he &rst one involves thegeneration of a map that
represents slope stability understatic conditions
-$he second stage of analysis considersall the factors included in 'stimation ofrepresentative earthquake force ,de&ne
di(erent rock acceleration levels.
*
GI methodology forlandslide ha%ardevaluation has two mainstage:
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$he &rst stage !under staticconditions"
eneration of digital terrain model!DT"#$
based on information of surface features and location of
rivers and creeks !topographical information#.
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*eneration of sloping ground map$
This map represents sloping ground variation in the
studied zone.
This city presents steeped
surfaceswhich reflects the great
importance of landslide
phenomena in this country
$he &rst stage !under staticconditions"
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*eneration of flow direction map
it is necessary to evaluate the flow direction, variable
that makes possible identification of individual slopes.
"The generation of theflow direction map is
based on the following
eight flow directions$
north, south, east, west,
northeast, northwest,
southeast and
southwest#
$he &rst stage !under staticconditions"
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* ma%imum sloping ground is the best parameter tocharacterize the slope.
$he &rst stage !under staticconditions"
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Geotechnical characteri%ation ofthe region
*This step involves identification of representative soilprofiles of the region
*soil profiles consist of particular sequence of layers,
where every sequence can have different thickness
distribution.
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*involve the effective
weight of materials
-the pore pressure
conditions
-the shearing strength
parameters
!cohesion andinternal friction angle#
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tability analysis under staticconditions.
*&tability analysis are based on
preparation of stability number
charts for every representative
soil profile to estimate the ratio
between critical height and real
height constitutes the
measurement of slope stability.
*This ratio is considered as a
safety factor
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$he second stage !)oni&cation of landslideunder earthquakes"
*The ratio between the site
ma%imum acceleration
and the limit acceleration
represents a safety factorof slope stability under
earthquakes.
*this city taking into accountrock acceleration of '.() g
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In conclusion:
*& methodology, allowed the identification of thegreat influence on landslide not only under static
conditions but also under earthquakes.
*&tability of every slope under earthquakes depends on
its geometry surface features, geotechnical properties
and associated local site effects.
*+onification results of landslide hazard are so useful
for government agencies to prevent disaster .