slope stability gis by fardous rababah

8/16/2019 Slope Stability Gis by fardous rababah

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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



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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#



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* ma%imum sloping ground is the best parameter tocharacterize the slope.



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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 .

slope stability gis by fardous rababah

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