Presentation Geo Bridge

7/28/2019 Presentation Geo Bridge

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GEOLOGICALCONSIDERATION

IN BRIDGE FOUNDATION

&CONSTRUCTION

By Ashenafi Kiros


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CONTENT:

Definition.

Geological considerations.

Geological characters- -Depth to bed rock .

-Nature of bed rock .

Structural disposition.

Data required.

Factors affecting bridge sites.

Advantages.

Conclusion .


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Definition:

A structure built over a river,

a dry valley, low or anydepressed part of the landto provide a link between

two opposite sides.


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Geological considerations

:Most rocks of igneous origin are

suitable for bridge foundation.

Amongst sedimentary rocks,

compact beds of sandstone,

conglomerate and breccia aresuitable for taking the load of the

bridge structure and traffic.


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Geological Characters:

In any major bridge construction

project, the designer is keen to placethe Bridge Abutments and piers on assound strong and stable rock

foundation below as possible. -Depthto bed rock . -Nature of bed rock . -Structural disposition.


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Depth to bed rock .:

Depth to bed rock . Unconsolidated natural

deposits of sand gravels and boulders.

Such loose materials are not safe forfoundation. Reasons

1.piers placed directly on them would be

unstable.2. the cover material is liable to be removed

due scouring by river water.


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Nature of bed rock:

Nature of bed rock should be

strong. Most igneous, massive

sedimentary and metamorphic

rocks are quite strong, stable and

durable.


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Structural Disposition:

Structural Disposition

Horizontal altitude anduniform massive structure

offer inherent resistantagainst failure.


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Data Required :

Data Required The preliminary Foundation

Geology Report, including test hole locations,

geological description of soils and rock, SPTdata, ground water table locations, temperature

data, permafrost depth, and other data as

applicable. The description of bedrock properties

when present, including planes of weakness,joints, faults, rock type, Rock Quality Designation

(RQD), etc. as they relate to the foundation

recommendations.


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ac ors a ec ng r gesites:

Factors affecting bridge sites If the bridge lies across

a river joining two mountains, the depth at which

each bridge pier meets the hard sound rock may

vary from pier to pier. This depth can only be gauged

from geological studies.


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ADVANTAGES :

The subsurface soil description, including unit

weight, relative density, moisture content, phi angle,

and lateral stiffness parameters and modeling

recommendations for each layer of soil. The

presence of permafrost, high ground water table,

and soil stability considerations. The role in socio-

economic development and defence strategies.


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Conclusion :

From all the point of view

geology in bridge constructionhave more importance. As it is

the necessary part of theconstruction.


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Thank you.

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Presentation Geo Bridge