geology in bridge construction

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GEOLOGY IN BRIDGE CONSTRUCTION.:

GEOLOGY IN BRIDGE CONSTRUCTION. .

CONTENT:

CONTENT Definition. Geological considerations. Geological characters- -Depth to bed rock . -Nature of bed rock . -Structural disposition. Data required. Factors affecting bridge sites. Advantages. Conclusion .

Definition:

Definition A structure built over a river, a dry valley, low or any depressed part of the land to provide a link between two opposite sides.

Geological considerations :

Geological considerations Whenever the bridge is constructed across any natural depression, the sound rock should not be at a large depth below the walls and floor of such a depression . Foundation and abutment rocks should be strong enough to bear the load of the bridge structure as well as the vehicular traffic above it. If the bridge lies across the river channel, the erosive action of the running water should not be so conspicuous as to cause the wear and tear of the piers or foundation. Foundation rock should be free from shear zones, fissures and joints.

Geological considerations :

Geological considerations Most rocks of igneous origin are suitable for bridge foundation. Amongst sedimentary rocks, compact beds of sandstone, conglomerate and breccia are suitable for taking the load of the bridge structure and traffic.

Geological Characters:

Geological Characters In any major bridge construction project, the designer is keen to place the Bridge Abutments and piers on as sound strong and stable rock foundation below as possible. -Depth to bed rock . -Nature of bed rock . -Structural disposition.

Depth to bed rock .:

Depth to bed rock . Unconsolidated natural deposits of sand gravels and boulders. Such loose materials are not safe for foundation. Reasons – 1.piers placed directly on them would be unstable. 2. the cover material is liable to be removed due scouring by river water.

Nature of bed rock:

Nature of bed rock Bed rock – strong. Most igneous, massive sedimentary and metamorphic rocks are quite strong, stable and durable.

Structural Disposition:

Structural Disposition Horizontal altitude and uniform massive structure offer inherent resistant against failure.

Data Required :

Data Required The preliminary Foundation Geology Report, including test hole locations, geological description of soils and rock, SPT data, 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.

Factors affecting bridge sites:

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.

ADVANTAGES :

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.

Conclusion :

Conclusion From all the point of view geology in bridge construction have more importance. As it is the necessary part of the construction.

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