GEOLOGY

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geological considerations in construction of dams over uncosolidated formatios

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GEOLOGICAL CONSIDERATION IN SELECTION OF DAMS AND RESERVOIRS OVER UNCONSOLIDATED FORMATION : 

GEOLOGICAL CONSIDERATION IN SELECTION OF DAMS AND RESERVOIRS OVER UNCONSOLIDATED FORMATION FROM: -DINESH -BISHAL THAKUR - ARUN ALEXANDER

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UNCONSOLIDATED FORMATION ?

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A sediment that is loosely arranged or whose particles are not cemented together i.e. soft rocks which occurs either at the ground surface or at a depth below the surface.

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General things to be taken into account before the construction of a dam Dam site should be such that quantity of leakage through it is minimum. Dam site having the presence of highly permeable rocks reduce the water tightness of dam.

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Topography of a reservoir site should be such that it has adequate capacity without submerging excessive land and other properties . Reservoir basin should have narrow openings in the valley so that the length of the dam is less.

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DAM FOUNDATION

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The dam should be founded on sound water tight rock base and percolation below the dam should be minimum . The control of floods is an essential element in dam design and may also be a difficult problem during construction on large rivers . The local seismic risk may modify the design.

Geological Concerns: 

Geological Concerns PLANAR FEATURES Thin shear or weak planar zones Weak Joints Faults and Fault zones ZONAL FEATURES Solution Cavities Weathered Zones Buried Channels

CONSIDERATIONS: 

CONSIDERATIONS Checking the quality of rocks Excavation to a given rock quality provides a foundation with those characteristics judged adequate.

Cut off trench to prevent the seeping of water: 

Cut off trench to prevent the seeping of water A trench that is cut along the centerline of a new dam. This trench needs to extend, in depth, to an impervious material. An impervious material is any material that water cannot seep through. This material could be rock, shale or even heavy clay. After this material is reached, the trench should be filled and compacted with the heaviest clay available.

Treatment carried out conventionally: 

Treatment carried out conventionally Excavate weak portion and fill back with concrete d = 0.002 bH + 5 for H > 150 ft. d = 0.3 b + 5 for H < 150 ft. where H = height of the dam b = width of the weak zone d = depth of excavation weak zone for clay gouge d > 0.1 H

Case Of Tigra Dam : 

Case Of Tigra Dam 100 ft. high dam across river. Built in 1913-1917 on massive rock foundation. Failed in first filling. Broken dam stands downstream even today. 12 years of investigation revealed that Sandstone with horizontal seams led to uplift.

OMKARESHWAR DAM:: 

OMKARESHWAR DAM:

OMKARESHWAR DAM(MP): 

OMKARESHWAR DAM(MP) LOCATED 80 KM FROM INDORE, 40 KM DOWNSTREAM OF INDIRASAGAR 949 m LONG CONCRETE GRAVITY DAM 53 m HIGH HAS A SURFACE POWERHOUSE WITH 8 UNITS.

Case of Omkareshwar Dam: 

Case of Omkareshwar Dam Foundations having horizontally stratified formations. Block Shear tests were conducted. Analysis shows sliding failure.

Benefits And Issues In Dam Construction : 

Benefits And Issues In Dam Construction

THANK YOU: 

THANK YOU