Lesson 7 - nptel

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Seepage failures The water on the reservoir side continuously seeps through an embankment dam and its foundation to the downstream side. Unless a proper design is made to prevent excessive seepage, it may drive down fine particles along with its flow causing gaps to form within the dam body leading to its collapse. Seepage failures may be caused in the following ways: 1. Piping through dam and its foundation: This is the progressive backward erosion which may be caused through the dam or within its foundation by the water seeping from upstream to the downstream (Figure 26) Version 2 CE IIT, Kharagpur
2. Conduit leakage: This is caused due to seepage taking place by the surface of a conduit enclosed within an embankment dam (Figure 27). The seepage of water may be from the reservoir to the downstream or due to the water leaking out of the conduit through cracks that might have developed due to unequal settlement of dam or by overloading from the dam. Further, the cracking of a conduit may also be caused when the soil mass lying below it settles and the conduit is not sufficiently strong to support the soil mass lying above. 3. Sloughing of downstream face: This phenomena take place due to the dam becoming saturated either due to the presence of highly pervious layer in the body of the dam. This causes the soil mass to get softened and a slide of the downstream face takes place (Figure 28) Version 2 CE IIT, Kharagpur
Page 1 and 2: Module 4 Hydraulic Structures for F
Page 3 and 4: Instructional objectives On complet
Page 5 and 6: Version 2 CE IIT, Kharagpur
Page 7 and 8: An embankment dam is not as impervi
Page 9 and 10: Here, too it may be observed that t
Page 11 and 12: Though this is entirely satisfactor
Page 13 and 14: Another layout of the combination o
Page 15 and 16: Both the spillway section and the p
Page 17 and 18: The example of Beas Dam at Pong (Fi
Page 19 and 20: Another example is given in Figure
Page 21: spillway. Overtopping may also be c
Page 25 and 26: drops to zero, which means the soil
Page 27 and 28: Version 2 CE IIT, Kharagpur
Page 29 and 30: 1. Safety against hydraulic failure
Page 31 and 32: 2. Safety against seepage failures
Page 33 and 34: for resisting the piping action. Th
Page 35 and 36: Inclined/Vertical Filter Inclined o
Page 37 and 38: Transition Zones and Transition Fil
Page 39 and 40: Rock Toe The principal function of
Page 41 and 42: Toe Drain Toe drain is provided at
Page 43 and 44: Grout Curtain Grout Curtain in Perv
Page 45 and 46: Relief Wells Relief wells are an im
Page 47 and 48: As may be observed from Figure 48,
Page 49 and 50: Quantity of seepage flow An embankm
Page 51 and 52: The slope stability methods general
Page 53 and 54: The above critical conditions are e
Page 55 and 56: Earthquake Condition In the regions
Page 57 and 58: In some rivers, the floods may be s
Page 59 and 60: To reduce the hydrostatic pressure
Page 61 and 62: Movements Measurement of movements
Page 63 and 64: Horizontal movement gauges Cross-Ar
Page 65: Electrical Piezometers: Electrical

Lesson 7 - nptel

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