The document outlines structural specifications related to an impervious floor, focusing on dimensions, thickness, and hydraulic calculations based on Bligh's creep theory. It includes parameters for upstream and downstream measurements, residual head conditions, and wing wall designs. Key calculations for floor length, creep length, and factors influencing uplift pressure on the floor are also detailed.

1. 3/18/2014 1
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2. 3/18/2014
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2

3. u/s pile depth
u/s floor length
Top width of fall
Bottom width of fall
Height of fall
Length of cistern
Depth of cistern
Thickness of floor
d/s floor length
Depth of intermediate and d/s pile
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4. 1.5 M
0.85 M
D = 2.25 m
5.5. m
0.3 m
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101.5
101.2
103.77

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6. Impervious floor : (Bligh
creep theory)
Total creep length –
(L) = CHs
Where Maximum seepage head = Hs
= crest level – d/s bed level
L = 2d1 + l + 2d2
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7. L = 2d1 + l + 2d2
L = total creep length,
d1 = depth of u/s cutoff , d2 = depth
of d/s cutoff , &
l or b = length of impervious floor
l =b
d1
d2
lu ld1.5 m
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8. Minimum length of d/s floor
required,
Thus the length of u/s floor
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9. `
L =
L = 13.7 (creep length)
D1
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10. Impervious floor length l or b from
equation L = 2d1 + l + 2d2
L = 2(0.5) + l + 2(0.75) = 13.7
l or b = 11.20
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11. Minimum length of d/s floor
required,
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12. l =b = 11.2 mD1 = 0.5
D2
=
0.75
2.7 1.5 m
7. 0 m
0.6
m 0.6
m
Floor length and cutoff
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13. Thickness of floor as per Bligh
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14. t = residual head at any point / G – 1
Where Residual Head = hr
hr = depth of cistern
+
creep length
upto the point





 
lengthtotalcreep
bedlevelRLofcrest
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15. Thickness of floor as per Bligh
103.77
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16. Thickness of floor as per Bligh
(a) Residual head (static head) at
the d/s toe of the crest wall
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17. Thickness of floor as per Bligh
103.77
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18. Thickness of floor as per Bligh
(b) Residual head at 3 m from the toe
of the crest wall :
Hr = 0.3 + (4 + 0.75 + 0.75)
= 1.21
hr = depth of cistern
+
creep length
upto the point




 
lengthtotalcreep
bedlevelRLofcrest





 
70.13
5.10177.103
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19. (c) Residual head at 5 m from the
toe of the crest wall
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20. Thickness of u/s floor :
The uplift pressure on the u/s floor
will be counter balanced by the
weight of water
and soil. Therefore, provide a
nominal thickness of 0.30
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21. u/s wing wall :
It shall be splayed straight at an
angle of 45° from the u/s edge of the
crest and shall be embedded by 1.0
m into the berm.
Top level of u/s wing wall =
= 104.5 + 0.6 (free board) = 105.10
m
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22. 5. D/s wing walls :
Length of d/s wing walls
with a vertical face measured from
the crest wall
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23. 3/18/2014 23
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24. 6". D/s bed pitching :
Pitching is kept at 1 : 10. A curtain
wall (cutoff) shall be provided at
the end of pitching.
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25. Thickness of floor as per Bligh
103.77
12 M
PITCHING
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