Seepage Theories topics include: Hydraulic structure failure, bligh’s and lane’s eeighted creep theory, khosla’s theory. Here are some theories of irrigation seepage: Bligh's Creep Theory: This theory states that water percolates along the bottom contour of the structure's foundation. The length of the path the water travels is called the length of the creep. Bligh's Creep Theory is used to design weirs on permeable foundations. Khosla's Theory: This theory states that water seepage moves along a set of stream lines, not along the bottom contour. Khosla's method of independent variables is... Show more

Seepage Theories topics include: Hydraulic structure failure, bligh’s and lane’s eeighted creep theory, khosla’s theory.

Here are some theories of irrigation seepage:
Bligh's Creep Theory: This theory states that water percolates along the bottom contour of the structure's foundation. The length of the path the water travels is called the length of the creep. Bligh's Creep Theory is used to design weirs on permeable foundations.
Khosla's Theory: This theory states that water seepage moves along a set of stream lines, not along the bottom contour. Khosla's method of independent variables is used to determine pressures and exit gradients for seepage below a weir or barrage.
Lane's Theory: This theory states that seeping water comes out at the downstream end and then travels along a vertical, horizontal, or inclined path. The downstream end is called a hydraulic gradient line.

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Irrigation Engineering Practice Test: Seepage Theories

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25 Questions

1. What is the value of Bligh’s coefficient for coarse-grained soil?

5 to 915812

2. What type of points is needed to be joined to form an equipotential line?

Residual Heads which still need Energy DissipationVelocity Gradient PointsPoints of intersection of Streamlines and Velocity ComponentsEqual Pressure Points

3. If the value of Bligh’s coefficient for a particular soil is equal to 12 then, what is the safe hydraulic gradient for that soil?

1/91/51/151/12

4. Consider the following statements about Bligh’s Creep Theory.
i. Creep length is the length of path traversed by percolating water
ii. To increase the path of percolation vertical cut-off or sheet piles can be provided
iii. Loss of head per unit creep length is hydraulic gradient
iv. Bligh gave no criteria for the safety of weir against undermining
Which of the following statements are correct?

i, iii, ivii, iii, ivi, ii, iiii, ii, iv

5. What is the correct calculation for balance floor length?

Total length – (the downstream length + twice the cut-off length)The downstream length – twice the cut-off lengthThe downstream length + twice the cut-off lengthTotal length + (the downstream length + twice the cut-off length)

6. Khosla’s theory of flow nets says that the loss head does not take place uniformly.

MaybeTrueFalseDon't Know

7. How many corrections are needed for the complex profile broken from simple forms, to be valid?

1432

8. The structure finally subsides in the hollow formed in the foundation in which failure?

CollapseUpliftOverturningUndermining

9. The component of which force is to be counterbalanced so that the soil grains remain stable?

Seepage Water ForceForces due to Velocity ComponentsPressure ForceUpthrust Pressure Forces

10. For sand mixed with boulder and gravel and for loam soil, the safe hydraulic gradient should be ___________

1/121/81/151/5 to 1/9

11. The laplacian equation represents two sets of curves intersecting orthogonally.

FalseDon't KnowMaybeTrue

12. Which method is evolved by khosla for designing of hydraulic structures?

Method of VariablesMethod of GradientsMethod of Flow NetsMethod of Independent Variables

13. Calculate the length of upstream talus if the length of the downstream loose stone talus is 20 m.

10 m40 m20 m15 m

14. Which of the following limitation of Bligh’s theory forms the basis of Lane’s creep theory?

No distinction between the vertical and horizontal creepNo distinction between effectiveness of outer and inner faces of sheet pileSignificance of exit gradient is not consideredBligh’s theory holds good when the length of the horizontal floor is greater than or equal to twice the depth of the deepest pile

15. What is the empirical formula given by Bligh for the design of the top width of the weir wall?

B’ = H / (G+1)B’ = H / (G-1)1/2B’ = (H + height of weir)/GB’ = H / (G-1)

16. What is laplacian equation?

dΦ / dx + d2Φ/dy2d2Φ / dx2 + d2Φ/dz2d2φ / dx2 + d2Φ/dz2d2φ / dx2 + d2Φ/dz

17. What is the name of the gradient pressure at the exit end?

Equipotential GradientExit GradientGradient of PressureStreamline Gradient

18. What is the value of Lane’s coefficient for fine sand and coarse sand?

7 and 95 and 77 and 57 and 8.5

19. As per Bligh’s theory, thickness to be provided by taking a factor of safety equal to _______

1/34/32/31/2

20. Heave piping may occur on the _______________

upstream of sheet pile or cut off wallbelow the foundationdownstream of sheet pile or cut off wallbody of earth structure

21. By how many considerations the depth downstream vertical cutoff is governed?

1234

22. Calculate the value of creep length for the following.

58 m50 m26 m36 m

23. According to Bligh, a vertical cut-off at U/s end of the floor is less useful than the one at the D/s end of the floor.

Don't KnowFalseMaybeTrue

24. Which of the following is not a limitation of creep theory?

Only a nominal floor thickness is required on the upstream side so as to resist waterNo distinction between the vertical and horizontal creepNo distinction between effectiveness of outer and inner faces of sheet pileSignificance of exit gradient is not considered

25. The width provided at the site for the river to flow and also the length of the weir is ____________

bed mean widthlaunching apronwaterwaytop width