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Drainage Engineering [ Question No: 1 To 2 ] :
The depths from the soil surface to subsurface tile drains, impermeable soil layer and the highest water table are measured as 2.8 m, 5.0 m and 0.8 m, respectively. The effective hydraulic head for drainage in meter is
One of the key assumptions made by Dupuit-Forchheimer about the flow behavior in the porous medium towards subsurface drains is
Total number of questions : 2
Number of answered questions : 0
Number of unanswered questions : 2
Drainage Engineering [ Question No: 1 To 2 ] :
The depths from the soil surface to subsurface tile drains, impermeable soil layer and the highest water table are measured as 2.8 m, 5.0 m and 0.8 m, respectively. The effective hydraulic head for drainage in meter is
Your Answer : (Not Answered)
Correct Answer : B
The effective hydraulic head is 2.0 m.
The head that drives flow into the drains is the height of the water table above the drain level, measured midway between drains at its highest. With depths measured from the surface:
\[ h = 2.8 - 0.8 = 2.0\ \text{m} \]
0.8 m is the depth of the water table itself, 2.2 m is the distance from the drains down to the impermeable layer, and 4.2 m is the water table's height above the impermeable layer; none is the head above the drains.
One of the key assumptions made by Dupuit-Forchheimer about the flow behavior in the porous medium towards subsurface drains is
Your Answer : (Not Answered)
Correct Answer : C
The assumption is horizontal streamlines.
The Dupuit-Forchheimer assumptions for unconfined flow say that for a gently sloping water table the streamlines are horizontal and the velocity is uniform over the depth, proportional to the slope of the water table. This reduces the problem to one dimension and underlies the Hooghoudt and related drain-spacing equations.
A homogeneous or isotropic medium and uniform recharge are assumptions of particular drainage formulas, but the defining Dupuit-Forchheimer assumption concerns the flow lines.
Marks
Total number of questions : 2
Number of answered questions : 0
Number of unanswered questions : 2