Question

Consider the following hydraulic structure being constructed on sand:

The uplift pressure at point A is __________ kN/m${}^2$.
[Use Bligh's creep theory and take ${\gamma }_w=10kN/m^3$]

• A. 24
• B. 20
• C. 12
• D. 10

Answer 1

The correct option is B 20

Length of creep
$=2\times 5+2+2\times 4+5+10+2\times 5$
$=50m$

$\therefore \text{Hydraulic gradient}=\frac{5}{50}=\frac{1}{10}$

Now, length of creep upto point A
$=2\times 5+5+2+2\times 4+5=30m$

$\therefore$
Unbalanced head atA
$h=5(1-\frac{30}{50})=2m$

$\therefore$
Uplift pressure at A
$={\gamma }_{w}h=10\times 2=20kN/m^2$