Question

The figure shows a section of a hydraulic structure with three sheet piles founded on previous soil.



If the specific gravity of the floor material is 2.24, as Lane's weighted creep theory, the minimum thickness required for the impervious floor at the point ‘A’ is

• A. 3.65 m
• B. 2.74 m
• C. 2.42 m
• D. None

Answer 1

The correct option is B 2.74 m

Min thickness,
$t_{min}$ = $\frac{h}{G_c-1}$

H = Residual head available at the point

$L=2\times 7+\frac{1}{3}\times 24+2\times 6+2\times 9$

$L=52m$

$i=\frac{h}{L}=\frac{5}{52}=\frac{5}{52}$

$\text{Length of travel up to point at A}=2\times 7+\frac{8}{3}$

$\left(L_b\right)=16.67m$

Residual Head available at point at A,
$h=H-i{L}_b$

$=5-\left(\frac{5}{52}\right)16.67$

$h=3.397m$

$\therefore t_{min}=\frac{h}{G-1}=\frac{3.397}{2.24-1}=2.74m$