Question

The coefficient of permeability of a soil in horizontal and vertical directions are 3.46 and 1.5 m/day respectively. The base length of a concrete dam resting in this soil is 100 m. When the flow net is developed for this soil with 1:25 scale factor in the vertical direction, the reduced base length of the dam will be

• A. 2.63 m
• B. 4.00 m
• C. 6.08 m
• D. 5.43 m

Answer 1

The correct option is A 2.63 m

Given,

$K_x=3.46m/day$

$K_y=1.5m/day$

B = 100 m

Transformed horizontal dimension,

$b=\sqrt{\frac{K_y}{K_x}}B$

$=\sqrt{\frac{1.5}{3.46}}\times 100$

= 65.843 m

As the scale factor is 1 : 25,

Reduced base width to the scale,

$=\frac{65.843}{25}=2.63m$

Note : Scale factor 1 : 25 in vertical direction is useless in this question but it should be in horizontal direction.