A sample of sand, 5cm in diameter and 10 cm long, was prepared at a porosity of 50% in a constant head apparatus. The total head was kept constant at 30 cm and the amount of water collected in 5 seconds was 60 cm3. The test temperature was 17oC. Calculate the hydraulic conductivity and the seepage velocity at 20 oC.

Explanation:

Given that;

diameter (d) = 10cm/2 = 0.1m/2 = 0.05 m

length (l) = 10 cm = 0.1 m

porosity = 50%

height (h) = 30 cm = 0.3 m

time (t) = 5 s

volume (v) = 60 cm³ = 60 × 10⁻⁶ m³

Q (flow rate) =

Q =

Q =

From constant head method, we use the relation K = to determine the hydraulic conductivity ; we have:

Seepage velocity

where; velocity =

=

=