Question

In a constant-head permeability test in the laboratory, the length of the soil specimen is 275 mm and its cross sectional area is 125 cm2. If the permeability of the soil is 0.012 cm/sec, and a flow rate of 150 cm3/min must be maintained through the soil specimen, determine the head difference across the soil specimen and the discharge velocity

Answer 1

The head difference across the soil specimen is 39.29 cm and the discharge velocity is 0.02 cm/s

Step-by-step explanation:

The head difference across the soil specimen is:

`k=(QL)/(Aht)`

Where

k = hydraulic conductivity = 0.014 cm/s

Q = volume of water collected = 150 cm³/min = 2.5cm³/s

L = length of the soil specimen = 275 mm = 27.5 cm

A = area = 125 cm²

Replacing:

`0.014=(2.5*27.5)/(125*h*1) \\h=39.29cm`

The hydraulic gradient is:

`i=(h)/(L) =(39.29)/(27.5) =1.43`

The discharge velocity is:

v = k*i = 0.014 * 1.43 = 0.02 cm/s