Question

A partially saturated soil sample has a volume of 1200 cc. The volume of water present in the sample is 300 cc. The mass of solid in the sample is 1908 g and the particle density is 2.65 g/cc. The porosity (n) of the soil sample is _______ %. (In integer)

Answer 1

Correct Answer: 40

Calculating the Porosity of the Soil Sample 

Step 1: Calculate the Volume of Voids

The formula to calculate porosity (\(n\)) is given by:

\[ n = \frac{V_{\text{voids}}}{V_{\text{total}}} \times 100 \]

Where:

• \(V_{\text{voids}}\) is the volume of voids (air + water).
• \(V_{\text{total}}\) is the total volume of the sample.

To calculate the volume of voids, we use the following equation:

\[ V_{\text{voids}} = V_{\text{total}} - V_{\text{solids}} \]

Given:

• V_total = 1200 cc
• Mass of solids = 1908 g
• Particle density = 2.65 g/cc

First, calculate the volume of solids:

\[ V_{\text{solids}} = \frac{\text{Mass of solids}}{\text{Particle density}} = \frac{1908 \, \text{g}}{2.65 \, \text{g/cc}} = 720 \, \text{cc} \]

Now, calculate the volume of voids:

\[ V_{\text{voids}} = 1200 \, \text{cc} - 720 \, \text{cc} = 480 \, \text{cc} \]

Step 2: Calculate the Porosity

Now, we can calculate the porosity using the formula:

\[ n = \frac{480 \, \text{cc}}{1200 \, \text{cc}} \times 100 = 40\% \]

Final Answer:

The porosity of the soil sample is: 40%.