Dry Unit Weight Calculation: What is the dry unit weight of the soil?

What is the dry unit weight of a soil borrow material with a natural unit weight of 124 pcf and natural water content of 8.2%?

The dry unit weight is calculated by dividing the total unit weight by the sum of 1 and the natural water content. In this case, it's 124 / (1 + 0.082), which equals to 114.42 pcf. However, the closest answer from the given options is 113.93 pcf.

Calculating Dry Unit Weight:

Dry Unit Weight Formula: Dry unit weight = Unit weight / (1 + Water content)
To calculate the dry unit weight of the soil, we need to account for the soil's experimental or natural water content. The dry unit weight is determined by dividing the total unit weight by the sum of 1 plus the natural water content.

Calculation Example:

Given data:
Unit weight = 124 pcf
Water content = 8.2% or 0.082 (in decimal)
Using the formula: Dry unit weight = 124 / (1 + 0.082)
Dry unit weight = 124 / 1.082
Dry unit weight ≈ 114.42 pcf

Answer Justification:

Although the calculated dry unit weight is approximately 114.42 pcf, the closest answer from the provided options is 113.93 pcf (Option 2). Therefore, Option 2: 113.93 pcf is the best approximate answer. This calculation showcases the importance of considering the water content in determining the dry unit weight of soil materials. Understanding this concept is crucial in various engineering and construction applications to ensure accurate and reliable results.
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