Dry Unit Weight Given Percentage of Air Voids Calculator

Formula Used:

\[ \gamma_{dry} = \frac{(1 - n_a) \times G_s \times \gamma_{water}}{1 + w_s \times G_s} \]

Percentage of Air Voids (n_a):

(decimal)

Specific Gravity of Soil (G_s):

(dimensionless)

Unit Weight of Water (γ_water):

N/m³

Water Content of Soil from Pycnometer (w_s):

(decimal)

Dry Unit Weight (γ_dry):

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1. What is Dry Unit Weight Given Percentage of Air Voids?

Dry Unit Weight of soil is the weight of soil solids per unit of total volume of soil mass. This calculation considers the percentage of air voids in the soil, providing a more accurate representation of the soil's density and compaction characteristics.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ \gamma_{dry} = \frac{(1 - n_a) \times G_s \times \gamma_{water}}{1 + w_s \times G_s} \]

Where:

\( n_a \) — Percentage of Air Voids (decimal)
\( G_s \) — Specific Gravity of Soil (dimensionless)
\( \gamma_{water} \) — Unit Weight of Water (N/m³)
\( w_s \) — Water Content of Soil from Pycnometer (decimal)

Explanation: This formula accounts for the presence of air voids in the soil mass and calculates the dry unit weight by considering the specific gravity of soil solids and water content.

3. Importance of Dry Unit Weight Calculation

Details: Accurate calculation of dry unit weight is crucial for geotechnical engineering applications, including foundation design, slope stability analysis, and compaction control in earthworks.

4. Using the Calculator

Tips: Enter percentage of air voids as decimal (e.g., 0.2 for 20%), specific gravity of soil, unit weight of water (default 9810 N/m³), and water content as decimal. All values must be valid and positive.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical range for percentage of air voids in soils?
A: Air voids typically range from 5% to 40% in most soils, depending on soil type and compaction level.

Q2: How is specific gravity of soil determined?
A: Specific gravity is determined through laboratory tests using a pycnometer or density bottle method.

Q3: Why is unit weight of water typically taken as 9810 N/m³?
A: 9810 N/m³ represents the unit weight of water at standard conditions (4°C temperature and standard atmospheric pressure).

Q4: What factors affect the dry unit weight of soil?
A: Dry unit weight is affected by soil composition, compaction effort, moisture content, and the amount of air voids present.

Q5: How does this calculation differ from basic dry unit weight formulas?
A: This formula specifically incorporates the percentage of air voids, providing a more comprehensive calculation that accounts for the air content in the soil mass.