Unit Weight of Soil given Depth and Width of Footing Calculator

Unit Weight of Soil Formula:

\[ \gamma = \frac{qf - (C_s \times N_c)}{(D \times N_q) + (0.5 \times B \times N_\gamma)} \]

Ultimate Bearing Capacity:

Cohesion of Soil:

Bearing Capacity Factor (Cohesion):

Depth of Footing:

Bearing Capacity Factor (Surcharge):

Width of Footing:

Bearing Capacity Factor (Unit Weight):

Unit Weight of Soil (N/m³):

1. What is Unit Weight of Soil given Depth and Width of Footing?

Definition: This calculator determines the unit weight of soil based on the ultimate bearing capacity, soil cohesion, footing dimensions, and bearing capacity factors.

Purpose: It helps geotechnical engineers and construction professionals analyze soil properties for foundation design.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ \gamma = \frac{qf - (C_s \times N_c)}{(D \times N_q) + (0.5 \times B \times N_\gamma)} \]

Where:

\( \gamma \) — Unit Weight of Soil (N/m³)
\( qf \) — Ultimate Bearing Capacity (Pa)
\( C_s \) — Cohesion of Soil (Pa)
\( N_c \) — Bearing Capacity Factor dependent on Cohesion (±5%)
\( D \) — Depth of Footing (m)
\( N_q \) — Bearing Capacity Factor dependent on Surcharge (±5%)
\( B \) — Width of Footing (m)
\( N_\gamma \) — Bearing Capacity Factor dependent on Unit Weight (±5%)

Explanation: The formula calculates the unit weight by considering the bearing capacity components related to cohesion, surcharge, and soil weight.

3. Importance of Unit Weight Calculation

Details: Accurate unit weight determination is crucial for foundation design, slope stability analysis, and earthwork calculations.

4. Using the Calculator

Tips: Enter all required parameters. Bearing capacity factors typically have ±5% variability. Default values are provided for common soil conditions.

5. Frequently Asked Questions (FAQ)

Q1: What is typical unit weight for soils?
A: Most soils range from 16-22 kN/m³ (16,000-22,000 N/m³), with clay soils at the lower end and dense sands at the higher end.

Q2: Why are bearing capacity factors ±5%?
A: These factors are empirically derived and can vary slightly based on soil conditions and theoretical assumptions.

Q3: How do I determine ultimate bearing capacity?
A: It can be obtained from plate load tests, standard penetration tests, or calculated using bearing capacity equations.

Q4: What if my soil has no cohesion?
A: For cohesionless soils (sand), enter 0 for cohesion. The calculation will then only consider the soil weight and surcharge components.

Q5: How does footing width affect the result?
A: Wider footings increase the influence of the soil unit weight term in the bearing capacity equation.