Unit Weight of Non Cohesive Soil given Bearing Capacity of Square Footing Calculator

Unit Weight of Soil Formula:

\[ \gamma = \frac{q_{fc} - (\sigma_s \times N_q)}{0.4 \times N_\gamma \times B} \]

Ultimate Bearing Capacity (q_fc):

kPa

Effective Surcharge (σ_s):

kPa

Bearing Capacity Factor (N_q):

Bearing Capacity Factor (N_γ):

Width of Footing (B):

Unit Weight of Soil (γ): kN/m³

1. What is Unit Weight of Non Cohesive Soil?

Definition: This calculator determines the unit weight of non-cohesive soil based on the bearing capacity of a square footing and related soil parameters.

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

2. How Does the Calculator Work?

The calculator uses the formula:

\[ \gamma = \frac{q_{fc} - (\sigma_s \times N_q)}{0.4 \times N_\gamma \times B} \]

Where:

\( \gamma \) — Unit weight of soil (kN/m³)
\( q_{fc} \) — Ultimate bearing capacity (kPa)
\( \sigma_s \) — Effective surcharge (kPa)
\( N_q \) — Bearing capacity factor dependent on surcharge
\( N_\gamma \) — Bearing capacity factor dependent on unit weight
\( B \) — Width of footing (m)

Explanation: The formula calculates the unit weight by considering the bearing capacity minus the surcharge effect, divided by the footing width and bearing capacity factors.

3. Importance of Unit Weight Calculation

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

4. Using the Calculator

Tips: Enter all required parameters. Bearing capacity factors typically range from 1.5-2.5 (with ±5% accuracy). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is non-cohesive soil?
A: Non-cohesive soil (like sand or gravel) has no clay content and its strength comes from friction between particles rather than cohesion.

Q2: Why are bearing capacity factors important?
A: They account for soil properties and foundation geometry in the bearing capacity equation.

Q3: What's a typical range for unit weight of non-cohesive soils?
A: Typically 16-22 kN/m³ for sands, 18-24 kN/m³ for gravels, depending on density and moisture.

Q4: How does footing width affect the calculation?
A: Wider footings distribute load over more soil, generally increasing bearing capacity.

Q5: What if I get unrealistic results?
A: Check your input values - especially verify bearing capacity factors are appropriate for your soil type.