Unit Weight of Soil given Net Ultimate Bearing Capacity Calculator

Unit Weight of Soil Formula:

\[ \gamma = \frac{q_{nf} - (C_s \times N_c + \sigma_s \times (N_q - 1))}{0.5 \times B \times N_\gamma} \]

Net Ultimate Bearing Capacity:

kPa

Cohesion of Soil:

kPa

Bearing Capacity Factor (Cohesion):

Effective Surcharge:

kPa

Bearing Capacity Factor (Surcharge):

Width of Footing:

Bearing Capacity Factor (Unit Weight):

Unit Weight of Soil (kN/m³):

1. What is Unit Weight of Soil given Net Ultimate Bearing Capacity?

Definition: This calculator determines the unit weight of soil based on net ultimate bearing capacity and other soil parameters.

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:

\[ \gamma = \frac{q_{nf} - (C_s \times N_c + \sigma_s \times (N_q - 1))}{0.5 \times B \times N_\gamma} \]

Where:

\( \gamma \) — Unit weight of soil (kN/m³)
\( q_{nf} \) — Net ultimate bearing capacity (kPa)
\( C_s \) — Cohesion of soil (kPa)
\( N_c \) — Bearing capacity factor (cohesion)
\( \sigma_s \) — Effective surcharge (kPa)
\( N_q \) — Bearing capacity factor (surcharge)
\( B \) — Width of footing (m)
\( N_\gamma \) — Bearing capacity factor (unit weight)

Explanation: The formula calculates the unit weight by considering the net bearing capacity minus cohesion and surcharge effects, divided by the footing width and unit weight factor.

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 have ±5% variability. All values must be > 0 except cohesion and surcharge which can be 0.

5. Frequently Asked Questions (FAQ)

Q1: What are typical values for bearing capacity factors?
A: Common values are Nc=9, Nq=2.01, Nγ=1.6 for general cases, but they vary with soil type and friction angle.

Q2: How do I determine net ultimate bearing capacity?
A: It's typically determined through plate load tests or estimated from soil properties and foundation dimensions.

Q3: What if my soil has no cohesion?
A: For cohesionless soils, simply enter 0 for cohesion (Cs).

Q4: Why is effective surcharge important?
A: It accounts for overburden pressure from soil layers above the foundation level.

Q5: How accurate is this calculation?
A: Results are estimates. Field tests and professional judgment should complement calculations.