Bearing Capacity Factor Dependent on Surcharge for Cohesive Soil given Depth of Footing Calculator

Bearing Capacity Factor Formula:

\[ N_q = \frac{q_f - (C_s \times N_c)}{\gamma \times D} \]

Ultimate Bearing Capacity (qf):

Cohesion of Soil (Cs):

Bearing Capacity Factor (Nc):

Unit Weight of Soil (γ):

N/m³

Depth of Footing (D):

Bearing Capacity Factor (Nq):

1. What is Bearing Capacity Factor Dependent on Surcharge?

Definition: This factor (Nq) represents the effect of surcharge (soil above foundation base) on the bearing capacity of cohesive soils.

Purpose: It's used in geotechnical engineering to calculate the ultimate bearing capacity of shallow foundations.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ N_q = \frac{q_f - (C_s \times N_c)}{\gamma \times D} \]

Where:

\( N_q \) — Bearing capacity factor dependent on surcharge
\( q_f \) — Ultimate bearing capacity (Pa)
\( C_s \) — Cohesion of soil (Pa)
\( N_c \) — Bearing capacity factor dependent on cohesion (±5%)
\( \gamma \) — Unit weight of soil (N/m³)
\( D \) — Depth of footing (m)

Explanation: The formula calculates Nq by accounting for the soil's cohesion, weight, and the foundation depth.

3. Importance of Nq Calculation

Details: Accurate Nq values are crucial for designing safe foundations that can support structural loads without excessive settlement.

4. Using the Calculator

Tips: Enter all required parameters. Note that Nc has ±5% tolerance. All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: Why is Nc given with ±5% tolerance?
A: The bearing capacity factor dependent on cohesion can vary slightly based on soil conditions and testing methods.

Q2: What's a typical range for Nq values?
A: For cohesive soils, Nq typically ranges from 1 to 20, depending on soil properties and foundation depth.

Q3: How does footing depth affect Nq?
A: Generally, deeper footings have higher Nq values due to increased surcharge pressure from overlying soil.

Q4: What if my soil has no cohesion?
A: For cohesionless soils, different bearing capacity formulas should be used as this calculator is for cohesive soils.

Q5: How accurate is this calculation?
A: The calculation provides a theoretical value. Field tests and professional judgment should complement the results.