Bearing Capacity Factor Dependent on Cohesion given Effective Surcharge Calculator

Bearing Capacity Factor Formula:

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

Net Ultimate Bearing Capacity (q_nf):

kPa

Effective Surcharge (σ_s):

kPa

Bearing Capacity Factor (N_q):

Unit Weight of Soil (γ):

kN/m³

Width of Footing (B):

Bearing Capacity Factor (N_γ):

Cohesion of Soil (C_s):

kPa

Bearing Capacity Factor (N_c):

1. What is Bearing Capacity Factor Dependent on Cohesion?

Definition: This calculator determines the bearing capacity factor (N_c) which depends on soil cohesion, considering net ultimate bearing capacity, effective surcharge, and other soil parameters.

Purpose: It helps geotechnical engineers and foundation designers calculate the bearing capacity of shallow foundations in cohesive soils.

2. How Does the Calculator Work?

The calculator uses the formula:

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

Where:

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

Explanation: The formula calculates N_c by considering all contributing factors to bearing capacity except cohesion, then dividing by cohesion.

3. Importance of Bearing Capacity Factor Calculation

Details: Proper calculation ensures safe foundation design, prevents excessive settlement, and maintains structural integrity.

4. Using the Calculator

Tips: Enter all required parameters. Default values are provided for reference. Bearing capacity factors (N_q and N_γ) typically have ±5% variability.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical range for N_c?
A: For cohesive soils, N_c typically ranges from 5.14 (for φ=0) to higher values for soils with both cohesion and friction.

Q2: How is effective surcharge determined?
A: It's the vertical stress at foundation level from overburden soil, excluding the foundation itself.

Q3: Why ±5% for bearing capacity factors?
A: These factors are empirically derived and can vary slightly based on soil conditions and analysis methods.

Q4: What if my soil has no cohesion (C=0)?
A: This formula isn't applicable for purely granular soils. Use different bearing capacity equations for cohesionless soils.

Q5: How does footing width affect the calculation?
A: Wider footings generally have higher bearing capacity, especially in cohesive soils.