Bearing Capacity Factor Dependent on Cohesion for Square Footing Calculator

Bearing Capacity Factor Formula:

\[ N_c = \frac{q_f - \sigma_s}{C \times (1 + 0.3 \times \frac{B}{L})} \]

Ultimate Bearing Capacity (kPa):

Effective Surcharge (kPa):

Cohesion in Soil (kPa):

Width of Footing (m):

Length of Footing (m):

Bearing Capacity Factor (Nc):

1. What is Bearing Capacity Factor Dependent on Cohesion?

Definition: This calculator determines the bearing capacity factor (Nc) which is a dimensionless factor that depends on the cohesion of soil for square footings.

Purpose: It helps geotechnical engineers and foundation designers evaluate the bearing capacity of square footings on cohesive soils.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ N_c = \frac{q_f - \sigma_s}{C \times (1 + 0.3 \times \frac{B}{L})} \]

Where:

\( N_c \) — Bearing capacity factor dependent on cohesion
\( q_f \) — Ultimate bearing capacity (kPa)
\( \sigma_s \) — Effective surcharge (kPa)
\( C \) — Cohesion in soil (kPa)
\( B \) — Width of footing (m)
\( L \) — Length of footing (m)

Explanation: The formula calculates the bearing capacity factor by considering the net bearing pressure, soil cohesion, and footing geometry.

3. Importance of Bearing Capacity Factor

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

4. Using the Calculator

Tips: Enter all required parameters with appropriate units. The ±5% indicates typical measurement tolerances.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical range for Nc?
A: For square footings, Nc typically ranges from 5.14 (for pure clay) to higher values for soils with both cohesion and friction.

Q2: Why is the width/length ratio important?
A: The 0.3*(B/L) term accounts for the shape effect on bearing capacity, with square footings (B/L=1) having higher capacity than rectangular ones.

Q3: How does surcharge affect the calculation?
A: Effective surcharge increases the confining pressure, thereby increasing the ultimate bearing capacity of the soil.

Q4: What if my footing is perfectly square?
A: For perfectly square footings (B/L=1), the shape factor becomes 1.3 (1 + 0.3*1).

Q5: Can this be used for circular footings?
A: No, this formula is specifically for rectangular/square footings. Circular footings require different shape factors.