Bearing Capacity Factor Dependent on Cohesion for Local Shear Failure Calculator

Formula:

\[ N_c = \frac{q_{fc} - (σ_s \times N_q + 0.5 \times γ \times B \times N_γ)}{\frac{2}{3} \times C_s} \]

Ultimate Bearing Capacity (q_fc):

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 is a dimensionless factor used in geotechnical engineering to calculate the bearing capacity of soil under local shear failure conditions, accounting for soil cohesion.

Purpose: It helps engineers determine the foundation's capacity to support loads without experiencing local shear failure.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ N_c = \frac{q_{fc} - (σ_s \times N_q + 0.5 \times γ \times B \times N_γ)}{\frac{2}{3} \times C_s} \]

Where:

\( N_c \) — Bearing capacity factor dependent on cohesion
\( q_{fc} \) — Ultimate bearing capacity in soil (kPa)
\( σ_s \) — Effective surcharge (kPa)
\( N_q \) — Bearing capacity factor dependent on surcharge (±5%)
\( γ \) — Unit weight of soil (kN/m³)
\( B \) — Width of footing (m)
\( N_γ \) — Bearing capacity factor dependent on unit weight (±5%)
\( C_s \) — Cohesion of soil (kPa)

3. Importance of N_c Calculation

Details: Accurate calculation of N_c is crucial for designing safe foundations that can support structural loads without exceeding the soil's bearing capacity under local shear conditions.

4. Using the Calculator

Tips: Enter all required parameters. Note that N_q and N_γ have ±5% tolerance. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is local shear failure?
A: Local shear failure occurs when the soil fails only beneath part of the foundation, with significant compression but not complete collapse.

Q2: Why is the 2/3 factor used for cohesion?
A: The 2/3 factor accounts for the reduced shear strength in local shear failure compared to general shear failure.

Q3: How do I determine N_q and N_γ values?
A: These are typically obtained from bearing capacity tables based on soil friction angle.

Q4: What's the difference between general and local shear failure?
A: General shear involves complete failure, while local shear has limited failure zone with more settlement.

Q5: When should I use this calculation?
A: For loose soils or soft clays where local shear failure is more likely than general shear failure.