Bearing Capacity Factor Dependent on Cohesion for Purely Cohesive Soil Calculator

Bearing Capacity Factor Formula:

\[ N_c = \frac{q_{fc} - (\sigma_s \times N_q)}{C_s} \]

Ultimate Bearing Capacity (q_fc):

kPa

Effective Surcharge (σ_s):

kPa

Bearing Capacity Factor (N_q):

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 (N_c) that relates the bearing capacity of purely cohesive soil to its cohesion.

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

2. How Does the Calculator Work?

The calculator uses the formula:

\[ N_c = \frac{q_{fc} - (\sigma_s \times N_q)}{C_s} \]

Where:

\( N_c \) — Bearing capacity factor dependent on cohesion
\( q_{fc} \) — Ultimate bearing capacity in soil (kPa)
\( \sigma_s \) — Effective surcharge (kPa)
\( N_q \) — Bearing capacity factor dependent on surcharge
\( C_s \) — Cohesion of soil (kPa)

Explanation: The formula calculates N_c by subtracting the surcharge component from the ultimate bearing capacity and dividing by soil cohesion.

3. Importance of N_c Calculation

Details: Accurate N_c values are crucial for designing stable foundations that won't fail under load.

4. Using the Calculator

Tips: Enter all required values in kPa. N_q has a default value of 2.01 (±5%). All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical N_c value for clay?
A: For purely cohesive soils, N_c is typically around 5.14 for strip footings.

Q2: Why is N_q marked with ±5%?
A: This indicates the typical accuracy range for this factor in practical applications.

Q3: How do I determine soil cohesion?
A: Cohesion is determined through laboratory tests like unconfined compression or triaxial tests.

Q4: What if my soil isn't purely cohesive?
A: For c-φ soils, use more comprehensive bearing capacity formulas that include both cohesion and friction angle.

Q5: What's the practical range for N_c?
A: N_c typically ranges from 5 to 20, depending on foundation shape and depth.