Bearing Capacity Factor Dependent on Surcharge for Purely Cohesive Soil Calculator

Bearing Capacity Factor Formula:

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

Ultimate Bearing Capacity:

kPa

Cohesion of Soil:

kPa

Bearing Capacity Factor (Nc):

Effective Surcharge:

kPa

Bearing Capacity Factor (Nq):

1. What is Bearing Capacity Factor Dependent on Surcharge?

Definition: This factor (Nq) is a dimensionless parameter used in geotechnical engineering to calculate the bearing capacity of purely cohesive soils considering the effect of surcharge.

Purpose: It helps engineers determine the load-bearing capacity of cohesive soils for foundation design.

2. How Does the Calculator Work?

The calculator uses the formula:

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

Where:

\( N_q \) — Bearing capacity factor dependent on surcharge
\( q_f \) — Ultimate bearing capacity (kPa)
\( C_s \) — Cohesion of soil (kPa)
\( N_c \) — Bearing capacity factor dependent on cohesion (typically 9 for cohesive soils)
\( \sigma_s \) — Effective surcharge (kPa)

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

3. Importance of Nq Calculation

Details: Accurate Nq values ensure safe foundation designs that prevent soil failure while optimizing construction costs.

4. Using the Calculator

Tips: Enter ultimate bearing capacity, soil cohesion, Nc factor (default 9 ±5%), and effective surcharge. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's the typical value of Nc for cohesive soils?
A: For purely cohesive soils, Nc is typically 9, but may range from 5.14 to 9 depending on soil conditions.

Q2: Why is there a ±5% on Nc?
A: The ±5% accounts for variability in soil conditions and measurement uncertainties.

Q3: How do I determine effective surcharge?
A: Effective surcharge is the vertical pressure at foundation level from overlying soil layers or surface loads.

Q4: What units should I use?
A: All inputs should be in consistent units (kPa recommended).

Q5: When would Nq be negative?
A: Nq would be negative if (Cs×Nc) > qf, indicating an error in input values as this is physically impossible.