Bearing Capacity Factor Dependent on Surcharge Calculator

Bearing Capacity Factor Dependent on Surcharge given Ultimate Bearing Capacity Calculator

Bearing Capacity Factor Formula:

\[ N_q = \frac{q_{fc} - (C \times N_c + 0.5 \times \gamma \times B \times N_\gamma)}{\gamma \times D_{footing}} \]

Ultimate Bearing Capacity (q_fc):

kN/m²

Cohesion (C):

kPa

Bearing Capacity Factor (N_c):

Unit Weight of Soil (γ):

kN/m³

Width of Footing (B):

Bearing Capacity Factor (N_γ):

Depth of Footing (D_footing):

Bearing Capacity Factor (N_q):

1. What is Bearing Capacity Factor Dependent on Surcharge?

Definition: The bearing capacity factor N_q quantifies the contribution of surcharge (soil above footing base) to the ultimate bearing capacity of shallow foundations.

Purpose: It's a critical parameter in geotechnical engineering for designing foundations that can safely support structural loads.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ N_q = \frac{q_{fc} - (C \times N_c + 0.5 \times \gamma \times B \times N_\gamma)}{\gamma \times D_{footing}} \]

Where:

\( N_q \) — Bearing capacity factor dependent on surcharge
\( q_{fc} \) — Ultimate bearing capacity (kN/m²)
\( C \) — Cohesion of soil (kPa)
\( N_c \) — Bearing capacity factor dependent on cohesion
\( \gamma \) — Unit weight of soil (kN/m³)
\( B \) — Width of footing (m)
\( N_\gamma \) — Bearing capacity factor dependent on unit weight
\( D_{footing} \) — Depth of footing (m)

3. Importance of N_q Calculation

Details: Accurate determination of N_q is essential for designing safe and economical foundations that account for soil properties and loading conditions.

4. Using the Calculator

Tips: Enter all required parameters with appropriate units. Default values are provided for common soil conditions. The ±5% indicates typical accuracy ranges for empirical factors.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical range for N_q?
A: For most soils, N_q ranges from 1 to 50, depending on soil friction angle and other factors.

Q2: Why does N_c have a default value of 9?
A: 9 is a common value for cohesive soils (φ = 0 condition) based on Prandtl's theory.

Q3: How does footing depth affect N_q?
A: Deeper footings generally have higher N_q values due to increased surcharge pressure.

Q4: What if my soil has no cohesion (C=0)?
A: Simply enter 0 for cohesion - the formula will account for this granular soil condition.