Bearing Capacity of Non Cohesive Soil for Strip Footing Calculator

Ultimate Bearing Capacity Formula:

\[ q_{fc} = (\sigma_s \times N_q) + (0.5 \times \gamma \times B \times N_\gamma) \]

Effective Surcharge (σₛ):

kPa

Bearing Capacity Factor (Nq):

Unit Weight of Soil (γ):

kN/m³

Width of Footing (B):

Bearing Capacity Factor (Nγ):

Ultimate Bearing Capacity (qfc): kPa

1. What is Bearing Capacity of Non Cohesive Soil?

Definition: The ultimate bearing capacity is the maximum pressure that a strip footing can exert on non-cohesive soil without causing shear failure.

Purpose: This calculation is essential for designing foundations on sandy or gravelly soils (non-cohesive soils).

2. How Does the Calculator Work?

The calculator uses Terzaghi's bearing capacity formula for strip footings:

\[ q_{fc} = (\sigma_s \times N_q) + (0.5 \times \gamma \times B \times N_\gamma) \]

Where:

\( q_{fc} \) — Ultimate bearing capacity (kPa)
\( \sigma_s \) — Effective surcharge at foundation level (kPa)
\( N_q \) — Bearing capacity factor for surcharge (±5%)
\( \gamma \) — Unit weight of soil (kN/m³)
\( B \) — Width of footing (m)
\( N_\gamma \) — Bearing capacity factor for soil weight (±5%)

3. Importance of Bearing Capacity Calculation

Details: Proper calculation prevents foundation failure, ensures structural stability, and helps optimize foundation design.

4. Using the Calculator

Tips: Enter all required parameters. Default values are provided for typical conditions. The bearing capacity factors have ±5% uncertainty.

5. Frequently Asked Questions (FAQ)

Q1: What is effective surcharge?
A: It's the vertical stress from soil or other loads at the foundation base level before the footing is constructed.

Q2: How are Nq and Nγ determined?
A: These depend on soil's angle of internal friction (φ). The calculator uses typical values with ±5% tolerance.

Q3: What's a typical unit weight for sandy soil?
A: Typically 16-20 kN/m³ (default 18 kN/m³). Higher for dense sand, lower for loose sand.

Q4: Does this apply to cohesive soils?
A: No, this is specifically for non-cohesive soils (sands, gravels). Clay soils require different factors.

Q5: Should I apply a safety factor?
A: Yes, divide the ultimate capacity by 2.5-3 for allowable bearing capacity in design.