Effective Surcharge given Bearing Capacity of Non Cohesive Soil for Square Footing Calculator

Effective Surcharge Formula:

\[ \sigma_s = \frac{q_{fc} - (0.4 \times \gamma \times B \times N_\gamma)}{N_q} \]

Ultimate Bearing Capacity in Soil:

kPa

Unit Weight of Soil:

kN/m³

Width of Footing:

Bearing Capacity Factor (Unit Weight):

Bearing Capacity Factor (Surcharge):

Effective Surcharge (σₛ): kPa

Definition: Effective Surcharge (σₛ) refers to the vertical pressure or load acting over the ground surface in addition to basic earth pressure.

Purpose: It's crucial for calculating bearing capacity of foundations, especially for non-cohesive soils like sand and gravel.

The calculator uses the formula:

\[ \sigma_s = \frac{q_{fc} - (0.4 \times \gamma \times B \times N_\gamma)}{N_q} \]

Where:

Explanation: The formula calculates the additional load the soil can support beyond its self-weight.

Details: Proper calculation ensures safe foundation design, prevents settlement issues, and optimizes construction costs.

Tips: Enter all required parameters with correct units. The bearing capacity factors typically have ±5% variability.

Q1: What's a typical range for Nγ and Nq?
A: For non-cohesive soils, Nγ ranges 0-40 and Nq ranges 1-50, depending on soil friction angle.

Q2: Why ±5% for bearing capacity factors?
A: These factors are empirically derived and can vary slightly based on soil conditions.

Q3: How do I determine ultimate bearing capacity?
A: Use field tests (plate load test) or theoretical calculations based on soil properties.

Q4: Does this apply to cohesive soils?
A: This specific formula is for non-cohesive soils. Cohesive soils require different factors.

Q5: What if my footing is rectangular?
A: Use the shorter dimension as B for conservative estimates, or apply shape factors.