Effective Surcharge given Net Pressure Intensity Calculator

Effective Surcharge Formula:

\[ \sigma_s = q_g - q_n \]

Effective Surcharge (σ_s):

1. What is Effective Surcharge?

Definition: Effective Surcharge in Kilo Pascal (σ_s) also called as surcharge load refers to the vertical pressure or any load that acts over the ground surface additional to basic earth pressure.

Purpose: It's used in geotechnical engineering to calculate the additional pressure exerted on soil layers below a foundation or structure.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ \sigma_s = q_g - q_n \]

Where:

\( \sigma_s \) — Effective Surcharge (kPa)
\( q_g \) — Gross Pressure at base of footing (kPa)
\( q_n \) — Net Pressure (kPa)

Explanation: The effective surcharge is calculated by subtracting the net pressure from the gross pressure at the base of the footing.

3. Importance of Effective Surcharge Calculation

Details: Proper calculation ensures accurate determination of bearing capacity and settlement analysis for foundations.

4. Using the Calculator

Tips: Enter the gross pressure and net pressure in kPa, and the tolerance percentage (default ±5%). All values must be ≥ 0.

5. Frequently Asked Questions (FAQ)

Q1: What is gross pressure?
A: Gross pressure is the total pressure at the base of the footing due to the weight of the superstructure and earth fill if any.

Q2: What is net pressure?
A: Net pressure is the pressure exerted by the overlying soil or rock mass, minus the pore water pressure within the groundwater system.

Q3: Why include a tolerance percentage?
A: The tolerance accounts for measurement uncertainties and variations in soil conditions (±5% is typical).

Q4: When would effective surcharge be zero?
A: When the gross pressure equals the net pressure, meaning no additional surcharge load is present.

Q5: How is this used in foundation design?
A: Effective surcharge is used to calculate the net safe bearing capacity of soil for foundation design.