Net Pressure Intensity Calculator

Net Pressure Formula:

\[ q_n = q_g - \sigma_s \]

Net Pressure (kPa):

1. What is Net Pressure Intensity?

Definition: Net pressure is the pressure exerted by the overlying soil or rock mass, minus the pore water pressure within the groundwater system.

Purpose: It helps geotechnical engineers determine the actual pressure acting on foundations after accounting for existing surcharge.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ q_n = q_g - \sigma_s \]

Where:

\( q_n \) — Net pressure (kPa)
\( q_g \) — Gross pressure (kPa)
\( \sigma_s \) — Effective surcharge (kPa)

Explanation: The gross pressure is reduced by the effective surcharge to determine the net pressure that will act on the foundation.

3. Importance of Net Pressure Calculation

Details: Proper net pressure estimation ensures accurate foundation design, preventing overdesign (wasteful) or underdesign (risky).

4. Using the Calculator

Tips: Enter the gross pressure and effective surcharge in kPa. The ±5% indicates typical measurement tolerances.

5. Frequently Asked Questions (FAQ)

Q1: What is effective surcharge?
A: Effective surcharge refers to the vertical pressure or load that acts over the ground surface additional to basic earth pressure.

Q2: Why use net pressure instead of gross pressure?
A: Net pressure accounts for existing loads, giving the true additional pressure the foundation must support.

Q3: What units should I use?
A: This calculator uses kilopascals (kPa) for consistency, but you can convert from other units as needed.

Q4: How accurate is the ±5% tolerance?
A: This represents typical field measurement accuracy. For critical projects, conduct site-specific testing.

Q5: Can net pressure be negative?
A: Yes, if surcharge exceeds gross pressure, but this usually indicates an error in measurement or calculation.