1. What is Unit Weight of Soil?

Definition: Unit weight (γ) represents the weight per unit volume of soil, typically expressed in kN/m³ in geotechnical engineering.

Purpose: It's a fundamental property used in calculating stresses in soil, bearing capacity, and slope stability analysis.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( \gamma \) — Unit weight (kN/m³)
• \( \rho \) — Density of soil (kg/m³)
• \( g \) — Acceleration due to gravity (9.81 m/s²)

Explanation: The density is multiplied by gravity and divided by 1000 to convert from N/m³ to kN/m³.

3. Importance of Unit Weight

Details: Unit weight is crucial for:

• Calculating overburden pressure
• Designing foundations and retaining walls
• Assessing slope stability
• Estimating earthwork quantities

4. Using the Calculator

Tips:

• Enter soil density in kg/m³ (typical range 1500-2000 kg/m³)
• Gravity is typically 9.81 m/s² (Earth's standard)
• All values must be > 0

5. Frequently Asked Questions (FAQ)

Q1: What's the typical unit weight of soil?
A: Most soils range between 15-20 kN/m³, with sands around 16-18 kN/m³ and clays 17-20 kN/m³.

Q2: Why use kN/m³ instead of kg/m³?
A: kN/m³ is preferred in geotechnical engineering as it directly relates to stress calculations (kPa = kN/m²).

Q3: How does moisture affect unit weight?
A: Wet soils have higher unit weight due to water content, while saturated soils may approach 22 kN/m³.

Q4: What's the difference between density and unit weight?
A: Density (ρ) is mass per volume (kg/m³), while unit weight (γ) is force per volume (kN/m³), related by γ = ρ × g.

Q5: How do I measure soil density?
A: Use field tests like sand cone or nuclear density gauge, or lab tests on undisturbed samples.