What Is the Soil Bearing Capacity Calculator (Terzaghi)?
Soil bearing capacity is the maximum average contact pressure between a foundation footing and subgrade soil before shear rupture occurs.
How Does the Soil Bearing Capacity Calculator (Terzaghi) Work?
Calculates plastic limit equilibrium assuming Prandtl-Reissner log-spiral failure slip surfaces extending upward from footing edges.
Soil Bearing Capacity Calculator (Terzaghi) Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
Ultimate bearing capacity sums cohesion resistance, embedment overburden surcharge, and footing base width self-weight resistance.
How to Use the Soil Bearing Capacity Calculator (Terzaghi)
- Select square, strip, or circular footing geometry.
- Enter footing width B and embedment depth Df in meters.
- Input soil unit weight, cohesion c, and friction angle φ.
- Specify design Factor of Safety.
Step-by-Step Example Calculation
2m Square Footing in Silty Sand (c = 15 kPa, φ = 28°, Df = 1.5m)
Input Values:
Understanding Your Result
Allowable Bearing Capacity (q_all): Safe working pressure limit for structural column load sizing.
Ultimate Capacity (q_ult): Theoretical catastrophic shear failure threshold.
Terzaghi Factors: Dimensionless Nc, Nq, and Nγ capacity factors.
Factors That Affect the Result
- Friction angle φ has exponential impact on bearing capacity factors; footing width B linearly scales self-weight term.
When Should You Use This Calculator?
- Structural column pad footing design, foundation engineering reports, and geotechnical site assessment.
Assumptions & Limitations
- Valid for shallow foundations (Df ≤ B) in homogeneous soil with general shear failure mode.
Frequently Asked Questions
Calculation Accuracy & Reference Note
Standard classical Terzaghi shallow foundation formulation.