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Soil Bearing Capacity Calculator
Calculate ultimate and safe bearing capacity of soil using Terzaghi, Meyerhof, and Hansen methods with shape and depth factors.
Foundation Engineering Geotechnical engineers, structural engineers Commercial Intent: HIGH
Engineering Formulas
Terzaghi Bearing Capacity Equation
qult = c × Nc × sc + q × Nq + 0.5 × γ × B × N_γ × s_γ
q_ult: Ultimate bearing capacity (kPa)
c: Cohesion (kPa)
q: Overburden pressure = γ × Df (kPa)
γ: Unit weight of soil (kN/m³)
B: Footing width (m)
N_c, N_q, N_γ: Bearing capacity factors (function of φ)
s_c, s_γ: Shape factors
Worked Example
Square Footing in Dense Sand
soilType: sand-densecohesion: 0phi: 40gamma: 20width: 2length: 2depth: 1.5shape: square
Bearing Factors
Nq = 64.2, Nc = 0 (c=0), Nγ = 109.4
Overburden
q = 20 × 1.5 = 30 kPa
Shape Factors
sc = 1.3, sγ = 0.8 (square)
Ultimate Capacity
qu = 0 + 30 × 64.2 + 0.5 × 20 × 2 × 109.4 × 0.8 = 3,678 kPa
Safe Capacity
qs = 3,678 / 3 = 1,226 kPa
Result: qu = 3,678 kPa, qs = 1,226 kPa — suitable for most structures
Engineering Notes
Always verify soil parameters with laboratory or field tests.
For water table correction, adjust unit weight when water table is within B of footing base.
Consider settlement criteria in addition to bearing capacity.
Assumptions
• Soil is homogeneous and isotropic
• Failure occurs by general shear
• Footing is rigid and at shallow depth (Df ≤ B)
Common Mistakes
✕ Using Terzaghi factors for deep foundations
✕ Ignoring ground water table effects
✕ Not distinguishing between strip, square, and circular footings
Frequently Asked Questions
What is the difference between ultimate and safe bearing capacity?
Ultimate bearing capacity (qu) is the maximum pressure the soil can support before failure. Safe bearing capacity (qs) is qu divided by a factor of safety (typically 3).
Which method should I use?
Terzaghi is suitable for shallow foundations. Meyerhof and Hansen include additional correction factors for shape, depth, and inclination.
What is a typical factor of safety for bearing capacity?
A factor of safety of 3 is commonly used for bearing capacity calculations. This accounts for uncertainties in soil parameters, loading conditions, and analysis methods.
References & Standards
Terzaghi (1943)IS 6403ACI 318
Terzaghi (1943)
Theoretical Soil Mechanics — original bearing capacity theory
IS 6403
Code of Practice for Bearing Capacity of Shallow Foundations
ACI 318
Foundation design requirements