Shallow Foundation Bearing Capacity
General Bearing Capacity Equation (Meyerhof/Vesic)
Ultimate Capacity
Ultimate Bearing (qu)
0.0 kPa
Design Capacity
Net Allowable (qnet(all))
0.0 kPa
Max Safe Column Load
0.0 kN
Based on Area = 0 m²
Governing Component
Cohesion: 0%
Surcharge: 0%
Friction: 0%
Foundation & Soil Failure Mechanism Schematics
Plan & Cross-Section Views
Plan View
Cross-Section
Parametric Sizing: Capacity vs. Footing Width ($B$)
Calculation Factors Breakdown
| Factor Type | Cohesion ($c$) | Surcharge ($q$) | Friction ($\gamma$) |
|---|---|---|---|
| Bearing ($N$) | 0.0 | 0.0 | 0.0 |
| Shape ($s$) | 0.0 | 0.0 | 0.0 |
| Depth ($d$) | 0.0 | 0.0 | 0.0 |
| Comp. Stress ($q$) | 0.0 | 0.0 | 0.0 |
Effective Surcharge Stress ($q$):0.0 kPa
Effective Wedge Unit Wt ($\gamma_{eff}$):0.0 kN/m³
Geotechnical Theory
1. The General Bearing Capacity Equation
This tool utilizes the generalized formulation developed by Meyerhof, Hansen, and Vesic to account for footing shape and embedment depth beyond Terzaghi's original simplified equation.
$$q_u = c' N_c s_c d_c + q N_q s_q d_q + \frac{1}{2} \gamma_{eff} B N_\gamma s_\gamma d_\gamma$$
2. Bearing Capacity Factors
Based on the effective friction angle ($\phi'$), using Prandtl-Reissner and Vesic definitions:
$$N_q = \tan^2\left(45^\circ + \frac{\phi'}{2}\right) e^{\pi \tan \phi'}$$
$$N_c = (N_q - 1) \cot \phi'$$
$$N_\gamma = 2(N_q + 1) \tan \phi'$$
3. Groundwater Table Corrections
Water reduces the effective stress of the soil, significantly lowering bearing capacity. The unit weight of water ($\gamma_w$) is assumed as $9.81 \text{ kN/m}^3$ (or $62.4 \text{ pcf}$).
- $D_w \le D_f$: Water is above the footing. Surcharge $q$ is reduced. The wedge soil is fully submerged ($\gamma' = \gamma - \gamma_w$).
- $D_f < D_w < D_f + B$: Water intersects the failure wedge. An interpolated effective unit weight ($\gamma_{eff}$) is applied to the third term.
- $D_w \ge D_f + B$: Water is too deep to affect the failure wedge. Full bulk unit weight $\gamma$ is used.
Standard Geotechnical Reference Tables
Typical Soil Parameters
| Soil Description | Friction φ' (°) | Cohesion c' (kPa) | γ (kN/m³) |
|---|---|---|---|
| Loose Sand / Gravel | 28 - 30 | 0 | 14 - 16 |
| Med Dense Sand / Gravel | 32 - 36 | 0 | 17 - 19 |
| Dense Sand / Gravel | 36 - 40+ | 0 | 19 - 22 |
| Soft Clay | 0* | 10 - 25 | 14 - 17 |
| Medium Clay | 0* | 25 - 50 | 17 - 19 |
| Stiff / Hard Clay | 0* | 50 - 100+ | 19 - 21 |
* For Undrained (Short-Term) total stress analysis. Drained clay has $\phi' > 0$ and $c' \approx 0$.
Presumptive Allowable Bearing (IBC)
| Material Type | Metric (kPa) | Imp (psf) |
|---|---|---|
| Crystalline Bedrock | 600 | 12,000 |
| Sedimentary / Foliated Rock | 200 | 4,000 |
| Sandy Gravel / Gravel | 150 | 3,000 |
| Sand / Silty Sand | 100 | 2,000 |
| Clay / Sandy Clay / Silt | 75 | 1,500 |
Recommended Min. Factor of Safety (FS)
| Structure / Condition | Typical FS |
|---|---|
| Typical Buildings & Bridges | 3.0 |
| Retaining Walls (Bearing) | 3.0 |
| Temporary Structures | 2.0 |
| Extreme Loads (Earthquake/Wind) | 1.5 - 2.0 |
References
- Meyerhof, G. G. (1963). Some recent research on the bearing capacity of foundations. Canadian Geotechnical Journal, 1(1), 16-26. Google Scholar
- Vesic, A. S. (1973). Analysis of ultimate loads of shallow foundations. Journal of the Soil Mechanics and Foundations Division, 99(1), 45-73. Google Scholar
- Das, B. M. (2010). Principles of Geotechnical Engineering (7th ed.). Cengage Learning. Google Scholar
- International Code Council (ICC). (2018). International Building Code (IBC) - Chapter 18: Soils and Foundations. ICC Safe
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