👉SOIL BEARING CAPACITY CALCULATION
🚥Terzaghi Bearing Capacity Method – Study Note
1. What is Soil Bearing Capacity?
Soil bearing capacity is the maximum pressure that soil can safely support from a foundation without unacceptable shear failure or excessive settlement.
2. Terzaghi’s Bearing Capacity Equation
qᵤ = cN꜀ + γDᶠNq + 0.5γBNᵧ
Where:
qᵤ = ultimate bearing capacity (kN/m²)
c = soil cohesion (kN/m²)
γ = unit weight of soil (kN/m³)
Dᶠ = depth of foundation (m)
B = width of footing (m)
N꜀, Nq, Nᵧ = bearing-capacity factors, mainly dependent on the soil friction angle φ
3. Example Calculation – Square Footing
Given:
Cohesion, c = 20 kN/m²
Unit weight, γ = 18 kN/m³
Foundation depth, Dᶠ = 1.5 m
Footing width, B = 2.0 m
Angle of internal friction, φ = 30°
Factor of Safety = 3
For φ = 30° (illustrative values): N꜀ = 30.14, Nq = 18.40, Nᵧ = 16.02
For a square footing:
qᵤ = 1.3cN꜀ + γDᶠNq + 0.4γBNᵧ
qᵤ = 1.3(20)(30.14) + (18)(1.5)(18.40) + 0.4(18)(2.0)(16.02)
qᵤ = 783.64 + 496.80 + 230.38
qᵤ ≈ 1,510.82 kN/m²
4. Allowable Bearing Capacity
Allowable bearing capacity is obtained by applying an appropriate factor of safety:
qₐₗₗ = qᵤ / F.S.
qₐₗₗ = 1,510.82 / 3 ≈ 503.61 kN/m²
Allowable bearing capacity ≈ 504 kN/m²
5. Important Points
Use soil properties obtained from a proper geotechnical investigation.
Bearing-capacity factors depend on the soil friction angle φ and the selected theory.
Footing shape affects the bearing-capacity equation through shape factors.
A suitable factor of safety must be selected according to the applicable design code and project requirements.
Bearing capacity and settlement are separate checks; both must be considered in foundation design.
Groundwater conditions, foundation depth, eccentricity, inclination, and nearby loads may affect the final design.
6. Design Reminder
The numerical example is for educational illustration. Actual foundation design should be based on site-specific soil investigation, structural loads, groundwater conditions, settlement analysis, and the applicable foundation design code.
👉መሰረታዊ የ ፋውንዴሽን ኢንጅነሪንግ የምትስረዳ ምርጥ መፅሐፍ ከታች ባለው ሊንክ ያውርዱ👇
🌟Foundation Engineering Fundamentals – Complete Introductory Ebook
https://ye-buna.com/etconp?ref=product_detail&product=6a8743a519501_etconp
🚥Terzaghi Bearing Capacity Method – Study Note
1. What is Soil Bearing Capacity?
Soil bearing capacity is the maximum pressure that soil can safely support from a foundation without unacceptable shear failure or excessive settlement.
2. Terzaghi’s Bearing Capacity Equation
qᵤ = cN꜀ + γDᶠNq + 0.5γBNᵧ
Where:
qᵤ = ultimate bearing capacity (kN/m²)
c = soil cohesion (kN/m²)
γ = unit weight of soil (kN/m³)
Dᶠ = depth of foundation (m)
B = width of footing (m)
N꜀, Nq, Nᵧ = bearing-capacity factors, mainly dependent on the soil friction angle φ
3. Example Calculation – Square Footing
Given:
Cohesion, c = 20 kN/m²
Unit weight, γ = 18 kN/m³
Foundation depth, Dᶠ = 1.5 m
Footing width, B = 2.0 m
Angle of internal friction, φ = 30°
Factor of Safety = 3
For φ = 30° (illustrative values): N꜀ = 30.14, Nq = 18.40, Nᵧ = 16.02
For a square footing:
qᵤ = 1.3cN꜀ + γDᶠNq + 0.4γBNᵧ
qᵤ = 1.3(20)(30.14) + (18)(1.5)(18.40) + 0.4(18)(2.0)(16.02)
qᵤ = 783.64 + 496.80 + 230.38
qᵤ ≈ 1,510.82 kN/m²
4. Allowable Bearing Capacity
Allowable bearing capacity is obtained by applying an appropriate factor of safety:
qₐₗₗ = qᵤ / F.S.
qₐₗₗ = 1,510.82 / 3 ≈ 503.61 kN/m²
Allowable bearing capacity ≈ 504 kN/m²
5. Important Points
Use soil properties obtained from a proper geotechnical investigation.
Bearing-capacity factors depend on the soil friction angle φ and the selected theory.
Footing shape affects the bearing-capacity equation through shape factors.
A suitable factor of safety must be selected according to the applicable design code and project requirements.
Bearing capacity and settlement are separate checks; both must be considered in foundation design.
Groundwater conditions, foundation depth, eccentricity, inclination, and nearby loads may affect the final design.
6. Design Reminder
The numerical example is for educational illustration. Actual foundation design should be based on site-specific soil investigation, structural loads, groundwater conditions, settlement analysis, and the applicable foundation design code.
👉መሰረታዊ የ ፋውንዴሽን ኢንጅነሪንግ የምትስረዳ ምርጥ መፅሐፍ ከታች ባለው ሊንክ ያውርዱ👇
🌟Foundation Engineering Fundamentals – Complete Introductory Ebook
https://ye-buna.com/etconp?ref=product_detail&product=6a8743a519501_etconp
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