SPT N-Value Correction Tool
Calculator for correcting Standard Penetration Test (SPT) N-values considering: Hammer Energy Correction, Overburden Pressure Correction, and Dilatancy Correction.
Input Parameters
Important:
Dilatancy correction is applied only for saturated fine sand and silt when corrected N-value exceeds 15.
Dilatancy correction is applied only for saturated fine sand and silt when corrected N-value exceeds 15.
Equations Used
1. Energy CorrectionN₆₀ = (Eactual / 60) × N
2. Overburden Correction Factor
Cₙ = 0.77 × log₁₀(2000 / σ′₀)
0.40 ≤ Cₙ ≤ 2.00
3. Overburden Corrected Value
(N₁)₆₀ = Cₙ × N₆₀
4. Dilatancy Correction
N' = 15 + 0.5[(N₁)₆₀ − 15]
Results & Dynamic Visualization
Corrected Results
Energy Corrected N₆₀
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Correction Factor Cₙ
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Overburden Corrected (N₁)₆₀
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Final Corrected N
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Energy Correction
SPT N-values vary with hammer efficiency. Therefore, measured values are standardized to 60% hammer energy.
- Donut Hammer → 45%
- Safety Hammer → 60%
- Automatic Hammer → 70–80%
Overburden Correction
Effective confinement pressure affects penetration resistance.
- Low σ′₀ → Low resistance
- High σ′₀ → Higher resistance
- Correction normalizes field values
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| SPT Correction Tool as per IS-2131-2025 |
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