Corrections follow the standard form (N1)60 = N · CN · CE · CB · CR · CS. Consistent SI units (m, kPa, kN/m³).
Demo:
Test Parameters
Correction Factors
Auto ~80%, Safety ~60%, Donut ~45%
Length above ground level
Results
Corrected (N1)60
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blows / 0.3 m · 60% energy, 1 atm overburden
Energy-corrected N60
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blows / 0.3 m · no overburden correction
Correction factors applied
Overburden, CN
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Energy, CE
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Rod length, CR
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Borehole, CB
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Sampler, CS
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Formulation
\( (N_1)_{60} = N \cdot C_N \cdot C_E \cdot C_B \cdot C_R \cdot C_S \) and \( N_{60} = N \cdot C_E \cdot C_B \cdot C_R \cdot C_S \).\( C_N = \sqrt{P_a / \sigma'_{v0}} \le 2.0 \) (Liao & Whitman, 1986; \( P_a = 100 \) kPa), \( C_E = ER / 60 \).
\( C_R \): 0.75 for rod length < 3 m, 0.80 for 3-4 m, 0.85 for 4-6 m, 0.95 for 6-10 m, 1.00 beyond 10 m (rod length = depth + stickup).
\( \sigma'_{v0} = \gamma_{moist} \min(z, z_w) + (\gamma_{sat} - 9.81)\max(0, z - z_w) \).
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