If σ0' and σ' represent initial and increased pressure ; e0 and e void ratios corresponding to initial and increased pressure ; and C0 the compression index (dimensionless), then, the virgin compression curve as expressed by Terzaghi empirical formula is

• e = e0 + Cc log10 σ'/σ0'
• e = e0 - Cc log10 σ'/σ0'
• e0 = e - Cc log10 σ'/σ0'
• e0 = e + Cc log10 σ0'/σ'