Use this geological calculation for a transparent first-pass interpretation of measured rock, soil, fluid, well, stratigraphic, isotopic, geophysical, or seismic data under an explicitly selected model.

e1

Void ratio e1 at the start of the reload increment.

e2

Void ratio e2 at the end of the reload increment.

sigma1'

Effective vertical stress sigma1' in kPa.

sigma2'

Effective vertical stress sigma2' in kPa.

Recompression (swell/reload) index Cr = Cs = (e1 - e2) / log10(sigma2' / sigma1') measured on an unload-reload loop of an oedometer test. Void ratios dimensionless, effective stresses in kPa. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Cr

Recompression index Cr (dimensionless).

• Geological models are scale-, site-, method-, and calibration-dependent. Heterogeneity, anisotropy, sampling, diagenesis, pressure-temperature history, instrument response, boundary conditions, and empirical-correlation range can dominate the result.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Compare independent measurements and models, retain units and analytical metadata, propagate uncertainty, and validate interpretations against logs, cores, maps, laboratory data, or field observations.

• Compression Index Calculator

  Compression index Cc = -(de) / d(log10 sigma') = (e1 - e2) / log10(sigma2' / sigma1') from two points on the virgin consolidation curve. Void ratios dimensionless, effective stresses in kPa.

• Modulus Of Volume Compressibility Calculator

  Oedometric (constrained) modulus E_oed = (1 + e0) * d_sigma' / de = 1 / mv from a consolidation loading increment. Void ratios dimensionless, stresses in kPa.

• Preconsolidation Pressure Calculator

  Maximum past effective vertical stress sigma_p' = OCR * sigma_v0' from the definition of the overconsolidation ratio. Stresses in kPa; use a Casagrande construction on the oedometer curve for direct measurement.