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.

sigma_1 (MPa)

Major principal stress in megapascals.

sigma_3 (MPa)

Minor principal stress in megapascals.

Radius of the Mohr circle for two principal stresses: R = (sigma_1 - sigma_3) / 2, also the maximum shear stress. 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]

R (MPa)

Circle radius (maximum shear stress) in megapascals.

• Geotechnical correlations and idealized failure models depend on stratigraphy, sampling disturbance, drainage, stress history, groundwater, density, anisotropy, scale, construction sequence, and laboratory or field method. Site-specific design requires investigation and code factors.
• 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.

• Mohr Circle Center Calculator

  Center of the Mohr circle for two principal stresses: sigma_center = (sigma_1 + sigma_3) / 2 on the normal-stress axis.

• Mohr Coulomb Shear Strength Calculator

  Mohr-Coulomb shear strength tau_f = c' + sigma_n' * tan(phi') for given effective normal stress, cohesion and friction angle.

• 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.