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_n' (kPa)

Effective normal stress on the failure plane in kilopascals.

c' (kPa)

Effective cohesion c' in kilopascals.

phi'

Effective friction angle phi' in degrees.

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

tau_f (kPa)

Shear strength at failure in kilopascals.

• 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.

• Earth Pressure At Rest Calculator

  At-rest lateral earth pressure for a normally consolidated soil via Jaky K0 = 1 - sin(phi): horizontal effective stress sigma_h' = K0 * sigma_v'. Stress in kPa, angle in degrees.

• 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 Circle Radius Calculator

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