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.

alpha_i

Base inclination angles alpha of the slices in degrees.

W_i (kN)

Slice weights W in kilonewtons.

b (m)

Common slice width b in metres.

c' (kPa)

Effective cohesion c' in kilopascals.

phi'

Effective friction angle phi' in degrees.

ru

Pore water pressure ratio ru.

Bishop simplified method of slices with uniform slice width and pore pressure ratio ru: FS solves FS = sum[(c'b + W(1-ru)tan(phi'))/m_alpha] / sum[W sin(alpha)] with m_alpha = cos(alpha) + tan(phi')sin(alpha)/FS. 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]

FS

Factor of safety from the Bishop simplified iteration.

• 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.

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