// multi-utility computation suite · offline · instant · precise
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sci.rock-strength-Hoek-Brown Calculator
Calculates Hoek-Brown failure criterion for intact rock and rock masses: σ₁ = σ₃ + σci(mb×σ₃/σci + s)^a. GSI (Geological Strength Index) links RMR to Hoek-Brown parameters mb and s — hard intact rock (GSI = 100, mi = 25) has mb = 25, s = 1; heavily jointed rock (GSI = 30) has mb ≈ 1, s ≈ 0.
Inputs
Sigma3 Mpa
Internal force per unit area (Pa or MPa). Must stay below yield strength in service.
Ucs Mpa
Reference formula or conversion factor shown for context.
Mi Constant
Reference formula or conversion factor shown for context.
Gsi
Reference formula or conversion factor shown for context.
Results
major principal stress at failure σ₁ (MPa)
Internal force per unit area (Pa or MPa). Must stay below yield strength in service. Beyond yield: permanent deformation. Beyond tensile strength: fracture.
m_b (rock mass constant)
The computed mass of the object or substance.
s parameter
Reference formula or conversion factor shown for context.
σ₁ = σ₃ + σci(mb·σ₃/σci + s)^a
Reference formula or conversion factor shown for context.
quality
A qualitative assessment of how the result compares to the desired standard or benchmark.