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Hoek-Brown Intact Rock Triaxial Failure Criterion Calculator

Evert Hoek and E. T. Brown developed an empirical failure criterion tailored to the non-linear parabolic strength of rock under confinement.

Triaxial confinement cell pressure

Uniaxial compressive strength (UCS)

Lithology constant (Limestone ~ 12, Granite ~ 32)

Calculated Result
157 MPa

Peak Major Principal Stress (σ1)

Deviatoric Strength (σ1 - σ3)

147 MPa

Calculation Breakdown

  1. Hoek-Brown Intact Criterionσ1 = σ3 + σci·√(mi·σ3/σci + 1) => 157 MPa

Failure Stress vs Confinement

Interactive visualization based on your current inputs

σ1
0.0601201802400 MPa (UCS)10 MPa25 MPaConfining σ3 (MPa)Peak σ1 (MPa)

What Is the Hoek-Brown Intact Rock Triaxial Failure Criterion Calculator?

Evert Hoek and E. T. Brown developed an empirical failure criterion tailored to the non-linear parabolic strength of rock under confinement.

Unlike linear Mohr-Coulomb models, Hoek-Brown accurately captures curvature in the rock failure envelope at elevated pressures.

How Does the Hoek-Brown Intact Rock Triaxial Failure Criterion Calculator Work?

The calculation evaluates user-provided measurements using recognized domain equations, converts between measurement units, and adjusts for real-world efficiency factors.

Hoek-Brown Intact Rock Triaxial Failure Criterion Calculator Formula & Variables

The core mathematical equation utilized by this calculator is expressed as:

\sigma_1 = \sigma_3 + \sigma_{ci} \sqrt{m_i \frac{\sigma_3}{\sigma_{ci}} + 1}

Hoek-Brown intact rock failure criterion.

How to Use the Hoek-Brown Intact Rock Triaxial Failure Criterion Calculator

  1. Enter your primary measurements in the input fields above.
  2. Select your preferred units (e.g. metric or imperial) if applicable.
  3. Review or adjust operational assumptions such as field efficiency.
  4. Click Calculate to instantly generate the full results breakdown and visual chart.
  5. Use the Reset button at any time to clear the form and test a new scenario.

Step-by-Step Example Calculation

Granite Triaxial Core Test

Input Values:

minorPrincipalStressSigma3Mpa:20.0
unconfinedStrengthSigmaCiMpa:140.0
hoekBrownConstantMi:30.0

Understanding Your Result

Your calculated result represents the realistic operational capacity or baseline output under the specified conditions. Comparing theoretical and effective outputs reveals the direct impact of turns, overlap, and practical downtime.

Factors That Affect the Result

Field terrain, operator experience, equipment maintenance, overlap margin, and weather conditions can significantly influence real-world output.

When Should You Use This Calculator?

Use this calculator whenever you need quick, verified estimates for job planning, budgeting, equipment sizing, or project timelines.

Assumptions & Limitations

  • Applies strictly to intact laboratory core specimens before rock mass scaling.

Frequently Asked Questions

Calculation Accuracy & Reference Note

This calculator implements verified, deterministic mathematical equations based on published standards. Results should be treated as professional engineering estimates; always verify critical operations with local equipment manuals and site inspections.

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