Failure Criteria - Mohr-Coulomb Stress Components Calculator
Enter the required inputs, confirm the units, and run the calculator to solve tau. Review the formula source and assumptions before using the result in engineering work.
Calculation context and source notes
Failure Criteria - Mohr-Coulomb Stress Components calculates shear stress on the plane for in-situ stress and rock mechanics workflows in geomechanics and fracturing. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.
Use this formula when the listed inputs (sigma_a, sigma_b, beta_deg) are known and the assumptions behind the cited in-situ stress and rock mechanics relationship match the engineering case being checked.
Solves for
tau (psi)
Best next page
Formula, variables, and sourceFormula, variables, and default calculation
Reproducible default result
With the default values shown below, the calculation returns tau = 1,299.038106 psi. Defaults demonstrate the implementation; they are not recommended field values.
8000
5000
30
Input definitions
sigma_a
psiPrincipal Stress
sigma_b
psiSecond Strongest Stress
beta_deg
degAngle Between Fault and Principal Stress Direction
Output definitions
tau
Shear Stress on the Plane
sigma_n
Normal Stress on the Plane
Engineering use, assumptions, and limits
Use this formula when the listed inputs (sigma_a, sigma_b, beta_deg) are known and the assumptions behind the cited in-situ stress and rock mechanics relationship match the engineering case being checked.
Assumptions
- Input values are representative for the well, reservoir, fluid, or equipment case being evaluated.
- The declared units match the field-unit constants used in the formula.
- The cited formula applies to the selected petroleum engineering workflow.
Limitations
- The calculation does not replace a full engineering model or operating procedure.
- Accuracy depends on the source correlation, assumptions, input quality, and unit consistency.
Common mistakes
- Mixing unit systems without converting the inputs.
- Using default example values as field recommendations.
- Applying the formula outside the source assumptions.
Frequently asked questions
What inputs does the Failure Criteria - Mohr-Coulomb Stress Components calculator need?
The calculation uses Principal Stress (sigma_a), Second Strongest Stress (sigma_b), Angle Between Fault and Principal Stress Direction (beta_deg). Enter values on the units shown beside each field.
What result does this calculator return?
The primary result is shear stress on the plane in psi. The formula section shows the declared relationship, variables, and a reproducible default calculation.
What should I check before using the result?
Confirm the unit basis, source applicability, and input quality. The calculation does not replace a full engineering model or operating procedure. Mixing unit systems without converting the inputs.
Source and record status
Source metadata identifies the relationship implemented by the calculator. Check the cited edition, unit basis, and scope against the engineering case before operational use.
Zoback, M.D. 2007. Reservoir Geomechanics, Cambridge University Press, Page 89.
Open source reference