Barton-Bandis Rock Joint Shear Calculator
Rock mechanics & rock slope stability: Model non-linear shear strength, asperity override, dilation angle, and field scale corrections ($JRC_n, JCS_n$) per the Barton-Bandis criterion.
Laboratory Joint Measurements ($L_0 = 100$ mm)
Barton-Bandis Strength & Dilation Results
Peak Shear Strength $\tau_p$
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MPa (asperity interlock)
Peak Friction Angle $\phi_p$
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degrees (total friction)
Peak Dilation Angle $d_n$
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degrees (asperity override)
Scaled Field $JRC_n$
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Block roughness
Scaled Field $JCS_n$
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MPa (wall strength)
Residual Strength $\tau_r$
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MPa ($\sigma_n \tan \phi_b$)
Shear Strength vs Normal Stress Envelope
At low normal stresses, asperities ride over each other ($d_n > 0$, high dilation). At elevated normal stresses, asperities are sheared through, and $\phi_p \to \phi_b$.
Barton-Bandis Mechanics & Scale Effects
The empirical shear strength criterion developed by Barton (1973, 1976) and Bandis et al. (1981) accurately predicts the shear resistance of unfilled rock joints:
$$\tau_p = \sigma_n \tan \left[ JRC \log_{10}\left( \frac{JCS}{\sigma_n} \right) + \phi_b \right]$$
$$JRC_n = JRC_0 \left( \frac{L_n}{L_0} \right)^{-0.02 JRC_0}, \quad JCS_n = JCS_0 \left( \frac{L_n}{L_0} \right)^{-0.03 JRC_0}$$
Scale effects are pronounced: larger in-situ rock blocks exhibit lower effective roughness $JRC_n$ and lower wall strength $JCS_n$ because shear displacements mobilize longer wavelength, gentler asperities.
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