model factor-of-safety command
Syntax
- model factor-of-safety <keyword ...>
Primary keywords:
associated block-zone bracket bracket-limit characteristic-steps convergence filename interface joint list perturbation ratio ratio-average ratio-local ratio-maximum resolution step-limit zone zone-joint
Set factor of safety analysis parameters. See the section Factor of Safety for a complete description. Note only FLAC and 3DEC calculate factor of safety; this calculation is not available in PFC. The following keywords apply.
- associated
Apply associated flow rule. The dilation angle is set equal to the friction angle, as modified by the factor of safety procedure. (By default, the nonassociated flow applies.) Note that even in a nonassociated flow rule, the dilation is not allowed to become greater than the friction.
- block-zone keyword (3DEC)
Specify which 3DEC zone properties to change during analysis. The user may include or exclude specific zone properties from the list. By default the list of properties being included is friction, cohesion, joint-cohesion, and joint-friction (the last two referring to ubiquitous joint strength properties).
- bracket f1 f2
Set two starting bracket values. Factor of safety calculation stops with a warning message issued if it turns out that the factor of safety falls outside of the specified brackets. If f1 = f2, FLAC3D tests one value for stability.
- bracket-limit f
Set the maximum mount the target factor of safety can change during factor of safety bracketing. For example, if the current factor of safety limits were 1 for stable and 2 was just calculated as unstable the next factor of safety trial would be at 1.5. But if the bracket-limit had been set to 0.05 the next trial factor of safety would be 1.95 – in the same direction as 1.5 but a maximum of 0.05 away from the last value.
This keyword is useful if the goal is to generate factor of safety contours, as it guarantees a maximum spread between values taken during bracketing.
- characteristic-steps i
Set the characteristic response steps. If not specified, i is tested using the existing perturbation method.
- convergence f
Specifies the convergence value used to determine equilibrium. See the discussion of ratio options in Convergence Criteria (in FLAC3D documentation). The default value is 0.
- filename s
Sets the file name prefix used to identify save files created during the factor of safety calculation. Three files will be created during the process. For example, if the prefix given was test, then the filenames test-Init.f3sav, test-Stable.f3sav, and test-Unstable.f3sav will be created. These files represent the initial state, the last stable state, and the last unstable state, respectively.
- interface (FLAC)
Specify which interface properties to change during analysis. The user may include or exclude specific interface properties from the list. All interfaces properties are excluded by default. Note that factor of safety calculations in large strain mode are not supported if interfaces are present.
- joint
Specify which joint properties to change during analysis. This refers for zone joints in FLAC2D and FLAC3D or joints in 3DEC. The user may include or exclude specific joint properties from the list. By default, in 3DEC the list of properties being included is cohesion and friction. By default, in FLAC2D and FLAC3D all zone joint properties are excluded.
- list
Display the last factor of safety result.
- perturbation f
Set the stress perturbation factor. This is used in determining the characteristic response steps, by perturbing the model from its current (assumed) equilibrium state by adjusting the stress field and not allowing failure. The default factor is 2.0.
- ratio f
Specify the unbalanced force ratio used to determine equilibrium. If this is not explicitly set, the program uses the current value used by the previous
model solvecommand. The default is 1e-5.
- ratio-average f
Specify the unbalanced force ratio used to determine equilibrium, and that the average ratio be used. See the discussion of ratio options in Convergence Criteria (in FLAC3D documentation).
- ratio-local f
Specify the unbalanced force ratio used to determine equilibrium, and that the local ratio be used. See the discussion of ratio options in Convergence Criteria (in FLAC3D documentation).
- ratio-maximum f
Specify the unbalanced force ratio used to determine equilibrium, and that the maximum ratio be used. See the discussion of ratio options in Convergence Criteria (in FLAC3D documentation).
- resolution f
Set the resolution in comparing two bracketing (stable and unstable) factors. The default is .005 × the mean value. Once the gap between the known stable and unstable factors is less than this value, the factor of safety calculation will end.
- step-limit i
Set a limit on the number of characteristic steps allowed. If the characteristic steps would be above this limit the check is halted and this value is used. The default value is 50,000.
- zone keyword (FLAC3D)
Specify which zone properties to change during analysis. The user may include or exclude specific zone properties from the list. By default the list of properties being included is friction, cohesion, joint-cohesion, and joint-friction.
- zone-joint keyword (FLAC)
Specify which zone-joint properties to change during analysis. The user may include or exclude specific interface properties from the list. All zone-joint properties are excluded by default. To include or exclude more than one property, repeat the keyword, e.g. model factor-of-safety zone-joint include 'friction' include 'cohesion'
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