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Modeling: Analysis Methods
In RocPlane, stability can be assessed using either Deterministic (safety factor) or Probabilistic (probability of failure) analysis methods.
The Analysis Type can be changed in the Project Settings dialogue
For a Deterministic analysis, RocPlane computes the factor of safety for a wedge of known input parameters. For a Probabilistic analysis, statistical data can be entered to account for uncertainty in input parameters (orientation, strength, water and external forces). This results in a safety factor distribution, from which a probability of failure is calculated. In addition to Deterministic and Probabilistic analyses, a Sensitivity Analysis can also be performed. This allows the user to study the effect of individual variables on the safety factor of the wedge, by automatically varying one variable at a time, while keeping other variables constant.
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Modeling: Graphical Data Entry/Editing
RocPlane gives the flexibility in defining the slope angle, tension crack angle, and distance of tension crack from crest. A great many different wedge shapes can be analyzed in RocPlane. Diagrams are provided to help the user visualize the geometry of the wedge when entering required parameters in the Input Data Dialogue.
Deterministic Input Data Dialogue
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Modeling: Tension Crack
In RocPlane, a tension crack is optional and does not have to be vertical. The tension crack can be checked and the tension crack angle and the distance from the slope crest to the crack can be specified in the Input Data dialogue.
The minimization process uses Brent's algorithm to determine the distance of the tension crack from the crest of the slope that yields the minimum factor of safety. If the position of the tension crack is known from field studies then it also possible to fix this location by entering a user defined distance from the crest.
The following figure depicts a wedge with a user defined tension crack position located 15m from the slope crest and a tension crack angle of 70 degrees. All angles and dimensions can be seen on this 2D view. Both 2D and the above 3D view can be used to easily visualize the geometry.
If the tension crack angle is unknown and you wish to look at how the orientation of the tension crack affects the factor of safety, it is a simple matter of doing a sensitivity analysis on the tension crack angle. The following figure plots sensitivity of the factor of safety to the tension crack angle by varying it between 70 and 110 degrees.
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Modeling: Upper Slope Face
In RocPlane, an upper ground surface does not have to be present and horizontal. The upper slope face can be defined at any angles.
Upper slope face can have any orientation (doesn't have to be horizontal)
Normally, the wedge size determined by RocPlane is based on the Slope Height. If desired, the user can scale the wedge size according to a Bench Width, by selecting the Bench Analysis checkbox and entering a value. This option is useful for bench analyses in open pits.
Bench Analysis. Limit the wedge size by a bench width.
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Modeling: Strength Models
RocPlane contains 5 different strength models that can be used to define the shear strength along the failure surface. The parameters associated with any of the models is entered through a simple dialog:
As seen above, the supported strength models are 1) Mohr-Coulomb, 2) Barton-Bandis, 3) Hoek-Brown, 4) Generalized Hoek-Brown and 5) Power Curve. The following figures depict each of the models and the required input.
Mohr-Coulomb
Barton-Bandis
Hoek-Brown
Generalized Hoek-Brown
Power Curve
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Modeling: Waviness
In RocPlane, waviness is an optional parameter that can be included in calculations of the shear strength of the failure plane, for any of the strength models. It accounts for the waviness (undulations) of the failure plane surface, observed over distances on the order of 1 m to 10 m. Waviness is specified as the average dip of the failure plane, minus the minimum dip of the failure plane. A non-zero waviness angle, will always increase the effective shear strength of the failure plane.
Waviness specification in the Data Input Dialog:
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Modeling: Different Water Pressure Distributions
RocPlane contains 4 different water pressure distributions that can be used to define the water level in the slope. The parameters associated with any of the models is entered through a simple dialog:
As seen above, the supported water pressure models are 1) Peak Pressure - Mid Height, 2) Peak Pressure - Toe, 3) Peak Pressure - TC Base and 4) Custom Pressure. The following figures depict each of the models and the required input.
| Peak Pressure - Mid Height |
Peak Pressure - Toe |
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| Peak Pressure - TC Base |
Custom Pressure |
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Modeling: Seismic Force
RocPlane lets the user add a seismic force component to the sliding slope by specifying the seismic coefficient and the slope angle.
Select the orientation of the seismic force
Horizontal seismic force
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User defined seismic force direction
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Modeling: Multiple External Forces
External Forces (e.g. a structural load on the upper surface of a slope, or the force applied by a waste rock berm to the toe of a slope) can be applied to the sliding block, with the External Forces option in the Input Data dialog.
Specify the number of external forces and the individual orientations and magnitudes in the data input dialog
External forces (purple arrows) are shown separately in the 3D wedge view
External forces are shown as a single resultant force (dark green arrow) in the 2D wedge view (specific force orientations and magnitudes are listed in a table)
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Modeling: Bolt Reinforcement
Placements of bolts in RocPlane is simple. Bolts are added individually to a wedge model by moving the cursor into the Top or Front orthogonal views. As shown in the Bolt Property Dialog, bolts in RocPlane contain the following features:
Simple placement
Define load capacity and length for each bolt - The bolt capacity is entered
as a force per distance, taking account of the spacing of the bolts in the
out-of-plane direction.
Optimize orientation of rockbolts
Calculation of bolt capacity for a specified factor of safety
Active or passive bolt models
Instant calculation of safety after after addition of reinforcement
Simple addition / deletion / modification of individual rockbolts
Bolt Properties Dialog
Automatic new safety factor computation
Add / delete / modify individual rockbolts
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Modeling: Metric and Imperial Units
RocPlane allows the user to work under either Metric or Imperial system. All data entries and calculations will change accordingly once the unit system is switched in the Project Setting Dialog Box.
Project Setting Dialog Box
The unit system is changed automatically in the data input dialog
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