Design Bench Pit

This command creates pits where the sides are a series of slopes with benches. The side slopes start from a closed polyline. This pit polyline can be either the bottom of the pit and the slopes run up and out to intersect the ground surface, or the pit polyline can represent the top of the pit and the slopes run down and in, to intersect the pit bottom grid. Different slopes can be used for different sides of the pit. The pit is drawn as 3D polylines and the pit volumes are reported.

Before starting this command, the pit perimeter should be drawn as a closed polyline, 2D at zero elevation, or at 3D elevations on a surface. The program also needs triangulation or grid files for the existing ground surface and the bottom of pit surface. Design Bench Pit starts with the dialog shown below to specify these grid file names.

• Ground Surface: This is the surface for the top of pit perimeter.
  
• Pit Bottom Surface: This is the surface that will represent the bottom of the pit.
• Pit Bottom Surface By: This option chooses between using a surface model or fixed Elevation for the target for the bottom of the pit.
• Write Bench Solids: This option creates solid model files (.MDL) for the volume of each bench in the design.
• Report Volumes: You can turn off this option to save processing time if you don't need this routine to report the pit earthworks.
  
• Write Surface History File: This output file is a GSQ file that is used for volumes in Surface Mine Reserves which leads up to surface mine timing and scheduling on these volumes, or for 3D Viewing as a movie with View Surface History File command.
  
• Round Exterior Corners: This option will create rounded corners on the outside edges of the pit for a more realistic design. When this is off, the corners are sharp and angular. 
• Write Output Grid File: This option will create a grid file (GRD) of the design. It includes the original ground surface grid file, with the pits built onto it.
  
• Use Elevations From Pit 3D Polyline: This will use the elevations on the polyline as the start of the design. It will start the pits at the elevations the polylines are drawn at instead of starting at the Pit Bottom Grid for going up, or the topography when going down.
• Force Bench with Width and Max Depth: This option applies when the Slope Method is in Projection mode. This option creates the bench up to the specified Max Depth beyond the target surface.
  
• Process Multiple Polylines by Pit Names: This option is to process multiple pit perimeter polylines all at once. The pit polylines must have pit/site names assigned and the program will process them in the order of their pit names. As each pit polyline is processed, the ground surface is updated with the pit volume removed. Then the next pit will use this updated ground surface. When Process Multiple is active, the Sequence Method choose the way to order the pits for processing. The Pit Name method processes the pits in alphabetical order. The Timing File method uses the pit assignment order from Surface Equipment Timing from the .TIM file.
  
• Separate Layers by Pit Names: This option puts the 3D polyline break lines of each pit on their own separate layer. It takes the Pit Layer, and increments them by -2, -3 etc.
  
• Create Road: This option carves a rough road into the pit design. In the dialog, the road Direction, Road Width and Road Slope % are specified along with a Road Color for the road polylines to create. When this option is active, the program will prompt for a road starting point along the pit perimeter. The cut slopes are shifted to make room for the road. The Bench Stop Distance is for suspending the bench as it crosses the road to avoid combining the road and bench widths at the crossing which tends to shift the cut slopes too much. Within the Bench Stop Distance, the bench has a zero width. The Bench Stop is centered at the road crossing. The Bench Taper to the distance that the bench transitions from full width to zero at the Bench Stop. The Berm Height adds a berm and makes the road wider to fit the berm. The slope of the berm is set by the Berm Slope.
  

• Slope Direction: Up will start at the pit bottom and bench up and out to the surface topography. Down will start at the top surface, and bench down and in to the pit bottom.
  
• Slope Method: Projection is a method that projects the 3D polylines down the slope, across the benches. Offset is a method that offsets the horizontal "toe and crest" lines to create the pit shells this way. Both methods will have horizontal and vertical breaklines, but the method they are generated is different. Each method has its benefits and might work better than the other for each unique scenario. If there is a problem with one method, try the other to see if it handles it better.
  
• Horizontal & Vertical Interval: These settings control the distance to draw the 3D breakline polylines. The horizontal interval will run down the slope, and across the bench. The vertical interval will run parallel with the benches. It should be a factor of the bench height if possible, but not required. 
• Min Bench Height: The bench is not created when the side slope depth is less than the specified amount.
  
• Side Layer: This is the layer of the 3D polylines drawn perpendicular to the benches, and running down slope.
  
• Pit Layer: This layer is applied to the 3D polyline break lines running parallel to the benches.
  
• Use Bench Name for Layer Suffix: This option adds the bench name to the Pit Layer so that each bench can have a unique name which can be useful for having different colors for each bench for visualization or for isolating benches by layer.
  
• Draw Side Slope Polylines: This option chooses whether to draw the 3D polylines running perpendicular to the benches, and down slope.
• Use Target Surface for Bench Slope: When the benches use a surface file for the target, this option makes the bench slope follow the target surface model. Otherwise, the bench slope is set in the next dialog.
  
• Bench Color: This setting puts the bench 3D polylines in the Pit Layer on a different, specified color so they stand out against the slope breaklines.
  
• Bench Taper At Surface Tie: When a bench meets the Ground Surface, this option tapers the bench width to zero over this specified distance.
  

The next dialog defines the cut and bench slopes. Cut Slopes are entered as ratios. The Cut Target can be either a fixed depth number, a fixed elevation, a fixed width or to a grid file. For a grid file, the program will find the intersection of the cut slope with the grid surface and will end the cut slope at this intersection. For example, you could make a grid file for a second coal seam and have the bench occur at this coal seam. For the width method, the program creates a cut slope to the target surface with a variable slope to reach the surface at a fixed cut slope width. This width method can only be used on the final bench.

After the cut slope, the bench slope and width are used. The cut and bench slopes are applied in order until there is an intersection with the surface. Once you have all the cut slopes defined, you can use the Save button to save these slope settings to a .PIT file. Then these settings can be recalled later with the Load button.

The Pick Perimeter For Z Range function prompts to select a perimeter polyline from the drawing. This function reports the elevation range of the Ground Surface along this perimeter which is useful as a reference for setting the bench elevations.

Four different sets of slope schemes can be defined. To define the another slope scheme, select other Slope Group tab. The set of slopes that you are currently editing is indicated by the selected tab. If you define different sets of slopes, then the program will prompt you to pick which sides to apply each set of slopes to. All sides are assumed to be slope type one. So you only have to identify types two, three and/or four. If only one slope group is defined, then you will not be prompted to select any additional sides. 

If a pit already exists to one side of the current pit, then this existing pit should be part of the Ground Surface grid file. Then the program will intersect the surface right away on this side without creating all the bench-cut slopes.

Here are a couple of examples of the various settings in Design Bench Pit.

• Offset Method:

• Offset Method with Road in red:
• Projection Method:

• Multiple Pits with Offset Method and Viewing the Grid History File in 3D.

Prompts

Pick the pit polyline: pick the closed polyline
Pick pit polyline segment for side 2 slopes (Enter to continue): pick the segment near midway, it will highlight
Pick pit polyline segment for side 2 slopes (Enter to continue): pick the segment near midway, it will highlight
Pick pit polyline segment for side 2 slopes (Enter to continue): press Enter to continue

Pulldown Menu Location: Surface in Surface Mining Module
Keyboard Command: minepit2