Designing a Switchback

7/30/2019 Designing a Switchback

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Designing a Switchback

Toe-ramp-crest method: using the complete sequence to create a switchback ramp.

Overview

In this part of the tutorial you are going to design the upper portion of a switchback road for a

bench, consisting of new ramp, enlarged crest flat and new crest strings.

The Toe-Ramp-Crest design method (for a bottom-up design direction)

makes use of toe, ramp and crest string elements, created in that order,

to define a bench in the pit. The full pit design is typically done on a

bench by bench basis, starting from the lowest bench and working

upwards. For a single bench, the toe string is created and adjusted, the

ramp is inserted and finally the crest string are added. This method

builds ramps that include access to the berms and can be applied

working either from the bottom up or the top down.

Prerequisites

Required:

Created a new project and added all the required tutorial files i.e. the exercises on theCreating a New Projectpage.

Loaded and viewed the ultimate pit shell model data i.e. the exercises on theViewingUltimate Pit Shell Modelspage.

Created and applied a custom legend, filtered cells, for the NPVS block model i.e. theexercises on theCreating a Custom Display Legendpage.

Recommended:

Displayed and customized the open pit design toolbars; saved a profile i.e. the exerciseson theDisplaying Design Toolbarspage.

Specified project and mine design settings i.e. the exercises on theSpecifying DesignSettingspage.

Filesrequired for the exercises on this page:

_vb_npvmod1 _vb_trc_pit70

Link toExercises


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The following exercises are available on this page:

Designing a SwitchbackExercise: Designing a Switchback

The procedure for creating a switchback is much the same as that used

to create a standard spiral ramp section. The general procedureis as

follows:

create the lower half of the bench, using a standard toe-ramp-crest sequence

create the upper portion of the bench, using a reverse directionramp-crest sequence, using the following guidelines:

the start point for the upper road is the outside corner(and not the inside corner)

the direction point is given in the opposite direction i.e.in the opposite direction to that of the lower ramp

the crest string at the bottom of the reverse directionramp requires modification to include a flat area

connecting the two ramps, to form the switchback

the upper portion does not have a toe string a final crest string is created as normal.

A switchback can be created at any elevation within the pit.

In this exercise you are going to use the pit strings _vb_trc_pit70 as a starting point for creating a

switchback for the next bench (bench 80m) consisting of a full sequence of new toe, ramp and

crest strings; the bench will be 10m high. Thisincludesthefollowingtasks:

Defining data and design plane settings Saving to a new strings file Creatingtheupperswitchbackramp Enlargingthe 70m crestarea Creatingthe 80m toe Savingthe data.


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Defining Data and Design Plane Settings

1. SelecttheDesignwindow.2. In the Project Files control bar, Strings folder, drag-and-drop the following file into the

Design window:

_vb_trc_pit703. In the Sheets control bar, Design Overlays folder, select only the following overlays (i.e.

display these overlays):

Default Grid _vb_trc_pit70 (strings) _vb_npvmod1 (block model)

4. In the View Control toolbar, click Zoom All Data.5. In the View Control toolbar, click View Settings.6. In the View Settings dialog, define the Section Orientation and Mid-Point XYZ coordinate

(6110, 5100, 70) and other parameters shown below, click OK:

These settings place the Design view plane (the working plane) at an

elevation of 70m i.e. the bottom of bench 80. This allows the block

models cells for bench 80 to be displayed and also used to guide the

positioning of the new toe string. The View | Set Viewplane | Snap to

Plane (stpl) command can also be used to set the view plane i.e. the

design plane elevation.

The clipping option is used to display only the data which falls within

20m above or below the selected view plane. Setting the clipping equal

to the bench height makes it possible to view the full previous bench

and the new bench design strings.


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7. In the View Control toolbar, click Zoom In.8. In the Design window, drag a zoom rectangle to display the view extents shown below:


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Saving To a New Strings File

1. In the Loaded Data control bar, right-click on the _vb_trc_pit70 (strings) object, selectData | Save As.

2. In the Save New 3D Object dialog, click Single Precision Datamine (.dm) File.3. In the Save New Strings dialog, select the path to your tutorial folder

'C:/Database/MyTutorials/OPDesign', define the File name: as 'trc_pit80', click Save.

4. In the Loaded Data control bar, check that _vb_trc_pit70 (strings) has been replaced bytrc_pit80 (strings).

5. Check that trc_pit80 (strings) is the current strings object i.e. highlighted bold.CreatingtheUpperSwitchbackRamp

1. In the Design window, select the yellow crest string.2. In the Pit Design toolbar, click Create Road Segment (rseg).3. In the Studio 3 (Road Segment) dialog, define a Road Gradient % of '10', a Road Width of

'20', an RL at end of Road of '80', click OK:

RL at end of road is the elevation at the top of the ramp.

4. Follow the messages displayed on the left side of the Status Bar for the steps below.5. As shown below, right-click (snap) to the outside corner of the yellow crest string where

the previous road segment ends and then left-click at a location out towards the south:


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The first point defines the inside corner of the ramp and must be

snapped to the indicated crest string; the second point indicates the


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upwards direction of the ramp i.e. south.

6. In the Design window, check that a green ramp string has been created and that the creststring has been automatically modified, as shown below:


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Enlargingthe 70m CrestArea


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The flat area connecting the two ramps needs to provide enough turning

space for machines traveling on the haul roads and is defined by two

crest strings as follows:

an enlarged standard crest string which defines the north-eastern and eastern sides of the flat area

a new short crest string defining the western side of the flatarea, the ends of which are snapped to the standard crest and

the inside top corner of the previous ramp.

1. In the Design window, using the Point and String Editing: Standard toolbar commandsMove Point (mpo) and Insert Points (ipo), adjust the yellow 70m crest string between the

two ramps, outwards to increase the flat area, as indicated by the black dashed line shown

below:


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2. Check that you have moved and inserted points, to place the standard yellow crest stringin the position shown below:


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3. Select the orange 60m toe string.


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4. Using Design | String Tools | Break | At Point (bs), break this string at the two pointsshown below, starting with the northern point:


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5. Select the short portion of broken string, in the Pit Design toolbar, click Create RoadContour (rcon).

6. In the Studio 3 (Create Contour) dialog, define the contour elevation as '70', click OK.7. In the Design window, right-click and select Deselect All Strings (das).8. Check that the short yellow crest string (with three segments) has been created as shown

below:


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9. Select this short crest string and using Move Points (mpo), move both end points of thisshort string, snapping them (right-click) onto the points shown below:


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If you are unsure of where the end points are positioned, first move

them away into the adjacent white space using left-click, then move


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them back in again, this time snapping (right-click) them to the required

final points. Here, the northern point of the short crest string snaps to

the enlarged standard crest string; the southern point of the short crest

string snaps to the top inside corner of the previous ramp string.

10.Using Design | String Tools | Connect (conn) , following the prompts in the Status Bar,connect the three portions of broken orange 60m toe string shown below:


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11.Zoom out, select the connected 60m toe string and check that it is again a single closedstring (perimeter), highlighted yellow in the image below:


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CreatingtheBench 80 Crest


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1. Select the outer, full standard 70m crest string.2. In the Pit Design toolbar, click Create Road Contour (rcon).3. In the Studio 3 (Create Contour) dialog, define the Contour Level as '80', click OK.4. In the Design window, right-click and select Deselect All Strings (das).


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5. Check that a full, yellow 80m crest string has been created as shown below:


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The upper ramp of the switchback does not have an orange toe string,

but instead uses the crest string which forms part of the lower half

ramp.

6. Select Format | VR View | Update VR Objects (vro).


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7. In the VR window, rotate the view and check that your is as shown below:

Savingthe Data


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1. Select File | Save.2. In the Save Data/Set Auto Reload dialog, select to Save the trc_pit80 (strings) object, click

OK.

If you are not happy with the design at any stage, you can erase the

incorrect strings and recreate them using the open pit design

commands. The design MUST be restarted from either a toe or crest

string, NOT from a road segment.

You can check your design strings against the example file

_vb_trc_pit80.dm.

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Designing a Switchback