Lecture 10 Design of Rough Draft Stage Pits ©2010 Dr. B. C. Paul Note – These Slides contain numerous screen shots from the program MineSight® developed by Mintec Inc in Tucson Arizona. The concepts being presented are regarded as part of the body of “common knowledge” to those schooled in Surface Mine planning and can be found in parts in many surfacing mining texts and articles as well as in training materials prepared by Mintec for use with their computer program.

What We Have  We have a Block Model of Our Ore Reserves  We have an outline of an ultimate pit that identifies those blocks likely to be economic for recovery by surface mining  We have a series of pit surfaces designed to encompass subsets of our ultimately minable ore that go roughly from the most to least valuable ore  We have an idea of how we will expand the pit.  It is unlikely that those stage pits we have at this point actually represent minable geometries  What we will try to do now is to create Minable Pit Geometries with the “Pit Expansion” tool in MineSight –In the old days you had to do this with exhaustive hand drawings

Take A Look at the Initial Pit We Plan on Developing with Top Down Mining

Use the MineSight Query Function to Find out How Deep the Bottom is Click on the Query Button (the Question Mark)

Now Click on the Bottom of the Pit The Query Screen gives you A run-down on that Point including its Elevation. (Make sure you Look at the Pit33 Elevation)

I Jump to a 2D View at about 2400 meters My unmined surface Is at about 2670 Feet about 300 Meters in 15 meter Increments is 20 benches. (It would be handy To know how many Benches to have My pit expansion Tool to set up as We will see).

Pull Down the Engineering Tools Menu and Pick the Pit Expansion Tool

It Wants Me to Name The Geometry Object it will store my pit in Click open after Naming the object

The Pit Expansion Dialog Comes On

Set Up the Bottom Trace of Your Pit We will trace the Contour outline For a pit “bottom” Click the Digitize Radio Button. Type in 2405 (we Want the contours To hit bench Elevations in the Block model. Check of close to Close the line You will trace Click add and then Trace the line.

Digitize around the initial pit outline and right click to end the operation

Set The Expansion Make sure we start on the Same level I’ve picked 24 benches Which I know will go up Above the surface (because I used Query to check Surface elevations before I ever started this)

Click Over to the Required Tab Set the starting elevation (2405 in our Case) Set the bench height (15 meters in our Case) Set the Toe to Crest Slope and Over-All Pit slope Click the radio button to use the slopes to Control bench geometry Click buttons to tell the pit to expand Upward and outward Click Preview to see if this looks good

The Computer Instantly Projects 24 Benches Upward and Out Click Apply if you Like it. (Or Cancel If you say – oh Crud That’s not what I Had in mind).

The Color Changes I’m going to exit The pit expansion Tool while I Consider.

The Computer Wants to Confirm Our Intent to Exit the Expansion Tool I’m going to confirm

It Asks Me If I Want to Make A Full Surface of My Pit instead of just Contours Saying yes is easy And quick. I’m going to decline For right now Because I’m still A little concerned About pit depth (I’m not to the Projected bottom) And I want my Contours and surface In separate files.

My Next Issue – The Pit Bottom  I know my pit actually was projected to go down 4 more benches (Because I used that Query to find out where it was before I ever started) –I didn’t start there because the bottom got a little square and I had a more even shape starting further up –I’m also not sure how far down I want to go because I want to have practical room for moving equipment at the bottom of the pit.

I Can Also Use the Pit Expansion Tool to Project Down I restart my pit Expansion tool And this time set It to copy an Existing line to Use to project from

I Also Reset for Just 4 Pit Bench Levels

I Click Add and then pick the bottom contour at the toe of my bottom bench A Right Click at the End confirms my Selection is Complete.

I Go to My Required Tab I of course set my 2405 elevation and My pit slopes but The new thing is I set radio buttons To expand Downward And Inward

A Preview Click Shows the Expansion Going Down Now I decide Whether that is A practical Amount of space If not I would Cancel and go Back to the Expansion Screen and set For less than 4 Benches down. I’m going to apply In this example.

I’m Going to Exit Expansion Without Making a Surface I’m going to create A separate Geometry object For my rough Pit surface (I call it rough Because I still have Not dealt with Roads) Using Data Manager I will go the Pull down file menu Highlight New and Then pick geometry Object from the Side menu

Yes I Have to Name That Object

Now I’m Going to Get Ready to Put the Pit Surface in My Surface Object I already clicked On my new surface Object – then right Clicked it and Picked edit from The pop-up menu (You can tell cause My surface file is Now a golden Open box) Now I click on my Contours file – right Click to pop up The menu and go To the select option. (I’m going to select the contours for making my pit surface)

Now I Will Use the Triangulate Surface Tool Go to Surface And drop the Menu Pick triangulate Surface with the Selection (ie – those Contour lines I Just picked).

It Asks Me If I Want to Use the Open Edit Object or Create Another I already have My surface object Open and ready To go so I will Say Ok

I Triangulates a Pit Surface for Me!

I Want a Solid Surface – Not a Bunch of Triangles Click on my object Right Click to pop Up the menu Highlight and left Click properties

The Object Properties Window Opens I click the faces only Radio button And then click Ok

I’ll Admire My Work of Art

Of Course I See One Little Problem I’ve got a bunch Of benches Hovering in the Air - I don’t think So!

I Will Have My Surfaces Clip Each Other and Give Me One Integrated Surface For My initial set up I made sure my Original unmined Surface and my New pit surface Was turned on. I also created a new Open edit object For my merged Surface. Now I will prepare to Use the intersect Surface tool. I drop down the menu Under surface and Pick Intersect Surface Tool

Up Comes The Tool Control Window I need to pick the Surfaces to work With The blue worm Means to pick from The viewer The Red Box means You will pick them From the Data Manager file list. I’m going to pick Them in the viewer

Pick My Primary Surface Left click the Blue worm and Then left click Anywhere on my Unmined surface The pretty yellow Box surrounds My selection I will next right Click my mouse To signal the Completion of my Selection.

After My Right Click My surface name Appears in the Primary group Line And the yellow Box turns blue Now I get ready To pick my Pit surface by Left clicking the Blue worm for The secondary Surface.

Left Click the Pit Surface, Right Click to Complete the Selection The Output options Become black (instead of gray) Meaning they are Now available Set the Radio Buttons to merge The Surfaces And have the Surfaces cut each Other and save The union of what Is left.

Click Preview to Check Out that the Result is What You Had in Mind

If Satisfied Click Apply The where would You like to put this Screen comes up It can go in the Open edit object (which I have Ready) Or if I had been less Prepared I could Have it create a New object name For me on the fly. When I’m ready Click Ok

My Finished Wire Frame Surface Appears I’m not satisfied With my display

I Tried to Turn Off My Surfaces that I Didn’t Want to See But the blasted Program won’t Turn it off. When this happens The program is Usually waiting for You to do Something. The almost Universal solution 1- Right click to Finish what you Are doing 2- Click the weird Save icon.

Yup It Wanted Me to Save My Work I turn off the Other surfaces And go to the Properties of my Merged surface And set it to Display faces Instead of a wire Frame. Now isn’t that just So neat to look At!

So What Have I Done and What Am I Trying to Do?  I used MSOPIT to map out a series of nested shells that targeted my best ore first and then worked down to poorer ore  I figured out what sequence I wanted to go in.  Then because the MSOPIT shells were not quite practical I used them as a map and tried to draw in my stage pits roughly using the pit expansion tool.  Of course at this point I have only got my first pit drawn in. –I’ll next go through a series of push-backs –(Yup – Its drawing time again)

Looking At My Next 2 Pushbacks This area Is pushback #2 For those who want to know how I did this – Here is A detour

View Magic  On turned on the surfaces I wanted to see –Pit #10 (my expansion to pit) –Merged Pit Surface (which I just recently created) –I turned Off other surfaces On my merged surfaces I clicked On it and then right clicked to Pop up the menu Then I picked properties On the Object Properties Dialog Box I picked the surfaces tab Then I checked off transparency And then used the arrows to work Up to 62% (which worked well For my view)

Since I Will Be Increasing Depth I Need to Know Where the Bottom is I’ll use Query Click ? Click bottom Read elevation of Pit 10 surface 2195

I Have a Problem with a Simple Pit Expansion from the Bottom Fitting The edge did not Push out as much As it should I missed some Benches I’ll cancel my pit Expansion and look For places where My benches push out

The Pit Also Pushes Out at Several Distinct Points This push out is At 2270 (up 5 benches From the bottom)

There is another distinct push out one more bench up 2285 meters

And Another Distinct Push out up 6 more benches

I’ll Try My Pit Expansion Again I’ve created a stage Pit 2 contours Object I’ve set the viewed To 2D at the 2200 Meter level. Now I’ll start the Pit expansion tool

I’ll Digitize in My Pit Bottom on 2195 I’m also set to Expand 5 benches Up which is where I know I need to Deal with the first Bench that pushes Out.

I’m Going to be Working Back to A Final Pit Slope So I Set that Under Required Oh –by the Frustrating way When I completed My base string it Disappeared (reason it was on 2195 but my 2D View was on 2200)

When I Expand Up Those 5 Levels it Looks Like a Good Fit I am cutting into A nose of rock The computer Said was low On grade I probably to not Want to leave Little noses of Rock sticking Out for slope Stability reasons

Now Lets Get to That Level Where One of the Benches Pushes Out I’m going to “Edit My Base String” to Handle this push Out of a bench. Another thing I did Was to create Another horizontal Gridset with grids Every 15 meters to Match the benches. I then attached that To the viewer so my Viewing would be Easier.

It Ask Me What I Want to Edit on What Level They had a pretty Good idea I would Want to edit the Current level and Move to the toe for The next bench Going up because That is the default Click Ok

The Pit Expansion Menu Shuts Down but the Point and Polyline Menus are Available I’m going to use Point Move To move points on The toe of the next Bench out to where They need to be.

I Drag Out the Points to Fit the pushed out bench To finish my Effort I 1- Right Click My Mouse (to tell it I’m Through moving Points) 2- I click on the Weird save icon To save the work Whenever the Program stares At you and won’t Let you do anything Try right click save

My Base String is Now Moved I set it to expand Up 1 level (because I know There is another Push out one bench Up) Human interest Note that the program Keeps track of My base string Expansion history And shows me where My other base strings Are located.

Select My Shifted Base String for the Expansion I clicked copy Then I clicked Add Then I clicked on The base string I will use for the Expansion. Yes it turned a Pretty yellow to Show what was Picked.

I Click Preview, Check it Out, and then Click Apply When I Like It.

I Jump Up One Bench Level to See Where the Extra Push-out is. Note I have reset The viewer 2D to The next bench Level up Note the program Now has 2 base Strings in the History.

I Use the Edit Strings – Point – Move Trick and Move My Toe Out to The Bench

I Now Copy My Modified Base String and Expand Up 6 Benches

Yup It Looks Like I’m Getting a Good Fit On My Way Up This Time

Now I Have to Push My Base String Out Again to Get a Bench That Pushes out Remember I set my 2D viewer plane to The bench level I Was working on I picked edit string Then I used the point Menu I used the point Function to move Points on the base String out to bench Trace from my MSOPIT

I Thought Expanding up 15 Benches Would Get Me Above the Surface It didn’t I could have Avoided the problem By doing a query Before I started so I would have known How high the Surface was just Like I new how Many benches to Expand up between Push outs.

I Go to the Top of My Pit and Pick the Highest Toe to Do One More Expansion

Oh Ya – This is Working

There is My Pit 2 Surface Well actually not Quite – remember I still have my Phase 1 pit and the Current topo surface I need to merge Into (If your thinking I’m About to use my Intersect surfaces Tool again you are Right). You can See where My next Push back will Be.

Note in a Few Places My Original Pit Expands Out beyond by Stage 2 Pit I’m going to have To use surface Intersections to Capture this.

A Technical Dissatisfaction Skinning back the Benches on this Side is really to Small for a good Push back – I Could argue I need To redo the pit so The east side of The pit was in the 45 degree wall

What Should Happen The wall needs to be here. Of course this now Makes this bottom To small for Equipment If I start the pit on The 2270 Level then I won’t have an Unworkable bottom

I Start on 2270 This Time Digitizing a Base String that Will Fall inside My Initial Pit on the East Side

I Set for The Steeper Final Slope

I Expand Up One Bench and Modify the Base String for the Bench at 2285 to Push Out to the West

I Preview My Expansion Up 6 Benches Youch! Look at That unstable Nose of rock Cancel and lets Fix the base string

Now That’s More Like It

Looking on 2D Up Six Level Where the Benches Push Out Again Note that my New pit is indeed Inside my Initial pit (thus keeping Me from assuming A tiny infeasible Push back to the East)

I Edit My Base String Out to Where the Bench is Projected by Pit 10

I Expand Up Past the Surface Note that my Stage 2 pit has Stayed inside My initial pit on The east side.

I Triangulate My Stage 2 Pit and Prepare to Use the Intersect Surfaces Tool

I Set Up for My Intersect Surfaces Tool I’ve created a Geometry object For my initial Merged surface I will merge my Stage 2 pit with My original topo (I’ll clip off those Pit levels that Are hovering in The air.)

I Activate My Intersect Surfaces Tool Remember it is on The Surfaces Pull Down Menu

I Pit My Surfaces and Preview the Merge My primary surface Is the original topo My secondary Surface is my Unedited stage 2 Pit surface I’m going to merge Surfaces And I will have the Surfaces cut each Other so what ever Is the lowest is saved

Step One Looks Lovely But we remember We have actually Mined some rock Away out here In the initial pit (Time for another Round with the Merge surfaces Tool)

By Turning on the Initial Pit Surface I Can See the Part that is Already Cut Away

I Set a Final Pit 2 Surface Object and Activate the Intersect Surfaces Tool

This is What My Stage 2 Pit Will Look Like My next push Back will push Out here.

So I Will Go Top Down and Dig My Initial Pit

Then I Will Push Down and Out Toward the West

So What Am I Doing Here  I Use Lerch Grossman to get a profile of my ultimate pit.  The I use a series of floating cones with price fakes or multi-val to set out a series of guide pits that take the best ore first  Then I look at those stage pits to see which steps actually outline push backs that are large enough to do with real equipment  Then I go in with the pit expansion tool and draw in stage pits that actually correspond to feasible push backs –This gets me my mining sequence

Now It’s Your Turn  In Assignment 7 You Laid Out a Series of Guide Pits and an Expansion Strategy  In Assignment 8 you will use the pit expansion tool and lay out your pit at the end of 5 different stages of development –Ie – you will be drawing in 5 nested pits that follow your expansion strategy using the pit expansion tool.