Tailings is an application designed to streamline the process of creating surfaces to represent staged deposition to a tailings impound facility. The principal function is the 'model tailings' function, which does the work of building the final surface. The remaining functions are tools to assist in the preparation of the model and the presentation of results after the model is complete.
Tailings uses a gridded surface model. A slope profile equation is applied to each discharge point in turn, and elevations of the points on the gridded surface away from the discharge point are determined mathematically from this equation and from existing boundary conditions (topography, barriers and pond elevations). The input slope profile is a mathematical expression (either a polynomial function or a linear-discontinuous expression) that represents the expected final stable surface extending away from the discharge point. Each discharge point may have distinct slope profiles for deposition above and below water. Tailings will change from one to the other where appropriate. The discharge points are processed sequentially. The starting surface for any given discharge point is the output surface after processing of the preceding discharge point.
There are two methods by which a tailings surface can be created:
"Standard mode" - Discharge elevations known
(deposition time unknown).
A series of discharge points are set up with fixed elevations.
The program will model the surface and calculate the time
required to deposit to each of the discharge points in turn
to achieve the given elevations.
"Advanced mode" - Discharge elevations unknown
(target deposition time known) - The xy locations
of the discharge points are known, and the user wishes
to determine the z-elevation of the discharge points after
a given period of deposition.
This method requires more processing time because the
solution is determined iteratively. This method is the preferred
method for generating deposition schedules for fixed periods
(ie. 6 months, 12 months, etc.). There is a practical lower limit
to the size of period that can be scheduled for a given basin
size (ie. it will generally be inappropriate to determine a surface for
daily or even weekly deposition).
Function: 2D Profile From 3D Lines
The slope profiles to be used by the tailings application may come from 3D survey profiles. This function will convert lines that represent 3D surveyed slope profiles into 2-dimensional centreline profiles (XY coordinates) that can be used by Excel or other spreadsheet programs to plot the slope profile and fit a polynomial curve. The polynomial curve function can be used as the slope definition in the tailings application. This function requires that the slope profile(s) be continuous segments, and the first point in the segment be the location of the discharge point.
A typical slope profile plotted in Excel. After transformation to 2D with the "2D Profile from 3D lines", the string file (a comma-delimited text file) was opened in Excel, and x,y values plotted against each other. The polynomial fitted-curve equation was added with the Excel function: CHART-ADD TRENDLINE (It is a good idea to set the format of the numbers in the trend line equation to greater precision than is given by default by right clicking on the curve equation that is displayed and choose "Format Data Labels". On the "Number" tab displayed, Category: Scientific, with decimal places: 6 is generally a good choice. Polynomial charts of high orders tend to produce erratic results if few decimals are retained because very large numbers (ie. x^6) are multiplied by very small coefficients (ie.1X10-14).
Invoking 2D Profile From 3D Lines
The "2D profiles from 3D lines" function can be invoked in a number of ways as
follows:
Using 2D Profiles From 3D Lines
When you invoke 2D profiles from 3D lines you are presented with the following form
Input string file & Id number
The string file location and id number of the input profiles
String range
The string range of the input profiles
Output string file & Id number
The location and id number of the string file to store the output
Profile type
The Profile Type is the kind of survey information that is to be converted and
determines how the script will calculate the distance between the starting
point of the segment and the current point.
Z Values
The Z-values can be calculated in two ways:
Function: Basin Capacity Chart
It can be useful to determine the amount of water a basin can hold for a given flooded elevation. The curve of elevation vs. basin capacity is sometimes called a "struck capacity curve". This tool will take a gridded surface (the inputs or outputs from the tailings application) and output the table of information necessary needed to create the struck capacity curve.
This function outputs a comma-delimited (.csv) file. The same results are also output to the message window.
A typical struck capacity curve for an example basin. The output table of information for two grid files was charted in Excel to produce this graphic.
Invoking Basin Capacity Chart
The create basin capacity chart function can be invoked in a number of ways as
follows:
When you invoke the basin capacity chart function you are presented with the following form:
Select a topographic grid file
The name of the string file containing the topographic data
Grid spacing
The grid spacing to be used when calculating the volume at each grid node.
This should be the same grid spacing used when modeling the tailings
(although any multiple of this grid spacing can be used).
The x and y axis grid spacings are assumed to be the same.
Boundary string file
The name of the string file containing the boundary string.
A boundary string must be used if the calculations are to be limited to a
specific subset of the grid file.
For example, a topographic grid file may contain more than one basin.
If you wish to determine the capacity of a specific basin, you choose which
area to perform the calculations.
A boundary string is mandatory.
This function assumes that there is only one segment on the boundary string.
Boundary string number
The string number of the boundary string
Choose the starting elevation
Define the lowest value for which you wish to report results. This will also become the lower
bound for the elevation groups. Data will only be reported starting with the lowest elevation
interval that actually exists. (For example, assume the starting elevation is zero, elevation interval
is 10 and the lowest data point is z=1234. The lowest interval for which results will be output is 1240.)
Optional maximum elevation for calculations
The elevations of interest may be far lower than the maximum elevation of the
topography grid being processed. Enter a maximum elevation for which you wish
to calculate results. If this elevation does not fall on an elevation interval,
the next higher elevation interval will be used. (For example, assume the starting elevation is zero, the
elevation interval is 10 and the optional maximum is 1901. The highest interval for which information
will be reported is 1910.). Choosing an optional maximum elevation which does not fall on an elevation
interval is not recommended.
Choose the elevation interval
The elevation interval (in project units ie. ft or m) for reporting cumulative
volume increments.
Currently this has been fixed at 0.05.
Future versions will allow the use of user-defined elevation intervals.
Chart output file
The name of the file to which the table of information will be output.
This file will have an extension ".csv", which can be opened directly in Excel.
Function: Edit Discharge Points
Discharge points are generally represented by points in graphics.
The properties of the discharge points and the properties of the flows from
them are
stored in description fields.
This function will permit the user to edit the discharge point properties in a
table
by selecting a string of discharge points to be edited in graphics.
This function will edit all the discharge points on a selected string at the
same time.
After the edits are complete, the function will write them back to a single
segment on that string.
Invoking Edit Discharge Points
The edit discharge points function can be invoked in a number of ways as
follows:
When you invoke the edit discharge points you are asked to select a point on the discharge point string to edit. When the discharge point has been selected you are presented with a form that allows you to edit the discharge point information.
Discharge point string number
A read only field that displays the number of the selected discharge point
string.
All discharge points same slope
If all the discharge points are to have the same slope definition, only the
default slope
definitions, and this checkbox need to be filled in. NOTE: If this box is
checked,
all the existing slopes stored in the discharge points will be overwritten with
the
default slope definitions.
Default subaerial slope
A slope definition for tailings deposition above water to be applied to all the
discharge points.
The slope definition must be one of the forms defined below for "subaerial
slope definition"
This definition will only be applied to all the discharge points when the "All
discharge points same slope" checkbox is checked.
For specific details on the format of the slope definition, see the item in the
Frequently Asked Questions (FAQ) section below on
slope definitions
Default subaqueous slope
An underwater slope definition to be applied to all the discharge points.
The slope definition must be one of the forms defined below for "subaqueous
slope definition"
This definition will only be applied to all the discharge points when the "All
discharge points same slope" checkbox is checked.
For specific details on the format of the slope definition, see the item in the
Frequently Asked Questions (FAQ) section below on
slope definitions
Y, X, & Z
The coordinates of the discharge point.
Name
A name that will be used to identify the discharge point in output reports.
The discharge point name is not mandatory, but makes for clearer understanding
of the output.
Subaerial slope definition
A slope definition for tailings deposited on land. This slope can have 3 forms.
For specific details on the format of the slope definition, see the item in the
Frequently Asked Questions (FAQ) section below on
slope definitions
Subaqueous slope definition
A slope definition for tailings deposited under water.
Slope expressions have the same format and syntax as subaerial slope
expressions above.
For specific details on the format of the slope definition, see the item in the
Frequently Asked Questions (FAQ) section below on
slope definitions
Max distance
If a polynomial interpolated slope has been used to describe the slope of the
tailings basin, the curve is generally only valid for interpolating data.
That is, if an interpolated curve was generated from data within
x
metres of the discharge point, it will not generally be useful for estimating
elevations beyond
x
metres.
If we must calculate elevations beyond the distance that the curve is valid,
a polynomial curve can fluctuate wildly. To prevent this, we define a maximum
valid distance for this subaerial slope definition. Beyond this distance we
will use a linear slope (called the end slope). Note that this limit is used
for above water AND underwater tailings deposition.
This value is ignored when a linear-discontinuous slope definition is used.
End slope
The constant, linear slope to be used for all deposited points further away
from the discharge point than
the max interpolation distance, expressed as a percent. A negative slope,
slopes downward away from the discharge point. (ie. -1.00%)
This value is ignored when a linear-discontinuous slope definition is used.
Density
The in-situ dry density in tonnes per cubic metre (or tons per cubic foot if
using imperial measurements) of material being discharged from this discharge
point.
If this field is empty, the default discharge rate from the tailings modeling
parameters form will be used.
Discharge
The discharge rate of this discharge point in dry tonnes per day (or dry tons
per day if using imperial measurements). If this field is empty, the default
discharge rate from the tailings modeling parameters form will be used.
Order
The order in which the discharge points will be deposited.
The tailings application deposits tailings on one discharge point at a time
until the tailings surface has reached the maximum deposition for that
discharge point. It then moves to the next point and continues with each point
in turn. If the tailings streams from adjacent discharge points have
significant overlap, the order in which the deposition points are processed can
have a significant effect on the material deposited by individual discharge
points, although the total deposition will remain the same.
Reordering all the numbers in this column will reorder the discharge points.
This new discharge point order will be reflected the next time this function is
run. Ordering starts at zero.
The principal input and output of the tailings application is a gridded surface.
The grid spacing will have some effect on the accuracy of the calculations.
For more information on grid spacing and selection of grid spacing, please see
the note on grid spacing in the FAQ section.
In order to get the best results from a particular basin, it is useful to model
a typical configuration in the basin, and run tests on a variety of grid
spacings
to determine the best grid spacing to use for a particular basin.
This function will automate the creation of multiple grids at different grid
spacings
to use in these sensitivity tests.
Invoking Create Grid Spacings
The Create grid spacings function can be invoked in a number of ways as follows:
When you invoke the create grid spacings function you are presented with the following form:
Range of grid file spacings to create
Enter a valid range of grid spacings you wish to create.
An output file will be created for each spacing entered.
For example: 30,200,10 is a valid range of grid spacings to create.
Grid string number
The string number on which the grid spacings will be created.
The examples in the tutorials that accompany the tailings application use
string 1001 to represent grids.
Location name for grid files
The file name that will be used (along with the grid spacing) to name the file.
For example "grid".
If the range of grid spacings is set to 10,30,10 this function will create 3
output files called grid10.str, grid20.str and grid30.str.
Select a styles file to draw with
Select the styles file used to draw the grid lines in graphics.
The name of this styles file will be saved with the grid file so that the grid
points are displayed correctly when recalled later.
Origin X & Origin Y
The X and Y coordinates of the lower left corner of the required grid pattern.
X extents & Y extents
The X and Y extents of the grid pattern.
This is not a coordinate value, but the length in x and y that the pattern will span.
Overlay grids with dtm location & Id
This function will overlay them on a pre-determined dtm file so that the grids
output from this function can be immediately used as input for the model
tailings function.
Model tailings can work in either standard mode (discharge elevations known)
or advanced mode (required deposition time known). These modes are explained in the
overview section
See the Tailings tutorial for further information on the steps required to model
in standard or advanced mode.
Invoking Model Tailings
The model tailings function can be invoked in a number of ways as follows:
When you invoke the model tailings function, you are presented with the following form:
Select Parameter File
The tailings application stores all the parameters used for any particular run
in an ascii file with a .dep extension.
The last-used parameters file is automatically recalled each time the function
is invoked.
If you wish to recall a different parameter file, select the file browser (the
down arrow) to locate the correct parameter file.
When the file is selected press the
button to recall the parameters from the file into the form.
If you wish to save the entered parameters on the form to a new file, type (or
browse for) the filename and then press the
button.
To clear all the parameters on the form, press the
button.
The 'Input Files' Panel
The model tailings function operates on files that must exist on the hard-drive.
The input files panel is used to specify all these files.
Note that the discharge points, dam and berm centrelines, and basin boundaries
can all be created in the same file as long as they are created on different
string numbers.
The tailings example data was created this way.
Topo grid
The input location, id and string range of the grid file that represents the
tailings surface at the beginning of the tailings deposition.
Discharge points
The location, id, and string range discharge point file containing the
discharge points.
The format of the information in the description fields of the discharge
points is:
If you use the graphical function:
edit discharge points
to modify the properties of the discharge points, this information is already
being managed for you, and it is not necessary to edit the point information by
hand.
Dams
The simplest method for modeling berms is with their centrelines.
The dams file requires the entry of a file of dam centrelines
(There are other methods of modeling dams and berms. For a discussion, please
see the FAQ on
berm modeling
"
The location, id, and string range of the file containing the dams and berms.
Currently they must all be the same string number. If there are no dams/berm
centerlines, enter a dummy string number (9999, for example).
Basins
The location, id, and string range of the file containing basin boundaries.
If you wish to have a pond form in the tailings area, you will need know the
elevation of
the pond surface, and the general area, but not the specific location of
the pond. A polygon must be drawn around the entire drainage area that
will drain into each specific pond. Multiple ponds can be modeled in a
tailings basin, each with a different pond elevation. The basin outline(s)
must enclose every point where deposition is to occur. If a grid point
is discovered not to be inside a basin boundary, a warning message will
be displayed. This basin boundary can be as simple as four points around
the outside of the grid. Its elevation should be set to the elevation of
the desired pond. The pond name if used should be in the d1 field of the
first point of each segment.
Output
The location, id, and string range of the output grid file where the grid
points will be placed.
The output grid file will contain exactly the same number of grid points as the
input file.
It is possible to use the output of one tailings run as the input for the
next tailings run. The description fields for the current run are all
placed as the first 4 description fields. The existing d-fields in the
file are pushed down (ie. D1 becomes D5). The output fields:
Grid Parameters
The same grid spacing is used for both the x and y directions.
Default subaerial slope
If a discharge point has no subaerial slope defined, this slope will be used.
This can save some time if there are many deposition points with the same slope
equation.
For specific details on the format of the slope definition, see the item in the
Frequently Asked Questions (FAQ) section below on
slope definitions
This field can be left blank if all discharge points have slopes defined.
Default subaqueous slope
If a discharge point has no subaqueous slope defined, this slope will be used.
This can save some time if there are many deposition points with the same slope
equation.
For specific details on the format of the slope definition, see the item in the
Frequently Asked Questions (FAQ) section below on
slope definitions
This field can be left blank if all discharge points have slopes defined.
Dams are always boundaries
If the "dams are always boundaries" box is checked, tailings
will always be prevented from flowing over dams. If this box is not
checked, tailings deposition will calculate whether or not the dam can
be breached, and will deposit accordingly.
Slope method
Distances from the current deposition point to the discharge point (for
substituting
into the slope definition equation) can be calculated either in a direct line
from the discharge point
(direct) or along the flow path of the tailings (cumulative).
The direct method is most appropriate in regularly shaped basins where tailings
does not need to flow around obstacles.
The cumulative method is appropriate when the flow path is not direct from the
discharge point, and the tailings must flow around a berm or other obstacle,
as the direct method will always overestimate the amount of tailings deposited
in these cases .
The cumulative distance calculated for this gridded model is a grid
approximation of the cumulative distance from the discharge point to any given
point. This distance will always be longer than the "true" distance (getting
closer to "true" the smaller the grid spacing) so the volumes calculated with
the cumulative method tend to be slightly lower than the volume for the direct
method.
Default in-situ (dry) density
The default in-situ dry density is used to determine tonnage
deposited given a calculated volume. Its units are tonnes/m^3 (metric)
or tons/ft^3 (imperial). This value will be used only if the density
is not defined in the discharge point definition.
Default daily discharge
The default daily discharge is the tonnes(metric) or tons
(imperial) of material coming from the mill per day. This value will
be used only if the density is not defined in the discharge point
definition.
View progress on screen
If this checkbox is checked, points where deposition occurs will be created in
the current layer on the string defined for topo output. The information in the
d-fields of these created points is different than the information
saved to the output file, as this feature is used primarily for debugging.
Only points where deposition occurs will be created.
This box should be left unchecked if tailings is to be run in advanced mode.
Output report file
The output report is a comma-delimited (csv) text file. The first part of
the report summarises the input information. The second part summarises
deposition for each discharge point.
Deposition is broken down by subaerial and subaqueous deposition.
The subaerial deposition is calculated by summing the deposition of all grid nodes
where the final surface deposited in air
(when approaching a pond, it is possible that tailings at a particular node
could be deposited both under water and above water. In any case, it is the elevation
of the final deposited surface for the current discharge node that determines whether
deposition will be classified as subaerial or subaqueous).
The "Time dependent parameters (Advanced Mode)" panel
Solve for discharge point elevations given time?
Check the "Solve for discharge point elevations given time" check-box on the
"Time Dependant
Parameters" panel in the lower right of the form to run Model Tailings in
Advanced Mode
The principal difference in the input files information when using advanced
mode is that
the discharge point elevations should be at the elevation that they were BEFORE
deposition starts.
(In the standard mode, the discharge point elevations must be at their intended
final elevations).
Tolerance
Advanced mode only:
The time (+/-) tolerance (in percent) of an acceptable
time result from the target value. For example, if a tolerance of 10% is
selected, and a cycle time of 120 days is chosen for a particular string, model tailings
will stop iterating when it has found an elevation increment for the discharge points
on the current string that results in a discharge time within (+/-)12 days of
120 days. The larger this value, the fewer iterations have to be performed to close in on
an appropriate answer within tolerance.
Max discharge delta z
Advanced mode only:
The user-determined limit on the discharge point
elevation increase. The maximum elevation increase (in the real world units of
the project) that can be applied to any discharge string. If this elevation
increase does not deposit enough volume to meet the target time (ie. there is not enough
material deposited to meet the time requested) the program will accept this
result and continue to the next discharge string. This value is also the 'first guess'
that the algorithm will make in testing elevation increments in order to find an
upper limit on time. It is worthwhile to choose this as close to (but still
above) the probable upper limit as possible to limit the number of iterations
performed.
Discharge points output file
Advanced mode only:
The discharge point elevations output from this run (at the
final determined elevation can be input into a later run. They will be saved to
this filename. This output file can be used as the input in a following tailings
cycle
Discharge point string & Target time
Advanced mode only:
The target discharge time (in days) must be defined for each
discharge point string. The order of the string numbers is important. The
program will attempt to determine a solution for each string in turn.
The target discharge is defined by string so that the user may choose to model
deposition
to two different areas "concurrently" and have the discharge point elevation
increases in
one area calculated independently (in as far as they can be as they are being
modeled in
a linear manner) from the elevation increases in the other areas.
The demonstration item on the menu allows you to view an example output data set showing the initial and final contours, a dam design, and colour contoured tailings thicknesses.
Standard Mode Demonstration Data
A demonstration set of data is provided to illustrate the standard mode of operation.
You can find a set of menu items for this demo in the "Demonstration" menu under the "Tailings" menu.
The menu items on that menu coorespond to the steps listed below.
For more details on running the tailings modeling application in this mode, see the
procedure section for standard mode
"C:\MineSolutions\Tailings\example_std\"
Note the following things:
You may view the properties of these discharge points with the function Edit discharge points.
(Start the function from the tailings menu, and select one of the discharge points.
This function will allow you to edit any of the discharge point properties, but we recommend for
the first time through this demonstration that you do not change any of the parameters.)
Note that all the discharge points are above the existing topographic surface at the final intended elevation of the tailings surface.
Some of these discharge points have densities assigned to their discharge stream.
Others will use the default density assigned when the model tailings function is run.
(If you wish to view the gridded surface that forms part of the input to the tailings application,
you can reset graphics now, and drag the file "topo0.str" into graphics.
This file was created by draping a grid over a dtm (digital terrain model)
created from the file input_contours1.str.
To continue with the demo, reset graphics again rerun the Standard demo - Step 1 function again."
file into graphics again.)
(If you would like more information on creating a grid, creating a dtm or draping files onto dtm surfaces, please check the Vision on-line help or tutorials available from the help menu)
This function looks for the last-used tailings parameter file in the current working directory.
It should start up with the file name "example1.dep" in the "Parameter file" field.
If this is not the case (and you are in the correct working folder), you can browse
for the file and press the "open parameter file" button ().
For a detailed explanation of the field on this form, please see the model tailings references section.
The form should be filled out like this:
Note that information is stored in each point about its original elevation as well as the new elevation.
(D1 - Point ID,D2 - Elevation at the start of deposition,D3 - Deposition thickness,D4 - Deposition flag (0=none, 1=subaerial, 2=subaqueous))
Advanced Mode Demonstration Data
A demonstration set of data is provided to illustrate the advanced mode of operation.
It is assumed that you have already have been through the standard mode demo data set.
as this demo covers only the additional considerations involved with the advanced mode.
Tailings uses the standard Mine Solutions licensing system. All licensing
functions are available from the license menu option on the Tailings
menu. These menu are options a discussed in detail in the
Mine Solutions License Manual
.
For assistance on problems that you maybe experiencing with Tailings
fill in the support form on the web site at
www.minesolutions.com/support.html
. If
you don't have web access then send a mail to
support@minesolutions.com
.
Procedure: Model Tailings in Standard Mode
The procedures for modeling the
standard
and
advanced
modes are
very similar. The following sections outline the procedures to be
taken in order to produce results for each method. It is recommended
that a beginning user trial the standard method first to understand
the fundamentals of the modeling method and interpretation of results
before attempting to use the advanced method.
The grid can be trimmed to save file size.
One way to trim the grid is with the FILE TOOLS-APPLY BOUNDARY STRING function.
Remember that the string that the grid points are on is considered a spot
height string.
For specific details on the format of the slope definition, see the item in the
Frequently Asked Questions (FAQ) section below on
slope definitions
What do i do with the output?
To run a number of scenarios with small changes in input parameters
to produce data for sensitivity charts (ie. slope definition vs capacity
or discharge point elevation vs capacity, dam raising curves, etc.). Charts can
be produced by compiling results from several different runs into a spreadsheet.
Producing contour maps of deposition. You can generate surface
contour maps and deposition thickness maps (isopach maps) by contouring
the output file on z or D3 (deposition thickness). An outline of the
maximum extent of deposition can be generated by contouring (triangulation
method is best) on D4 (deposition flag) at value =0.5. Contouring
on D4=1.5 will create an outline of the underwater deposition areas.
The pond elevation can be extracted by creating a dtm of the output
grid, and extracting a contour at z=pond elevation.
The images at the start of this help are screen captures of surfaces
that were generated using these methods, and displayed using the
DISPLAY-DTM WITH COLOUR BANDING function to get the surfaces coloured.
Procedure: Model Tailings in Advanced Mode (Discharge time targets known)
The basic operation mode will determine the time necessary to fill a
basin for given discharge point elevations. It is possible that the
user wishes to assign elevations to discharge points so that the period
between discharge point elevation changes is a fixed interval (six
months or a year, for example). It is possible to determine these
elevations by trail and error with the standard model. The advanced
mode is intended for these circumstances.
1.
How are tailings deposited in the computer model?
To view the input data, input parameters, and output results, follow the following steps.
For more details on running the tailings modeling application in this mode, see the
procedure section for advanced mode
"C:\MineSolutions\Tailings\example_adv\"
Note the following things:
You may view the properties of these discharge points with the function Edit discharge points.
(Start the function from the tailings menu, and select one of the discharge points.
This function will allow you to edit any of the discharge point properties, but we recommend for
the first time through this demonstration that you do not change any of the parameters.)
Note that all the discharge points are ON the existing topographic surface at the INITIAL elevation of the tailings surface.
The advanced mode is required to determine the final elevation of the discharge points.
This function looks for the last-used tailings parameter file in the current working directory.
It should start up with the file name "example2.dep" in the "Parameter file" field.
If this is not the case (and you are in the correct working folder), you can browse
for the file and press the "open parameter file" button ().
For a detailed explanation of the field on this form, please see the model tailings references section.
The form should be filled out like this:
Note that information is stored in each point about its original elevation as well as the new elevation.
(D1 - Point ID,D2 - Elevation at the start of deposition,D3 - Deposition thickness,D4 - Deposition flag (0=none, 1=subaerial, 2=subaqueous))
Tailings will automatically install a 30 day trial license the first
time it is run. The trial license will allow unrestricted access so that
you may fully evaluate the product.
Visit
www.minesolutions.com
or contact
sales@minesolutions.com
for further information.
(Discharge point elevations known)
STEP 1:
Create a grid of points that represents the existing
tailings surface.
Generally, a project will start with some form of dtm surface. Although
there are a couple of ways to prepare your grid, the most reliable is
probably:
There must not be any "holes" inside the grid data where you might expect
tailings to be deposited.
The script will not estimate deposition in areas for
which there are no grid points so deposition will be underestimated,
although the script will appear to complete correctly. If the basin in
the grid cannot contain the tailings, the program will deposit only up to
the edge of the grid points. This might mean that the amount of material
deposited will be underestimated. For a more realistic deposition, the
grid should be extended to include enough area for the tailings to
completely deposit, berms should be placed to prevent the tailings from
leaving the gridded area, or the discharge point configuration should be changed
to prevent tailings from flowing off the gridded area.
STEP 2:
Define the tailings slope.
There are currently three ways to define a tailings slope surface
for the script:
Note: For information on transforming 3D survey lines into an Excel
chart for the purposes of extracting a curve-fitted slope definition, please
see the notes for
2D Profile From 3D Lines
. It is a good idea
to set the format of the numbers in the trend line equation to greater
precision than is given by default.
STEP 3:
Model the berms and dams and discharge point locations
Digitize the locations of berms, dams and discharge point locations and save
them to a file. They should be on different string numbers. The berms
and dams can be in a different file from the discharge point points. This design
file must be different than the file that contains the topo grid points.
The example problem has all the design information in the same file.
It is a good idea to put the design information at the true elevation
(drape strings over the original dtm) but it is not absolutely necessary.
If the dams are not at a true 3D elevation, you have an option on the model
tailings form to force them to always act as a boundary (even if the tailings
could theoretically overflow).
STEP 4:
Add the slope definitions to the discharge points.
It is possible to manually edit the elevations, labels, and slope
definitions of the discharge points, because all this information is stored in
d-fields of each discharge point. The
Edit Discharge Point Definitions
function will allow you to edit elevation, names, material properties and
tailings surface profile for discharge points
STEP 5:
Run the model tailings function. See the reference section on the
Model Tailings
function for details on specific information to be entered on the form.
STEP 6:
Evaluate the Outputs
There are two principal outputs from the tailings modeling script:
There are several reasons for running the model tailings function:
This mode will solve for a target discharge time which has been assigned
to each string. It will process each string sequentially and move all
discharge points on the same string up by the same amount (delta z)
to deposit an appropriate amount of tailings. Strings are processed
in the order specified by the user. As in the standard mode, discharge
points are processed sequentially within these strings. The user controls
how close to the target time will be considered acceptable and the maximum
allowable delta z.
The report does not tally up the total discharge time for all the strings,
because it is accepted that the different strings may be intended to
simulate concurrent discharge. While this version does not model concurrent
deposition directly, discharge streams from different strings that do
not overlap or do not overlap significantly can be modeled adequately
with this method, subject to testing.
The algorithm performs a series of interpolating runs to arrive at the
solution: an inital run at the discharge point starting elevations
and at the maximum allowable delta z gives the program initial information
to interpolate for its 3rd run. Successive runs continue to interpolate
between runs.
There are a few cases where a solution is not possible. If one of
these cases are encountered, the program will choose a pre-determined
appropriate course of action (select the nearest solution), display a warning
and continue.
For an explanation of the three cases, please see the Frequently Asked Questions
(FAQ) not on:
The general procedure for using model tailings in the advanced mode is the
same as for the The
standard mode
operation
with the addition of time-dependent parameters:
When a new deposition surface is being created for a given set of discharge
points, the tailings application will find the closest downstream grid points
from the first discharge point.
It will determine if deposition can occur to these downstream points (given
physical surface, berms, etc.).
If deposition can occur, then it will calculate an appropriate new elevation
for this point given a user-defined slope expression for the final tailings
surface and the distance calculated from the discharge point to this current
deposition point.
From these newly deposited points, it will search for the next set of
downstream points, check whether deposition is possible, calculate new
elevations and so on.
When no more deposition can occur for a given discharge points, the application
will start deposition from the next sequential discharge point.
The process continues until there are no more deposition
points. The application models sequential deposition, but for discharge points
without significant discharge stream overlap, concurrent deposition can
satisfactorily be modeled. For basins where the deposition points are
relatively close together, and the discharge streams might have significant
overlap, the first discharge point in a basin may have a lot
of deposition and the remaining discharge points may have relatively little
deposition. Concurrent deposition was beyond the scope of the original
tailings project. An estimate of programming cost can be provided to any
interested purchasers
2.
How are berms and dams represented in this model? A real dam has volume
and will reduce the amount of space available for tailings.
Dams can be modeled as temporary centerlines or incorporated into the
surface model and treated as a fixed part of the terrain.
The dams in the example data are represented as a centrelines. This
is adequate for initial design and multiple scenario modeling (because
centrelines are easy to edit and move around for testing different options),
but where the dam volume is significant relative to the basin
deposition, and for final finishing work, you may wish to create the
dam using either the pit design tools (drive outline from a centreline
then expand at design slope to the base, then create a dtm) or the
centreline-profile method (the /dem/v4_examples folder has a good
demonstration of this method.
under the civil engineering menu) and incorporate it
into the topography.
It is also a good idea to retain the dam centreline as a hard boundary for the
following reason:
If a dam exists as part of the topographic surface, there are cases where the
gridded model of the dam won't be detailed enough to prevent tailings from
overflowing it.
For example, the crest width of the dam may be small compared to the grid
spacing.
There may not be enough points created on the dam crest in the gridding process
to properly model the crest.
In these case, it is a good idea to model the dam centerline with a line
segment.
The same applies to any berms that are part of the initial topography.
3.
How do I account for freeboard when modeling tailings against dams
or berms?
Tailings allows the user to decide where the deposition
points must be (x,y and z) to achieve deposition targets. Dam centerlines
can be overlaid on the final tailings surface (max tailings elevation)
and freeboard applied (with string maths) to obtain the resulting centerline.
In the case where an existing design is to be evaluated, there are
several techniques to be applied:
The deposition freeboard (deposition to within a certain elevation of
the dam crest) is controlled by the user. The profile equation will
create a surface exactly to the elevation of the discharge point height. If
you wish to incorporate freeboard, you can alter the deposition equation
(if the discharge point is at the design crest) by changing the constant in
the polynomial equation (ie.: If my slope is z= ax^2 + bx, I could
change it to z=ax+6 + bx -0.5) OR you can alter the physical location
of the discharge point point to simulate the freeboard. The first method will
not work with linear definition slopes (though I will add it if it
becomes a condition of sale). It should be noted that deposition
occurs on outward from deposition points. Tailings will be deposited
behind dams only as far a the deposition will allow. If a tailings
dam is to be filled to capacity, discharge point points should be placed along
the crest and modified accordingly for freeboard.
4.
Why is the in situ dry density the only property required for
calculations? Isn't the wet density also important?
The dry density is used only to calculate the time taken to deposit
to a modeled surface given the volume deposited and the tailings output
rate (in dry tonnes or tons) from the mill: time(days)= (deposited
volume*dry density)/mill output rate
Wet density is not an input because water balance is not calculated.
If water balance were to be properly incorporated the evaporation, and
rainfall and runoff/decanting in the basin would also have to be
accounted for. This was beyond the scope of the initial project. An
estimate on the work required, and its cost can be provided to potential
purchaser who might be interested in this option.
5.
Is the deposition rate for all the discharge points the same?
Since the version of 270601, it is now possible to assign different
density and discharge rates to each discharge point. If the discharge
rate and density are not entered on the "edit discharge points" form,
the default discharge and density will be used. The default density
and discharge rate are entered on the "model tailings" form.
6.
How do I calculate the water capacity of my basin for different
elevations?
The basin capacity function will output a table of water capacity vs. elevation information for given inputs.
7.
How to I generate a polygon that represents the maximum limit
of tailings deposition?
The D4 field of the output grid contains an integer flag that is:
Use the contouring tools to contour this field (d4) and draw a single
contour line at a value of 1.0. This will be the limit of tailings
deposition.
If you wish to see the limit of tailings deposition underwater, contour
this field on a value of 2.0. This is not the same as the pond outline.
If you wish to extract the contour line that represents the pond outline,
you should contour the "z" field at the elevation of the pond.
8.
My pond elevation fluctuates throughout the year. How can I
account for this?
Tailings assumes that the pond elevation is static throughout the
course of the run. Depending on the circumstance, the pond elevation
can significantly affect the volume of tailings that can be stored in
a basin. A pond elevation should be chosen that reflects the average
pond elevation for the period of the run. If fluctuating pond elevations
are to be modeled, an average pond elevation should be selected for a
shorter period, and appropriate discharge point elevations chosen
(usually by trial and error) to model these shorter periods.
9.
I am using the ADVANCED option. The program cannot find an
appropriate elevation for my discharge points. What is going on?
All the discharge points in a given string are manipulated at the same
time. If there are many discharge points on a string, and they cover
a large area, it is possible that
There may be three reasons why a deposition target might not get reached:
Graphical illustration of case 'c'
10.
How do I uninstall Tailings?
Tailings uses a commercial installer which creates an uninstall
program. You can uninstall from the Control Panel (Start--Settings--
Control Panel) by double-clicking on the "Add/Remove Programs" icon.
Find the entry for "Tailings"
in the window below. Select it, and click the "Add/Remove" button.
The files associated with the tailings package will be removed from your
hard-disk. Any custom files will not be removed.
11.
How do I define slope profiles?
The slope away from any particular discharge point controls how the tailings
surface is created.
The slope can be defined in 3 ways:
a. linear-discontinuous of the form:
LINEAR: [distance1]@[slope]|[distance2]@[slope2]|[distance3]@[slope3]....
Distance1, distance2, etc. are discrete distances away from the discharge point
(ie. distance1 might be the first 1000m from the discharge point, distance2
might be the next 2500m away, and distance 3 might be the next 9999m).
The distance units are the same distance units as the project distances.
The only currently-supported unit of slope is percentage(%).
A positive slope is one which slopes upwards, away from the discharge point.
Most slope definitions will be negative.
Slope is represented as: "-1.00%" or "-0.23%". An example:
LINEAR:1000@-1.50%|2500@-1.25%|9999@-1.00%
An illustrated example of a linear-discontinuous slope definition. Subaerial and subaqueous slope profiles are defined in a similar way.
b. Excel polynomial interpolation
A polynomial expression in x can be used to define the slope of the tailings
profile.
This option was added to make use of the expressions created by MS Excel when
an interpolated line is added to a graph.
See the notes on the
2D Profile From 3D Lines
function above for more details on interpolated graphs.
The equation generated by Excel can be cut and pasted into this field. An
example:
y = -3.5033E-14x4 - 1.7706E-09x3 + 1.3089E-05x2 - 3.2936E-02x + 1.7083E-02
c. Any SCL (Surpac Command Language) expression in x
The Surpac Command Language (Scl) has an expression function (SclExpr).
This option gives the user the option to create any expression (log, trig,
etc.) as an expression of the slope.
Any valid expression created with the Scl Expr function in one variable (x must
be used) will be accepted by the tailings application.
Expressions of form 2 (Excel polynomial interpolation) are converted to this
form internally before they are used.
SCLEXPR:0.232 * pow($x,2) + 0.01*$x + 0.024
12.
The tailings application cannot seem to finish a tailings run. What's
happening?
It is possible that there are too many grid points defined in the surface.
The tailings application has a practical limit of 10 000 points that it can
process.
This is often enough, as the increased accuracy that can be achieved for a
given basin by reducing the grid size beyond a certain point is minimal.
You should test the sensitivity of the basin to be modeled against grid spacing.
Please see the notes on
grid spacing selection
for more information.
13.How does grid spacing effect my results?
Because the tailings application uses a grid based method for estimating the
tailings basin capacity, your choice of grid spacing will have an effect on the
accuracy of the tailings model results.
The smaller the grid size, the closer the resulting surface will approximate
the "idea" estimate, although there is a penalty in processing time as the
number of points to be processed increases.
Theoretically, if we use a small enough grid spacing, we will not have to worry
about the final estimation.
Unfortunately, there is a practical limit on the number of points. This
practical limit is currently approximately 10000 points.
It is the equivalent of choosing a grid spacing of 10m on a 1000X1000m basin.
Fortunately, there is a point where decreasing the grid spacing will have a
relatively small impact on the final volume.
The determination of this optimal grid spacing (large enough to permit fast
processing, but small enough to provide reliable results) can be done by
conducting trials on a typical configuration of discharge points on a number of
grids of different spacing.
A comparison of calculated volume for a number of tailings deposition runs on a typical basin at various grid spacings from 30m - 200m. Note that there was a point at about ~60m grid spacing where the results were very nearly the same (within 2%) as the grid spacing was decreased. At the same time, the number of points and processing time increased dramatically.
In order to get the best results from a particular basin, it is useful to model a typical configuration in the basin, and run tests on a variety of grid spacings to determine the best grid spacing to use for your particular basin. The create grid spacings function automates the creation of multiple grids at different grid spacings for this kind of testing.
14. Why do the contours produced with the "cumulative" slope method look different than the contours produced by the "radial" slope method? How will this affect my results?
The radial slope deposition method calculates distances from the discharge points
to the deposition point directly (as-the-crow-flies).
This method calculates the true horizontal distance between any grid point and the current discharge points.
The resulting contours will be cone-like emanating from the discharge points.
The radial method cannot provide useful modeling if there are significant changes in tailings flow direction (flow around large obstacles or doglegs in the tailings basin, for example).
The cumulative discharge method keeps track of the distance away from the discharge point along the flow path of the tailings.
This allows it to calculate distances around obstacles.
Because the tailings surface is modeled as a grid, the distances will be a cumulative inter-grid distance, which will always tend to be a bit longer than the equivalent radial distance.
This means the volumes (and resulting tonnages) will be lower than by the radial method.
Visually, the cumulative method will appear as octagonal contours, where the radial method will produce circular contours.
On basins where a comparison is possible between the two methods, we have typically seen a ~5-10% results difference between the radial and cumulative methods.
It is always a good idea to make this comparison on your own basin.
If the basin in question has significant flow direction changes, it might be possible
to compare results for the two different slope methods by digitizing a "dam" polygon around
the area that has clear intervisibility with the discharge point and compare results for that area only.
A hybrid cumulative-radial method is being contemplated a future release to improve the estimation and visual results.
Please contact info@minesolutions.com if you would be interested in sponsoring this development or the development of any new features.
Sponsored development assures that features of interest to the sponsor will be completed on an agreed timetable.
15. How can I validate the results of the basin capacity function with other Surpac functions?
Similar results can be obtained using the Surpac built-in functions for calculating volumes between surfaces.
This function was written to remove the tedium of preparing separate dtm surfaces for every elevation at which
results are required. The following steps will produce results at a specific elevation which can be compared
to the script results:
a. Recall the gridded topo surface. Create a dtm from these points and save it to a file. Keep this file on the screen.
b. Create a new, temporary layer. Set the digitizing elevation to the
elevation whose results you intend to compare to the script. Digitize a polygon (square is easiest) that can
contain the whole of the topo grid. Create a dtm surface of this polygon. Verify that this polygon is at the correct elevation
and save the new dtm to a file.
c. Run the function VOLUMES=>CUT AND FILL BETWEEN DTMS.
Specify the planar dtm as the "first dtm".
Specify the surface created from the gridded surface as the "second dtm".
The boundary string will be the polygon that defined the basin for this model.
d. Open the results file and check the "cut volume" number.
This number will be used to compare to the volume at a similar elevation reported by the script.
The cut volume only is used because we wish to report the volume below the specific elevation (the planar dtm), but
also above the topo surface. The fill volume will report the volume below the topo surface and
above the specified elevation.
The script produces results from a grid of points, where the dtm operates on dtm surfaces.
You should expect to find a difference between the two results, but the numbers should agree to within
a small percentage (typically less than 1%).