Grade Control

In an effort to minimise the cost of mining and maximise the recovery of ore, careful Grade Control is an integral and essential part of both open pit and underground mining operations. The grade control module provides you with tools to automate and simplify the more mundane aspects of production control tasks. This module provides solutions for open pit and underground grade control.

Open Pit Grade Control
Underground Mine Grade Control
Drill Hole Database

Define Hole ID Format

Interpolate List Inclusive
Interpolate Range Inclusive

Interpolate List Between
Interpolate Range Between
Interpolate Between End Points

Load Drill Holes To Database
Load Channels To Database

Channel Survey Observations
Clear Drill Hole IDs
Draw Drill Hole IDs
Erase Drill Hole IDs
Transform Channel

Grade Control Grade Calculation
Recall Sample File
Draw Sample Grades
Draw Sample IDs
Draw Samples
Erase Sample IDs
Erase Samples
Mean Point Average Grades
Sichel Point Average Grade
Interval Weighted Average Grade

Open Pit Grade Control

A typical scenario is that numerous grade control drill holes are drilled on a regular pattern. These drill holes provide a high density of sample points, that are used to assist the mine geologist delineate between ore and waste material. Often grade control drill holes have a dual purpose and are used as blast holes. Blast hole design usually requires consistent burden and toe spacing which presents a regular drilling pattern. Also, the depth, dip and azimuth of the drill holes is consistent, and it can be assumed to be identical for all holes in the drilling pattern.

Since the drill holes are usually drilled in a regular pattern, and because there are so many of them, one aspect of the grade control module for open pit applications is to minimise the amount of work required to survey each of the drill holes. This is done using the following methodology:

1. The surveyor surveys the drill holes at each end of a row of drill holes and notes how many holes exist between the two surveyed end holes. Note that the spacing of the holes must be consistent.
2. The resultant data are processed into coordinates, typically with one of the data recorder processing functions found in the Surface Surveying module.

Drill Holes

The convention used to automatically assign Sample IDs as the drill holes are loaded into the database is as follows:

Take the hole ID and append the ``_'' character to the hole ID as a separator between sample 1 at the top of the hole and sample nn at the bottom of the hole. Thus if the Hole ID is "A123" and there are 5 samples at intervals of 2 metres down the hole the data in the resultant interval table of the database is:

Channels Samples

The convention used to automatically assign Sample IDs as the channels holes are loaded into the database is as follows:

Take the channel_ID (equivalent to hole_ID) and append the ``_'' character as a separator between the distance from the start of the channel to the end of each channel. Thus if the Hole ID is "A123" and there are 5 samples at intervals of 2 metres along the channel, the data in the resultant interval table of the database is:

This convention is simple and unlimited in the number of samples which may exist in a hole or channel. It is essential that the results from the assay laboratory include the sample_ID so that the data may be merged effortlessly with the survey data using the Load Database function within the Drill Hole Database module.

1. The .obs file created is recalled into the Graphics module and the grade control functions are used to:

interpolate the missing drill holes between end points

load the interpolated drill holes into a drill hole database and assign depth, dip, azimuth and down hole sample interval details.

When these three steps have been completed, the surveyed details of the drill holes exist in a drill hole database. Before any further grade control work can be performed it is necessary to load and merge the sample assay results from the laboratory.

Underground Mine Grade Control

A typical scenario is that channel samples are taken at regular intervals as the mining face advances. The channel positions are generally only surveyed approximately and it is often necessary to adjust the position of the channel to be aligned or coincide with surveyed outlines of the underground excavation. Each channel is likely to have a different number of samples which may depend on the length of the channel and its location with respect to the orebody. The methodology described below can minimise the time and work required to process channel samples.

Note: The channel samples need not be in an underground mine to use the grade control module.

1. The channels are surveyed and are eventually stored in a string file as one distinct string segment per channel, the path of the string defines any irregularities in the location of the channel. This string file can be created by a number of the Surface and Underground Survey functions.
2. The channel string file is recalled into the Graphics module, and the location of the channels modified, if necessary, to be aligned more precisely with the surveyed mine workings.
3. Each segment MUST have the channel identifier (equivalent to drill hole ID) in the D1 field of the first point in the string. Also, the last point in the segment MUST have the depth range of the samples in the channel, see the string file example below:

The two segments above will create samples intervals in the database as follows:

When channels, represented as string segments are in their correct positions with respect to the underground workings, the data is ready to be loaded into the drill hole database.

When these three steps have been completed the surveyed details of the channels exist in a drill hole database. It is now necessary to merge the sample results from the assay laboratory with the channel survey data.

Drill Hole Database

The drill hole database is an integral part of the grade control system. The data used in grade control, i.e. the survey data and the sample assay data, are generally produced at different times. Typically, survey data are available much sooner than assay data.

For optimal operation efficiency and control, the different types of data should be processed as soon as they become available. This means that there is a time lag between the processing of the survey data and the processing of the assay data.

This time lag presents a problem in effectively managing the grade control data in the drill hole database. The problem is obviated by use of a UNIQUE KEY for the sample_id field in the interval table which is used to store the drill hole, or channel sample data. See drill hole database creation in Generic Tools Reference for details on how to define a unique key for the samp_id field in interval tables.

The Sample ID is the key which simplifies the merge process of survey data and down hole depths for each of the samples, with any assay data received from the laboratory.