BMT Blast Movement Monitor Guide de l'utilisateur

BMM® System Manual

Monitoring Procedures

Solutions to Reduce Ore Loss and

Dilution

BMM®System Manual –Monitoring Procedures i

Monitoring Procedure-Manual_WIP_FCC August 2012

TABLE OF CONTENTS

BMM®System Manual _____________________________________________________________1

Monitoring Procedures_____________________________________________________________1

1Introduction _________________________________________________________________1

2Planning the Location of BMM®s_______________________________________________2

2.1 Introduction......................................................................................................................2

2.2 BMM®Separation.............................................................................................................2

2.3 BMM®Location for Grade Control.................................................................................3

2.4 BMM®Location for Blast Dynamics ...............................................................................4

2.5 Monitoring Holes.............................................................................................................6

2.6 Monitoring Hole Diameter..............................................................................................7

3BMM®Installation ___________________________________________________________7

3.1 Introduction......................................................................................................................7

3.2 Installation Procedure......................................................................................................8

3.3 Delayed Start..................................................................................................................10

3.4 Wet Holes .......................................................................................................................11

3.5 Test Button on the Activator .........................................................................................12

4BMM®Detection ____________________________________________________________13

4.1 Introduction....................................................................................................................13

4.2 Orientation of the Detector............................................................................................13

4.3 Detecting Procedure - Locating the Peak Signal..........................................................14

4.4 Graphical Display ..........................................................................................................16

4.5 Validating the Peak........................................................................................................17

4.6 Sample Field Shapes ......................................................................................................18

4.7 Procedures to Improve Efficiency.................................................................................19

4.8 Common Mistakes by New Users ................................................................................19

5Depth Calibration ___________________________________________________________20

5.1 Overview ........................................................................................................................20

5.2 Procedure........................................................................................................................20

5.3 Using the Data................................................................................................................21

6Potential Hazards ___________________________________________________________21

BMM®System Manual –Monitoring Procedures

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1INTRODUCTION

The Blast Movement Monitor (BMM®) System consists of directional transmitters placed within

the blast volume prior to blasting, which are then located after the blast with a special detector.

The data is then processed with purpose-designed software. The system is applicable to all open

cut mines and is easy to use —designed for routine use by site personnel.

Each BMM®is activated, programmed

and installed before blasting.

A special detector is used to locate each

BMM®after the blast. Data is

downloaded to accompanying software

that calculates the movement vectors

and then summarises and archives the

results.

Ore boundaries can then be redefined to

reflect the measured movement of the

blast and therefore enable accurate ore

control.

Detection of the BMM®s after blasting is

generally the most difficult part of the entire

process to learn due to its practical nature. Good tuition and experience are the greatest assets

for any practical activities. For example, it would be very difficult to learn to ride a bicycle by

reading a manual because there is no sensory experience. Similarly, a new BMM®System

operator needs to get a feel for what the changing signal strength is indicating and how to move

the Detector. This can only be obtained by actually doing it. This manual does not replace first-

hand tuition from an experienced operator and it should be used to supplement that practical

training to accelerate the process of developing experience. It includes:

Planning the monitoring locations

BMM®installation procedure

The correct technique for locating BMM®s

Depth calibration procedure

Potential hazards.

This manual covers how to use the BMM®System as a whole. The detailed description of the

Detector and Activator are covered by the respective equipment manuals.

There are Quick Reference Guides available for download from the

VIP-Zone on the BMT website. These are step-by-step procedures for

monitoring a blast and processing the data. New users should print

and refer to them regularly until the procedures are familiar.

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2PLANNING THE LOCATION OF BMM®S

2.1 Introduction

The two main reasons for monitoring blast movement are to improve grade control and to

understand blast movement dynamics. In practice, the objective of many blasts will be a

combination of both. The data requirement of each is different so the decision process of where

to install the BMM®s will also be different. Regardless of the main reason for monitoring, there

are operational constraints that must always be followed. The objective of this section is to

provide guidelines to help with this decision process to maximise the value of using the BMM®

System.

As with any new activity, the best advice to new users is to commence conservatively. Plan the

BMM®locations to make detection easier until experience is gained. This can be achieved by

selecting appropriate depths, Multi-ID BMM®s (colours), separation distances and locations

within the pattern. For example, the BMM®’s signal gets weaker as the depth increases and

therefore is harder to locate and requires greater separation from BMM®s of the same colour.

Concentrate at about mid-bench to begin with before investigating the movement in other parts

of the bench. The exception to this is for multi-pass (flitch) mining where it is important to

monitor different levels.

The number of BMM®s installed depends on many factors but the primary question is, “If a

BMM is placed at a certain location, will it lead to a more accurate post-blast delineation of an ore

boundary and therefore more ore?” The decision factors include:

Grade

Price of mineral

Cost of monitoring

Ore/waste boundary condition –structural vs. disseminated

Movement variation

Size and shape of ore polygons

Orientation of ore polygons

Isolated vs. contiguous ore polygons

Bench height

2.2 BMM®Separation

There are four Multi-ID BMM®s available, each identified by a colour; orange, yellow, red, and

green. Each Multi-ID BMM®emits a different signal and therefore can be identified separately

by the Detector. Therefore, it is possible to install more than one BMM®per hole and/or place

BMM®s close together –assuming they are of a different colour. If there is inadequate separation

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between adjacent BMM®s of the same colour, they may be impossible to locate. There are a few

simple rules that should be followed when designing separation distances between BMM®s of

the same colour.

If they are installed at similar depths, the separation should be a factor of 2–3 times

the depth. Deeper BMM®s require greater separation.

If there is a large difference in depths of the BMM®s, the separation must be 3-4 times

the depth of the deepest BMM®(maximum 30 m). For example, an orange BMM®that

is 2 m deep should be at least 25 m away from an orange BMM®that is 8 m deep.

When planning BMM® locations

and installation depths, remember

to take into account the planned

movement direction and distance

within the blast. BMM®s with

adequate separation at the

installation stage, may actually

move towards each other and end

up too close after the blast. The

blast plan shown is an actual blast

where this occurred and several

BMM®s could not be located after

the blast. The green and red dots

are the pre and (expected) post-

blast BMM®locations respectively.

2.3 BMM®Location for Grade Control

When planning the location of BMM®s specifically for the purposes of grade control, think

ahead to what will be critical for translating the ore polygons. The main aim is to locate the

BMM®s as close as possible to the ore boundaries to reduce the error associated with

interpolating the ore is translated away from the measured vector. This therefore reduces the

overall ore loss and dilution. To achieve the best result, planning BMM®locations should take

into account the following factors.

1. High grade ore –ore loss and dilution will have a greater economic impact on higher

value zones, therefore definition of the correct boundary of high grade polygons will

have a higher priority than lower grade polygons.

2. Ore boundary conditions –the worst case is high grade adjacent to waste and the

mineralisation is structurally controlled, i.e. sharp cut-off.

3. Proximity to other BMM®s of the same colour after the blast –consider the expected

movement distance and direction (use the planned initiation timing contours) to ensure

BMM®s don’t end up within the minimum separation distance if they move towards

each other (refer to Section 2.2).

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4. Depth –Horizontal displacement varies with depth and is typically D-shaped with the

maximum occurring adjacent to the explosive column, i.e. in the lower half of the bench.

Ore loss is more costly than dilution so it is important to maximise the recovery of the

mineral, especially for high-grade ore polygons.

a) For single-pass excavation, it is recommended to install the BMM®s below the

top of the explosive column because this region is typically most representative

of the majority of the bench height. This is typically close to the mid-bench level

but could be adjusted under certain circumstances. Contact a BMT consultant if

you want to know more.

b) For multi-pass (flitch) mining, the movement of different flitches are likely to be

different. Therefore plan to have BMM®s in each flitch. It may be feasible to

combine movement vectors from different flitches under certain circumstances

but contact a BMT consultant to discuss this.

5. Close to ore polygon vertices –during the ore translation process, it is the vertices of

the polygons that are going to be moved.

6. Small, isolated ore polygons (surrounded by waste) –these have the potential for the

greatest percentage of ore loss and dilution (up to 100%). If the polygon is very small

and a single BMM is planned to be near it, install a BMM®inside the ore polygon so all

edges are similar distance from that vector.

7. Polygon boundaries that are oblique to expected movement are more important than

parallel boundaries.

8. Concentrate most of the BMM®s in the body of the blast, away from edge-effects, unless

there is an important ore boundary close to an edge.

9. Survivability of the BMM®s –Install halfway between blast holes to maximise the

distance between BMM®s and any explosive. See Section 2.5.

10. Impact on drill and blast operations –for ease of drilling monitor holes and explosive

truck access, holes drilled within the rows of blast holes will have the least impact on

drill and blast operations. See Section 2.5.

11. It is important for the person responsible for defining the post-blast ore polygons to

understand the 3-dimensional movement in various regions of the blast. Therefore,

while most BMM®s will be installed specifically to adjust ore boundaries, it is

recommended that some should also be used to gain an understanding of movement in

all regions of the blast. This is important because it is not practical to measure

movement everywhere, so this knowledge will often be used to supplement the

measured movement.

2.4 BMM®Location for Blast Dynamics

BMM®s can be installed in certain locations specifically to understand blast dynamics. The

movement data can still be used to translate ore polygons for ore control, but this may be a

lesser priority when deciding where to install the BMM®s. Outcomes of these results include:

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Determining optimum flitch digging heights for a multi-pass mining operation

The relationship between powder factor and horizontal movement

Quantify the variability of movement

Quantifying the movement profile

Understanding the movement dynamics in different zones.

Optimising blast designs, such as sub-drill and timing.

It is important to recognise that there are a number of zones within a blast pattern where the

movement is known to be different to other zones. These include close to all edges (within 2-3

blast holes from any edge, including the initiation centreline) and the body (away from edge-

effects). It is only valid to compare similar data, and depending on the specific objectives,

BMM®s may be concentrated in the body or distributed through all zones. The body zone

represents the greatest volume of most blasts so it is generally more important to understand

and monitor this zone, but the edges are arguably more interesting and provide unique

challenges for grade control. Regardless, the data will need to be filtered to compare like with

like.

The horizontal and vertical components of the 3D

movement are both important to ore loss and

dilution, but to varying degrees depending on the

orebody. It is therefore important to gather a good

spread of data throughout the depth of the bench to

gain an understanding of the horizontal movement

profile, i.e. the shape in section. For multi-pass

(flitch) mining operations, this information will

enable a determination of the optimum flitch digging

levels. The diagram on the right shows an example

of installing multiple BMM®at the base of each flitch

for a four-pass mining operation (the dashed lines

represent the pre-blast flitch levels). Several holes in

a blast could have BMM®s installed in this way, but

the separation rule must still be applied to BMM®s of

the same colour.

Concentrate on the body of the blast.

Ideally, select blast(s) with similar rock along the entire length.

Ensure the same initiation timing for all locations. If the blast has to be initiated with a

V, then the centreline of the V must be more than 3 rows from any BMM®and the same

timing on each side of the centreline.

Select the depths to give a complete coverage of the bench height, including sub-drill.

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Since blast movement is quite variable, one of the most important criteria when planning a

project to gain an understanding of blast dynamics, is to control the variables. For example, the

size and shape of patterns (bigger is better), initiation timing (delays and tie-up), rockmass,

explosive, hole diameter, and front face condition. This will minimise the variation and enable

more specific conclusions to be drawn from the results. Although we can plan for predictability

within a blast, there are also several factors that are difficult to control or out of the blast

designer’s control. These factors could include:

Change in material characteristics —rock type, structures, oxidation state

Inconsistent mass of explosive being loaded into each hole

Variation between batches of explosive

Variability of explosive delays.

Therefore it is valuable to quantify and understand the variability when interpreting results

and tests can be configured specifically to investigate this. To understand the amount of

variability within a blast, the following guidelines are recommended.

All monitoring holes within the body of the blast.

Install the BMM®s at the same depths in every hole –use multiple BMM®s per hole as

required.

Conduct a number of blasts to quantify variability at different depths —at least one in

the stemming and explosive zones respectively. Depending on the scope of the study, it

may be advantageous to either do these blasts with the same depth as used in the 3D

movement tests or to select different depths.

2.5 Monitoring Holes

When deciding the location and depth of a monitoring hole in the blast pattern, consideration

needs to be given to its position to ensure the BMM®has the greatest chance of survival.

To minimise the chance of BMMs being destroyed, it is very important to get them as far from

a blasthole as possible. The maximum distance from a blast hole is shown at position 4 in the

diagram below (equidistant between blast holes). However, this location can be less convenient

to drill and may suffer cave-in due to equipment driving through the drilled pattern. Positions

1-3 may be better from a production perspective (half way between blast holes). Whichever

position you choose, it is important to get it close to mid-way between blast holes.

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Below are some further suggestions relating to monitor hole placement and hole depth.

There is no need to drill monitor holes to the same depth as blast holes. Only drill to just

below where you want to install the deepest BMM®in that hole (if more than one). Holes

that are deeper than necessary waste drilling resources plus it takes time and effort to

back-fill them before installing the BMM®s.

It is often a good idea to put something in the hole collars to prevent them from filling

or collapsing as equipment moves around the bench. Gasbags are best but traffic cones

can also be effective.

Communication with the shot crew is important. Ensure monitor holes are clearly

marked so that the hole is not stemmed or loaded with explosive accidently. Drill and

Blast should be aware of the importance of correct placement of the monitoring holes

within the blast pattern.

2.6 Monitoring Hole Diameter

The BMM®s are 98 mm diameter so it is possible to get them into a 102 mm (4”) hole but only if

the ground is competent and the hole is clean. The minimum recommended hole diameter for

effective installation is 115 mm (4.5″).

3BMM®INSTALLATION

3.1 Introduction

Installation of the BMM®s is arguably the easiest of the monitoring tasks and with good

planning and communication with the drillers and blasters, it can be done very efficiently, with

little impact on existing workloads.

The BMM®s have a limited transmission time so it is critical to know the blast time. The signal

from each BMM®is constant for about 10–12 hours and then begins to decrease and finally stops

after about 36 hours. The signal strength is used to calculate the depth, so the depth, and hence

the vertical displacement, will only be accurate if it is located within the 10–12 hour window.

To provide more flexibility, there is the ability to program the BMM®s to start transmitting up

to 36 hours in the future. See Section 3.3 for more information on this topic.

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The limited transmission time and the fact that a BMM®can’t be switch off once activated,

means planning and communication with the drill and blast department is critical. One must

be reasonably certain of the blast time before installing BMM®s into a blast. Installing the

BMM®s as close as possible to the scheduled blast time minimises the chance that the blast will

be delayed.

3.2 Installation Procedure

Installation of the BMM®s consists of five basic steps:

i. Measure the depth of the hole

ii. Activate the BMM®

iii. Drop the BMM®into the hole

iv. Read the signal strength and record the BMM®s details on the blast plan

v. Backfill the hole.

WARNING The BMM®cannot be switched off once activated with the

BMM On button.

The Detector will be affected by electromagnetic interference from

certain equipment and vehicles. This usually manifests as unusually

erratic signal strength (‘noisy’) and/or elevated signal strength on the

Detector. There is a usually little interference once in the pit, unless a

source is close to the Detector. Known sources in the pit include: survey

GPS controller (if very close to the LCD), some vehicles (a few metres)

and electric shovel power cable (~10 m). There are no issues with

mobile/cell phones.

Make sure you have all required equipment before departing to the pit.

Detector and Activator

BMM®s —take 1-2 extra

Tape measure with weight suitable for measuring the depth of the monitor holes

Map of blast pattern and planned BMM®locations

Pencil or pen —to write on map

BMM®Mesh Bags —if wet holes are expected (see Section 3.4)

Shovels —to backfill holes if required

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