Blasting News Q2 2016

Blasting News VOLUME 25 ISSUE 2 2016

IN THIS ISSUE • Equipping Explosives Engineers and Technical Representatives at WEETR (Workshop for Explosives Engineers and Technical Representatives) • AEL expands South American base • Check twice, blast once: The importance of blasthole monitoring

Printed on 100% eco friendly paper

CAPTAINS OF INDUSTRY

Editor’s Note Welcome to our bumper second quarter edition of Blasting News. In this issue we focus on our latest innovative technologies and products in our quest to remain relevant to the market we serve.

CONTENTS 3

AEL CAPTAINS OF INDUSTRY: Meet Denvor Govender

4

AEL KNOWLEDGE SHARING: Equipping Explosives Engineers and Technical Representatives at WEETR (Workshop for Explosives Engineers and Technical Representatives)

8

AEL INTERNATIONAL: AEL expands South American base

10 AEL TECHNICAL CAPABILITY: Check twice, blast once: The importance of blasthole monitoring 14 AEL THOUGHT LEADERSHIP: Explosives Today 17 18 AEL IN THE FIELD: AECI showcases at Expomin 2016 19 AEL PAYING IT FORWARD: AEL partners with Northam Rhinos

In our captains of industry section, we introduce you to another member of our Executive Committee, recently appointed Denvor Govender, Executive: Supply Chain.

Meet Denvor Govender

Under our thought leadership banner, we present the latest instalment of Explosives Today, our technicallydriven customer publication, focusing on blasthole drilling and initiation patterns in surface blasting.

Our knowledge sharing segment, offers insight from our internal Workshop for Explosive Engineers and Technical Representatives by providing you with information on our latest featured products, latest product catalogue and stop blasting handbook as well as the top case study based on Assmang Khumani Iron Ore Cost Saving compiled by our subject specialist Robert Erasmus, Field Services Superintendent.

On the international front, our General Manager for business development in South America, Alois Kwenda enlightens you about the expansion of our global footprint within Latin America. As an international player we demonstrate our support to various markets with our presence at key industry events such as Expomin 2016 where we showcase our trail-blazing innovations and superior service offerings.

Under our AEL technical capability section, we profile our Mining Engineer, Manare Mokoatlo’s work on the importance of blasthole monitoring which she presented at the annual IOQ conference in April this year, empowering fellow engineers with invaluable insights.

To subscribe to Blasting News please visit our website www.aelminingservices.com and fill in the subscription form located under the Publications tab.

Enjoy your read!

Denvor is Executive: Supply Chain.

Role: Responsible for AEL’s Global Supply Chain portfolio.

Professional background: Denvor joined AEL in 2014 as Global Supply Chain Manager. With over 22 years of work experience in Global Supply Chain, International Logistics and Global Trade, he has worked at some of the largest multinationals which includes Orica Mining Services.

Denvor holds a BCom degree in Supply Chain Management and post-graduate qualifications in Business Management and Procurement & Supply Chain. He completed an EDP- Strategic Leadership at the University of Cape Town and the AECI SMDP at GIBS Business School. Denvor is also a Certified International Supply Chain Professional (IPSMI) and holds a MBB in Lean Six Sigma (Japan).

Eubulus Pillay Cover image: Mirny, Sakha Republic, Russia

Denvor Govender

Contact Details: Eubulus Pillay - Editor Tel: +27 11 606 0313 eubulus.pillay@aelms.com www.aelminingservices.com

Disclaimer This publication does not necessarily reflect the views and opinions of AEL Mining Services Limited management. The copyright to this publication rests in AEL Mining Services Limited. Other product and corporate names used in this publication may be trademarks or registered trademarks of other companies, and are used only for explanation and to the owner’s benefit, without intent to infringe.

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Blasting News I Second Quarter 2016

Blasting News I Second Quarter 2016

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AEL KNOWLEDGE SHARING

AEL KNOWLEDGE SHARING

Equipping Explosives Engineers and Technical Representatives at WEETR (Workshop for Explosives Engineers and Technical Representatives) AEL’s WEETR presents an opportunity to emphasise the company’s values and our relentless focus on innovation and commitment to staff through sharing insights on the latest technical methods and projects.

This year’s theme for WEETR was Simplexity - technology made simple, fast precise! Simplexity defines AEL’s capabilities in terms of products and services. We offer simplified solutions which are designed and developed for highly complex mining conditions.

Our Values Aligning to AEL values of BIGGER (BOLD, INNOVATIVE, GOING GREEN, ENGAGED and RESPONSIBLE), WEETR focused on “Being Innovative”.

At the helm of AEL’s innovative spirit, is our R&D department which plays a vital role in keeping our global operations on the frontier of technology with the delivery of groundbreaking innovations. The R&D team is actively involved in partnering with our Mining Optimisation team and our AEL engineers to develop products and solutions, tailored for specific mining applications.

Simplexity achieved through featured products and services at WEETR 2016 Aligned to our WEETR theme of SIMPLEXITY, our featured product range showcased AEL’s cutting edge

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innovations that aide customers to optimise their operations. AEL’s simplified mining solutions are designed to respond to our customers’ complex mining conditions.

offer numerous benefits in support of conventional explosives in certain applications.

Surface Mining Innovation at its best! AEL’s Surface Bulk Explosives are one of the best researched and developed formulations currently in the market.

The following new generation products offer ease-of-use and desired outcomes to the customer.

The Eco range of products The eco-range has been developed to optimise blast results delivering value throughout the surface mining sector. The substitution of recycled oil for diesel in the emulsion results in an environmentally friendly range of products helping to simply reduce environmental impact.

Management of Blast Generated Gasses in Surface Blasting If NOx Fumes are a problem, AEL has a simple solution. Blasting produces a sudden localised release of gases with potentially high concentrations of (Nitric Oxide) NOx. Such gas emissions pose a health risk if people are exposed to them before the fumes can dissipate. Causes of fumes from blasts include emulsion formulation deficient in oil content, or rich in ammonium nitrate content (oxygen rich/positive) or poor diesel absorption by ammonium nitrate prill.

InstastemTM InstaStem™ is a non-detonating, selfstemming rock breaking cartridge that is suitable for both soft and hard rock and concrete breaking. InstaStem™ Cartridges, by virtue of its nondetonating performance characteristic

Underground Mining

BIT The Blast Initiation Timer (BIT) is an electronic replacement for the pyrotechnic initiation systems targeted at the underground and surface mining industry.

Buffalo Booster This is a replacement to the Pentolite Booster and offers high VOD and detonation pressure similar to current Pentolite, with more forward pressure, lower friction sensitivity than Pentolite and easy lacing up ensuring better vertical positioning in the hole.

Electronics Our electronics offerings facilitate complex blasting projects to achieve a more precise result. Electronic initiation systems enable functions that traditional pyrotechnic systems lack. Besides the immediately obvious benefits of improved environmental blasting conditions such as reduced blast vibration and air blast; the system’s increased timing control allows for accurate blast modelling and optimisation of the initiation sequence, before triggering the blast.

DigiShotTM Plus DigiShotTM Plus is the Flagship system in Electronic Detonators. It is an easyto use, reliable electronic initiating

Blasting News News II Second Second Quarter Quarter 2016 2016 Blasting

system with remote firing capability and can be extended to fire very large blasts.

BlastWebTM The BlastWeb™ electronic initiation system is designed for underground environments where there is a requirement for ease-of use, limited user interaction and centralised blasting. The BlastWeb™ electronic initiation system is capable of initiating specific AEL electronic detonators.

Cutting Edge Software Our blasting science and software development offers simple solutions by looking at the mining operation holistically to ensure that the benefits are derived from improved efficiency in equipment, plant and beneficiation.

Delegates present at the plenary session

New marketing collateral Product catalogue We are proud to present our latest product catalogue showcasing our wide range of ground-breaking products and comprehensive range of services on offer to optimise customers’ operations. This new product catalogue has been compiled with care to ensure that it is an invaluable reference tool to equip you for the field.

Stope handbook launch The Stope Blasting Handbook has been used with great enthusiasm as a reference in mine blasting syllabi. This booklet has been compiled by AEL Mining Services to provide a practical guide for blasting in underground narrow reef mining operations. It has been revised to include new products and to give greater emphasis to critical questions.

AECI Chief Executive, Mark Dytor, opens the WEETR and highlights AECI Mining Solutions vision for the future

Case Studies AEL partners with customer in order to add value to their operations. We listen, analyse and understand the challenges of the customer and deliver to the required level of requirement using the right product mix, optimised delivery systems and a team of experts that are focused to deliver value.

We proudly present our wining case study at the WEETR entitled AEL achieves required cost savings at Assmang Khumani Iron Ore Mine, presented by Robert Erasmus, Field Services Superintendent Assmang who will be presenting this case study at the ISEE 43rd Annual Conference on Explosives and Blasting Technique to be held in early 2017 in Orlando, Florida. (See page 6)

Blasting News I Second Quarter 2016

2016 P ROD CATAL UCT OGUE Versio n3

Stope Blasting Handbook Version 1.1 I 2016

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AEL ACHIEVES REQUIRED COST SAVINGS AT ASSMANG KHUMANI IRON ORE MINE CASE STUDY

CONTACT Robert Erasmus Field Services Superintendent Assmang +27 27 82 739 6470 robert.erasmus@aelms.com AEL MINING SERVICES 1 Platinum Drive, Longmeadow Business Estate North, Modderfontein, 1645, South Africa www.aelminingservices.com

CASE STUDY

Total saving each month on drilling and explosives at Bruce Mine.

CONTACT Robert Erasmus Field Services Superintendent Assmang +27 27 82 739 6470 robert.erasmus@aelms.com

BUSINESS CHALLENGE AEL in the Northern Cape was awarded the Assmang Khumani contract in May 2015. At the time of the tender the mine requested that ore be delivered in a “lumpy” form as they were experiencing significant losses due to fine ore. It was identified from the start of the contract that the Burden and Spacing parameters were too small. Initially, the Ore burden and spacing parameters were 3.5m x 4m, and in the Waste 3.5m x 3.75m.

These parameters in conjunction with AEL’s doped emulsion initially resulted in the ore being blasted too fine which indicated an increase in the burden and spacing parameters was necessary. The previous explosives supplier had attempted to increase burden and spacing but had been unsuccessful in achieving the required fragmentation, therefore the expectation from Khumani for AEL to be successful was high.

AEL MINING SERVICES 1 Platinum Drive, Longmeadow Business Estate North, Modderfontein, 1645, South Africa www.aelminingservices.com

Over the period from July 2015 till March 2016 (9 months) AEL have saved King Mine a total of approximately R102 million. R32 million of this was on explosives, and R69 million on drilling.

Total saving each month on drilling and explosives at King Mine.

The main challenge that AEL faced was the decrease in the Iron Ore price, resulting in a Section 189 being implemented on the mine. This required drastic cost reductions specifically in the drilling and blasting operations.

SOLUTION This equates to a total saving of about R158 million over a period of 9 months for Assmang Khumani Iron Ore and is an on-going cost saving.

AEL started the optimisation process at Bruce Mine in July 2015, by increasing the burden and spacing parameters in 0.5m increments. AEL carried out quality measurements on each bench/block to ensure that all the holes were drilled according to plan and at the correct burden and spacing. This resulted in fewer drilled holes with the increased burden and spacing parameters that were identified in this process. The optimal burden and spacing parameters for Bruce Mine were finalised at 4.0m x 5.0m in the ore and 5.0m x 6.0m in the waste using SP235 Eco. The same process was then followed at King Mine, where the final optimal burden and spacing parameters were finalised at 4.0m x 4.5m in the ore and 5.0m x 6.0m in the waste using SP235 Eco.

Digging, loading and hauling was more efficient due to the “lumpy” fragmented rock. Optimum fragmentation leads to more cost saving, this cost includes the reduction in fuel for moving the fragmented rock and also an improved efficiency on the crushers and mills. Due to the improved fragmentation (more uniform and less oversize), more efficient loading with fewer haul trucks was realised. Due to contractual negotiations still in progress, a Rand based saving cannot be specified at this time, but a potential bonus pay out from Khumani to AEL may be granted when the contract has been finalised and signed.

In March 2016 the sub-drill at Bruce Mine was reduced to zero as it had been identified that the geology did not require sub-drill for good floor conditions. This would result in significant savings in drilling costs.

Following a month of trial blasting with zero sub-drill, Bruce Mine signed off on satisfactory floor conditions and is happy to continue with no sub-drill at this mine. The following step is to implement a similar project at King Mine.

NEXT STEPS Change the down-the-hole product and/or timing to improve the fragmentation quality to the mean size that the client requires.

OUTCOME Over the period from July 2015 till March 2016 (9 months) AEL saved Bruce Mine a total in excess of R56 million which encompasses saving in explosives as well as drilling.

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Blasting News I Second Quarter 2016

Blasting News I Second Quarter 2016

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AEL INTERNATIONAL

AEL INTERNATIONAL

AEL expands South American base explosives and specialty chemicals

AEL aims to increase its supply of

manufacturer AECI, it is important,

electronic blasting systems and bulk

specifically because of the continent’s

explosives to South American markets,

stability, its status as a major mining

particularly those of Brazil and Chile,

destination and the potential for new

where safety is the main issue for

mining projects even under the current

customers. Kwenda adds that the

environment of depressed commodity

company will also expand its on-site

prices.

technical support to maintain the highest safety standards and optimise

He cites the Brazilian mining industry,

mining operations for its customers.

which has remained competitive

a

end w K s i Alo

despite the fall of commodities prices

“Mining operations are looking

and the slowing global economy. Other

for suppliers that not only deliver

South American mining industries

products but that can also come up

have displayed similar resilience,

with solutions that increase their

which, in conjunction with the vast

operational efficiency, which we can

mineral deposits throughout the

achieve using our suite of explosives,

continent, is indicative of significant

blast initiating systems and technical

business opportunity, he adds.

support through blast optimisation teams.”

Demonstrations, which focus specifically on electronic blasting systems, have been

Kwenda says growing AEL’s previously

AEL has increased its presence in South America, owing to the nature and resilience of the South American mining industry.

established base in South America

Kwenda comments that the company’s

through direct interaction with

expansion in South America has

customers is integral to the company’s

exceeded expectations, with it having

global expansion strategy. Such

participated in several tenders

interaction has been characterised

and conducting demonstrations

by increased attendance at South

of electronic blasting systems for

American mining exhibitions and

potential customers.

events, as well as several meetings with potential clients.

AEL GM for business development in

To date, AEL has performed two blasting demonstrations for copper

South America and West Central Africa

AEL has previously supplied customers

mining clients in Chile and expects to

Alois Kwenda notes that, although

on the continent using distributors and

conduct two more next month. Kwenda

South America is a relatively new

other agents, but decided last year

notes that the demonstrations, which

market (compared with Africa where

to offer its full suite of products and

focus specifically on electronic blasting

the company was first established

technical expertise directly to ensure

systems, have been successful, as

more than a century ago and the Asia

high-quality supply and more efficient

they have led to renewed interest from

Pacific region, where the company

application of explosives on site, he

stakeholders in Chile and securing

has been established for a decade)

explains.

new clients.

for AEL and its parent company

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Blasting News I Second Quarter 2016

successful AEL field technicians on bench

AEL has consolidated its offices under

second year, is a mining exhibition and

International Mining Exhibition 2015

the AECI brand in South America;

conference for Latin America, attended

from September 14 to 17. The annual

therefore, the sales and distribution

by about 80 000 visitors and including

event was held in Belo Horizonte,

offices in Brazil and Chile trade under

exhibitions from 1 700 companies.

Brazil, and attracted more than 50 000

the AECI name. AECI Mining Solutions

Kwenda notes that even though

visitors.

brings together the group’s expertise

attendance had decreased this year

in the supply of products and services

due to global economic conditions, the

According to Kwenda the company

for customers in the mining sector.

quality of customer interaction was

intends to establish manufacturing

still significant, with many customers

operations in either Chile or Brazil

Kwenda and his team recently

and potential customers visiting the

within the next five years.

exhibited as part of AECI Mining

stalls and asking for meetings.

Solutions at the Expomin 2016 event, held in Santiago, Chile, from April 25 to

AEL under the AECI Mining Solutions

29. The event, which takes place every

banner, also exhibited at Exposibram

Blasting News I Second Quarter 2016

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AEL TECHNICAL CAPABILITY

AEL TECHNICAL CAPABILITY

Check twice, blast once: The importance of blasthole monitoring by Manare Mokoatlo ‘Measure twice and cut once’ is an old adage that every person who works with their hands has heard countless times, usually dispensed by their mentor as they learn the ins and outs of their craft. The learnings behind this phrase are to avoid having to duplicate your efforts, save time and eliminate any possibility of error in your results.

In the world of mining operations – where every cubic millimetre of ore and every second of uptime counts – this is especially true. However, some operations are failing to meet their potential by allowing poorly drilled blastholes to force them into duplicating blasts unnecessarily and ultimately hampering production in the long run. It is crucial that mines

measure twice, and blast once.

Blasthole surveying is a key part of blast planning and blast optimisation.

These two processes are vital in ensuring that every blast goes off without a hitch, that the optimal amount and type of explosives are used and that the right results are achieved.

When drilling blastholes, there are a number of technical and geological factors that can lead to an undesirable drilling pattern. From a technical aspect, excessive drilling and the use of worn out drill bits can lead to errors in blasthole structures while rock types and ground water can lead to drilling deviations.

Deviations lead to poor blast results, low productivity, safety risks and

environmental impacts.

Blasthole surveying can identify drilling deviations as well as burden lengths and drilling depths. This is crucial to operations because a small burden length can result in too much rock being blasted from the bench face while too long a length results in the explosive energy coming back up the blasthole.

Manare Mokoatlo presenting on blast hole monitoring at the IOQ conference

Borehole callipher log for measuring diameter deviations

Poor drilling practices

Hole being measured for depth

Poor fragmentation as a result of poor blast preparation

Blast hole angle deviation surveying

Using Boretrak™ equipment, for example, operations can check these factors as well as calculate drilling deviation from the design at fixed intervals. Boretrak™ comprises a control display unit (CDU) logger, a rack of rods, a probe and a gyroscope or gravity sensors. All of this equipment feeds into an interface which can represent the status of a

drillhole, removing all guesswork from blast planning.

Other equipment which is crucial in checking drillholes is borehole calliper logs, which comprise a tripod with a probe on a pulley which is lowered into the hole.

The probe is equipped with arms that can open out on command to measure the average diameter and average variance of the drillhole. In an ideal world, the hole should resemble a cylindrical tube – with smooth walls and an equal diameter throughout. In reality, however, there are often deviations. By measuring these deviations with the probe, blasting teams can determine the optimal amount and type of explosives that each unique hole requires or if the hole needs slight drilling adjustments.

A well planned and successfully executed blast has several benefits. It can deliver operation-specific fragmentation levels that result in improved productivity

BoretrackTM in action 10

Blasting News I Second Quarter 2016

Blasting News I Second Quarter 2016

and removing the need for secondary blasts. This is because the correct level of fragmentation reduces the levels of loading and hauling, and optimises plant operations by making processes such as crushing more efficient.

A successful blast also improves safety because it reduces the amount of flyrock, while its environmental benefits include meeting airblast and ground vibration limits.

While the information that surveying provides is crucial, it is what operations do with it that really counts.

Through thorough measurement and analysis, AEL can help operations take corrective actions to reduce downtime and unnecessary secondary blasts. By ‘measuring twice and blasting once’, mines can reap the financial and operational rewards of thorough planning and measurement.

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circles for effective fragmentation to occur. Figure 2 contrasts the arrangement of square drilling patterns with that of staggered

EXPLOSIVES TODAY

drilling patterns, for a Spacing/ Burden (S/B) ratio of 1.25:1.

Figure 1. Gas pressure and crack extension

The staggered pattern produces a more uniform distribution of fracture circles and thus more even fragmentation in the rockpile for the same powder factor.

In fact, optimum coverage is

Series 4 I No 15

obtained when the holes form equilateral triangles, but as can be seen from table 1 this pattern varies only slightly in coverage from the staggered patterns based on S/B ratios of between 1.0 and 1.5.

BLASTHOLE DRILLING AND INITIATION PATTERNS IN SURFACE BLASTING Part 1 By Henk Esterhuizen – Senior Mining Engineer

Figure 2. Bench coverage by blasthole fracture circles assuming constant powder factor and S/B ratio = 1.25 - Note: In the square pattern unfractured areas and excessive overlap between circles; In the staggered pattern, total bench coverage

Implications of Drilling Pattern The greatest potential for good breaking with the most extended

The layout of the drill holes, burden and spacing and ratio between them have an important effect on blasting results. In this issue a theme will be developed with particular reference to blasthole drilling and initiation patterns. In order to understand the significance of these patterns however, one of the basic mechanisms of rock fracture by explosives must be briefly considered.

12 12

Radial Fracture Under Gas Pressure

drilling pattern thus lies in using

other hand, promotes the formation

a staggered pattern having an

of longer cracks hence a greater When blastholes are fired

diameter plug of fractured ground,

independently a cylindrical ‘plug’ of

accompanied by minimal heave. The

broken ground is created around each

optimum burden is that which results

hole before movement of the burden

in a maximum of ground being broken

takes place. The diameter of this

and heaved into a rockpile loose

‘plug’ is determined by the pressure

enough to be handled by the available

of the explosives gases and the

loading equipment.

S/B ratio of between 1.0 and 1.5. The square layouts all give significantly less coverage. Note that if the S/B ratio increases beyond 2, the radial fractures reach the free face before Figure 3. Interaction of stresses from closely spaced blastholes fired simultaneously

result pressure is released earlier

time for which they act in the radial cracks and fissures to the free face as

Blasthole Drilling Patterns

illustrated in steps 1 to 4 in figure 1.

Seen in plan on the surface of the

becoming fully developed. As a

Table 1: Effect of drilling patterns and S/B ratios on area covered by fracture circles. Equilateral triangular layout = 100%

resulting in a smaller diameter fractured area and more flyrock.

S/B Ratio

Square pattern %

Staggered pattern %

There can therefore be little

1.00

77

98.5

benefit in exceeding an S/B ratio

1.15 Δ

76

100

of 1.5.

1.25

75

99.5

If the burden is small the gas is

bench, the fractured areas around

released very quickly and its unused

the blastholes can be represented as

energy is spent in heaving the

circles. It is logical to assume that

1.50

71

94.6

broken burden forward with great

every point on the surface must fall

Real as the benefits of staggered

2.00

62

77.0

momentum. A large burden, on the

within at least one of these fracture

patterns may be, they are less

Blasting News News II Second Second Quarter Quarter 2016 2016 Blasting

Note: Δ, equilateral triangle Blasting News News II Second Second Quarter Quarter 2016 2016 Blasting

evident in highly fractured 13 13

Single row fired with excess time

ground where the fracture

delay

planes seriously hamper the

•

broken rock buffer.

possible result as can be seen in

Lower ground vibrations and

figure 5.

airblast than the instantaneous

development of radial fractures.

If a single row of similar blastholes is

single hole blast, because energy

blastholes in high benches,

detonated in sequence with relatively

release and ground movement

drilling inaccuracy and hole

long time delay (e.g. several seconds)

are spread over a longer period

between successive detonations,

of time. Ground vibrations may be

the result will be different again as

higher than the single hole blast,

Identifying the right intra-row delay is

illustrated in figure 4.

because of the restraining effects

one of the key factors to predictable

of the broken rock buffer.

and efficient blasting. For a brittle,

Also, with small diameter

deviation can result in the pattern

Figure 4. Interaction of stresses from closely spaced blastholes fired with excess time delay

at the toe being unrelated to the laid out pattern on the bench. In these conditions, therefore, the merits of staggered patterns may

In general, this type of blast would

be outweighed by the convenience

produce:

of drilling square patterns.

Blasthole Initiation Patterns

• Figure 5. Interaction of stresses from closely spaced blastholes fired with optimal time delay

“Initiation” Burden and Spacing Spacing delay

elastic, homogeneous rock type, a short intra-row delay is usually

Better fragmentation than

Single row firing with optimal time

appropriate. In contrast, a porous,

the instantaneous single row

delay

plastic, highly jointed rock mass

blast, as cracks between

would require more time between

blastholes would not tend to

Alternatively, a single row of similar

of production blasts can be

link up preferentially. However,

blastholes could be fired in sequence

controlled by altering delay

fragmentation may be poorer

with a relatively small time (e.g.

Short delays promote a united effort

than the single hole blast

several milliseconds) between

between adjacent blastholes, tending

because there is no positive

adjacent detonations. In general, a

to maximise forward displacement

interaction between adjacent

delay interval of a few milliseconds

at the expense of fragmentation and

blastholes, and earlier-firing

per metre of spacing between

vibration levels. Long delays tend

charges may disrupt adjacent

adjacent blastholes will produce quite

to make each blasthole work more

explosives charges or the rock

different results compared to the

independently, reducing positive

mass surrounding them.

previous examples.

interaction.

the single hole or simultaneous

Optimal time delay is known as intra-

Results from a wide range of

single row blasts, as the rock

row delay, the essential difference

conditions indicate that the

displaced by the first holes

is that each blast hole charge is

appropriate intra-row delay for

to fire will come to rest and

detonated whilst the surrounding

conventional blasting is usually less

become a buffer which restrains

rock mass is pre-stressed but not

than 5 milliseconds per metre of

subsequent burden movement.

completely disrupted by the effects of

burden (as measured between rows

The opening of cracks from

earlier-firing charges.

of holes). The ideal delay for each

The overall performance

timing to vary the degree of interaction between adjacent blastholes. Whilst absolute values of inter-row and intra-row delays are important, the ratio of these times is also significant.

This can be explained by the •

following concepts (which are over-simplifications of a complex subject).

•

The intra-row delay controls interaction between adjacent blastholes and determines whether blastholes act independently or together.

•

The inter-row delay controls interaction between dependent blastholes, as it affects the progressive creation of new effective free faces during the blast.

•

The ratio of inter-row delay to intra-row delay controls the

14 14

Figure 6. Squared and staggered V-cut chevron patterns

geometry and orientation of new

muckpile shape and position.

free faces created as the blast

This is sometimes referred to

progresses. For a later-firing

as the apparent direction of

blasthole, the location, shape

movement of a blasthole or the

and extent of any effective free

overall blast.

face will depend on this ratio the direction and extent of displacement of the burden of each blasthole and thus the final

Blasting News News II Second Second Quarter Quarter 2016 2016 Blasting

Less forward movement than

earlier-firing charges may

•

of delay times. This influences

detonation of adjacent blastholes.

situation is clearly influenced by rock

also permit premature venting

Adjacent blastholes thus interact

properties, blast geometry and the

of gases from subsequent

positively, producing superior results

desired result, but 3 to 6 milliseconds

detonations.

because the explosives energy is

per metre of burden is recommended.

Less overbreak than the

released in a controlled manner

instantaneous row of blastholes,

and applied to the rock mass more

but more than the single

effectively. In fact, for any pair of

hole blast because forward

blastholes there is a unique delay

Fragmentation will be enhanced,

displacement is restrained by the

time which will produce the best

particularly in the toe region of

Blasting News News II Second Second Quarter Quarter 2016 2016 Blasting

Burden delay

15 15

blastholes towards the perimeter of

up in terms of visualising the correct

•

Explosives

damages that may be suffered, as a

the blast. The correct inter-row delay

initiation routes. Figure 6 illustrates

–

Characteristics, degree of

result of a party acting, or failing to act,

ensures that each blast hole has an

the difference between a squared and

coupling and decking

on the advice and/or recommendations

effective free face to break towards,

staggered V-cut chevron patterns.

•

Initiation system

given by AEL;1.4 accept liability for any

–

Surface or in-hole delays and

acts or omissions of its employees.

type of downline

Representatives and/or agents, whether

because preceding blastholes have broken and detached their burdens before

If we consider a square pattern of holes

the next dependent blast hole fires. This

as depicted in figure 6, it is evident that

•

Environmental constraints

progressive relief of burden during the

several different chevrons can be drawn

–

blast will affect the volume of oversize

through the pattern.

frequency

rock produced, although fragmentation

Air, ground vibration levels and

•

The desired result –

is often influenced more by the intra-row

Considering a single front row hole, the

delay than by the inter-row delay.

chevron which intersects the nearest hole

Fragmentation, muckpile displacement and final profile

in the next row, i.e. the hole immediately Results from a wide range of conditions

behind, defines the “VO” chevron. If the

We will develop this concept in future

indicate that the appropriate inter-row

angle of the chevron is flattened so that

editions of Explosives Today. AEL Mining

delay for conventional blasting is usually

it extends through the next nearest hole,

Services Explosives Engineers based at

less than 18 milliseconds (measured

this defines the “V1” chevron, and so on,

the regional offices are available to help

between rows of holes) but 12 – 18

figure 7.

and advise on this subject and the use

milliseconds per metre of burden is

of electronic detonators to achieve all

recommended for initial trials.

Chevrons through staggered hole

controlled blasting scenarios.

patterns are similarly defined but Ground and air vibrations are minimised

Figure 7. Chevron initiation patterns

References:

sideways distance is increased by half

similar to a single row blast. This is

the spacing. Figure 8 illustrates the

a direct result of progressive relief of

difference between a squared “V2”

This document is a new addition to the

burden during the blast, which promotes

chevron and a more flatter staggered

Explosives Today series. This document

lateral movement and minimises uplift,

“V2”chevron pattern.

replaces all previous Explosives Today

cratering and stemming ejection.

on this subject including Series 2. No 12:

Subsequent blasts are also likely to

Factors which influence the timing of a

have less potential for airblast because

blast

reduced overbreak means that front row

June 1978 Disclaimer: Any advice and/or

burden rock contains minimum cracking

Several factors which have a direct

recommendations given by AEL

from the previous blast.

influence on timing which should be

Mining Services Limited (“AEL”) in this

considered are:

publication, is given by AEL in good

Open or Closed

faith in order to provide assistance to

Figure 8. Squared and staggered V2-cut chevron patterns

•

Rock properties

the reader. AEL does not however: 1.1

– Strength, Young’s modulus,

warrant the correctness of its advice

chevron pattern causes the rock pile to

Open chevron patterns yield flatter, evenly

be concentrated in a central position, and

spread rock piles, that are well suited to

Chevron patterns are classed as ‘Open’

may provide a small bonus in terms of

front-end loaders. They also avoid the

structure

that particular results or effects will

or ‘Closed’ depending on whether it

fragmentation, owing to impacts between

possibility of a toe problem posed by the

•

Blast geometry

be achieved if AEL’s advice and/or

is desired to take V-cut in the bench

rocks projected from opposing echelons.

tighter breaking conditions of closed

–

Burden, spacing, bench height

recommendations are implemented;

patterns, and are rather easier to connect

and available free faces

1.3 accept liability for any losses or

or blast to two free faces. The closed

16

Copyright: All copyright that subsists in this publication together with any and all diagrams and annexures contained herein, which shall include all and/or any ideas, plans, models and/or intellectual property contained in this document vests in AEL. Any unauthorised reproduction, adaptation, alteration, translation, publication, distribution or dissemination (including, but not limited to, broadcasting and causing the work to be transmitted in a diffusion service) of the whole or any part of this document in any manner, form or medium (including, but not limited to, electronic, oral, aural, visual and tactile media) whatsoever, will constitute an act of copyright infringement in terms of the Copyright Act No.98 of 1978 and will render the transgressor liable to civil action and may in certain circumstances render the transgressor liable to criminal prosecution. This document remains the intellectual property of AEL. Intellectual Property: All ideas, concepts, know-how and designs forming part of this publication belong to AEL, save for where it is clearly indicated to the contrary.

look rather flatter, as in each case the

and can often be maintained at levels

Types and Features of Chevron Patterns

negligent or otherwise.

Blasting News I Second Quarter 2016

density, porosity and rock

Blasting News I Second Quarter 2016

and/or recommendations; 1.2 warrant

17

AEL IN THE FIELD

AEL PAYING IT FORWARD

AECI showcases at ExpoMin 2016

AEL partners with Northam Rhinos AEL is proud to have partnered with Northam Rhinos rugby team

Expomin has become a benchmark

For AECI this was a great opportunity

AECI team took this opportunity to

event for the Latin American mining

to promote our brand and the new

strengthen the relationship with

for several years. The team won

industry. The event allows industry

concept of AECI Mining Solutions in

current and potential customers

the Assupol Tournament in March

to focus on the widest range of

the South America mining industry.

during this event.

2016 at Loftus Versfeld Stadium

technological innovation while bringing

Additionally, being an exhibitor

together the mining sector’s key

reinforces our commitment to the

The AEL Latin America team

players. After 12 exhibitions since

region and builds confidence, in a

present at the event included

1990, it has become the largest

very conservative market, that we are

Alois Kwenda, General Manager

mining event in South America and a

committed about supplying Chilean

Business Development – LATAM &

worldwide benchmark event.

customers with explosives and

Central Africa; Alejandro Contreras,

The club boasts players employed

chemicals for mining.

Operations Manager – AECI

by the mines in the area as

enabling them to qualify for the Community Cup which will be a widely televised event.

Latam; Ignacio Humeres, Business

well as players from the local

80,000 professional, and more than

The AECI stand was visited by a host

Development Manager and Carlos

communities. Some highlights

1,700 enterprising suppliers from 36

of conference delegates, who sourced

Cammás, Financial Manager Latam.

countries around the world.

information about the company. The

include the team winning the

Expomin 2016 received more than

2015 Assupol Tournament (Blue Bulls Rugby Union), the 2015 Waterberg League, 2015 Limpopo Club Championships and the 2016 Assupol Tournament (Blue Bulls Rugby Union).

As a result of being the 2015 Limpopo Champions, the team will represent Limpopo Blue Bulls Rugby Union in the Gold Cup Tournament (previously called the Cell C Community Cup) in September this year. This is a prestigious national tournament for the top 20 teams in the country.

We wish them all the best to bring home the title!

The fully equipped interactive exhibition stand 18

Blasting News I Second Quarter 2016

Blasting News I Second Quarter 2016

19