EXPLOSIVE USAGE OPTIMIZATION USING AIR BAG

Brief on Blasting Design

Blasting operation is one of the most important operation, looking from the capital influence on operation cost, the important of Blasting result on downstream operations and the place of safety. Most mine and quarries are not sensitive enough to understand the principle of Blasting operation and it significant in mine profit margin, because all Blasting is Blasting to them provided the ore ore industrial rock mass is broken down.

Some of the blast design by operators in common quarries around Africa and others continent where small scale miners and Artisanal miners dominate are extremely poor and give low Explosive Energy ultilization.

It has been proved by many research that poor blast Design with lack of agreement between the blast parameters like burden, spacing, stemming length, subdrill among others will definitely produce poor fragmentation with high environmental illness such as ground vibration, airblast, noise, flyrock among others.

Giant Africa mines expecially Nigeria mines like Dangote, BUA, Freedom Quarries, Fanalou Quarries, Geo-works Quarries, Stoneworks Quarries among others are making great different compare to other local Quarries handled by ASM. This Giant mines have great mine plans and design that help them in striking balance between the hypertensive parameters.

But nevertheless, most of them still under use Explosive energy and still haven't balance the variance effect between the controllable factors (burden, spacing,hole diameter, Stemming, e.t.c) and the uncontrollable factors (rock strength, discontinuity nature of rock mass, chemical property of rock among others).

Blasting operation is capital intensive as I had earlier explained in one of my published write up, the Effect of poor Blasting is not restricted to just loading and transportation but also stretch wings to downstream operations like crushing, grinding and Separation because libration begins from Blasting as Explosive energy not only break rock but also weaken the intermolecular bonds in rock grains.

Previous years ago I meant one of the giant blasterman in Akoko Edo local government of Edo state Nigeria, I was quest to ask him why using ANFO as the column charge and the reason for using it in abundant?

He replied as with this that, ANFO is a strength breaker Explosive, thou it is a low Explosive or better still Blasting agent, it assist and sustain High Explosive energy within the rock mass and ensure it saturate and weaken rock strength. This will reduce work on the processing machine by aiding easy comminution process.

Why air decking is likely going to yeild result that Stemming material decking!!!

Many never sieze from asking me this question concerning the reason why I think air decking will give better Blasting than solid material decking.

Talking about decking in Blasting operation we refer to the situation where innert material is place within explosive charge to reduce charge delay and also produce diversifer stand for the explosive wave.

At the point of detonation, explosive charge initiate generate fast waves which travels at a speed greater than the speed of sound in more than Seven times (>2100m/s), the wave energy perform the Major function of microfracturing (Slabbing). At the point of initiation, the waves are released to complete propagation after getting to the free face. The use of air decking (air bag) definitely provides closer free face medium for the shock waves which makes it reflects back quickly to support the lateral waves after longitudinal wave collision. In other words, the resulting wave generate from the air bag after collision support the rate of fracturing beyond the crushing zone. This support increase in fragmentation and proper breakage of the rock mass.

It also help to provide higher confining which gives the charge more avenue to release more explosion gas for casting and fragmenting.

In conclusion, Air bag help in the reduction of explosive charge weight per blast, reduce the maximum instantaneous charge per delay which directly minimize the blasting operation cost.

It also support good fragmentation; this advantage is important since theain aim of blasting is to get sufficient Run-off-mine at low cost for profitable production.

Also, good fragmentation assist in the minimizing of dilution and challenge of unexpected increase in transportation cost from mime2mill.

Finally, safety has always been the watch word and first thing on the dial of mining industry. It is of no doubt that blasting is one of the most dangerous operation in mining operation cycle due to the high energy involved. Such energy as that release form explosive can be destructive if not safely utilize and can be devastating if poor use. The use of Air bag is one of the cheapest way to ensure the safe and profitable use of explosive.

Remember, Mining the ore safe is better than mining it profitably when the mining act and condition is unsafe. Ensure bis safe and profitable to avoid any for of accident which is the end product of hazard. Eradicating principal hazard to avoid principal threatening condition works like magic for those mining industries that put all mining safe and profitable strategy in place.

Maje safety first.

Thanks and Happy mining

ASM Needs help with safety

Blow out and flyrock is one of the evidence of poor and unprofessional blasting operation.

This can result from poor steaming and overloading of holes and sometimes result from low charge weight.

Energy is define as the ability to get the job done, the capacity to overcome the energy barrier.

There are many ways to generate energy but for rock breaking, the use of explosive had been the most adopted means since 1900s. In every proper work done, professionalism is very important. Lack of professionalism result into disaster and accident. Since the aim of mining is to promote safety first through new innovation, inventories and safety management system, then the call for help to ensure this is achieve in Artisanal and small scale mines is important.

Fact

The artisanal miners will keep existing in the stope of mining operation as they has always be because if the following reasons:

1. challenge of start up capital in developing countries to set up large scale mine

2. large scale mines will for sure always go for huge deposit, neglecting placer/alluvial deposit with low grade and non uniformly distributed. #mining 

Artisanal miners need assistance and help to ensure all operations are safely carried out.

Reason for urgent response

The approach adopted by the low income Miner to extract alluvial formation tends to affects the environment, damage water, land and even air through pollution and acid mine drainage.

Aside from this hazardous effect, small scale mining operations working with insitu hard and soft rock sometimes engage in drilling and blasting operation.

This operation in most ASM mines are performed with less consideration to safety. Getting the explosive charge quantity that will break the rock down safely without any environmental effect becomes important. likewise understanding the behavior of this explosive generated shock and gas energy also contribute to ensuring the Earth crust condition after blast remain stable and safe for human existence.

Th question now arise that who will sensitize the ASM and other quarry workers about the safe design and execution of blasting in Most Africa and less developed country.

Explosive is for peace and not war

Let get the across to the ASM operators about the best and safe usage and handling of explosive but during transportation, storage and usage.

the mission is to go for safety first!

As all the mining worker must return back home to enjoy nice dinner with their family.

blasting aim to support innovation, development, and human existence beautification.

mine the ore safely

get the ore peacefully

support peaceful and safe mining

#campaign_Against_unsafe_Blasting

 #environment #safety #drilling #africa #innovation 

Blast it safe to safe your world

Brief Summary

We must be alive to get all the money we are dreaming and thinking about! Mining still remains the most lucrative business in the world with high impact on Technology Development.

But the level of safety at the blasting operation cycle is minimal due to lack of sensitivity despite millions of Research work on this area.

This article was put together By Taiwo Blessing Olamide to sensitize the World mining sectors on the need to get involved in small scale mining to avoid unforeseen disaster.

What blasting may look like if picture from a perspective

Check below picture to have a view of what blasting is and what quantum physic can be involved in getting the rock fragmented

instantanous casting of fragments from overloaded blasting

Article

Looking are many developed countries it becomes clearer that they are all functioning well in their large scale mines. Likewise the developing countries, they tends to have some level of success in the record of medium scale mining operations.

Taking a look at the small scale mining operations as a case study Nigeria and other Africa countries, most mining operations in artisanal and small mines are poorly monitored and design. Professional Mining engineers are kind of Given up on the local miner, instead of any form of assistance they set their compass on the direction where large mining thrives. Less attention has given to help, improve and monitored small mining operations because the large scale miners have all Earth equipment to get their mine cleaned and discretely planned.

This become my view and concern! That, though the small scale mining operators are abundoned but with time the large scale mines will soon fold up, reach the ultimate limit and come back to the small scale sites. In addition, the small scale miners might later cause damage to the Earth and bring aftereffect implication on the large scale mines and human existence at large.

Small mining firms are known for less safety concerns, less safety management and supervision.

looking from the direction of Blasting, small scale miners are not much concern about the effect of flyrock and it's causes, better worth how to minimize it.

They are less concerned about the effect of timing on blast fragmentation (Appreciating Professor Takis findings at Queen's University). This sectors are less aware about the aftermath effect of generated shock waves from excessive powder factor, how it can over break the wall, damage the unmined rock mass and reduce the stability of the mine slope completely.

Though we have our own mine safe and try not to show concern for the poor miner, neither do we have any plan to train, sensitize them on what they don't know. Before we try to mine for our own profit and mine development alone is time to begin a sustainable mining that check out others operation to avoid the future damage which is possible of affecting our mother Earth.

The ground itself has a stable stress field before the disturbance team called miner came, the induce stress resulting from excavation is capable of shifting all stress equilibrium into stress instability if proper control is not put in place. Each tectonic plate has it own respond to all the generated dynamic waves. But a time shall come when the plate will no longer be accommodative, then what can be done?

prevention is better than cure!

say no to poor blasting

support through mentorship, surveillance and supervision all blasting

manager must now be concern about the report of all blasting, not just how much tonnage do we get but how safe was the blast.

safety first

Campaign Slang:

Before Fire in the Hole, Safety must be assured

Mine is safe

Blast it safe

Check!! Check!! And recheck before putting fire

The beauty of a Good blasting is safety: Go for safety to safe the world

        Sir Dyno Nobel

Why Blasting?

The rock Mass contain the ore mineral which is the mining engineer major target. Mineral resources are inevitable material needed for Technological innovation and national development. The place of this mineral resources can not be suschanged neither can it be replaced with synthetic materials.

By definition, I describe mineral as solid inorganic naturally occurring matter, that is been generated during magma eruption through sufficient time cooling and interrelate and exchange of element in the liquified rock lava.

The mining engineer as well known by other disciplines involve themselves in getting the ore from the Earth crust and refining it to fit end user's need.

The extraction process begin from altering the Earth land form through wide range of excavation and degredation attempt to get the so called overburden material removed in order to gain access to the enriched ore vein.

Emphasis on Bowen series reaction*: During formation of mineral, the cooling time tenders to affect the location of each precious mineral, some tend to form at deep depth due to the slow rate of cooling. Slow cooling support fast  and bigger growth of mineral size. The bigger the mineral accommodation, the higher the economic value. This condition makes the ore deposit locate in strategic position where need arise for size reduction to ensure the valuable minerals are easily separated.

Ore is an accumulation of valuable mineral existing in an economic quantity. This ore is what the Mining engineers want and it existence can only be found in rock Mass. In addition, the ore block do not exist alone as an entity but usually bond with the parent rock which can be igneous, sedimentary or metamorphic rock.

The host rock may exist as outcrop or deep depth rock Mass which becomes impossible to move directly to the processing plant for libration and separation process.The quest bring about ways to reduce the rock mass and free the ore block for further ore dressing. Transportation of run-off-mine is capital expensive and also the mine-to-mill operation cost is high!

Innovation attempt in the 1900s to begin the use of black powder aim to assist and improve mining operations.

This improvement covers the production and cost minimisation.

Likewise the 1960s Innovation of detonation cords and cap by the Dyno Nobel group assist the safety and effective use of the energetic material.

Blasting Is important but must be safely carry out to ensure the reason for blasting is not been blasted.

Let your manager be aware!!!!

Campaign against unsafe Blasting

Say no to poor and unsafe blasting operation.

Both civil works and mining operations required blasting activities to get the rock Mass size reduced or get the obstructing rock casted out from the road map.

Using explosive in a bit to generate the needed energy can be highly dangerous if not properly handled 

Many quarries had begin blasting long year ago without any plan, without any post blast check, without any preblast planing. Fire work is not good when out of hand and this can happen when excessive powder factor is use or there is existence of misfire due to unforeseen circumstances.

Blasting is much more dangerous and must be done safely.

This campaign is to sensitize all quarry owner, manger and mining engineer on the need to put proper consideration on proper and safe blasting.

Advice to mining industry:Things to enhance your blast safety

1.Get the blast design right

2. Conduct your preblast checking and take note of various structural features that needs design attention

3. Identify any hole with fractures and note any existing dyke and sills as intrusion

4. Supervise the handling and transportation of all explosive material from magazine to site and from site back to the magazine

5. Monitor all explosive usage and ensure due procedure is follow during charging and chaining to avoid unnecessary fire cut, misfire and other arising issue with blast impulse distribution.

6. Provide good policy for you blasting team and monitor all unsafe act and conditions with instant action

7. Give all blasting operation special team for emergency response and safety team.

8. Ensure all clear surveillance is made available and active for all blast operation.

Let make blasting a good blasting and not a Killing or ground damaging blasting.

We want the ore for the people, then we must not create dead trap for the people through landslide, wall fall and holing due to over break during blasting.

The explosive energy is for peace and not for war

#campaign_against_unsafe_blasting

#GiantMiner

Campaign Against Unsafe Blasting: Management responsibility (1)

#campaign_against_unsafeBlast

Brief Introduction

It's clear that unsafe blasting is the father of unwanted occurrences. This make all move in the wrong time give birth to the wrong event. All mining operations must be planned properly before in site action.

A look at explosive energy

 Explosive energy distribution is almost a stochastic  discrete event, the explosion and detonation energy can sometimes be unfamiliar if there is change in rock property stimulation and expectation. Let all blasting put needed factor of safety in place to account for unexpected entities. Rock Mass as a discountinous, heterogeneous, anisotropic and non elastic material host the ore, the unmine rock form the supporting body; damaging the supporting rock is a call to hazardous events. The energy generator is the explosive, but the explosive will always remain calm until the stimulating wave is in touch with it. As mining engineer in this new year, let all our relationship with explosive but in usage, storage and transportation give positive result.

THINGS TO DO

 Balance the rock properties with the explosive energy and make proper adjustment to the controllable parameters in order to ensure all intrinsic conditions had been handled. The blasting result greatly affect the mine management plans, it control the downstream operations and alter the productivity rate.

Both safety and profit must be considered when we are planning our blasting. The high powder factor affect mine cost per ton, and also produces unsafe conditions like, ground vibration, flyrock, over break, backbreak, ore grade dilution, noise, dust pollution to mention few. This year operation in the mine must be different completely.

 Generally, both Artisian and small scale miners (ASM) and Large scale miners (LSM) must put the safety of equipment, personnel and mother Earth into consideration.

 Giant miner advice to mine managers:

Dear mine manager, 

I understood all managers concern about profit and your interest in high production rate so as to meet up with the customer's demand. I am aware that all managers make use of all available managerial and leadership's skill and controlling techniques to ensure the mine operation cost is minimized. In fact, managers have decided to become the blasting engineer in other to reduce all blasting materials, supervise the loading and silent the professional mining because he will always say "This is not safe sir!". As good as profit, profit without safety is fraudulent.

Truly the wall has never fail since, despite the use of unquantifiable explosive charge. In fact, the bench wall is full of multiple joint sets and fracture but yet the mine is still producing. As fine as the state of your mine now because you are producing, do you know the mine slope will definitely fail one day!

 That the wall is standing does not assure the wall is stable!.

 Please, let not the management decision side line the place of safety. The profit is good, but please let the safety be first. 

The wall is dieing, the failure conditions might not be completely met, but you can imagine the wall standing and suddenly little vibration collapse all and cover the mine.

To support our campaign against unsafe blasting, all mine managers must ensure the management decision and blast proposal/design be thoroughly review and approval be granted base on safety first. All mine operators who consider anyone able to supervise to be more effective and efficient than competent Mining engineer is totally wrong! 

Mining engineer is needed to ensure the decision made about the blasting is right for the deposit at every Time. I know the company needs low paid employee but putting mining engineer aside to get electrical engineer or builder as mine manager is inppropriate. The rock behavior is not like current and voltage any way, rock is not cable but a DIANE material

Rock don't obey Kirchoff law at all, not all the release energy entrying a rock Mass node will get out at the same intensity, the heterogeneity of rock call for rock doctor who can diagnostically prescribe the right charge for the right explosion. 

Please dear management, give room for professional mining engineers to carry out there jobs. The mine is build base on plan, do your mine have any plan? The blasting conditions is check to prepare for the future events, do you have any post and preblast checking team?

No, we don't is probably the answer for more than 70% mine in Nigeria, maybe 50% for mines in other Africa countries.

What blasting team do you have? Do you call people who distribute explosive the blasting engineers? I bet you, those team  doesn't even understanding when the Earth is bleeding, when the fragmentation is good or poor, when their is misfire; that is not what Council that regulate engineering activities called Engineering team. Those are event oriented Team who don't show any concern about the aftermath effect. The real Team prepare a good design, implement and supervise the execution of the plan and also check the results from the plan to ensure good recommendation is drawn from it. Good blasting team also ensure all the mine is safe before, during and after blasting.

This is a call back to the real mining, when you fail to plan the mine, the mine will definitely experience premature closure. Let all manager reorganize their company policy, Safety management system and working structure.

The mine Team should be working with a clear blue print, not just work with the idea of getting the ore out by all means; whether safe or unsafe.

Decide to put safety first in year 2022!!!!

Fire in the Hole, charge in the rock, energy and waves within rock grains.

Happy mining

Say no to poor use of explosive

Say no to unwanted blasting event

Use explosive for peace and not for war

Let us mine the Earth safely

Thanks

Appreciate from Taiwo Blessing Olamide (Giant miner) goes to all mining engineers who ensure and see to the proper implementation of mining laws and regulations.

Let us mine the mine and not dig the ground.

Thanks to USA, CANADA, AUSTRALIA, SOUTH AFRICA mining engineers. I salute your great work and practising.

Give zero tolerance for unsafe act and unsafe conditions.

Overbreak: Result of poor Blasting

                        A Technical overview of Overbreak

B.O. Taiwo*

Giant Miner

*Graduate of Federal University of Technology Akure, Nigeria 

author's mail: taiwoblessing199@gmail.com

 

Abstract: The presence of boulders in the blasted muck causes not only loss in production, but also increases the cost of hauling. In another words, the cost and efficiency of mucking, loading, and Comminution operations (crushing and grinding) will be highly altered by the outcome of blasting operation. This article give detail explanation about the causes and effect of overbreak during blasting. It point out the ways to control and minimize blast overbreak and give recommendation on the ways to improve blasting operation and safety. The safety of the mine is important to ensure guarantee of life, therefore generation of overbreak on the mine face affect both profitability and safety status of the mine. All possible means and design must be put in place to mitigated and control the generation of overbreak during blasting operation. Rock mass with existing fractures and joint set likely become detrimental in the present of overbreak fracture, such become unstable and can undergo plane or wedge failure if all require conditions are fulfilled. The ore require high grade status to guarantee high economic value, external dilution resulting from overbreak may increase dilution resulting into increase in haulage cost and processing cost. Overbreak floor also support the out flow of ground water into the mine and demanding for de-watering operation if not result into Acid Mine Drainage or total closure of mine. Overbreak can therefore be control from the Pre-blasting stage which involve proper understanding of the ore deposit geological condition, ground water condition, explosive material knowledge among others. Special blasting techniques like pre-splitting, post splitting, line hole, cushion blasting, air decking among others can also be use to control overbreak in mine wall, toe and face. 

 Keywords: Blast, overbreak, fragmentation

      

1. INTRODUCTION

The profitability of blasting operation depends upon the ability of the Mining Engineer to produce fragment size distribution as close as possible to the optimal range for downstream operations. In addition, from practical standpoint, oversize is defined as size ranges greater than the crusher’s gape and therefore requires secondary breakage before further handling. In most hard rock mining methods, drilling and blasting are the most widely used method of fragmenting the rock for handling (transportation and stock-piling) (sang and Katsuhiko, 2004). Sang and Katsuhiko, (2004) noted that, an optimal blast is that which yields the specified fragmentation size distribution at safe, economic and environmental friendly manner. On the other hand, a poorly conducted blast would typically end in poor fragmentation and may generate adverse effects like fly rocks, ground vibration, air blast and back break (Nassib et al, 2016). Nassib et al, (2016) also discovered that blasting operation is capital intensive due to the following; need for rock mass reduction to smaller size ranges, efficient use of explosive energy at high safety level; and control of blasting to avoid oversize materials. Therefore, there is need for proper blasting optimization using the controllable factors which can be predicted using machine learning packages and other empirical formula (Tiile, 2016).    

The primary requisites for any blast design is to ensure optimum results for existing operating conditions, possesses adequate flexibility and comparatively simple to use (Muhammad, 2009). Several factors affect the output of a blast, these factors can be generally classified into two; uncontrollable factors and controllable factors.  Uncontrollable factors are those that the blast designer has no direct control over. They are controlled by the intrinsic (DIANE) properties of the in-situ rock formation or ore deposit to be blasted. According to Konya and Walter (1990), these factors include: geology, rock characteristics, regulations as well as the distance to the nearest structures. These limitations usually require that the blaster makes correct modification to a standard design to fit the conditions of the in-situ rock conditions.

2. Blast OVerbreak  

 

Fig 1. Theory of blast Overbreak   

The chance of breaking rock beyond the design reference is highly possible during Blasting operation. This is known as overbreak, when the Explosive energy fractures the rock beyond the bench width. This is highly dangerous and even disastrous to both safely and profitability.Deep deposits are mined in benches to ensure easy access to the pit and support of multiple operations within the mine. The pit benches are design such that the height is higher than the loader boom height and selected base on geological condition and grade Control constraints.  Each bench width is designed such that it accommodate truck turning radius and it overall width, this is done with high consideration of grade Control and geological condition also to ensure discontinuity daylight is not supported and likewise external dilution is not supported. With all this in mind, the access road to the pit called ramp is also design, each with consideration width (Be in expectant of my lecture on pit design and ramp design). Over breaking the bench width beyond this design width will compromise the safely in place of bench wall stability and also affect production in place of dilution and poor fragmentation. 

 

Fig 2. Site view of Overbreak effect on mine toe (After ismge.org)

 

2.1 How overbreak occurred during Blasting

 

Muhammad, (2009) establish that blast design usually aimed at providing adequate fragmentation and ensuring that loading, haulage and subsequent processing is accomplished at the lowest possible cost. However, for optimum and efficient blasting performance, it is essential to consider critically the rock mass intrinsic properties. Rocks are usually characterized by several properties. The nature and properties of the rock mass vary sharply over short distance. It is therefore important that the influence of the rock mass parameters must be understood during the blast design process (Bhandari, 1997).

Overbreak begins from the blast design point, selection of Minimum burden distance must be done with good decision and rock condition justification. One important parameters that support overbreak is the wall burden distance. If this is small then the implication is to produce overbreak beyond the bench wall. Such occur because the Explosive energy (shock wave) is under use within the wall and have sufficient strength to proceed slabbing into the wall. Since slabbing is extend into the wall explosion will definitely fall rock beyond the wall Konya and Walter (1990). This follows the law of conservation of energy directly.

Other factor is the powder factor, this is the quantity of explosive designated to fracture a ton of the rock, this depends strictly on the charge weight per hole.

Pf = charge per hole ÷ Tonnage of rock fragment per hole 

From my short study of jack hammer drilling and Blasting operation, a single hole of jack hammer blasted is expected to produce nothing less than one (1) ton of the rock. Meaning if 5 holes are blasted,ore than 5Ton capacity truck will be produced. In situation where at the last hole row, the Explosive weight is more than that to fracture within the holes area o influence then, the unused Energy will definitely be use to overbreak the wall and create problem.

It's important to know that during Blasting of a single hole the burden is divided into two and distributed at the four cardinal direction of the hole to form the area of influence around the hole. Each blast generated energy from Explosive exothermic reaction is expected to be active within this area of influence. Placing our blast holes at the last bench edge should be done with respect to this understanding. This area of influence is define by 1ft/ms of shock energy traveling and it correspondence to the gas Energy explosion time and Rick casing time according to scholars research work in 1970s.  Explosive  shock and gas energy will always be active provided the area of influence is still yet completed. Over breaking in rock mass is easy to control when the place of understanding the blast parameters balancing is fulfilled. This can be prevent by increasing the burden distance.

Nevertheless, if design burden distance is much,  the implication is that,blast charge initiated will have more of the energy contained within the designated region thereby producing back-break or under-break as shown in Fig 1 which generate more oversize. Oversize or  Large Particle size materials  requires secondary Blasting or hydraulic breaker to Re-break the rock. This form a source of additional cost and waste of time which any company will never want.

Another factor that causes overbreak is rock mass Anisotropic and heterogenous nature. Rock consist of various Mineral composition, the response of each mineral components to Explosive energy is different due to their Strength and hardness variation (Bhandari, 1997). This heterogeneity nature makes rock and ore deposit Anisotropic to explosive energy. As a result of the this there will be change in fracturing along the rock wall. For instance, formation containing dyke or sill which are both geological intrusion, this intrusion according to the principle of intrusion which states that, "the rock been intruded is older than the intrusion itself". With the understanding of this principle if all things been equal in absent of weathering and leaching, the intrusion (dyke, batholith, laccolith among others) are proved to have higher strength than the old rock been intruded especially in case of metamorphosed carbonate rocks (marble and dolomite). Blasting such rock, understanding the geology of the area and deposit, with proper strata test, geotechnical mapping work  and observation during drilling will help to put good charge design in place to handle any variation in rock stratigraphy and lithology.

Other factors include discontinuity, Explosive property and conditions, misfire among others which I will explain in my full article.

 

2.2 Effect of Overbreak 

 

Some of overbreak effect are:

1. Produce rough bench wall

2. Support external dilution

3. Support slope and wall failure

4. Poor fragmentation and non uniform size distribution among other 

 

2.3 Ways to control and prevent overbreak

 

1. Proper Blasting design: making balance in blast parameters (burden, spacing, stemming length e.t.c.) Design

2. Proper study of formation geology and lithology during Drilling: This require the implementation of drilling log in mine, the drilling team should provide information of each holes clearly as observes during Drilling and from the drill cutting. Such include interception depth at which a hole lithology changes, the strength variation with depth as indicated by Penetration rate During drilling, collar condition and others.

3. Discontinuity information and joint set mapping to understand the insitu rock stability and competency status.

4. The place of powder factor control is also important and place of drill hole row alignment with design.

5. Preventive measure against misfire such has Explosive checking, proper loading and connection, hole water status checking e t.c should be intact.

 

Conclusion

 

The safety of the mine is important to ensure guarantee of life, therefore generation of overbreak on the mine face affect both profitability and safety status of the mine. All possible means and design must be put in place to mitigated and control the generation of overbreak during blasting operation. Rock mass with existing fractures and joint set likely become detrimental in the present of overbreak fracture, such become unstable and can undergo plane or wedge failure if all require conditions are fulfilled. The ore require high grade status to guarantee high economic value, external dilution resulting from overbreak may increase dilution resulting into increase in haulage cost and processing cost. Overbreak floor also support the out flow of ground water into the mine and demanding for de-watering operation if not result into Acid Mine Drainage or total closure of mine. Overbreak can therefore be control from the pre-blasting stage which involve proper understanding of the ore deposit geological condition, ground water condition, explosive material knowledge among others. Special blasting techniques like pre-splitting, post splitting, line hole, cushion blasting, air decking among others can also be use to control overbreak in mine wall, toe and face.  

References

[1]           Sang Ho, C. and Katsuhiko K. (2004). Rock Fragmentation Control in Blasting. The Mining

        and Materials Processing Institute of Japan , pp. 1722 to 1730.

[2]          Tiile, R. N. (2016). Artificial neural network approach to predict blast-induced ground

        vibration, Airblast and rock Fragmentation . Masters Theses. 7571.

        https://scholarsmine.mst.edu/masters_theses/7571

[3]           Muhammed, A. R. ( 2009). The Effect of Fragmentation Specification on Blasting Cost.

  Unpublished MSc Thesis Report, Queen’s University, Kingston, Ontario, Canada , pp.192-    

  200.

[4]           Konya, C. J. and Walter, E. J.  ( 1990). Surface Blast Design. Prentice-Hall Inc., New Jersey,

  USA , pp 125.

[5]          Bhandari, S. (1997). Engineering Rock Blasting Operations. A.A. Balkema, Rotterdam,

        Brookfield , pp 375