In a blasting activity, fragmentation and flyrock are two fundamental consequences of blasting activities to be considered. One assessment of the success of a blast operation on the mine area is the achievement of a level of rock fragmentation as planned. In the mining company the fragmentation of the required blasting rocks must be in accordance with the capacity of the loading and transport equipment to be used after the blasting process.
A. Classification of rocks
- Frozen Rocks ~ occurs from the freezing of magma that undergoes the cooling process and forms crystals slowly.
- Sedimentary rock ~ is formed from the deposition process of weathering materials arranged in layers according to the order of deposition time.
- Metamorphic rocks ~ Occur from a recrystallization process that occurs at high temperatures and pressures. The properties of the resulting rocks depend on the rocks affected by metamorphosis and how far the deformations are related to the process.
Before conducting the blasting activity, a plumber should know the technical properties of the rock to be carried out blasting because it will affect the drilling activities for the explosive hole. The technical properties of the rock consist of:
- Hardness ~ is the durability of a smooth surface field of abrasion. Rock hardness can also be used to express the amount of voltage that causes rock damage. its characteristics are: solid, strong, and not easily broken
- Texture ~ Can be classified based on looseness, density, porosity, and grain size.
- Abrasive ~ i.e. Scraping by friction between two materials that have crushed power, or is a parameter that affects the wear of the drill bit ( dril bit) and drill dtell rod . To measure and measure the wear of the abrasive drill bit depends on the composition of the rocks contained in the rock.
- Rock Drill Ability ~ Is the penetration speed of the drill bit into the rock.
- Rock blast ability ~ Is a prisoner against blasting that is heavily influenced by the state of rocks. The hard and dense rocks of the blasting activity can be controlled properly. While there are many rocks, some of the energy from the explosive branches will be lost into the cracks and the blasting process will be difficult to control. The factors that affect "Rock Blast Ability" include faults, rock types, coating fields, and strike-dip rock formations.
C. Blasting Mechanism
The concept used is the concept of solving and mechanical reactions in homogeneous rocks. The mechanical properties in homogeneous rocks will differ from rocks that have heterogeneous defects as found in blasting work. The process of breaking rocks resulting from blasting is divided into three processes: Dynamic loading, Quasi-static loading, and release of loading.
- The process of solving level I ( Dynamic Loading) ~ Pad when explosives explode, high pressure destroys rocks in the area around the explosive hole. Shockwaves that cause explosive holes to creep at speeds of 9000 - 17000 ft/s will result in tangential voltage, resulting in a creeping damage from the plumbing area. The first crushing of the spread occurs within 1 - 2 ms. at this stage there is a destruction of rocks around the firing hole and the energy of the explosion is passed in all directions.
- Quasi-static loading ~ The pressure associated with the shock wave that left the hole in the solving process is positive. When reaching the free field will be reflected, the pressure will drop quickly, then turn negative and a tensile wave arises. This tensile wave creeps back into the rocks. Therefore, the rocks are less resistant to pull than pressure, so there will be primary damage caused by the tensile voltage of the reflected waves. when the tension is strong enough, it will cause slambing or spalling in the free field. in the process of solving level I and II, the function of the shock wave is to prepare the rocks with a number of small relics...... Theoretically the shockwave energy amounts to between 5 - 15% of the total energy of explosives. So the shockwave provides basic readiness for the final level solving process. At this stage the blasting energy that moves until the free field destroys the rocks on the wall of the level.
- Phase III breakdown process (release of loading) ~ Under the influence of very high pressure from blasting gases then the primary radial break (level II) will be widened rapidly by the combination of the effect of tensile voltage caused by radial compression and division (pneumetic wedging). If the rock mass in front of the explosive hole fails to maintain its position moving forward then the high pressure voltage in the rock will be released. The effect of detaching rocks is to cause a high tensile voltage in the rock mass that will continue the breakdown of the results that have occurred in the level II breakdown process. The resulting fragmentation in level II solving causes weak areas to initiate major fragmentation reactions in the blasting process. In this last stage the energy reflected by the free field in the previous stage will destroy the rocks more perfectly.
Figure 1. The process of breaking rocks due to blasting
D. Rock Fragmentation
Fragmentation is a general term to indicate the size of each chunk of blasting. The size of the fragement depends on the next process. For a specific purpose a large rock fragmentation size of 9boulder) is required, for example arranged as a roadside barrier of mines. But most want a small fragmentation size because handling the next activity will be easier. The largest fragmentation size is usually limited by the dimensions of the 9 excavator/shovel digging tool bowl) which will load it into the truck dump.
Some general provisions on the relationship of fragmentation with explosive holes:
- The size of a large explosive hole will result in chunks of fragmentation, therefore it should be reduced by using more powerful explosives.
- Please note that adding explosives will result in a distant throw.
- In rocks with high crack intensity and small amounts of explosives combined with short space distances will result in small fragmentation.
E. The Effect of Explosions on Rocks
The effect of the explosion caused the onset of: the area of destruction, the area of cracks, the vibration of the ground (ground vibration), and the blast water.
- Crushed zone ~ is located around the plumbing hole, where solid rocks will turn into fine grains in the form of powder. this is due to the high temperature and pressure of the blast reaction gases as well as the high pressure of detonation. The size of this area depends on the type of explosives and materials to be detonated.
- Fracture zone ~ occurs if the voltage caused by the explosion is greater than the acceptable voltage of the rock. the cracks that form are first caused by detonation pressure which is then magnified by the blasting pressure. the size of this area is affected by the type of rocks and explosives. For sedimentary rocks the size of crack areas can reach 40 times the diameter of a crack hole.
- Ground vibration ~ occurs in elastic zone area. In this area the voltage received by the rock is smaller than the strength of the rock causing a change in shape and volume. According to the elastic properties of the rock, the shape and volume will return to their original state after no voltage has worked. Voltage patches in the elastic area will cause elastic waves also known as seismic waves.
- Air Blast ~ is a pressure wave that is predicted in the atmosphere at the speed of sound. There are 2 kinds of water blast : ~ Audible sound
~ Which cannot be heard ( subaudible sound)
audible air blast has a frequency below 29 Hz.
F. Factors That Affect Rock Fracmentation
1. Karekteristic rocks, in the form of:
- Strength (strenght), It is the strength of the rock to withstand the load or force that works on the rock without any damage to the rocks. These styles are drag styles and press styles.
- Violence, is a prisoner of a fine surface field against abrasion. Hardness is used to measure the technical properties of rock materials and can also be used to state how much voltage it takes to cause damage to rocks.
- Density (Density), rocks that have a high density means having tight and dense granules so as to allow the spread of energy in rocks faster and easier. The tightest rocks have smaller energy loss and tend to disintegrate better.
- Velocity, can be interpreted as the time it takes to press energy to the free field and then back again.
- Elasticity, The elasticity properties of rocks can be expressed in the elasticity modulus, which is the coma factor between the normal voltage and the relativ voltage. Modulus elasticity is highly depends on its mineral composition, porosity, type of displacement and load applied.
- Plasticity, is the behavior of rocks that causes fixed deformation after the voltage is restored to its original state, where the rock has not been destroyed.
2. Geological Structure
Geological structure of rocks can affect the kelurusan of the plumbing and the speed of drilling. Meanwhile, the process of blasting geological structures can weaken shock waves and release and create a balance in the distribution of explosive stuffing.
3. Influence of Groundwater
Groundwater conditions can also affect the outcome of blasting. the use of groundwater can lead to cooling reactions and the soluble of explosive elements by water.
ANFO (Ammonium Nitrate-Fuel Oil) explosives have a poor level of resistance to water, so if the ANFO used is contaminated by water it will affect the fragmentation of the blasting rocks and can even cause explosive failure.
4. Drilling Geometry
Drilling geometry and drilling patterns are designed in an integrated way in the blasting design. Drilling geometry: Drill hole diameter, Burden, spacing, drill hole depth and slope.
Drilling geometry also includes drilling direction. drilling direction there are two namely: upright drilling direction and tilt drilling direction.
The shot is made upright, so at the level receives a large press wave, resulting in a toe on the level floor, this is because the press wave will be partially reflected on the free field and some will be passed on to the bottom pad of the level floor. And the energy in this blasting is also not enough to give the urge to remove the rocks from the parent rock.
While in the use of oblique firing holes will form a wider free field, so it will facilitate the process of breaking rocks because the pressure waves reflected larger and the press waves passed on the level floor will be smaller. The slope of the firing hole actually depends on the location of the blast in the field.
 |
| Figure 2. Drilling Direction |
5. Drilling Pattern
The success of one of them lies in the availability of sufficient free fields. Drilling pattern is a pattern in drilling activities by obtaining firing pits systematically. Drilling patterns that can be applied to open mines there are usually three kinds of drilling patterns, namely:
- Square pattern ~ This drilling pattern is where the distance between the burden and the space is the same length that forms the square.
- Rectangular pattern ~ where the size of the spacing in a row is greater than the burden distance that forms the rectangular pattern. to get good fragmentation, this pattern is not precise because the area that is not affected by blasting is quite large.
Figure 3. Square pattern drilling pattern and rectangular pattern - The staggered pattern ~ in this drilling of the firing hole is made like Zi-zag so that a triangular pattern is formed. Where the distance of a large spacing is equal to or greater than the burden distance. In this pattern the area that is not affected by blasting is quite small compared to other patterns. However, in the application in the field this pattern is quite difficult to perform further drilling and arrangement. But to improve the fragmentation of blasting rocks, this pattern is more suitable for use. In order to obtain fragmentation of good blasting results, drilling patterns must also be observed. Because it is seen in the image 4 areas are not exposed to detonation smaller than the parallel drilling pattern. Where the area is not exposed to blasting energy, the rock will be large or can be said to fragment the result of large blasting (boulder).
 |
| Figure 4. Advantages of intersing hose drilling patterns |
G. Blasting
blasts on mining companies are carried out to dispose of rocks from the main rocks. And it is carried out to support the excavation operations carried out by excavators, because the purpose of the blast itself is to create fragmentation so that it can produce fragmentation on the rocks, which can facilitate in the process of excavating the rocks.
1. The geometry of blasting, is a very decisive result of blasting in terms of the resulting fragmentation, expected fragmentation as well as in terms of the level that is
formed. In blasting activities that include blasting geometry are: burden, space, stemming, subdrilling, explosive hole depth, fill column length, explosive hole diameter and level height.
blasts on mining companies are carried out to dispose of rocks from the main rocks. And it is carried out to support the excavation operations carried out by excavators, because the purpose of the blast itself is to create fragmentation so that it can produce fragmentation on the rocks, which can facilitate in the process of excavating the rocks.
1. The geometry of blasting, is a very decisive result of blasting in terms of the resulting fragmentation, expected fragmentation as well as in terms of the level that is
formed. In blasting activities that include blasting geometry are: burden, space, stemming, subdrilling, explosive hole depth, fill column length, explosive hole diameter and level height.
 |
| Figure 5. Blasting Geometry |
- Burden (B) ~ Is a perpendicular distance between the firing holes against the closest free field. Burden is the most important dimension in blasting activities, as it is used to determine the geometry of other blasting. A good burden distance is the distance that allows maximum energy to move from the fill column to the free field and is reflected back with enough force to surpass the strong pull of the rock so that there will be destruction. If the blasting is carried out the application of a burden distance that is too small it will result in the energy of the explosion easily moving towards the free field can cause the flying rock to occur. While the distance burden is too large will result in energy not strong enough to reach the free field so that the rupture of rocks will form chunks or boulders
- Spacing (S) ~ Is the distance between firing holes in a row and measured parallel to the patio wall (level). In estimating the length of the space, what needs to be considered is whether there is an interaction between adjacent charges. If each drill hole is blown individually with a long enough time interval and to allow each drill hole to explode perfectly, there will be no interaction, resulting in a complex effect.
- Stemming (T) ~ or collar is a column to place the cover material in the firing hole located above the fill column. Stemming is used to determine the stress balance in order to break the rocks so that they can explode simultaneously. Stemming is also useful for locking out gases arising from blasting results so that they can dissify rocks with maximum energy. There are 2 things related to stemming, among others:
- Stemming Length Size, Generally the same as burden when blasting is carried out on compact rocks, to get maximum blasting results as expected. If the blasting process uses a stemming length that is too short then the resulting blast energy tends to reach the free field faster, resulting in fly rock and energy that suppresses the rock is not maximal. Short stemming will also result in poor fragmentation of rocks (and vice versa).
- The size of the stemming material, this strongly affects the blasting result, when the stemming material consists of fine grains from the drilling (cutting), lacks the friction force against the firing hole so that high pressure air will easily push the stemming material. so that the energy is supposed to destroy the rocks, much is lost through the stemming cavity. To prevent it many use coarse and hard grainy materials.
Figure 6. Stemming
- Subdrilling (J) ~ Is an addition of depth to the explosive hole with the aim that the rocks can explode full face as expected and the rocks that are uncovered are only limited to the floor level only. Subdrilling that is too short can result in the onsanion (toe) so it can complicate the next activity process.
- The depth of the explosive hole (H) ~ is the depth of the hole to be blasted which is the summation between the height of the level and the subdrilling. the depth of the explosive hole made should not be smaller than the burden. This aims to avoid everbreak and (flyrock) into the explosive hole usually determined based on the desired production capacity.
Figure 7. Explosive hole depth
- Trace height (L) ~ Specifically the maximum level height is determined by the drill hole equipment and loading tools available. The height of the level is taken based on the depth of the firing hole and subdrilling. If the height of the level exceeds the depth of the firing hole, then often the formation of a toe at the bottom of the level. This is due to the explosive's explosive energy not being able to reach the bottom of the level.
- The length of the Stuffing Column (PC) ~ is the length of the firing hole column to be filled with explosives. The length of this column is the depth of the firing hole minus the stemming used. The more explosives used in the blasting process it will require a long enough fill column length so it will also affect the size of the length stemming.
Figure 8. Fill Column Length (PC)
2. Blasting pattern, In general the blasting pattern shows the blasting sequence means there is a pause in the blast time between the explosive holes called delay time. Here are the advantages gained by applying snooze time on the blasting system among others:
- Reduce vibration
- Reduce Over break and fly rock
- Reduces concussion due to water blast and noise
- Can direct the throw of rock fragmentation.
- Can improve the size of rock fragmentation resulting from blasting
- Box cut, is a blasting pattern that collapses forward and forms a box.
- Corner cut, is a pattern of blasting that the direction of the rock collapses into one corner of the free field.
- V cut,is a pattern of blasting that the direction of the rock collapses forward and forms the letter V
H. Classification of Explosives Explosives
in the mining industry is generally made of a mixture of chemicals, so it is called chemical explosives.
The definition of an explosive is a single compound chemical or a mixture in the form of solid, liquid, gas or mixture which when given heat action, impact, friction or initial explosion will react very quickly and hot (exothermal) resulting in a partial or entirely high-pressure gas and very hot temperature.
Blasting will provide different results than expected as it depends on external conditions when the work is carried out that affects the quality of the explosive-forming chemicals that cause combustion, followed by deflagration and last detonation.
The process of decomposition of explosives can be described as follows:
- Combustion ~ is a chemical reaction that is hot on the surface of a burning object and maintained the continuity of the combustion process by the heat generated from the reaction itself and its products in the form of gases. Combustion reactions require oxygen elements both in the wild and from the molecular bonds of materials or burning materials.
- Deflagration ~ is a combustion reaction at very high speed and produces pressurized gases whose pressure increases (expansion) during the combustion process, causing an explosion. As a result of this pressure, there is an effect of removal that is comparable to the combustion process that occurs.
- Explosion ~ is a rapid instantaneous expansion of the gas into larger volumes accompanied by loud noises and damaging mechanical effects. From that definition it is implied that an explosion does not involve a chemical reaction, but its appearance is caused by the transfer of energy to mass movement which gives rise to a damaging mechanical effect accompanied by heat and loud sounds.
- Detonation ~ is a chemical-physical process with a very high reaction speed that produces very large gases and temperatures and builds a very large expansion of force as well. The reaction speed spreads heat pressure throughout the blasting zone in the form of shock compression wave and this process takes place continuously to free up energy so that it ends and gives a shattering effect. Explosives are classified based on their energy sources into mechanical, chemical, and nuclear explosives. The type of explosive is broadly classified into 3 groups (JJ Manon 1978) :
- Mechanical explosives
- Chemical explosives : ~ High explosive : primary explosive and secondary explosive
- nuclear explosives
I. The physical nature of explosives The
physical properties of explosives are a real appearance of the nature of explosives when dealing with changes in the surrounding environmental conditions. This is what must be observed and known signs by a plumber to identify an explosive that is damaged, damaged but still usable, and not damaged. The physical properties of explosives to be aware of are:
- Density ~ in general is a number that states a comparison of weight per volume.
- Sensitivity ~ is a trait that indicates the ease or vulnerability of an explosive to be initiated (detonated) due to an outside thrust in theform of impact, show wave, heat (flame), or friction.
- Water resistance ~ is a measure of an explosive's ability to fight the surrounding water without losing sensitivity. if an explosive dissolves in water in a short period of time means that the explosive has poor water resistance, otherwise if it is not soluble in water is called well (exellent): examples of explosives that have poor water resistance are emulsions, watergels, slurries.
- Chemical stability ~ is the ability not to change chemically and maintain sensitivity while in storage in the warehouse under certain conditions. Factors that accelerate chemical instability include heat, cold, humidity, raw material quality, contamination, packing and explosive warehouse facilities.
- Characteristics of gas (fumes characteristic) ~ Detonation of explosives will produce fume, i.e. toxic blasting gas, if the processof mixing an imperfect explosive concoction that causes excess or lack of oxygen during the process of chemical decomposition of explosives takes place. Fume-classified blasting gases include nitrogen monoxide (NO), Nitrogen Oxide (NO2), and carbon monoxide (CO). It is expected that the detonation of a commercial explosive does not produce toxic gases, but in fact in the field it is difficult to avoid due to several factors including:
- Mixing explosive concoctions that include oxide elements and fuel are not balanced, so as not to achieve zero oxygen balance.
- Inappropriate primary location
- Less closed due to less dense and strong stemming installation
- The water in the explosive hole
- Delay time system is not precise lying in the possibility of a reaction between explosives and rocks
A. Explosive Filling
- Powder Factor (PF) ~ is a number to state the amount of material blasted or dismantled by a number of explosives that can be expressed in kg/ton. PF is usually determined by the company because it is the result of some previous research and also because of various considerations.
- The length of the fill column (PC) ~ is the depth of the explosive hole minus the stemming. PC = H-T description : PC = Field length (m), H = Hole depth (m), T = Stemming(m).
- ANFO Explosives ~ in the use of ANFO in accordance with the provisions of zero oxygen balance then the comparison used is 94.5 % Ammonium Nitrate (AN) and 5.5 % Fuel Oil (FO).
- Loading Density ~ is the amount of explosives for each column length of the explosive hole stated in kg/m.
B. Calculation of Blasting Volume
of Blasting Geometry In open-pit mines or Quarys, which generally apply blasting or bench blasting, the volume of rocks to be blasted depends on the burden, space, height, and number of holes.
Blasting volume need = B
x S x H Total blasting volume
= (B x S x H) x Number of holes Fill column length = Handak weight required
of Blasting Geometry In open-pit mines or Quarys, which generally apply blasting or bench blasting, the volume of rocks to be blasted depends on the burden, space, height, and number of holes.
Blasting volume need = B
x S x H Total blasting volume
= (B x S x H) x Number of holes Fill column length = Handak weight required
Loading density
D. Data Processing and Data Processing
1. The
data obtained in the blasting area are: drilling pattern, drilling direction and specification data from the drill tool, e.g. Furukawa brand with a drill bit diameter of 5.5 inch and the length of the drill rod 6 meters.
2. Data Processing
a. Blasting Geometry ~ at one month the blasting geometry is
1. The
data obtained in the blasting area are: drilling pattern, drilling direction and specification data from the drill tool, e.g. Furukawa brand with a drill bit diameter of 5.5 inch and the length of the drill rod 6 meters.
2. Data Processing
a. Blasting Geometry ~ at one month the blasting geometry is
b. Blasting Volume
V =
B x S x H = 4.5 x 5.5 x
5
= 123.75 m3 (BCM) While on the daily calculation there are 62 holes,
then: Blasting volume = rock volume x number
of holes V = (B x S x H) x 62
V = 123.75 x
62 V = 7672.5 m3 (BCM)
E.g. workmanship in February and there are 28 days, then:
= daily blasting volume x 28
= 7,672.5 m3 x 28
= 214,830 m3
c. PC Column Length = H - T description
:
PC =
Field length H =
Depth of explosive hole T = Stemming
T (stemming) used in company X is 2 m (company provision)
so,
PC = H - T
= 5m -2m
= 3m
d.
The use of Explosives Loading Density constitutes the amount of explosives for each column length of the plumbing :
ANFO fill weight
for each hole
E = de x Pc = 12.13
kg/m
x 3m =
36.39 kg f. ANFO needs for
each hole The use of explosive ammonium nitrate (AN) material for each hole can be described using
a formula, namely:
WEIGHT AN = Total weight of explosives per hole x 95.5
100
= 36.39 x
95.5 100 = 37.75 kg Fuel Oil (FO) needs for each hole can also be described using formula, Namely: Number
of AN usage for the number of explosive holes per day
= Number of explosives needing to bebang x number of explosive holes
= 34.75 kg x 62
= 2154.5 kg AN Number
of FO uses for the number of explosive holes per day
= Number of FO needbang x number of explosive holes
= 2.50 liters x 62
= 155 liters FO
3. Troubleshooting
Based on actual data in the field using a burden of 4.5m, a space of 5.5m and a depth of 5 explosive holes we get a voleme of 123.75 m3.
Thus, from 300,000 BCM blasting planing per month, we can calculate : actual data = production target blasting jml explosive hole x 214,830 m3 (BCM) 300,000 BCM = 62 x 214,830 m3 x = 300,000 x 62 214,830 m3 x = 18,600,000 x = 18,600.000 214,830 x = 86.5 holes Total ANFO needs after the increase in the number of explosive holes per day is: Ammonium Nitrate (AN) = number of needs AN perlubang x number of holes AN = 34.75 kg x 86 AN = 2988 kg/day Fuel Oil (FO) = number of FO x number of FO holes = 2.50 liters x 86 FO = 215 liters/day.
V =
B x S x H = 4.5 x 5.5 x
5
= 123.75 m3 (BCM) While on the daily calculation there are 62 holes,
then: Blasting volume = rock volume x number
of holes V = (B x S x H) x 62
V = 123.75 x
62 V = 7672.5 m3 (BCM)
E.g. workmanship in February and there are 28 days, then:
= daily blasting volume x 28
= 7,672.5 m3 x 28
= 214,830 m3
c. PC Column Length = H - T description
:
PC =
Field length H =
Depth of explosive hole T = Stemming
T (stemming) used in company X is 2 m (company provision)
so,
PC = H - T
= 5m -2m
= 3m
d.
The use of Explosives Loading Density constitutes the amount of explosives for each column length of the plumbing :
ANFO fill weight
for each hole
E = de x Pc = 12.13
kg/m
x 3m =
36.39 kg f. ANFO needs for
each hole The use of explosive ammonium nitrate (AN) material for each hole can be described using
a formula, namely:
WEIGHT AN = Total weight of explosives per hole x 95.5
100
= 36.39 x
95.5 100 = 37.75 kg Fuel Oil (FO) needs for each hole can also be described using formula, Namely: Number
of AN usage for the number of explosive holes per day
= Number of explosives needing to bebang x number of explosive holes
= 34.75 kg x 62
= 2154.5 kg AN Number
of FO uses for the number of explosive holes per day
= Number of FO needbang x number of explosive holes
= 2.50 liters x 62
= 155 liters FO
3. Troubleshooting
Based on actual data in the field using a burden of 4.5m, a space of 5.5m and a depth of 5 explosive holes we get a voleme of 123.75 m3.
Thus, from 300,000 BCM blasting planing per month, we can calculate : actual data = production target blasting jml explosive hole x 214,830 m3 (BCM) 300,000 BCM = 62 x 214,830 m3 x = 300,000 x 62 214,830 m3 x = 18,600,000 x = 18,600.000 214,830 x = 86.5 holes Total ANFO needs after the increase in the number of explosive holes per day is: Ammonium Nitrate (AN) = number of needs AN perlubang x number of holes AN = 34.75 kg x 86 AN = 2988 kg/day Fuel Oil (FO) = number of FO x number of FO holes = 2.50 liters x 86 FO = 215 liters/day.
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