Geometry Of The Drilling Include :
- Diameter Hole Shot
Diameter of the bullet holes that are too small causing the resulting energy factor will be reduced so as not big enough to unload rocks will explode, if the diameter of the hole is too large, then shoot a hole shot is not enough to produce good fragmentation, especially on the rocks there is lots of stocky with distances at high densities. A small diameter bullet holes also provide fault or destruction of the better on the roof ladder. this corresponds to stemming, where a large fire pit then the length of stemming aka also greater due to avoid vibration and fly rock, whereas if you use a small bullet hole then the length of stemming can be reduced.
- Shot Hole Depth
shot hole depth is usually adjusted with a high level is applied. and to get a flat level floor then shot hole depth should be greater than the higher levels, in which excess than the depth of drilling is called a sub.
- Direction Of Drilling
drilling direction that we know there are two, namely the direction of drilling vertical and oblique direction of drilling. alignment direction of the drill holes on the ladder should be level to ensure uniformity of burden who want to get a space in geometry and blasting. bullet holes made upright, then at the floor level will receive a large wave hit, causing a bulge in the floor level, this is because the waves will be reflected in the press and some areas are free and some will be forwarded on the bottom floor level. where as in the use of oblique shot hole will form a wider field-free, that will facilitate the outbreak of the rock press and the reflected waves are larger and the transmitted wave on the floor press a smaller level.
- Drilling Pattern
In the open pit drilling blasting is usually done on a bench or a ladder. Drilling carried out to prepare the explosive hole with good quality in the right position so that blasting can be run efficiently on the yield and the consumption of explosives
There are three drilling patterns that exist in the open pit, namely:
- Drilling pattern rectangle (Square Pattern) is a pattern of drilling holes with the placement of fire between the rows next to each line parallel to and form a rectangle. Drilling a rectangular pattern in which long term burden with as large a space is not called a square rectangular pattern.
- Drilling pattern of alternating (Staggered) is the placement of drilling hole pattern explosive on successive lines are not parallel to each other, and for drilling pattern of alternating long burden which is not equal to the length of a space called the staggered rectangular pattern
- Rectangular pattern, ie in a single line spacing greater than the burden
Drilling in open pit generally use three types of drill tools, namely:
1. Top hammer drilling
* Hydraulic self = contained drill
* Pneumatic drill with water portable compressor
2. Down the hole drilling
* Pneumatic operated with a portable water carrier compressor
* Hydraulic operated self contained carrier
3. Rotary drilling
* Rotary crushing
* Rotary cutting
The factors that affect the speed and penetration of the drilling are:
a. Borehole geometry
b. Geological circumstances, namely the existence of faults, fractures
c. Structure and texture of the rock to be drilled
d. Employment conditions and driveway
e. Fragmentation and production of the required and specified
f. The cost of drilling
g. Rules must be obeyed
a. Borehole geometry
b. Geological circumstances, namely the existence of faults, fractures
c. Structure and texture of the rock to be drilled
d. Employment conditions and driveway
e. Fragmentation and production of the required and specified
f. The cost of drilling
g. Rules must be obeyed
Direction of drilling on the ladder or the bench there are two oblique drill holes and drill holes straight. By drilling up at the top level of fragmentation is less good and on the ground floor of explosive power can not be fully distributed (greater energy loss). But with oblique drill hole, which is usually with a slope of 3: 1 can avoid the problems mentioned above
Oblique drill hole has several advantages compared with the upright drill holes, among others:
* Levels (bench) formed more stable
* Reducing the risk of bumps and back break
* The results of the stack (muck pile shape) better
* Levels (bench) formed more stable
* Reducing the risk of bumps and back break
* The results of the stack (muck pile shape) better
Some difficulties in the manufacture of drill holes sloping, among others:
* It is difficult to drill accurately, especially when drilling holes in explosive
* To perform drilling needed slanted scrutiny addition drill hole straightness is an important factor
* It is difficult to drill accurately, especially when drilling holes in explosive
* To perform drilling needed slanted scrutiny addition drill hole straightness is an important factor
If the direction is not straight drilling will affect the cost of drilling and blasting are likely to be enlarged. Besides, it would result in the distance spacing and burden of the design changes that have been established because often coincide which will lead to changes in both distances. Factors that could cause the drilling direction is not straight, among other geological structures and explosive hole depth does not match the size of the diameter of bits used.
In drilling underground openings generally there is only one area of freedom, namely labor leaders or face. For that, need to be made an additional field called the cut-free.
Generally there are four types of cut are:
Generally there are four types of cut are:
- Center cut is also called pyramid or diamond cut
- Wedge cut or V-cut, angled cut or a cut wedge-shaped
- Drag cut or fan patterns
- Burn cut is also called cylinder cut
1. DRAG CUT
Drag cut or fan patterns, wedge-shaped like the difference lies in the wedge position is not in the middle of the openings, but lies on the floor or wall openings. How to make the drill holes are made oblique manner to form a cavity in the floor or the wall. This method is effective in layered rocks and not hard and also acts as a controlled blasting. Hole "Cut" made an angle to the plane in the plane perpendicular to bedding, so it would be revealed by field rock bedding. Type "Cut" as is suitable for small tunnel (width from 1.5 to 2 m) where great progress is not too important.
2. FAN CUT
This pattern is suitable for use in layered rock structures and are rarely used. In type "Fan Cut" made an angled shot holes and are on flat areas. After cutting detonated the rock that is between two lines of holes "Cut" will be uncovered. Furthermore, the holes 'easer' and 'Trimmer' will enlarge the openings 'cut' to the geometric shapes on the tunnel.
This pattern is suitable for use in layered rock structures and are rarely used. In type "Fan Cut" made an angled shot holes and are on flat areas. After cutting detonated the rock that is between two lines of holes "Cut" will be uncovered. Furthermore, the holes 'easer' and 'Trimmer' will enlarge the openings 'cut' to the geometric shapes on the tunnel.
3. V - CUT
. Wedge cut or V-cut, angled cut or a cut wedge-shaped, each pair of four or six holes with the same diameter were drilled towards one point, but the drill hole between parallel pairs, thus forming a wedge. This is more convenient than pyramid-cut but less effective for hard rock. V-cut is often used in blasting the tunnel. Shoot holes in this pattern are arranged so that each of the two holes form a 'V'. A 'Cut' can consist of two or three pairs of 'V', respectively in the horizontal position. Hole - a hole shot on the 'Cut' is usually made form a 600 angle to the surface of the tunnel. Thus, the length of the progress depends on the width of the tunnel, because the length of the drill rod is limited to the width. One or two bullet holes shorter (burster) may be made in the middle of 'Cut' to improve the results of fragmentation.
. Wedge cut or V-cut, angled cut or a cut wedge-shaped, each pair of four or six holes with the same diameter were drilled towards one point, but the drill hole between parallel pairs, thus forming a wedge. This is more convenient than pyramid-cut but less effective for hard rock. V-cut is often used in blasting the tunnel. Shoot holes in this pattern are arranged so that each of the two holes form a 'V'. A 'Cut' can consist of two or three pairs of 'V', respectively in the horizontal position. Hole - a hole shot on the 'Cut' is usually made form a 600 angle to the surface of the tunnel. Thus, the length of the progress depends on the width of the tunnel, because the length of the drill rod is limited to the width. One or two bullet holes shorter (burster) may be made in the middle of 'Cut' to improve the results of fragmentation.
4. PYRAMID CUT
Pyramid Cut is also called Center cut or diamond cut, consists of 4 pieces of shot holes with the same diameter and converge at a point of the drill hole in the middle of the tunnel to form a pyramid. For hard rock, the number of holes 'Cut' can be added into 6 pieces.
Pyramid Cut is also called Center cut or diamond cut, consists of 4 pieces of shot holes with the same diameter and converge at a point of the drill hole in the middle of the tunnel to form a pyramid. For hard rock, the number of holes 'Cut' can be added into 6 pieces.
5. BURN CUT
Burn the cut is also called cylinder cut, the pattern is perfect for hard rock such as sandstone (sandstone) or igneous rock and is not suitable for a layered structure. In contrast to the pattern - the pattern of 'Cut' before, where the hole 'Cut' makes an angle to each other and perpendicular to the surface of the tunnel. In the Cut Burn patterns, there are some that do not cut holes in filled with explosives that serves as a free field to cut the holes are filled. Empty hole can be made more than one size larger than the hole cut are filled.
Burn the cut is also called cylinder cut, the pattern is perfect for hard rock such as sandstone (sandstone) or igneous rock and is not suitable for a layered structure. In contrast to the pattern - the pattern of 'Cut' before, where the hole 'Cut' makes an angle to each other and perpendicular to the surface of the tunnel. In the Cut Burn patterns, there are some that do not cut holes in filled with explosives that serves as a free field to cut the holes are filled. Empty hole can be made more than one size larger than the hole cut are filled.
6. LARGE HOLE CUT
This method is similar to the Burn Cut, consisting of one or more large-diameter holes are empty, surrounded by a hole-small-diameter drill hole containing explosives. Burden of holes - holes that are filled with empty holes are relatively small. The next hole - a hole explosive arranged in a rectangle surrounding the openings. The number of rectangles in the 'Cut' is limited by the provisions of rock 'Burden' in the last four terms do not exceed the 'Burden' of Stoping hole.
This method is similar to the Burn Cut, consisting of one or more large-diameter holes are empty, surrounded by a hole-small-diameter drill hole containing explosives. Burden of holes - holes that are filled with empty holes are relatively small. The next hole - a hole explosive arranged in a rectangle surrounding the openings. The number of rectangles in the 'Cut' is limited by the provisions of rock 'Burden' in the last four terms do not exceed the 'Burden' of Stoping hole.
Method Of Calculation
To facilitate the calculation of the pattern of drilling and Cross Section of the tunnel, it's easier that is, the calculation of 'Cut' and the other part (easer and Trimmer). The calculation should use standard explosives to be used for example to use the dynamite with Weight Strength = S = 1.0 or 78% of Blasting Gelatine.
Calculation of Cut
For parallel hole hole near Burster (based on bustafsor 1973, as guidelines for the use in the field)
V = 0.7 d
Description:
- Using an empty hole
- D = diameter of the hole is empty
- Using an empty hole
- D = diameter of the hole is empty
If using two holes, then:
V = 0.7 x 2 d
Filling the holes need to choose a balanced Concertration Charge, I remember the rectangular hole adjacent to large, empty, to avoid Plastic deformation or breakage.
The following table can be used as a benchmark filling holes in the "Parallel Hole Cut"
V = 0.7 x 2 d
Filling the holes need to choose a balanced Concertration Charge, I remember the rectangular hole adjacent to large, empty, to avoid Plastic deformation or breakage.
The following table can be used as a benchmark filling holes in the "Parallel Hole Cut"
| NUMBER RECTANGULAR | hb (x H) | Lp (x Lb | ho (x v) |
| 1 |
0,05
| 0,05 | 0,05 |
| 2 | 0,05 |
0,05
| 0,05 |
| 3 |
0,20
|
0,05
| 0,05 |
| 4 | 0,33 | 0,05 | 0,05 |
Description:
hb = Height Bottom Charge
H = Depth of Hole
Lp = Concentration of the charge column
V = Burden
ho = Stemming
For angled holes
High Cut and Burden V1 and V2 are calculated with the diagram
- For all the holes, the height of the bottom charge equal to:
hb.1 / 3 H
H = depth of hole - The concentration of the charge column: 1
Lp = 40-50% of the Lb - empty hole
Ho = 0.3 V1
CAUSES OF THE DISTINGUISHING PATTERNS DRILLING IN OPEN AND MINE UNDERGROUND MINING
| FACTOR | UNDERGROUND MINING | OPEN MINING |
| The area | Limited, according to the dimensions of openings extent influenced by the stability of these openings | More extensive because there are in the earth's surface and can select a suitable area |
| The volume of the detonation | Limited due to limited surface area of the aperture, the diameter of the drill bit and drilling depth | Bigger could reach hundreds of thousands of cubic meters per detonation, so it can target a large planned |
| Fresh air supply | Depending on the system is well ventilated | Not problematic because it is done in open air |
| Safety | Critical, due to limited space, rock avalanches from the roof, where survival is limited | Relatively more secure because all work is done in an open area |
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