AU2016203001B2

AU2016203001B2 - Method for drilling and dismantling

Info

Publication number: AU2016203001B2
Application number: AU2016203001A
Authority: AU
Inventors: José Raimundo Lopes; Galdino Ananias de Santana Neto
Original assignee: Vale SA
Current assignee: Vale SA
Priority date: 2015-05-11
Filing date: 2016-05-10
Publication date: 2021-01-28
Anticipated expiration: 2036-05-10
Also published as: AU2016203001A1; BR102015010654B1; BR102015010654A2

Abstract

METHOD FOR DRILLING AND DISMANTLING Abstract A Method for the Drilling and Dismantling of Rock Banks (1) in open pit iron ore mines is described. The method of the invention is designed to adapt the existing drilling and dismantling methodologies of the state of the art to the modem iron ore mining systems that employ conveyor belts (2) instead of off-road trucks. Among the characteristics of this new method are: the drilling of holes (5) to a depth of approximately 30 meters and a blast pattern designed to avoid the launching of material in the direction of the conveyor belts (2) during the detonation of the rock (1); amongst other additional characteristics. 4/5 Fig. 6 3I (Invention) Fig. 7 4 d' d 2 (Invention)

Description

4/5 Fig. 6 3I

(Invention)

Fig. 7

4 d' d

2 (Invention)

METHOD FOR DRILLING AND DISMANTLING

Field of the Invention

[0001] A new method for drilling and dismantling of rock benches in open pit iron ore mines is described.

Background of the Invention

[0002] The method traditionally used to exploit the ore in open pit iron ore mines is as follows: initially, planning of the mining program is performed, during which the areas to be explored and the best configuration of excavation are defined according to the topography of the area to be explored. During this step the locations where the ramps, roads and accesses are to be built are also defined. These ramps, roads and accesses, in the future, will enable the access of the equipment to the interior of the mine.

[0003] After planning of the mining program, the blasting plan is defined. This consists in planning the dismantling of the benches. The blasting plan establishes where to drill, how much and which type of explosive should be used, seeking to adapt the granulometry of the ore to the subsequent stages.

[0004] After dismantling of the massif, the dismantled ore is carried by the bulldozers onto large sized dump trucks. This ore is then transported by these trucks to the ore processing plant.

[0005] Each one of these trucks is capable of transporting a limited amount of material (according to its own capacity). Furthermore, the environmental impact caused by these trucks, resulting from the high consumption of diesel and tires, also constitutes a big problem of the state of the art.

[0006] To eliminate the use of trucks in open pit iron ore mines, certain pioneer techniques were implemented, consisting in the substitution of these trucks for mobile crushing systems, using relocatable and other peripheral equipment.

[0007] One of the referred techniques is revealed in document US20110175429, which presents a method for the exploration of open pit mines, which includes the following sequential exploration stages: Stage 1 - blasting of a rock bank; Stage 2 - collection of the dismantled material; Stage 3 - transportation of the collected material to a rock crusher; Stage 4 - transportation of the crushed material out of the mine by means of a conveyor belt.

[0008] Despite innovating in the techniques used up to now to transport iron ore, the previous technique revealed in US20110175429 is incomplete and incipient since, when we substitute the machinery currently used in iron ore mines for mobile conveyor belts and rock crushers as established in the document US20110175429, we continue to face a series of bottlenecks in the "production line" that impair the processing of large volumes of iron ore, resulting in production interruptions.

[0009] The method for dismantling revealed in US20110175429 uses, preferentially, benches measuring 40 meters in width, 20 meters in depth in the horizontal plane and 10 meters in height in the vertical plane. The blasting of a bench of this size is capable of producing close to 8.000 m3 of ore, that are equivalent to 21 thousand tons of ore per detonation

[0010] However, each conveyor belt used in US20110175429 is capable of transporting 8.5 mil tons of iron ore per hour. Thus, by using two or more conveyor belts it is possible to transport 16, 24, 32 thousand tons per hour. For this reason, the largest bottleneck of the technique described in US20110175429 is the dismantling operation. It should be observed that, for a mine equipped with three conveyor belts in operation, it would be necessary to conduct one detonation every hour in order for the conveyor belts to operate at their nominal capacity.

[0011] It is operationally impossible to conduct one detonation every hour in an open pit mine since each dismantling operation requires a planning stage, drilling of holes, insertion of explosives in the holes and subsequent detonation. It should be observed that these stages are necessarily in sequential order, i.e. they cannot occur simultaneously, and each can take more than one Day to be concluded. Furthermore, for the detonation stage to occur, the entire area around the bench to be detonated must be evacuated, displacing the equipment to a minimum radius of 300 m and personnel to a minimum radius of 700 m beyond the limits of the bench.

[0012] Therefore, it is necessary to dismantle a large volume of rocks at each detonation, a volume much larger than that traditionally detonate, to ensure the operational continuity of a process that employs conveyor belts.

[0013] Also, it is fundamental that the dismantling operation be directed so that the conveyor belts are not hit by the material cast during the detonation.

[0014] Lastly, it is necessary to have a dismantling method that fulfills all these requirements and that is economic, quick and effective.

Summarized Description of the Invention

[0015] The objectives of this invention are reached using a drilling and dismantling method that consists of the following stages: planning of the blast hole pattern; drilling of the holes; placing of explosives; and detonating at once a bench containing a sufficiently large volume of rocks (or two standard size benches at the same time), being that the holes are between 28 and 36 meters deep.

[0016] The method comprises the dismantling of two benches (or rocky bench) at the same time, where one bench has a free face and is above the level of the operation area, and another bench with a trapped face, which is below the level of operation area.

[0017] The operation area are areas for equipment maneuvering, including conveyor belts, or areas with a lower level that provide access to the benches. In the same mine, it is possible to have more than one operation areas, located in different levels.

[0018] It is a further object of the present invention to substantially overcome or at least ameliorate one or more disadvantages of existing arrangements.

[0019] In a first embodiment, the present invention provides a method for the Drilling and Dismantling of Rock Banks of an Iron Ore Mine, consisting of the stages of planning of the blast hole pattern; drilling of the holes; loading of explosives in the holes; and detonation of the explosives, wherein it is possible to dismantle two benches in the same time, being one bench a free face bench and above the rock bank grid, the other bench being a trapped face bench and below the rock bank grid, and the holes are drilled to a depth of between 28 and 36 meters.

Brief Description of the Figures

[0020] Example embodiments should become apparent from the following description, which is given by way of example only, of at least one preferred but non-limiting embodiment, described in connection with the accompanyingfigures:

[0021] Figure 1 reveals the upper topography of an example blasting plan that follows the precepts of this invention

[0022] Figure 2 reveals a blast hole pattern plan that follows the precepts of this invention.

[0023] Figure 3 is a cross section view of an iron ore deposit, evidencing the depth of the holes drilled according to the method of this invention.

[0024] Figure 4 is a cross section view of a pile formed after the dismantling of a rock bank, following the precepts of the state of the art.

[0025] Figure 5 is a top view of the pile evidenced in Figure 4.

[0026] Figure 6 is a cross section view of a pile formed after the dismantling of a rock bank of two benches, following the precepts of this invention.

[0027] Figure 7 is a top view of the pile evidenced in Figure 6.

[0028] Figure 8 is a top view of a rock bank, evidencing the spacing and distance between the holes used to place the explosives.

Detailed Description of the Invention

[0029] The invention consists in the application of the method for the simultaneous detonation of two rock banks 1 (also called benches) (see Figure 3). This method seeks to ensure constant feeding of the conveyor belts 2 located at the operation area and used to transport the iron ore from the mine to the processing plant.

[0030] With the use of this dismantling technique it as also possible to steer the direction of detonation of a bench 1, avoiding that detonation fragments hit the conveyor belts 2 located at the mining fronts.

[0031] All these objectives are reached with the execution of a drilling and dismantling method that incorporates the characteristics described below.

[0032] One of the main characteristics of this method is the drilling of holes 5 with an approximate depth of 30 meters, instead of the usual 10 to 15 meters, for placement of the explosive charges (see depth P of the invention and P' of the state of the art in Figure 3). With this depth, it is possible to dismantle two benches 1 at the same time, being a rock bench with a free face 6 and above the level of the operation area and another bench with a trapped face that is below the level of the operation area, generating a volume of dismantled material much greater than the volume generated in simple benches 1'. For definition of the scope of protection of this invention, "approximate depth of 30 meters" means: any metric value comprised between the depth of 28 and 36 meters.

[0033] The new blasting plan developed for this invention consists of holes 5 arranged in escalated grids (see Figure 8), this grid is dimensioned based on the geological features of the material and the degree of fracturing that is desired, and in this case paying attention to the restrictions and features of results described above. Taking these points into account, the distance to be preferably adopted between holes 5 is between 5 to 6 meters spacing J by 11 to 12 meters spacing L, totaling approximately 11 thousand square meters. The diameter of the holes , in turn, is between 20 and 30 cm, preferably 9 7/8" or 251mm.

[0034] For drilling of the holes, diesel powered rotary drilling machines or drilling machines with down the hole hammers are used. Each drilling machine is equipped with a GPS navigation system and an electronic device designed to identify variations in the resistivity of the rock to be drilled. The GPS navigation system helps in the positioning of the holes 5 and in the arrangement of these elements. The electronic device, in turn, supplies important data that facilitates calculation of the amount of explosive to be allocated to each hole, maximizing the efficiency and economy of the explosives used in the detonation process.

[0035] The explosive preferentially used for detonation is ANFO (Ammonium NitrateIFuel Oil). This explosive can also be mixed with emulsions, making it resistant to humidity and enabling it to be used in regions recently hit by rains and floods, for example. On average, this method uses between 100 and 200 tons of explosives for each detonation.

[0036] As with this method the volume of material to be dismantled by detonation is much greater than the volumes traditionally dismantled, the use of ANFO (pure or mixed with emulsions) is almost mandatory, since this explosive is more economic than most explosives available on the market. The volume of rock to be dismantled per week, per mining front, totals approximately 340.600 M3. Considering that each conveyor belt will operate continuously for 24 hours.

[0037] This number, 340.600 M3 , is reached considering the limit of 8.500 ton/h of the conveyor belts 2, an average operating yield of 62% and seven days in a week, totaling 885.500 tons of ore (average density of 2,6 ton/m3), or, approximately 340.600 m 3 of total volume in two benches.

[0038] The stages of the dismantling operation, from the execution of the holes up to the detonation, require the following time periods to be completed: six days for drilling and one day for placement of the explosive charges and detonation.

[0039] To reach a volume of 340.600 M3 , considering the 30 meter depth of the holes 5, would require a bench 1 measuring 190 m wide by 60 m in depth, or 70 m in depth by 160 m wide, or still, any other measurements that, multiplied by the 30 meter depth, result in a total volume of approximately 340.600 M3 .

[0040] It should be observed that, in the previous technique revealed in US20110175429, the dimensions of the bench 1 are: 40 m x 20 m x 10 m, totaling 8.000 m 3 of ore. This volume is forty two times less than the volume of the bench 1 explored using the present method, thus evidencing the large difference between both technologies.

[0041] The blast hole pattern used in this method is a mix between a parallel line arrangement 11, used in the first lines of dismantlement, and lines in "V" 12 for the subsequent lines as revealed in Figure 1. This blast hole pattern provides greater control in the launching of material from the holes 5 closest to the free face of the bench 6.

[0042] Linked to this blast hole pattern, the invention defines a specific timing for the detonation of the explosive charges, being that this timing is capable of determining the direction of the detonation, which should occur parallel to the direction of the conveyor belt 2.

[0043] The blast hole pattern employed also seeks to form a higher pile 3 of dismantled material 3 that maintains a height h similar to the benches before dismantling, not substantially altering the height originally occupied by the ore. With higher piles 3, the operation, is more productive for mining using bulldozers 4. Figures 4 and 5 reveal ore piles 3' of the state of the art, which were formed by a detonation performed in accordance with the blast hole pattern of the state of the art. Figures 6 and 7 reveal an ore pile 3 formed by a detonation performed in accordance with the blast hole pattern of this invention. Observe that the height h of the ore pile 3 of the invention is greater than the height h' of the ore pile of the state of the art 3' (compare Figures 6 and 4). Observe also that the fact of the height h of the pile 3 being greater facilitates the work of the bulldozers 4 (compare the distances d and d' travelled by the bulldozers in Figures 5 and 7).

[0044] It can be observed that all the characteristics mentioned in this report seek to reach a single objective: to adapt the drilling and dismantling process to a mine that uses conveyor belts 2.

[0045] Having described a few examples of the preferred embodiment of the invention, it should be pointed out that the scope of protection provided by this document includes all other reasonable alternative forms of embodiment of the invention, which is defined herein.

Claims

1. A method for the Drilling and Dismantling of Rock Banks of an Iron Ore Mine, consisting of the stages of planning of the blast hole pattern; drilling of the holes; loading of explosives in the holes; and detonation of the explosives, wherein two benches are dismantled at the same time to create at least one pile of dismantled material, being one bench a free face bench and above the level of an operation area and the other bench being a trapped face bench which is below the level of the operation area, and the holes are drilled to a depth of between 28 and 36 meters;

wherein the blast hole pattern fuses parallel lines and lines in "V"; and

wherein the blast hole pattern enables the at least one pile of dismantled materials to maintain a height similar to the height of the free face bench before detonation.

2. The method for the Drilling and Dismantling of Rock Banks of an Iron Mine, according to claim 1, wherein the blast hole pattern is designed to direct the direction of detonation of the benches.

3. The method for the Drilling and Dismantling of Rock Banks of an Iron Mine, according to claim 2, wherein the blast hole pattern has specific timing for the detonation of the explosive charges in the lines, being that this timing is capable of determining the direction of the detonation of the rock benches, which should occur parallel to the direction of conveyor belt.

4. The method for the Drilling and Dismantling of Rock Banks of an Iron Mine according to claim 1, wherein the distance adopted between holes is between 5 and 6 meters of separation by 11 to 12 meters of spacing.

5. The method for the Drilling and Dismantling of Rock Banks of an Iron Mine according to claim 1, wherein the diameter of the holes is between 20 and 30 cm.

6. The method for the Drilling and Dismantling of Rock Banks of an Iron Mine, according to claim 1, further comprising the use of between 100 and 200 tons of explosives in the holes for each detonation.

7. The method for the Drilling and Dismantling of Rock Bank of an Iron Mine s, according to claim 6, wherein the explosive used is: ANFO or a mixture of ANFO and emulsions.

8. The method for the Drilling and Dismantling of Rock Banks of Iron Ore Mine, according to any of claims 1 to 7, wherein the pile of dismantled material has a height similar to the benches before the dismantling.

Vale S.A. Patent Attorneys for the Applicant/Nominated Person SPRUSON & FERGUSON