Mining width controlled blasting method for deep hole mining of extremely thin ore bodies

Abstract

The controlled blasting method for deep hole mining of extremely thin ore bodies determines the waste rock inflow rate according to the grade and economic value of the ore body, and then calculates the maximum offset of the blasthole, blasthole depth, drill rod diameter, blasthole depth and mining width through formula calculation. The diameter of the explosive is determined by combining the formula and field tests. A casing with an inner diameter equal to the diameter of the explosive is selected and installed in a large-diameter deep hole. The gap between the casing and the deep hole is backfilled, and explosives are installed in the casing to blast the ore. This effectively controls the mining width of deep hole mining of extremely thin ore bodies and has the advantages of effectively reducing the unit consumption of explosives, mining costs, mining depletion rate and loss rate.

Description

Technical Field

[0001] The invention relates to underground mine deep hole mining blasting technology, in particular to a deep hole mining width controlled blasting method for an extremely thin ore body. Background Art

[0002] Mining operations are generally categorized into shallow-hole blasting and deep-hole blasting. According to the national "Safety Regulations for Blasting GB6722," shallow-hole blasting refers to blasting operations with a blasthole diameter of 50mm or less and a depth of 5m or less; deep-hole blasting refers to blasting operations with a blasthole diameter greater than 50mm and a depth greater than 5m. In engineering applications, deep-hole blasting of 12m to 16m is generally referred to as medium-deep-hole blasting, which falls within the deep-hole blasting range.

[0003] Shallow hole blasting is currently commonly used to mine extremely thin ore bodies, such as the ore-retention method. However, these methods suffer from significant mining and cutting workloads, low ore removal per blast, low recovery efficiency, and high mining costs. For example, patent CN 111550247 A provides a "mining method for gently inclined, layered, extremely thin ore bodies based on shallow hole blasting." This method uses blastholes of 1800 mm in length. Another example, patent CN 106150505 A proposes a "fine blasting process for extremely thin ore bodies." This process involves placing side holes on either side of the ore body and a central hole in the center of the ore body. The side holes are first blasted to separate the ore body from the surrounding rock, followed by the central hole to release the ore. Both the side and central holes have diameters of 32-35 mm and depths of 3-6 m. These blasthole diameters fall within the shallow hole blasting range, while the depths fall within the shallow to deep hole range. However, this method maintains the essence of shallow hole blasting, and the addition of side holes significantly increases costs.

[0004] According to engineering experience, the size of the minimum resistance line of blasting is 20 to 30 times the diameter of the explosive. The larger the blast hole, the larger the blasting and crushing area. Deep hole blasting uses a charge loader or a charging trolley to fill the entire hole with granular or powdered bulk explosives. If the large-diameter deep hole process of conventional deep hole blasting is used for mining extremely thin ore bodies, the blasting and crushing area is large, resulting in the mining width (mining thickness) being much larger than the ore body thickness, resulting in a large amount of waste rock mixed in and a large loss of ore grade. If a small-diameter deep hole process is used to mine extremely thin ore bodies in combination with shallow hole blasting and deep hole blasting technology, a small-diameter drill rod must be used for the construction of small-diameter blast holes. The smaller the drill rod diameter, the greater the blast hole deflection rate, causing the blast hole to deviate from the ore body to the waste rock, resulting in a large amount of blasting waste rock mixed in, a large amount of ore loss, and reduced grade.

[0005] In summary, for the mining of extremely thin ore bodies, there is currently no suitable deep-hole technology or method that can take into account production capacity, control mining width, reduce mining costs, and ensure dilution and loss rate.

[0006] Therefore, it is particularly urgent to develop a deep hole mining width controlled blasting method for extremely thin ore bodies. Summary of the Invention

[0007] The task of the present invention is to overcome the shortcomings of the existing technology and provide a deep hole mining width controlled blasting method for ultra-thin ore bodies, which can not only use deep hole mining to improve the production capacity of ultra-thin ore bodies, but also control the mining width to reduce mining costs and dilution losses.

[0008] The task of the present invention is accomplished by the following technical solutions:

[0009] The controlled blasting method for deep hole mining of extremely thin ore bodies determines the waste rock inflow rate based on the ore body grade and economic value, and then uses a formula to calculate the maximum blasthole offset, blasthole depth, drill rod diameter, blasthole depth and mining width. The explosive diameter is determined by combining the formula and field tests. A casing with an inner diameter equal to the explosive diameter is selected and installed in a large-diameter deep hole. The gap between the casing and the deep hole is backfilled, and explosives are installed in the casing to blast the ore. This effectively controls the mining width of deep hole mining of extremely thin ore bodies, reduces explosive consumption per unit, mining costs, mining depletion rate and loss rate. It specifically includes but is not limited to the following process steps and conditions:

[0010] (1) Determine the waste rock mixing rate based on the grade of the extremely thin ore body and its market economic value;

[0011] (2) The maximum blasthole offset is calculated using the formula = 0.5rt / (1-r), where r is the waste rock inflow rate and t is the ore body thickness;

[0012] (3) Calculate the blasthole depth by the formula = k / e, where e is the maximum deflection rate of the drill rod. When the drill rod diameter is different, the drill rod deviation rate is different. Determine the blasthole depth and drill rod diameter, and select the matching drill bit diameter according to the drill rod diameter. k is the maximum deviation of the blasthole;

[0013] (4) Calculate the sampling width by the formula = t + 2k;

[0014] (5) Combine the formula to calculate the explosive diameter = c / (40-60) and the blasting test to adjust the explosive diameter on site to control the actual blasting width, where c is the width, and finally determine the explosive diameter;

[0015] (6) Select a casing with an inner diameter equal to the diameter of the explosive and install it in the deep hole, backfilling the gap between the casing and the blasthole;

[0016] (7) Install explosives in the casing to blast the falling ore.

[0017] Compared with the prior art, the present invention has the following advantages or effects:

[0018] Due to the organic combination of large-diameter deep holes and small-diameter explosives, the deep hole mining width of extremely thin ore bodies can be effectively controlled, thereby reducing the unit consumption of explosives, mining costs, mining depletion and loss rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a layout diagram for implementing the controlled blasting method for deep hole mining of steeply inclined and extremely thin ore bodies involved in an embodiment of the present invention.

[0020] Figure 2 yes Figure 1 Cross-section along line I-I.

[0021] Figure 3 yes Figure 1 Cross-sectional view along line II-II.

[0022] The symbols in the accompanying drawings represent:

[0023] 1. Sectional return air tunnel 2. Cutting shaft (slot) 3. Sectional transport tunnel 4. Casing 5. In-hole backfill 6. Ore body thickness centerline 7. Ore body hanging wall boundary 8. Ore body footwall boundary 9. Footwall blasting boundary 10. Hanging wall blasting boundary ①-③. Blasthole α. Ore body inclination k. Maximum blasthole offset t. Ore body thickness c. Mining width d1. Drill pipe diameter d2. Drill bit diameter d3. Explosive diameter e. Maximum drill pipe deflection h. Blasthole depth r. Waste rock inflow rate

[0024] The following is a further detailed description of the invention in conjunction with the accompanying drawings. DETAILED DESCRIPTION

[0025] like Figure 1-3 As shown, the present invention provides a method for controlled blasting in deep hole mining of an ultra-thin ore body. The method determines the waste rock inflow rate based on the ore body grade and economic value, then calculates the maximum blasthole offset, blasthole depth, drill rod diameter, blasthole depth, and mining width using a formula. The explosive diameter is determined by combining the formula with field tests. A casing with an inner diameter equal to the explosive diameter is selected and installed in a large-diameter deep hole. The gap between the casing and the deep hole is backfilled, and explosives are installed in the casing to blast the ore. This method effectively controls the mining width of ultra-thin ore body deep hole mining, reduces explosive consumption per unit, mining costs, mining depletion rate, and loss rate. The method specifically includes, but is not limited to, the following process steps and conditions:

[0026] (1) Determine the waste rock mixing rate r based on the grade of the extremely thin ore body and its market economic value;

[0027] (2) The maximum blasthole offset is calculated using the formula (k) = 0.5rt / (1-r), where r is the waste rock inflow rate and t is the ore body thickness;

[0028] (3) Calculate the blasthole depth (h) by the formula: k / e, where e is the maximum deflection rate of the drill rod. When the drill rod diameter (d1) is different, the drill rod deflection rate (e) is different. Determine the blasthole depth (h) and the drill rod diameter (d1), and select the matching drill bit diameter (d2) based on the drill rod diameter (d1);

[0029] (4) Calculate the sampling width by the formula (c) = t + 2k;

[0030] (5) Combine the formula to calculate the explosive diameter (d3) = c / (40-60) and the blasting test to adjust the explosive diameter (d3) on site to control the actual blasting width (c), and finally determine the explosive diameter (d3);

[0031] (6) Select a casing (4) with an inner diameter equal to the explosive diameter (d3) and install it in the deep hole, and backfill the gap between the casing (4) and the blasthole (①-③);

[0032] (7) Install explosives in the casing (4) to blast the falling ore.

[0033] The process of the present invention may further be:

[0034] According to the mining process, two blasting techniques, namely, upward deep hole blasting or downward deep hole blasting, are selected. In the downward deep hole, crushed stone, fine sand or rock powder is used to backfill the gap between the casing (4) and the blast hole (①-③), while in the upward deep hole, cementing material or expansion material is used to backfill the gap between the casing (4) and the blast hole (①-③).

[0035] The casing (4) is a PE pipe.

[0036] The wall thickness of the casing (4) is determined according to the hole depth and the mine pressure.

[0037] If affected by groundwater, the casing (4) at the bottom of the hole is sealed to achieve water-proof blasting.

[0038] Example

[0039] Reference Figure 1-3 The ore body thickness (t) of a certain mining site is 0.8 to 1.8m, extremely thin ore body to thin ore body, the average ore body thickness (t) is 1.4m, the average ore body inclination (α) is 70°, and the waste rock inflow rate (r) is determined to be no more than 15% based on the ore grade and ore market price. The maximum blasthole offset (k) is calculated by the formula = 0.5rt / (1-r), and the result is (k) is 0.12m.

[0040] A drill rod with a maximum deflection rate (e) of 1% and a diameter of 56 mm was selected to construct blastholes (①-③). The blasthole depth (h) was 12 m according to the formula (blasthole depth (h) = k / e). A matching 64 mm drill bit diameter (d2) was selected based on the drill rod diameter (d1).

[0041] The mining width (c) = t + 2k is calculated to be 1.64m, and the explosive diameter (d3) is calculated to be in the range of 27mm to 41mm using the formula explosive diameter (d3) = c / (40 to 60). The explosive diameter (d3) is finally determined to be 32mm through on-site blasting tests.

[0042] A segmented return air tunnel (1), a cutting shaft or trough (2) and a segmented transport tunnel (3) are constructed in the ore body according to conventional technology.

[0043] Downward deep hole blasting is adopted for mining. Blast holes (①-③) are constructed along the center line (6) of the ore body thickness and are inclined toward the boundary (8) of the lower wall of the ore body. PE casings (4) with an inner diameter of 32 mm and a wall thickness of 3 mm are installed in the blast holes (①-③). The gaps between the casings (4) and the blast holes (①-③) are backfilled with fine sand and gravel (5). Bulk granular explosives are used for blasting. The blast holes (①-③) are fully charged with explosives through a charge loader. The blast holes (①-③) are detonated in sequence to realize the lateral drop of ore from the deep hole toward the cutting well (2).

[0044] Because the blastholes (①-③) are deflected toward the ore body footwall boundary (8), the distance from the blasthole to the ore body upper wall boundary (9) becomes larger and larger from the hole mouth to the hole bottom, and the distance from the footwall boundary (8) becomes smaller and smaller. The actual blasting range is Figure 3 The area between the middle and lower wall blasting boundary (9) and the upper wall blasting boundary (10); the area between the upper wall boundary (7) and the upper wall blasting boundary (10) of the ore body and the area between the lower wall boundary (8) and the lower wall blasting boundary (9) of the ore body are blasting waste rock areas.

[0045] Furthermore, due to the greater influence of groundwater, the bottom side of the casing (4) is sealed by hot melting, and the opening of the casing (4) is appropriately raised by about 5 cm to prevent groundwater from entering the casing (4) to achieve water-proof blasting.

[0046] As described above, the present invention can be better implemented. The above embodiments are only the best implementation methods of the present invention, but the implementation methods of the present invention are not limited to the above embodiments. Other changes, modifications, replacements, combinations, and simplifications made without departing from the spirit and principles of the present invention should be considered equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. The controlled blasting method for deep-hole mining of extremely thin ore bodies involves determining the waste rock mixing rate based on the ore body grade and economic value. The maximum blasthole offset, blasthole depth, drill rod diameter, blasthole depth, and mining width are then calculated using a formula. The explosive diameter is determined by combining the formula with field tests. A casing with an inner diameter equal to the explosive diameter is selected and installed in a large-diameter deep hole. The gap between the casing and the deep hole is backfilled, and explosives are installed in the casing to blast the ore. This method can effectively control the mining width of deep-hole mining of extremely thin ore bodies, reduce explosive consumption per unit, mining costs, mining depletion rate, and loss rate. The specific process steps and conditions include the following: (1) Determine the waste rock mixing rate r based on the grade of the extremely thin ore body and its market economic value; (2) The maximum blasthole offset is calculated using the formula (k) = 0.5rt / (1-r), where r is the waste rock mixing rate and t is the ore body thickness; (3) Calculate the blasthole depth (h) by the formula: k / e, where e is the maximum deflection rate of the drill rod. When the drill rod diameter (d1) is different, the drill rod deflection rate (e) is different. Determine the blasthole depth (h) and the drill rod diameter (d1), and select the matching drill bit diameter (d2) based on the drill rod diameter (d1); (4) Calculate the sampling width by the formula (c) = t + 2k; (5) Combine the formula to calculate the explosive diameter (d3) = c / (40-60) and the blasting test to adjust the explosive diameter (d3) on site to control the actual blasting width (c), and finally determine the explosive diameter (d3); (6) Select a casing (4) with an inner diameter equal to the explosive diameter (d3) and install it in the deep hole, and backfill the gap between the casing (4) and the blasthole (①-③); (7) Install explosives in the casing (4) to blast the falling ore.

2. The method according to claim 1, wherein: According to the mining process, two blasting techniques, namely, upward deep hole blasting or downward deep hole blasting, are selected. In the downward deep hole, crushed stone, fine sand or rock powder is used to backfill the gap between the casing (4) and the blast hole (①-③), while in the upward deep hole, cementing material or expansion material is used to backfill the gap between the casing (4) and the blast hole (①-③).

3. The method according to claim 1, wherein: The casing (4) is a PE pipe.

4. The method according to claim 1 or 3, wherein: The wall thickness of the casing (4) is determined according to the hole depth and the mine pressure.

5. The method according to claim 1, wherein: If affected by groundwater, the casing (4) at the bottom of the hole is sealed to achieve water-proof blasting.

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