Large-diameter sub-presplitting blasting method for open-pit mining

Abstract

The invention relates to an open-pit mining large-diameter sub-presplitting blasting method which comprises the steps that blast holes are arranged, specifically, a row of presplitting blast holes and a plurality of rows of main blast holes are formed in a working step of a stope, the presplitting blast holes are formed in the last row of the working step of the stope, and the presplitting blast holes are formed by half-depth presplitting blast holes and full-depth presplitting blast holes in an alternating mode; blast hole charging: charging the main blast hole according to the conventional design; the charging structure of the half-depth presplitting blast hole comprises a filling section and a charging blasting section. The charging structure of the full-depth presplitting blast hole comprises an air section, a filling section and a charging blasting section. And after the blast holes are charged, detonating cords of the explosive strings are connected to detonating points, and the detonating mode that the pre-splitting blast hole rows are detonated before all the main blast holes, the pre-splitting blast hole rows are detonated in a one-hole-one-sound staggered mode towards the half-depth pre-splitting blast holes and the full-depth pre-splitting blast holes in the same direction, and the half-depth pre-splitting blast holes are detonated before the adjacent full-depth pre-splitting blast holes is adopted for detonating. According to the method, the blasting effect can be remarkably improved by optimizing the blast hole arrangement, the charging structure and the detonating sequence.

Description

Technical Field

[0001] The present invention belongs to the technical field of open-pit mining, and particularly relates to a large-diameter sub-pre-splitting blasting method for open-pit mining. Background Art

[0002] In open-pit mine mining, the blasting operation of the working bench is a key link to achieve ore and rock mining. The traditional open-pit stope working bench blasting usually adopts large-diameter deep-hole blasting technology, and its construction process includes steps such as design, hole layout, drilling, charging, blasting, loading, and slope trimming. However, there are many problems with this conventional blasting method. Especially when pre-splitting blast holes are not set, the impact on the rock mass of the rear and side working benches after blasting is relatively large, resulting in rock mass cracking. This cracking phenomenon will cause the energy to leak in advance during subsequent blasting of the rear and side benches, thereby deteriorating the blasting effect, resulting in uneven block size, high large block rate, frequent occurrence of bottom problems, etc., seriously affecting the loading operation efficiency and increasing the safety hazards of transportation operations.

[0003] In addition, although the traditional bench pre-splitting blasting method for slope protection can improve these problems, its construction difficulty is large, cost is high, and construction period is long. For example, the number of blast holes for pre-splitting blasting is usually 2 - 5 times that of conventional blast holes, the hole diameter is only 1 / 3 - 1 / 4 of that of conventional blast holes, and most of them are inclined holes, which greatly increases the difficulty of drilling operations. At the same time, the charging process for pre-splitting blasting is relatively complex. Usually, small-diameter cartridges are used for charging, the charging period is long, and it is difficult to ensure the charging qualification rate. These problems not only limit the wide application of pre-splitting blasting technology in the open-pit stope working bench, but also increase the construction cost and management difficulty. Summary of the Invention

[0004] In view of the above problems, the present invention proposes a large-diameter sub-pre-splitting blasting method for open-pit mining, aiming to solve the problems existing in the traditional blasting method by optimizing the hole layout and charging structure, and improving the blasting effect and economy.

[0005] The specific technical solution is as follows: A large-diameter sub-pre-splitting blasting method for open-pit mining includes the following steps: S1. Arranging blast holes: A row of pre-splitting blast holes and multiple rows of main blast holes are arranged on the working bench of the stope. The pre-splitting blast holes are arranged in the last row of the working bench of the stope. The pre-splitting blast holes are alternately composed of semi-depth pre-splitting blast holes and full-depth pre-splitting blast holes. The hole depth H of the semi-depth pre-splitting blast holes is half of the hole depth H of the full-depth pre-splitting blast holes; the adjacent rows of main blast holes and between the full-depth pre-splitting blast holes and the adjacent rows of main blast holes are arranged in a plum blossom pattern. The semi-depth pre-splitting blast holes are arranged in the middle position between two adjacent full-depth pre-splitting blast holes to supplement the blast hole density of the full-depth pre-splitting blast holes to ensure the expected sub-pre-splitting effect; This blast hole arrangement method uses a pre-splitting blast hole row composed of alternately arranged semi-depth pre-splitting blast holes and full-depth pre-splitting blast holes to replace the small-diameter inclined pre-splitting holes and buffer blast holes in the traditional pre-splitting blasting method for the slope bench (such as Figure 4 3 and 4 in

[0006] ). This can greatly simplify the blast hole layout workload, reduce the construction difficulty, and does not require additional purchase of slope drilling rigs for laying small-diameter inclined pre-splitting holes, thus reducing the construction cost.

[0007] The charge structure of the full-depth pre-splitting blast hole 12 includes an air section Lk’, a stemming section Lt’, and a charge blasting section Lb’. The setting of the air section Lk’ can appropriately reduce the charge amount, and at the same time, the reserved blank section can guide the semi-depth pre-splitting blast holes to pre-split towards the air sections on both sides, achieving a better pre-splitting effect. It can be seen that the air section is the key setting for guiding the pre-splitting direction in pre-splitting blasting operations. During the construction process, the accuracy and reliability during stemming and charging should be ensured, and enough air section should be reserved.

[0008] The stemming section Lt’ is also stemmed with stemming clay. Since the charge blasting section Lb’ is not clamped by the explosives of the semi-depth pre-splitting blast holes and the periphery of the blasting is in the deep part, there is a clamping effect of the rock, and a stronger blasting power is required for fracturing to ensure a better fracturing effect. Therefore, the whole section is charged with large-diameter cartridges and a charge method with controllable non-coupling in both the radial and axial directions. In addition, since the bottom of the semi-depth pre-splitting blast hole is the enhanced charge section with a large blasting force, the stemming section Lt’ of the full-depth pre-splitting blast hole 12 should be 1 m higher than the bottom of the semi-depth pre-splitting blast hole to ensure the overall blasting effect. S3. Connecting and initiating: After the blast holes are charged, connect the detonating cord of the charge string to the initiation point. The pre-splitting blast hole row is initiated before all the main blast holes. The pre-splitting blast hole row detonates one hole at a time in an alternating manner for the semi-depth pre-splitting blast holes and the full-depth pre-splitting blast holes in the same direction, and the semi-depth pre-splitting blast holes detonate ahead of the adjacent full-depth pre-splitting blast holes.

[0009] This initiation method can effectively ensure that the pre-splitting of the semi-depth pre-splitting blast holes is guided by the air section of the full-depth pre-splitting blast holes, so that the pre-splitting blasting of the next full-depth pre-splitting blast hole can further fracture along the fracture direction guided by the previous semi-depth pre-splitting blast hole, effectively ensuring the pre-splitting effect of the overall design structure.

[0010] Furthermore, the aperture R, hole depth H, and overdrill h of the full-depth presplitting blast holes described in step S1 are the same as those of the main blast holes, and the aperture R of the half-depth presplitting blast holes is the same as that of the main blast holes. Such a unified dimension design makes the layout and construction of the full-depth presplitting blast holes and half-depth presplitting blast holes simpler and faster, and can be completed with the same drilling rig as the main blast holes.

[0011] Furthermore, the row spacing between the presplitting blast hole rows and the adjacent main blast hole rows, and between two adjacent main blast hole rows described in step S1 are all equal (both are b in Figure 1 ), and the hole spacing between two adjacent full-depth presplitting blast holes and between two adjacent main blast holes in each row are all equal (both are a in Figure 1 ). The settings of equal row spacing and equal hole spacing are beneficial to determining a consistent charging standard and ensuring the overall blasting effect.

[0012] Furthermore, the enhanced charging section of the half-depth presplitting blast holes and the charging and blasting section of the full-depth presplitting blast holes described in step S2 are both charged with large-diameter cartridges the same as those of the main blast hole 2. On the premise of ensuring the blasting effect, the same cartridges are more convenient for charging operations.

[0013] Furthermore, the initiation method of the multi-row main blast holes in step S3 is to take every two adjacent rows as a group. Starting from the group close to the presplitting blast holes, the groups are initiated downward in sequence, and the two main blast hole rows in each group are initiated in a staggered manner with one hole ringing at a time in the same direction, and the front-row main blast holes are initiated ahead of the rear-row main blast holes. Such an alternating and sequential initiation method can make the blasting energy act on the rock mass more evenly, avoiding problems such as insufficient local fragmentation and uneven block size caused by concentrated energy release, and improving the fragmentation quality of the rock mass.

[0014] Advantages of the present invention: By optimizing the blast hole layout, charging structure, and initiation sequence, the present invention significantly improves the blasting effect, significantly improves the bench slope quality, reduces the construction cost and difficulty, enhances the safety and reliability, increases the economy and practicability, provides an efficient, safe, and economical blasting method for open-pit mine mining, and is of great significance for improving the mining efficiency, ensuring the slope stability, reducing the mining cost, and protecting the environment, providing strong support for the sustainable development of the mine.

[0015] (1) Optimized blast hole layout: By alternately arranging half-depth presplitting blast holes and full-depth presplitting blast holes and combining with the plum blossom hole layout method, the blast hole density is effectively supplemented, ensuring the expected sub-presplitting effect. Such a layout method can better guide the release direction of the blasting energy, making the presplitting effect more uniform and stable.

[0016] (2) Precise charging structure: The semi-depth pre-splitting blast holes use small-diameter cartridges for air-decoupled charging, reducing the impact fracture on the rear of the working bench; the full-depth pre-splitting blast holes use large-diameter cartridges and non-coupled charging to ensure the fracture effect during the pre-splitting process. This charging method can effectively control the distribution of blasting energy, reduce the large block rate and bottom problem, and improve the fragmentation quality of the rock mass.

[0017] (3) Unified hole diameter and charging standard, greatly reducing the construction difficulty, reducing the complexity and uncertainty during the charging process, and making the construction more simple and fast.

[0018] (4) Rational initiation sequence: The pre-splitting blast hole row detonates prior to the main blast holes, and the semi-depth pre-splitting blast holes and full-depth pre-splitting blast holes detonate alternately, which can effectively guide the pre-splitting direction and ensure the overall pre-splitting effect. The main blast holes use a group-by-group alternate detonation method, making the blasting energy act on the rock mass more evenly and avoiding insufficient local fragmentation. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the plan layout diagram of the blast holes of the present invention; Figure 2 is Figure 1 the transverse sectional view of the pre-splitting blast holes in Figure 3 is Figure 1 the longitudinal sectional view of the full-depth pre-splitting blast holes and main blast holes in Figure 4 is the sectional layout diagram of the traditional slope-retaining blast holes; Figure 5 is Figure 2 the charging schematic diagram of the pre-splitting blast holes; Figure 6 is Figure 2 the fracture schematic diagram of the pre-splitting blast holes; Figure 7 is Figure 1 the initiation network schematic diagram of Figure 8 is the on-site layout scene diagram of the pre-splitting blast holes; Figure 9 is the on-site charging scene diagram of the semi-depth pre-splitting blast holes; Figure 10 is the on-site charging scene diagram of the full-depth pre-splitting blast holes; Figure 11 is the slope scene diagram with relatively serious fracture after the daily blasting of the original working bench; Figure 12 is the slope scene diagram of the working bench after the implementation of Example 1; Figure 13 is the slope scene diagram of the working bench after the implementation of Comparative Example 1; In the figure: 1 - presplitting blast hole, 11 - half - depth presplitting blast hole, 12 - full - depth presplitting blast hole; 2 - main blast hole, 21 - front - row main blast hole, 22 - rear - row main blast hole; 3 - small - diameter inclined presplitting hole; 4 - buffer blast hole; a - hole spacing; b - row spacing; H - hole depth. Detailed implementation method

[0020] In order to make the technical problems and technical solutions solved by the present invention clearer and more understandable, the following further details the present invention in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Embodiment 1

[0021] Taking the working bench of a large open - pit mine during normal operation as the implementation object, the basic parameters are: bench height 15m, bench slope angle 60°, the rock is semi - hard rock with a stability coefficient f of (4 - 6), and the degree of rock mass fissure development is moderate; the design parameters of the main blast holes: drilling diameter D is 140mm, hole row spacing (a×b) is 6m×4m, hole depth H is 15m (vertical hole), and the over - depth h is designed as 1m, and the stemming length is 4m.

[0022] Using the method described in the present invention to implement on the primary blasting unit in this area, the specific steps are as follows: S1. Layout of blast holes: (1) After the site is leveled and surveyed, the hole layout and drilling operations are carried out according to the design. As shown in the figure, according to the design parameters of the main blast holes 2 and the rule that the main blast holes between adjacent rows are arranged in a plum - blossom pattern, the main blast holes 2 in the implementation area are arranged in four rows. The presplitting blast holes 1 are arranged in the last row of the working bench. According to the rule that the full - depth presplitting blast holes 12 and the main blast holes 2 in the adjacent row are arranged in a plum - blossom pattern, the row spacing between the presplitting blast hole row and the adjacent main blast hole row is b, and the hole spacing between two adjacent full - depth presplitting blast holes is a, the layout of the full - depth presplitting blast holes 12 is completed; then the half - depth presplitting blast holes 11 are arranged at the middle position (a / 2) between two adjacent full - depth presplitting blast holes 12 to supplement the hole density of the full - depth presplitting blast holes 12. The on - site layout of the presplitting blast holes 1 is as shown in the figure. Figure 1 As shown in the figure. Figure 8 As shown.

[0023] (2) After the layout is completed, drilling is carried out according to the following parameters to obtain the structures of the presplitting blast holes 1 and the main blast holes 2 as shown in the figure: Figure 2 Figure 3 As shown in the figure. For the main blast holes 2 and the full - depth presplitting blast holes 12: the drilling diameter is 140mm, and the hole depth H is 16m (vertical hole, including the 1m of over - depth h); for the half - depth presplitting blast holes 11: the drilling diameter is 140mm, and the hole depth is H / 2 = 8m (vertical hole); (3) After drilling, carry out guarantee work such as hole inspection and hole measurement to ensure the drilling quality.

[0024] S2, Blasthole Charging and Stemming: (1) The charging structure of the four rows of main blastholes 2 is charged and stemmed according to the normal working bench charging and blasting structure.

[0025] (2) It is extremely important to charge the pre-splitting blastholes strictly according to the design. As Figure 5 shown, the charging structure of the semi-depth pre-splitting blasthole 11 includes a stemming section Lt and a charging and blasting section Lb. Among them, the stemming section Lt is taken as 2m according to the formula Lt = (16 - 32)D and on-site experience, and it is stemmed with a combination of stemming clay and rock powder; the charging and blasting section Lb is 6m, and the decoupled interval charging method is used for charging. Among them, the upper weak charging section uses small-diameter cartridges (32mm) for air interval charging, and the bottom enhanced charging section uses large-diameter cartridges (90mm) for charging. The on-site charging is as Figure 9 shown.

[0026] (3) As Figure 5 shown, the charging structure of the full-depth pre-splitting blasthole 12 includes an air section Lk’, a stemming section Lt’ and a charging and blasting section Lb’. In order to ensure the guiding effect of the air section Lk’, the air section Lk’ is designed to be 7m; considering that the bottom of the semi-depth pre-splitting blasthole is the enhanced charging section, and the charging and blasting section Lb’ uses large-diameter cartridges with greater power, the stemming section Lt’ is taken as 3m according to the formula Lt = (16 - 32)D and on-site experience; the charging and blasting section Lb’ is 6m, and large-diameter cartridges (90mm) are used for charging to ensure the fracturing effect in the deep part. The on-site charging is as Figure 10 .

[0027] (4) Connection and Initiation: After the blasthole charging is completed, according to the Figure 7 shown initiation network, connect the detonating cords of all the cartridge strings to the initiation point for initiation. The specific initiation method is: (1) As Figure 7 shown, the first row of pre-splitting blastholes is initiated before all the main blastholes 2. The first row of pre-splitting blastholes is initiated alternately one hole at a time from the right to the left for the semi-depth pre-splitting blasthole 11 and the full-depth pre-splitting blasthole 12, and the semi-depth pre-splitting blasthole 11 is initiated ahead of the adjacent full-depth pre-splitting blasthole 12. This initiation method, as Figure 6 shown, can effectively ensure that the pre-splitting of the semi-depth pre-splitting blasthole 11 is guided by the air section of the full-depth pre-splitting blasthole 12, so that the pre-splitting blasting of the next full-depth pre-splitting blasthole can be further fractured along the fracturing direction guided by the previous semi-depth pre-splitting blasthole, effectively ensuring the pre-splitting effect of the overall design structure.

[0028] After the pre-splitting blast holes 1 are detonated, the four rows of main blast holes 2 are divided into two groups. When detonating, start from the group close to the pre-splitting blast holes and detonate each group downward in turn. For each group, the front row main blast holes 21 and the rear row main blast holes 22 of the two rows of main blast holes are detonated alternately one hole at a time from right to left, and the front row main blast holes 21 are detonated in advance of the rear row main blast holes 22. Such an alternating and sequential detonation method can make the blasting energy act on the rock mass more evenly, avoid problems such as insufficient local fragmentation and uneven block size caused by concentrated energy release, and improve the fragmentation quality of the rock mass.

[0029] The blasting effect in this area: Use Figure 12 Comparison Figure 11 It can be seen that although the working bench does not form the same trace rate as that of conventional pre-splitting blast hole blasting, after blasting, it effectively improves the impact and cracking on the unblasted rock mass at the rear and sides, also greatly improves the flatness of the working bench slope, and further improves the blasting fragmentation and the blasting efficiency and quality of the later working bench. Comparative Example 1

[0030] The implementation object of this comparative example belongs to the same area as that of Example 1. The difference between the method adopted in this comparative example and that in Example 1 is that: in this comparative example, only full-depth pre-splitting blast holes 12 are arranged in the pre-splitting blast hole row, and half-depth pre-splitting blast holes 11 are not arranged. And the full-depth pre-splitting blast holes are all charged with air interval charging using large-diameter cartridges (90 mm). Other hole pattern parameters remain unchanged, and the connection detonation method still adopts the hole-by-hole detonation method; after blasting, the overall muck pile and slope improvement are not obvious, and the cracking at the rear is more obvious (as Figure 13 shown), further verifying the rationality and practicability of the hole layout method and charging method of the present invention.

[0031] The present invention has been described in detail through specific and preferred embodiments, but those skilled in the art should understand that the present invention is not limited to the above-described embodiments. Any modifications, equivalent replacements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A large-diameter sub-pre-splitting blasting method for open-pit mining, characterized in that, It includes the following steps: S1. Borehole arrangement: A row of presplitting boreholes and multiple rows of main boreholes are arranged on the working bench of the stope. The presplitting boreholes (1) are arranged in the last row of the working bench of the stope. The presplitting boreholes (1) are alternately composed of semi-depth presplitting boreholes (11) and full-depth presplitting boreholes (12). The hole depth H of the semi-depth presplitting boreholes (11) is half of the hole depth H of the full-depth presplitting boreholes (12). The main boreholes (2) in adjacent rows and between the full-depth presplitting boreholes (12) and the main boreholes (2) in adjacent rows are arranged in a plum blossom pattern. The semi-depth presplitting boreholes (11) are arranged in the middle position between two adjacent full-depth presplitting boreholes (12) to supplement the borehole density of the full-depth presplitting boreholes (12). S2. Borehole charging: Charge the main boreholes (2) according to the conventional design. The charging structure of the semi-depth presplitting boreholes (11) includes a stemming section and a charging and blasting section. The stemming section is stemmed with stemming clay, and the charging and blasting section is charged by an uncoupled interval charging method. Among them, the weak charging section in the upper part is charged by air interval charging with small-diameter cartridges, and the enhanced charging section at the bottom is charged with large-diameter cartridges. The charging structure of the full-depth presplitting boreholes (12) includes an air section, a stemming section, and a charging and blasting section. The air section can guide the semi-depth presplitting boreholes (11) to presplit towards the air sections on both sides. The stemming section is also stemmed with stemming clay. The charging and blasting section is charged with large-diameter cartridges and a charging method that is both radially and axially uncoupled and controllable. At the same time, the stemming section of the full-depth presplitting boreholes (12) should be 1 m higher than the bottom of the semi-depth presplitting boreholes (11). S3. Connection and initiation: After the boreholes are charged, connect the detonating cords of the cartridge strings to the initiation point. The presplitting boreholes (1) row is initiated prior to all the main boreholes (2). The presplitting boreholes (1) row is initiated in a way that the semi-depth presplitting boreholes (11) and the full-depth presplitting boreholes (12) detonate one by one in the same direction with an alternating initiation, and the semi-depth presplitting boreholes (11) initiate ahead of the adjacent full-depth presplitting boreholes (12).

2. The large-diameter sub-pre-splitting blasting method for open-pit mining according to claim 1, characterized in that In step S1, the aperture R, hole depth H, and overbreak h of the full-depth presplitting boreholes (12) are the same as those of the main boreholes (2), and the aperture R of the semi-depth presplitting boreholes (11) is the same as that of the main boreholes (2).

3. A large-diameter sub-pre-splitting blasting method for open-pit mining according to claim 1 or 2, characterized in that, In step S1, the row spacing between the presplitting boreholes (1) row and the adjacent main boreholes (2) row, and between two adjacent main boreholes (2) rows are all equal. The hole spacing between two adjacent full-depth presplitting boreholes (12) and between two adjacent main boreholes (2) in each row are all equal.

4. A large-diameter sub-pre-splitting blasting method for open-pit mining according to claim 3, characterized in that, In step S2, the enhanced charging section of the semi-depth presplitting boreholes (11) and the charging and blasting section of the full-depth presplitting boreholes (12) are both charged with the same large-diameter cartridges as the main boreholes (2).

5. A large-diameter sub-pre-splitting blasting method for open-pit mining according to claim 4, characterized in that, In step S3, the initiation method of the multiple rows of main boreholes (2) is to take every two adjacent rows as a group. Starting from the group close to the presplitting boreholes (1), initiate them downward row by row in sequence. And for the two main boreholes (2) rows in each group, the front-row main boreholes (21) and the rear-row main boreholes (22) detonate one by one in the same direction with an alternating initiation, and the front-row main boreholes (21) initiate ahead of the rear-row main boreholes (22).

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