Blasting control method for creating free surface through simultaneous sound of front row holes in slag pressing blasting area in advance

Abstract

The invention provides a blasting control method for simultaneously creating a free surface in advance by front-row holes in a slag pressing blasting area, which comprises the following steps of: arranging front-row blast holes and rear-row blast holes: arranging the front-row holes in the slag pressing area along a free surface direction, arranging rear-row holes in a main blasting area, and arranging according to a preset hole distance, a preset row distance, a preset hole depth and a preset charging coefficient; the front-row holes are set to be at the same detonation moment, so that synchronous detonation of the front-row holes earlier than that of the rear-row holes is achieved, the same multi-section charging is conducted in the blast holes of the front-row holes, and multi-section detonator detonation can be conducted in the same high-frequency millisecond detonation mode; setting delayed detonation of the rear row holes: setting the detonation moment of the rear row holes to be 10-20ms after the last section of detonation moment of the adjacent front row holes; and detonating implementation: detonating control is carried out by adopting a blasting network established by digital electronic detonators. According to the method, a continuous and stable free surface can be formed in the slag pressing blasting area, the crushing effect of follow-up blasting is improved, and the boulder yield is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of mine blasting engineering, and in particular to a blasting control method for creating a free surface by blasting a front row of holes in a slag blasting zone in advance. Background Art

[0002] Deep-hole blasting on benches in open-pit mines widely uses micro-difference detonation in separate rows and at different times to achieve efficient crushing and reasonable throwing while meeting safety and environmental protection constraints. As the hardness of the ore body increases, the bench height increases, and the requirements of the operation organization for "less flying rocks, less spillage, and less disturbance" become stricter, the production site widely uses slag pressing conditions for mining and stripping connection. That is, the next round of blasting is carried out before the previous round of blast piles are completely cleared to control the throwing distance and shorten the cycle. Under this condition, the free surface of the blasting area is insufficient and the resistance line is unstable, which puts higher requirements on the consistency of energy release and spatial effect during the detonation process. However, how to stably create a free surface under slag pressing conditions remains a key technical problem.

[0003] Existing technologies often employ two approaches: one is to differentiate the configuration of hole grid parameters and charge structures, such as reducing charge in the front row, decoupling, increasing plugging length, and adjusting hole spacing to reduce upthrow and induce fracture expansion toward the free surface; the other is to adopt an initiation strategy with slight differences in equal intervals between rows, with the front or back row initiating detonations sequentially to achieve row-by-row pressure relief. However, these approaches typically only provide delay control between rows. The multi-stage charge within the hole is mostly single-stage or low-frequency segmented, and the time difference dispersion of traditional non-electric or fire detonators is large, making it difficult for the front row holes to truly "sound in unison," making it difficult to achieve high-frequency coupling of stress waves within the hole, and the fracture zone often appears discontinuous or offset. Especially in hard rock slag pressing conditions, the energy of the front row is easily "shielded" by the slag pressing and thick resistance lines, resulting in the failure of the free surface to form on schedule and continuously before the back row detonation, resulting in high foundation retaining walls and secondary crushing rates.

[0004] Overall, the bottleneck of slag-pressing conditions lies not in the hole pattern or charge parameters themselves, but in the lack of coordination among timing, space, and energy. Therefore, it is necessary to propose a blasting control method that can achieve efficient energy transfer and pre-form a stable free surface under slag-pressing conditions, ensuring a reliable free surface structure before rear-row detonation. Summary of the Invention

[0005] The present application provides a blasting control method for creating a free surface by blasting the front row holes in the slag pressing blasting zone in advance, so as to solve the problem in the prior art that it is difficult to reliably form a free surface extending along the front row direction before detonating the rear row holes under slag pressing conditions.

[0006] The present application provides a blasting control method for creating a free surface by simultaneously firing the front row holes in the slag pressing blasting zone in advance, comprising: Front and rear row blasthole layout: The front row of holes are laid out along the free surface in the slag pressing area, and the rear row of holes are laid out in the main blasting area. The layout is carried out according to the preset hole spacing, row spacing, hole depth and charging coefficient. The front row holes are set to have the same detonation time, so that the front row holes are detonated earlier than the rear row holes. The same multi-stage charge is carried out in each blast hole of the front row, and the multi-stage detonator detonation can be carried out in the same high-frequency micro-difference detonation mode. Delayed detonation setting for rear row holes: set the detonation time of rear row holes to 10-20ms after the last detonation time of adjacent front row holes; Detonation implementation: Detonation control is carried out using a blasting network composed of digital electronic detonators.

[0007] In an optional embodiment, the hole spacing of the front row holes is 3.2 to 3.8 m, the row spacing is 2.6 to 3.0 m, the hole depth is designed to be ultra-deep 0.3 to 0.7 m, and the charging coefficient is 0.60 to 0.70; the hole spacing of the rear row holes is 2.8 to 3.2 m, the row spacing is 2.3 to 2.7 m, and the charging coefficient is 0.50 to 0.60.

[0008] In an optional embodiment, the hole spacing of the front row holes is 3.5m, the row spacing is 2.8m, the hole depth is designed to be extra deep 0.5m, the charging coefficient is 0.65, the front row holes use linear charging, and the linear charging density is 0.75-0.85kg / m; the hole spacing of the rear row holes is 3.0m, the row spacing is 2.5m, the charging coefficient is 0.55, the rear row holes use coupled charging, the diameter of the medicine roll is 85-95mm and it is arranged close to the hole wall.

[0009] In an optional embodiment, in the setting of early simultaneous detonation of the front row holes, the multi-segment charging in each blast hole of the front row holes is segmented charging, and inert spacer materials are set between each charge segment to isolate adjacent charge segments; the front row holes use a high-frequency micro-difference initiation method to carry out multi-segment detonation with detonators, which must meet the requirement that the detonation time delay time interval τ of adjacent charge segments in each blast hole is 20 to 30 ms.

[0010] In an optional embodiment, each blast hole in the front row of holes adopts a three-stage charging method to realize three-stage detonation of detonators to form a continuous stress wave impact. The detonation time delay time interval τ of adjacent sections in each blast hole in the front row of holes is 25ms. The detonators in the front row of holes detonate each section in sequence from bottom to top, and the delay sequence is 0ms, 25ms and 50ms respectively.

[0011] In an optional embodiment, the delay time Δt between the detonation time of the rear row holes and the last detonation time of the adjacent front row holes is 15ms, so that the initial stress wave generated by the detonation of the rear row holes overlaps with the stress wave generated by the last detonation of the front row holes in time.

[0012] In an optional embodiment, the blasting hole is sealed with clay or bentonite, and the length of the sealing section is 10 to 20 times the hole diameter.

[0013] In an optional embodiment, the method is applicable to hard rock ore bodies with a Pugh hardness coefficient f≥10, preferably granite, diabase and basalt with a Pugh hardness coefficient f=10-12.

[0014] In an optional embodiment, a detonating cord is set 1.6 to 2.3 meters below the mouth of each blasting hole to ensure the stability of explosion transmission; after the detonation is implemented, the detonation of the front row of holes forms a continuous crack zone with a width of 0.8 to 1.2 meters along the front row direction in the slag pressing area, so as to create a free surface for the rear row of holes.

[0015] In an optional embodiment, the detonation time control accuracy of the digital electronic detonator is ≤0.1ms.

[0016] Compared with the prior art, this application has the following beneficial effects: The present application provides a blasting control method for creating a free surface by blasting the front row holes in the slag blasting area in advance. The method first arranges the front row holes in the slag blasting area along the direction of the free surface, and blasts the front row holes in advance and simultaneously before the back row holes are detonated, so that the front row holes release blasting energy in a concentrated manner in a short period of time, forming an artificial free surface connected to the original free surface, solving the problem of large subsequent blasting resistance caused by the lack of free surface in the slag blasting area. Secondly, the present application delays the detonation of the back row holes by 10 to 20 ms after the last detonation moment of the front row holes in terms of detonation sequence, so that the stress wave field formed by the front row holes and the blasting energy of the back row holes are effectively connected in time, realizing the reasonable transfer and superposition of energy, improving the utilization efficiency of the blasting energy, and facilitating the subsequent full fragmentation of the rock mass. Finally, this application uses digital electronic detonators to form a blasting network, and accurately controls the front row holes, rear row holes and multi-stage charging, which can ensure that key time parameters such as early simultaneous sound and delayed detonation meet the design requirements, avoiding stress wave superposition failure caused by timing errors, thereby improving the stability and repeatability of the blasting effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0018] Figure 1A flow chart of a blasting control method for creating a free surface by blasting the front row of holes in the slag pressing blasting zone in advance and simultaneously, provided in one embodiment of the present application; Figure 2 A schematic diagram of an initiation network provided in an embodiment of the present application. DETAILED DESCRIPTION

[0019] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application are clearly and completely described below. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts also fall within the scope of protection of this application.

[0020] First, let’s explain the terms involved in this application: Line charge: refers to a charge with a diameter significantly smaller than the diameter of the borehole. Detonating cord or thin charge is usually arranged along the axis of the borehole, with an air gap or other filler in the middle, and the charge does not contact the borehole wall.

[0021] Coupled charge: refers to the case where the diameter of the charge coil is close to or equal to the diameter of the blasthole, and the charge coil is in direct contact with the hole wall, so that the energy of the explosive is efficiently transferred to the rock mass.

[0022] like Figure 1 As shown, the embodiment of the present application provides a blasting control method for creating a free surface by firing the front row holes in the slag blasting zone in advance, including the following processes: arranging the front and rear rows of blast holes, setting the front row holes to fire in advance and simultaneously, setting the rear row holes to fire with delayed detonation, and implementing the detonation. The specific steps of the blasting control method are as follows: Step S1: Arrange the front row of holes along the free surface in the slag pressing area, and arrange the rear row of holes in the main blasting area according to the preset hole spacing, row spacing, hole depth and charging coefficient; Step S2: setting the same detonation time for each blasthole in the front row to achieve synchronous detonation of the front row blastholes earlier than the rear row blastholes, and performing the same multi-stage charge in each blasthole in the front row and enabling the multi-stage detonation of the detonator to be performed in the same high-frequency micro-difference detonation mode; Step S3, setting the detonation time of the rear row holes to 10 to 20 ms after the last detonation time of the adjacent front row holes; Step S4: using a blasting network composed of digital electronic detonators to perform detonation control.

[0023] In the prior art, the slag-pressing blasting zone often suffers from a lack of effective free surface, which hinders subsequent blasting, poor blasting energy connection between the front and rear rows of holes, and insufficient detonation control precision. To address this, the present application proposes a blasting control method for creating a free surface by simulating the front row of holes in the slag-pressing blasting zone in advance, as described in the above embodiments.

[0024] First, this embodiment arranges the front row of holes in the slag pressing and blasting area along the direction of the free surface, and detonates the front row of holes in advance before the rear row of holes are detonated, so that the front row of holes release the blasting energy in a concentrated manner in a short period of time, forming an artificial free surface connected to the original free surface, thereby solving the problem of large subsequent blasting resistance caused by the lack of free surface in the slag pressing area.

[0025] Secondly, in terms of the detonation sequence, this embodiment delays the detonation of the rear row of holes by 10 to 20 ms after the last detonation moment of the front row of holes, so that the stress wave field formed by the front row of holes and the blasting energy of the rear row of holes are effectively connected in time, realizing the reasonable transfer and superposition of energy, improving the utilization efficiency of the blasting energy, and facilitating the subsequent full fragmentation of the rock mass.

[0026] Finally, this embodiment uses digital electronic detonators to form a blasting network, and accurately controls the front row holes, rear row holes and multi-stage charges, which can ensure that key time parameters such as early simultaneous sound and delayed detonation meet the design requirements, avoid stress wave superposition failure caused by timing errors, and thus improve the stability and repeatability of the blasting effect.

[0027] From the above, it can be seen that the blasting control method for creating a free surface by the early simultaneous sounding of the front row holes in the slag pressing blasting zone provided in the embodiment of the present application can more effectively solve the problem that it is difficult to reliably form a free surface extending along the front row direction before the detonation of the rear row holes under slag pressing conditions in the prior art through the synergistic effect of the early simultaneous sounding of the front row holes to form a free surface, the reasonable delayed connection between the front and rear row holes, and the high-precision detonation control, and can also improve the crushing effect of subsequent blasting and reduce the rate of large blocks.

[0028] In the embodiments of this application, the front row of holes refers to the row of blastholes located closest to the blasting surface (free surface). These are the first holes in the entire blasthole group to interact with the free surface. They are generally located at the leading edge of the blasting zone, with a relatively small resistance line (i.e., the distance between the holes and the free surface). During blasting, the front row of holes primarily forms and expands the free surface, allowing it to extend into the blasting zone and providing a release surface for subsequent rows of holes, thereby reducing rock constraints and improving the crushing effect. In hard rock or slag-pressed conditions, the front row of holes also serves to penetrate the slag and cut through thick resistance lines. The rear row of holes, generally relative to the front row, refers to the rows of blastholes located further back in the hole layout, immediately following the front row of holes.

[0029] In some embodiments, the hole spacing of the front row of holes is 3.2 to 3.8 m, the row spacing is 2.6 to 3.0 m, the hole depth is designed to be ultra-deep 0.3 to 0.7 m, and the charging coefficient is 0.60 to 0.70; the hole spacing of the rear row of holes is 2.8 to 3.2 m, the row spacing is 2.3 to 2.7 m, and the charging coefficient is 0.50 to 0.60.

[0030] In the above embodiment, clear numerical ranges are defined for the hole spacing, row spacing, over-depth value of hole depth, and charging coefficient of the front row holes and the rear row holes. This numerical combination will produce a relatively stable and controllable synergistic effect in implementation: First, the hole spacing and row spacing of the front row holes are slightly larger than those of the rear row holes, and the front row holes are designed with an over-depth of 0.3 to 0.7 meters, which can form a relatively thick free surface footing after blasting, enhance the ability to penetrate the slag, and provide sufficient energy accumulation space for high-frequency multi-stage detonation; second, the higher charging coefficient of the front row holes ( The blast coefficient of the rear row holes is 0.60-0.70, which helps to achieve reliable rock breaking and fracture penetration under the conditions of slag pressure and thick resistance line, while the slightly lower charging coefficient of the rear row holes (0.50-0.60) is conducive to controlling the throwing amount of the rear row and reducing flying rocks and overflow. Finally, the differentiated configuration of the parameters of the front and rear row holes makes the free surface formed by the early simultaneous detonation of the front row holes more spatially complete. When the rear row holes are detonated, energy can be released under the conditions of the already formed free surface, the crushing efficiency is improved and the energy utilization is more concentrated, thereby improving the instability of the free surface formation under slag pressure conditions.

[0031] In the blasting design mentioned in the embodiments of the present application, "super-deep" refers to the part where the actual drilling depth of the blasthole is greater than the theoretical depth corresponding to the designed resistance line, that is, the drilling depth that extends additionally at the bottom of the resistance line, that is, the depth drilled more than the designed step height. The purpose of super-deep is to ensure that the charge at the bottom of the blasthole can fully act on the bottom rock mass, eliminate the bottom angle residue that may be formed after blasting, and improve the integrity of the bottom crushing and free surface formation. In this embodiment, the super-deep value of the front row of holes is controlled at 0.3 to 0.7m, which can not only ensure that there is sufficient bottom energy accumulation for crushing the slag pressing area, but also avoid the reduction of drilling efficiency or energy utilization due to excessive super-depth, thereby achieving stable destruction of the bottom area and row penetration.

[0032] When arranging front-row holes, it's common practice to place one or two rows in the slag pressure area. When thick slag is present, double rows can be used to enhance the stability of the free surface formation. Furthermore, row spacing essentially refers to the center-to-center distance between two rows of blastholes, measuring the distance between the front and rear rows. If there's only one row of front-row holes, the row spacing can be understood as the distance between the front and rear rows.

[0033] As a preferred solution, in some embodiments, the hole spacing of the front row holes is 3.5m, the row spacing is 2.8m, the hole depth is designed to be an extra-deep 0.5m, and the charging coefficient is 0.65. The front row holes use linear charging, and the linear charging density is 0.75-0.85kg / m. Preferably, the linear charging density is 0.85kg / m; the hole spacing of the rear row holes is 3.0m, the row spacing is 2.5m, and the charging coefficient is 0.55. The rear row holes use coupled charging, the diameter of the medicine roll is 85-95mm and is arranged close to the hole wall. Preferably, the diameter of the medicine roll is 90mm.

[0034] In this example, a preferred parameter combination of "front-row linear charge + rear-row coupled charge" is proposed, resulting in a rational energy distribution. The front-row holes are drilled at a 3.5m spacing, a 2.8m row spacing, and a 0.5m over-depth. A charging coefficient of 0.65 is used, along with linear charge and a density of 0.75-0.85 kg / m. This approach reduces the burden on the foundation, decoupling the linear charge from the hole wall, prolonging the gas action time and reducing the crushing zone around the hole. This makes it easier for fractures to open along the free surface and connect between holes, suppressing front-row updraft and reducing the probability of residual foundation. The rear-row holes, however, are drilled at a 3.0m spacing, a 2.5m row spacing, a 0.55 charging coefficient, and coupled charge with a coil diameter of 85-95mm, arranged close to the wall. Given the free surface provided by the front-row holes, this approach helps concentrate energy to crush the bulk of the rock mass. At the same time, because the charge factor is controlled at a moderate level, the blasting-induced throwing and vibration are both within controllable limits. This parameter combination, combined with the front-row hole configuration, allows the front-row holes to focus more on "face opening and pressure relief," while the rear-row holes perform the "primary crushing" task. This enhances the upward continuity of the fracture zone, suppresses the formation of roots and large blocks, and makes the blast pile more conducive to subsequent loading and unloading operations.

[0035] In some embodiments, when setting up simultaneous detonation of the front-row holes, the multi-stage charge in each blasthole of the front row is segmented, with inert spacers placed between each segment to isolate adjacent segments. The high-frequency, micro-difference detonation method for multi-stage detonator detonation in the front row requires that the detonation delay time interval τ between adjacent segments in each blasthole be 20-30 ms. The inert spacers can be PVC tubes, PE tubes, or rubber gaskets. In actual use, it should be noted that the PVC or PE tubes should be short sections with closed ends, or sealed ends should be placed at their ends to avoid forming through-channels that affect the isolation effect. The rubber gaskets must fit tightly against the inner wall of the blasthole and the end face of the charge roll. If necessary, they can be filled with fine sand or bentonite to form a tight seal, effectively blocking the direct propagation of detonation waves and flames between the segments, ensuring the independence and controllability of the segmented charge detonation.

[0036] In this embodiment, a segmented charge, inert spacer material separation, and a 20-30ms delay between adjacent charge segments within the hole are applied to the front row holes to achieve a more stable blasting process. First, the inert spacer material physically separates adjacent charge segments, blocking direct detonation and gas pathways. This prevents the first detonated charge segment from prematurely igniting subsequent segments, thereby dividing the energy release process within the hole into multiple short pulses. This reduces the area of ​​the hole wall crushing zone and makes the coupling between the charge and the hole wall easier to control. Second, the 20-30ms delay between adjacent charge segments ensures that when the subsequent pulse arrives, the microcracks formed by the previous pulse have not yet closed and the local constraints have been reduced. This allows subsequent stress waves and blasting gases to continue to propagate along the existing crack tips, facilitating the formation of fractures within the hole. If the delay is too short, a single large pulse will be formed, resulting in insufficient fracture expansion. If the delay is too long, the effect of the previous pulse will be significantly weakened, requiring the subsequent pulse to re-initiate the fracture, resulting in energy dispersion. Finally, the same segmentation and delay rhythm is used in each hole in the front row to keep the detonation time spectrum consistent within the row, reduce the phase difference between holes, and make the force distribution along the free surface more uniform, thereby improving the continuity of the fracture zone in the row direction and providing a more complete free surface condition for the rear before subsequent blasting, reducing the possibility of root base and large block formation.

[0037] In some embodiments, a three-stage charging method is adopted in each blast hole of the front row of holes to realize the initiation of three-stage detonators to form a continuous stress wave impact. The initiation time delay time interval τ of adjacent charge segments in each blast hole of the front row of holes is 25ms. The detonators in the front row of holes detonate each charge segment in sequence from bottom to top, and the delay sequence is 0ms, 25ms and 50ms respectively.

[0038] In this embodiment, the multi-stage charging of each blast hole in the front row is specifically limited to a three-stage charging method, and the detonation time of adjacent charge segments in the blast hole is delayed at equal intervals of 25 ms. In addition, a bottom-up detonation method (0 / 25 / 50 ms) is adopted. This ensures that the stress waves and blasting gases formed in sequence by each charge segment are connected in an orderly manner in time and advance layer by layer in space, thereby forming a continuous and stable rupture transmission process.

[0039] In the above-mentioned embodiment, a three-stage charge system is used for the front row holes, splitting the energy release within a single hole into three bursts. This reduces the peak value of each burst and prolongs the duration of the burst. After the first pulse is detonated, the initial fractures formed in the hard rock have not yet closed, allowing the two subsequent pulses to continue expanding along the existing fracture tips. Adjacent charge segments are detonated at equal intervals of 25ms. This ensures that when the subsequent pulse arrives, the tension and gas support of the previous pulse are still in their effective stages. This avoids excessive peaks caused by simultaneous peaks with the previous pulse and prevents the need for re-initiation due to excessive delays. The detonation sequence is from bottom to top: the bottom segment prioritizes breaking the floor and forming a lower pressure relief channel. The middle segment then expands the crushing range, and the top segment finally acts near the free surface, which facilitates outward energy diversion and reduces mud ejection. Detonating at equal intervals of 0, 25, and 50ms results in a step-by-step progression of the stress wave and blasting gas, creating continuous drive within a single hole and promoting the interconnection of fractures between holes into bands along the row, thus providing a more stable forward fracture channel for subsequent blasting.

[0040] In some embodiments, the delay time Δt between the detonation time of the rear row holes and the last detonation time of the adjacent front row holes is 15ms, so that the initial stress wave generated by the detonation of the rear row holes overlaps with the stress wave generated by the last detonation of the front row holes in time.

[0041] In this embodiment, the detonation time of the rear row holes is set to be 15ms later than the last section of the adjacent front row holes, so that the stress waves formed by the two rows have a controlled overlap on the time axis. When the rear row holes are detonated, the cracks formed by the last section of the explosion of the front row holes are still in an open state and supported by gas. At this time, the initial stress waves of the rear row holes can quickly extend along the existing crack tips, promoting crack penetration. This delay not only avoids the closure of cracks and energy attenuation caused by too long intervals, but also prevents the complete superposition of wave peaks caused by too short intervals, which leads to local over-breakage or throwing instability. Under slag pressing conditions, this temporal "overlap" helps to weaken the energy shielding brought by the thick resistance line, making it easier for the front and rear rows to form a continuous crack zone in the row direction, thereby improving the timeliness and integrity of the free surface formation, and improving the crushing and throwing conditions of subsequent blasting.

[0042] In some embodiments, the blasting hole is sealed with clay or bentonite, and the length of the sealing section is 10 to 20 times the hole diameter.

[0043] In this embodiment, the blasthole openings are sealed with clay or bentonite, and the length of the sealing section is controlled to 10 to 20 times the hole diameter to enhance the effect of premature simultaneous detonation of the preceding holes. This design of the sealing section length improves gas tightness, prolonging the residence time of explosive gases within the hole, allowing more energy to be transferred along the hole bottom and discharge path, reducing energy dissipation through the hole opening, thereby increasing energy utilization on the free surface and in the slag pressure direction. Furthermore, clay or bentonite exhibits certain plastic deformation and erosion resistance under explosive impact. During the sequential detonation of multiple charge stages, the sealing section can maintain a good sealing effect even after the preceding stage has detonated, suppressing gas leakage until the final stage has detonated. By setting the sealing length range in this embodiment, sufficient resistance is provided to prevent premature pressure release, while not affecting charge placement or construction operations due to excessive length. This synergistic effect of the sealing effect with charge design and detonation sequence promotes stable free surface formation and reduces the risk of free surface discontinuity under slag pressure conditions.

[0044] In some embodiments, the method is applicable to hard rock ore bodies with a Pugh hardness coefficient f≥10, preferably granite, diabase and basalt with a Pugh hardness coefficient f=10-12.

[0045] The method of this embodiment is applicable to hard rock ore bodies with a Proctor hardness coefficient f ≥ 10, preferably granite, diabase, and basalt with f = 10-12, to better match the blasting energy release with the ore body's mechanical properties. Hard rock ore bodies have a dense structure and high compressive strength, and the crack extension rate and range generated by a single blast are limited. Therefore, it is necessary to promptly form a stable free surface through the front row of holes to provide an effective stress release channel for subsequent crushing. Setting a hardness range can avoid excessive energy release or premature collapse of the free surface when the rock is too soft, ensuring a more concentrated and sustained energy effect. For rock types such as granite, diabase, and basalt, which have fast elastic wave propagation speeds and high reflection coefficients, premature synchronization can superimpose multiple stress peaks in the free surface direction in a short period of time, increasing the level of local stress concentration and promoting the penetration of cracks into the free surface. Clarifying the scope of application also helps accurately match blasting parameters during the design phase, reducing fluctuations in results caused by lithology differences, and making free surface formation more controllable and stable.

[0046] In addition, it should be noted that while the method of the embodiment of the present application is preferably applicable to hard rock ore bodies with a Pugh hardness coefficient f ≥ 10, it is not limited to this range. Under medium-hardness and even some soft rock conditions, as long as the blasting parameters are appropriately adjusted (such as hole spacing, row spacing, charge structure, and delay setting), a certain degree of free surface formation and crack penetration effect can also be achieved. Therefore, this method is most suitable for hard rock conditions, but it also has certain feasibility of promotion under other lithologic conditions, providing an alternative blasting control strategy for different ore bodies.

[0047] In some embodiments, a detonating cord is set 1.6 to 2.3 meters below the mouth of each blasting hole to ensure the stability of explosion transmission; after the detonation is implemented, the detonation of the front row of holes forms a continuous crack zone with a width of 0.8 to 1.2 meters along the front row direction in the slag pressing area to create a free surface for the rear row of holes.

[0048] In this embodiment, detonating cords are placed 1.6 to 2.3 meters below the orifice of each blasthole. This positions the detonation path within a relatively stable rock mass, minimizing interference with signal transmission from factors such as looseness, air leaks, or water accumulation near the orifice, thereby improving the reliability of the detonation signal. This ensures that the front-row holes fire synchronously according to the preset timing during detonation, avoiding "duds" or delays caused by signal attenuation or interruption. The fracture zone formed by stable detonation in the front-row holes can reach a width of 0.8 to 1.2 meters along the row in the slag pressure zone and spatially extend between adjacent blastholes, forming a continuous free-surface channel. This channel effectively reduces rock constraints on the free surface during detonation in the rear-row holes, facilitating stress wave propagation toward the free surface and improving the fragmentation efficiency and energy utilization of subsequent blasting. Furthermore, the detonating cord placement matches the hole spacing and depth, helping to align the extension depth of the front-row fracture zone with the rear-row charge position, reducing reverse resistance and improving the uniformity and controllability of the overall blasting. As an optional solution of this embodiment, the detonating cord is set 2 meters below the hole mouth of each blasting hole.

[0049] In some embodiments, the detonation time control accuracy of the digital electronic detonator is ≤0.1ms.

[0050] In this embodiment, the detonation time control accuracy of the digital electronic detonator is limited to ≤0.1ms, ensuring virtually no cumulative error within the preset micro-delays for each blasthole and its multi-stage charge, thus ensuring highly consistent blasting sequences. When multi-stage charges are combined with delays in the front and rear rows of holes, amplified timing errors can easily lead to misaligned stress wave peaks or weakened superposition effects, reducing fragmentation efficiency. High-precision control ensures that stress waves accurately overlap within the designed time window, forming a stable synergistic effect and achieving the ideal rock fracture morphology. This level of accuracy also effectively avoids detonation sequence disruptions or localized premature detonation caused by detonator errors, thereby reducing the risk of adverse effects such as flyrock and vibration. In hard rock conditions, high-precision timing control also helps maintain the stable extension of continuous fractures, ensuring that the free surface formed in the front row of holes is closely aligned with the energy release process in the rear row of holes, thereby improving the controllability and repeatability of the overall blasting effect.

[0051] The following describes a typical implementation of the method of the present application using a blasting operation in a bench slag pressure area of ​​an open-pit mine as an example, combining the on-site conditions of a granite ore body and a Proctor hardness coefficient of approximately 11. This example covers key aspects such as the layout parameters of the front and rear rows of holes, the charging method, and the detonation sequence, aiming to demonstrate how this technical solution can be used to achieve stable and controllable blasting results in an actual construction environment.

[0052] The object of this embodiment is the slag pressing condition of open-pit mine step blasting. The ore body is granite with a Pugh hardness coefficient of about 11. The thickness of the residual slag at the bottom of the slag pressing area is about 2 meters. Under this condition, a stable free surface needs to be created first. In this embodiment, the schematic diagram of the detonation network is as follows: Figure 2 As shown. The front and rear rows of holes are connected in sequence with digital electronic detonators through detonating cords, and combined with the preset delay parameters to form an overall blasting system. The red line segments represent the connection lines within the same delay period, corresponding to the front row holes on the side of the free surface; the gray line segments represent the blasting lines between different delay periods, corresponding to the rear row holes on the side of the slag pressing area. This color differentiation method helps to quickly distinguish the line layout relationship between the front and rear rows of holes on site, avoid wiring errors, and facilitate the inspection and maintenance of the blasting network. Through this blasting network layout, it is possible to take into account both blasting stability and delay accuracy under field conditions, reduce the risks of signal attenuation and transmission interruption, and improve the overall blasting effect. This is further explained below.

[0053] 1. Front row hole arrangement and charge The front row holes are arranged in two rows along the free surface in the slag pressing area. The front row holes are spaced 3.5 meters apart, with a spacing of 2.8 meters between rows. The hole depth exceeds the design elevation by 0.5 meters. The charge coefficient is controlled at 0.65, and the linear charge density is 0.8 kg / m. The front row holes use a three-stage charge, separated by inert spacers. Three electronic detonators are placed in each hole, with adjacent charge stages detonated sequentially from the bottom of the hole toward the orifice with a delay of 25 milliseconds, followed by detonation in the order of 0 milliseconds, 25 milliseconds, and 50 milliseconds. To ensure stable detonation transmission, a detonating cord is placed 2.0 meters below the orifice of each front row hole. The orifice is sealed with clay or bentonite, with the length of the sealing section being 15 times the hole diameter. During detonation, the two rows of front row holes are detonated synchronously, meaning all front row holes initiate a micro-difference detonation at the same time.

[0054] 2. Relationship between rear hole arrangement and detonation The rear row of holes is located in the main blasting area and is arranged in three rows. The rear row holes are spaced 3.0 meters apart and 2.5 meters apart. No over-depth is permitted. The charge coefficient is 0.55, using a coupled charge structure and wall-mounted charge rolls with a 90mm diameter. The detonation time of the rear row holes is delayed by 15 milliseconds relative to the last detonation of the adjacent front row holes. This allows the initial stress wave from the rear row holes to enter the crack tips already formed in the front row holes, achieving effective temporal connection. Digital electronic detonators are used throughout the network for detonation control, with a time control accuracy of no more than 0.1 millisecond.

[0055] 3. Construction and Effect After completing drilling, hole cleaning, charge placement, segmentation, and plugging according to the aforementioned parameters, and completing the connection of the detonating cord and detonator and circuit testing, detonation was carried out. Detonation results showed that the front row of holes formed a continuous fracture zone approximately 0.8 to 1.2 meters wide along the row in the slag pressure area, with a free surface appearing and advancing outward in a timely manner. The rear row of holes released energy under the boundary conditions of this free surface, resulting in uniform rock fragmentation and no visible foundation retaining wall. The casting direction was controlled, and both flyrock and vibration were within acceptable limits, ensuring smooth operation.

[0056] In field trials in a bench slag-pressing area of ​​an open-pit mine, the hole layout and blasting method of this embodiment achieved significant results under conditions with a rock hardness coefficient of f=11. Compared with traditional methods, the unit energy consumption was reduced from 0.71kg / m³ to 0.43kg / m³, the large-piece rate was reduced from 21% to 4.5%, and the cost of a single blasting operation was saved by approximately 18,000 yuan (including explosives, labor, and equipment losses). This fully demonstrates the comprehensive advantages of this embodiment in terms of energy utilization, particle size control, explosives economy, and overall operating cost control.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A blasting control method for creating a free surface by simultaneously firing the front row holes in the slag blasting zone in advance, characterized in that: include: Front and rear row blasthole layout: The front row of holes are laid out along the free surface in the slag pressing area, and the rear row of holes are laid out in the main blasting area. The layout is carried out according to the preset hole spacing, row spacing, hole depth and charging coefficient. The front row holes are set to have the same detonation time, so that the front row holes are detonated earlier than the rear row holes. The same multi-stage charge is carried out in each blast hole of the front row, and the multi-stage detonator detonation can be carried out in the same high-frequency micro-difference detonation mode. Delayed detonation setting for rear row holes: set the detonation time of rear row holes to 10-20ms after the last detonation time of adjacent front row holes; Detonation implementation: Detonation control is carried out using a blasting network composed of digital electronic detonators.

2. The blasting control method for creating a free surface by simultaneously firing the front row holes in the slag pressing blasting area in advance according to claim 1 is characterized in that: The hole spacing of the front row holes is 3.2-3.8m, the row spacing is 2.6-3.0m, the hole depth is designed to be extra deep 0.3-0.7m, and the charging coefficient is 0.60-0.70; the hole spacing of the rear row holes is 2.8-3.2m, the row spacing is 2.3-2.7m, and the charging coefficient is 0.50-0.

60.

3. The blasting control method for creating a free surface by simultaneously firing the front row holes in the slag pressing blasting zone in advance according to claim 2 is characterized in that: The hole spacing of the front row holes is 3.5m, the row spacing is 2.8m, the hole depth is designed to be extra deep 0.5m, the charging coefficient is 0.65, the front row holes use linear charging, and the linear charging density is 0.75-0.85kg / m; the hole spacing of the rear row holes is 3.0m, the row spacing is 2.5m, the charging coefficient is 0.55, the rear row holes use coupled charging, the diameter of the medicine roll is 85-95mm and it is arranged close to the hole wall.

4. The blasting control method for creating a free surface by simultaneously firing the front row holes in the slag pressing blasting zone in advance according to claim 1 is characterized in that: In the setting of early simultaneous detonation of the front row holes, the multi-segment charging in each blast hole of the front row holes is segmented charging, and inert spacer materials are set between each charge segment to isolate the adjacent charge segments; the multi-segment detonation of the front row holes using high-frequency micro-difference initiation method requires that the detonation time delay time interval τ of the adjacent charge segments in each blast hole be 20 to 30ms.

5. The blasting control method for creating a free surface by simultaneously firing the front row holes in the slag pressing blasting zone in advance according to claim 4 is characterized in that: Each blast hole in the front row of holes adopts a three-stage charging method to realize the initiation of three-stage detonators to form a continuous stress wave impact. The initiation time delay time interval τ of adjacent charge segments in each blast hole in the front row of holes is 25ms. The detonators in the front row holes detonate each charge segment in sequence from bottom to top, and the delay sequence is 0ms, 25ms and 50ms respectively.

6. The blasting control method for creating a free surface by simultaneously firing the front row holes in the slag pressing blasting zone in advance according to claim 4 or 5, characterized in that: The delay time Δt between the detonation time of the rear row holes and the last detonation time of the adjacent front row holes is 15ms, so that the initial stress wave generated by the detonation of the rear row holes overlaps with the stress wave generated by the last detonation of the front row holes in time.

7. The blasting control method for creating a free surface by simultaneously firing the front row holes in the slag pressing blasting zone in advance according to claim 1 is characterized in that: The blasting holes are sealed with clay or bentonite, and the length of the sealing section is 10 to 20 times the hole diameter.

8. The blasting control method for creating a free surface by simultaneously firing the front row holes in the slag pressing blasting zone in advance according to claim 1 is characterized in that: The method is applicable to hard rock ore bodies with a Pusch hardness coefficient f≥10, preferably granite, diabase and basalt with a Pusch hardness coefficient f=10-12.

9. The blasting control method for creating a free surface by simultaneously firing the front row holes in the slag pressing blasting area in advance according to claim 1 is characterized in that: A detonating cord is set 1.6 to 2.3 meters below the mouth of each blasting hole to ensure the stability of explosion transmission; after the detonation is implemented, the detonation of the front row of holes forms a continuous crack zone with a width of 0.8 to 1.2 meters along the front row direction in the slag pressing area, creating a free surface for the rear row of holes.

10. The blasting control method for creating a free surface by simultaneously firing the front row holes in the slag pressing blasting zone in advance according to claim 1 is characterized in that: The detonation time control accuracy of the digital electronic detonator is ≤0.1ms.

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