Step merging presplitting blast hole structure and blasting method

Abstract

The invention discloses a step merging pre-splitting blast hole structure and a blasting method. The step merging pre-splitting blast hole structure comprises a pre-splitting hole, a buffer hole and a main blast hole. The presplitting holes are arranged in a row on the designed boundary slope line of the upper step and are obliquely deepened to and below the bottom of the lower step in the downward front direction, and the perforation angle of the presplitting holes is the designed angle of the slope after blasting; the pre-splitting hole is an upper step pre-splitting hole at the upper step part, the pre-splitting hole is a lower step pre-splitting hole at the lower step part, and the non-coupling coefficient of the upper step pre-splitting hole is smaller than that of the lower step pre-splitting hole; the buffering hole is formed in front of the pre-splitting hole, and the main blast hole is formed in front of the buffering hole. The method is simple in process technology, convenient to operate and construct, high in perforating efficiency, good in presplitting effect, low in slope treatment investment, capable of effectively improving the stability of the merged slope and avoiding slope instability and collapse, and especially suitable for one-time forming blasting of the merged slope in surface mining.

Description

Technical Field

[0001] This invention relates to a mining blasting technology, and more particularly to a pre-splitting blast hole structure and blasting method with stepped merging. Background Technology

[0002] my country boasts abundant mineral resources, and open-pit mining, with its advantages of high efficiency and low cost, has become the mainstream method of mining. Blasting, as a crucial step, directly impacts mining costs and efficiency. Traditional blasting often results in excessive fragmentation, flyrock, and low operational efficiency, increasing subsequent processing costs and potentially posing safety hazards. Pre-splitting blasting technology, as an advanced controlled blasting method, effectively controls the blasting range and vibration by creating pre-cracks before the main blasting zone, reducing damage to the surrounding rock mass. Exploring the application of pre-splitting blasting technology in mining is of great significance for improving blasting quality, reducing costs, and ensuring safe production.

[0003] Under current technical conditions, if pre-splitting blasting is carried out on the upper production step, it will be difficult to carry out pre-splitting blasting and drilling operations on the lower production step. At the same time, a protruding wall will appear at the junction of the upper and lower production steps. In order to achieve the designed slope angle, the slope angle of the lower step will inevitably be larger than the designed slope angle, which will affect the stability of the overall merged slope and make it very easy for the slope to become unstable and collapse, thus posing a hidden danger to safe production. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a pre-splitting blast hole structure with good slope stability through step merging; the present invention also provides a pre-splitting blasting method for step merging.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the pre-splitting blast hole structure of the present invention is as follows: it includes pre-splitting holes, buffer holes, and main blast holes; the pre-splitting holes are arranged in a row along the boundary slope line of the upper step design, extending obliquely downwards and forwards to the bottom and below of the lower step, and the perforation angle of the pre-splitting holes is the design angle of the slope after blasting; the pre-splitting holes located in the upper step are called upper step pre-splitting holes, and the pre-splitting holes located in the lower step are called lower step pre-splitting holes, and the decoupling coefficient of the upper step pre-splitting holes should be less than that of the lower step pre-splitting holes; the buffer holes are arranged in front of the pre-splitting holes, and the main blast holes are arranged in front of the buffer holes.

[0006] Furthermore, the decoupling coefficient of the pre-cracked hole in the upper step is 0.6 to 0.7 times that of the pre-cracked hole in the lower step.

[0007] Furthermore, the buffer holes are arranged in two rows, and the main gun holes are arranged in at least three rows.

[0008] Furthermore, the perforation angle of the first row of buffer holes near the front is 78° to 85°, and the perforation angle of the second row of buffer holes at the rear is 64° to 75°.

[0009] Furthermore, the last row of main gun holes does not extend too deep into the upper step, while the main gun holes of the remaining rows extend into the lower step.

[0010] Furthermore, the diameter of the pre-splitting hole is 0.55 to 0.65 times the diameter of the main blast hole.

[0011] Furthermore, the charging sections of the upper step pre-splitting hole, from top to bottom, are the upper step pre-splitting hole weakening section, the upper step pre-splitting hole normal section, and the upper step pre-splitting hole strengthening section, with the detonator connected in the forward direction to the latex explosive in the upper step pre-splitting hole strengthening section; the charging sections of the lower step pre-splitting hole, from top to bottom, are the lower step pre-splitting hole upper strengthening section, the lower step pre-splitting hole normal section, and the lower step pre-splitting hole lower strengthening section, with the detonator connected in the forward direction to the latex explosive in the lower step pre-splitting hole upper strengthening section; the latex explosives in the upper and lower step pre-splitting holes are connected in series via detonating cord.

[0012] Furthermore, the charge length of the normal section of the upper step pre-crack hole is 70% to 80% of the total charge length of the upper step pre-crack hole; the charge per unit length of the reinforced section of the upper step pre-crack hole is 2 to 4 times the charge per unit length of the normal section of the upper step pre-crack hole; and the charge per unit length of the weakened section of the upper step pre-crack hole is 0.45 to 0.55 times the charge per unit length of the normal section of the upper step pre-crack hole. The charge length of the normal section of the lower step pre-crack hole is 76% to 82% of the total charge length of the lower step pre-crack hole; and the charge per unit length of the upper reinforced section and the lower reinforced section of the lower step pre-crack hole is 2 to 4 times the charge per unit length of the normal section of the lower step pre-crack hole.

[0013] Furthermore, the upper step pre-splitting hole is equipped with a spacer at a distance of 3 to 4.5 m from the hole opening, and the upper part of the spacer is filled as a filling section.

[0014] To solve the above-mentioned technical problems, the pre-splitting blasting method of the present invention adopts the above-mentioned pre-splitting blast hole structure. The technical solution adopted is as follows: the upper step pre-splitting hole and the lower step pre-splitting hole are detonated simultaneously with a 0ms delay; the main blast hole is detonated hole by hole using isochronous lines, and the buffer hole is detonated hole by hole using isochronous lines.

[0015] The beneficial effects of adopting the above technical solution are as follows: This invention achieves one-time forming of two merged slopes by drilling pre-splitting holes to two merging steps in a single operation, while simultaneously adjusting the decoupling coefficients of the pre-splitting holes in the upper and lower steps, as well as the pre-splitting hole charging structure. Furthermore, the main blasting holes are also drilled to the lower step, reducing the difficulty of drilling subsequent main blasting holes and pre-splitting holes in the lower step and reducing the dangers of subsequent blasting operations. This results in a smoother wall surface at the junction of the upper and lower steps after blasting, preventing the lower step from having an excessively large angle after reaching the boundary, which could affect the overall stability of the merged steep slope. After implementation, this invention strengthens the slope's stability, reduces the increased slope maintenance costs due to slope instability, reduces the harm to drilling and blasting personnel from loose rocks on the slope, and also reduces the cost of slope fissures, GNSS, anchor cable force gauges, and anchor bolt stress gauges.

[0016] This invention, by modifying the charging structure of the pre-splitting hole, ensures a smooth wall surface after pre-splitting blasting, solving the problem of unevenness at the junction of the upper and lower steps caused by separate pre-splitting blasting of the upper and lower steps, thus improving the slope boundary approach progress. Furthermore, this invention features simple technology, convenient operation and construction, and high drilling efficiency. It offers excellent pre-splitting effect, low investment in slope treatment, and significant cost savings, effectively addressing the issue of boundary pre-splitting blasting affecting production progress. This invention effectively improves the stability of merged slopes, preventing slope instability and collapse, and significantly increases down-the-hole drilling efficiency while reducing production costs. It is particularly suitable for one-time forming blasting of merged slopes in open-pit mines. Attached Figure Description

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0018] Figure 1 This is a schematic diagram of the pre-splitting blasting planar arrangement described in this invention; Figure 2 This is a schematic diagram of the cross-section of the pre-splitting blasting borehole described in this invention.

[0019] In the diagram: 11 main gun holes in the first row, 12 main gun holes in the second row, 13 main gun holes in the third row, 21 buffer holes in the first row, 22 buffer holes in the second row, 3 pre-crack holes, 31 pre-crack holes in the upper step, 311 weakened section of the pre-crack holes in the upper step, 312 normal section of the pre-crack holes in the upper step, 313 reinforced section of the pre-crack holes in the upper step, 32 pre-crack holes in the lower step, 321 upper reinforced section of the pre-crack holes in the lower step, 322 normal section of the pre-crack holes in the lower step, 323 lower reinforced section of the pre-crack holes in the lower step, 4 free surface, 51 upper step, 52 lower step, angle a1 of the first row of buffer holes, angle a2 of the second row of buffer holes. Detailed Implementation

[0020] Figure 1 , 2As shown, in this paper, the free surface 4 is in front and the boundary slope line is behind. The blast holes are arranged in a row on the steps in front of the boundary slope line.

[0021] Figure 1 , 2 As shown, the pre-splitting blast hole structure of this step includes pre-splitting holes 3, buffer holes, and main blast holes. The buffer holes are arranged in front of the pre-splitting holes 3, and the main blast holes are arranged in front of the buffer holes. The pre-splitting holes 3 are arranged in a row along the boundary slope line of the upper step 51, extending diagonally downwards and forwards to the bottom of the lower step 52 or through the bottom of the lower step 52. The pre-splitting holes 3 have an over-depth of 0-0.5m, meaning that the depth of the pre-splitting holes 3 through the bottom of the lower step 52 does not exceed 0.5m. The perforation angle of the pre-splitting holes 3 is the design angle of the slope after blasting, which is determined according to the mining slope stripping plan. The pre-cracked holes 3 are designated as upper step pre-cracked holes 31 for the portion located on the upper step 51 and lower step pre-cracked holes 32 for the portion located on the lower step 52. The decoupling coefficient of the upper step pre-cracked holes 31 should be less than that of the lower step pre-cracked holes 32. Preferably, the decoupling coefficient of the upper step pre-cracked holes 31 is 0.6 to 0.7 times that of the lower step pre-cracked holes 32. The diameter of the pre-cracked holes 3 is D. Y =0.55D Z ~0.65D Z Hole spacing J Y =16D Y ~24D Y , where D Y The diameter of pre-cracked hole 3, D Z The diameter of the main borehole, J Y The spacing between the pre-splitting holes 3; the borehole depth L of the upper stepped pre-splitting holes 31. Y上 =H 上 / sina, the borehole depth L of the pre-splitting hole 32 in the lower step Y下 ≥H 下 / sina, where L Y上 The borehole depth and H of the pre-splitting hole 31 in the upper step 上 Where is the height of the upper step, 'a' is the perforation angle of the pre-splitting hole 3, and 'L' is the height of the upper step. Y下 The borehole depth and H of the pre-splitting hole 32 in the lower step 下 This refers to the height of the lower step.

[0022] Figure 1 , 2As shown, in this stepped pre-splitting borehole structure, the buffer holes are perforated obliquely downwards and forwards; preferably, two rows are arranged, with the first row of buffer holes 21 near the front having a perforation angle of 78°~85°, i.e., the first row of buffer holes angle a1=78°~85°, and the second row of buffer holes 22 behind having a perforation angle of 64°~75°, i.e., the second row of buffer holes angle a2=64°~75°. The diameter of the buffer holes is 140~165mm, preferably the same as the diameter of the main borehole; the spacing J of the buffer holes... H =10D2~30D2; the spacing between the buffer holes =J H / m, the spacing between the buffer hole and the main gun hole = J Z / m, the spacing between the buffer hole and the pre-cracked hole 3 = J Y / m, where J Z J H and J Y The spacing between the main blast holes, buffer holes, and pre-splitting holes 3 are respectively. m is the designed blast hole density coefficient, m = hole spacing / row spacing, which is generally taken as 0.8 to 1.4.

[0023] Figure 1 , 2 As shown, the pre-splitting blast hole structure of this stepped merging features main blast holes that drill vertically downwards. At least three rows are arranged, with the last row of main blast holes having no excessive depth on the upper step 51; that is, the bottom of the main blast holes in this row extends at most to the bottom of the upper step 51. The remaining rows of main blast holes are designed to be excessively deep on the upper step 51, extending into the lower step 52. This design provides service for both the upper and lower merged steps. The diameter D of the main blast hole is... Z The main borehole spacing J is 140–165 mm. Z =10D Z ~30D Z The spacing between main gun holes = J Z / m, where m is the designed borehole density coefficient, m = hole spacing / row spacing, generally taken as 0.8 to 1.4.

[0024] Figure 1 , 2 As shown, the pre-splitting borehole structure of this step is filled with explosives in the main borehole, buffer hole and pre-splitting hole.

[0025] The charging structure within the pre-splitting hole 3 is as follows: the charging sections of the upper stepped pre-splitting hole 31, from top to bottom, are the upper stepped pre-splitting hole weakening section 311, the upper stepped pre-splitting hole normal section 312, and the upper stepped pre-splitting hole strengthening section 313; latex explosive is filled in the charging sections, and the digital electronic detonator is positively connected to the latex explosive in the upper stepped pre-splitting hole strengthening section 313. The charging sections of the lower stepped pre-splitting hole 32, from top to bottom, are the lower stepped pre-splitting hole upper strengthening section 321, the lower stepped pre-splitting hole normal section 322, and the lower stepped pre-splitting hole lower strengthening section 323; latex explosive is filled in the charging sections, and the digital electronic detonator is positively connected to the latex explosive in the lower stepped pre-splitting hole upper strengthening section 321. The explosives filled in the upper step pre-splitting hole 31 and the lower step pre-splitting hole 32 are fixed on long strips of bamboo or wood. The fixing method can be to wrap the bamboo or wood strips with straps / PVC tape. Two sections of detonating cord are laid on the bamboo strips to connect the explosives in series, so as to ensure that the latex explosives in the upper step pre-splitting hole 31 and the lower step pre-splitting hole 32 can be detonated simultaneously through the detonating cord.

[0026] The charge length of the normal section 312 of the upper step pre-cracked hole is 70% to 80% of the total charge length of the upper step pre-cracked hole 31, and the charge length of the weakened section 311 and the reinforced section 313 of the upper step pre-cracked hole are 20% to 30% of the total charge length. The total charge length L of the upper step pre-cracked hole 31 is... 上药 =Q 上预 / q 上线 The charge amount of the pre-cracked hole in the upper step, in the normal section 312, is Q. 上正 =q 上线 ×L 上正药 The charge per unit length of the reinforced section 313 of the upper stepped pre-cracked hole is 2 to 4 times the charge per unit length of the normal section 312 of the upper stepped pre-cracked hole, i.e., Q 上加 =2×q 上线 ×L 上加药 ~4×q 上线 ×L 上加药 The charge per unit length of the weakened section 311 of the upper stepped pre-cracked hole is 0.45 to 0.55 times the charge per unit length of the normal section 312 of the upper stepped pre-cracked hole, i.e., Q 上减 =0.5×q 上线 ×L 上减药 ~0.55×q 上线 ×L 上减药 ; among which, L 上药 The total length of the charge in the pre-splitting hole 31 of the upper step is in meters (m); q 上线 Q represents the linear charge density of the pre-splitting hole 31 in the upper step, i.e., the explosive consumption per unit volume, in g / m³. 上预 The pre-charge amount of explosive for the pre-splitting hole 31 in the upper step is kg; Q 上正The charge amount for the normal section 312 of the pre-scraped hole in the upper step is expressed in kg and L. 上正药 Q is the charge length of the normal section 312 of the pre-cracked hole in the upper step, in meters. 上加 The charge amount for the pre-cracked hole reinforcement section 313 in the upper step is kg; L 上加药 Q is the charge length of the pre-cracked hole reinforcement section 313 in the upper step, in meters. 上减 The charge amount for the weakened section 311 of the pre-cracked hole in the upper step is kg; L 上减药 The charge length of the weakening section 311 of the pre-splitting hole in the upper step is in meters (m). The plugging length of the pre-splitting hole is 1 to 1.5 times the diameter of the pre-splitting hole 3, i.e., L. 堵 =1D Y ~1.5D Y , where L 堵 D is the plugging length of the pre-cracked hole. Y The diameter of the pre-cracked hole 3 is specified; the upper stepped pre-cracked hole 31 is equipped with a spacer at a distance of 3 to 4.5 m from the hole opening, and the upper part of the spacer is filled with a filling section, which is filled with a filling material.

[0027] The charge length of the normal section 322 of the lower step pre-cracked hole is 76% to 82% of the total charge length of the lower step pre-cracked hole 32, and the charge length of the upper reinforcing section 321 and the lower reinforcing section 323 of the lower step pre-cracked hole is 18% to 24% of the total charge length of the lower step pre-cracked hole 32. The total charge length L of the lower step pre-cracked hole 32 is... 下药 =Q Y下 / q 下线 The charge amount of the pre-cracked hole in the lower step, in the normal section 322, is Q. 下正 =q 下线 ×L 下正药 The charge per unit length of the upper reinforcing section 321 and the lower reinforcing section 323 of the lower step pre-crack hole are 2 to 4 times the charge per unit length of the normal section 322 of the lower step pre-crack hole, i.e., Q 下加 =2×q 下线 ×L 下加药 ~4×q 下线 ×L 下加药 ; among which, L 下药 The total length of the charge in the pre-splitting hole 32 of the lower step is in meters (m); q 下线 Q represents the linear charge density of the pre-splitting hole 32 in the lower step, i.e., the explosive consumption per unit volume, in g / m³. Y下 The pre-charge amount of explosive for the pre-splitting hole 32 in the lower step is kg; Q 下正 The charge amount for the normal section 322 of the pre-scraped hole in the lower step is expressed in kg and L. 下正药 Q is the charge length (m) of the normal section 322 of the pre-scraped hole in the lower step; 下加The charge amount (kg; L) is the charge amount of the upper reinforcing section 321 of the pre-splitting hole in the lower step or the lower reinforcing section 323 of the pre-splitting hole in the lower step. 下加药 The charge length is in meters (m) for either the upper reinforcing section 321 of the pre-splitting hole in the lower step or the lower reinforcing section 323 of the pre-splitting hole in the lower step.

[0028] The main borehole and buffer borehole are filled with porous granular ammonium nitrate explosive (ANFO), with an ANFO density of 0.83–0.87 g / cm³. 3 The charge Q of the main gun bore Z =qa 孔 b 排 L, the amount of explosive in the buffer hole Q H =qa 孔 b 排 L, the filling height h of the main borehole and buffer borehole is (30~40)D, and the borehole density coefficient m is generally taken as 0.8~1.4, m=a 孔 / b 排 ; where Q Z The charge amount for the main borehole, in kg; Q H The charge amount in the buffer hole, kg; h is the filling height of the main borehole or buffer hole, m; D is the diameter of the main borehole or buffer hole, mm; m is the designed borehole density coefficient; a 孔 The hole spacing is in meters (m); b 排 q is the row spacing, in meters; q is the charge density, i.e., the explosive consumption per unit volume, in grams per cubic centimeter. 3 L represents the length of the charge, in meters (m).

[0029] Figure 1 , 2 As shown, the pre-splitting blasting method for this step merging is as follows: the main blast holes are detonated using digital electronic detonators and latex explosives. Both the main blast holes and buffer holes are detonated sequentially using isochronous detonation; the first detonation hole in the first row of the main blast holes is detonated with a delay of 100ms, the interval between main blast holes in the same row is 42ms, and the interval between rows is 100ms; the pre-splitting holes are detonated with an instantaneous detonation delay of 0ms, and the pre-splitting holes 31 in the upper step and 32 in the lower step are detonated simultaneously with a delay of 0ms.

[0030] By adopting the above-mentioned pre-splitting blasting method, the risk of difficulty in drilling pre-splitting holes in the lower step is eliminated by drilling pre-splitting holes to both the upper and lower steps in one go. At the same time, it solves the problem that the lower step's final boundary slope angle is too large due to the need to ensure construction close to the design boundary line, which affects the overall stability of the merged slope. The pre-splitting surfaces of the upper and lower steps are formed in one go, and there will be no protrusion at the junction of the upper and lower pre-splitting surfaces, which would affect the aesthetics of the slope. By drilling the main blast hole to the lower step, the lower step does not need to drill pre-splitting holes and buffer holes, and full-depth blast holes can be drilled directly, which improves the boundary line of the lower step and the production progress.

[0031] Example: The following is an illustration of the blasting of the slope near the boundary of the Sijiaying mining area.

[0032] Figure 1 As shown, based on the actual mining production, the bench height is determined to be 15m, and the combined bench height is 30m. A φ90 type down-the-hole drill, commonly used in mining, is selected to drill pre-splitting holes. A φ150 type down-the-hole drill is selected to drill buffer holes and main blast holes. The relevant parameters are determined as follows: 1. Determination of pre-splitting borehole parameters: 1) Determine the depth LY of the pre-splitting hole 3: Based on actual field application experience, the step height H is determined. 并 =L Y sina, where: H 并 =30m, drilling angle a=65°, pre-splitting hole depth L Y =33.1m, L is taken in this design. Y =33.5m; Pre-cracked hole diameter D Y =(0.55~0.65)D Z D Z It refers to the main gun bore diameter, which is generally taken as 140-165mm, then D Y =77~107.25mm, D is taken in this design. Y =90mm; Pre-cracked hole plugging length L 堵 =(1~1.5)D Y =0.9~1.35mm, the charge height is 4.5m without specifying the charge height in this design, with the spacer lowered to 3m and the remaining 3m filled with packing material; the pre-splitting hole spacing J Y =(16~24)D Y The approximate length is 1.44 to 2.16 meters, but we use 1.5 meters for this design.

[0033] 2) Determine the decoupling coefficient M: Decoupling coefficient M = D Y / D 药 In this design, the diameter D of the pre-splitting hole 31 in the upper step is [missing information]. 上药 Take a φ32mm diameter, lower step pre-splitting hole 32, charge cartridge diameter D 下药 With a diameter of φ50mm and a pre-splitting hole diameter of 90mm, the decoupling coefficient M of the pre-splitting hole 31 in the upper step is [missing information]. 上 Take 2.8, and the decoupling coefficient M of the pre-cracked hole 32 in the lower step. 下 Take 1.8.

[0034] 3) Determine the density q of the linear charge. 线The linear charge density for pre-splitting holes in this design is divided into two parts. According to the "Detailed Explanation of Construction Methods for Smooth Blasting and Pre-splitting Blasting in Open-Pit Mines," the linear charge density for pre-splitting blasting is generally 200–500 g / m. Based on the specification, the linear charge density q for the upper bench pre-splitting hole 31 is... 上线 The charge density is set at 400-500 g / m. Since the lower bench lacks an exposed free surface, the pre-splitting hole 32 is subject to significant clamping effect from the ore-bearing rock mass. Therefore, the linear charge density of the pre-splitting hole 32 in the lower bench is approximately twice the standard value, i.e., q. 下线 Take 750-800 g / m.

[0035] Due to Q Y上 =q 上线 L 上药 The charge Q in the pre-splitting hole 31 of the upper step was... Y上 =5.4kg; the specific calculation is as follows: the charge density q of the pre-splitting hole 31 in the upper step. 上线 =400~500g / m, 400g / m is used in this case; the charging length L of the pre-splitting hole 31 in the upper step. 上药 =12m. The normal section of the pre-splitting hole in the upper step is filled with 312 latex explosive Q. 上正 =q 上线 L 上正药 =400×9=3.6kg, normal segment L 上正药 Take 9m; the upper step pre-cracked hole reinforced section 313 latex explosive Q 上加 =(2~4)×q 上线 L 上加药 =2×400×2=1.6kg, reinforced section L 上加药 Take 2m, this time take twice q 上线 The upper step pre-cracked hole weakening section of the 311 latex explosive Q 上减 = (0.45~0.55)×q 上线 L 上减药 =0.5×400×1=0.2kg, weakening segment L 上减药 Take 1m, and this time take 0.5 times q. 上线 Q Y上 =Q 上正 +Q 上加 +Q 上减 =3.6+1.6+0.2=5.4kg.

[0036] Due to Q Y下 =q 下线 L 下药 Among them: the charge Q of the 32 pre-splitting holes in the lower step. Y下 =14kg; the specific calculation is as follows: the charge density q of the 32-line wire in the pre-splitting hole of the lower step. 下线=750~800g / m, 750g / m is selected in this case; the charging length L of the pre-splitting hole 32 in the lower step is... 下药 =17m. The lower stepped pre-splitting hole normal section contains 322 latex explosive Q. 下正 =q 下线 L 下正药 =700×14=9.8kg, normal segment L 下正药 Take 14m; the upper reinforcing section of the pre-splitting hole in the lower step is made of 321 latex explosive Q. 下加1 =(2~4)×q 下线 L 下加药 =2×700×1=1.4kg, reinforced section L 下加药 Take 1m, this time take 2 times q 下线 The lower step pre-cracked hole lower reinforcing section of the 323 latex explosive Q 下加2 =(2~4)×q 下线 L 下减药 =2×700×2=2.8kg, reinforced section L 下加药 Take 2m; Q Y下 =Q 下正 +Q 下加1 +Q 下加2 =9.8+1.4+2.8=14kg.

[0037] 2. Determination of buffer borehole parameters: 1) Determine the charge density Δ in the buffer orifice H Based on the actual production of porous granular ammonium nitrate explosives in mining and chemical plants, the packing density △ inside the buffer holes H It ranges from 0.83 to 0.87 g / cm³. 3 The design used 0.83 g / cm³. 3 .

[0038] 2) Determine the drilling angle α of the buffer hole: Based on the drawing and actual measurement, in order to ensure that the buffer hole does not damage other blast holes, a distance of not less than 1m should be left between it and other blast holes. Therefore, the measured depth L of the second row of buffer holes 22 near the pre-splitting hole 3 is as follows. H2 The borehole diameter is 5-7m, but 6m is used in this design; the perforation angle is 64°-75°, but 70° is used in this design; the first row of buffer holes near the main gun hole has a depth of L. H1 The standard borehole diameter is 9–11m, but this design uses 10m; the perforation angle is 78°–85°, but this design uses 80°; the explosive consumption is 0.45–0.6 kg / m. 3 The explosive consumption q for this test is taken as 0.45 kg / m³. 3 .

[0039] 3) Determine the diameter D of the buffer orifice. H : Buffer hole diameter D HThe borehole diameter is typically 140–165 mm, but this design uses 150 mm. The borehole density coefficient m = 0.8–1.4, but in this design m is set to 1, m = a H / b H Hole spacing a H Take 4m, row spacing b H Take 4m.

[0040] 3. Determination of main borehole parameters: 1) Determine the charge density △ in the main gun port Z Based on the actual production of porous granular ammonium nitrate explosives in mining and chemical plants, the packing density △ inside the buffer holes Z It ranges from 0.83 to 0.87 g / cm³. 3 The design used 0.87 g / cm³. 3 .

[0041] 2) Determine the drilling depth L of the main gun borehole Z The main gun holes are arranged in three rows. Based on the drawings and actual measurements, to ensure the main gun holes do not damage the pre-splitting holes, a distance of no less than 1 meter should be maintained between them. Therefore, the measured depth L of the third row of main gun holes (13 holes) closest to the buffer hole is... Z3 ≤15m, the depth L of the second row of main gun holes 12 in the middle Z2 The hole depth L of the first row of main gun holes 11 near the free surface 4 is ≤22m. Z1 ≤27m; all main blast holes are vertically drilled; explosive consumption is 0.45~0.6kg / m 3 The explosive consumption q for this test is taken as 0.6 kg / m³. 3 .

[0042] 3) Determine the main gun bore diameter D Z Main gun aperture D Z The borehole diameter is typically 140–165 mm, but this design uses 150 mm. The borehole density coefficient m = 0.8–1.4, but in this design m is set to 1, m = a Z / b Z Take the hole spacing a respectively. Z =4m, row spacing b Z =4m.

[0043] 4. On-site blasting operation: The blasting experiment was conducted at the -157m level of the West Slope. During normal production, drilling should proceed directly to the -172m level, followed by drilling to the -187m level, ultimately forming a merged step near the boundary slope from -157m to -187m. The experiment included one row of 12 pre-splitting holes; two rows of buffer holes, with 5 holes in the second row (22) closest to the pre-splitting holes and 6 holes in the first row (21); and three rows of main blast holes, with 9 holes in the first row (11), 8 holes in the second row (12), and 7 holes in the third row (13). A total of 47 blast holes were arranged, including 12 pre-splitting holes and 35 other blast holes. The borehole layout uses a triangular arrangement. The explosives used are porous granular ammonium nitrate explosive (AMF) and latex explosive. Two types of latex explosive are used: one with a diameter of φ32 and the other with a diameter of φ50. The main borehole and buffer boreholes use φ50 latex explosive as the detonator, and digital electronic detonators are used for network deployment. Pre-splitting boreholes use bamboo strips to connect the latex explosives in series. The latex explosives on the bamboo strips are detonated by a detonating detonator. Pre-splitting boreholes are detonated at least 100ms prior to the first borehole in the main borehole area. The charge per meter of a φ150 down-the-hole borehole is Q_single = ρπr. 2 = (0.83~0.87)×3.14×7.52≈15kg; where ρ is the density of the explosive, and ANFO explosives are generally taken as 0.83~0.87g / cm³. 3 This time, 0.85 g / cm³ was taken. 3 , where r is the borehole radius.

[0044] First, second, and third rows of main gun holes: First row main gun hole 11, borehole diameter D Z1 =150mm, hole depth L Z1 =15m, row spacing b Z1 =4m, borehole density coefficient m=0.8~1.4, hole spacing a Z1 =mb Z1 =1×4=4m, filling height h Z1 =(30~40)D Z1 Take 33 × 0.15 = 4.5m, and the explosive consumption per unit volume q Z1 Equal to 0.45~0.6kg / m 3 The unit consumption of explosives in this case is q Z1 Take 0.6 kg / m 3 The first row of main gun ports 11 has 9 gun ports, and the total charge is based on Q. Z1 =q Z1 a Z1 b Z1 L Z1 ×9=0.6×4×4×15×9=1296kg. The second row of main gun holes is 12, with a borehole diameter D.Z2 =150mm, hole depth L Z2 =22m, row spacing b Z2 =4m, borehole density coefficient m=0.8~1.4, hole spacing a Z2 =mb Z2 =1×4=4m, filling height h Z2 =(30~40)D Z2 Take 33 × 0.15 = 4.5m, and the explosive consumption per unit volume q Z2 =0.45~0.6kg / m 3 The unit consumption of explosives in this case is q Z2 Take 0.6 kg / m 3 The total propellant charge of the second row of main gun holes 12 is based on Q. Z2 =q Z2 a Z2 b Z2 L Z2 ×8=0.6×4×4×22×8=1690kg. The third row of main gun holes 13 has a borehole diameter D. Z3 =150mm, hole depth L Z3 =27m, row spacing b Z3 =4m, borehole density coefficient m=0.8~1.4, hole spacing a Z3 =mb Z3 =1×4=4m, filling height h Z3 =(30~40)D Z3 Take 33 × 0.15 = 4.5m, and the explosive consumption per unit volume q Z3 Equal to 0.45~0.6kg / m 3 The unit consumption of explosives in this case is q Z3 Taking 0.6 kg / m³, the total charge of the third row of main gun holes 13 is based on Q. Z3 =q Z3 a Z3 b Z3 L Z3 ×7=0.6×4×4×27×7=1814kg. Total propellant charge Q for the three main gun ports. Z =Q Z1 +Q Z2 +Q Z3 =1296+1690+1814=4800kg.

[0045] Two rows of buffer holes: The first row of buffer holes 21, closest to the main gun hole, has 6 gun holes with a diameter D. H1 =150mm, hole depth L H1 =10m, row spacing b H1 =4m, borehole density coefficient m=0.8~1.4, take m=1.0, hole spacing a H1 =mb H1=1×4=4m, filling height h 填1 =(30~40)D H1 Take 33 × 0.15 = 4.5m. Based on actual blasting experience on site, the buffer hole of 10m is filled to 4m. The explosive consumption per unit is q. h1 The range is 0.45~0.6kg / m 3 This design q H1 Take 0.45 kg / m 3 Q 缓1 =q H1 a H1 b H1 L H1 6 = 0.45 × 4 × 4 × 10 × 6 = 432 kg. The second row of buffer holes 22, near the pre-splitting hole, has 5 blast holes with a borehole diameter D. H2 =150mm, hole depth L H2 =6m, row spacing b H2 =4m, borehole density coefficient m=0.8~1.4, take 1.0, hole spacing a H2 =mb H2 =1×4=4m, filling height h 填2 =(30~40)D H2 Take 33 × 0.15 = 4.5m. Based on actual blasting experience on site, fill the 6m buffer hole with 3m. Explosive consumption per unit length q H2 The range is 0.45~0.6kg / m 3 This design q H2 Take 0.45 kg / m 3 Q 缓2 =q H2 a H2 b H2 L H2 5 = 0.45 × 4 × 4 × 6 × 5 = 216 kg; Total charge Q of the two rows of buffer holes H =Q 缓1 +Q 缓2 =432+216=648kg.

[0046] A row of pre-splitting boreholes: Based on the above buffer borehole parameters, the charge Q of the upper step pre-splitting borehole 31 can be obtained. Y上 Equal to 5.4 kg, the charge Q for the pre-splitting hole 32 in the lower step is 32. Y下 This equals 14 kg, thus determining the charge Q per pre-splitting hole. Y =Q Y上 +Q Y下 =5.4 + 14 = 19.4 kg. A total of 12 pre-splitting holes were designed, with a total charge Q for the pre-splitting holes. Y总 =Q Y ×12=233kg.

[0047] The total amount of propellant Q in this experiment 总 =Q Z +Q H +Q Y总 =4800+648+233=5681kg. The pre-splitting holes, main gun holes and buffer holes are all connected by digital electronic detonators. The pre-splitting holes are detonated more than 100ms before the first detonating main gun hole. After the blast, there are pre-cracks of more than 10cm at the pre-splitting holes.

[0048] Subsequent on-site tracking and analysis of the blasting location revealed that the pre-splitting half-wall porosity of the upper bench was significant, and the half-wall porosity of the lower bench also met design requirements; there were no protruding walls at the merging point of the upper and lower benches; the slope angles of the upper and lower benches were consistent with the design; and the overall merged boundary slope surface was regular and free of debris. This invention, by deepening the main blast hole depth and directly drilling the pre-splitting holes to the design boundary line of the lower bench, and then adjusting the internal charge structure of the pre-splitting holes and the drilling depth of the main blast hole, successfully achieved a one-time blasting method for merging benches. This ultimately solved many problems such as the difficulty of drilling the lower bench of the merged slope; the overall slope angle exceeding the design angle after the boundary; and the significant safety hazards posed by slope breakage. Therefore, this method is technically simple, easy to operate and construct, and has high drilling efficiency, meeting the needs of large-scale open-pit mine production and construction. It can be applied to both metal and non-metal mines and has broad prospects.

Claims

1. A pre-splitting borehole structure with stepped merging, characterized in that: It includes pre-splitting holes (3), buffer holes and main blasting holes; the pre-splitting holes (3) are arranged in a row on the design boundary slope line of the upper step (51), and extend diagonally downwards to the bottom and below of the lower step (52). The perforation angle of the pre-splitting holes (3) is the design angle of the slope after blasting; the part of the pre-splitting holes (3) located on the upper step (51) is the upper step pre-splitting hole (31), and the part located on the lower step (52) is the lower step pre-splitting hole (32). The decoupling coefficient of the upper step pre-splitting hole (31) should be less than the decoupling coefficient of the lower step pre-splitting hole (32); the buffer holes are arranged in front of the pre-splitting holes (3), and the main blasting holes are arranged in front of the buffer holes.

2. The pre-splitting borehole structure with stepped merging according to claim 1, characterized in that: The decoupling coefficient of the upper step pre-cracked hole (31) is 0.6 to 0.7 times that of the lower step pre-cracked hole (32).

3. The pre-splitting borehole structure with stepped merging according to claim 1, characterized in that: The buffer holes are arranged in two rows, and the main gun holes are arranged in at least three rows.

4. The pre-splitting borehole structure with stepped merging according to claim 3, characterized in that: The perforation angle of the first row of buffer holes (21) near the front is 78° to 85°, and the perforation angle of the second row of buffer holes (22) at the rear is 64° to 75°.

5. The pre-splitting borehole structure with stepped merging according to claim 3, characterized in that: The last row of main gun holes has no excessive depth on the upper step (51), while the main gun holes of the other rows extend into the lower step (52).

6. The pre-splitting borehole structure with stepped merging according to claim 1, characterized in that: The diameter of the pre-splitting hole is 0.55 to 0.65 times that of the main blast hole.

7. A pre-splitting borehole structure with stepped merging according to any one of claims 1-6, characterized in that: The charging sections of the upper step pre-splitting hole (31) are, from top to bottom, the upper step pre-splitting hole weakening section (311), the upper step pre-splitting hole normal section (312), and the upper step pre-splitting hole strengthening section (313). The detonator is connected in the forward direction to the latex explosive in the upper step pre-splitting hole strengthening section (313). The charging sections of the lower step pre-splitting hole (32) are, from top to bottom, the lower step pre-splitting hole upper strengthening section (321), the lower step pre-splitting hole normal section (322), and the lower step pre-splitting hole lower strengthening section (323). The detonator is connected in the forward direction to the latex explosive in the lower step pre-splitting hole upper strengthening section (321). The latex explosives in the upper step pre-splitting hole (31) and the lower step pre-splitting hole (32) are connected in series by detonating cord.

8. The pre-splitting borehole structure with stepped merging according to claim 7, characterized in that: The charge length of the normal section (312) of the upper step pre-crack hole is 70% to 80% of the total charge length of the upper step pre-crack hole (31). The charge per unit length of the reinforced section (313) of the upper step pre-crack hole is 2 to 4 times that of the charge per unit length of the normal section (312) of the upper step pre-crack hole. The charge per unit length of the weakened section (311) of the upper step pre-crack hole is 0.45 to 0.55 times that of the charge per unit length of the normal section (312) of the upper step pre-crack hole. The charge length of the normal section (322) of the lower step pre-crack hole is 76% to 82% of the total charge length of the lower step pre-crack hole (32). The charge per unit length of the upper reinforced section (321) and the lower reinforced section (323) of the lower step pre-crack hole is 2 to 4 times that of the charge per unit length of the normal section (322) of the lower step pre-crack hole.

9. The pre-splitting borehole structure with stepped merging according to claim 7, characterized in that: The upper step pre-cracked hole (31) is equipped with a spacer at a distance of 3 to 4.5 m from the hole opening, and the upper part of the spacer is filled as a filling section.

10. A pre-splitting blasting method for step merging, employing the pre-splitting borehole structure described in any one of claims 1-9, characterized in that: The upper step pre-splitting hole (31) and the lower step pre-splitting hole (32) are detonated simultaneously with a 0ms delay; the main blast hole is detonated hole by hole using isochronous lines, and the buffer hole is detonated hole by hole using isochronous lines.

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