Stepped blasting method for eliminating slope and ore rock body bedding down-blast root

Abstract

The application discloses a bench blasting method for eliminating the blasting root of a slope surface and a stratum of a mine rock mass, and when the blasting root appears, an auxiliary micro-inclined blast hole is constructed at the bottom of the bench slope to perform auxiliary blasting; the auxiliary micro-inclined blast hole is inclined inwards and downwards, the inclination angle γ is 3-5°, the distance h1 from the blast hole to the root is 100-200 mm, and the horizontal length l of the blast hole is calculated according to formula (1). The method adopts the auxiliary micro-inclined blast hole blasting technology, performs auxiliary blasting on the mine rock mass under the bench slope surface, and eliminates the blasting root, so that the problem that the resistance line of the bench root is too large under the stratum condition of the bench slope surface and the mine rock mass and a large root is generated after blasting can be effectively solved, the large block rate of the mine rock mass under the bench slope surface after blasting is reduced, and the working efficiency of subsequent shovel loading and transportation of the open-pit mine is improved.

Description

Technical Field

[0001] This invention belongs to the field of open-pit mining technology, and in particular to a bench blasting method for eliminating the foundation of bench blasting on open-pit mine bench slopes. Background Technology

[0002] Open-pit mining typically employs bench blasting to separate the ore from the parent rock mass and break it into fragments. To ensure production safety, bench blasting creates a bench slope with a certain angle to the horizontal plane; this slope becomes the free surface for the next blast. The bench slope angle is a crucial parameter in open-pit mining, significantly influenced by factors such as the properties of the ore, joints, bedding, fissure development, and the angle between the structural plane and the bench slope. When the bench slope in open-pit mining is bedding-parallel to the structural plane of the ore mass, after each bench blast, the ore behind the blast zone will collapse and slide along the structural plane, forming a bench slope with an angle equal to the dip of the structural plane. When the dip angle of the structural plane is less than the designed bench slope angle, the resulting bench slope angle is gentler, leading to an excessively large resistance line at the bench base during the next blast cycle, resulting in a larger base and directly impacting the efficiency of loading and unloading operations.

[0003] The larger the foundation formed after bench blasting, the greater the shoveling resistance to subsequent loading equipment, affecting its efficiency. Simultaneously, the significant undulations in the smoothness of the newly formed bench surface also negatively impact the efficiency of transportation equipment. This severely affects the efficiency of subsequent shoveling, loading, and transportation operations in open-pit mines, increasing production costs. Existing literature has explored solutions using inclined or horizontal holes to address the problem of excessive foundation resistance, but these methods are unsuitable for handling large foundations formed along the bedding planes of open-pit mine benches. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a bench blasting method to eliminate the foundation of blasting along the bedding plane of the ore body, so as to effectively reduce the foundation formation.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a row of auxiliary slightly inclined blast holes are constructed at the bottom of the stepped slope to assist the main blast holes in blasting; the auxiliary slightly inclined blast holes are inclined inward and downward with an inclination angle γ of 3° to 5°, the distance h1 from the center of the hole to the bottom of the slope is 100 to 200 mm, and the horizontal length l of the blast hole is calculated according to formula (1):

[0006]

[0007] In formula (1): l is the horizontal length of the auxiliary micro-inclined borehole, m; H is the step height of the step slope, m; β is the slope angle of the step slope, °.

[0008] Furthermore, the spacing between the auxiliary micro-tilted boreholes, b', is 3.5 to m, and the borehole diameter is 90 to 100 mm.

[0009] Furthermore, the first row of main gun holes, the auxiliary slightly inclined gun holes, and the subsequent rows of main gun holes were successively blasted using micro-differential blasting.

[0010] Furthermore, the dimensions of the primary blasting zone are optimized during the design and construction of the bench blasting. The width W2 of the primary blasting zone after optimization is calculated using formula (3):

[0011]

[0012] In formula (3): W2 is the width of the optimized primary blasting zone, m; H is the step height, m; β is the slope angle, °n is the number of main blasting holes in the primary blasting zone; b is the spacing between the main blasting holes in the primary blasting zone, m; c is the distance between the rotary drilling rig and the top of the step slope as specified in the regulations, m.

[0013] Furthermore, the width W2 of the optimized blasting zone is calculated using formula (4):

[0014]

[0015] In equation (4): L2 is the width of the blasting zone after optimization, in meters; L1 is the width of the blasting zone before optimization, in meters.

[0016] The beneficial effects of adopting the above technical solution are as follows: The present invention uses the auxiliary micro-inclined blast hole blasting technology to assist in the blasting of the ore and rock mass below the slope of the open-pit mine bench, so as to eliminate the blasting foundation. This can effectively solve the problem that the bench foundation resistance line is too large under the condition of the open-pit mine bench slope and the ore and rock mass being in stratum, resulting in a large foundation after blasting. It is also conducive to reducing the proportion of large pieces of ore and rock mass after blasting below the bench slope and improving the efficiency of subsequent shoveling and transportation in the open-pit mine.

[0017] This invention further optimizes the size and structure of the blasting zone, effectively reducing the number of foundation formations and assisting in the construction of micro-inclined blast holes, while ensuring that the mine's production capacity is not reduced, thereby effectively improving the mine's production efficiency. Attached Figure Description

[0018] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0019] Figure 1 This is a schematic cross-sectional view of the stepped slope used for borehole arrangement in this invention.

[0020] Figure 2 This is a top view schematic diagram of the borehole arrangement described in this invention.

[0021] In the diagram: Ⅰ. Ore rock mass structure surface; Ⅱ. Open-pit mine bench slope; Ⅲ. Open-pit mine designed bench slope; 1-1. First row of main blast holes in normal blasting zone; 1-2. Second row of main blast holes in normal blasting zone; 1-3. Third row of main blast holes in normal blasting zone; 3-1. First row of main blast holes in optimized expansion zone; 3-2. Second row of main blast holes in optimized expansion zone; A, B, B', C, C', D-D' are the location points of the bench slope; 1. Main blast hole; 2. Auxiliary slightly inclined blast hole; 3. Blast hole in optimized expansion zone. Detailed Implementation

[0022] The stepped slope surface produced by the stepped blasting is as follows: Figure 1 As shown, according to the design bench blasting parameters of the open-pit mine bench slope III, after bench blasting, due to the bedding plane, the actual open-pit mine bench slope II will be formed from the rock mass structure plane I. In the figure, α is the dip angle of the open-pit mine bench slope III, β is the slope angle of the bench slope, that is, the rock stratum dip angle, A-B is the actual formed bench slope, and A-B' is the designed bench slope.

[0023] The bench blasting method for eliminating the foundation of blasting along bedding planes and rock masses adopts the following process:

[0024] 1) Auxiliary blasting: Under the condition that the slope of the open-pit mine bench is in line with the ore body or under any other condition, the bench blasting adopts the main bench blasting + auxiliary blasting.

[0025] 1.1) Assisted slightly inclined borehole: Figure 1 , Figure 2 As shown, auxiliary slightly inclined blast holes 2 are used to assist in blasting the ore and rock mass below the slope of the open-pit mine bench, so as to eliminate the blasting foundation. The auxiliary slightly inclined blast holes are arranged at a certain height above the bottom of the bench slope and the foundation. The blast holes are slightly inclined inward and downward, with an angle γ of 3° to 5° with the horizontal plane. The diameter of the blast holes is 90 to 100 mm. The distance h1 from the center of the hole to the bottom of the slope is 100 to 200 mm. The horizontal length l of the blast holes is calculated according to formula (1):

[0026]

[0027] In formula (1): l is the horizontal length of the auxiliary micro-inclined blast hole, that is, the length of the auxiliary micro-inclined blast hole in the horizontal direction, m; H is the step height of the step slope, m; β is the slope angle of the step slope, °.

[0028] The auxiliary micro-inclined blast holes have a blast hole plugging length of 3.0 to 3.5 m. The auxiliary micro-inclined blast holes are arranged in a row along the length of the blasting zone, and the b' of adjacent auxiliary micro-inclined blast holes is 3.5 to 4.0 m.

[0029] 1.2) Main blasting of benches: The main blasting of benches adopts conventional bench blasting technology, or bench blasting technology with optimized blast zone size and structure as described below; the main blast hole 1 of the main blasting of benches adopts the original blast hole diameter, hole network parameters and other blasting technical parameters of the mine.

[0030] 1.3) Blasting process: To avoid flyrock that may be generated during the blasting of the auxiliary micro-inclined blast holes, the first row of main blast holes is detonated first, and the blasted ore and rock cover the auxiliary micro-inclined blast holes; then, the auxiliary micro-inclined blast holes are detonated with a micro-delay, lagging behind the first row of main blast holes; then, the second row and subsequent rows of main blast holes are detonated in sequence with a 50μs micro-delay blasting.

[0031] 1.4) The use of auxiliary micro-inclined borehole blasting technology improves the uniformity of explosive distribution in the rock mass to be blasted, and achieves effective crushing of the rock mass below the bench slope. It can effectively solve the problem of excessive resistance line at the base of the bench and large base after blasting when the bench slope and the rock mass are in strata in open mines.

[0032] 2) Optimization of the size and structure of the blasting zone in a single blast: Optimize the size of the blasting zone in a single blast to reduce the number of blasts in open-pit mine production, that is, reduce the number of new steps formed in production, so as to avoid the occurrence of blasting foundation and reduce the construction of auxiliary micro-inclined blast holes.

[0033] 2.1) Based on the area of ​​the blast zone before structural optimization, length L1, and width W1 of the blast zone in a single blasting operation in a mine, calculate the volume V of the object to be blasted and the planar area S of the blast zone, as shown in formulas (2.1) and (2.2):

[0034] V = H × L1 × W1 (2.1);

[0035] S = L1 × W1 (2.2);

[0036] In equations (2.1) and (2.2): V is the volume of the object to be detonated, m 3 H represents the step height of the bench slope, in meters; L1 represents the length of the primary blasting zone before optimization, in meters; W1 represents the width of the primary blasting zone before optimization, in meters. The length and width of the primary blasting zone before optimization are the length and width of the primary blasting zone designed using conventional bench blasting.

[0037] 2.2) Based on the number of main blast holes in a single blast and the potential collapse range of the ore and rock structure, the optimized width W2 of the primary blast zone is calculated using formula (3):

[0038]

[0039] In formula (3): W2 is the width of the optimized primary blasting zone, m; H is the step height, m; β is the slope angle, °; n is the number of main blast holes in the primary blasting zone. The size of n is related to the expected reduction in the number of newly generated steps in open-pit mine blasting and the increase in the width of the primary blasting zone W2. The smaller the expected number of newly generated steps and the larger the increase in width, the larger n will be; b is the spacing of the main blast holes in the primary blasting zone, which is the same as the spacing of the main blast holes designed for conventional step blasting, m; c is the distance from the rotary drilling rig to the top line of the step slope as specified in the regulations, m.

[0040] 2.3) Based on the aforementioned formulas (2) and (3), formula (4) is obtained, which can be used to calculate the optimized length L2 of the primary blasting zone; L2 should not affect the normal operation of the mining and transportation equipment;

[0041]

[0042] In equation (4): L2 is the width of the blasting zone after optimization, in meters; L1 is the width of the blasting zone before optimization, in meters.

[0043] by Figure 1 , Figure 2 Taking the example shown, according to the conventional design, the normal blasting zone has three rows of main blast holes, namely the first row of main blast holes 1-1, the second row of main blast holes 1-2, and the third row of main blast holes 1-3. After optimizing the size and structure of the blasting zone using this method, the optimized expansion zone is formed after the normal blasting zone. The optimized expansion zone is calculated according to formulas (3) and (4). The blast holes 3 in the optimized expansion zone include two rows of main blast holes, namely the first row of main blast holes 3-1 and the second row of main blast holes 3-2. C-C' is the step slope formed by blasting before the blasting zone structure size optimization, and D-D' is the step slope formed by blasting after the blasting zone structure size optimization.

[0044] 2.4) The optimized blast zone size effectively reduces the number of new steps generated during open-pit mine blasting. The reduction in the number of new steps depends on the ratio of W2 to W1. For example, when W2 = 2W1, with a blast zone width of W2, the optimized method requires one blast to form one new step; while the original method requires two blasts with a blast zone width of W2, resulting in two new steps.

[0045] Example: The specific method for eliminating the foundation of open-pit mine bench blasting is as follows.

[0046] 1) Taking a certain open-pit mine as an example, the open-pit mine bench slope and the ore mass exhibit a bedding relationship. Before adopting the solution of this invention, each blast resulted in a large blasting foundation. Later, by using auxiliary micro-inclined blast holes to assist in the blasting of the ore mass below the open-pit mine bench slope, the problem of bench blasting foundation formation was effectively solved.

[0047] 1.1) The auxiliary slightly inclined blast holes are arranged at a certain height above the root of the bottom of the step slope, with the distance from the hole opening to the root being h1 = 200 mm. The blast holes are slightly inclined inward and downward with an inclination angle β of 5°. The diameter of the auxiliary slightly inclined blast holes is 90 mm and the spacing between blast holes is b' = 3.5 m. The step height is H = 15 m and the slope angle is 45°. The horizontal length l of the blast holes is calculated according to formula (1):

[0048]

[0049] The horizontal length of the auxiliary micro-inclined borehole was calculated to be l = 15m.

[0050] 1.2) The main blast holes in the normal blasting zone shall first adopt the blast hole diameter, hole network parameters and other blasting technical parameters originally designed by the mine, namely, the blast hole diameter is 350mm, the center distance of the blast holes in the same row is 7.0m, the row spacing of the blast holes is 8.0m, the blast hole filling length is 5.0m, and micro-delay blasting is used between rows of blast holes, with an initiation time difference of 50μs.

[0051] 1.3) Blasting process: To avoid flyrock that may be generated during the blasting of the auxiliary micro-inclined blast holes, the first row of main blast holes is detonated first, and the blasted ore and rock cover the top of the auxiliary micro-inclined blast holes; then, the auxiliary micro-inclined blast holes are detonated after the first row of main blast holes; then, the second row and subsequent rows of main blast holes are detonated after the auxiliary micro-inclined blast holes in sequence; 50μs micro-delay blasting is used.

[0052] 1.4) Before using auxiliary micro-inclined boreholes for assisted blasting, the maximum height of the blasting foundation reached 1.10–1.8 m. After using auxiliary micro-inclined boreholes for assisted blasting, the maximum height of the blasting foundation was only about 0.15–0.30 m. The newly formed step surface was flat and essentially had no foundation. At the same time, after using auxiliary micro-inclined boreholes for blasting, the explosive energy was evenly distributed under the step slope, and the proportion of large fragments after blasting decreased from about 15% to about 6%.

[0053] 2) Optimization scheme for the size and structure of the blast zone in the primary blast:

[0054] 2.1) Based on the blast zone area before structural optimization (e.g., length L1 = 150m, width W1 = 34m) of a single blast in a mine, the volume V of the object to be blasted and the planar area S of the blast zone are calculated using formula (2):

[0055]

[0056] The calculated volume of the explosive body is V = 76500 m³. 3 The blasting zone has a planar area of ​​S = 5100m² 2 .

[0057] 2.2) The original blasting design of the mine adopted 3 rows of blast holes for one blast. Considering the matching relationship between the length and width of the blasting area, the number of rows for one blast was increased to 5, the row spacing of the blast holes was 8m, and the distance between the roller cone drill and the top line of the bench was c = 3m. Based on the number of rows of the main blast holes for one blast, the possible collapse range of the rock structure, and the inclination angle of the rock structure surface β = 45°, the width W2 of the optimized blasting area (i.e. the distance between AD) was calculated using formula (3).

[0058]

[0059] The width of the blast zone was calculated to be W2 = 50m.

[0060] 2.3) According to formula (4), the optimized length L2 of the primary blasting zone can be calculated:

[0061]

[0062] The optimized blast zone size structure was obtained, with a blast zone length of 120m and a width of 50m for a single blast. A blast zone length of 120m will not affect the normal operation of mining and transportation equipment.

[0063] 2.3) The optimized blasting zone size structure adopted in the mine will not affect the normal operation of the mining and transportation equipment. On the other hand, the optimized blasting zone width (50m) is 1.47 times that of the original design blasting zone width (34m), which reduces the number of new steps generated during the entire open-pit mine production process by 47%. Therefore, it effectively reduces the number of new steps formed during the production process and reduces the probability of blasting foundation formation.

Claims

1. A bench blasting method for eliminating the need for blasting foundations along bedding planes and ore masses, characterized in that: A row of auxiliary slightly inclined blast holes is constructed at the bottom of the step slope to assist the main blast holes in blasting; the auxiliary slightly inclined blast holes are inclined inward and downward with an inclination angle γ of 3° to 5°, the distance h1 from the center of the hole to the bottom of the slope is 100 to 200 mm, and the horizontal length l of the blast hole is calculated according to formula (1): （1） In formula (1): l is the horizontal length of the auxiliary micro-inclined borehole, m; H is the step height of the stepped slope, m; β is the slope angle of the stepped slope, °; The first row of main gun holes, the auxiliary slightly inclined gun holes, and the subsequent rows of main gun holes were successively blasted using micro-differential blasting. The dimensions of the primary blasting zone were optimized during the design and construction of the bench blasting. The width W2 of the primary blasting zone after optimization was calculated using formula (3): （3） In formula (3): W2 is the width of the optimized primary blasting zone, m; H is the step height, m; β is the slope angle, °; n is the number of main blasting holes in the primary blasting zone; b is the spacing between the main blasting holes in the primary blasting zone, m; c is the distance between the rotary drilling rig and the top of the step slope as specified in the regulations, m; The length L2 of the optimized blast zone is calculated using formula (4): （4） In equation (4): L2 is the length of the blasting zone after optimization, in m; L1 is the length of the blasting zone before optimization, in m.

2. The bench blasting method for eliminating the foundation of blasting along the bedding plane of the ore body as described in claim 1, characterized in that: The auxiliary micro-inclined boreholes have a borehole spacing b' = 3.5–4.0 m and a borehole diameter of 90–100 mm.

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