A bench blasting method for reducing the large block rate of bedded rock mass in an open pit mine
By setting up auxiliary blasting zones and auxiliary blast holes outside the normal blasting zone during open-pit mining, the problem of large block ratio caused by ore collapse and sliding was solved, resulting in more uniform ore block size and higher loading and transportation efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HEBEI IRON & STEEL GRP MINING
- Filing Date
- 2023-06-21
- Publication Date
- 2026-05-26
AI Technical Summary
During open-pit mining, when the ore body dips at an angle less than the designed bench slope angle, it is prone to collapse and slide, resulting in the formation of large or extra-large ore blocks, which affects loading and transportation efficiency and increases production costs.
An auxiliary blasting zone is set up on the side of the normal blasting zone of the ore body away from the bench slope, and auxiliary blast holes are set up in this zone. Pre-blasting is carried out using auxiliary blast holes of specific depth and arrangement to reduce the proportion of large blocks.
By pre-blasting through auxiliary blast holes, easily collapsible rock masses can be effectively broken, reducing the proportion of large blocks, improving loading efficiency, and reducing production costs.
Smart Images
Figure CN116858049B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of open-pit mining technology, and in particular to a bench blasting method for reducing the proportion of large blocks in bedding rock mass in open-pit mines. Background Technology
[0002] Open-pit mining employs bench blasting for mining and rock stripping. During mining, blast holes are drilled and arranged on the bench in a specific manner, followed by the loading of explosives and blasting. This separates the ore to be mined from the parent rock mass, creating fragments. The size and quantity of these fragments (i.e., the percentage of large pieces) significantly impact subsequent shoveling, loading, transportation, and beneficiation processes, directly affecting shoveling, loading, transportation, beneficiation efficiency, and production costs.
[0003] To improve production efficiency, large open-pit mines often use rotary drilling rigs for blasting, with the blast holes perpendicular to the bench surface. When the dip angle of the ore layer is in sync with the bench slope angle, and the dip angle is less than the designed bench slope angle, the ore mass is prone to collapse and slide, producing large or super-large chunks of ore. Figure 1 As shown, during open-pit mining, the ideal step slope formed is the designed step slope represented by line BE (i.e., the step slope that should be formed, the angle between this step slope and the horizontal plane is the designed step face angle), and line GF represents the new step slope that should be formed after one blast. However, because the dip angle of the ore layer is dip-sloping in the same direction as the step slope angle, and the dip angle α of the ore layer is less than the designed step slope angle, the actual step slope formed during production is the step slope represented by line BA, whose dip angle (the same as the dip angle of the ore layer) α < 75°. The main reason for this is that during open-pit mining blasting, the ore and rock mass within the GFCD range is prone to collapse and slide due to the damage to the structural plane, making it impossible to form a new step slope. Figure 1 The slope shown as BE (or GF) has an angle that cannot reach the designed 75°. Furthermore, the ore body within the GFCD area has collapsed and slid, forming many large or oversized blocks, ultimately creating the stepped slope represented by line DC. According to regulations, these large or oversized blocks can only be mechanically broken into suitable sizes for loading and transportation, severely impacting the efficiency of subsequent shoveling, loading, and transportation operations in the open-pit mine. At the same time, mechanical crushing significantly increases the mine's production costs. The higher the proportion of large blocks, the greater the decrease in efficiency and the increase in production costs for open-pit mine shoveling, loading, and transportation. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a bench blasting method to reduce the proportion of large blocks in bedding rock mass in open-pit mines, so as to avoid the collapse and sliding of the rock mass.
[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: an auxiliary blasting zone is arranged on the side of the normal blasting zone of the ore body away from the bench slope; the width W2 of the auxiliary blasting zone is calculated by formula (1):
[0006]
[0007] In equation (1), W2 is the width of the auxiliary blasting zone, m; H is the height of the bench, m; α is the dip angle of the rock strata, °;
[0008] The auxiliary blasting zone is provided with at least one row of auxiliary blast holes. The arrangement of the auxiliary blast holes and the spacing between rows are the same as those in the normal blasting zone. The depth of each row of auxiliary blast holes is calculated using formula (2):
[0009] h n =H-n·b·tanα (2)
[0010] In equation (2), h n denoted as denoted as the depth of the nth row of auxiliary blast holes, in meters; H is the step height, in meters; n is the number of rows of auxiliary blast holes, with the row closest to the step slope being the first row; b is the row spacing of the auxiliary blast holes, in meters; α is the dip angle of the rock strata, in degrees.
[0011] Furthermore, the depth of the auxiliary borehole is not less than 3.5m.
[0012] Furthermore, the auxiliary blasting zone detonates after the normal blasting zone has detonated.
[0013] The beneficial effects of adopting the above technical solution are as follows: In areas behind the normal blasting zone in mines where large and extra-large ore blocks are generated due to the collapse and sliding of ore-bearing rock along structural surfaces (as shown in the GFCD area in the figure), this invention arranges auxiliary blasting holes according to the spacing and depth of the blast holes in the normal blasting zone to pre-blast and break up this part of the ore-bearing rock, making it reach a suitable block size, thereby reducing the proportion of large blocks. In bench blasting, this invention uses auxiliary blasting holes to effectively break up the ore-bearing rock in the auxiliary blasting zone, solving the problem of large and even extra-large blocks being generated by the collapse and sliding of ore-bearing rock along joint surfaces after the normal blasting holes are blasted. This effectively reduces the proportion of large blocks. The arrangement of auxiliary blasting holes allows for a more uniform distribution of explosives within the rock to be blasted, resulting in more uniform block size and a lower proportion of large blocks after blasting, which is beneficial to improving the efficiency of subsequent loading operations. Attached Figure Description
[0014] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.
[0015] Figure 1 This is a schematic diagram of a rock mass structure that is prone to collapse after conventional blasting methods.
[0016] Figure 2 This is a cross-sectional view of the borehole arrangement for the stepped blasting described in this invention;
[0017] Figure 3 This is a top view of the borehole arrangement for the stepped blasting described in this invention.
[0018] In the diagram: I, Normal blasting zone; II, Auxiliary blasting zone; III, Rock stratum structure surface; IV, Bench slope; I-1, First row of main blast holes in normal blasting zone; I-2, Second row of main blast holes in normal blasting zone; I-3, Third row of main blast holes in normal blasting zone; I-4, Fourth row of main blast holes in normal blasting zone; II-1, First row of auxiliary blast holes in auxiliary blasting zone; ①, Main blast hole; ②, Auxiliary blast hole; α, Rock stratum dip angle; H, Bench height; L, Blasting zone length; W1, Normal blasting zone width; W2, Auxiliary blasting zone width. Detailed Implementation
[0019] Figure 2 , Figure 3 As shown, the bench blasting method for reducing the proportion of large blocks in bedding rock mass in open-pit mines adopts the following steps: 1) Layout of blast holes in the normal blasting zone: The normal blasting zone I is located near the bench slope IV, which is the blasting range during normal mine production, as shown in the figure. Figure 2 , 3 The area comprised of points BB'CC' is defined by the normal blasting zone length L, normal blasting zone width W1, and bench height H (normal blasting zone height). Holes are driven perpendicularly from normal blasting zone I towards the ore-rock stratum structure plane III, forming at least one row of main blast holes. Figure 2 , 3 In the normal blasting zone, the first row of main blasting holes I-1, the second row of main blasting holes I-2, the third row of main blasting holes I-3, and the fourth row of main blasting holes I-4 are arranged according to the arrangement and spacing of blasting holes in conventional blasting during normal mine production. Figure 2 , 3 The spacing between the main gun holes ① is a, and the row spacing of the gun holes is b. Generally, a > b. The main gun holes ① between rows are arranged in an alternating diamond pattern, that is, the main gun holes of the next row are directly opposite the positions of the adjacent gun holes of the previous row.
[0020] 2) Layout of blast holes in the auxiliary blasting zone: The auxiliary blasting zone II is located on the side of the normal blasting zone I away from the bench slope IV, such as... Figure 2 , 3 The area comprised of the four points CC'DD' is characterized by the following dimensions: the auxiliary blasting zone has the same length as the normal blasting zone (L), the auxiliary blasting zone width (W2), and the maximum height of the auxiliary blasting zone (H, the step height). Its bottom surface exhibits... Figure 2The slope shape shown by the dashed line CD is the same as the final stepped slope formed after blasting. The width W2 of the auxiliary blasting zone is calculated by formula (1):
[0021]
[0022] In equation (1), W2 is the width of the auxiliary blasting zone, m; H is the step height, m; α is the rock dip angle, °, which is also the actual step slope angle.
[0023] In auxiliary blasting zone II, drill blast holes vertically into the ore and rock mass to form at least one row of auxiliary blast holes, such as... Figure 2 , 3 In the auxiliary blasting zone, the first row of auxiliary blasting holes II-1; the main blasting holes ① are arranged according to the arrangement and spacing of the main blasting holes ① in the normal blasting zone; such as Figure 2 , 3 The spacing between auxiliary blast holes ② is a, and the row spacing is b. Generally, a > b. The auxiliary blast holes ② between rows are arranged in a staggered diamond pattern, that is, the position of the next row of auxiliary blast holes is directly opposite the position of the adjacent blast holes of the previous row of auxiliary blast holes, and the first row of auxiliary blast holes is staggered with the last row of main blast holes.
[0024] With the standard that the depth of auxiliary blast holes ② is not less than 3.5m and the filling depth of the hole opening is not less than 3m, the auxiliary blast holes in each row are designed; the depth of each row of auxiliary blast holes is calculated using formula (2):
[0025] h n =H-n·b·tanα (2)
[0026] In equation (2), h n denoted as denoted as the depth of the nth row of auxiliary blast holes, in meters; H is the step height, in meters; n is the number of rows of auxiliary blast holes, with the row closest to the step slope being the first row; b is the row spacing of the auxiliary blast holes, in meters; α is the dip angle of the rock strata, in degrees.
[0027] 3) Charge and detonation: Explosives are loaded into the main blast hole ① and the auxiliary blast hole ②. First, the normal blasting zone I is detonated sequentially with a certain time difference. Then, the auxiliary blasting zone II is detonated sequentially with a certain time difference.
[0028] 4) This method enables the pre-fracture and effective breaking of ore-bearing rock masses in areas prone to collapse and slide along structural planes (as shown in the GFCD area in the figure), thereby effectively reducing the collapse and slide of ore-bearing rock masses behind normal blasting zone I. The proportion of large blocks has been reduced from 18%–26% to 10%–18%. Through auxiliary blast hole arrangement, this method can achieve a more uniform distribution of explosives within the rock mass to be blasted, resulting in more uniform rock mass size and a lower proportion of large blocks after blasting, which is beneficial for improving the efficiency of subsequent loading operations.
[0029] Example 1: The bench blasting method for reducing the proportion of large blocks in bedding rock mass in open-pit mines is described in detail below.
[0030] 1) Figure 2 , Figure 3 As shown, the normal blasting zone I consists of four points: BB, CC, and represents the blasting range during normal mine production. Its length is L = 120m and its width is W1 = 27m. Within this zone, the spacing between the main blast holes ① is a = 8m, the row spacing is b = 7m, and the blast holes between rows are staggered, representing the mine's original blast hole layout.
[0031] 2) The auxiliary blasting zone II is composed of four points CC'DD', with a length of L = 120m and a width of W2 = 15m. Within this zone, the spacing between the auxiliary blasting holes ② is a = 8m, and the distance between the auxiliary blasting zone II-1 row of blasting holes and the normal blasting zone I-4 row of blasting holes is b = 7m.
[0032] 2.1) The geological compass and steel ruler are used to measure the exposed rock mass structure planes to obtain the dip angle α of the rock strata and the spacing between the structure planes.
[0033] 2.2) The width of the auxiliary blasting zone II is calculated and determined using formula (1), where α = 45° and the step height H = 15m:
[0034]
[0035] The calculated width of the auxiliary blasting zone is W2 = 15m.
[0036] 2.3) Based on the dip angle of the ore strata and the spacing of the boreholes, α = 45°, bench height H = 15m, and borehole spacing b = 7m, the depth hn of each row of auxiliary boreholes ② in auxiliary blasting zone II is calculated sequentially according to formula (2):
[0037] h1 = 15 - 1 × 8 × tan45° = 7m;
[0038] It is evident that only one row of auxiliary blast holes can be set, and the depth of the auxiliary blast holes is 7m.
[0039] 3) Drilling, charging, and blasting are carried out according to the normal mine production procedures. The charge amount for each row of auxiliary blast holes is determined based on the depth of auxiliary blast holes ② and the filling depth at the hole opening. During blasting, the four rows of blast holes I-1, I-2, I-3, and I-4 are detonated sequentially with a certain time difference; after the main blast holes in row I-4 of the normal blasting zone I are detonated, the auxiliary blast holes in auxiliary blasting zone II are detonated sequentially with a certain time difference.
[0040] 4) After adopting the above process steps, the actual inclination angle of the formed step is 45°. The auxiliary blasting of the blast hole effectively pre-fractures the ore rock mass in the area prone to collapse and sliding (GFCD range in the figure). It can be seen that the step blasting method of reducing the large block rate of the bedding rock mass in the open-pit mine effectively reduces the possibility of large blocks formed due to the collapse and sliding of the ore rock mass along the structural plane. The large block rate is 16%.
[0041] Example 2: The specific steps of the bench blasting method for reducing the proportion of large blocks in bedding rock mass in open-pit mines are as follows.
[0042] 1) Figure 2 , Figure 3 As shown, the normal blasting zone I consists of four points: BB, CC, and represents the blasting range during normal mine production. Its length is L = 120m and its width is W1 = 27m. Within this zone, the spacing between the main blast holes ① is a = 8m, the row spacing is b = 7m, and the blast holes between rows are staggered, representing the mine's original blast hole layout.
[0043] 2) The auxiliary blasting zone II is composed of four points CC'DD', with a length of L = 120m and a width of W2 = 21.42m. Within this zone, the spacing between the auxiliary blasting holes ② is a = 8m, and the distance between the auxiliary blasting zone II-1 row of blasting holes and the normal blasting zone I-4 row of blasting holes is b = 7m.
[0044] 2.1) The geological compass and steel ruler are used to measure the exposed rock mass structure planes to obtain the dip angle α of the rock strata and the spacing between the structure planes.
[0045] 2.2) The width of the auxiliary blasting zone II is calculated and determined using formula (1), where α = 35° and the step height H = 15m:
[0046]
[0047] The calculated width of the auxiliary blasting zone is W2 = 21.42m.
[0048] 2.3) Based on the dip angle of the ore strata and the spacing of the blast holes, α = 35°, bench height h = 15m, and blast hole spacing b = 8m, the depth h of each row of auxiliary blast holes ② in the auxiliary blasting zone II is calculated sequentially according to formula (2). n Implementation example:
[0049]
[0050] Since the depth of the second row of auxiliary blast holes is close to 3.5m, the depth of the third row of auxiliary holes will no longer be calculated. That is, two rows of auxiliary blast holes will be arranged in the auxiliary blasting area.
[0051] 3) Drilling, charging, and blasting are carried out according to the normal mine production procedures. The charge amount for each row of auxiliary blast holes is determined based on the depth of auxiliary blast holes ② and the filling depth at the hole opening. During blasting, the four rows of blast holes I-1, I-2, I-3, and I-4 are detonated sequentially with a certain time difference; after the main blast holes in row I-4 of the normal blasting zone I are detonated, the auxiliary blast holes in auxiliary blasting zone II are detonated sequentially with a certain time difference.
[0052] 4) After adopting the above process steps, the actual inclination angle of the formed step is 35°. The auxiliary blasting of the blast hole effectively pre-fractures the ore rock mass in the area prone to collapse and sliding (GFCD range in the figure). It can be seen that the step blasting method of reducing the large block rate of the bedding rock mass in the open-pit mine effectively reduces the possibility of large blocks formed due to the collapse and sliding of the ore rock mass along the structural plane. The large block rate is 12%.
Claims
1. A bench blasting method for reducing the proportion of large blocks in bedding rock mass in open-pit mines, characterized in that: An auxiliary blasting zone is arranged on the side of the normal blasting zone of the ore body away from the bench slope; the width W2 of the auxiliary blasting zone is calculated by formula (1): （1） In equation (1), W2 is the width of the auxiliary blasting zone, m; H is the step height, m; α is the rock dip angle, °; The auxiliary blasting zone is equipped with at least one row of auxiliary blast holes. The arrangement of the auxiliary blast holes and the spacing between rows are the same as those in the normal blasting zone. The depth of each row of auxiliary blast holes is calculated using formula (2): （2） In equation (2), h n denoted as denoted as the depth of the nth row of auxiliary blast holes, in meters; H is the step height, in meters; n is the number of rows of auxiliary blast holes, with the row closest to the step slope being the first row; b is the row spacing of the auxiliary blast holes, in meters; α is the dip angle of the rock strata, in degrees. The auxiliary blasting zone detonates after the normal blasting zone has been detonated.
2. The bench blasting method for reducing the proportion of large blocks in bedding rock mass in open-pit mines according to claim 1, characterized in that: The depth of the auxiliary blast hole is not less than 3.5m.
3. A bench blasting method for reducing the proportion of large blocks in bedding rock mass in open-pit mines according to claim 1 or 2, characterized in that: The auxiliary blast holes between rows are arranged in a staggered, diamond-shaped pattern.