Blasting method and limestone manufacturing method

Abstract

To provide a blast method capable of reducing a low frequency sound occurring in a blast.SOLUTION: A blast method comprises: a charging process of charging an insertion 28 into a blast hole 10 after charging a detonator dynamite 22 and an increasing dynamite 24 on a detonator 20 installed at a bottom of the blast hole 10; and a blast process of executing a blast at the blast hole 10, wherein at least a part of the insertion 28 is fixed to the inside of the blast hole 10 in a state of being charged in a bag body.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] One aspect of the present invention relates to a blasting method and a method for producing limestone.

Background Art

[0002] Generally, blasting means a process of crushing rock formations, etc. in addition to cutting out raw stones in mines or quarries, and also in tunnel construction, demolition work of concrete structures, road construction work, etc. Recently, blasting is being carried out not only in remote areas but also in urban areas, such as in underground excavation work of buildings, power line and pipeline work, and subway work.

[0003] Blasting varies from small-scale ones that blast single rocks to large-scale ones that blast rock formations of tens of thousands of tons, and methods suitable for the object are used. As methods for blasting rock formations, there are a general blasting method (single charge blasting) in which blast holes are drilled in the rock formation and explosives and stemming are filled inside the blast holes for blasting, a method (deck charge blasting) in which explosives and stemming are arranged alternately for blasting to reduce vibration, a method (air deck blasting) in which a void is provided between the explosives and the stemming for blasting, etc. (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The low-frequency sound generated during blasting becomes a factor of noise, so it is desirable to reduce it from the viewpoints of improving the working environment and maintaining the environment of the surrounding area. Therefore, the present disclosure provides a blasting method and a method for producing limestone capable of reducing the low-frequency sound generated during blasting.

Means for Solving the Problems

[0006] The present invention provides a blasting method comprising a loading step of loading a main die and an additional die onto a detonator installed at the bottom of a blast hole, and then filling the blast hole with filler material, and a blasting step of performing blasting in the blast hole, wherein in the loading step, at least a portion of the filler material is fixed inside the blast hole in a state filled with a bag.

[0007] In the above blasting method, at least a portion of the filler material is packed into a bag and fixed inside the blast hole where the detonator, main die, and auxiliary die are loaded. Because the filler material is packed into a bag, the blast hole is effectively capped with a large rock, which suppresses the propagation of the shock wave generated by the blast outwards from the opening of the blast hole, allowing the shock wave to be effectively utilized for fragmentation. As a result, low-frequency noise (below 100 Hz) generated during blasting is reduced, improving the working environment and significantly reducing noise to nearby houses and other structures around the mine. Furthermore, it becomes possible to utilize explosives more effectively, reducing the amount of explosive consumed per unit and thus lowering costs.

[0008] The present invention provides a method for producing limestone, comprising a step of adjusting the particle size of the raw limestone obtained by performing the above-described blasting method in a limestone mine. In this method of producing limestone, since blasting is performed using the above-described blasting method, the low-frequency noise generated during blasting can be reduced. Furthermore, it becomes possible to make effective use of explosives, thereby reducing the cost of producing limestone. [Effects of the Invention]

[0009] This invention provides a blasting method that can reduce low-frequency noise generated during blasting, and a method for producing limestone. [Brief explanation of the drawing]

[0010] [Figure 1] This is a diagram illustrating a blasting method according to one embodiment. [Figure 2] This diagram shows the state of the material filling in the blast hole. [Figure 3]This is a magnified view of the bag fixed to the blast hole and its vicinity. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below, with reference to the drawings as appropriate. However, the following embodiments are illustrative examples for explaining the present invention and are not intended to limit the present invention to the following. In the description, the same reference numerals will be used for elements that are the same or have the same function, and redundant explanations will be omitted as appropriate. Furthermore, unless otherwise specified, positional relationships such as up, down, left, and right will be based on the positional relationships shown in the drawings. Moreover, the dimensional ratios of each element are not limited to the ratios shown in the drawings.

[0012] A blasting method according to one embodiment includes the steps of forming a blast hole, installing a detonator at the bottom of the blast hole and then loading a main die and an additional die in that order, filling the blast hole with filler, and performing blasting in the blast hole. This blasting method may be used, for example, to extract ore in a mine, or in various construction works such as tunnel construction, underground excavation work, or subway construction. In the step of forming a blast hole, the blast hole can be formed using heavy machinery such as a drilling machine.

[0013] In the example shown in Figure 1, the blast hole 10 is formed in the rock mass 40. The rock mass 40 may be the rock mass of a mine (e.g., a limestone mine). In this example, the blast hole 10 is slightly inclined with respect to the vertical direction, but is not limited to this. For example, the blast hole 10 may extend vertically or horizontally. Multiple blast holes 10 may be arranged in a row along the face 41 of the rock mass 40. The bore diameter (inner diameter) of the blast hole 10 may be 70 to 150 mm, or 80 to 130 mm. The resistance R may be 2 to 6 m, or 3 to 5 m. The ratio of resistance R to bore diameter may be 30 to 60. The spacing (hole spacing) between adjacent blast holes 10 may be 2 to 8 m, or 3 to 6 m. The ratio of this spacing to resistance R may be 0.5 to 4, or 1 to 2.

[0014] After forming the blast hole 10, the detonator 20 is introduced through the opening 12 of the blast hole 10 and placed on the bottom surface of the blast hole 10. For example, electric detonators, non-electric detonators, electronic detonators, etc., can be used as the detonator 20. The legs (not shown) of the detonator 20 may be connected to the blaster 30 located outside the blast hole 10. Next, the main die 22 is introduced through the opening 12 and loaded into the inside of the blast hole 10. The main die 22 is called a propulsion charge or detonating dynamite and has the function of fully detonating the booster die 24. Examples of the main die 22 include cast boosters, dynamite, and water-containing explosives.

[0015] Next, the additional die 24 is introduced through the opening 12 of the blast hole 10 and loaded into the inside of the blast hole 10. As the additional die 24 (main explosive), for example, ANFO explosive (ammonium nitrate fuel oil explosive) and water-containing explosive (bulk emulsion explosive) can be used. Of these, ANFO explosive is a type of ammonium nitrate explosive that contains ammonium nitrate as its main component and is mixed with fuel oil. From the viewpoint of cost reduction, ANFO explosive may be used as the additional die 24.

[0016] The bulk emulsion explosive is loaded into the blast hole 10 while mixing the emulsified intermediate raw material (emulsion matrix) with a blowing agent. Inside the blast hole 10, the intermediate raw material and the blowing agent chemically react, causing foaming and sensitization, and functioning as an explosive (additional die 24).

[0017] After loading the additional die 24 into the blast hole 10, filler material 28 is packed on top of the additional die 24 loaded into the blast hole 10. It is preferable to pack the filler material 28 so that a void 26 is provided between the filler material 28 and the additional die 24. This blasting method, in which a void 26 is provided in the blast hole 10, is also called air deck blasting. By having such a void 26, the energy generated by the explosion is reflected within the void 26, thereby improving the crushing effect and reducing the generation of low-frequency waves and flying debris. In addition, the amount of explosive used can be reduced by replacing the explosive in the void 26. Furthermore, crushed stone with a smaller particle size can be obtained due to the generation of secondary waves.

[0018] At least a portion of the material 28 is filled into the bag 35 as shown in Figure 2. The material of the bag 35 is not particularly limited, but it is preferable that it can be filled with the material 28 and expands as the amount of filling increases. Such a bag 35 can be smoothly fixed inside the blast hole 10. The bag 35 may be made of, for example, plastic, rubber, or elastomer. Examples of plastics include polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate, polyvinyl chloride, and nylon. Examples of rubbers include natural rubber, nitrile rubber, silicone rubber, styrene-butadiene rubber, urethane rubber, and fluororubber. Examples of elastomers include olefin-based, vinyl chloride-based, and urethane-based elastomers.

[0019] A tubular (hollow) bag may be used for the bag body 35. For example, the end of the tube is tied to close it to form an empty bag, and the empty bag is inserted into the blast hole 10 from the front end. Once inserted to a predetermined depth, the filler material 28a is filled into the empty bag from the base end (upper end). To fill the empty bag with the filler material 28a, a rod or other material may be used to push the filler material 28a introduced into the empty bag towards the front end (lower end). In this way, a bag body 35 filled with the filler material is obtained. By filling the bag body 35 with the filler material 28a, the bag body 35 is fixed inside the blast hole 10. This makes it possible to create a gap 26 between the additional die 24 and the filler material 28a (bag body 35).

[0020] The bursting hole 10 is in a state as if capped by a large rock due to the bag body 35 fixed inside the bursting hole 10. A part of the charge 28 loaded into the bursting hole 10 may be filled into the bag body 35, and the other part may be filled outside the bag body 35 inside the bursting hole 10. Then, as shown in FIG. 3, the charge 28b filled above the bag body 35 enters between the bag body 35 and the inner wall surface 10A of the bursting hole 10 and is sandwiched between the bag body 35 and the inner wall surface 10A. Such a charge 28b meshes with the charge 28a filled into the bag body 35 through the bag body 35 and suppresses the bag body 35 from falling below the bursting hole 10. For this reason, the blasting operation can be performed more stably. Also, since the void portion 26 can be firmly sealed, the shock wave generated by blasting can be sufficiently and effectively utilized for crushing.

[0021] The mass ratio of the charge 28a filled into the bag body 35 to the entire charge 28 may be 0.05 or more, and may also be 0.1 or more. Thereby, since the function as a cap is sufficiently exhibited, the shock wave generated by blasting is further suppressed from propagating from the opening of the bursting hole to the outside, and the shock wave can be more effectively utilized for crushing. The mass ratio of the charge 28a filled into the bag body 35 to the entire charge 28 may be 0.5 or less, and may also be 0.4 or less. Thereby, the working time required for the preparation of blasting can be sufficiently shortened.

[0022] The upper end 35A of the bag body 35 may be connected to a support body 50 disposed outside the bursting hole 10 as shown in FIG. 2. Thereby, the bag body 35 can be sufficiently prevented from falling downward. The support body 50 may be, for example, a sandbag. The support body 50 may be disposed at an arbitrary position on the ground surface 42 (free surface) in FIG. 1.

[0023] As the filling material 28, the swarf 52 (shavings) generated when the blasting hole 10 is drilled with a heavy machine such as a drilling machine may be used, or crushed sand, crushed stones (including aggregates), etc. prepared separately may be used. Since the particle size of the swarf 52 is small, if it is used as the filling material as it is without using the bag body 35 as in the conventional case, the sealing effect of the blasting hole 10 may become insufficient, and there may be a risk of the filling material being blown up during blasting and flying stones hitting mining equipment and surrounding houses. In contrast, in this embodiment, since the swarf 52 is put into the bag body 35 and used, even if the swarf 52 with a small particle size is used as the filling material 28, the above problems can be avoided, and blasting can be performed while further reducing the low-frequency sound. Further, since the filling material 28 contains such swarf 52, the cost required for blasting can be reduced. Specifically, the amount of crushed stones used for the filling material 28 can be reduced, and the labor for carrying in and storing the crushed stones can be reduced. The particle size of the swarf 52 used for the filling material 28 may be 30 mm or less, or may be 10 mm or less. The swarf 52 having such a small particle size can be used as the filling material 28. This particle size can be measured, for example, using a caliper. The particle size of the non-spherical swarf 52 is the maximum value among the measured values measured with a caliper.

[0024] The ratio (Lb / L) of the length Lb of the bag body 35 (the portion filled with the filling material) to the total length L of the blasting hole 10 may be 0.01 or more, or may be 0.02 or more. Thereby, the shock wave generated by blasting can be sufficiently suppressed from propagating to the outside from the opening 12 of the blasting hole 10, and the shock wave can be effectively used for crushing. Lb / L may be 0.2 or less, or may be 0.1 or less. Thereby, the bag body 35 can be held sufficiently stably in the blasting hole 10. The total length L and the length Lb are measured along the longitudinal direction of the blasting hole 10.

[0025] Returning to Figure 1, the ratio of the length of the void 26 (void length: L2) to the total length L of the blast hole 10 (L2 / L) may be 0.1 or greater, and may be 0.15 or greater. This allows for a sufficient reduction in low-frequency noise and flying debris during blasting. It also allows for a sufficient reduction in the amount of explosive used. Furthermore, it allows for a sufficiently small particle size and reduced variation of the crushed stone after blasting. L2 / L may be 0.4 or less, and may be 0.3 or less. This helps to suppress a decrease in blasting efficiency. The void length L2 is measured along the longitudinal direction of the blast hole 10.

[0026] The ratio (L3 / L) of the loading length of the material 28 (material length: L3) to the total length L of the blast hole 10 may be 0.15 or more, 0.2 or more, or 0.25 or more. This sufficiently suppresses the propagation of the shock wave generated by the blast from the opening 12 of the blast hole 10 to the outside, and allows the shock wave to be used sufficiently effectively for crushing. L3 / L may be 0.45 or less, or 0.4 or less. This suppresses a decrease in blasting efficiency and reduces the time required for blasting preparation. The material length L3 is measured along the longitudinal direction of the blast hole 10.

[0027] The ratio of the void length L2 to the length from the bottom of the blast hole 10 to the top of the additional die 24 (charge length: L1) (L2 / L1) may be 0.2 to 0.6, or 0.3 to 0.55. This allows for a significant reduction in the amount of explosive used and a sufficiently high blasting efficiency. It also significantly reduces low-frequency noise and flying debris during blasting. Furthermore, it allows for a sufficiently small and consistent particle size distribution of the crushed stone after blasting. The charge length L1 is measured along the longitudinal direction of the blast hole 10.

[0028] As shown in Figure 1, once the blast hole 10 is completed with the detonator 20, main die 22, auxiliary die 24, and filler material 28 installed in that order from the bottom, blasting is performed. The detonator 20 and the blaster 30 installed on the ground surface 42 are connected by a leg line (not shown). Multiple blast holes 10 as shown in Figure 1 may be prepared and blasting may be performed simultaneously or sequentially using multiple blast holes 10. When power is supplied from the blaster 30 installed in each blast hole 10, the detonator 20 ignites and detonates, which detonates the main die 22. The detonation of the main die 22 detonates the auxiliary die 24, which then blasts the bedrock 40, completing the blasting.

[0029] In the blasting method using the blast hole 10 of this embodiment, a portion of the filler material 28a of the filler material 28 is filled into the bag body 35 and fixed inside the blast hole 10 into which the detonator 20, main die 22, and extension die 24 are loaded. Because a portion of the filler material 28 (filler material 28a) is filled into the bag body 35, it is as if the blast hole 10 is capped with a large rock. The inner wall surface 10A of the blast hole 10 and the bag body 35 are interlocked by the filler material 28b on the outside of the bag body 35. As a result, the bag body 35 is firmly fixed inside the blast hole 10. Therefore, the propagation of the shock wave generated by the blast from the opening 12 of the blast hole 10 to the outside is sufficiently suppressed, and the shock wave can be used effectively for crushing. As a result, the low-frequency noise generated during blasting is sufficiently reduced, improving the working environment and sufficiently reducing noise to houses and other buildings around the mine. Furthermore, it becomes possible to utilize explosives more effectively, reducing the amount of explosive used per unit and thus lowering costs. In addition, the amount of flying debris during blasting can be reduced, improving safety.

[0030] A method for producing limestone according to one embodiment includes the steps of collecting raw limestone by performing the blasting method described above at a limestone mine, and then producing limestone by adjusting the particle size of the raw limestone. Particle size adjustment may be performed by crushing the raw stone with a crusher and then using a screen. This makes it possible to obtain limestone with sufficiently small and uniform particle sizes. Applications of the limestone obtained in this way include raw material for quicklime (uses: building materials, papermaking, heating agent, desiccant, etc.), raw material for slaked lime (for agricultural use, etc.), and raw material for cement. The particle size of limestone for cement raw material may be, for example, 30 mm or less. The particle size of limestone for quicklime and slaked lime may be, for example, 100 mm or less. These particle sizes can also be measured using, for example, calipers.

[0031] The above blasting method and limestone manufacturing method effectively utilize shock waves for crushing, allowing for the production of limestone at a low cost. Furthermore, it is possible to obtain limestone with small and uniform particle size. If such limestone is used, for example, as a cement raw material, the load on various crushing machines, such as raw material mills, is reduced, enabling efficient cement production.

[0032] Although one embodiment of the present invention has been described above, the present invention is not limited in any way to the above embodiment. For example, in the above embodiment, an air deck blast is provided with a void portion 26, but the invention is not limited thereto, and a single-charge blast or deck-charge blast without a void portion may also be used. Also, in the above embodiment, the upper end 35A of the bag body 35 was tied to the support 50, but this is not necessarily required. It is not necessary to pull the upper end of the bag body 35 out to the outside of the blast hole 10, and the entire bag body 35 may be fixed inside the blast hole 10 so that it is embedded inside the blast hole 10. Even with such a structure, the bag body 35 is stably fixed inside the blast hole 10 by the frictional force with the inner wall surface 10A of the blast hole 10.

[0033] This disclosure includes, for example, the following: [1] A blasting method comprising: a loading step of loading a main die and an additional die onto a detonator installed at the bottom of a blast hole, and then filling the blast hole with filler material; and a blasting step of performing blasting in the blast hole, A blasting method comprising the loading step of fixing at least a portion of the material inside the blast hole while it is filled into a bag. [2] The blasting method according to [1], wherein in the loading step, the bag body is fixed inside the blast hole such that a gap is provided between the additional die and the bag body. [3] The blasting method according to [2], wherein the ratio of the length of the void to the length from the bottom surface of the blast hole to the top surface of the additional die is 0.2 to 0.6. [4] In the loading step, after loading the additional die into the blast hole, a tubular empty bag is inserted, and the filler is filled into the empty bag from the opening at the upper end of the empty bag to obtain the bag body fixed inside the blast hole, as described in any one of [1] to [3]. [5] The blasting method according to any one of [1] to [3], wherein in the loading step, the upper end of the bag is fixed to a support placed outside the blast hole. [6] The blasting method according to any one of [1] to [5], wherein in the loading step, a portion of the material is filled between the bag and the inner wall surface of the blast hole. [7] The blasting method according to any one of [1] to [6], wherein the mass ratio of the material filled in the bag to the total material is 0.1 to 0.5. [8] The blasting method according to any one of [1] to [7], wherein the material includes milling powder. [9] A blasting method according to any one of [1] to [8], comprising a blast hole formation step of forming the blast hole in the bedrock of a limestone mine, wherein blasting is performed in the blasting step to obtain limestone raw material.

[10] A method for producing limestone for cement raw materials, comprising a step of adjusting the particle size of limestone raw material obtained by carrying out any one of the blasting methods described in [1] to [9] above at a limestone mine. [Examples]

[0034] The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0035] Multiple blasting experiments were conducted with varying conditions for blasting method, total amount of explosive, etc. For air deck blasting, experiments were conducted by changing the explosive length L1, void length L2, and material length L3. Based on these, blasting efficiency (total amount of explosive / amount of ore), working time, the occurrence rate of low-frequency noise above a predetermined volume during blasting, the presence or absence of damage to the lead wires, and the ease of recovery of the lead wires were evaluated. The specific procedures and evaluation methods were as follows.

[0036] The following materials were used in each example and comparative example. Detonator: ORICA brand, product name: UT600 Main die (cast booster): Made by ORICA, product name: Yinguang Booster Ammonium nitrate (ANFO explosive): Manufactured at a cement factory's explosives manufacturing plant by spraying diesel fuel onto ammonium nitrate. Polyethylene tube (thickness: 0.09~0.11mm, folded diameter: 150mm): Manufactured by Ishikawa Co., Ltd., Product name: PE paper tube

[0037] (Example 1: Air deck blasting) In a limestone mine, six blast holes with a diameter of 95 mm were drilled at equal intervals of 4.0 m between them, at a point in the rock face with a face height H: 11.0 m and resistance R: 3.8 m. A hydraulic crawler drill was used to drill the blast holes. The total length L of each blast hole was as shown in Table 1. The six blast holes were drilled in a straight line. The blasting dust generated during drilling was left to settle near the blast holes. A detonator with a lead wire attached was placed on the bottom surface of the blast hole. The upper end of the lead wire was connected to an blaster installed on the outside (ground surface) of the blast hole opening. A main die was loaded to cover the detonator, and an additional die was loaded above the main die. The additional die was loaded so that the charge length L1 from the bottom surface of the blast hole to the top surface of the additional die was 6.1 m.

[0038] Next, one end of a polyethylene tube (poly tube) was tied in a knot, and the poly tube was inserted into the blast hole with that end facing downwards. A filler rod was inserted from the other end (upper end) of the poly tube, and the insertion depth into the blast hole was adjusted so that the length from the knot at the lower end of the poly tube to the ground surface (filler length L3) was 3.8 m. 8 kg of blasting powder (particle size: 10 mm or less) was introduced as filler through the opening at the upper end of the poly tube, filling the poly tube with blasting powder.

[0039] The opening at the top of the poly tube was closed by twisting the top while removing the air from the unfilled portion (top) of the poly tube. The top of the poly tube was wrapped around a sandbag placed outside the blast hole and secured. In this way, the bag was installed inside the blast hole. Then, approximately 24 kg of the same amount of powder as that filled in the poly tube was introduced into the blast hole and filled onto the bag. This filled the outside of the bag as well. Specifically, powder was filled between the side of the powder-filled portion of the bag and the inner wall of the blast hole, and between the top of the powder-filled portion of the bag and the opening of the blast hole (ground surface).

[0040] The mass ratio of the material filled in the bag to the total material (the sum of the material filled in the bag and the material filled outside the bag) was approximately 0.3. The distance between the lower end of the bag fixed inside the blast hole and the upper surface of the additional die, i.e., the length of the void along the longitudinal direction of the blast hole (void length L2), was 2.9 m. There was no tension on the upper part of the bag that was wrapped around and fixed to the sandbag, and the bag itself was firmly fixed by frictional force with the inner wall surface of the blast hole.

[0041] The time required from the start of loading the main die into the blast hole to filling the blast hole opening (ground level) with blasting powder and securing the upper end of the poly tube to the sandbag was measured as the working time per hole. The measurement results are shown in Table 2. Subsequently, six blast holes were simultaneously blasted using a blaster. The total amount of explosives (main die + additional die) for the six blast holes, the amount of ore crushed by the blasting (amount of limestone), the amount of ore per blast hole, and the total amount of explosives per amount of ore are shown in Table 2.

[0042] The generation of low-frequency sound exceeding a predetermined level during blasting was evaluated as follows: A low-frequency sound meter (manufactured by Rion Co., Ltd., product name: Precision Sound Level Meter NL-62) was placed 900m away from the two central blast holes (outside a private house) out of six blast holes, and the volume of low-frequency sound (below 100Hz) was measured. If the volume of low-frequency sound (below 100Hz) during blasting was 85dB or higher, it was evaluated as "present"; if it was less than 85dB, it was evaluated as "absent". The results are shown in Table 2.

[0043] If the visual inspection before blasting showed no damage to the lead wire connecting the detonator and the blaster, and the blasting proceeded as planned, the lead wire connecting the detonator and the blaster was evaluated as "no damage." On the other hand, if the visual inspection before blasting showed damage to the lead wire connecting the detonator and the blaster, or if the blaster did not blast even after being activated, the lead wire was evaluated as "damaged." The evaluation results are shown in Table 2.

[0044] If the blast wires could be recovered quickly and smoothly after the blasting, the result was rated "A," and if it took a long time to recover the wires, the result was rated "B." The evaluation results are shown in Table 2.

[0045] (Examples 2-5: Air deck blasting) Air deck blasting was performed in the same manner as in Example 1, except that at least one of the following was changed as shown in Table 1: face height H of the limestone mine, number of holes, total length L of the blast hole, explosive length L1, void length L2, and filler length L3. The evaluation results are shown in Table 2.

[0046] (Comparative Example 1: Single-charge blasting) A blast hole with a diameter of 95 mm was excavated using a hydraulic crawler drill at a point in the bedrock of a limestone mine with a face height of H5.0 m and resistance R2.6 m. The total length L of the blast hole was as shown in Table 1. A detonator with a connecting wire was placed on the bottom surface of the blast hole. The upper end of the wire was connected to an blaster installed on the outside (ground surface) of the blast hole opening. A main die was loaded to cover the detonator placed on the bottom surface of the blast hole, and an additional die was loaded above the main die. The additional die was loaded so that the charge length L1 from the bottom surface of the blast hole to the top surface of the additional die was 3.4 m. The total amount of explosive (main die + additional die) in the blast hole was as shown in Table 2.

[0047] Next, without leaving any voids, powder was introduced as a filler material onto the additional die and filled up to the opening of the blast hole (ground level). The filler length L3 was as shown in Table 1. Using the blast hole obtained in this way, blasting was performed in the same manner as in Example 1, and each evaluation was performed in the same manner as in Example 1. The evaluation results are as shown in Table 2.

[0048] (Comparative Example 2: Deck Charge Blasting) A blast hole with a diameter of 95 mm was excavated using a hydraulic crawler drill at a point in the bedrock of a limestone mine with a face height of H8.0 m and resistance R2.8 m. The overall length L of the blast hole was as shown in Table 1. A detonator with attached wires was placed on the bottom surface of the blast hole. The upper end of the wires was connected to an blaster installed on the outside (ground surface) of the opening of the blast hole. A main die was loaded to cover the detonator installed on the bottom surface of the blast hole, and an additional die was loaded above the main die.

[0049] Next, without leaving any voids, aggregate was introduced and filled as filler material on top of the additional die up to the opening of the blast hole (ground level). On top of the filled filler material, the additional die and filler material were filled without leaving any voids. In this way, the detonator, main die, additional die, filler material, additional die, and filler material were arranged in the blast hole in this order. The end of the work time was defined as the completion of filling the second layer of filler material. Table 1 shows the total length of the detonator and the main die and main die (two layers each) as the charge length L1, and the total length of the filler material (two layers) as the filler material length L3. The same aggregate material used in Comparative Example 1 was used as the filler material. Using the blast hole obtained in this way, blasting was performed in the same manner as in Example 1, and each evaluation was performed in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0050] [Table 1]

[0051] [Table 2]

[0052] As shown in Tables 1 and 2, the total amount of explosive / amount of ore was smaller in the examples than in the comparative examples, resulting in a lower explosive unit consumption. In all examples, no blow-up occurred during blasting, and it was confirmed that sufficient sealing effect was obtained by the bag. As a result, the volume of low-frequency sound was less than 85 dB in all examples. Even when each example was blasted multiple times, no low-frequency sound above 85 dB was detected. On the other hand, in Comparative Examples 1 and 2, low-frequency sound above 85 dB was detected. The probability of low-frequency sound above 85 dB occurring was determined by blasting Comparative Examples 1 and 2 multiple times. As a result, low-frequency sound above 85 dB occurred with a probability of 24% in Comparative Example 1 and 42% in Comparative Example 2.

[0053] These results confirmed that in each embodiment, the blasting method suppressed the propagation of shock waves generated by the blasting outward from the blast hole opening, and that the shock waves were effectively utilized for crushing. Furthermore, in all embodiments, there was no damage to the detonator's lead wires that would render blasting impossible, and the lead wires could be smoothly recovered after blasting. In addition, no large chunks were generated during the blasting process in each embodiment, and limestone useful for various applications was produced. In each embodiment, the process of filling poly tubes with the crushed limestone was carried out, and the working time was kept sufficiently short. [Industrial applicability]

[0054] This invention provides a blasting method that can reduce low-frequency noise generated during blasting, and a method for producing limestone. [Explanation of Symbols]

[0055] 10...Blasting hole, 10A...Inner wall surface, 12...Opening, 20...Detonator, 22...Main die, 24...Additional die, 26...Void, 28,28a,28b...Filling material, 30...Blaster, 35...Bag body, 35A...Upper end, 40...Rock mass, 41...Face surface, 42...Ground surface, 50...Support, 52...Powder.

Claims

1. A blasting method comprising: a loading step of loading a main die and an additional die onto a detonator installed at the bottom of a blast hole, and then filling the blast hole with filler material; and a blasting step of performing blasting in the blast hole, A blasting method comprising the loading step of fixing a portion of the material inside the blast hole while it is filled into a bag, and filling the remaining portion of the material between the bag and the inner wall surface of the blast hole.

2. A blasting method comprising: a loading step of loading a master die and an additional die onto a detonator installed at the bottom of a blast hole, and then filling the blast hole with filler material; and a blasting step of performing blasting in the blast hole, In the loading process, at least a portion of the material is filled into the bag and fixed inside the blast hole. A blasting method in which the mass ratio of the material filled in the bag to the total amount of the material is 0.1 to 0.

5.

3. The blasting method according to claim 2, wherein in the loading step, a portion of the material is filled into the bag and fixed inside the blast hole, and the remaining portion of the material is filled between the bag and the inner wall surface of the blast hole.

4. The blasting method according to any one of claims 1 to 3, wherein in the loading step, the bag is fixed inside the blast hole such that a gap is provided between the additional die and the bag.

5. The blasting method according to claim 4, wherein the ratio of the length of the void to the length from the bottom surface of the blast hole to the top surface of the increasing die is 0.2 to 0.

6.

6. The blasting method according to any one of claims 1 to 3, wherein in the loading step, after loading the additional die into the blast hole, a tubular empty bag is inserted, and the filler is filled into the empty bag from the opening at the upper end of the empty bag to obtain the bag body fixed inside the blast hole.

7. The blasting method according to claim 6, wherein in the loading step, the upper end of the bag is fixed to a support placed outside the blast hole.

8. The blasting method according to any one of claims 1 to 3, wherein the aforementioned material includes milling powder.

9. The process includes a blast hole formation step in which the aforementioned blast holes are formed in the bedrock of a limestone mine. The blasting method according to any one of claims 1 to 3, wherein blasting is performed in the blasting step to obtain limestone raw material.

10. A method for producing limestone, comprising a step of adjusting the particle size of raw limestone obtained by carrying out the blasting method described in any one of claims 1 to 3 at a limestone mine.

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