A multi-wire detonating cord parallel charging structure for pre-splitting blasting and a construction method thereof

Abstract

The application discloses a multi-wire detonating cord parallel charging structure for pre-splitting blasting, which solves the problem that small-diameter cartridges cannot meet the on-site construction requirements due to various factors and cannot well realize pre-splitting blasting. The structure comprises a pre-splitting hole, a reinforced cartridge arranged at the bottom of the pre-splitting hole, and a detonating cord set connected with the reinforced cartridge. The upper end of the detonating cord set penetrates through the pre-splitting hole and is arranged above the pre-splitting hole. The length of the connection section of the pre-splitting hole bottom and the reinforced cartridge, i.e. the length of the reinforced charging section, is L2, the length of the normal charging section in the hole is L3, the length of the weakened section at the hole mouth is L4, the length of the blocking section is L5, and the length of the reserved section outside the hole is L6.

Description

Technical Field

[0001] This invention relates to the field of blasting construction technology, and in particular to a charging structure and construction method for multi-strand detonating cords connected in parallel for pre-splitting blasting. Background Technology

[0002] Pre-splitting blasting is a technique in which dense holes are drilled along the designed excavation outline during the blasting excavation process, and a small amount of explosives are loaded to pre-blast and create fractures, in order to prevent the blasting of the boreholes in the blasting zone from causing damage to the remaining rock mass or other buildings outside the blasting zone.

[0003] In my country, small-diameter explosive cartridges, typically 25mm, 32mm, or 35mm, are commonly used for charging pre-splitting blasting holes. These cartridges are tied to bamboo strips at regular intervals or continuously, and connected by detonating cords. The prepared explosive strings are then placed into the holes, and detonating cords are used to connect multiple holes for simultaneous detonation. This technology is very mature and achieves excellent blasting results.

[0004] However, for some overseas projects, this technology cannot be well applied due to factors such as immature manufacturing technology of small-diameter explosive cartridges, insufficient supply, poor blasting effect, or problems with the results. Summary of the Invention

[0005] In view of the above situation and to overcome the defects of the prior art, the present invention provides a charging structure with multiple detonating cords connected in parallel for pre-splitting blasting, which effectively solves the problem that small-diameter explosive cartridges cannot meet the needs of on-site construction and cannot achieve pre-splitting blasting well due to various factors.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: a charging structure for a multi-strand detonating cord used in pre-splitting blasting, comprising a pre-splitting hole, a reinforcing charge being provided at the bottom of the pre-splitting hole, a detonating cord assembly being connected to the reinforcing charge, and the upper end of the detonating cord assembly penetrating the pre-splitting hole and positioned above the pre-splitting hole;

[0007] The length of the connection section between the bottom of the pre-cracked hole and the reinforced charge, i.e., the length of the reinforced charge section, is L2; ​​the length of the normal charge section inside the hole is L3; the length of the weakened section at the hole opening is L4; the length of the blocking section is L5; and the length reserved outside the hole is L6.

[0008] Preferably, when the rock mass integrity is between 90-100 and joints are not well developed, the number of detonating cord bundles in the normal charging section of the pre-splitting hole, i.e., section L3, is seven; the number of detonating cord bundles in the weakening section at the pre-splitting hole opening, i.e., section L4, is three; the number of detonating cord bundles in the blocking section at the top of the pre-splitting hole, i.e., section L5, is one, and is led out of the hole opening; the number of detonating cord bundles in the reinforcing section at the bottom of the pre-splitting hole, i.e., section L2, is 1.2 Φ50mm explosive cartridges, which are connected by a single detonating cord bundle, and the end of the detonating cord bundle is inserted into the explosive cartridge to a depth of not less than 10cm.

[0009] Preferably, when the rock mass integrity is between 50-90 and the joints are relatively developed, the number of detonating cord bundles in the normal charging section of the fracture hole, i.e., section L3, is six; the number of detonating cord bundles in the weakening section at the pre-splitting hole opening, i.e., section L4, is three; the number of detonating cord bundles in the blocking section at the top of the pre-splitting hole, i.e., section L5, is one bundle and leads out of the hole opening; and the number of detonating cord bundles in the reinforcing section at the bottom of the pre-splitting hole, i.e., section L2, is one Φ50mm explosive cartridge, which is connected by a detonating cord bundle. The end of the detonating cord bundle is inserted into the explosive cartridge to a depth of not less than 10cm.

[0010] Preferably, when the rock mass integrity is between 25-50 and joints are developed or very developed, the number of detonating cord bundles in the normal charging section of the fracture hole, i.e., section L3, is five bundles; the number of detonating cord bundles in the weakening section at the pre-splitting hole opening, i.e., section L4, is two bundles; the number of detonating cord bundles in the blocking section at the top of the pre-splitting hole, i.e., section L5, is one bundle and leads out of the hole opening; and the number of detonating cord bundles in the reinforcing section at the bottom of the pre-splitting hole, i.e., section L2, is one Φ50mm explosive cartridge and is connected by one detonating cord bundle. The end of the detonating cord bundle is inserted into the explosive cartridge to a depth of not less than 10cm.

[0011] Preferably, the detonating cord bundles are formed into detonating cord clusters, and the detonating cord clusters are bound together at certain intervals with blasting tape to form detonating cord binding knots.

[0012] Preferably, the reinforcing explosive charge is provided with a central ring for the bottom detonating cord above the hole, the detonating cord passes through the bottom hole and the top hole of the central ring for the bottom detonating cord, and the central ring for the bottom detonating cord is filled with sealing sand.

[0013] Preferably, the blocking section is provided with a central ring for the detonating cord at the top of the borehole, and the detonating cord bundle passes vertically through the central ring for the detonating cord at the top of the borehole.

[0014] Preferably, the lower end of the blocking section is provided with a flexible seal, and the upper part of the flexible seal is provided with a blocking body.

[0015] Preferably, the flexible seal is made of a packaging bag or a woven bag.

[0016] Preferably, the blockage is one or more of rock chips, sand, or gravel.

[0017] The construction method using a charge structure includes the following steps:

[0018] Step 1: Drilling pre-splitting holes. Based on the rock mass characteristics and design drawings, determine the relevant drilling parameters and use a high-pressure air drilling rig to drill the holes. After drilling is completed, clean the rock cuttings in the holes and temporarily seal the hole openings.

[0019] Step 2: Pre-cracked holes are then filled with explosives;

[0020] Step 3: Blocking; the blocked section is blocked using a blocking device.

[0021] Step 4: Connect the external network. Use detonating cords to connect all the reserved lengths of L6 detonating cords in series outside the borehole. If there is a maximum single-shot charge requirement, use millisecond delay detonating tubes to segment the middle.

[0022] Step 5: Detonation.

[0023] Preferably, the specific steps of step two are as follows:

[0024] Before loading the explosive, the depth of each hole is measured. The first bundle of detonating cord, with a length of L1, is cut according to the measured depth and used as the detonating cord for the blasting inside the pre-splitting hole. This bundle of detonating cord extends throughout the entire pre-splitting hole, entering from the hole opening and connecting with the reinforcing charge at the bottom of the hole. The lengths from the bottom to the top of the pre-splitting hole are as follows: the length of the connection section between the bottom of the pre-splitting hole and the reinforcing charge (i.e., the length of the reinforcing charge section) is L2; ​​the length of the normal charge section inside the hole is L3; the length of the weakening section at the hole opening is L4; the length of the plugging section is L5; and the length reserved outside the hole is L6. Where L1 = L2 + L3 + L4 + L5 + L6.

[0025] When the rock mass integrity is between 90-100 and the joints are not well developed, it is identified by characteristic a; when the rock mass integrity is between 50-90 and the joints are relatively well developed, it is identified by characteristic b; when the rock mass integrity is between 25-50 and the joints are developed or very developed, it is identified by characteristic c.

[0026] Cut the X-beam detonating cord to a length of L7, where L7 = L3 + L4. According to the rock characteristics, X is 2 when it is characteristic a, X is 2 when it is characteristic b, and X is 1 when it is characteristic c.

[0027] A section of Y-shaped detonating cord is cut, with a length of L8, where L8 = L3. According to the rock characteristics, Y is 4 when characteristic a is present, Y is 3 when characteristic b is present, and Y is 3 when characteristic c is present.

[0028] For the reinforced charge section, which is used to connect with the reinforced charge package, only a single bundle of detonating agent is required for connection.

[0029] The detonating cords inside the borehole are connected in parallel, with each length numbered and aligned, and tied together with blasting tape at 0.5m intervals.

[0030] After the detonating cord is tied, install the centering rings of the detonating cord at the bottom of the hole and the centering rings of the detonating cord at the top of the hole. The first bundle of detonating cord is put into the centering rings. Then, the bottle mouth is tied securely with blasting tape, with the bottle mouth facing downwards.

[0031] Slowly lower the tied detonating cord string into the hole. Before the centering ring at the hole opening is lowered, wrap the flexible seal around the bottom of the centering ring, and then slowly lower it into the hole along with the centering ring. A jackhammer can be used to assist in proper guidance. Stop lowering when the length of the detonating cord outside the pre-splitting hole just reaches the reserved length L6.

[0032] Compared with existing technologies, the present invention has the following advantages: 1) The pre-loaded hole charging structure is simpler, the on-site operation is more convenient, the construction speed is faster, and the same blasting effect can be achieved; 2) There are basically no cases of missed explosions or duds, avoiding secondary dud treatment and reducing operational risks; 3) For some foreign countries or projects where the manufacturing process of small-diameter explosive cartridges is not mature, the supply is insufficient, or the blasting effect is not good, this technology can be well applied and the effect is good. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the present invention;

[0034] In the diagram: 1. Pre-splitting hole; 2. Reinforcing charge; 3. Detonating cord bundle; 4. Detonating cord binding knot; 5. Bottom ring of detonating cord; 6. Bottom hole of the bottom ring of detonating cord; 7. Top hole of the bottom ring of detonating cord; 8. Sealing sand; 9. Top ring of detonating cord; 10. Flexible sealing element; 11. Plugging body. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to the accompanying drawings. The drawings are simplified schematic diagrams, illustrating only the basic structure of the invention in a schematic manner, and therefore only show the components relevant to the invention.

[0036] Using the specific construction process of the Basha Dam project in Pakistan as an example, a multi-strand detonating cord parallel charging structure for pre-splitting blasting is described. Its main structural components include: 1. pre-splitting hole, 2. reinforcing charge, 3. detonating cord bundle, 4. detonating cord binding knot, 5. bottom hole central ring of the detonating cord, 6. bottom hole of the bottom hole central ring of the detonating cord, 7. top hole of the bottom hole central ring of the detonating cord, 8. sealing sand, 9. top hole central ring of the detonating cord, 10. flexible sealing element, and 11. plugging material.

[0037] Correspondingly, the length of the connection section between the bottom of the hole and the emulsion explosive (reinforced charge section) is L2, the length of the normal charge section inside the hole is L3, the length of the weakened section at the hole opening is L4, the length of the plugging section is L5, and the reserved length outside the hole is L6.

[0038] Furthermore, the number of detonating cords in detonating cord set 3 varies depending on the depth of the charge position in the pre-splitting hole 1. Specifically:

[0039] Feature a: When the rock mass integrity (RQD) is between 90-100 and joints are not well developed, the number of detonating cord bundles 3 in the normal charging section (L3 section) of pre-splitting hole 1 is 7 bundles, the number of detonating cord bundles 3 in the weakening section (L4 section) of pre-splitting hole 1 is 3 bundles, the number of detonating cord bundles 3 in the top blocking section (L5 section) of pre-splitting hole 1 is 1 bundle, which is led out of the hole opening, and the bottom reinforcing section (L2 section) of pre-splitting hole 1 is equipped with 1.2 Φ50mm explosive cartridges (the weight of the explosive cartridges is 1.2kg), which are connected by 1 detonating cord, and the end of the detonating cord is inserted into the explosive cartridge to a depth of not less than 10cm.

[0040] Feature b: When the rock mass integrity (RQD) is between 50 and 90 and the joints are relatively developed, the number of detonating cord bundles 3 in the normal charging section (L3 section) of pre-splitting hole 1 is 6 bundles, the number of detonating cord bundles 3 in the weakening section (L4 section) of pre-splitting hole 1 is 3 bundles, the number of detonating cord bundles 3 in the top blocking section (L5 section) of pre-splitting hole 1 is 1 bundle, which is led out of the hole opening, and the bottom reinforcing section (L2 section) of pre-splitting hole 1 is equipped with 1 Φ50mm explosive cartridge (the explosive cartridge weighs 1kg), which is connected by 1 detonating cord, and the end of the detonating cord is inserted into the explosive cartridge to a depth of not less than 10cm.

[0041] Characteristic c: When the rock mass integrity (RQD) is between 25 and 50, and joints are developed or very developed, the number of detonating cord bundles 3 in the normal charging section (L3 section) of pre-splitting hole 1 is 5 bundles, the number of detonating cord bundles 3 in the weakening section (L4 section) of pre-splitting hole 1 is 2 bundles, the number of detonating cord bundles 3 in the top blocking section (L5 section) of pre-splitting hole 1 is 1 bundle, which is led out of the hole opening, and the bottom reinforcing section (L2 section) of pre-splitting hole 1 is equipped with 1.2 Φ50mm explosive cartridges (the weight of the explosive cartridges is 1.2kg), which are connected by 1 detonating cord, and the end of the detonating cord is inserted into the explosive cartridge to a depth of not less than 10cm.

[0042] For all the above characteristic points, the detonating cord bundles are tied with blasting tape every 0.5m to form detonating cord binding knots 4, ensuring the uniformity of the detonating cord bundles and preventing them from becoming scattered, thereby improving the quality of pre-splitting blasting.

[0043] For all the above-mentioned features, detonating cord centering rings are installed at both the bottom and top of the borehole. These rings are made from plastic bottles with a volume of 1.5L and an outer diameter of 85mm, suitable for 92mm and 105mm drilling. The bottom hole 6 (bottle mouth) of the bottom detonating cord centering ring faces the bottom of the borehole. When the detonating cord bundle 3 passes through, it is securely tied with blasting tape. A hole 7 (bottle bottom) is drilled in the top hole of the bottom detonating cord centering ring to ensure the passage of the detonating cord bundle 3, and the bottle is then filled with sand. The bottom detonating cord centering ring 5 is located on the top surface of the explosive charge, and the top detonating cord centering ring 9 is located within the plugging section. The bottom detonating cord centering ring 5 has the same structure and construction as the top detonating cord centering ring, differing only in its installation position. This ensures that the detonating cord bundle is centered after being inserted into the borehole, enhancing the decoupling effect and improving the quality of pre-splitting blasting.

[0044] The diameter of the single-bundle detonating cord is d1=6mm. When operating with features a, b, and c, the diameter of the detonating cord bundle in the normal charging section (L3 section) is d2=18mm, the diameter of the pre-splitting hole 1 is D=92mm, and the radial decoupling coefficient is p=92mm / 18mm=5.11; the diameter of the detonating cord bundle in the orifice weakening section (L4) is d2=12mm, the diameter of the pre-splitting hole 1 is D=92mm, and the radial decoupling coefficient is p=92mm / 12mm=7.67.

[0045] A construction method for a multi-strand detonating cord parallel charge structure used in pre-splitting blasting, the specific operation steps of which are described below:

[0046] Step 1: Drilling pre-splitting hole 1. Determine the relevant drilling parameters based on the rock mass characteristics and design drawings, including the drilling diameter d0=92mm, the designed drilling depth h1=15.3m, and the drilling interval a=0.6m. Use a high-pressure air drilling rig to drill the hole. After drilling, clean the rock cuttings in the hole and temporarily seal the hole opening.

[0047] Step 2: Loading the pre-splitting hole 1. Before loading, measure the depth of each hole. Cut the first bundle of detonating cord (length L1 = 16.4m, based on design specifications) according to the measured depth. This bundle of detonating cord will serve as the detonating cord for the internal blasting of the pre-splitting hole 1. This bundle of detonating cord extends throughout the entire pre-splitting hole 1, entering from the hole opening and connecting with the explosive cartridge at the bottom of the hole. From the bottom to the top of the pre-splitting hole 1, the lengths are as follows: the length of the section connecting the bottom of the hole to the emulsion explosive (reinforced loading section) L2 = 1m (the length of the explosive cartridge is 0.5m, including the length wrapped around the cartridge and inserted into the cartridge, the total length is 1m), the length of the normal loading section inside the hole is L3 = 11.3m, the length of the weakened section at the hole opening is L4 = 2.5m, the length of the plugging section is L5 = 1.0m, and the reserved length outside the hole is L6 = 0.6m.

[0048] Furthermore, the X-beam detonating cord is cut off (according to rock characteristics, X is 2 when it is characteristic a; X is 2 when it is characteristic b; X is 1 when it is characteristic c), with a length of L7, L7=L3+L4=11.3+2.5=13.8m.

[0049] Furthermore, a section of the Y-beam detonating cord was cut (based on rock characteristics, Y is 4 when characteristic a, Y is 3 when characteristic b, and Y is 3 when characteristic c), with a length of L8, where L8 = L3 = 11.3 m.

[0050] Furthermore, the explosive charge of the single-strand detonating cord is 11 g / m. That is, when it is characteristic a, the explosive charge in the normal charge section (L3 section) is 77 g / m and the explosive charge in the weakened section (L4 section) is 33 g / m; when it is characteristic b, the explosive charge in the normal charge section (L3 section) is 66 g / m and the explosive charge in the weakened section (L4 section) is 33 g / m; when it is characteristic c, the explosive charge in the normal charge section (L3 section) is 55 g / m and the explosive charge in the weakened section (L4 section) is 22 g / m.

[0051] Furthermore, the length of the connection section between the bottom of the hole and the emulsion explosive (reinforced charge section) L2 = 1.0m. Here, 1.0m refers to the length of the detonating cord, not the drilling depth. It should be clarified that this is used to connect with the reinforcing charge at the bottom of the hole, and only a single bundle of detonating cord is needed for connection.

[0052] Furthermore, in the three cases of feature a, feature b, and feature c mentioned above, the detonating cords inside the borehole are connected in parallel. Based on the number of detonating cord sets 3 in each feature case, they are aligned according to their length numbers and tied together with blasting tape at 0.5m intervals.

[0053] Furthermore, after the detonating cord is secured, install the centering ring 5 for the bottom detonating cord and the centering ring for the top detonating cord. Both centering rings are fitted onto the first bundle of detonating cord and installed as shown in the image. Figure 1 After positioning, the bottom hole (bottle mouth) of the centering ring of the detonating cord is then securely tied according to the instructions of the blasting worker. Sand is then filled through the top hole, and the ring should be filled with sand more than half full. Other materials can also be used instead. The reason for filling the ring is mainly to ensure the verticality of the centering ring and to ensure that the detonating cord is centered in the pre-splitting hole 1.

[0054] Slowly lower the bundled explosive string into the hole. Before the centering ring at the hole opening is lowered, wrap the flexible sealing element around the bottom of the centering ring. The flexible sealing element can generally be a packaging bag for bulk explosives or other woven bags. After wrapping, slowly lower it into the hole together with the centering ring. You can use a tamping rod to assist in proper tamping. When the length of the detonating cord outside the pre-splitting hole 1 reaches the reserved length L6=0.6m, stop lowering. At this time, the charging process is complete.

[0055] Step 3: Blocking. Conventional materials can be used as the blocking body for the blocking section L5, such as rock chips, sand, and gravel.

[0056] Step 4: Connect the external detonating cords. Connect all the pre-reserved L6 detonating cords in series outside the hole using detonating cords. If there is a maximum single-shot charge requirement, use millisecond delay detonating tubes to divide the section in the middle.

[0057] Step 5: Detonate. A conventional detonation method can be used.

[0058] The working principle of this invention is as follows: It primarily utilizes a bundle of detonating cord as the blasting power source. Taking advantage of its high detonation velocity, under the action of the explosion stress wave and high-pressure gas, it cuts along the pre-splitting line to form a pre-crack of a certain width. The bottom-reinforced explosive cartridge reduces the clamping effect, and the centrally positioned ring of the detonating cord ensures that the detonating cord is centered on the pre-splitting hole 1, enhancing decoupling and improving the quality of pre-splitting blasting. The above values ​​were obtained through field tests and large-scale production, and have certain guiding significance.

[0059] The embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that various variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom remain within the scope of this invention.

Claims

1. A charging structure for pre-splitting blasting using a multi-strand detonating cord connected in parallel, characterized in that, It includes a pre-splitting hole, a reinforcing explosive charge is installed at the bottom of the pre-splitting hole, the reinforcing explosive charge is connected to a detonating cord bundle, and the upper end of the detonating cord bundle passes through the pre-splitting hole and is positioned above the pre-splitting hole; The length of the connection section between the bottom of the pre-cracked hole and the reinforced charge, i.e. the length of the reinforced charge section, is L2; ​​the length of the normal charge section inside the hole is L3; the length of the weakened section at the hole opening is L4; the length of the plugging section is L5; and the length reserved outside the hole is L6. When the rock mass integrity is between 90-100 and joints are not well developed, the number of detonating cord bundles in the normal charging section of the pre-splitting hole, i.e., section L3, is seven; the number of detonating cord bundles in the weakening section at the pre-splitting hole opening, i.e., section L4, is three; the number of detonating cord bundles in the blocking section at the top of the pre-splitting hole, i.e., section L5, is one, and it is led out of the hole opening; the number of detonating cord bundles in the reinforcing section at the bottom of the pre-splitting hole, i.e., section L2, is 1.2 Φ50mm explosive cartridges, which are connected by a single detonating cord bundle. The depth of the detonating cord bundle end inserted into the explosive cartridge is not less than 10cm. When the rock mass integrity is between 50-90 and the joints are relatively developed, the number of detonating cord bundles in the normal charging section of the fracture hole, i.e., section L3, is six; the number of detonating cord bundles in the weakening section at the pre-splitting hole opening, i.e., section L4, is three; the number of detonating cord bundles in the blocking section at the top of the pre-splitting hole, i.e., section L5, is one bundle and leads out of the hole opening; the number of detonating cord bundles in the reinforcing section at the bottom of the pre-splitting hole, i.e., section L2, is one Φ50mm explosive cartridge and is connected by one detonating cord bundle. The end of the detonating cord bundle is inserted into the explosive cartridge to a depth of not less than 10cm. When the rock mass integrity is between 25-50 and joints are well-developed or very well-developed, the number of detonating cord bundles in the normal charging section of the fracture hole, i.e., section L3, is five bundles; the number of detonating cord bundles in the weakening section at the pre-splitting hole opening, i.e., section L4, is two bundles; the number of detonating cord bundles in the top blocking section of the pre-splitting hole, i.e., section L5, is one bundle and leads out of the hole opening; and the number of detonating cord bundles in the bottom reinforcing section of the pre-splitting hole, i.e., section L2, is one Φ50mm explosive cartridge, which is connected by one detonating cord bundle. The end of the detonating cord bundle is inserted into the explosive cartridge to a depth of not less than 10cm.

2. The charging structure for pre-splitting blasting with multiple strands of detonating cord in parallel as described in claim 1, characterized in that, The detonating cords are arranged into detonating cord bundles, and the detonating cord bundles are tied together at regular intervals with blasting tape to form detonating cord binding knots.

3. The charging structure for pre-splitting blasting with multiple strands of detonating cord connected in parallel according to claim 1, characterized in that, The reinforced explosive charge is provided with a central ring for the bottom detonating cord above it. The detonating cord passes through the bottom hole and the top hole of the central ring for the bottom detonating cord, and the central ring for the bottom detonating cord is filled with sealing sand.

4. The charging structure for pre-splitting blasting with multiple strands of detonating cord in parallel as described in claim 1, characterized in that, The blockage section is equipped with a central ring for the detonating cord at the top of the borehole, and the detonating cord bundle passes vertically through the central ring for the detonating cord at the top of the borehole.

5. The charging structure for pre-splitting blasting with multiple strands of detonating cord in parallel as described in claim 1, characterized in that, The lower end of the blocking section is provided with a flexible seal, and the upper part of the flexible seal is provided with a blocking body.

6. A construction method using the charge structure of claim 5, comprising the following steps: Step 1: Drilling pre-splitting holes. Based on the rock mass characteristics and design drawings, determine the relevant drilling parameters and use a high-pressure air drilling rig to drill the holes. After drilling is completed, clean the rock cuttings in the holes and temporarily seal the hole openings. Step 2: Pre-cracked holes are filled with explosives; Step 3: Blocking; the blocked section is blocked using a blocking device. Step 4: Connect the external network. Use detonating cords to connect all the reserved lengths of L6 detonating cords in series outside the borehole. If there is a maximum single-shot charge requirement, use millisecond delay detonating tubes to segment the middle. Step 5: Detonation.

7. The construction method according to claim 6, characterized in that, The specific steps of step two are as follows: Before loading the explosive, the depth of each hole is measured. The first bundle of detonating cord, with a length of L1, is cut according to the measured depth and used as the detonating cord for the blasting inside the pre-splitting hole. This bundle of detonating cord extends throughout the entire pre-splitting hole, entering from the hole opening and connecting with the reinforcing charge at the bottom of the hole. The lengths from the bottom to the top of the pre-splitting hole are as follows: the length of the connection section between the bottom of the pre-splitting hole and the reinforcing charge (i.e., the length of the reinforcing charge section) is L2; ​​the length of the normal charge section inside the hole is L3; the length of the weakening section at the hole opening is L4; the length of the plugging section is L5; and the length reserved outside the hole is L6. Where L1 = L2 + L3 + L4 + L5 + L6. When the rock mass integrity is between 90-100 and the joints are not well developed, it is identified by characteristic a; when the rock mass integrity is between 50-90 and the joints are relatively well developed, it is identified by characteristic b; when the rock mass integrity is between 25-50 and the joints are developed or very developed, it is identified by characteristic c. Cut the X-beam detonating cord to a length of L7, where L7 = L3 + L4. According to the rock characteristics, X is 2 when it is characteristic a, X is 2 when it is characteristic b, and X is 1 when it is characteristic c. A section of Y-shaped detonating cord is cut, with a length of L8, where L8 = L3. According to the rock characteristics, Y is 4 when characteristic a is present, Y is 3 when characteristic b is present, and Y is 3 when characteristic c is present. For the reinforced charge section, which is used to connect with the reinforced charge package, only a single bundle of detonating agent is required for connection. The detonating cords inside the borehole are connected in parallel, with each length numbered and aligned, and tied together with blasting tape at 0.5m intervals. After the detonating cord is tied, install the centering rings of the detonating cord at the bottom of the hole and the centering rings of the detonating cord at the top of the hole. The first bundle of detonating cord is put into the centering rings. Then, the bottle mouth is tied securely with blasting tape, with the bottle mouth facing downwards. Slowly lower the tied detonating cord string into the hole. Before the centering ring at the hole opening is lowered, wrap the flexible seal around the bottom of the centering ring, and then slowly lower it into the hole together with the centering ring. A jackhammer can be used to assist in proper guidance. Stop lowering when the length of the detonating cord outside the pre-splitting hole just reaches the reserved length L6.

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