A centering charge double-layered cutting pipe device and construction method suitable for roadway engineering

Abstract

The present application relates to the field of blasting technology, especially to a center-loading double-layered cutting seam pipe device and construction method suitable for roadway engineering. The device comprises an energy-gathering cutting seam pipe body, a positioning meniscus and a grooved cork. The device can be made and constructed on site, and is easy to operate. The compression of the rigid spring is conducive to the loading of the double-layered cutting seam pipe device into the blast hole. When the cutting seam pipe reaches the appropriate position, the rebound of the rigid spring fixes the double-layered cutting seam pipe device at the center position of the blast hole, preventing eccentricity. By selecting PVC pipes of different diameters to make the energy-gathering cutting seam pipe body and selecting rigid springs of different lengths, the center-loading double-layered cutting seam pipe device can be applied to blast holes of different diameters. The energy-gathering cutting seam pipe body is provided with an energy-gathering cutting seam. Directional fracture controlled blasting promotes the crack propagation in the direction of the energy-gathering cutting seam and inhibits the crack propagation in the direction of the non-energy-gathering cutting seam, so that directional cracks are formed in the direction of the blast hole line, reducing the damage to the surrounding rock.

Description

Technical Field

[0001] This invention relates to the field of blasting technology, and in particular to a centrally loaded double-layer slotted tube device and construction method suitable for tunnel engineering. Background Technology

[0002] Currently, the main method for tunnel excavation is drill-and-blast. Due to its wide applicability, relatively low cost, and high efficiency, drill-and-blast is widely used in rock tunnel excavation and underground space engineering construction. Drilling and blasting remain the primary means of rock breaking during excavation. In addition to breaking and fracturing the rock, the stability of the remaining rock mass must be ensured during drill-and-blasting. This involves minimizing the disturbance of the remaining rock mass caused by the explosive blast, reducing under-excavation and over-excavation of the excavation profile, and ultimately achieving a smooth and flat excavation profile.

[0003] To reduce over- and under-excavation of the remaining rock mass, directional fracture control blasting, developed from pre-splitting blasting and smooth blasting, can effectively address over- and under-excavation of the tunnel profile. Directional fracture control blasting promotes crack propagation along the shaped charge direction and inhibits the propagation of blast-induced cracks along the non-shaped charge direction, thereby creating directional cracks along the borehole alignment and reducing damage to the surrounding rock.

[0004] However, existing contour-controlled blasting methods all employ decoupled charge structures. Under gravity, the explosive cartridge and shaped charge slotted tube adhere tightly to one side of the borehole, and the center of the explosive cartridge does not coincide with the central axis of the borehole. This results in uneven energy distribution of the explosive on the borehole wall, altering the designed blasting effect, causing excessive damage to the rock mass in the reserved area, affecting rock mass stability, and even leading to over- or under-excavation. Therefore, to address the problem in this type of directional fracture-controlled blasting method where the gap between the slotted tube and the borehole causes the slotted tube to be in an off-center position, this invention provides a centrally charged double-layered slotted tube device and construction method suitable for roadway engineering. This aims to ensure the explosive cartridge is placed centrally, protect the rock mass in the non-shaped charge direction, and effectively improve the surrounding formation quality of coal mine rock roadways. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a centrally loaded double-layer slotted tube device and construction method suitable for tunnel engineering. The technical solution adopted is as follows:

[0006] A double-layer slotted tube device for centrally loaded explosive charge suitable for tunnel engineering, comprising a shaped charge slotted tube body, two positioning menisci, and a grooved cork stopper;

[0007] The positioning meniscus consists of two pieces, which together form a tube with a gap in the middle, wrapped around the outside of the energy-concentrating cut tube. The diameter of the tube formed by the two positioning meniscus is larger than the diameter of the energy-concentrating cut tube.

[0008] Each positioning meniscus is provided with at least three pre-made holes, respectively on its left, middle and right sides. The corresponding positions of the energy-concentrating cutting tube are provided with the same pre-made holes. A rigid spring with a diameter larger than the pre-made hole is set between the energy-concentrating cutting tube and the positioning meniscus. A round-headed rivet passes through the positioning meniscus, the rigid spring and the energy-concentrating cutting tube and connects the three.

[0009] The energy-concentrating slit tube body is cut at a 180° angle on both sides of the right port, and the position of the energy-concentrating slit corresponds to the position of the gap left by the two positioning menisci.

[0010] The grooved cork is installed at the left end of the energy-concentrating slit tube, and a pre-reserved groove is provided on the side edge of the grooved cork.

[0011] Preferably, both the energy-concentrating slit tube and the positioning meniscus are made of PVC; the diameter of the positioning meniscus is 10-15 mm larger than the diameter of the energy-concentrating slit tube.

[0012] Preferably, the width of the energy-concentrating slit is 2-4 mm, and its leftmost distance from the left port of the energy-concentrating slit tube is 200-300 mm.

[0013] Preferably, the width of the energy-concentrating cut is less than the width of the gap left between the two positioning menisci.

[0014] Preferably, each of the positioning menisci has nine pre-fabricated holes evenly and symmetrically arranged, forming three rings on its left, middle and right sides respectively; the energy-concentrating slit tube body has pre-fabricated holes at corresponding positions, for a total of 18 holes.

[0015] Preferably, the diameter of the circular cap at the top of the round-head rivet is larger than the diameter of the pre-drilled hole, the diameter of the rivet body matches the diameter of the pre-drilled hole, and the length of the rivet body is greater than the sum of the thicknesses of the positioning meniscus, the rigid spring, and the energy-concentrating cutting tube. When selecting round-head rivets, not only must the length meet the requirements, but it must also be ensured that the end of the rivet body does not detach from the energy-concentrating cutting tube and the rigid spring during use; it can only detach when intentionally caused to do so.

[0016] Preferably, the round-headed rivet passes through the pre-made hole of the shaped charge slit tube and is directly inserted into the explosive inside the shaped charge slit tube.

[0017] Preferably, the length of the rigid spring is greater than the inherent distance between the tube body composed of the two positioning menisci and the energy-concentrating slit tube body.

[0018] The construction method for a centrally loaded double-layer slotted tube device suitable for tunnel engineering includes the following steps:

[0019] Step 1. Select a PVC pipe with a diameter 10-15mm smaller than the borehole diameter. Use a cutting machine to pre-process the pipe on site. Cut a 2-4mm wide energy-concentrating slit at a 180° angle on both sides of the PVC pipe. The leftmost distance of the energy-concentrating slit should be 200-300mm from the left end of the pipe body.

[0020] Step 2. Cut a PVC pipe with a diameter 10-15mm larger than the energy-concentrating slit pipe body along the axial middle to obtain two positioning menisci of the same size. Set corresponding pre-made holes on the energy-concentrating slit pipe body and each positioning menisci. The diameter of the blast hole is slightly larger than the diameter of the uncut positioning menisci.

[0021] Step 3. Load a measured amount of explosive into the shaped charge tube, insert the detonator into the explosive, plug the left end of the shaped charge tube with a pre-made grooved cork, and pass the detonator lead wire connected to the detonator inside the shaped charge tube out through the reserved slot.

[0022] Step 4. After loading the explosive into the shaped charge slit tube, pass the round-headed rivet through the pre-processed positioning meniscus, rigid spring, and shaped charge slit tube in sequence, and then insert the round-headed rivet directly into the explosive.

[0023] Step 5. Carry out blasting construction in the tunnel. The centrally charged double-layer slit tube device is inserted into the pre-drilled peripheral blast holes by pressing the positioning menisci on both sides. Under the action of the rigid spring, the two positioning menisci are tightly attached to the blast hole wall. During placement, the line connecting the shaped charge slits is ensured to coincide with the line connecting the peripheral blast holes.

[0024] Compared with the prior art, the advantages of the present invention are:

[0025] 1) The present invention adopts a centrally loaded double-layer slit tube device, which is convenient to operate on site. The compression of the rigid spring facilitates the insertion of the double-layer slit tube device into the blast hole. When the slit tube reaches the appropriate position, the rebound of the rigid spring fixes the double-layer slit tube device in the center of the blast hole, preventing eccentricity.

[0026] 2) By selecting PVC pipes of different diameters to make shaped charge cutting tubes and selecting rigid springs of different lengths, the centrally loaded double-layer cutting tube device can be adapted to boreholes of different diameters.

[0027] 3) The shaped charge blasting tube is equipped with shaped charge blasting. Directional fracture control blasting can promote the propagation of cracks in the direction of shaped charge blasting and inhibit the propagation of explosive cracks in the direction of non-shaped charge blasting, so as to form directional cracks in the direction of the borehole connection to reduce damage to the surrounding rock.

[0028] 4) The grooved cork stopper has a reserved slot for the detonator lead wire to pass through, making it convenient for the detonator lead wire to pass through the shaped charge tube. Attached Figure Description

[0029] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0030] Figure 1 This is a side sectional view of the centrally loaded double-layer slit tube device for tunnel engineering according to the present invention;

[0031] Figure 2 The left view of the centrally loaded double-layer slit tube device for tunnel engineering of the present invention, with the grooved cork removed;

[0032] Figure 3 This is a right view of the centrally loaded double-layer slit tube device for tunnel engineering according to the present invention;

[0033] Figure 4 This is a detailed view of the round-head rivet connection of the present invention;

[0034] Figure 5 This is a perspective view of the grooved cork stopper of the present invention;

[0035] Figure 6 This is a top view of the grooved cork stopper of the present invention;

[0036] Figure 7 This is a schematic diagram of the construction method of the present invention;

[0037] Figure 8 This is a cross-sectional view showing the layout of the device of the present invention;

[0038] Figure 9 The diagrams show a comparison of the blasting effects of the device in Embodiment 1 of the present invention and the device in the comparative example. Figure A shows the blasting effect of Embodiment 1 of the present invention, and Figure B shows the blasting effect of Comparative Example 1.

[0039] In the diagram: 1-Energy-concentrating slit tube body, 2-Positioning meniscus, 3-Rigid spring, 4-Energy-concentrating slit, 5-Grooved cork plug, 6-Pre-reserved groove, 7-Round head rivet, 8-Tunnel excavation outline, 9-Pre-fabricated hole, 10-Internal screw. Detailed Implementation

[0040] The accompanying drawings are for illustrative purposes only; to better illustrate this embodiment, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product; the terms "upper," "lower," "left," "right," "side," "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. For those skilled in the art, some well-known structures and their descriptions in the drawings may be omitted, and therefore should not be construed as a limitation of the present invention.

[0041] To make the technical means, creative features, achieved objectives, and effects of this invention readily understandable, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The invention will now be described in further detail with reference to the accompanying drawings.

[0042] Example 1

[0043] like Figure 1 , Figure 2 , Figure 3 As shown, this embodiment of the invention provides a double-layer slit tube device for centrally loaded explosives suitable for tunnel engineering, including a shaped charge slit tube body 1, a positioning meniscus 2, and a grooved cork plug 5;

[0044] The positioning meniscus 2 consists of two pieces, which together form a tube with a gap in the middle, wrapped around the outside of the energy-concentrating slit tube 1. The diameter of the tube formed by the two positioning meniscus 2 is larger than the diameter of the energy-concentrating slit tube 1.

[0045] Nine pre-fabricated holes are evenly and symmetrically opened on each of the positioning menisci 2, forming three rings on their left, middle, and right sides respectively; corresponding pre-fabricated holes 9 are opened on the energy-concentrating cutting tube 1, for a total of 18 holes. A rigid spring 3 with a diameter larger than that of the pre-fabricated hole 9 is placed between the energy-concentrating cutting tube 1 and the positioning menisci 2, and a round-headed rivet 7 passes through the positioning menisci 2, the rigid spring 3, and the energy-concentrating cutting tube 1 in sequence and connects the three. Figure 2 Left side view Figure 3 In the right-side view, you can see the connection structure diagram with a ring of round-headed rivets 7 on both the left and right ports.

[0046] A circular pre-drilled hole 9 is made on the positioning meniscus 2, and the same pre-drilled hole 9 is also made on the energy-concentrating cutting tube 1 at the same corresponding position. The diameter of the circular cap at the top of the round-headed rivet 7 is larger than the diameter of the pre-drilled hole 9, the diameter of the rivet body 7 is matched with the diameter of the pre-drilled hole 9, and the length of the rivet body is greater than the sum of the thicknesses of the positioning meniscus 2, the rigid spring 3, and the energy-concentrating cutting tube 1. The diameter of the rigid spring 3 is about 2 mm larger than the diameter of the pre-drilled hole 9, and the length of the rigid spring 3 is greater than the radius width of the fixing between the positioning meniscus 2 and the energy-concentrating cutting tube 1. It is sandwiched between the positioning meniscus 2 and the energy-concentrating cutting tube 1, so that the distance between the positioning meniscus 2 and the energy-concentrating cutting tube 1 can be expanded or contracted.

[0047] Both the shaped charge cutting tube 1 and the positioning meniscus 2 are made of PVC. The diameter of the positioning meniscus 2 is 10mm larger than the diameter of the shaped charge cutting tube, so the inherent distance between the positioning meniscus 2 and the shaped charge cutting tube 1 is 5mm, meaning the length of the rigid spring 3 is greater than 5mm, and generally its length does not exceed three times the inherent distance. The round-headed rivet 7 passes through the pre-made hole 9 of the shaped charge cutting tube 1 and is directly inserted into the explosive inside the shaped charge cutting tube 1.

[0048] In this embodiment of the invention, the round-headed rivet 7 is a type of rivet that meets the requirements of existing technology. It can ensure that the rivet passes through the pre-drilled holes 9 on the positioning meniscus 2, the rigid spring 3, and the pre-drilled holes 9 on the energy-concentrating slit tube 1 without easily falling off. It can also ensure that the positioning meniscus 2 can slide along the round-headed rivet 7 when pressed. Figure 4 As shown, a round-headed rivet 7 with an internal screw 10 and an expansion portion at the bottom can be used. When in use, the internal screw 10 is screwed into the round-headed rivet 7, and the bottom of the round-headed rivet 7 expands to prevent it from falling off.

[0049] Energy-concentrating slits 4 are cut at 180° intervals on both sides of the right end of the energy-concentrating slit tube 1. The position of the energy-concentrating slits 4 corresponds to the gap left by the two positioning menisci 2. The width of the energy-concentrating slits is 4mm, and its leftmost distance is 200mm from the left end of the energy-concentrating slit tube 1. The width of the energy-concentrating slits is less than the width of the gap left by the two positioning menisci.

[0050] like Figure 5 , Figure 6As shown, the grooved cork stopper 5 is installed at the left port of the shaped charge slit tube 1 to block its left port. A pre-drilled groove 6 is provided on the side edge of the grooved cork stopper 5, extending from one end face to the other. After the explosive is loaded into the centrally loaded double-layer slit tube device, the detonator is inserted into the explosive. The grooved cork stopper 5 blocks the left port of the shaped charge slit tube 1, and the detonator lead can pass through the pre-drilled groove 6. The grooved cork stopper 5 prevents the dissipation of explosive energy and improves blasting efficiency.

[0051] This invention also relates to a construction method for a center-charge double-layer slotted tube device suitable for tunnel engineering, such as... Figure 7 As shown, the specific steps include the following:

[0052] Step 1. Select a PVC pipe with a diameter 15mm smaller than the borehole diameter. Use a cutting machine to pre-process the pipe on site. Cut a 4mm wide energy-concentrating slit 4 at a 180° angle on both sides of the PVC pipe. The leftmost distance of the energy-concentrating slit 4 should be 220mm from the left end of the energy-concentrating slit pipe body 1 to obtain the required energy-concentrating slit pipe body 1.

[0053] Step 2. Cut the PVC pipe with a diameter larger than the energy-concentrating slit tube body 1 along the axial middle to obtain two positioning menisci 2 of the same size. The PVC pipe of the positioning menisci 2 is 10mm larger than the diameter of the energy-concentrating slit tube body 1. Set corresponding pre-made holes 9 on the energy-concentrating slit tube body 1 and the positioning menisci 2. The rigid spring 3 is selected with a length of 12mm.

[0054] Step 3. Load a fixed amount of explosive into the shaped charge cutting tube 1, insert the detonator into the explosive, plug the left end of the shaped charge cutting tube 1 with a pre-made grooved cork plug 5, and pass the detonator lead wire connected to the detonator inside the shaped charge cutting tube 1 out through the reserved slot 6.

[0055] Step 4. After loading the explosive into the shaped charge slit tube, pass the round-headed rivet 7 through the processed positioning meniscus 2, rigid spring 3, and shaped charge slit tube 1 in sequence, and insert the round-headed rivet 7 directly into the explosive to make the centrally loaded double-layer slit tube device.

[0056] By pressing the positioning menisci 2 on both sides of the shaped charge slotted tube body 1, the processed double-layer slotted tube device is placed into the blast hole. During placement, as the device penetrates deeper, the round-headed rivets 7 compress the positioning menisci 2 on both sides, compressing the centered double-layer slotted tube device and ensuring that the device can be smoothly placed into the blast hole. After reaching the bottom of the blast hole, the positioning menisci 2 will adhere tightly to the blast hole wall under the rebound action of the rigid spring 3, fixing the slotted tube device in the center position of the blast hole and preventing the charge from being eccentric. The shaped charge slotted tube body 1 is equipped with shaped charge slots 4 for directional fracture control blasting. By promoting the propagation of cracks in the direction of the shaped charge slots and inhibiting the propagation of blast cracks in the direction of non-shaped charge slots, directional cracks can be formed in the direction of the blast hole connection to reduce damage to the surrounding rock.

[0057] Step 5. Carry out blasting construction in the tunnel. The centrally charged double-layer slit tube device is inserted into the pre-drilled peripheral blast holes by pressing the positioning menisci on both sides. Under the action of the rigid spring, the two positioning menisci are tightly attached to the blast hole wall. During placement, the line connecting the shaped charge slits is ensured to coincide with the line connecting the peripheral blast holes.

[0058] like Figure 8 As shown, in the tunnel engineering, the blast holes set along the tunnel outline are peripheral holes, and the cut-out hole is set in the middle of the tunnel working face. The line connecting the peripheral holes completely coincides with the tunnel excavation outline 8. Through the energy-concentrating effect of the centrally charged double-layer slotted tube device, the explosive energy is released along the tunnel excavation outline 8, i.e., the line connecting the peripheral holes. Figure 9 As shown in (A), the perimeter hole blasting outline is neat after detonation, the borehole wall is relatively smooth, there is no obvious damage in the non-shaped charge cutting direction, and the blasting effect is good.

[0059] Example 2

[0060] When using the device of this invention for construction, different borehole diameters can be addressed by selecting PVC pipes of different diameters to fabricate the shaped charge cutting tube and by selecting rigid springs of different lengths. Therefore, the centered charge double-layer cutting tube device of this invention is applicable to boreholes of different diameters. In specific use, adjustments can also be made within a suitable range of width and length.

[0061] A PVC pipe with a diameter 14 mm smaller than the borehole diameter is selected as the shaped charge cutting pipe body 1. The PVC pipe for the positioning meniscus 2 is 10 mm larger than the diameter of the shaped charge cutting pipe body 1. The rigid spring 3 is selected with a length of 8 mm. Other aspects are the same as in Example 1.

[0062] Comparative Example 1

[0063] The directional pre-splitting blasting device includes a shaped charge detonating tube made of PVC plastic, an explosive cartridge, an electric detonator, and a plug. The shaped charge detonating tube has two axially spaced slits, each 3-5 mm wide, symmetrically positioned relative to its axis. The explosive cartridge is filled inside the shaped charge detonating tube. The plug seals both ends of the shaped charge detonating tube. The electric detonator is inserted into the explosive cartridge, with its lead wire passing through the plug and positioned outside the shaped charge detonating tube. Devices such as the positioning meniscus 2 on the outer layer of Example 1 are not included.

[0064] In the aforementioned tunnel engineering, the installation method is the same as in Example 1. After detonation, due to gravity and other reasons, it is impossible to ensure centered charging, and the line connecting the slits and the lines connecting the surrounding boreholes will deviate to a certain extent. After blasting, there is obvious damage in the non-slit direction, the borehole walls are uneven, and the blasting effect is not ideal. The blasting effect is shown in the figure. Figure 9 (B)

[0065] Round-head rivets 7 can also be made of other materials such as automotive rivets or plastic clips. After passing through various holes and springs, their lower ends can expand or become more elastic, preventing the rivet or clip from falling off. Figure 1-3 Figure 8 is merely for illustrative purposes to show the connection between the positioning meniscus 2, the rigid spring 3, and the energy-concentrating slit tube 1. It is only an illustrative example and a simplified diagram. The structure and form of the circular rivet 7 are not limited to these specific details. Figure 1-3 Examples from 8 and 9.

[0066] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0067] Other areas not mentioned herein adopt the common practices in existing technologies and will not be detailed here.

[0068] Furthermore, it should be understood that although this specification describes the embodiments, it does not mean that the present invention only includes the technical solutions in the embodiments. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in the embodiments can also be appropriately combined to form other embodiments that can be understood by those skilled in the art, which are also within the protection scope of the present invention.

Claims

1. A construction method for a center-charge double-layer slotted tube device suitable for tunnel engineering, characterized in that: The device includes a slit-cutting tube, a positioning meniscus, and a grooved cork stopper; The positioning meniscus consists of two pieces, which together form a tube with a gap in the middle, wrapped around the outside of the energy-concentrating cut tube. The diameter of the tube formed by the two positioning meniscus is larger than the diameter of the energy-concentrating cut tube. Each positioning meniscus is provided with at least three pre-made holes, respectively on its left, middle and right sides. The corresponding positions of the energy-concentrating cutting tube are provided with the same pre-made holes. A rigid spring with a diameter larger than the pre-made hole is set between the energy-concentrating cutting tube and the positioning meniscus. A round-headed rivet passes through the positioning meniscus, the rigid spring and the energy-concentrating cutting tube and connects the three. The energy-concentrating slit tube body is cut at a 180° angle on both sides of the right port, and the position of the energy-concentrating slit corresponds to the position of the gap left by the two positioning menisci. The width of the energy-concentrating cut is less than the width of the gap left between the two positioning menisci; The grooved cork is installed at the left end of the energy-concentrating slit tube, and a pre-reserved groove is provided on the side edge of the grooved cork. The diameter of the round head rivet's top circular cap is larger than the diameter of the pre-drilled hole, the diameter of the rivet body is matched with the diameter of the pre-drilled hole, and the length of the rivet body is greater than the sum of the thicknesses of the positioning meniscus, the rigid spring, and the energy-concentrating slit tube. The round-headed rivet passes through the pre-made hole of the shaped charge cutting tube and is directly inserted into the explosive inside the shaped charge cutting tube. The construction method specifically includes the following steps: Step 1. Select a PVC pipe with a diameter 10-15mm smaller than the borehole diameter. Use a cutting machine to pre-process the pipe on site. Cut a 2-4mm wide energy-concentrating slit at a 180° angle on both sides of the PVC pipe. The leftmost distance of the energy-concentrating slit should be 200-300mm from the left end of the pipe body. Step 2. Cut a PVC pipe with a diameter 10-15mm larger than the energy-concentrating slit pipe body along the axial middle to obtain two positioning menisci of the same size. Set corresponding pre-made holes on the energy-concentrating slit pipe body and each positioning menisci. The diameter of the blast hole is slightly larger than the diameter of the uncut positioning menisci. Step 3. Load a measured amount of explosive into the shaped charge tube, insert the detonator into the explosive, plug the left end of the shaped charge tube with a pre-made grooved cork, and pass the detonator lead wire connected to the detonator inside the shaped charge tube out through the reserved slot. Step 4. After loading the explosive into the shaped charge slit tube, pass the round-headed rivet through the pre-processed positioning meniscus, rigid spring, and shaped charge slit tube in sequence, and then insert the round-headed rivet directly into the explosive. Step 5. Carry out blasting construction in the tunnel. The centrally charged double-layer slit tube device is inserted into the pre-drilled peripheral blast holes by pressing the positioning menisci on both sides. Under the action of the rigid spring, the two positioning menisci are tightly attached to the blast hole wall. During placement, the line connecting the shaped charge slits is ensured to coincide with the line connecting the peripheral blast holes.

2. The construction method of the centrally loaded double-layer slit pipe device for tunnel engineering according to claim 1, characterized in that, Both the energy-concentrating slit tube and the positioning meniscus are made of PVC; the diameter of the positioning meniscus is 10-15 mm larger than the diameter of the energy-concentrating slit tube.

3. The construction method of the center-loading double-layer slit pipe device for tunnel engineering according to claim 1, characterized in that, The width of the energy-concentrating slit is 2-4 mm, and its leftmost distance from the left end of the energy-concentrating slit tube is 200-300 mm.

4. The construction method of the center-loading double-layer slotted tube device for tunnel engineering according to claim 1, characterized in that, Nine pre-fabricated holes are evenly and symmetrically opened on each of the positioning menisci, forming three rings on the left, middle and right sides respectively; corresponding pre-fabricated holes are opened on the energy-concentrating slit tube body, with a total of 18 holes.

5. The construction method of the center-loading double-layer slit pipe device for tunnel engineering according to claim 1, characterized in that, The length of the rigid spring is greater than the inherent distance between the tube body composed of two positioning menisci and the energy-concentrating slit tube body.

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