A tunnel blasting method for forming a large-diameter mixed cut by laser irradiation

Abstract

This invention relates to the field of tunnel engineering and blasting construction technology, specifically a tunnel blasting method for forming large-diameter hybrid cut-outs using laser irradiation. The method includes: drilling a pilot hole; designing the location of the hollow hole; pre-treatment of the rock mass; continuous heating; and cut-out blasting. This invention involves drilling a pilot hole at the tunnel face, introducing a high-power laser into the hole to thermally irradiate the rock mass, inducing thermal cracks and delamination layers, forming or expanding into a large-diameter hollow cavity. Auxiliary holes and peripheral holes are arranged around this cavity for charging and millisecond-delay detonation, thereby achieving efficient formation of the cut-out space and effective energy concentration, increasing single-pass depth and reducing block size. Laser irradiation enables non-contact hole enlargement and pre-fragmentation, reducing reliance on high-power drilling rigs and large drilling tools, and reducing drill bit wear. It also forms a stable large-diameter hollow cavity in extremely hard surrounding rock, providing ample space for the expansion and ejection of blasting debris.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering and blasting construction technology, specifically a tunnel blasting method that utilizes laser irradiation to form a large-diameter mixed cut. Background Technology

[0002] In tunnel drilling and blasting construction in hard surrounding rock, the arrangement of cut holes is a key factor determining the single-cycle advance and blasting effect. Since tunnel blasting usually only has one free face, the release of explosive energy is limited. In order to improve the efficiency of the explosive wave in breaking the rock mass, multiple new free faces can be artificially formed inside the working face through the design and blasting of cut holes. This enhances the tensile effect of reflected tensile waves on the rock mass, thereby promoting the effective breaking of the rock mass. The formation of cut holes not only provides a channel for the propagation of explosive energy, but also creates expansion and fragmentation space for subsequent rock breaking and spoil ejection.

[0003] Traditional straight-hole cutting typically involves creating the cutting space by arranging multiple small-diameter parallel holes. However, in extremely hard rock masses, this method requires a large number of small holes with strict spacing requirements, and suffers from high drill bit wear and low efficiency, often resulting in limited single-pass depth, typically less than 5 meters. To address this issue, engineering practice has demonstrated that using a hybrid cutting technique with large-diameter holes can significantly increase the volume of the cutting space, simplify drilling procedures and explosive loading, thereby improving tunneling efficiency and reducing the proportion of large blocks. Research on the thermal fracturing mechanism of rock masses irradiated by lasers shows that continuous or millisecond pulsed lasers can generate high-temperature gradients and thermal stress on the surface of rock masses such as granite, inducing the formation of thermal cracks, delamination layers, and even localized melting zones, thus achieving non-contact directional fracturing.

[0004] However, traditional slotting has the following disadvantages: In particularly hard surrounding rocks such as granite, relying solely on mechanical methods to drill ultra-large diameter holes still faces problems such as high drilling resistance, severe drill bit wear, and poor hole wall quality, which limits the further promotion and application of large-diameter hybrid grooving technology. Summary of the Invention

[0005] The purpose of this invention is to provide a tunnel blasting method that uses laser irradiation to form large-diameter hybrid slots, in order to solve the problems mentioned in the background art, such as high drilling resistance, severe wear of drilling tools, and poor hole wall quality when drilling ultra-large diameter holes by mechanical means alone in particularly hard surrounding rocks such as granite, which limits the further promotion and application of large-diameter hybrid slotting technology.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a tunnel blasting method for forming large-diameter hybrid cuts using laser irradiation, comprising the following steps: Step 1: Drilling the pilot hole: Drill the pilot hole at the tunnel face according to the design; Step 2, Hole Location Design: On the tunnel face, design large-diameter holes and auxiliary slotting holes according to the cross-sectional dimensions and surrounding rock conditions. The auxiliary slotting holes are symmetrically arranged around the circumference of the holes. Step 3, Rock mass pretreatment: High-power laser is used to irradiate the rock around the guide hole in the axial and circumferential directions to induce thermal cracks and exfoliation layers in the rock mass, thereby expanding it into a large-diameter hollow cavity at the predetermined location; Step 4, Continuous heating: During laser irradiation, the slow heating characteristic of the differential pulse laser is used to achieve stable heating, overcoming the problem of heat transfer obstruction caused by the accumulation of molten material during continuous laser irradiation, and is combined with high-pressure gas to clean the holes; Step 5, Cutting and Blasting: After the hole is formed, millisecond-level micro-delay blasting is carried out on the inner ring cutting holes 1 to 4 and the outer ring auxiliary holes 1 to 4 according to the designed blasting sequence, so as to realize the cutting and blasting of the working face and long-length tunneling.

[0007] In step one, the specific process for drilling the pilot hole is as follows: 1.1 Material pretreatment: Clean the surface of the rock mass and spray a black oxide layer light-absorbing material onto the rock processing area to improve laser absorption efficiency; 1.2 Laser parameter settings: A high peak power, low duty cycle pulsed laser is used. The depth and diameter of the aperture are controlled by adjusting the pulse frequency and energy density. The laser beam is focused into a micron-sized spot by a lens to ensure concentrated energy. 1.3 Processing execution: The material is irradiated with intermittent laser pulses, each pulse melting and vaporizing a small amount of material, gradually penetrating to form holes. Inert gas is used to blow away slag and reduce the heat-affected zone. 1.4 Post-processing: Remove carbon deposits or plasma residue from the borehole walls to ensure the borehole is clean. Verify the borehole diameter, depth, and shape accuracy using three-dimensional measurement equipment.

[0008] In step one, the diameter of the guide hole is 40-60mm. In step two, the empty hole and the auxiliary slotting hole are arranged perpendicular to the free surface of the working face.

[0009] In step three, the high-power laser is either a continuous laser or a pulsed laser, with a power range of 2-20kW and a single-point irradiation time of 0.5-3s, to induce thermal stress cracks in the rock mass and form a desquamation layer.

[0010] In step three, the target diameter of the hollow cavity is 80-200 mm. The hollow cavity is a single-cavity structure or a parallel multi-cavity structure formed by processing two or more guide holes, in order to adapt to different lithologies and drilling requirements.

[0011] In step four, the slow heating characteristic of differential pulse laser is used to achieve stable heating. After the hollow cavity is formed or expanded by laser irradiation, a mechanical cleaning device or a pneumatic cleaning device is used to remove debris from the cavity. A measuring probe or video device is used to detect the forming quality and actual aperture of the cavity.

[0012] In step five, the inner ring slotted holes one to four and the outer ring auxiliary holes one to four are detonated in sequence with a delay of 3-8ms.

[0013] The method uses a high-power laser, which includes a laser emitting device, an optical fiber or laser nozzle transmission assembly, a cooling system and a protective cover. One end of the laser emitting device is connected to one end of the optical fiber or laser nozzle transmission assembly, and the other end of the optical fiber or laser nozzle transmission assembly is fixedly connected to one end of the protective cover. A cooling system is fitted on the outside of the laser emitting device. Laser emitting devices are used to emit high-power lasers; The laser nozzle transmission component within the fiber optic or laser nozzle transmission assembly is used to guide the cutting gas, such as oxygen, to form high pressure, accelerate the oxidation reaction, remove slag, and improve cutting speed and quality. The nozzle orifice diameter adjusts the gas pressure, affecting the cutting surface pressure and slag removal efficiency. The optical fiber is used for the optical waveguide effect in the fiber core to transmit optical signals. The cooling system absorbs the heat generated by the laser emitting device by circulating coolant such as water or antifreeze, preventing overheating that could damage the equipment or degrade its performance. The protective shield is used to isolate the laser irradiation area and control smoke and reflected light.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. This method involves drilling a guide hole at the working face, introducing a high-power laser into the hole to thermally irradiate the rock mass, inducing thermal cracks and exfoliation layers in the rock mass, forming or expanding into a large-diameter hollow cavity, and arranging auxiliary holes and peripheral holes around the cavity for charging and millisecond-delay detonation, thereby achieving efficient formation of the slotting space and effective energy concentration, increasing the single advance and reducing the block size; 2. Utilizing laser irradiation to achieve non-contact hole enlargement and pre-fragmentation reduces reliance on high-power drilling rigs and large drilling tools, significantly reducing drill tool wear; 3. It is easier to form stable large-diameter hollow cavities in extremely hard surrounding rock, providing ample space for the expansion and ejection of blasting material, which is conducive to improving the single-cycle advance. 4. The slow heating characteristic of micro-difference pulsed laser achieves stable heating, overcoming the problem of heat transfer obstruction caused by molten material accumulation during continuous laser irradiation. It is also combined with high-pressure gas cleaning to reduce slag blockage, shorten hole forming time, and improve processing efficiency. 5. The laser irradiation process allows for parameter control and automated operation, making it suitable for integration with intelligent drilling and blasting equipment to improve construction safety and repeatability; 6. The method of adjusting the diameter and number of hollow cavities according to different rock types and advance requirements is highly applicable and has high engineering promotion value. Attached Figure Description

[0015] Figure 1 This is a flowchart of the present invention; Figure 2 This is a flowchart of the guide hole drilling process of the present invention; Figure 3 This is a schematic diagram of the large-diameter mixed excavation arrangement at the tunnel face according to the present invention.

[0016] In the diagram: 1: Inner ring slot hole one, 2: Inner ring slot hole two, 3: Inner ring slot hole three, 4: Inner ring slot hole four, 5: Outer ring slot hole one, 6: Outer ring slot hole two, 7: Outer ring slot hole three, 8: Outer ring slot hole four, 9: Hole, L: Radial distance from the center of the hole to the inner ring slot hole, a: Hole spacing between the inner ring slot holes. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1

[0019] Please see Figures 1-3 This invention provides a tunnel blasting method for forming large-diameter hybrid cuts using laser irradiation, comprising the following steps: Step 1: Drilling the pilot hole: Drill the pilot hole at the tunnel face according to the design; Step 2, Hole Location Design: On the tunnel face, based on the cross-sectional dimensions and surrounding rock conditions, design large-diameter holes 9 and auxiliary slotting holes. The auxiliary slotting holes are symmetrically arranged around the circumference of hole 9. L and a are used together to define the spatial geometric relationship of the inner ring slotting holes to control the formation conditions of the slotting area. L is used to determine the arrangement radius of the inner ring slotting holes relative to the hole, controlling the spatial scale of the slotting area and the formation conditions of the free surface. a is used to determine the hole spacing between the inner ring slotting holes, controlling the degree of penetration of the cracks between adjacent holes and the continuity of the slotting structure.

[0020] Step 3, Rock mass pretreatment: High-power laser is used to irradiate the rock around the guide hole in the axial and circumferential directions to induce thermal cracks and exfoliation layers in the rock mass, thereby expanding it into a large-diameter hollow cavity at the predetermined location; Step 4, Continuous heating: During laser irradiation, the slow heating characteristic of the differential pulse laser is used to achieve stable heating, overcoming the problem of heat transfer obstruction caused by the accumulation of molten material during continuous laser irradiation, and is combined with high-pressure gas to clean the holes; Step 5, Cutting and Blasting: After the hole is formed, the inner ring cutting holes 1 to 4 and the outer ring auxiliary holes 5 to 8 are detonated in sequence with a delay of 3-8ms, thereby realizing the cutting and blasting of the working face and the long advance of the tunnel.

[0021] In step one, the specific process for drilling the pilot hole is as follows: 1.1 Material pretreatment: Clean the surface of the rock mass and spray a black oxide layer light-absorbing material onto the rock processing area to improve laser absorption efficiency; 1.2 Laser parameter settings: A high peak power, low duty cycle pulsed laser is used. The depth and diameter of the aperture are controlled by adjusting the pulse frequency and energy density. The laser beam is focused into a micron-sized spot by a lens to ensure concentrated energy. 1.3 Processing execution: The material is irradiated with intermittent laser pulses, each pulse melting and vaporizing a small amount of material, gradually penetrating to form holes. Inert gas is used to blow away slag and reduce the heat-affected zone. 1.4 Post-processing: Remove carbon deposits or plasma residue from the borehole walls to ensure the borehole is clean. Verify the borehole diameter, depth, and shape accuracy using three-dimensional measurement equipment.

[0022] In step two, both the empty hole 9 and the auxiliary slotting hole are arranged perpendicular to the free surface of the working face.

[0023] In step three, the high-power laser is either a continuous laser or a pulsed laser, with a power range of 2-20kW and a single-point irradiation time of 0.5-3s, to induce thermal stress cracks in the rock mass and form a desquamation layer.

[0024] In step three, the target diameter of the hollow cavity is 80-200 mm, and the diameter of the guide hole in step one is 40-60 mm.

[0025] In step three, the high-power laser includes a laser emitting device, an optical fiber or laser nozzle transmission assembly, a cooling system, and a protective cover. One end of the laser emitting device is connected to one end of the optical fiber or laser nozzle transmission assembly, and the other end of the optical fiber or laser nozzle transmission assembly is fixedly connected to one end of the protective cover. A cooling system is fitted on the outside of the laser emitting device. Laser emitting devices are used to emit high-power lasers; The laser nozzle transmission component within the fiber optic or laser nozzle transmission assembly is used to guide the cutting gas, such as oxygen, to form high pressure, accelerate the oxidation reaction, remove slag, and improve cutting speed and quality. The nozzle orifice diameter adjusts the gas pressure, affecting the cutting surface pressure and slag removal efficiency. The optical fiber is used for the optical waveguide effect in the fiber core to transmit optical signals. The cooling system absorbs the heat generated by the laser emitting device by circulating coolant such as water or antifreeze, preventing overheating that could damage the equipment or degrade its performance. The protective shield is used to isolate the laser irradiation area and control smoke and reflected light.

[0026] In step three, the hollow cavity is either a single-cavity structure or a parallel multi-cavity structure formed by processing with two or more guide holes, in order to adapt to different lithologies and drilling requirements.

[0027] In step four, the slow heating characteristic of differential pulse laser is used to achieve stable heating. After the hollow cavity is formed or expanded by laser irradiation, mechanical cleaning device or pneumatic cleaning device is used to remove debris in the cavity, and measuring probe or video device is used to detect the forming quality and actual aperture of the cavity.

[0028] In step five, the detonation sequence is as follows: first, detonate the center hole or cutting hole, and then detonate the peripheral holes and auxiliary holes in sequence with a delay of 3-8ms.

[0029] Example 2

[0030] In this embodiment, a granite tunnel is excavated using the drill-and-blast method. The surrounding rock is intact and extremely hard. Using the method described in Example 1, the target advance per single cycle is designed to be 8-10m. At the center of the tunnel face, a guide hole with a diameter of 40mm and a depth of 1.8m is first drilled using a rock drilling rig. A pulsed laser with a peak power of approximately 8kW is selected. Through reciprocating scanning along the axial and circumferential directions of the hole, thermal stress cracks and delamination layers are generated in the rock mass at the bottom and wall of the hole. The hole diameter is gradually expanded to approximately 150mm, forming a stable large-diameter hollow cavity. After laser irradiation, a pneumatic cleaning device blows out the loose debris from the cavity. A probe is used to detect the measured diameter and depth of the cavity. After confirming that the design requirements were met, eight auxiliary holes and several peripheral holes with a diameter of 32 mm and a depth of 3.2 m were arranged around the hollow cavity. The explosives were charged and filled in sections according to the slotting design. The detonation adopted a millisecond micro-delay detonation method. First, the cutting hole near the center of the slotting was ignited or a small amount of detonating charge was placed in the cavity. Then, the peripheral holes and auxiliary holes were detonated in sequence with a delay of 3-8 ms to achieve explosive fragmentation with energy concentrated in the hollow cavity and free surface. The field test results showed that the single-cycle advance increased from about 5 m with traditional small-hole slotting to about 9 m, the large block rate decreased from about 16.4% to about 2.5%, the forming quality of the working face was good, and the distribution of the explosive block size was uniform.

[0031] Example 3

[0032] In this embodiment, for scenarios requiring larger tunnel cross-sections and greater rock expansion space, two or more guide holes can be arranged at the tunnel face, and laser irradiation can be used to enlarge the holes, so that adjacent hollow cavities are partially connected inside the rock mass, forming a parallel multi-cavity composite slotting structure. The remaining drilling arrangement, charging, and detonation methods are similar to those in Embodiment 2. The multi-cavity structure provides a larger space for blasting expansion compensation in extremely hard surrounding rock, further reducing the risk of blasting blockage in the cavities and improving the reliability of long-length blasting excavation.

[0033] Example 4

[0034] In this embodiment, a pilot hole is drilled at the tunnel face. A high-power laser is used to thermally irradiate the pilot hole wall and the surrounding rock mass, inducing thermal cracks and delamination layers in the rock mass, thereby expanding the hollow cavity. By utilizing the slow heating characteristics and thermal stability of the micro-difference pulse laser, a long and stable deep hole is formed in the rock mass, providing a free surface and space for subsequent auxiliary hole blasting. Auxiliary holes and peripheral holes are arranged around the cavity. Charges are loaded according to the design and millisecond-level micro-difference initiation is implemented to achieve efficient slotting and long-cut blasting at the tunnel face. This method replaces traditional mechanical slotting with laser non-contact hole enlargement technology, which has the advantages of high thermal stability, good hole wall quality, and high energy utilization. Compared with continuous laser method, it has less slag and higher heat transfer efficiency. Compared with traditional slotting blasting, it forms a large hollow structure in one go, significantly increasing the drilling footage, reducing drilling costs and operation time. It is particularly suitable for tunnel drilling and blasting construction in extremely hard surrounding rock with poor blastability, such as granite and basalt.

[0035] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A tunnel blasting method for forming large-diameter hybrid cuts using laser irradiation, characterized in that, Includes the following steps: Step 1: Drilling the pilot hole: Drill the pilot hole at the tunnel face according to the design; Step 2, Hole Location Design: On the tunnel face, design large-diameter holes and auxiliary slotting holes according to the cross-sectional dimensions and surrounding rock conditions. The auxiliary slotting holes are symmetrically arranged around the circumference of the holes. Step 3, Rock mass pretreatment: High-power laser is used to irradiate the rock around the guide hole in the axial and circumferential directions to induce thermal cracks and exfoliation layers in the rock mass, thereby expanding it into a large-diameter hollow cavity at the predetermined location; Step 4, Continuous heating: During laser irradiation, the slow heating characteristic of the differential pulse laser is used to achieve stable heating, overcoming the problem of heat transfer obstruction caused by the accumulation of molten material during continuous laser irradiation, and is combined with high-pressure gas to clean the holes; Step 5, Cutting and Blasting: After the hole is formed, the main cutting hole, auxiliary cutting hole and surrounding holes are detonated with millisecond-level micro-delay according to the designed detonation sequence, so as to realize the cutting and blasting of the working face and long-length tunneling.

2. The tunnel blasting method for forming large-diameter hybrid cuts using laser irradiation according to claim 1, characterized in that: In step one, the specific process for drilling the pilot hole is as follows: 1.1 Material pretreatment: Clean the surface of the rock mass and spray a black oxide layer light-absorbing material onto the rock processing area to improve laser absorption efficiency; 1.2 Laser parameter settings: A high peak power, low duty cycle pulsed laser is used. The depth and diameter of the aperture are controlled by adjusting the pulse frequency and energy density. The laser beam is focused into a micron-sized spot by a lens to ensure concentrated energy. 1.3 Processing execution: The material is irradiated with intermittent laser pulses, each pulse melting and vaporizing a small amount of material, gradually penetrating to form holes. Inert gas is used to blow away slag and reduce the heat-affected zone. 1.4 Post-processing: Remove carbon deposits or plasma residue from the borehole walls to ensure the borehole is clean. Verify the borehole diameter, depth, and shape accuracy using three-dimensional measurement equipment.

3. The tunnel blasting method for forming large-diameter hybrid cuts using laser irradiation according to claim 1, characterized in that: In step one, the diameter of the guide hole is 40-60mm; in step two, the empty hole and the auxiliary slotting hole are arranged perpendicular to the free surface of the working face.

4. The tunnel blasting method for forming large-diameter hybrid cuts using laser irradiation according to claim 1, characterized in that: In step three, the high-power laser is either a continuous laser or a pulsed laser, with a power range of 2-20kW and a single-point irradiation time of 0.5-3s, to induce thermal stress cracks in the rock mass and form a desquamation layer.

5. The tunnel blasting method for forming large-diameter hybrid cuts using laser irradiation according to claim 1, characterized in that: In step three, the target diameter of the hollow cavity is 80-200 mm. It is either a single-cavity structure or a parallel multi-cavity structure formed by processing two or more guide holes, in order to adapt to different lithologies and drilling requirements.

6. The tunnel blasting method for forming large-diameter hybrid cuts using laser irradiation according to claim 1, characterized in that: In step four, the slow heating characteristic of differential pulse laser is used to achieve stable heating. After the hollow cavity is formed or expanded by laser irradiation, a mechanical cleaning device or a pneumatic cleaning device is used to remove debris from the cavity. A measuring probe or video device is used to detect the forming quality and actual aperture of the cavity.

7. The tunnel blasting method for forming large-diameter hybrid cuts using laser irradiation according to claim 1, characterized in that: In step five, the inner ring slotted holes one to four and the outer ring auxiliary holes one to four are detonated in sequence with a delay of 3-8ms.

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