Blasting method for shallow shaft with medium and small sections at top of tunnel

Abstract

The invention discloses a blasting method for a small and medium section shallow shaft at the top of a tunnel, and relates to the technical field of tunnel construction, comprising the following steps: S1, reverse drilling: drilling a full-well depth blast hole in the tunnel from bottom to top, and communicating the blast hole with the outside of the upper part of the tunnel; s2, multiple sections of explosives covering the whole well depth are suspended from the ends, communicated with the outside, of the blast holes; and S3, the multiple sections of explosives are detonated from bottom to top in sequence at intervals. According to the method, the blast hole is directly drilled through in the tunnel, namely, the hole is drilled upwards from the top of the tunnel until the ground is broken through, and then one-time well completion is performed in a multi-section type suspension explosive interval detonation mode, so that on one hand, the process conversion between multi-time drilling and multi-time blasting can be reduced, a construction platform does not need to be lapped, labor is saved, and the construction cost is reduced; the construction progress is accelerated; and on the other hand, the blast hole is opened, the explosive is directly suspended above the blast hole, and the utilization rate of the blast hole can be increased by setting the number of sections of the explosive and the height of each section of the explosive.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel construction, in particular to a blasting method for a shallow vertical shaft with a small or medium cross section at the top of a tunnel. Background Art

[0002] For the blasting of small and medium-section rock formations faced in the construction of shallow shafts attached to tunnels that cannot be drilled from the top, the existing technology generally adopts a segmented drilling and blasting process, which has significant technical bottlenecks. For example, in a certain mountainous city subway (light rail) tunnel, three shallow shafts with a net diameter of 4.0m and a depth of 11.0-13.0m are built above the tunnel for ventilation as needed. The thickness of the shaft steel mesh sprayed concrete (C30) is 200mm, and the thickness of the cast-in-place concrete (strength grade C40) is 300mm. Due to the steep slope of the top of the mountain (70°~90°), the equipment cannot go up, and due to special requirements, no vegetation can be destroyed. Therefore, construction can only be carried out from the tunnel upwards. The net cross-section of the shaft is 12.56m 2 The excavation section is 19.63m 2 , belonging to small and medium sections. The rock type is mainly sandstone, with good integrity, uniaxial compressive strength of rock 68.5 ~ 90.5MPa, firmness coefficient f = 7.0 ~ 9.0, belonging to Class III surrounding rock.

[0003] The existing plan is to use a YT-28 air-leg rock drill and a φ42mm diameter straight-shaped drill bit to drill holes, using a wedge-shaped grooving method. The grooving depth is 2.5m, and the depth of other blastholes is 2.0m. There are 38 blastholes in the entire section, with a total of 81.5kg of explosives. The penetration of each blasthole is 1.2 to 1.6m, and the remaining blastholes are 0.4 to 0.8m long.

[0004] Disadvantages of existing solutions:

[0005] ① Segmented drilling and blasting. Each time drilling and blasting is carried out, a platform needs to be set up in the tunnel. This process is repeated, wasting manpower and materials, slowing down the construction progress and increasing costs.

[0006] ② Although the groove depth is 2.5m, the charge cannot be fixed to the top of the blasthole and can only be pushed to the middle and upper part with a long wooden plug. The emulsion explosive may also be broken. The penetration of each blast is 1.2 to 1.6m, and the remaining blasthole is 0.4 to 0.8m long. The utilization rate of the blasthole is only 60% to 80%. The penetration is too low and the groove effect after blasting is very poor. Summary of the invention

[0007] The purpose of the present invention is to provide a blasting method for shallow vertical shafts with small and medium sections at the top of a tunnel, so as to solve the problems existing in the above-mentioned prior art, change the charging structure mode, improve the blasting effect, speed up the construction speed, reduce the cost, and meet the occupational health requirements of the operators.

[0008] To achieve the above object, the present invention provides the following solutions:

[0009] A blasting method for a shallow shaft with a small or medium cross section at the top of a tunnel comprises the following steps:

[0010] S1, reverse drilling, drilling a full-depth blast hole from bottom to top in the tunnel, the blast hole is connected to the outside of the upper part of the tunnel;

[0011] S2, suspending multiple sections of explosives covering the entire well depth from one end of the blasthole connected to the outside world;

[0012] S3. Detonating the multiple sections of explosives in sequence from bottom to top.

[0013] In an exemplary embodiment, in step S1, the blasthole includes a center eye, a groove eye, an expanded groove eye, an auxiliary eye and a peripheral eye, the groove eye is arranged along a first circular trajectory, the expanded groove eye is arranged along a second circular trajectory, the auxiliary eye is arranged along a third circular trajectory, and the peripheral eye is arranged along a fourth circular trajectory, and the radii of the first circular trajectory, the second circular trajectory, the third circular trajectory and the fourth circular trajectory increase successively, and all have the center eye as the center.

[0014] In an exemplary embodiment, in step S2, the amount of each section of explosive suspended in the same blasthole is the same.

[0015] In an exemplary embodiment, in step S2, the number of sections of explosives arranged in the cut hole, the expanded hole, the auxiliary hole and the peripheral hole is the same, and the heights of each section of explosives correspond to each other.

[0016] In an exemplary embodiment, in the step S1, the number of the cut holes, the expanded holes, the auxiliary holes and the peripheral holes increases in sequence.

[0017] In an exemplary embodiment, in the step S2, the amount of explosives in the same section of the cut hole, the expanded hole, the auxiliary hole and the peripheral hole arranged from the inside to the outside with the central hole as the center of the circle decreases successively.

[0018] In an exemplary embodiment, in step S2, the total amount of explosives in all the cut holes is less than the total amount of explosives in all the expanded holes, the total amount of explosives in all the expanded holes is less than the total amount of explosives in all the auxiliary holes, and the total amount of explosives in all the auxiliary holes is less than the total amount of explosives in all the peripheral holes.

[0019] In an exemplary embodiment, in step S3, the explosives in the cut hole, the expanded hole, the auxiliary hole and the peripheral hole are sequentially detonated at intervals.

[0020] In an exemplary embodiment, in step S2, the staff at the top outside the tunnel lowers the explosive installation belt from the end of the blasthole connected to the outside world, and the staff inside the tunnel catches it and installs the explosives on the explosive installation belt in sections. After installation, the staff at the top outside the tunnel pulls the explosive installation belt upward until the explosives reach a specified height.

[0021] In an exemplary embodiment, in step S3, a digital electronic detonator is used to achieve millisecond-level delayed detonation.

[0022] Compared with the prior art, the present invention has achieved the following technical effects:

[0023] By drilling directly through the blasthole in the tunnel, that is, drilling from the top of the tunnel upwards until breaking through the ground, the depth of the hole is the full depth of the vertical shaft to be built, and then using multi-stage suspended explosives to detonate once at intervals to form the well, on the one hand, it can reduce the process conversion between multiple drilling and multiple blasting, and there is no need to overlap construction platforms, which saves labor, reduces construction costs, and speeds up construction progress; on the other hand, by drilling through the blasthole and suspending explosives directly from above the blasthole, the utilization rate of the blasthole can be improved by setting the number of sections of explosives and the height of each section of explosives. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 A schematic diagram of blasthole arrangement for a blasting method for a shallow vertical shaft with a small or medium cross section at the top of a tunnel disclosed in a specific embodiment of the present invention;

[0026] Figure 2 A blasthole numbering diagram of a blasting method for a shallow vertical shaft with a small or medium cross section at the top of a tunnel disclosed in a specific embodiment of the present invention;

[0027] Figure 3 for Figure 1 AA section view;

[0028] Among them, 1. center eye; 2. groove eye; 3. expanded groove eye; 4. auxiliary eye; 5. peripheral eye; 6. first circular trajectory; 7. second circular trajectory; 8. third circular trajectory; 9. fourth circular trajectory; 10. explosive installation belt; 11. explosives. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. People familiar with the technology can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The purpose of the present invention is to provide a blasting method for small and medium-section shallow shafts at the top of a tunnel, so as to solve the problems existing in the prior art, change the charging structure mode, improve the blasting effect, speed up the construction speed, reduce the cost, and meet the occupational health requirements of the operators.

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] This embodiment provides a blasting method for a shallow vertical shaft with a small or medium cross section at the top of a tunnel, comprising the following steps:

[0033] S1, reverse drilling, drilling the full-depth blasthole from bottom to top in the tunnel, the blasthole is connected with the outside world above the tunnel;

[0034] S2, suspending multiple sections of explosives 11 covering the entire well depth from one end of the blasthole connected to the outside world;

[0035] S3, detonating multiple sections of explosives 11 in sequence from bottom to top.

[0036] On the one hand, this embodiment directly drills blastholes in the tunnel, that is, drills holes from the top of the tunnel upwards until the ground is broken through. The depth of the hole is the full depth of the vertical shaft to be built, and then multi-stage suspended explosives are used to detonate once at intervals to form a well, thereby reducing the process conversion between multiple drilling and multiple blasting, and there is no need to overlap construction platforms, which saves labor, reduces construction costs, and speeds up construction progress. On the other hand, by drilling the blastholes and directly suspending explosives from above the blastholes, the utilization rate of the blastholes can be improved by setting the number of sections of explosives and the height of each section of explosives.

[0037] Specifically, taking the above case as an example, a certain mountain city subway (light rail) tunnel, according to needs, built three shallow shafts with a net diameter of 4.0m and a depth of 11.0~13.0m above the tunnel for ventilation. The thickness of the shaft steel mesh sprayed concrete (C30) is 200mm, and the thickness of the cast-in-place concrete (strength grade C40) is 300mm. Due to the steep slope of the top of the mountain (70°~90°), the equipment cannot go up, and due to special requirements, no vegetation can be destroyed. Therefore, construction can only be carried out from the tunnel upwards. The net cross-section of the shaft is 12.56m2 The excavation section is 19.63m 2 , belonging to small and medium sections. The rock type is mainly sandstone, with good integrity, uniaxial compressive strength of rock 68.5 ~ 90.5MPa, firmness coefficient f = 7.0 ~ 9.0, belonging to Class III surrounding rock.

[0038] In step S1, the specific type and number of blastholes are designed according to the cross-sectional size of the shaft. In the present embodiment, the blastholes to be drilled include a center hole 1, a groove hole 2, an expanded groove hole 3, an auxiliary hole 4 and a peripheral hole 5. The groove hole 2 is arranged along the first circular trajectory 6, the expanded groove hole 3 is arranged along the second circular trajectory 7, the auxiliary hole 4 is arranged along the third circular trajectory 8, and the peripheral hole 5 is arranged along the fourth circular trajectory 9. The radii of the first circular trajectory 6, the second circular trajectory 7, the third circular trajectory 8 and the fourth circular trajectory 9 increase successively, and all of them take the center hole 1 as the center. The number of groove holes 2, expanded groove holes 3, auxiliary holes 4 and peripheral holes 5 increases successively. Please refer to the arrangement of blastholes. Figure 1 .

[0039] During the specific construction, a tunnel boring machine is used to construct from inside the tunnel. The surveying personnel first lay out the position of the shaft center eye 1 and the cross line, and then draw the positions of the groove eye 2, the expansion eye 3, the auxiliary eye 4, and the peripheral eye 5 according to the design.

[0040] Crawler tunnel boring machine in place, use specifications Hollow hexagonal steel drill rod, can be continuously extended, Use a cross-shaped alloy steel drill bit to drill a 60mm diameter hollow hole in the center of the wellbore. Use the drill bit to drill the groove hole 2, the expansion hole 3, the auxiliary hole 4 and the peripheral hole 5 according to the blasthole layout diagram.

[0041] The original "YT-28 air-leg rock drill for drilling shallow holes in sections" was changed to "tunnel drilling rig for drilling full-depth blastholes", so that operators do not have to look up to face dust, magma and water, which meets the occupational health requirements of the staff and ensures the efficiency of task completion.

[0042] The tunnel boring machine can adopt the Changsheng brand tunnel boring machine, the parameters are as follows:

[0043] Mainstream pump: double pump

[0044] Track chassis size: 3M*2.3M

[0045] Travel motor: 8T

[0046] Drilling angle: 360°

[0047] Rotation angle: 360°

[0048] Voltage / Frequency: 4500W

[0049] Track shoe width: 400mm

[0050] In step S2, the staff at the top outside the tunnel lowers the explosive installation belt 10 from the end of the blasthole connected to the outside world. After the staff inside the tunnel catches it, they install the explosives 11 on the explosive installation belt 10 in sections. After the installation, the staff at the top outside the tunnel pulls the explosive installation belt 10 upward until the explosives 11 reach the specified height.

[0051] Specifically, first, prepare the explosive installation belts 10, the number of which is the same as the number of blastholes on the blasthole layout diagram, and number the explosive installation belts 10 so that they correspond to the blasthole numbers marked on the blasthole layout diagram (e.g. Figure 2 As shown, Figure 2 The numbers in represent the blast hole numbers, not the reference numerals) and correspond one to one.

[0052] Then, according to the design, the installation position marks of multiple sections of explosives 11 are set at different length positions of each explosive installation belt 10. For example, in this embodiment, the depth of the shallow shaft is 11.0-13.0m, and the length of the explosive installation belt 10 is designed to be 25-30m, of which part of the length is used for charging, and the remaining length is used for traction. From the bottom to the top, 3.5m is the first section of explosives installation point, 7.0m is the second section of explosives installation point, and 10.5m is the third section of explosives installation point.

[0053] The staff carries the prepared explosive installation belt 10 to the top of the mountain above the tunnel, compares the blast hole number with the number of the explosive installation belt 10, and puts the explosive installation belt 10 down from the corresponding blast holes one by one.

[0054] In the tunnel, explosives 11 are prepared in units, and each unit of explosives is numbered in the manner of blasthole number-section number, such as 1-1, which represents blasthole No. 1, the first section of explosives. The staff in the tunnel receives the explosive installation belt 10 of the corresponding number, and installs the explosives of the corresponding unit at the corresponding position of the explosive installation belt 10 according to the number. After all the explosives 11 are installed, they must be inspected and put into use only after they are inspected and found to be correct.

[0055] After the explosives 11 are installed and checked, the staff at the top outside the tunnel pulls the explosive installation belt 10 upward to the designed position, and then fixes the explosive installation belt 10 on the fixed piles prepared on the mountain. After all the explosive installation belts 10 and explosives 11 are installed, they are checked again, and only after they are correct can the blasting be prepared.

[0056] The design of the charge amount needs to be combined with rock formation characteristics, engineering objectives and safety requirements, and the optimal blasting effect must be achieved through scientific design and construction.

[0057] The engineering goal of this case is to build a ventilation shaft for a tunnel in a mountainous area. The rock structure in this area is uniform, and the blasting target is a shallow well with a small and medium section. Therefore, the charge design method of this case is as follows: the amount of each section of explosives 11 suspended in the same blasthole is the same, the number of sections of explosives 11 set in the cut hole 2, the expanded slot hole 3, the auxiliary hole 4 and the peripheral hole 5 is the same, and the height of each section of explosives 11 corresponds to each other. With the center hole 1 as the center of the circle, the amount of explosives 11 in the corresponding same section of the cut hole 2, the expanded slot hole 3, the auxiliary hole 4 and the peripheral hole 5 arranged from the inside to the outside decreases in sequence. The total amount of explosives 11 in all the cut holes 2 is less than the total amount of explosives 11 in all the expanded slot holes 3, the total amount of explosives 11 in all the expanded slot holes 3 is less than the total amount of explosives 11 in all the auxiliary holes 4, and the total amount of explosives 11 in all the auxiliary holes 4 is less than the total amount of explosives 11 in all the peripheral holes 5.

[0058] The specific charge design is shown in Table 1, where the hole number - that is, the blast hole number - please refer to Figure 2 .

[0059] Table 1 Design parameters for one-step well completion by suspended charge staged blasting in shallow vertical shaft with hard rock

[0060]

[0061] In step S3, the explosives 11 in the cut hole 2, the expanded hole 3, the auxiliary hole 4 and the peripheral hole 5 are detonated in sequence, and the multiple sections of explosives 11 in each blast hole are detonated in sequence from bottom to top. Specifically, digital electronic detonators can be used to achieve millisecond-level delayed detonation.

[0062] The above charge design combined with interval detonation has the following advantages:

[0063] First, layered energy release and blasting sequence optimization

[0064] The first, second and third sections of explosives 11 are detonated in order from bottom to top. When there is a blasting blind area or an incompletely broken area in the first section blasting, the second section blasting triggered by a millisecond delay can produce a secondary crushing effect. This progressive blasting mode effectively utilizes the synergistic effect of the stress wave reflection and stretching mechanism and the quasi-static pressure field of the detonation product, so that the rock crushing process forms a dynamic stress compensation mechanism, thereby improving the uniformity of the overall blasting block size, reducing the large block rate index, and at the same time improving the effective utilization rate of explosives through energy redistribution.

[0065] The slotted hole 2, the expanded slotted hole 3, the auxiliary hole 4 and the peripheral hole 5 are detonated in the order of "from inside to outside". The number of sections of explosives 11 in each type of blasthole is the same and the height corresponds to ensure the layered release of blasting energy. The slotted hole 2 with the least total charge is detonated first, concentrating the energy to form an initial free surface in the central area, providing an open surface for subsequent blasting and reducing the clamping effect of the surrounding rock. The expanded slotted hole 3 and the auxiliary hole 4 with increasing total charge are detonated with a delay, and the blasting range is gradually expanded by using the formed free surface. The increasing charge can adapt to the increase in rock resistance and improve the crushing efficiency. The peripheral hole 5 with the largest total charge but reduced single-section charge is detonated last. Through the combination of low single-section charge (reduced charge per unit height) + high total charge, fine control of the contour surface is achieved to reduce over-excavation and surrounding rock damage.

[0066] Second, energy gradient distribution and vibration control

[0067] The total charge increases from the inside to the outside, and the peripheral blastholes (auxiliary hole 4, peripheral hole 5) need to overcome greater rock resistance. Increasing the total charge can compensate for energy loss and ensure sufficient crushing; the single-stage charge decreases from the inside to the outside. Combined with interval detonation, the single-stage charge decreases from the inside to the outside to avoid vibration superposition caused by local energy concentration and reduce the peak vibration velocity (PPV). For example, the reduction of the single-stage charge of peripheral hole 5 can reduce the impact on the surrounding rock and protect the integrity of the contour surface. By separating the detonation of different sections with micro-difference time (such as 25-75ms), the blasting vibration wave propagates at different peaks, further weakening the vibration energy superposition effect.

[0068] Third, the rock crushing effect and blasting economy are improved

[0069] The rock mass in the excavation area has a strong clamping effect, but by accurately controlling the total charge (avoiding over-charging) and combining the timing advantage of interval detonation, the initial free surface can be efficiently formed to reduce energy waste; the total charge of the expansion hole 3 and the auxiliary hole 4 is gradually increased to match the resistance gradient of the rock mass from the inside to the outside, ensuring the dynamic balance between the blasting energy and the rock crushing demand, and reducing the large block rate; the peripheral hole 5 has the largest total charge, but the single-stage charge is reduced. Uniform energy distribution is achieved through the "multi-hole and less charge" mode, combined with the smooth blasting technology to form a flat contour surface and reduce over-excavation and secondary processing costs.

[0070] Fourth, structural safety and construction controllability

[0071] The main function of the slot hole 2 is to "break the rock" with precise charge dosage; the main function of the auxiliary hole 4 is to "expand the cavity" with appropriate charge dosage; the main function of the peripheral hole 5 is to "shape" with fine charge dosage. The functional requirements of different blastholes are specifically met through charge gradient design.

[0072] Use electronic detonators or high-precision detonating cord detonators, and detonate strictly according to the designed sequence to avoid energy conflicts caused by early or late explosions. For example, after the excavation hole 2 is detonated, the expansion hole 3 is detonated when the rock mass begins to move but has not completely detached, using kinetic energy superposition to improve the throwing efficiency.

[0073] The expected blasting effect of this case is shown in the following table:

[0074] Table 2 Expected effect of one-step well completion by suspended charge segmented blasting

[0075]

[0076] In summary, the blasting method in this embodiment achieves the following core advantages through the gradient distribution of "total charge increasing from inside to outside + single-stage charge decreasing" combined with interval detonation technology: matching energy release with rock resistance to improve blasting efficiency; precise control of vibration and destruction to ensure project safety; optimization of contour surface forming quality to reduce later support costs; systematic design of blasting parameters to enhance construction controllability.

[0077] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third" and the like are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0078] In the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0079] If the present invention discloses or involves components or structures that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (for example, connection using bolts or screws), and can also be understood as: a non-detachable fixed connection (for example, riveting, welding). Of course, the mutual fixed connection can also be replaced by an integrated structure (for example, manufactured by one-piece molding using a casting process) (except when it is obviously impossible to use an one-piece molding process).

[0080] In addition, unless otherwise stated, the terms used to indicate positional relationships or shapes in any technical solution disclosed in the present invention include states or shapes that are approximate, similar, or close thereto.

[0081] Any component provided by the present invention may be assembled from a plurality of separate components, or may be a separate component manufactured by an integral forming process.

[0082] It should be noted that the structures, proportions, sizes, etc. depicted in the drawings of this specification are only used to match the contents disclosed in the specification so that people familiar with this technology can understand and read them. They are not used to limit the conditions under which the present invention can be implemented. Therefore, they have no substantive technical significance. Any modification of the structure, change in the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0083] It should also be noted that in the embodiments of the present application, the same figure mark is used to represent the same component or the same part.

[0084] Adaptive changes made according to actual needs are all within the protection scope of the present invention.

[0085] It should be noted that it is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-restrictive from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any reference numerals in the claims should not be regarded as limiting the claims involved.

[0086] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for blasting a shallow shaft with a small or medium cross section at the top of a tunnel, characterized in that: The following steps are involved: S1, reverse drilling, drilling a full-depth blast hole from bottom to top in the tunnel, the blast hole is connected to the outside of the upper part of the tunnel; S2, suspending multiple sections of explosives covering the entire well depth from one end of the blasthole connected to the outside world; S3. Detonating the multiple sections of explosives in sequence from bottom to top.

2. The blasting method for small and medium-section shallow shafts at the top of a tunnel according to claim 1, characterized in that: In step S1, the blasthole includes a center eye, a grooved eye, an expanded groove eye, an auxiliary eye and a peripheral eye, the grooved eye is arranged along a first circular trajectory, the expanded groove eye is arranged along a second circular trajectory, the auxiliary eye is arranged along a third circular trajectory, and the peripheral eye is arranged along a fourth circular trajectory, and the radii of the first circular trajectory, the second circular trajectory, the third circular trajectory and the fourth circular trajectory increase in sequence, and all have the center eye as the center.

3. The blasting method for a shallow shaft with a small or medium cross section at the top of a tunnel according to claim 2, characterized in that: In step S2, the amount of each section of explosive suspended in the same blasthole is the same.

4. The blasting method for a shallow shaft with a small or medium cross section at the top of a tunnel according to claim 3, characterized in that: In the step S2, the number of sections of explosives arranged in the cut holes, the expanded holes, the auxiliary holes and the peripheral holes is the same, and the heights of each section of explosives correspond to each other.

5. The blasting method for small and medium-section shallow shafts at the top of a tunnel according to claim 4, characterized in that: In the step S1, the number of the cut holes, expanded holes, auxiliary holes and peripheral holes increases in sequence.

6. The blasting method for small and medium-section shallow shafts at the top of a tunnel according to claim 5, characterized in that: In the step S2, the amount of explosives in the same section of the cut hole, the expanded hole, the auxiliary hole and the peripheral hole arranged from the inside to the outside is reduced in sequence with the central hole as the center of the circle.

7. The blasting method for small and medium-section shallow shafts at the top of a tunnel according to claim 6, characterized in that: In step S2, the total amount of explosives in all the cut holes is less than the total amount of explosives in all the expanded holes, the total amount of explosives in all the expanded holes is less than the total amount of explosives in all the auxiliary holes, and the total amount of explosives in all the auxiliary holes is less than the total amount of explosives in all the peripheral holes.

8. The blasting method for small and medium-section shallow shafts at the top of a tunnel according to claim 7, characterized in that: In step S3, the explosives in the cut hole, the expanded hole, the auxiliary hole and the peripheral hole are detonated in sequence and at intervals.

9. The blasting method for a shallow shaft with a small or medium cross section at the top of a tunnel according to any one of claims 1 to 8, characterized in that: In step S2, the staff at the top outside the tunnel lowers the explosive installation belt from the end of the blasthole connected to the outside world. After the staff inside the tunnel receives it, they install the explosives on the explosive installation belt in sections. After installation, the staff at the top outside the tunnel pulls the explosive installation belt upward until the explosives reach the specified height.

10. The blasting method for a shallow shaft with a small or medium cross section at the top of a tunnel according to any one of claims 1 to 8, characterized in that: In step S3, digital electronic detonators are used to achieve millisecond-level delayed detonation.

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