WO2022198841A1 - Flying-limiting hole drilling and blasting method for controlling flying stones in tunnel blasting - Google Patents

Abstract

Disclosed is a flying-limiting hole drilling and blasting method for controlling flying stones in tunnel blasting. The method comprises: excavating a flying-limiting hole having an advanced tunneling section at a lower portion of the tunneling section, and setting, under different surrounding rock conditions, the relationship between the excavation depth of the flying-limiting hole and the blasting circulation footage of the advanced tunneling section and the tunneling section of a tunnel; in addition, setting a detonation time, such that rock slag blasted from a blast hole firstly detonated in the tunneling section of the tunnel under hard surrounding rock conditions can form a slag pile in the flying-limiting hole and can effectively block flying stones thrown outwards by blasting in the advanced tunneling section. Therefore, under weak surrounding rock conditions, the advanced tunneling section is blasted in advance, and a good free surface is created for blasting of the tunneling section of the tunnel. In the present invention, a flying-limiting hole is excavated once for the first time, a new flying-limiting hole is actively formed after each cycle, and blasting construction of the next cycle can be continuously performed, such that the working efficiency is improved again, and a feasible way is provided for efficient and safe construction of a tunnel.

Description

A method of limiting flying hole drilling and blasting for controlling flying rocks in tunnel blasting technical field

The invention belongs to the field of underground engineering blasting construction, in particular to a method for limiting flying hole drilling and blasting for controlling blasting flying stones during tunnel excavation blasting construction.

Background technique

In the process of tunnel excavation, in order to improve the blasting efficiency, it is often necessary to increase the amount of charge at the cutting part to achieve a good blasting effect. The throwing distance of flying stones produced by conventional cutting and blasting methods is usually 20~30m from the working face, and individual flying stones can reach 40m. Blasting the flying stones will cause serious damage to the equipment and facilities near the excavation face. In the process of tunnel excavation, in order to find out the geological conditions in front of the excavation working face, speed up the construction progress, and improve the safety in the process of tunnel excavation, the method of excavating advanced pilot holes is often used for the subsequent tunnel excavation. Construction to create good construction conditions. 

In the tunneling construction of coal mines, in order to improve the mechanization level of drilling and blasting in rock tunnel excavation, drilling, loading and transporting integrated machines have been used in the tunneling construction. Due to the structural characteristics of this type of integrated machine, the head of the integrated machine can only be withdrawn to a position 15~20m away from the excavation face during blasting. In order to avoid the damage of blasting flying stones to the head of the integrated machine, it is necessary to set up multiple protective facilities between the excavation face and the head, which increases the construction process, construction cost and reduces the construction efficiency. Even if protective facilities are added, it is difficult to eliminate the damage of blasting flying stones to the nose of the integrated machine. Therefore, it is necessary to develop a more reasonable blasting method to effectively reduce the throwing distance of blasting flying stones, control the shape of the blasting pile, and reduce the damage of blasting flying stones to the integrated machine.

"Protection against flying rocks during blasting of hydraulic tunnels" (Song Yu, Heilongjiang Water Conservancy Science and Technology, 2019, Vol. 47, No. 08, pp. 150-152) proposes that "for large equipment that is inconvenient to evacuate in the site, use rubber Soft pads, cotton pads, or heavy branches and other protective equipment that play a buffering role cover it to reduce the kinetic energy of flying stones and effectively protect against flying stones, which can effectively reduce the damage rate of equipment.” This method of strengthening coverage and shielding belongs to passive protection, with high cost, many processes and high labor intensity. Protective operations do not contribute to the driving footage, and have high requirements on the carrying capacity and quality of protective equipment, and cannot completely avoid the damage to equipment caused by flying rocks.

Chinese patent CN201310534938.7 discloses a comprehensive shock absorption method for blasting a tunnel under cultural protection buildings. Although this patent adopts the excavation method of a super-leading hole, its purpose is to control the blasting vibration speed, and it does not affect the blasting flying stones, especially the super-leading holes. The throwing direction, throwing distance and throwing range of the hole blasting flying stones are effectively controlled.

Chinese Patent Publication No. CN107218043 A discloses a method for excavating a broken surrounding rock cavern, which is characterized in that the pilot hole is excavated at the lower position in the middle of the main cave, and the small pilot hole is excavated by pneumatic drilling and blasting, and a cycle footage is excavated; The hole is expanded and excavated, and the explosions are sequentially initiated from the center of the hole to the surrounding holes, and the slag is discharged; the main hole is supported. In essence, the patent adopts the split-section method for construction, and does not form a pilot hole for advancing the working face. The existing problems are: (1) During the drilling and blasting excavation process, the throwing direction, throwing distance and throwing range of the blasting flying stones, especially the pilot hole blasting flying stones, cannot be effectively controlled, and the impact of blasting flying stones on the working face cannot be effectively controlled. The problem of damage caused by nearby equipment and facilities. (2) The pilot tunnel is excavated simultaneously with the excavation face, and no advanced face is formed. The shape of the ballast pile in the step of "excavation of the pilot hole" in Figure 1 of the invention patent does not match the actual project. In the actual project, the rock slag from the blasting of the pilot tunnel will be scattered on both sides of the blasting section of the pilot tunnel, and the lower part of the unblasted working face on both sides will be buried. The follow-up procedures on the working faces on both sides of the pilot tunnel, such as drilling, charging, wiring, detonation, etc., must be carried out after removing these rock slag, which greatly reduces the construction efficiency.

Chinese Patent Publication No. CN102758633 B discloses a construction method for a large-section tunnel with better surrounding rock conditions. This method does not effectively carry out the throwing direction, throwing distance and throwing range of the blasting flying stones, especially the blasting flying stones of advanced pilot holes. Control, can not solve the problem of blasting flying stone damage to the equipment and facilities near the working face.

Chinese Patent Publication No. CN106089216A discloses a rock-breaking construction method for a rock tunnel: a pilot hole of a certain depth is excavated in the section of the tunnel being constructed by mechanical rock-breaking along the advancing direction of the tunnel excavation being constructed; the surface of the pilot hole is The free surface is blasted, and the section of the pilot hole is excavated. The invention patent solves the problem of blasting a large number of flying stones and damaging equipment and facilities during the drilling and blasting excavation process of rock tunnels through the method of mechanical rock breaking and excavating advanced pilot holes. However, there are the following problems: (1) Compared with the drilling and blasting method, the mechanical rock breaking method used in the excavation of the advanced pilot hole has a slower excavation speed, many processes and high equipment cost. (2) According to claims 1 to 5 of the invention patent, in order to provide a good free surface for the rock to be excavated, the mechanical rock breaking method is used to excavate the advanced pilot hole, and the excavation depth is at least 1 step of drilling and blasting the rock. length, and the headroom cannot be shortened further. When the surrounding rock conditions are poor, the roof of the advanced excavation site has the safety protection problem of collapse and falling blocks. If support is added, such as bolt support and shotcrete support, it will lead to low construction efficiency and increased cost.

All in all, the prior art generally has the following three technical problems: (1) The existing tunnel blasting method cannot actively carry out effective blasting of flying stones, especially the throwing direction, throwing distance and throwing range of blasting flying stones in advanced pilot holes. ground control. It cannot solve the problem that the blasting flying stones thrown along the axis of the tunnel or the pilot hole cause damage to the equipment in the tunnel. (2) For the split-section method, the rock slag from the first blasting section (pilot tunnel) will be scattered on both sides of the blasting section, and the lower part of the unblasted working face on both sides will be buried. The follow-up procedures on the working faces on both sides of the pilot tunnel, such as drilling, charging, wiring, detonation, etc., must be carried out after removing the rock slag. The construction efficiency is greatly reduced. (3) Under the condition of weak surrounding rock, the roof safety problem caused by the advanced pilot hole.

technical solutions

In order to solve the technical problems existing in the existing blasting technology, effectively control the throwing direction, throwing distance and throwing range of the blasting flying stones, avoid the damage of the flying stones to the equipment of the driving face, and further improve the construction efficiency and ensure the construction safety, the present invention proposes a A method for limiting flying hole drilling and blasting for controlling flying rock blasting in tunnels.

The present invention adopts different technical measures for different surrounding rock conditions. Specifically, different blasting methods are adopted for tunnels with hard and weak surrounding rock conditions.

In order to achieve the above object, the technical scheme that the present invention takes is:

A method for limiting flying hole drilling and blasting for controlling the blasting of flying stones in tunnels, comprising the following steps

S1. Excavate a fly-limiting hole with a width a, height b, and depth L at the lower part of the tunnel excavation section to be excavated, and form an advanced excavation section in the fly-limiting hole. In principle, the height and width of the fly-limiting hole exceed The smaller the better, in addition to the operator and drill boom being able to enter, the shovel head of the ballast removal equipment should also be able to enter the hole for ballast removal;

S2. Set the blasting cycle footage L ₁ and L ₂ of the tunnel excavation section and the advance excavation section according to the site conditions, and drill the blast holes on the tunnel excavation section and the advance excavation section respectively, and limit the excavation depth L of the fly hole and the tunnel. The following relationship is satisfied between the blasting cycle footage L ₁ and L ₂ of the driving section and the advanced driving section:

When the surrounding rock of the tunnel to be excavated is hard surrounding rock, L=L ₁ +(0.5~1.5)L ₂ is required;

When the surrounding rock condition of the tunnel to be excavated is weak surrounding rock, L=(0.3~1.0)L ₁ , L ₂ ≥L ₁ , and a ballast pile shall be set between the opening of the fly-limiting tunnel and the equipment of the excavation face. Or the ballast plate, the purpose is to protect the equipment, and to leave a stacking space for the blasting flying stones thrown from the advanced driving section;

S3. Loading explosives and detonators into the blastholes in the tunnelling section and the advance section;

S4. Set the initiation time according to the surrounding rock conditions;

When the surrounding rock condition of the tunnel to be excavated is hard surrounding rock, the principle of setting the blasting time is: first, let the blasting hole of the tunnel excavation section along the excavation outline of the fly-limiting hole detonate, so that the rock blasted from the blasting hole first can be detonated in the fly-limiting tunnel. A ballast pile is formed in the hole, which can effectively block the flying stones thrown out by the blasting of the advanced driving section, and the other blasting holes are detonated sequentially from the inside to the outside;

When the surrounding rock of the tunnel to be excavated is weak surrounding rock, the principle of setting the detonation time is as follows: firstly let all the blastholes on the advanced excavation section detonate, and then detonate the blastholes in the tunnel excavation section, so as to detonate the tunnel excavation section. When , the fly-limiting hole creates a good free surface for the blasting of the tunneling section;

S5. Detonate the tunnel excavation section and the blast hole in the advance excavation section according to the detonation time set in S4;

S6. Remove the blasted rock slag to form a new tunneling section and a new fly-limiting hole, and the new fly-limiting hole section is used as a new advance driving section;

S7. Repeat steps S2~S6 to start a new cycle of tunnel excavation.

In order to meet the requirement that the height and width of the fly-restricting hole should be as small as possible in principle, it is convenient to drill the blasthole on the small-sized advanced excavation section, and to promote the blasted gravel to fall into the center of the advanced excavation section. Hollow hole straight hole cutting method, the relationship between the center distance t of the expanded slot and the hollow hole, the diameter of the hollow hole d ₁ , and the diameter of the expanded slot d ₂ satisfies the relationship: t=(1.5~3.0)d ₁ +0.5d ₂ , where d ₁ ≥75mm, d ₂ ≤60mm.

Further, in order to better protect equipment and block blasting flying stones, the height H of the ballast stack or the ballast plate is greater than or equal to the maximum distance h between the reaming slot and the tunnel floor, and the width W of the ballast stack is greater than or equal to the limit. The width of the fly hole a.

In order to further improve the safety of pilot tunnel construction with weak surrounding rock conditions, one or several protective benches with cross-sectional dimensions suitable for the fly-limited tunnel can be arranged in the tunnel when personnel enter the fly-limited tunnel. Due to the small size of the fly-limiting hole and the small size of the bench, the bench can be transported to a safe position by manpower or machinery when personnel are evacuated.

beneficial effect

The advantages of the present invention will be explained one by one according to the mechanism below.

1. the present invention excavates a fly-limiting hole of an advanced section at the bottom of the tunnel driving section, and the excavation working face of the fly-limiting hole is an advanced-heading section, and the wall of the fly-limiting hole limits the blasting flystone of the forward-moving section only along the Throwing in the direction of the axis of the fly hole is limited. The blasted rock ballast will not fill the unblasted working face outside the outline of the restricted fly hole.

2. The greater the advanced excavation depth L of the fly-limiting hole, the better the control effect on the throwing direction and throwing range of flying stones. However, as the excavation depth L increases, problems such as roof safety, drilling of blast holes, and transportation of ballast will arise. The invention proposes the relationship between the advance excavation depth L of the fly-limiting tunnel and the tunnel excavation section and the blasting cycle footage L ₁ and L ₂ of the advance excavation section, which solves the problems of blasting fly stone control and roof safety.

3. Under the condition of hard surrounding rock, the relationship L _{=L 1 + (} 0.5~1.5) L ₂ . The fly-limiting hole creates a good blasting free surface for the tunnel excavation section. Tunneling The minimum resistance line of the blasthole on the tunnel driving section points to the direction of the flying-limiting hole, and the blasting flying stones are mainly thrown along the direction of the minimum resistance line (that is, the direction perpendicular to the tunnel axis), so as to throw the blasting flying stones in the direction of the blasting flying stone in the tunnel driving section, throwing The distance and throwing range are effectively controlled, so that they are concentrated near the working face, eliminating the hidden danger of blasting flying stones on the tunnel excavation section to damage the equipment such as the integrated machine in front of the working face.

4. Under the condition of hard surrounding rock, the delay time of the blasthole detonator along the excavation contour of the fly-limiting hole on the tunnel excavation section is less than the minimum delay time of the detonator on the advanced excavation section, so that the blasthole detonator along the excavation contour of the fly-limiting hole on the tunnel excavation section is first. Detonation, the blasted rock can form a ballast pile in the restricted fly hole and can effectively block the flying rock thrown outward by the blasting of the advance tunneling section, so as to effectively control the throwing direction, throwing distance and throwing range of the blasting flying rock in the advance tunneling section. control so that they are concentrated in the fly-limiting hole. In addition, the rock slag produced by the blasting hole after the tunnel excavation section and the exploding rock slag in the advanced excavation section squeeze and collide with each other. While changing the throwing direction of the rock slag in the advanced excavation section, it effectively reduces the size of the rock slag, which is convenient and convenient. Ballast shipment.

5. Under the condition of hard surrounding rock, satisfying the relationship L=L ₁ + (0.5~1.5) L ₂ ensures that there is a hole content with a length of (0.5~1.5) L ₂ between the advanced driving section and the ballast pile in the hole Expansion space is provided to provide enough expansion space for the flying stones thrown from the advanced excavation section to ensure the blasting effect of the advanced excavation section.

6. Under the condition of weak surrounding rock, L, L ₁ and L ₂ satisfy the relationship L=(0.3~1.0)L ₁ , L ₂ ≥L ₁ . Under this condition, although there is no good blasting free surface prepared for the tunnel excavation section in the fly-restricting hole, in this case, the empty head distance of the advanced excavation section is small, the drilling and charging operations are relatively safe, no support or only simple It is especially suitable for the operation of large drilling equipment with short drill boom and high requirements on construction area. The excavation depth of the fly-restricting hole is at least 0.3L ₁ , which restricts the throwing direction of the flying rocks in the blasting section of the advance tunneling section and can only be thrown along the axis of the fly-restricting cave. the lower part of the working face.

7. Under the condition of weak surrounding rock, a ballast pile or a ballast plate shall be set in the relative position in front of the fly-limiting hole and the hole, and the minimum delay time of the detonator on the tunnel driving section is greater than the maximum delay time of the detonator on the advanced driving section, so that the advanced driving The section is blasted first, providing a good blasting free surface for the tunneling section, and the blasting flying stones are blocked by the ballast pile or the ballast plate, which limits the throwing direction, throwing distance and throwing range, so that the blasted rock ballast is piled up in a concentrated manner. Between the tunneling section and the ballast stack or the ballast plate. For the case of using the permitted electric detonators in coal mines, since the number of detonator sections is only 5, the advance driving section and the tunnel driving section can be detonated in two times. For the condition that the number of available detonator segments meets the requirements, the advance driving section and the tunnel driving section can be detonated at the same time, and the minimum delay time of the detonator on the tunnel driving section is greater than the maximum delay time of the detonator on the advanced driving section.

8. The hollow-hole straight-hole cutting method in the advance driving section creates conditions for reducing the section size of the fly-restricting hole, so that the flying range of blasting flying stones can be controlled more effectively. The relationship between the center distance t of the reamed hole and the hollow hole, the diameter of the hollow hole d ₁ and the diameter of the reamed hole d ₂ satisfies the relationship t=(1.5~3.0)d ₁ +0.5d ₂ , where d ₁ ≥75mm, d ₂ ≤60mm , which can ensure the blasting effect of the expanded slot hole.

For a long time, improving the efficiency of tunnel excavation construction under the premise of ensuring safety is the goal pursued by those skilled in the art. However, in reality, safe construction and efficient construction are a pair of contradictory bodies, and they often lose sight of one another. For fly-limiting holes, by setting the initiation time and using blasting technology to excavate tunnels, the construction efficiency is improved and the flying rocks are effectively prevented; The relationship between the three cycle footage also ensures that a new fly-limiting hole is actively formed after each blasting, so that the excavation of a fly-limiting hole can continue the blasting construction of the next cycle, which improves the work efficiency again. It provides a feasible way for efficient and safe tunnel construction, and has significant economic significance.

Description of drawings

Fig. 1 is a schematic diagram of drill-and-blast excavation of a working face under the condition of hard surrounding rock in Example 1.

FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1 .

Fig. 3 is a schematic diagram of the instantaneous effect after the blasting of the blast hole in which section 1 is detonated prior to section 2 under the condition of hard surrounding rock in Example 1.

Fig. 4 is a schematic diagram of the effect after detonation of all blast holes on section 1 and section 2 under the condition of hard surrounding rock in Example 1.

Fig. 5 is a schematic diagram of drilling and blasting excavation of the working face under the condition of weak surrounding rock in the second embodiment.

FIG. 6 is a cross-sectional view taken along line A-A of FIG. 5 .

FIG. 7 is a view taken along the line B of FIG. 5 .

Fig. 8 is a schematic diagram of the instant effect after the blasting of the blast hole on section 2 under the condition of weak surrounding rock in Example 2.

Fig. 9 is a schematic diagram of the effect after detonation of all blast holes on Section 1 and Section 2 under the condition of weak surrounding rock in Example 2.

Symbols ①, ②, ③, ④, and ⑤ in Fig. 2 and Fig. 6 represent detonator segment numbers, corresponding to 1, 2, 3, 4, and 5 segments of detonators, respectively.

In the figure: 1- tunnel excavation section; 2- advanced excavation section; 3- reaming hole; 4- hollow hole; 5- auxiliary hole in advanced excavation section; 6- peripheral hole in advanced excavation section; 7- auxiliary hole in tunnel excavation section; 8- Peripheral hole of tunnel excavation section; 9- Drilling and shipping integrated machine; 10- Air duct; 11- Ballast block; 12- First ballast pile; 13- Second ballast pile; 14- Third ballast pile; 15- No. Four ballast piles.

Embodiments of the present invention

Example 1

Embodiment 1 is an example of using the drilling and blasting method of the present invention when excavating a tunnel under the condition of hard surrounding rock. It is implemented in the blasting and excavation construction process of the second auxiliary transportation roadway in the north of a coal mine. The basic conditions of the excavation working face are: the excavation height of the working face. 5.2m, the excavation width is 4.5m, and the excavation area is 19.7m ² . The three-level water-gel explosive that is permitted in coal mines is used, and its working force is 220ml, the detonation speed is 3000m/s, and the intensity is 10mm. The medicine roll has a diameter of 35mm, a length of 40cm, and a mass of 400g/roll. The drilling and shipping integrated machine 9 has a drill pipe length of 2.5m, a maximum drill hole length of 2.3m, and a drill hole diameter of 42mm. 1~5 sections of coal mine allowable electric detonators are used. Before blasting, the integrated drilling and shipping machine was withdrawn to a distance of 15.0m from the excavation working face, and parked on the left side of the roadway facing the working face, and the right side was the passage for pedestrians and equipment.

The excavation steps are:

Step 1: Use a crawler drill to drill a hollow hole 4 at the center of the lower part of the tunneling section 1. The depth of the hollow hole 4 is 20m, the diameter is 133mm, and the height from the bottom plate is h=0.7m. Around the hollow hole 4, a fly-restricting hole with a width of 1.6m and a height of 1.6m is excavated in advance at the center of the lower part of the tunnel excavation section 1 to form the advanced excavation section 2. The footage length L ₁ of a single cycle of tunnel driving section 1 is 1.8m, and the footage L ₂ of a single cycle of advance driving section 2 is 1.8m. The depth L of the fly-limiting hole is taken as the sum of the footage L1 of a single cycle of tunnel driving section ₁ and the footage L2 of a single cycle of advance driving section 2, that is, L=L ₁ +L ₂ =3.6m. The positional relationship between the tunneling section 1 and the advance driving section 2 is shown in FIG. 1 .

Step 2: Use the drilling and shipping integrated machine 9 to drill the blastholes on the tunneling section 1 and the advanced driving section 2 respectively. Four reaming holes 3 are arranged around the hollow hole 4 on the advanced excavation section 2, and the distance between the center of the hollow hole 4 and the reaming hole 3 is t=240mm. The auxiliary holes 5 of the advanced driving section are arranged layer by layer from the inside to the outside, and the peripheral holes 6 of the advanced driving section are evenly arranged along the excavation contour of the fly-limiting hole. The auxiliary holes 7 of the tunnel driving section are arranged layer by layer from the excavation outline of the fly-limiting hole to the outside, and the peripheral holes 8 of the tunnel driving section are evenly arranged along the design contour of the driving face, as shown in Figure 2.

Step 3: Load explosives and detonators into the blastholes of the tunneling section 1 and the advanced driving section 2.

Step 4: Set the detonation time. On the tunneling section 1, the circle of auxiliary holes closest to the advanced driving section 2 shall use the first section of electric detonators permitted by coal mines, and then the blastholes from the excavation profile of the fly-limiting hole to the excavation profile of the roadway shall use the detonator sections 2, 3, and 3 respectively. 4 and 5 paragraphs. The detonators used in the blastholes on the advanced tunneling section 2 are 2, 3, 4, and 5, respectively. As shown in Figure 2, the detonator numbers of 1, 2, 3, 4, and 5 are ① and ② in the figure respectively. , ③, ④, ⑤.

Step 5: Simultaneously detonate the detonators in the blastholes on the tunneling section 1 and the advance driving section 2. The tunneling section 1 is detonated before the first section of the detonator detonated in the leading section 2 to form a first ballast pile 12 , the shape of which is shown in FIG. 3 . After all the blasting holes on the tunneling section 1 and the advanced excavation section 2 are fully detonated, a first ballast pile 12 and a second ballast pile 13 are formed, the shapes of which are shown in FIG. 4 . After blasting, the blower is turned on, and the blower 10 sends fresh airflow to the working face to remove harmful gases such as dust and gun smoke.

Step 6: Remove the blasted rock slag to form a new tunneling section, a fly-limiting hole and an advanced driving section.

Step 7: Repeat steps 2 to 6 to start a new cycle of tunnel excavation until the tunnel excavation is completed.

Embodiment 2

The second embodiment is an example of using the drill and blast method of the present invention under the condition of soft surrounding rock.

The excavation steps are:

Step 1: Use a crawler drill to drill a hollow hole 4 at the center of the lower part of the tunneling section 1. The depth of the hollow hole 4 is 20m, the diameter is 133mm, and the height from the bottom plate is h=0.7m. Around the hollow hole 4, a fly-restricting hole with a width of 1.6m and a height of 1.6m is excavated in advance at the center of the lower part of the tunnel excavation section 1 to form the advanced excavation section 2. The footage length L ₁ of a single cycle of tunnel driving section 1 is 1.8m, and the footage L ₂ of a single cycle of advance driving section 2 is 2.0m. The depth L of the fly-limiting hole is taken as half of the single cycle footage L ₁ of the tunnel excavation section 1, that is, L=0.5L ₁ =0.9m. Figure 5 shows the positional relationship between the tunnel excavation section 1 and the advance excavation section 2.

Step 2: Use the drilling and shipping integrated machine 9 to drill the blastholes on the tunneling section 1 and the advanced driving section 2 respectively. Four reaming holes 3 are arranged around the hollow hole 4 on the advanced excavation section 2, and the distance between the center of the hollow hole 4 and the reaming hole 3 is t=240mm. The auxiliary holes 5 of the advanced driving section are arranged layer by layer from the inside to the outside, and the peripheral holes 6 of the advanced driving section are evenly arranged along the excavation contour of the fly-limiting hole. The auxiliary holes 7 of the tunnel driving section are arranged layer by layer from the excavation outline of the fly-limiting hole to the outside, and the peripheral holes 8 of the tunnel driving section are evenly arranged along the design outline of the driving face, as shown in Figure 6.

Step 3: Set the ballast stack 11 in front of the fly-limiting hole relative to the hole. A ballast stack 11 is set between the fly-limiting hole and the well equipment, and the distance S between the ballast stack 11 and the fly-limit hole is 3.5m. The height H of the ballast stack 11 is 1.0m, which is 0.94m higher than the height of the bottom plate of the reaming hole in the upper part of the hollow hole, and the width W is 2.0m, which is 1.6m larger than the width of the fly-restricting hole. The material of the ballast retaining pile 11 is rock ballast that has been exploded in the roadway, as shown in FIG. 5 and FIG. 7 .

Step 4: Load explosives and detonators into the blastholes of tunneling section 1 and advance driving section 2.

Step 5: Set the detonation time. On the tunneling section 1, the circle of auxiliary holes closest to the advanced driving section 2 shall use the first section of electric detonators permitted by coal mines, and then the blastholes from the excavation profile of the fly-limiting hole to the excavation profile of the roadway shall use the detonator sections 2, 3, and 3 respectively. 4 and 5 paragraphs. Sections 1, 2, 3, 4, and 5 using detonators from the inside to the outside of the blasthole on the advanced tunneling section 2 are respectively. As shown in Figure 6.

Step 6: The blasting holes on the tunneling section 1 and the advance driving section 2 are detonated in two times. First detonate the blast hole on the advanced excavation section 2, and then detonate the blast hole in the tunnel excavation section 1. The third ballast pile 14 is formed after the blasting of the blasthole on the advance tunneling section 2, the shape of which is shown in FIG. 8 . The third ballast pile 14 and the fourth ballast pile 15 are formed after all the blasting holes on the tunneling section 1 and the advanced driving section 2 are detonated, the shapes of which are shown in FIG. 9 . After blasting, the blower is turned on, and the blower 10 sends fresh airflow to the working face to remove harmful gases such as dust and gun smoke.

Step 7: Remove the blasted rock slag to form a new tunneling section, a fly-limiting hole and an advanced driving section.

Step 8: Repeat steps 2 to 7 to start a new cycle of tunnel excavation until the tunnel excavation is completed.

Definitions of Key Terms of the Invention

(1) Slot expansion hole: a circle of charging holes arranged around the hollow hole, with equal spacing between adjacent holes and the closest distance to the hollow hole.

(2) Split-section method, which divides the tunnel excavation section into two or more blasting sections, and completes a tunneling cycle by blasting rocks on different sections in stages.

(3) The bottom plate, the bottom profile surface of tunnel excavation, is a plane parallel to the tunnel axis.

(4) The volume expansion space, considering the rock fragmentation expansion coefficient, provides the accumulation space for the rock exploded in the advanced pilot hole.

(5) Electric detonators permitted for use in coal mines, approved by the competent authorities, are permitted to be used in underground coal mines where there is a danger of gas and (or) coal dust explosion. There are only 5 delay sections for the permitted electric detonators in coal mines, and the delay times are 0ms, 25ms, 50ms, 75ms, and 100ms respectively.

Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. In the above embodiment, the selection of detonators and the design of blast holes are based on the geological and size data of the coal mine and are given according to the technical solution of the present invention. In addition, the design of the fly-limiting hole in the embodiment as a rectangle is based on the consideration of convenience for drawing, and is not a limitation to the technical solution of the present invention. In practice, for different tunnels, those skilled in the art are based on their own Professional knowledge can be completely designed under the guidance of the technical solution of the present invention, so the protection scope of the present invention is subject to the description in the claims.

Claims (4)

1. A method for limiting flying hole drilling and blasting for controlling the blasting of flying stones in tunnels, comprising the following steps

   S1. Excavate a fly-limiting hole with a width a, height b, and depth L at the lower part of the tunnel excavation section to be excavated, and form an advanced excavation section in the fly-limiting hole. In principle, the height and width of the fly-limiting hole exceed The smaller the better, in addition to the operator and drill boom being able to enter, the shovel head of the ballast removal equipment should also be able to enter the hole for ballast removal;

   S2. Set the blasting cycle footage L ₁ and L ₂ of the tunnel excavation section and the advance excavation section according to the site conditions, and drill the blast holes on the tunnel excavation section and the advance excavation section respectively, and limit the excavation depth L of the fly hole and the tunnel. The following relationship is satisfied between the blasting cycle footage L ₁ and L ₂ of the driving section and the advanced driving section:

   When the surrounding rock of the tunnel to be excavated is hard surrounding rock, L=L ₁ +(0.5~1.5)L ₂ is required;

   When the surrounding rock condition of the tunnel to be excavated is weak surrounding rock, L=(0.3~1.0)L ₁ , L ₂ ≥L1, and a ballast pile or a ballast pile is set between the opening of the fly-limiting tunnel and the equipment of the excavation face. The purpose of the ballast plate is to protect the equipment first, and to leave a stacking space for the blasting flying stones thrown from the advanced driving section;

   S3. Loading explosives and detonators into the blastholes in the tunnelling section and the advance section;

   S4. Set the initiation time according to the surrounding rock conditions:

   When the surrounding rock condition of the tunnel to be excavated is hard surrounding rock, the principle of setting the blasting time is: first, let the blasting hole of the tunnel excavation section along the excavation outline of the fly-limiting hole detonate, so that the rock blasted from the blasting hole first can be detonated in the fly-limiting tunnel. A ballast pile is formed in the hole, which can effectively block the flying stones thrown out by the blasting of the advanced driving section, and the other blasting holes are detonated sequentially from the inside to the outside;

   When the surrounding rock of the tunnel to be excavated is weak surrounding rock, the principle of setting the detonation time is as follows: firstly let all the blastholes on the advanced excavation section detonate, and then detonate the blastholes in the tunnel excavation section, so as to detonate the tunnel excavation section. When , the fly-limiting hole creates a good free surface for the blasting of the tunneling section;

   S5. Detonate the tunnel excavation section and the blast hole in the advance excavation section according to the detonation time set in S4;

   S6. Remove the blasted rock slag to form a new tunneling section and a new fly-limiting hole, and the new fly-limiting hole section is used as a new advance driving section;

   S7. Repeat steps S2~S6 to start a new cycle of tunnel excavation.
2. The method for limiting fly-hole drilling and blasting for controlling flying rocks in tunnel blasting as claimed in claim 1, characterized in that, the advanced excavation section adopts a hollow hole straight-hole cutting method, and the distance t between the reaming hole and the center of the hollow hole is the same as that of the hollow hole. The relationship between the hole diameter d ₁ and the reaming hole diameter d ₂ is satisfied: t=(1.5~3.0)d ₁ +0.5d ₂ , where d ₁ ≥75mm, d ₂ ≤60mm.
3. The method for limiting fly-hole drilling and blasting for controlling flying rocks in tunnel blasting according to claim 1 or 2, wherein the height H of the ballast stack or the ballast plate is greater than or equal to the gap between the reaming slot and the tunnel floor The maximum distance h, the width W of the ballast stack or the ballast plate is greater than the width a of the limit fly hole.
4. The fly-restricting hole drilling and blasting method for controlling the blasting of flying rocks in a tunnel according to claim 1, characterized in that, when artificially drilling a blast hole in a fly-restricting hole in a soft surrounding rock, one or more sections are arranged in the fly-restricting hole. A protective bench whose size is compatible with the section size of the fly-limiting hole.