WO2022198842A1 - Hollow-hole burn cut three-time blasting method - Google Patents

Abstract

Disclosed in the present invention is a hollow-hole burn cut three-time blasting method. In the method, a pilot tunnel is excavated on one side of the centerline of a tunneling section and in a direction where there is no target to be protected on a working face; the pilot tunnel divides the tunneling section into an advanced pilot tunnel region and a main blasting region; the advanced pilot tunnel region is blasted twice, and the main blasting region is then subjected to third blasting; the drilling footage of the third blasting is equal to that of the first blasting of the advanced pilot tunnel; and after one blasting cycle, a reserved pilot tunnel is formed in a new tunneling section, such that starting from a second cycle, blasting can be performed according to a normal cyclic drilling footage, and a situation that rock slag covers the bottom of the main blasting region after the first cyclic pilot tunnel blasting does not occur, thus providing a faster mode for blasting implementation of all sections.

Description

A three-time blasting method for hollow hole straight-hole cutting technical field

The invention relates to the technical field of engineering blasting, in particular to a three-time blasting method for hollow hole straight-hole cutting.

Background technique

In the process of excavation of traffic tunnels and mine roadways, 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 flying stones produced by the conventional cutting and blasting methods can be thrown to the area 20m~30m away from the working face, and some flying stones can even reach the area of 40m. facility.

At present, in order to improve the mechanization level of drilling and blasting construction of rock roadway excavation in coal mines, a drilling, loading and transporting machine is usually used in the excavation construction. Due to the structural characteristics of the all-in-one machine equipment during blasting, the all-in-one machine head can only be withdrawn to a position 15m~20m away from the excavation face. In order to avoid the damage to the head of the all-in-one machine caused by blasting flying stones, it is necessary to set up multiple protection facilities between the excavation face and the head. The process of building protection facilities increases the construction process and thus increases the construction cost.

Under the condition that the number of available detonator sections is limited, such as the case where there are only 5 electric detonators allowed in a coal mine, the split-section method is often used for construction, so that the lower section is detonated first, and then the upper section is detonated. This not only reduces the difficulty of flying stone control caused by the high cutting position of the positive step method, but also solves the roof safety problem caused by the inverted step method. However, there are also the following problems in the first blasting technology of the lower section: (1) If all blasting tasks of the lower section rocks cannot be completed at one time, for example, the blasting of the lower section is completed in 2~3 times, the collapsed rocks will be scattered in the first blasting. On both sides of the blasting section, the unexploded parts on both sides are buried. Subsequent procedures on both sides of the lower section, such as drilling, charging, wiring, detonation, etc., must be carried out after removing these rocks. This greatly reduces the construction efficiency. (2) If all the blasting tasks of the lower section of the rock can be completed at one time, since the blasting range covers the entire lower section, the blasting flying stones are thrown outward along the entire lower section, and it is difficult to effectively protect the equipment in front of the tunnel working face.

In addition, due to the large amount of blasting charge in one-time blasting of large-section tunnels, especially the poor air conditions, the excess explosive energy cannot be released, making it difficult to control the blasting vibration.

In the prior art:

The journal paper "Protection of Flying Rocks During Blasting Construction of Hydraulic Tunnels" (Song Yu, Heilongjiang Water Conservancy Science and Technology, 2019-08, pp. 150-152) discloses a protection technology for blasting flying rocks. For large equipment that is inconvenient to evacuate in the field, use rubber pads, cotton pads, or thick branches and other protective equipment to cover it, so as to reduce the kinetic energy of flying stones and reduce the damage to equipment caused by flying stones. This method of strengthening coverage and shielding belongs to passive protection, which cannot completely avoid the damage of flying stones to equipment. There are many protection procedures and labor intensity, which affects the progress of the excavation. In addition, the requirements for the bearing capacity and quality of protective equipment are high, and the cost increase.

Chinese Patent Publication No. CN102914226 discloses a blasting vibration damping method for hollow hole straight eye diamond cutting. Use a down-the-hole drilling machine to drill a hollow hole with a diameter of 90mm to 180mm in the middle of the tunnel face; use a rock drill to drill a number of blast holes, including undercut holes, auxiliary holes, peripheral holes and bottom plate holes spread around the hollow hole ; Detonate explosives according to the arrangement sequence of the blastholes and the delay time of the detonator. The purpose of the invention is to reduce the impact of blasting vibration on buildings and residents' lives.

Chinese Patent Publication No. CN109372509A discloses a method for arranging double-empty rhombus-shaped undercut holes in access filling mining. The purpose of the invention is to improve the utilization rate of blast holes, increase the length of the cycle footage, and reduce the cost of rock drilling and blasting. Reduce the number of cycle operations, shorten the mining time of the approach, and improve the productivity and safety of backfill mining.

Chinese Patent Publication No. CN107218043 A discloses a method for excavating a broken surrounding rock cavern. The hole is expanded and excavated, and the explosions are sequentially initiated from the center of the pilot hole to the surrounding holes, and the slag is discharged; finally, the main hole support is completed. The problems of this patent are: (1) During the drilling and blasting excavation process of the pilot hole, the throwing distance and throwing range of the blasting flying stones along the axis of the pilot hole cannot be effectively controlled, and the relative position of the driving face and the pilot hole cannot be effectively controlled. damage to equipment and facilities. (2) The caving rocks from the blasting of the pilot tunnel are scattered on both sides of the blasting section of the pilot tunnel, and the unblasted parts on both sides are filled. Subsequent procedures on both sides of the pilot hole, such as drilling, charging, wiring, detonation, etc., must be carried out after removing these rocks. This greatly reduces the construction efficiency.

Chinese Patent Publication No. CN 102758633 B discloses a construction method for a large-section tunnel with good surrounding rock conditions. The method includes: (1) determining a central pilot hole on a section of a predetermined tunnel; Determine the location distribution of the blast holes on the section. (3) Drill a blast hole on the section of the central pilot hole; (4) Fill the blast hole with explosive detonators and detonate in sequence; (5) Exhaust smoke and remove the stone slag; (6) Outside the central pilot hole and inside the tunnel (7) Exhaust smoke and remove stone ballast; (8) Support; (9) Repeat the above steps until the tunnel reaches the predetermined length. This method also fails to effectively control the throwing direction, throwing distance and throwing range of the blasting flying stones in the pilot hole.

  Chinese Patent Publication Nos. CN102914226 and CN109372509A use hollow hole straight-hole cutting blasting technology. The throwing direction of the blasting flying stone in the hollow hole straight-hole cutting is relatively determined, and the control of the blasting flying stone is relatively easy compared with the oblique-hole cutting. This technique has the following disadvantages:

(1) With the increase of the depth of the straight-hole cut hole, the utilization rate of the hole is greatly reduced. The article "Reasonable Parameters for Straight-Eye Cutting with Empty Holes" (Kutuzov, Shaanxi Coal Technology, 1989 03, pp. 57~60) pointed out: "When the diameter of the hole is constant, as the hole depth changes from From 1.5m to 3.2m, the utilization rate of the blasthole decreases almost linearly, the consumption of explosives also increases accordingly, and the consumption of blasthole length for blasting 1m3 rock also increases accordingly.” Especially for the use of allowable explosives in coal mines, the utilization rate of blastholes is significantly lower than that of ordinary rock explosives due to the low working power and sharpness of the explosives. The rock roadway blasting test carried out by the inventor in a coal mine shows that for the third-level coal mine permitted emulsion explosive, the blast hole utilization rate of hollow hole straight hole cutting is generally 60% to 75%.

(2) In order to solve the problem of low utilization rate of blast holes, the inventors tried to adopt the lower-section duplex blasting method to improve the utilization rate of blast holes in the full section and increase the blasting cycle footage of the full section. However, since the lower section duplex blasting method is carried out in the entire lower section, it is necessary to refill all remaining blasting holes with explosives and detonators after the first round of blasting of the lower section. In addition, the direction of the minimum resistance line is uncertain, which brings the following two problems. : ① It is difficult to control the blasting of flying stones, ② the amount of explosives is increased by about 30%, and the amount of detonators is increased by 100%.

(3) Because the cavity needs to be blasted out layer by layer from a hollow hole with a smaller diameter, the number of detonator segments that need to be detonated is larger than that of slant hole cutting. When the number of detonator segments is limited, one excavation cycle of a large-section tunnel requires multiple detonations to complete.

(4) For coal mine blasting, the number of available detonator segments is only 5, and the blasting efficiency is lower. Taking a rock roadway with a cross-sectional area of 28m ² in a coal mine as an example, since the rock at the lower part of the working face cannot be blasted off at one time, the rock dropped by the first blast will cover the lower part of the working face and the unexploded blastholes on both sides. The blasting operation of the second gun can only be carried out after the ballast and the ballast are removed, which seriously affects the construction efficiency. Therefore, the straight-hole cutting technology is rarely used in the excavation and blasting of large-section rock roadways in coal mines.

technical solutions

The purpose of the present invention is to provide a three-time blasting method for hollow hole straight-hole cutting to solve the following problems encountered by the straight-hole cutting blasting method in tunnel excavation: (1) The number of available detonator sections is limited, especially the use of coal mine permits Under the condition of using electric detonator, the problem of too many blasting times of the lower section. (2) Rocks from multiple blasting of the lower section or the first blasting of the pilot tunnel are scattered in the lower part of the working face and on both sides of the blasting section of the pilot tunnel, and the unblasted parts on both sides are buried, resulting in the problem of low construction efficiency. (3) The utilization rate of the hollow hole straight hole cut hole is low, which leads to the problems of low utilization rate of the blast hole and small cycle footage in full-section blasting. (4) The problems caused by the use of the lower-section duplex blasting method are that ① the blasting flying stones cannot be controlled, and ② the amount of explosives and detonators increases rapidly. (5) The problem that the flying stones thrown along the axis of the pilot hole by the blasting of the pilot hole destroy the equipment near the working face.

In order to achieve the above object, the technical scheme adopted by the present invention is:

A three-time blasting method for hollow hole straight-hole cutting, characterized in that it comprises the following steps:

S1. Excavate a pilot hole on the side of the centerline of the excavation section and towards the direction of the unprotected target of the working face. The pilot hole divides the excavation section into the advanced pilot hole area and the main explosion area;

In principle, the smaller the height and width of the advanced pilot hole, the better. In addition to allowing the operator and drill arm to enter, the shovel head of the ballast removal equipment should also be able to enter the hole for ballast removal;

The principle of selecting the depth of the super-leading pilot hole is to improve the utilization rate of the full-section blast hole under the premise of pursuing a large footage, and its depth will generally not exceed 5m;

It should be explained that although the pilot hole formed for the first time is in the advanced pilot hole area, it is not a real advanced pilot hole.

S2. Hollow holes, reaming holes, auxiliary holes and slot edge holes are drilled on the section of the advanced pilot hole, wherein the reaming slot holes are evenly arranged around the hollow hole, the slot edge holes are arranged on the outline of the pilot hole, and the reaming slot holes are arranged on the outline of the pilot hole. Auxiliary holes are evenly arranged between the hole and the side hole, and the depths of the expanded hole, the auxiliary hole and the side hole are required to be the same and less than the depth of the hollow hole, and the depth of the expanded hole, the auxiliary hole and the side hole is set as T;

S3. Loading explosives and detonators into the blastholes of the advanced pilot hole, first blasting, and cleaning up the slag covering the bottom of the main blasting area after the first blasting; , the total footage of the two blasting is L;

The footage control principle of the two blasting is: the first blasting maximizes the footage, and the second blasting only needs to blast the remaining residual holes;

What needs to be explained is: the ideal state is L=T, but it is difficult to achieve 100% blasthole utilization in practice, so L is less than T in reality.

S4. Drill peripheral holes and auxiliary holes in the main blasting area, and the auxiliary holes surround the advanced pilot hole area;

S5. Load explosives and detonators in the main blasting area, and complete the third blasting of the first cycle in order of distance from the advanced pilot hole area from near to far. The footage of the third blasting is equal to the footage of the first blasting of the advanced pilot hole. After the third blasting, an advanced pilot hole was actively formed on the excavation section. The depth of the advanced pilot hole was equal to the cyclic footage of the second blasting. So far, the first blasting cycle was completed. After the first cycle, a new leading hole was formed. The advanced pilot hole area and the new main explosion area;

S6. Drill holes in the new advanced pilot hole area and the new main blasting area respectively according to the methods described in S2 and S4; usually for the convenience of construction, after the first cycle of blasting is completed, charging in steps S2 and S4 The drilling of the holes can be done at the same time.

S7. Carry out two blasting of the new advanced pilot hole area according to the blasting method described in S3, and then blast the new main blasting area according to the method described in S5, and require that the blasting footage of the new main blasting area be L;

So far, the second blasting cycle is completed, and the blasting method of the second blasting cycle is repeated until the blasting of all sections is completed.

Preferably, when the surrounding rock conditions of the section are weak surrounding rock conditions, each time a person enters the advanced pilot tunnel area for work such as drilling, charging, etc., the advanced pilot tunnel area is passively supported, and the passive support is A support frame whose shape and size are adapted to the contour of the advanced pilot hole area is placed in the advanced pilot hole area.

Preferably, a ballast stack or a ballast shield is placed between the excavation working face and the equipment to be protected, and the ballast stack or the ballast shield is arranged opposite to the advanced pilot hole area; the height of the ballast stack or the ballast shield is greater than that of the expansion The maximum distance between the slot and the bottom plate, the width of the ballast stack or the ballast plate is greater than the maximum opening width of the leading pilot hole area. Preferably, the distance between the ballast stack or the ballast plate and the excavation face is 2.0m to 8.0m.

Preferably, the width of the super-leading hole region is 1.0m-2.0m, and the height is 1.5m-2.0m.

Preferably, the three times of blasting all use 1-5 sections of coal mine allowable electric detonators.

beneficial effect

The positive effects of the present invention are:

(1) The present invention adopts the pilot hole first method of the lower section and the hollow hole straight hole cutting technology. By controlling the section size of the pilot hole, the number of detonator sections is used less, and the first blasting method of the pilot hole section is completed by one-time detonation method. The advanced excavation of the pilot tunnel solves the problem of low construction efficiency when the lower section is blasted multiple times.

(2) The present invention makes full use of the residual blastholes in the pilot hole to carry out the second blasting, so as to achieve the designed blasthole utilization rate and the predetermined driving cycle footage of the pilot hole. The double blasting method of the pilot hole with small section is used to replace the double blasting method of the lower section, which solves the problem of the large amount of detonators and explosives caused by the high number of blasting of the lower section, and creates a good free surface for the blasting of other sections outside the pilot tunnel, which improves the overall The blasthole utilization rate and cycle footage of the section.

(3) The present invention controls the throwing direction of the flying stones by means of the side wall of the guide hole, and avoids the equipment that needs to be protected on the working face by selecting the position of the guide hole.

(4) By setting the ballast stack or the ballast plate, the size of the ballast stack or the ballast plate matches the size of the guide hole and the position of the hollow hole, so as to control the throwing distance and throwing range of the flying stones.

(5) The cycle footage achieved by the double blasting method of the pilot hole creates a good free surface condition for the third blasting of the full section, ensures the utilization rate of the blasthole and the cycle footage for the full section blasting, and reduces the detonator. and consumption of explosives.

(6) For a long time, when blasting the main blasting area with a pilot hole, those skilled in the art often take the cyclic footage of the main blasting area equal to the cyclic footage of the blasting area of the pilot hole. This is because everyone has formed an inherent thinking, It is believed that the construction efficiency is high when the cycle footage is large. Do you not know that this will bring the following two defects. One is that the rock collapsed by the blasting of the pilot tunnel is scattered on both sides of the blasting section of the pilot tunnel, and the unexploded parts on both sides of the reclamation need to be cleaned repeatedly. Blasting the collapsed rock in the pilot hole reduces the construction efficiency. Second, the pilot hole needs to be excavated again during the second cycle of blasting. If the pilot hole is not to be excavated, the depth of the pilot hole must be increased, which is bound to increase the depth of the pilot hole. It needs to be supported with bolts, etc., which reduces the construction efficiency again. In order to improve the construction efficiency, the inventor adopts reverse thinking and only excavates a small-sized pilot hole during the first cycle. Even if a weak rock section is encountered, it is only necessary to push the support frame to passively support the pilot hole, and then put the The pilot hole is blasted twice, creating a good free surface for the blasting of the main blasting area outside the pilot hole, and improving the utilization rate of the full-section blasthole. After field tests, the blasting utilization rate of the main blasting area can basically reach 100%; Then reduce the first cycle footage of the main blasting area, and actively reserve a pilot hole for the second cycle footage, so that starting from the second cycle, the blasting can be performed according to the normal cycle footage, and there will be no slag coverage after the first cycle pilot hole blasting. The situation at the bottom of the main blasting zone provides a faster way for blasting all sections, with outstanding substantive features and significant progress.

Description of drawings

Figure 1 is a schematic diagram of the full-section blasthole arrangement;

Fig. 2 is the layout schematic diagram of the advanced pilot hole area;

Figure 3 is a schematic diagram of the excavation process;

Fig. 4a is a schematic diagram of the arrangement of the ballast stack, and Fig. 4b is a cross-sectional view taken along the line A-A of Fig. 4a;

Figure 5 is a schematic diagram of the full-section blasthole arrangement in the embodiment.

FIG. 6 is a schematic diagram for passively supporting an advanced pilot hole.

In the picture: 1-Advanced pilot hole area, 2-Main blast area, 3-Hollow hole, 4-Expanded slot hole, 5-Advanced pilot hole area auxiliary hole, 6-Slot side hole, 7-Peripheral hole, 8-Main hole Auxiliary hole in blast area, 9-support frame.

①~⑤ correspond to 1~5 detonators respectively.

Embodiments of the present invention

With reference to FIGS. 1 to 6 , a specific embodiment of a three-time blasting method for hollow hole straight-hole undercutting provided by the present invention will be described.

Taking the auxiliary transportation roadway of a coal mine as an example, a three-time blasting method of hollow hole straight-hole cutting is described. The roadway is a straight wall semi-circular arch section, the excavation width is 5.40m, the height is 3.75m, and the section area is 15.53m ² . Its working force is 220ml, the explosion speed is 3000m/s, the intensity is 0.01m, the diameter of the medicine roll is 0.035m, the length is 0.40m, and the mass is 400g/roll. 1~5 sections of coal mine allowable electric detonators are used. The diameter of the empty hole is 0.133m, and the diameter of the charging hole is 0.042m. 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 used for pedestrians and equipment passages.

The specific construction steps include:

S1. Excavate a pilot hole on the side of the excavation section facing the unprotected target of the working face, and divide the excavation section into the advanced pilot hole area 1 and the main explosion area 2. The pilot hole width a=1.70m, height h=1.70m. When the excavation section is weak surrounding rock, the support frame 9 shown in FIG. 6 is pushed into the advanced pilot tunnel area 1 for passive support, so as to protect the safety of the operators.

S2. On the advanced pilot hole area 1, according to accompanying drawing 5, the hollow hole 3 with a diameter of d ₁ is drilled, the diameter of the expanded slot hole 4 of d ₂ , the auxiliary hole 5 in the advanced pilot hole area and the slot edge hole 6, the expanded slot hole 4 The maximum distance from the floor is H ₂ . The hole depth of the charging hole is T=2.50m, and the drilling depth of the hollow hole 3 is 20.0m at one time. When the depth of the hollow hole 3 is less than the hole depth of the charging hole, it is re-drilled. Hollow hole 3 is located 0.85m to the right of the centerline of the roadway and 0.9m above the bottom plate; reaming holes 4 are arranged around hollow hole 3, and the circumferential equidistant spacing between adjacent reaming holes 4 is maintained. The center-to-center distance of hole 3 t ₁ =(1.5~3.0)d ₁ +0.5d ₂ =0.22~0.42m, take t ₁ =0.24m; arrange a circle of slot edge holes 6 on the contour line of the leading hole area 1, The hole spacing is 0.45m, 0.55m; the auxiliary hole 5 in the advanced pilot hole area is arranged between the expansion slot hole 4 and the slot edge hole 6, and the hole spacing is 0.55m.

S3. Arrange the ballast stack at 4.0m directly in front of the leading pilot hole area 1 (see Figures 4a and 4b). The width of the ballast stack is W=1.9m and the height H ₁ =1.2m. Loading explosives and 1~5 detonators into the first blast hole in the super-leading pilot hole area to complete the first blasting; the first blasting blast hole utilization rate of the first cycle is η ₁ = 0.7, and the footage is L ₁ =η ₁ T =0.7×2.50m=1.75m;

S4. Carry out the second blasting on the excavation working face in the advanced pilot tunnel area 1. The blasting utilization rate of the second blasting in the first cycle is η ₂ = 0.98, and the footage is L ₂ =η ₂ (TL ₁ )=0.98× (2.5-1.75) m=0.735m; after the blasting is completed, remove the rock slag that has fallen and covered the bottom of the main blasting area 2;

S5. The peripheral holes 7 and the auxiliary holes 8 in the main blasting area are drilled in the main blasting area, and the auxiliary holes 8 in the main blasting area are arranged around the advanced pilot hole area 1. The spacing between holes and rows of auxiliary holes 8 in the main explosion area is 0.45m and 0.55m, and the spacing between holes of peripheral holes 7 is 0.40m. The depth of the peripheral hole 7 and the auxiliary hole 8 in the main blast zone is T ₁ =1.85m;

S6. Load explosives and detonators 1 to 5 in the main blasting area 2, and detonate in the order from near to far away from the lead hole area, and complete the third blasting of the first cycle. The footage of the third blasting is also the first The blasting footage of one cycle is equal to the first blasting footage L ₁ = 1.75m of the leading pilot hole area 1, and the blast hole utilization rate is = 0.95.

In this way, after the third blasting, a truly advanced pilot hole is actively formed on the excavation section, and the depth of the advanced pilot hole is equal to the cyclic footage L ₂ of the second blasting; After one cycle, a new leading hole area and a new main explosion area are formed;

S7. Carry out two blasting operations in the new advanced pilot hole area according to steps S2-S4;

S8. Carry out blasting in the new main blasting area according to the S5-S6 scheme, and the blasting footage is required to be L=L ₁ +L ₂ =2.485m; at this point, the second cycle footage is completed, and the blasting method of the second cycle footage is repeated until Complete the blasting of all sections. Usually, for the convenience of construction, after the first cycle of blasting is completed, the drilling of the charging holes in the advanced pilot hole area and the main blasting area can be completed at the same time.

Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the art within the essential scope of the present invention should also belong to the present invention. the scope of protection of the invention.

Definitions of terms used in this specification:

(1) Slot side holes: The blastholes arranged on the excavation outline of the advanced pilot hole area have the same function as the peripheral holes, and are mainly used to form the excavation outline of the advanced pilot hole area.

(2) The positive step method is a construction method in which the tunnel excavation section is divided into two or more excavation working faces according to the height, and the upper excavation working face is ahead of the lower excavation working face by a certain distance.

(3) The inverted step method is a construction method in which the tunnel excavation section is divided into two or more excavation working faces according to the height, and the lower excavation working face is ahead of the upper excavation working face by a certain distance.

(4) 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.

(5) In the construction process of the split-section method in which the lower section is blasted first, in view of the low utilization rate of blastholes in the lower section, after the first round of blasting at the lower section is completed, the original blastholes will continue to be used, and the lower section will be blasted first. Repeated charging, connection, and detonation operations in the residual blastholes, completed the second round of blasting, and blasted the residual surrounding rock; thus, the lower section reached a deeper excavation depth and created a better air surface for blasting at the upper section. . This method can effectively improve the utilization rate of the full-section blasting hole and improve the full-section blasting cycle footage.

(6) The duplex blasting method of the pilot hole, in the construction process of the split-section method in which the pilot hole is advanced and blasted, in view of the low utilization rate of the first blasting blasting hole when the pilot hole is cut with a straight hole, the first blasting in the pilot hole is used. After the completion, continue to use the original blast hole, repeat the charging, connection, and detonation operations in the residual blast hole of the pilot hole section, complete the second blasting, and blast the remaining surrounding rock; The excavation depth can create a better air surface for full-section blasting. This method can effectively improve the utilization rate of the full-section blasting hole and improve the full-section blasting cycle footage. Compared with the lower section duplex blasting method, it can effectively reduce the consumption of detonators and explosives in the second blasting, and improve the safety of blasting operations.

Claims (7)

1. A three-time blasting method for hollow hole straight-hole cutting, characterized in that it comprises the following steps:

   S1. Excavate a pilot hole on the side of the centerline of the excavation section and towards the direction of the unprotected target of the working face. The pilot hole divides the excavation section into the advanced pilot hole area and the main explosion area;

   In principle, the smaller the height and width of the advanced pilot hole area, the better. In addition to allowing the operator and drill arm to enter, the shovel head of the ballast removal equipment should also be able to enter the hole for ballast removal;

   The principle of selecting the depth of the pilot hole is to improve the utilization rate of the full-section blasthole on the premise of pursuing a large footage;

   S2. Hollow holes, reaming holes, auxiliary holes and slot edge holes are drilled on the section of the pilot hole, wherein the reaming slot holes are evenly arranged around the hollow hole, the slot edge holes are arranged on the outline of the pilot hole, the reaming slot holes and The auxiliary holes are evenly arranged between the slot side holes. It is required that the depths of the expanded slot holes, the auxiliary holes and the slot side holes are the same and less than the depth of the hollow hole.

   S3. Loading explosives and detonators into the blasthole of the pilot hole, first blasting, cleaning up the slag covering the bottom of the main blasting area after the first blasting; then blasting the second charge in the pilot hole, The total footage of the two blasting is L;

   The footage control principle of the two blasting is: the first blasting maximizes the footage, and the second blasting only needs to blast the remaining residual holes;

   S4. Drill peripheral holes and auxiliary holes in the main blasting area, and the auxiliary holes are arranged around the pilot hole area;

   S5. Load explosives and detonators in the main blasting area, and detonate in the order from near to far away from the leading pilot hole area to complete the third blasting of the first cycle. The footage of the third blasting is equal to the footage of the first blasting of the pilot hole. , After the third blasting, an advanced pilot hole is actively formed on the excavation section. The depth of the advanced pilot hole is equal to the footage of the second blasting. So far, the first blasting cycle is completed. After the first cycle, a new The advanced pilot hole area and the new main explosion area;

   S6. Drill holes in the new advanced pilot hole area and the new main blast area respectively according to the methods described in S2 and S4;

   S7. Carry out two blasting of the new advanced pilot hole area according to the blasting method described in S3, and then blast the new main blasting area according to the method described in S5, and require that the blasting footage of the new main blasting area be L;

   So far, the second blasting cycle is completed, and the blasting method of the second blasting cycle is repeated until the blasting of all sections is completed.
2. The three-time blasting method for hollow hole straight hole undercutting according to claim 1, characterized in that, when the surrounding rock condition of the section is weak surrounding rock, each time when personnel enter the advanced pilot hole area to drill the blast hole and fill the explosive, Passive support is performed in the advanced pilot tunnel area; the passive support is to place a support frame in the advanced pilot tunnel area with a shape and size adapted to the contour of the advanced pilot tunnel area.
3. The three-time blasting method for hollow hole straight-hole undercutting according to claim 1 or 2, characterized in that a ballast stack or a ballast plate is arranged between the front of the leading pilot hole area and the protected equipment; the ballast stack or The height of the ballast baffle plate is greater than the maximum distance between the expansion slot and the bottom plate, and the width of the ballast baffle stack or the ballast baffle plate is greater than the maximum opening width of the leading pilot hole area.
4. The three-time blasting method for hollow hole straight-hole undercutting according to claim 3, characterized in that, the distance between the ballast retaining pile or the ballast retaining plate and the excavation working face is 2.0m-8.0m.
5. The three-time blasting method for straight hole undercutting in a hollow hole according to claim 1 or 2, characterized in that, the width of the advanced pilot hole area is 1.0m~2.0m, and the height is 1.5m~2.0m.
6. The three-time blasting method for hollow hole straight-hole undercutting according to claim 1, characterized in that, the three times of blasting all use 1-5 sections of coal mine permitted electric detonators.
7. The three-time blasting method for hollow hole straight-hole undercutting according to claim 1, wherein the depth of the pilot hole is not more than 5m.