Segmented straight-hole cut blasting method

Abstract

The present invention relates to the technical field of blasting excavation, and specifically to a segmented straight-hole cut blasting method, comprising drilling, charging and detonation at an excavation face. During drilling at the excavation face, the arrangement of cut holes comprises the following steps: S1, at the central position of a cut zone in a roadway cross-section, using a down-the-hole drill to drill a large-diameter center hole having a diameter of 100-120 mm and a depth of 4 m or more; S2, arranging four to six fracture-expansion holes around the large-diameter center hole, wherein the depth of each fracture-expansion hole is at least 4 m, the center distance between the fracture-expansion hole and the center hole is 0.5-1.0 m, and the axial direction of the fracture-expansion hole is consistent with that of the center hole; S3, arranging a row of fracturing holes between the fracture-expansion holes, wherein the depth of the fracturing holes is 0.5 times that of the fracture-expansion holes; and S4, arranging an additional row of auxiliary throwing holes with a spacing of 0.5 m below the lowest fracture-expansion hole, wherein the drilling direction of the auxiliary throwing holes is inclined towards the roof of a roadway and forms an included angle of less than 90 degrees with the roadway cross-section. The present invention can solve the problems of limited blasting depth and low efficiency during cut blasting, and has good market application prospects.

Description

A method of blasting straight-hole segmented trenching Technical Field

[0001] The invention belongs to the technical field of blasting excavation, and in particular relates to a blasting straight-hole segmented trenching method. Background Art

[0002] Among existing excavation methods, slotting is a common method, primarily used to dig narrow trenches. However, when digging large trenches, traditional slotting methods typically require a large number of workers and equipment, resulting in low excavation efficiency and a significant waste of time and resources. Therefore, a new excavation method is needed to address this problem.

[0003] Drilling and blasting is a common method used in underground roadways and rock tunnel excavation. During drilling and blasting, blastholes are generally divided into slot holes, auxiliary holes, peripheral holes, and bottom holes. The arrangement is as follows: the slot hole is located in the middle and lower portion of the roadway cross section, the auxiliary holes (or caving holes) surrounding the slot hole are located, the top and sides of the cross section are located as peripheral holes, and the bottom edge of the cross section is located as the bottom hole. Since the slot hole is blasted first to create a second free surface for the auxiliary holes, the blasting efficiency of the slot hole is crucial for rapid blasting of the roadway.

[0004] In previous slot hole designs, slot holes came in various forms, such as wedge-shaped slot holes, tapered slot holes, and straight-hole slot holes. With the development of medium- and long-hole blasting technology and the use of drilling rigs, straight-hole slot holes have become the most common. Limited by drilling equipment, the diameter of the slot hole is the same as that of other blast holes, generally 32-40mm. Because slot hole blasting has only one free surface, the blasting depth is limited by the clamping force of the surrounding rock, typically less than 3m per blast. Furthermore, many densely packed slot holes must be arranged, impacting the excavation speed. Currently, with the advancement of drilling equipment, especially down-the-hole drills, drilling blast holes with a diameter of over 100mm is no longer a problem. Therefore, the use of large-diameter straight-hole slot holes can solve the problem of low slot hole blasting efficiency.

[0005] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the Invention

[0006] The purpose of the present invention is to provide a blasting straight-hole segmented slotting method to solve the problem of limited blasting depth and low efficiency during slotting blasting.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A blasting straight-hole segmented slotting method includes drilling holes, charging explosives, and detonating at an excavation working face. When drilling holes at the excavation working face, the arrangement of the slotting holes includes the following steps:

[0009] S1. Use a down-the-hole drill to drill a large-diameter center hole with a diameter of 100-120 mm and a depth of more than 4 m in the center of the tunnel section.

[0010] S2. Arrange 4-6 expansion holes around the central hole; the expansion holes are at least 4 meters deep, 0.5-1.0 meters away from the center of the central hole, and aligned with the axis of the central hole;

[0011] S3, arranging a row of crushing holes between the crushing expansion holes; the depth of the crushing holes is 0.5 times that of the crushing expansion holes;

[0012] S4. Arrange a row of auxiliary throwing holes with a spacing of 0.5m below the lowest expansion hole. The drilling direction of the auxiliary throwing holes is inclined upward in the tunnel, forming an angle less than 90 degrees with the tunnel section.

[0013] Preferably, 3.5-4.0 kg of common explosives are placed at the bottom of the central hole during charging, and the expansion hole, the crushing hole and the auxiliary throwing hole adopt a conventional continuous charging structure.

[0014] Preferably, millisecond delay detonators are used for segmented delayed detonation during detonation, and the sequence of segmented detonation is as follows: first, the expansion hole and the crushing hole are detonated together; then, the explosives at the bottom of the center hole and the auxiliary throwing hole are detonated together; finally, the conventional auxiliary hole, conventional peripheral hole and conventional bottom hole are detonated in sequence.

[0015] Preferably, the diameters of the expansion holes, the crushing holes and the auxiliary throwing holes are all 32-40 mm.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The blasting straight-hole segmented slotting method of the present invention makes full use of the principle of the line of least resistance. The center hole increases the crushing free surface and the crushing expansion space of the slotting, thereby forming a deeper slot cavity, so that the depth of the conventional auxiliary hole and the conventional peripheral hole can be further deepened to 4 meters, which is beneficial to improving the blasting efficiency and the depth of one blasting.

[0018] (2) In the blasting straight-hole segmented slotting method of the present invention, explosives are arranged at the bottom of the center hole and detonated after the crushing hole, which can improve the slag throwing slotting effect; the auxiliary throwing hole throws the broken rock out of the slot cavity, which is more conducive to the blasting of conventional auxiliary holes and facilitates slag removal and rock loading, thereby increasing the construction speed.

[0019] (3) The blasting straight-eye segmented trenching method of the present invention can drill more than 10 meters into the center hole at one time under the technical condition that the down-the-hole drill has a certain drilling depth, which can be used for several cycles of blasting trenching, thereby accelerating the cycle footage and helping to improve the excavation speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG1 is a schematic diagram of a blasthole arrangement of the present invention;

[0021] FIG2 is a schematic cross-sectional view of a charge structure of the present invention;

[0022] FIG3 is a schematic diagram of the detonation network of the present invention;

[0023] Description of main reference numerals:

[0024] 1. Center hole; 2. Crushing hole; 3. Crushing expansion hole; 4. Auxiliary throwing hole; 5. Conventional bottom hole; 6. Conventional auxiliary hole; 7-10. Conventional peripheral holes. DETAILED DESCRIPTION

[0025] The following is a clear and complete description of the technical solution of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts are within the scope of protection of the present invention.

[0026] In the description of the present invention, it should be noted that the orientations or positional relationships indicated by terms such as "center", "up", "down", "left", "right", "vertical", "horizontal", "inside" and "outside" are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, 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 a limitation on the invention.

[0027] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and connections within two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention.

[0028] Referring to Figures 1-3, a blasting straight-hole segmented slotting method includes drilling holes, charging explosives, and detonating explosives at the excavation face. When drilling holes at the excavation face, the slotting holes are arranged as follows:

[0029] At the center of the tunnel section cut area, a large diameter center hole 1 with a diameter of 100-120 mm and a depth of more than 4 m is drilled using a down-the-hole drill;

[0030] Arrange four ordinary diameter expansion holes 3 around the large diameter center hole 1. The depth of the expansion holes 3 is consistent with that of the center hole 1. The center distance between the expansion holes 3 and the center hole 1 is 0.5-1.0 meters, and the axis direction of the expansion holes 3 is consistent with that of the center hole 1.

[0031] A row of crushing holes 2 is arranged between the crushing holes 3. The depth of the crushing holes 2 is 0.5 times that of the crushing holes 3, which is used to crush large rocks.

[0032] A row of auxiliary throwing holes 4 with a spacing of 0.5 meters is arranged below the lowest expansion hole 3. The drilling direction of the auxiliary throwing holes 4 should be inclined upward to the tunnel, forming an angle of <85° with the tunnel cross section, as shown in Figure 2 where a <80°, so as to enhance the throwing effect on the rock and increase the slag throwing distance.

[0033] The charge structure is as follows: 3.5-4.0 kg of ordinary explosives are placed at the bottom of the center hole 1, and the crushing hole 3, crushing hole 2 and auxiliary throwing hole 4 adopt a conventional continuous charge structure. When detonating, millisecond delay detonators are used for segmented delay detonation. The segmented detonation sequence is as follows:

[0034] First, the expansion hole 3 and the crushing hole 2 are detonated together. The rocks in the expansion hole 3 are crushed and expanded by the second free surface in the center hole 1, and fill the free space in the center hole 1. The large rocks in the shallow part are further crushed by the blasting action of the crushing hole 2.

[0035] The explosives at the bottom of the center hole 1 and the auxiliary throwing holes 4 are detonated together, and the cracked rock blocks in the circle of the expansion holes 3 are thrown out of the rock mass by the blasting force at the bottom of the center hole 1, thereby forming a groove cavity. The groove is completed and provides a second free surface for the conventional auxiliary hole 6 blasting;

[0036] When the trenching is completed, the conventional auxiliary hole 6, the conventional peripheral hole 7 and the conventional bottom hole 5 are detonated in sequence, and the blasting of the excavation working face is completed.

[0037] The diameters of the expansion holes 3, crushing holes 2 and auxiliary throwing holes 4 are all 32-40 mm. The design standard is the underground excavation section (2.4 m × 2.5 m).

[0038] Blasthole diameter affects drilling productivity, hole count, unit explosive consumption, and tunnel wall smoothness. Increasing the blasthole diameter and the corresponding explosive diameter concentrates the explosive energy, thereby increasing detonation velocity and stability. However, excessively large blasthole diameters reduce drilling speed and affect rock fragmentation quality, tunnel wall smoothness, and surrounding rock stability.

[0039] The blasthole depth refers to the vertical distance from the bottom of the blasthole to the working face. In order to achieve rapid excavation, on the premise of improving the degree of mechanization of excavation and improving work organization, efforts should be made to increase the hole depth and the number of cycles. According to its own production conditions and combined with many years of production practice, the blasthole depth reaches 2.8m. The current experimental design blasthole depth is 3.5m to 4m.

[0040] The number of blastholes is mainly related to factors such as the tunnel cross-section, rock properties, and explosive performance. Too few blastholes will result in excessive large rock debris, which is not conducive to efficient rock loading; on the contrary, too many blastholes will increase the workload of rock drilling. The number of blastholes is calculated according to the formula:

[0041]

[0042] f is the Proctor coefficient, which is taken as 12; S is the cross-sectional area of ​​the tunnel, which is taken as 5.76 m2; it can be seen that N>24.1, so the minimum number of blast holes is 25.

[0043] In the straight-hole excavation method, the empty hole serves as the auxiliary free surface of the first explosive charge hole and the expansion space of the broken rock. Therefore, it is particularly important to reasonably determine the size and position of the empty hole.

[0044] The compensation space formula can be calculated as follows:

[0045]

[0046] V 增 The volume of rock increased after being crushed within the rock crushing circle; R is the radius of the crushing circle, which is calculated as 5 cm in the test;

[0047] h is the blasthole depth, the test blasthole depth is 2.8m; n is the number of empty holes; is the borehole radius, which is 2 cm; λ is the rock expansion coefficient, which is 1.5;

[0048] In order to provide compensation space, there should be v 补 >v 增 , then n≥6.25. Therefore, we know that there are at least 7 40mm holes. Because the mine originally used an 8-hole square cut, for the convenience of the experiment, the size and number of holes remained unchanged. Therefore, a total of 8 holes were arranged in the design, with a hole spacing of 0.05m, and a charging hole was arranged in the center of the hole. Hole spacing: The diameter of the excavation drill hole is 40mm. According to the formula:

[0049] W=(15~30)d

[0050] W is the line of least resistance

[0051] d is the drilling diameter

[0052] The hole spacing between the auxiliary holes and the peripheral holes is about 0.8m-1.2m, and the hole depth can be 2.5m-4.0m according to the experimental requirements. The arrangement of each blasthole is shown in Figure 1.

[0053] The holes were drilled using No. 2 rock emulsion explosive (32mm diameter cartridges). Continuous charging was used for the peripheral holes, while interval charging was used for the slot holes. The interval medium was taphole mud or water bags. The slot holes were approximately 2.6m long at the front end, with a charge length of 1.8m and a fill length of 0.8m. The total length of the slot bottom was approximately 0.9m, with a charge length of 0.6m and intervals of 0.3m between taphole muds. A cross-section of the charge structure is shown in Figure 2.

[0054] The detonators used in the design are half-second delay detonating cord detonators. Because the number of explosive packages is small, a cluster parallel detonation network is selected. The detonation order is generally slot hole - auxiliary hole - peripheral hole, and each type of blast hole is further divided and detonated in sequence. The slot holes are detonated in sections, and the detonation order is to detonate the front explosive package first, and then the bottom explosive package. Therefore, the slot holes are separated by the front explosive package with low-segment detonators (1st and 3rd segments), and the bottom explosive package with higher-segment detonators (2nd and 4th segments). Then the auxiliary holes and peripheral holes are detonated in sequence. The peripheral holes are blasted simultaneously with the same segment detonators to improve the boundary flatness. When connecting the detonators, all the detonating cords are integrated into a bundle and bundled together with a detonating detonator to form the entire detonation network. The detonation network is shown in Figure 3.

[0055] The original method used for underground tunneling blasting was the oblique-eye tunneling method, with each tunneling advance of only 2.5m. The tunneling section size was basically 5m. 2 This is a small-section blasting operation with a rock hardness coefficient of 10 to 12. The rock is relatively hard, making blasting more difficult. The oblique-eye slotting method is not suitable for small-section hard rock excavation blasting, and the success rate decreases as the slot depth increases. To increase the single-pass advance, a new slotting method—the straight-eye segmented slotting method—is used.

[0056] Compared to the oblique-eye slotting method, which is limited by large cross-sections and cannot be too deep, the straight-eye slotting method can be used for both large and small cross-sections, with better results for small sections. It is excellent for medium-hard and hard rocks and is less restricted by hole depth, making its use more suitable for Guyi Mine. Based on the improved slotting method, in order to increase the utilization rate of blastholes, the slot holes are blasted in sections, with gun mud or water bags used to space the charges in the middle. This not only reduces explosive consumption but also avoids excessive density of explosives between adjacent blastholes, which can lead to poor bottom-hole blasting results.

[0057] The essence of in-hole segmented grooving is to divide the charge into segments along the depth of the hole, separating each segment with media such as water bags and taphole mud. The segments are then detonated sequentially from the outside inward at slightly different time intervals. This charge structure and detonation method changes the energy distribution within the blasthole, allowing the rock formation outside the middle of the blasthole to withstand the explosive energy of the charge. Simultaneously, the bottom segmented charge can fully utilize the residual stress from the explosion of the outer segmented charge, enhancing the crushing effect. Spatially, the blasting of the outer segmented charge creates new free surfaces and more auxiliary free surfaces, both large and small, for the bottom segmented charge.

[0058] More importantly, this changes the equivalent resistance of the charge to rock breaking and redistributes the rock's blast resistance along the depth of the hole, enabling deep blasting in deep holes, improving blasthole utilization, improving fragmentation, and reducing throw distance, ultimately creating an ideal, simple slot. Simultaneously, the original slot blasthole layout is shifted from the center to slightly below the cross-section, reducing flystone and achieving more complete rock fragmentation at the bottom.

[0059] The blasting straight-hole segmented slotting method of the present invention makes full use of the principle of the least resistance line. The center hole 1 increases the crushing free surface and the crushing expansion space of the slotting, thereby forming a deeper slot cavity, so that the depth of the conventional auxiliary hole 6 and the conventional peripheral holes 7-10 can be further deepened to 4 meters, thereby improving the blasting efficiency and the depth of one blasting; explosives are arranged at the bottom of the center hole 1 and detonated after the crushing expansion hole 3, thereby improving the slag throwing and slotting effect; the auxiliary throwing hole 4 throws the broken rock out of the slot cavity, which is more conducive to the blasting of the conventional auxiliary hole 6 and facilitates the slag removal and rock loading, thereby improving the construction speed; under the technical condition that the down-the-hole drill has a certain drilling depth, the center hole 1 can be drilled more than ten meters at a time for several cycles of blasting slotting, thereby accelerating the cycle footage and improving the excavation speed.

[0060] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many variations and modifications are possible in light of the foregoing teachings. The exemplary embodiments have been selected and described for the purpose of explaining the specific principles of the invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the invention and various options and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A blasting straight-hole sectional cut method, including drilling holes, charging, and initiating detonation at the tunneling working face, is characterized in that, When drilling holes in the driving face, the arrangement of the cut holes includes the following steps: S1. At the central position of the cut area of the roadway section, use a down-the-hole drill to drill a large-diameter central hole with a diameter of 100 - 120 mm and a depth of more than 4 m; S2. Arrange 4 - 6 expansion holes around the central hole; the depth of the expansion holes is at least 4 m, the center distance from the central hole is 0.5 - 1.0 m, and the axis direction is the same as that of the central hole; S3. Arrange a row of fragmentation holes between the expansion holes; the depth of the fragmentation holes is 0.5 times that of the expansion holes; S4. Arrange a row of auxiliary throwing holes with a row spacing of 0.5 m below the lowermost expansion hole. The drilling direction of the auxiliary throwing holes inclines upward to the roadway, forming an angle less than 90 degrees with the roadway section.

2. The cut method by blasting parallel cut holes according to claim 1, characterized in that, When charging, place 3.5 - 4.0 kg of ordinary explosive at the bottom of the central hole, and the expansion holes, the fragmentation holes and the auxiliary throwing holes adopt a conventional continuous charging structure.

3. The cut method of blast hole sectional cut according to claim 1, characterized in that, When detonating, use millisecond delay detonators for staged delay detonation. The staged detonation sequence is as follows: First, the expansion holes and the fragmentation holes detonate together; then, the explosive at the bottom of the central hole and the auxiliary throwing holes detonate together; finally, the conventional auxiliary holes, the conventional perimeter holes and the conventional bottom holes detonate in sequence.

4. The blasting straight-hole sectional cut method according to claim 3, characterized in that, The diameters of the expansion holes, the fragmentation holes and the auxiliary throwing holes are all 32 - 40 mm.

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