Hydraulic smooth blasting method for composite straight-hole cutout in small-section tunnels

Abstract

The present invention relates to a method for composite straight-eye slot hydraulic smooth blasting of hollow holes in small-section tunnels. Applying a three-arm rock drill to the excavation blasting of small-section tunnels will be subject to space limitations, making it impossible to achieve oblique slotting, and requiring a long ventilation time after blasting. This method estimates the number of blastholes, and drills hollow holes, slot holes, auxiliary slot holes, collapse holes, peripheral holes, peripheral auxiliary holes, and bottom plate holes on the tunnel blasting section; estimates the charge amount, and charges the blastholes in the form of continuous charging or interval charging, with detonating caps installed at the bottom of the explosives for reverse detonation; constructs a micro-difference detonation network in the hole, and the detonation sequence starts from the center of the tunnel blasting section, and then blasts outward layer by layer on both sides. This method greatly improves the blasting footage and effectively improves the utilization rate of blastholes. The three-arm rock drill is used in conjunction with the composite straight-eye slot hydraulic smooth blasting operation, which has high construction efficiency, low work intensity, accelerated construction progress, and effectively improved the economic efficiency of the project.

Description

Technical Field

[0001] The invention relates to the technical field of small-section tunnel excavation blasting, and in particular to a method for hydraulic smooth blasting of hollow holes of small-section tunnels using a composite straight-hole cut. Background Art

[0002] While smooth blasting technology for large-section tunnels, such as those used for highway and railway tunnels, is relatively mature, the blasting parameters for small-section tunnels differ significantly from those for large-section tunnels and cannot be directly applied. Excavation and blasting of small-section tunnels have always been subject to technical difficulties such as short blasting footage and high explosive consumption. The precise setting of blasting parameters, such as cut angle and blasthole arrangement, plays a crucial role in blasting operations in small-section tunnels.

[0003] As an advanced drilling device, the three-arm rock drill has been increasingly used in engineering practice. Significantly smaller than other similar equipment, it offers technical advantages such as miniaturization, strong practicality, and wide versatility, and is suitable for operating heights of 6-12 meters. However, applying the three-arm rock drill to the excavation and blasting of small-section tunnels, such as a parallel pilot tunnel with a cross-sectional dimension of 6.5×6.5m in a certain plateau railway tunnel, is limited by the operating space. The required blasting angle for the oblique (wedge-shaped) cut cannot be achieved, and the post-blasting ventilation period is long. Therefore, it is necessary to combine the characteristics of the three-arm rock drill and propose new blasting methods suitable for small-section tunnel excavation and blasting, expand the engineering application scope of the three-arm rock drill, and leverage the technical advantages of the three-arm rock drill in the engineering practice of small-section tunnel excavation and blasting. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for hydraulic smooth blasting of composite straight-eye hollow holes in small-section tunnels, which is combined with a three-arm rock drill to optimize blasting parameters and overcome the technical problem that the three-arm rock drill cannot achieve oblique-eye groove cutting.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for composite straight-hole cutout hydraulic smooth blasting of hollow holes in small-section tunnels, comprising:

[0007] Arrange the blast holes:

[0008] Estimate the number of blastholes and drill hollow holes, slot holes, auxiliary slot holes, cave-in holes, peripheral holes, peripheral auxiliary holes and bottom plate holes on the tunnel blasting section:

[0009] Blast hole charge:

[0010] Estimate the charge quantity, use continuous charge or interval charge to load the blasthole, and install the blasting caps at the bottom of the explosives for reverse detonation;

[0011] Building the detonation network:

[0012] A micro-difference blasting network is constructed inside the hole. The blasting sequence starts from the center of the tunnel blasting section, and then blasts outward layer by layer on both sides.

[0013] Furthermore, the number of blastholes is estimated, including:

[0014] Calculate unit explosive consumption:

[0015] q=q1ef1k cons

[0016] in:

[0017] q is the modified unit explosive consumption;

[0018] q1 is the uncorrected unit explosive consumption, which is taken as 0.1 times the rock strength coefficient;

[0019] e is the explosive conversion factor, which is the ratio of the explosive heat of TNT to the explosive heat of the explosive used;

[0020] f1 is the rock structure coefficient, which is 0.8 for dense rock, 1.1 for brittle rock, 1.3 for slate and rock with fine cracks, and 2.0 for viscous and porous rock;

[0021] k cons is the free surface coefficient, when there is one free surface, S is the free surface area, i.e. the blasting cross-sectional area of the tunnel;

[0022] Calculate the number of blastholes:

[0023]

[0024] in:

[0025] N is the number of blastholes;

[0026] α is the charge coefficient;

[0027] γ is the mass of explosive per meter of cartridge.

[0028] Furthermore, the hollow holes are arranged in two groups, each group includes four hollow holes evenly arranged in a vertical row, and the eight hollow holes are all located on the symmetry axis of the tunnel blasting section;

[0029] The first group of hollow holes is located in the middle of the tunnel blasting section, that is, the center of the tunnel blasting section; the second group of hollow holes is located in the center of the lower part of the tunnel blasting section.

[0030] Furthermore, three of the grooved holes are symmetrically arranged on both sides of each group of the hollow holes, and the three grooved holes are evenly arranged in a vertical row; the arrangement range of the grooved holes corresponds to the position between the second and third hollow holes from the top to the bottom;

[0031] The auxiliary slot holes are arranged on the outside of the slot holes, on both sides of the middle of the tunnel blasting section and on both sides of the bottom of the tunnel blasting section; the auxiliary slot holes on both sides are arranged in four layers from the inside to the outside, and each of the auxiliary slot holes in each layer is staggered in height.

[0032] Furthermore, three layers of the cave-in holes are arranged circumferentially on the upper part of the tunnel blasting section, and the cave-in holes in each layer are arranged along an arc.

[0033] Furthermore, the peripheral holes are circumferentially arranged on the edge of the arch portion of the tunnel blasting section and on both side edges of the tunnel blasting section, and peripheral auxiliary holes are circumferentially arranged inside the peripheral holes.

[0034] Furthermore, bottom plate holes are arranged at the bottom edge of the tunnel blasting section, and the bottom plate holes are evenly arranged in rows horizontally.

[0035] Furthermore, the charge quantity is estimated, including:

[0036] Q=qIS

[0037] in:

[0038] Q is the total charge in one blasting cycle;

[0039] I is the designed cycle footage.

[0040] Furthermore, the charge is continuously charged into the cutout hole, and the tail is blocked by an anchoring agent;

[0041] Charges are charged at intervals in the peripheral holes, explosives and water bags are arranged at intervals, and the tails are blocked by water bags;

[0042] Explosives are continuously charged into the auxiliary cutting hole, the collapse hole, the peripheral auxiliary hole and the bottom plate hole, and the tail is blocked by a water bag.

[0043] Furthermore, the detonation sequence is:

[0044] Cut holes;

[0045] From the inside to the outside, the first layer of auxiliary slot holes and the first layer of cave-in holes;

[0046] From the inside to the outside, the second layer of auxiliary slot holes, the third layer of auxiliary slot holes and the second layer of cave-in holes;

[0047] From the inside to the outside, there is the fourth layer of auxiliary slot holes and the third layer of cave-in holes;

[0048] peripheral auxiliary holes;

[0049] peripheral holes;

[0050] Bottom plate hole.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] The blasting method provided by the present invention greatly improves the blasting footage and effectively improves the blasthole utilization rate. The average cycle footage can reach 2.8 to 3.0 meters, the blasthole utilization rate is 93% to 96%, the excavation contour wall is flat and smooth, and there is no obvious "stagger" phenomenon between blasting cycles.

[0053] The blasting method provided by the present invention, on the basis of giving full play to the advantages of the three-arm rock drill equipment, overcomes the defect that it cannot realize oblique eye groove cutting. The three-arm rock drill is used in conjunction with the composite straight eye groove hydraulic smooth blasting operation, which significantly reduces labor, has high construction efficiency, low work intensity and higher engineering safety.

[0054] The blasting method provided by the present invention can save 0.25 hours of ventilation time per cycle and reduce the construction cost by approximately RMB 15,700, thereby reducing the construction cost, accelerating the construction progress, and effectively improving the economic efficiency of the project. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying any creative work, they can also obtain drawings of other embodiments based on these drawings.

[0056] Figure 1 It is a schematic diagram of the groove angle and groove hole arrangement of the rock drill in the present invention.

[0057] Figure 2 It is a schematic diagram of the blasthole arrangement in the present invention.

[0058] Figure 3 It is a schematic diagram of the arrangement of hollow holes and slotted holes in the present invention.

[0059] Figure 4 It is a schematic diagram of the charging structure of the slot hole in the present invention.

[0060] Figure 5 It is a schematic diagram of the peripheral hole charging structure in the present invention.

[0061] Figure 6 It is a schematic diagram of the charging structure of the collapse hole, peripheral auxiliary holes, auxiliary groove holes and bottom plate holes in the present invention. DETAILED DESCRIPTION

[0062] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present disclosure.

[0063] In the description of this patent, it should be understood that the terms "center", "both sides", "up", "down", "vertical", "lateral", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings. They are only for the convenience of describing this patent and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on this patent.

[0064] In the description of this patent, it should be noted that, unless otherwise expressly specified or limited, the terms "arranged" and "disposed" should be understood broadly. For example, they can refer to fixed connection or arrangement, detachable connection or arrangement, or integral connection or arrangement. Those skilled in the art will understand the specific meanings of the above terms in this patent based on the specific circumstances.

[0065] It should also be noted that although the steps are described in order, in some cases they may be performed in an order different from that shown, and this should not be construed as limiting the order of the steps.

[0066] In order to solve the practical engineering problems such as the inability of three-arm rock drills to realize oblique cuts in tunnels due to space limitations and the long ventilation time after blasting, the present invention provides a method for hydraulic smooth blasting of hollow holes in small-section tunnels with composite straight cuts. The three-arm rock drill, such as the CYT15-3 rock drill, has a propulsion beam length of 6.5m, a drilling diameter of 43-80mm, a drilling depth of 5.0m, and a maximum coverage area of 140m. 2 The rubber top plate of the propulsion beam is 4cm away from the rock wall (7.5cm for a typical drill rig and 5cm for an air gun), which can solve the problem of large external insertion angles. A detachable hanging basket is installed in front of the drilling arm to meet the requirements of drilling blastholes, geological exploration holes, hollow holes, etc. The method of the present invention, based on the construction of a three-arm rock drill, rationally optimizes the blasting parameters for small-section tunnels, making it possible to use the three-arm rock drill in blasting construction of small-section tunnels.

[0067] The method specifically includes:

[0068] S1: Arrange blast holes:

[0069] Estimate the number of blast holes and drill hollow holes, slot holes, auxiliary slot holes, collapse holes, peripheral holes, peripheral auxiliary holes and bottom plate holes on the tunnel blasting section.

[0070] The specific process of estimating the number of blastholes is as follows:

[0071] S101: Calculate unit explosive consumption:

[0072] q=q1ef1k cons

[0073] in:

[0074] q is the modified unit explosive consumption;

[0075] q1 is the uncorrected unit explosive consumption, which is taken as 0.1 times the rock strength coefficient;

[0076] e is the explosive conversion factor, which is the ratio of the explosive heat of TNT to the explosive heat of the explosive used;

[0077] f1 is the rock structure coefficient, which is 0.8 for dense rock, 1.1 for brittle rock, 1.3 for slate and rock with fine cracks, and 2.0 for viscous and porous rock;

[0078] k cons is the free surface coefficient, when there is one free surface, S is the free surface area, i.e. the blasting cross-sectional area of the tunnel;

[0079] S102: Calculate the number of blastholes:

[0080]

[0081] in:

[0082] N is the number of blastholes;

[0083] α is the charge coefficient;

[0084] γ is the mass of explosive per meter of cartridge.

[0085] Various types of blastholes are drilled in the tunnel blasting section using a three-arm rock drill. The specific layout is as follows:

[0086] (1) There are two groups of hollow holes, each group includes four hollow holes evenly arranged in a vertical row, and all eight hollow holes are located on the symmetry axis of the tunnel blasting section. The first group of hollow holes is located in the middle of the tunnel blasting section, that is, the center of the tunnel blasting section; the second group of hollow holes is located in the center of the lower part of the tunnel blasting section.

[0087] (2) Three slot holes are symmetrically arranged on both sides of each group of hollow holes, and the three slot holes are evenly arranged in vertical rows; the arrangement range of the slot holes corresponds to the position between the second and third hollow holes from the top to the bottom. Auxiliary slot holes are arranged on the outside of the slot holes, on both sides of the middle of the tunnel blasting section, and on both sides of the bottom of the tunnel blasting section; the auxiliary slot holes on both sides are arranged in four layers from the inside to the outside, and each auxiliary slot hole in each layer is staggered in height.

[0088] (3) There are three layers of collapse holes arranged in a circumferential direction on the upper part of the tunnel blasting section, and each layer of collapse holes is arranged along an arc.

[0089] (4) Peripheral holes are arranged circumferentially on the edge of the arch of the tunnel blasting section and on both sides of the tunnel blasting section, and peripheral auxiliary holes are arranged circumferentially on the inner side of the peripheral holes.

[0090] (5) Bottom plate holes are arranged at the bottom edge of the tunnel blasting section, and the bottom plate holes are evenly arranged in rows horizontally.

[0091] S2: Blast hole charge:

[0092] Estimate the charge quantity and use continuous or intermittent charging to load the blasthole. The blasting caps are installed at the bottom of the explosives for reverse detonation.

[0093] The specific process of estimating the charge amount is as follows:

[0094] Q=qIS

[0095] in:

[0096] Q is the total charge in one blasting cycle;

[0097] I is the designed cycle footage.

[0098] Different types of blastholes use different charging methods, specifically:

[0099] (1) Continuously charge the hole in the cutout, and plug the tail with anchoring agent;

[0100] (2) Charge explosives at intervals in the peripheral holes, with explosives and water bags arranged at intervals, and the tail end blocked by a water bag;

[0101] (3) Continuously charge the auxiliary cutting holes, collapse holes, peripheral auxiliary holes and bottom plate holes, and plug the tail with a water bag.

[0102] S3: Build the detonation network:

[0103] Construct a micro-difference detonation network in the hole, starting from the center of the tunnel blasting section, and then blasting outwards layer by layer on both sides. The specific detonation sequence is:

[0104] Cut holes;

[0105] From the inside to the outside, the first layer of auxiliary slot holes and the first layer of cave-in holes;

[0106] From the inside to the outside, the second layer of auxiliary slot holes, the third layer of auxiliary slot holes and the second layer of cave-in holes;

[0107] From the inside to the outside, there is the fourth layer of auxiliary slot holes and the third layer of cave-in holes;

[0108] peripheral auxiliary holes;

[0109] peripheral holes;

[0110] Bottom plate hole.

[0111] Example:

[0112] The following describes the specific implementation process of this method using a parallel pilot tunnel with a cross-sectional size of 6.5×6.5m in a plateau railway tunnel as an example:

[0113] First, design the blasting parameters:

[0114] 1. Unit explosive consumption:

[0115] The main factors affecting the unit consumption of explosives include the type of explosives, rock properties, the number of free surfaces, etc. The process of calculating the unit consumption of explosives is as follows:

[0116] q=q1ef1k cons

[0117] in:

[0118] q is the corrected unit explosive consumption, kg / m 3 ;

[0119] q1 is the uncorrected unit explosive consumption, kg / m 3 , take 0.1 times the rock strength coefficient;

[0120] e is the explosive conversion factor, which is the ratio of the explosive heat of TNT to the explosive heat of the explosive used;

[0121] f1 is the rock structure coefficient, which is 0.8 for dense rock, 1.1 for brittle rock, 1.3 for slate and rock with fine cracks, and 2.0 for viscous and porous rock;

[0122] k cons is the free surface coefficient, when there is one free surface, S is the free surface area, that is, the blasting cross-sectional area of the tunnel.

[0123] After calculation, the modified unit explosive consumption q of the project in this embodiment is 1.6 kg / m 3 .

[0124] 2. Number of blast holes:

[0125] The process of calculating the number of blastholes is:

[0126]

[0127] in:

[0128] N is the number of blastholes, excluding the number of empty holes without charge;

[0129] α is the charge coefficient;

[0130] γ is the mass of explosive per meter of cartridge, kg / m.

[0131] After calculation, the number N of blastholes in this embodiment is 148.3. Combining engineering experience and the actual situation of this project, it is rounded to 150. In addition, 8 large-diameter hollow holes need to be arranged, for a total of 158 blastholes.

[0132] 3. Charge quantity:

[0133] First, the charge amount for one cycle is calculated using the volume formula, then it is distributed according to the blasting characteristics of various types of blastholes, and then tested and corrected in blasting practice.

[0134] The specific process of estimating the charge amount is as follows:

[0135] Q=qIS

[0136] in:

[0137] Q is the total charge of one blasting cycle, kg;

[0138] I is the designed cycle footage, m.

[0139] After calculation, the charge amount Q of the project in this embodiment is 213.6 kg, which is rounded to 216 kg.

[0140] 4. Blasthole parameters:

[0141] Taking into account the geological conditions, section width, and the size of the drilling rig propulsion beam, this embodiment of the project combines the purpose of blasting construction and the equipment used, and adopts a solution of large-diameter hollow holes combined with multi-stage composite wedge-shaped slotting. Two groups of large-diameter hollow holes are arranged on the symmetry axis of the tunnel section, 150 cm apart. The lowest hollow hole is 100 cm away from the bottom plate hole. The two hollow holes in each group are 20 cm apart, and a row of small-diameter slotting holes is set 20 cm on both sides of the hollow holes. Multi-stage composite wedge-shaped slotting holes, i.e., auxiliary slotting holes, are set 150 cm on both sides of the two groups of large-diameter hollow holes. Figure 1The angles are 76°, 80°, 84°, and 88° respectively, and the lengths are 310cm, 305cm, 302cm, and 300cm respectively. The distance from the bottom of the hole is 73cm. The spacing between the upper and lower auxiliary slot holes is determined by the lithology and is 45cm. The lowest auxiliary slot hole is 50cm away from the bottom plate hole.

[0142] Peripheral auxiliary holes and caving holes are the primary blastholes for rock crushing, using a combination of stress waves and high-pressure gas. They are evenly arranged around the auxiliary cutouts. The spacing between holes and their rows depends primarily on the rock's uniaxial compressive strength, the degree of joint and fissure development, and the initial construction parameters. Taking these factors into account, the spacing between peripheral auxiliary holes and caving holes is 80-90 cm, and the spacing between caving holes in the upper section is 50 cm.

[0143] The peripheral holes are arranged on the boundary of tunnel excavation due to the low charge density and large decoupling coefficient. The calculation process of the peripheral hole spacing is as follows:

[0144] E=(8~12)db,db≥60mm

[0145] E=(9~14)db,db<60mm

[0146] in:

[0147] E is the distance between the peripheral holes, mm;

[0148] db is the charge diameter, mm. For uncoupled continuous charge structure, db is the charge diameter.

[0149] After calculation, the hole spacing E of the peripheral holes in this embodiment is 44.8 cm, and 45 cm is taken. The bottom of the hole is about 10 cm outside the excavation boundary, and the minimum resistance line value is 50 cm.

[0150] The bottom plate hole is at the bottom of the tunnel excavation section, with a later detonation sequence and a longer delay time. During blasting, there is a large amount of rock covering it, and it is subject to a greater clamping effect from the bottom. Therefore, the resistance to rock movement is greater, and the charge of the bottom plate hole should be appropriately increased compared to the peripheral holes to enhance the blasting effect. The design length of the bottom plate hole is 320cm, and the hole spacing is 80cm. According to the existing equipment of the project and the requirements for the construction error of the initial support and secondary lining thickness, the hole mouths and bottoms of the peripheral holes and bottom plate holes must be controlled on a line 5cm outside the design contour line. At the same time, the external insertion angle of the blasthole should be set outward at a slope of 3.3% in order to achieve a better over-excavation and under-excavation control effect.

[0151] After fine-tuning the calculated blasting parameters based on engineering construction experience, a blasthole layout diagram and a blasting parameter table are formed, such as Figure 2As shown in Table 1. The designed cycle excavation footage is 3m, with 158 blastholes per cycle. Among them: 8 large-diameter hollow holes with a diameter of 80mm; 12 small-diameter slot holes with a diameter of 42mm; four layers of auxiliary slot holes on both sides totaling 56, three layers of collapse holes totaling 13, 19 peripheral auxiliary holes, 40 peripheral holes, and 10 bottom plate holes, totaling 138, all with a diameter of 42mm. The peripheral hole spacing is 0.45m, the peripheral auxiliary hole spacing is 0.8m, the collapse hole spacing is 0.8m×0.5m, and the bottom plate hole spacing is 0.8m. The total drilling length is 572.64m, the total charge is 216kg, and the unit consumption of explosives is 1.6kg / m 3 The maximum number of blastholes in the same section, excluding the peripheral holes, is 19. The maximum charge in a single section is 36 kg, and the location where the maximum charge is generated is the peripheral holes. Figure 3 shown.

[0152] Table 1 Blasting parameters

[0153]

[0154]

[0155] 5. Charge:

[0156] The explosive used in the blasting operation is No. 2 rock emulsion explosive. The specifications of the explosive rolls used in all the charged blast holes are Φ32mm×300mm×0.3kg. The explosion is transmitted by detonating cord, and the detonating caps are installed at the bottom of the explosives for reverse detonation. The peripheral holes have a greater impact on the quality of the tunnel excavation profile, so interval charging is adopted; the charged blast holes other than the peripheral holes are charged continuously. At the same time, in order to reduce the loss of blasting energy, the tail of the slot hole is blocked with anchoring agent, and the blocking length is not less than 20cm; the remaining charged blast holes are blocked with water bags. For the specific charging structure, please refer to Figure 4 、 Figure 5 、 Figure 6 The specific methods of charging various types of blastholes are as follows:

[0157] (1) Continuously charge the hole in the cutout, and plug the tail with anchoring agent;

[0158] (2) Charge explosives at intervals in the peripheral holes, with explosives and water bags arranged at intervals, and the tail end blocked by a water bag;

[0159] (3) Continuously charge the auxiliary cutting holes, collapse holes, peripheral auxiliary holes and bottom plate holes, and plug the tail with a water bag.

[0160] 6. Detonating the Network:

[0161] Each charge hole adopts non-electric millisecond detonator micro-difference detonation technology to control the explosive quantity and detonation time of the single-section detonator, so that the blasting shock wave does not overlap, thereby reducing the damage to the surrounding rock. In order to ensure that the network detonated later is not broken by the network detonated earlier, a micro-difference detonation network is used in the hole. The detonation sequence starts from the charge hole near the large diameter hollow hole in the center of the cross section, and then the slot holes on both sides are blasted layer by layer outward, and finally the peripheral holes are detonated. The specific arrangement is as follows Figure 2 The specific detonation sequence is:

[0162] Cut holes;

[0163] From the inside to the outside, the first layer of auxiliary slot holes and the first layer of cave-in holes;

[0164] From the inside to the outside, the second layer of auxiliary slot holes, the third layer of auxiliary slot holes and the second layer of cave-in holes;

[0165] From the inside to the outside, there is the fourth layer of auxiliary slot holes and the third layer of cave-in holes;

[0166] peripheral auxiliary holes;

[0167] peripheral holes;

[0168] Bottom plate hole.

[0169] After blasting with this method, 18 consecutive blasting cycles were conducted. The single-cycle blasting footage reached 2.8 to 3.0 meters, and the blasthole utilization rate was 93% to 96%. The hole mark rate on the excavation contour surface reached over 95%, and the semi-hole rate was 85%. The excavation contour wall was flat and smooth, and there was no obvious "stagger" phenomenon between blasting cycles. The bottoms of the peripheral holes were mostly located 0.15 to 0.22 meters outside the excavation boundary, with an average linear over-excavation of about 15 cm. This effectively controlled the over-excavation and under-excavation of the surrounding rock and reduced the stress concentration of the surrounding rock. In addition, the initial support was separated from the face by a distance, which not only created sufficient space for blasthole drilling, ensuring that the blastholes could be drilled according to the designed angle, but also enabled the initial support to be applied in a centralized manner, greatly saving the process conversion time required for frequent initial support application and improving construction efficiency.

[0170] The above examples are used to illustrate the present invention, which are only used to help understand the present invention and are not intended to limit the present invention. Those skilled in the art can make several simple deductions, modifications or substitutions based on the concept of the present invention.

Claims

1. A composite straight-hole hydraulic smooth blasting method for hollow holes in small-section tunnels, characterized by: The method comprises: Arrange the blast holes: Estimate the number of blastholes and drill hollow holes, slot holes, auxiliary slot holes, cave-in holes, peripheral holes, peripheral auxiliary holes and bottom plate holes on the tunnel blasting section; Various types of blast holes are drilled in the tunnel blasting section by a three-arm rock drill; the hollow holes are arranged in two groups, each group includes four hollow holes arranged vertically and evenly, and the eight hollow holes are all located on the symmetry axis of the tunnel blasting section; the hollow holes in the first group are located in the center of the middle part of the tunnel blasting section, that is, the center of the tunnel blasting section; the hollow holes in the second group are located in the center of the lower part of the tunnel blasting section; three slot holes are symmetrically arranged on both sides of each group of hollow holes, and the three slot holes are evenly arranged vertically; the arrangement range of the slot holes corresponds to the position between the second and third hollow holes from top to bottom; multi-stage composite wedges are arranged on the outside of the slot holes, on both sides of the middle part of the tunnel blasting section and on both sides of the bottom of the tunnel blasting section The auxiliary slot holes are arranged in four layers from the inside to the outside, with angles of 76°, 80°, 84°, and 88°, respectively. The auxiliary slot holes in each layer are staggered in height. Three layers of collapse holes are arranged circumferentially on the upper part of the tunnel blasting section, and the collapse holes in each layer are arranged along an arc. The peripheral holes are arranged circumferentially on the edge of the arch of the tunnel blasting section and on both sides of the tunnel blasting section, and peripheral auxiliary holes are arranged circumferentially on the inner side of the peripheral holes. The bottom edge of the tunnel blasting section is arranged with bottom plate holes, and the bottom plate holes are evenly arranged in rows horizontally. The orifices and bottoms of the peripheral holes and bottom plate holes are all controlled on the connecting line 5 cm outside the design contour line, and the outer insertion angle of the blasthole is set outward at a slope of 3.3%. Blast hole charge: Estimate the charge quantity, use continuous charge or interval charge to load the blasthole, and install the blasting caps at the bottom of the explosives for reverse detonation; Continuously charging explosives in the cutout holes, with the tails blocked by anchoring agents; charging explosives at intervals in the peripheral holes, with explosives and water bags arranged at intervals, with the tails blocked by water bags; continuously charging explosives in the auxiliary cutout holes, the caving holes, the peripheral auxiliary holes, and the bottom plate holes, with the tails blocked by water bags; Building the detonation network: Construct a micro-difference detonation network within the hole. The detonation sequence starts from the center of the tunnel blasting section and then blasts outwards layer by layer on both sides. The detonation sequence is: Cut holes; From the inside to the outside, the first layer of auxiliary slot holes and the first layer of cave-in holes; From the inside to the outside, the second layer of auxiliary slot holes, the third layer of auxiliary slot holes and the second layer of cave-in holes; From the inside to the outside, there is the fourth layer of auxiliary slot holes and the third layer of cave-in holes; peripheral auxiliary holes; peripheral holes; Bottom plate hole.

2. The method according to claim 1, wherein: Estimate the number of blastholes, including: Calculate unit explosive consumption: in: To correct the unit explosive consumption; is the uncorrected unit explosive consumption, taking 0.1 times the rock strength coefficient; is the explosive conversion factor, which is the ratio of the explosive heat of TNT to the explosive heat of the explosive used; is the rock structure coefficient, which is 0.8 for dense rock, 1.1 for brittle rock, 1.3 for slate and rock with fine fractures, and 2.0 for viscous and porous rock; is the free surface coefficient, when there is one free surface, , is the free surface area, i.e. the blasting cross-sectional area of the tunnel; Calculate the number of blastholes: in: is the number of blastholes; is the charge coefficient; is the mass of explosive per meter of cartridge.

3. The method according to claim 2, wherein: Estimate charge quantity, including: in: is the total charge for one blasting cycle; This is the design cycle footage.

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