Construction method for induced blasting of damaged rock mass in large-section high in-situ stress tunnel

Abstract

The present invention relates to a construction method for induced blasting of damaged rock masses in large-section high in-situ stress tunnels. The steps of the construction method are as follows: prospect the site, consider the influence of high in-situ stress on the expansion of rock blasting cracks, divide the damaged rock masses in the large-section high in-situ stress tunnels, determine the envelope of single-hole blasting cracks, and then design the layout schemes of cut holes, auxiliary holes and perimeter holes; specifically arrange the positions of the cut holes, auxiliary holes and perimeter holes at the excavation face for lofting; perform positioning drilling on the face after lofting; charge the holes after positioning drilling; use the method of sectional and time-divided initiation to initiate the charged holes; muck and remove hazards. The present invention solves the problems that the existing blasting design has not considered the influence of high in-situ stress, resulting in serious overbreak and underbreak phenomena, uneven blasting contour and unsatisfactory smooth blasting effect during the tunnel excavation process.

Description

Technical Field

[0001] The present invention relates to a method for induced blasting of damaged rock mass in a large-section high in-situ stress tunnel, mainly aiming at the excavation project of large-section deep-buried tunnels. Background Art

[0002] At present, China has become the country with the largest scale of tunnel construction, the highest construction difficulty, and the fastest development quality in the world. Tunnel excavation is the prerequisite for the implementation of work such as support, transportation, and line operation. The quality of tunnel excavation directly affects the subsequent construction quality and speed. Improving the excavation quality of tunnels is of great significance for accelerating the tunnel construction progress and enhancing the economic benefits of tunnel excavation. Among them, there are greater risk factors and more problems in the tunneling work of large-section deep-buried tunnels.

[0003] In the tunneling work of large-section deep-buried tunnels, the most commonly used tunneling method is the drill-and-blast method. The drill-and-blast method is the most commonly used construction method in China's mountain tunnel excavation projects at present due to its strong geological adaptability, low excavation cost, convenient and flexible construction, etc. The blasting excavation link among them is an issue that must be considered when designing tunnel excavation. Smooth blasting can not only reduce the damage range of tunnel surrounding rock, control the overbreak and underbreak amount, but also make the tunnel excavation contour smooth and flat, ensuring the integrity and self-bearing capacity of the surrounding rock. However, due to the complexity of geological conditions and the uncertainty of the rock-breaking mechanism of explosives, problems such as serious overbreak and underbreak phenomena, uneven blasting contours, and unsatisfactory smooth blasting effects still exist during the tunnel excavation process due to unreasonable blasting design and improper blasting construction. Due to the large tunnel section, the clamping effect between rocks during blasting is obvious, which will lead to poor blasting effects, directly affecting the cycle footage or tunneling speed and resulting in reduced construction efficiency. In addition, in deep-buried high in-situ stress tunnels, the high in-situ stress has a great influence on blasting. At present, the blasting design parameters of the drill-and-blast method do not take into account the influence of high in-situ stress, and mostly follow or refer to the blasting design methods for shallow rock masses, which to a certain extent affects the blasting forming contour of deep-buried tunnels and the degree of damage to the surrounding rock. In serious cases, it may even trigger engineering dynamic disasters of deep rock masses. Therefore, the blasting design and construction for large-section deep-buried tunnels are particularly important. Summary of the Invention

[0004] Object of the Invention:

[0005] The present invention proposes a method for excavating and constructing induced blasting of damaged rock mass in a large-section high in-situ stress tunnel. Its purpose is to solve the problems such as serious overbreak and underbreak phenomena, uneven blasting contours, and unsatisfactory smooth blasting effects still existing during the tunnel excavation process due to the fact that the existing blasting design does not take into account the influence of high in-situ stress.

[0006] Technical Solution:

[0007] A construction method for induced blasting of damaged rock mass in a large-section high in-situ stress tunnel, the steps are as follows:

[0008] Step 1: Conduct exploration on the site, consider the influence of high in-situ stress on the crack propagation of rock blasting, divide the damaged rock mass in the large-section high in-situ stress tunnel, and determine the envelope of single-hole blasting cracks; then design the layout schemes of cut holes, auxiliary holes and perimeter holes;

[0009] Step 2: Layout the specific positions of the cut holes, auxiliary holes and perimeter holes at the excavation face for lofting; Step 3: Drill positioning holes on the lofted face;

[0010] Step 4: Charge the holes after positioning drilling;

[0011] Step 5: Use the method of sectional and time-divided initiation to initiate the charged holes;

[0012] Step 6: Muck out and remove risks.

[0013] Beneficial effects:

[0014] 1. The present invention includes the perimeter hole design scheme. Considering that the initial in-situ stress field of deep rock is relatively complex, with the excavation of the tunnel, the stress states of rock masses at different positions are different, showing different mechanical behaviors under the blasting disturbance of the working face. According to the specific differences, a specific perimeter hole layout scheme is formulated to effectively reduce the amount of explosive used by reducing the number of blast holes and ensure the blasting forming quality.

[0015] 2. The present invention includes the auxiliary hole design scheme. The induced effect of high in-situ stress after the initiation of the perimeter holes is fully considered, and the auxiliary holes are arranged in the intact rock mass area, which not only improves the blasting forming quality, but also reduces the number of blast holes and the amount of explosive used; in addition, considering that the unit explosive consumption in the auxiliary holes increases at a relatively large rate with the increase of high in-situ stress, the present invention selects high-velocity explosives to increase the blasting load value of the explosive acting on the rock in the auxiliary hole wall, thereby achieving the purpose of reducing the amount of explosive used.

[0016] 3. The present invention includes the cut hole design scheme, and proposes the blasting design concept of the inner cut hole and the auxiliary cut hole cooperating with the main cut hole to achieve a better cut effect. Among them, the inner cut hole provides a free face for the main cut hole; the main cut hole has a larger depth, which directly determines the cut depth and provides a free face for the initiation of subsequent blast holes; the auxiliary cut hole is used to continue to expand the cavity and provide a free face for the initiation of subsequent auxiliary holes.

[0017] 4. In the present invention, the blasting design adopts the induced blasting design for the damaged rock mass zoning in the large-section high in-situ stress tunnel. By carrying out zoned blasting on the upper bench, it can effectively solve the negative impact of the rock clamping effect often occurring in the tunneling project of large-section deep tunnels on blasting, so as to improve the blasting forming quality. In terms of the blast hole design, the induced effect of the high in-situ stress after the perimeter holes are blasted is fully utilized to achieve the purpose of reducing the blast holes and effectively reducing the explosive consumption.

[0018] 5. The present invention describes in detail each construction process of lofting, drilling, charging, and initiating. The perimeter holes adopt the pre-splitting blasting charging structure, and the other blast holes adopt the smooth blasting charging structure, forming several closed cracks on the blasting excavation contour line of the tunnel section to separate the planned excavated rock from the surrounding rock, effectively reducing the clamping effect of the surrounding rock on the rock within the blasting contour line during the blasting process. By controlling the connecting detonators of the upper bench and the lower bench, the millisecond blasting between different types of blast holes and between different blast holes of the same type is realized.

[0019] In summary, the present invention is applicable to most large-section deep-buried tunnel excavation projects. Brief Description of the Drawings

[0020] Figure 1 It is a schematic diagram of the high in-situ stress distribution state;

[0021] Figure 2 It is the layout diagram of the perimeter holes under the influence of high in-situ stress in the embodiment of the present invention.

[0022] Figure 3 It is the schematic diagram of the excavation sequence of each blast hole in the embodiment of the present invention;

[0023] Figure 4 It is the schematic diagram of the plane layout of the cut holes in the embodiment of the present invention;

[0024] Figure 5 It is the schematic diagram of the footage depth layout of the cut holes in the embodiment of the present invention;

[0025] Figure 6 It is the schematic diagram of the layout of each blast hole in the embodiment of the present invention;

[0026] Figure 7 It is the schematic diagram of the layout of the auxiliary holes in the upper left blasting area in the embodiment of the present invention;

[0027] Figure 8 It is the schematic diagram of the layout of the auxiliary holes in the left blasting area in the embodiment of the present invention;

[0028] Figure 9 It is the schematic diagram of the layout of the auxiliary holes in the lower bench of the tunnel in the embodiment of the present invention;

[0029] Figure 10 It is the schematic diagram of the distribution state of the rock mass of the blast hole surrounding rock affected by the blasting in the previous cycle in the embodiment of the present invention;

[0030] Figure 11 This is the initiation network diagram of the perimeter holes in the embodiment of the present invention;

[0031] Figure 12 This is the initiation network diagram of the cut holes and the auxiliary holes in the embodiment of the present invention;

[0032] Figure 13 This is the schematic diagram of the influence of high in-situ stress on the formation of the standard blasting crater;

[0033] The reference numerals are shown as:

[0034] 1. First heading face; 2. Second heading face; 3. Third heading face; 4. Test hole; 5. Envelope line of the single-hole blasting crack in the first stage; 6. Envelope line of the single-hole blasting crack in the stress-free state; 7. Envelope line of the single-hole blasting crack in the second stage; 8. Tunnel center line; 9. Blasting excavation area of the perimeter holes; 10. Perimeter holes in the vertical direction; 13. Perimeter holes in the tunnel arch; 14. Perimeter holes at the bottom of the tunnel; 15. Perimeter holes in the side wall in the first stage; 16. Perimeter holes in the side wall in the second stage; 17. Perimeter holes in the horizontal direction; 18. Upper left blasting area; 19. Upper right blasting area; 20. Middle blasting area; 21. Left blasting area; 22. Right blasting area; 23. Blasting area of the lower bench of the tunnel; 24. Inner cut holes; 25. Main cut holes; 26. Auxiliary cut holes; 27. Tunnel heading face; 28. Auxiliary holes; 29. Strong unloading and relaxation area; 30. Weak unloading and relaxation area; 31. Micro unloading and relaxation area; 32. Intact rock mass area; 33. Fragmentation area; 34. Fracture area; 35. Surrounding rock area; 36. Original rock area; 37. Blasthole; 38. First perimeter hole; 39. Second perimeter hole; 40. Third perimeter hole; 41. Fourth perimeter hole; 42. Fifth perimeter hole;

[0035] 501. External detonator in the first area; 502. External detonator in the second area; 503. External detonator in the third area; 504. External detonator in the fourth area; 505. External detonator in the fifth area; 506. Detonator for initiating the upper bench; 507. Detonator for initiating the lower bench; 508. External detonator in the sixth area; 509. External detonator in the seventh area; 510. External detonator in the eighth area; 511. External detonator in the ninth area; 512. External detonator in the tenth area; 513. External detonator in the eleventh area; 514. External detonator in the middle blasting area; 515. External detonator in the twelfth area. Detailed implementation manners

[0036] The present invention will be described in more detail below with reference to the accompanying drawings of the specification.

[0037] The present invention takes into account the influence of high in-situ stress on crack propagation during blasting, reduces the clamping effect of surrounding rock during large-section blasting, and points out the specific layout schemes for perimeter holes, cut holes, and auxiliary holes in combination with different surrounding rock firmness coefficients. Among them, the distribution state of high in-situ stress at different positions is fully considered, the layout scheme of perimeter holes is formulated according to specific differences, and the hole spacing of perimeter holes at the boundary of each blasting area is adjusted in combination with the distribution state of high in-situ stress; in the design scheme of auxiliary holes, in combination with the induced effect of high in-situ stress after the perimeter holes are detonated, the auxiliary holes are arranged in the intact rock mass area to achieve the purpose of reducing the number of blast holes. At the same time, considering that the unit consumption of explosive in the auxiliary holes increases at a relatively large rate with the increase of high in-situ stress, the present invention uses explosives with a higher detonation velocity to increase the blasting load value of the explosive acting on the rock in the auxiliary hole wall, thereby achieving the purpose of reducing the amount of explosive used; in the design scheme of cut holes, the cut blasting concept of internal cut holes and auxiliary cut holes cooperating with the main cut holes is proposed. The perimeter holes adopt the pre-splitting blasting charging structure, and the remaining blast holes adopt the smooth blasting charging structure. At the same time, in combination with millisecond blasting, after the perimeter holes are detonated, several closed cracks are formed to reduce the contact between the excavated rock mass and the surrounding rock, so as to reduce the clamping effect of the deep rock mass in the large section. This construction method is applicable to most large-section deep-buried tunnel blasting projects.

[0038] The present invention provides an excavation construction method for induced blasting of damaged rock mass in a large-section high-in-situ stress tunnel, and its steps are as follows:

[0039] Step 1: Conduct exploration on the site, consider the influence of high in-situ stress on the expansion of rock blasting cracks, and design the layout schemes for cut holes, auxiliary holes, and perimeter holes.

[0040] Considering the influence of high in-situ stress on the expansion of rock blasting cracks, the influence of high in-situ stress on the expansion of rock blasting cracks specifically includes the influence on crack length and crack propagation direction. Design the layout schemes for cut holes, auxiliary holes, and perimeter holes, and conduct lofting, drilling, charging, and detonation on the cut holes, auxiliary holes, and perimeter holes to complete the sectional blasting.

[0041] The initial in-situ stress field of deep rocks is relatively complex, and there have been many reports analyzing and studying the dynamic characteristics of rocks under various initial in-situ stress states. However, for the rock mass of tunnels and underground projects, the rocks are often under the action of triaxial unequal stress non-hydrostatic pressure. With the excavation of the tunnel, the stress states of the rock mass at different positions are different, and different mechanical behaviors are shown under the blasting disturbance of the working face.

[0042] Such as Figure 1As shown, the initial in-situ stress field of deep rocks is relatively complex, and there have been many reports analyzing and studying the dynamic characteristics of rocks under various initial in-situ stress states. However, for rock masses in tunnels and underground engineering, the rocks are often under non-hydrostatic pressure of triaxial unequal stresses. With the excavation of the tunnel, the stress states of rock masses at different positions are different, and they show different mechanical behaviors under the blasting disturbance of the working face.

[0043] See Figure 1 , combined with the fact that the stress states of the rocks at the actual first heading face 1, the second heading face 2, and the third heading face 3 are all different, and moreover, the stress states of the rocks at different regions of the second heading face 2, which is the excavation heading face, are also different. Aiming at different high in-situ stress distribution states, analyze their influence on crack propagation, and combined with Figure 1 give a brief introduction to the high in-situ stress distribution states. The different high in-situ stress distribution states specifically include: the in-situ stress σ v in the vertical direction is greater than the in-situ stress σ h in the horizontal direction, where the in-situ stress σ v in the vertical direction is the maximum principal stress; the in-situ stress σ h in the horizontal direction is greater than the in-situ stress σ v in the vertical direction, where the in-situ stress σ h in the horizontal direction is the maximum principal stress.

[0044] Optionally, as Figure 1 shown, set a test hole 4 at the second heading face 2 and conduct blasting on it. Combine with the crack envelope 6 after blasting under the condition of no in-situ stress, and then analyze the influence of high in-situ stress on the crack envelope of a single blast hole. In contrast, when σ v >σ h , the crack length in the vertical direction increases, and the crack length in the horizontal direction decreases. The crack envelope after blasting is mainly elliptical, with the major axis along the vertical direction and the minor axis along the horizontal direction. This is the first single-hole blast crack envelope 5 under this high in-situ stress state.

[0045] As Figure 1 shown, in contrast, when σ h >σ v , combine with the crack envelope 6 after blasting under the condition of no in-situ stress, and then analyze the influence of high in-situ stress on the crack envelope of a single blast hole. The crack length in the horizontal direction increases, and the crack length in the vertical direction decreases. The crack envelope after blasting is mainly elliptical, with the major axis along the horizontal direction and the minor axis along the vertical direction. This is the second single-hole blast crack envelope 7 under this high in-situ stress state.

[0046] The method proposed by the present invention needs to combine the crack envelope of a single blast hole after the combined action of high in-situ stress and blasting obtained through test holes on-site. This embodiment only takes σ v >σ hTaking one of the high ground stress distribution states as an example for introduction, without involving specific numerical values and not representing that it is only applicable to this high ground stress distribution state. On the contrary, the inventive solution is applicable to the blasting design scheme of deep-buried tunnels under any high ground stress distribution state, specifically including taking σ v > σ h , σ h > σ v as the main any high ground stress distribution state, the blasting design principle of which is exactly the same as that introduced in the inventive solution and will not be elaborated one by one. Taking σ v > σ h as an example, make full use of the characteristic that the crack envelope line after single-hole blasting is elliptical under the influence of high ground stress, optimize the design scheme of the perimeter holes, appropriately change the position of the perimeter holes, reduce the amount of explosive used, and improve the blasting forming quality.

[0047] Specifically, the inventive solution needs to know in advance the high ground stress distribution state on site, etc., and combine with numerical simulation software to simulate the blasting process under the combined action of high ground stress and explosive charge, and further analyze to obtain the single-hole blasting crack envelope line, specifically observing the main crack length, the main crack propagation direction, and the long and short axis orientations of the crack envelope line.

[0048] As Figure 2-3 and Figure 6 shown, the damaged rock mass partition of the large-section high ground stress tunnel in step 1 is as follows: divide the second heading face 2 into the upper bench and the lower bench 23 of the heading face. The upper bench of the heading face is divided into the upper layer and the lower layer according to the ratio of 2:3 of the length of the tunnel center line 8. The upper layer is divided into the upper left blasting area 18 and the upper right blasting area 19, and the upper left blasting area 18 and the upper right blasting area 19 are symmetric structures with respect to the tunnel center line 8. The lower layer is divided into the middle blasting area 20, the left blasting area 21, and the right blasting area 22. The left blasting area 21 and the right blasting area 22 are respectively located on the left and right sides of the middle blasting area 20. The middle blasting area 20 is a symmetric structure with respect to the tunnel center line 8. The left blasting area 21 and the right blasting area 22 are symmetric structures with respect to the tunnel center line 8. The area occupied by each blasting area is basically the same.

[0049] The holes opened on the outer periphery of all the above areas are perimeter holes. The perimeter holes specifically include the tunnel arch perimeter holes 13, the tunnel bottom perimeter holes 14, the tunnel sidewall perimeter holes (the first-stage perimeter holes 15 and the second-stage perimeter holes 16), and the perimeter holes at the dividing lines of each blasting area (the vertical perimeter holes 10 and the horizontal perimeter holes 17); specifically, the tunnel arch perimeter holes 13 are arranged on the tunnel arch; the tunnel bottom perimeter holes 14 are arranged at the tunnel bottom; the first-stage perimeter holes 15 and the second-stage perimeter holes 16 are arranged on the tunnel sidewall from top to bottom; the horizontal perimeter holes 17 are transversely opened between each blasting area, and the vertical perimeter holes 10 are longitudinally arranged.

[0050] The holes set in the upper left blasting area 18, upper right blasting area 19, left blasting area 21, right blasting area 22, and lower bench 23 are auxiliary holes 28;

[0051] The holes set in the middle blasting area 20 are cut holes, and the cut holes specifically include inner cut holes 24, main cut holes 25, and auxiliary cut holes 26.

[0052] 1.1 Peripheral hole blasting design scheme

[0053] Combining several peripheral hole combinations with the first single-hole blasting crack envelope 5, and making full use of the blasting energy generated by the blasting of the explosive packages in each peripheral hole to achieve the effect of penetration after the blasting of each peripheral hole.

[0054] In the solution of the present invention, the peripheral hole combinations include the combinations of the peripheral holes at the blasting excavation contour line and the combinations of the peripheral holes at the boundaries of each blasting area. That is, the peripheral holes 13 at the arch of the tunnel, the peripheral holes 14 at the bottom of the tunnel, the peripheral holes on the side walls of the tunnel (the first-stage peripheral holes 15 and the second-stage peripheral holes 16), and the peripheral holes at the boundaries of each blasting area (the vertical peripheral holes 10 and the horizontal peripheral holes 17).

[0055] Aiming at different high in-situ stress distribution states, analyze its influence on crack propagation, and further determine the peripheral hole layout scheme in combination with the peripheral hole spacing obtained from the empirical formula.

[0056] According to the empirical formula, the peripheral hole spacing can be obtained from the following formula:

[0057] a = 10 - 15d

[0058] In the formula: a is the peripheral hole spacing; d is the peripheral hole diameter.

[0059] The peripheral hole diameter is selected to be 40 - 70 mm. The peripheral hole spacing is 40 - 105 cm.

[0060] ① Combinations of peripheral holes at the blasting excavation contour line

[0061] For the combination of the perimeter holes at the blasting excavation contour line, including the perimeter holes 13 in the tunnel arch, the perimeter holes 14 at the tunnel bottom, and the perimeter holes on the tunnel sidewalls (the first-stage perimeter holes 15 and the second-stage perimeter holes 16), the arrangement of all the above perimeter holes is not on the same arc. Specifically, according to the single-hole blasting crack envelope, the positions of several perimeter holes are adjusted to make full use of the explosives in each blast hole and ensure the effective solution of overbreak and underbreak problems. In the perimeter hole blasting excavation area 9, on both sides of the tunnel center line 8, each adjacent perimeter hole is on the first arc 11 and the second arc 12, and from the tunnel arch and the tunnel bottom to the tunnel sidewalls, all the perimeter holes tend to be on the same arc. Specifically, each adjacent perimeter hole is on the same arc, while at the tunnel sidewalls, each adjacent perimeter hole tends to be on the same arc, rather than on the same arc, that is, from the tunnel arch and the tunnel bottom to the tunnel sidewalls, each adjacent perimeter hole tends to be on the same arc. The first arc and the second arc are two different arcs where the adjacent perimeter holes are located. Taking advantage of the fact that in the high in-situ stress distribution state of σ v >σ h , the crack length within the single-hole blasting crack envelope shows the advantage that the vertical direction is greater than the horizontal direction. By arranging the perimeter holes in the above way, each perimeter hole is more penetrating after blasting, which can effectively improve the blasting forming quality and ensure the smoothness of the blasting excavation contour line.

[0062] ② The combination of the perimeter holes at the blasting area boundary (the perimeter holes 10 in the vertical direction at each blasting area boundary and the perimeter holes 17 in the horizontal direction at each blasting area boundary)

[0063] For the combination of the perimeter holes at each blasting area boundary (the perimeter holes 10 in the vertical direction at each blasting area boundary and the perimeter holes 17 in the horizontal direction at each blasting area boundary), when σ v >σ h , since the crack envelope after single-hole blasting is elliptical and the major axis is along the vertical direction, the spacing of the perimeter holes 10 at this stage in the vertical direction is appropriately increased to achieve the effect of reducing the blast holes, while ensuring the blasting forming quality.

[0064] As Figure 2 shown, combining the single-hole blasting-induced crack envelope 5 under the influence of high in-situ stress and the above-mentioned perimeter hole spacing to determine the perimeter hole arrangement plan. According to the σ v >σ h situation mentioned in the solution of the present invention, the perimeter hole arrangement plan is specifically as follows:

[0065]

[0066] Specifically: when the rock mass firmness coefficient is 2 - 6, it is recommended that the circumferential distance between adjacent peripheral holes (tunnel arch peripheral holes 13, tunnel bottom peripheral holes 14, first-stage sidewall peripheral holes 15, second-stage sidewall peripheral holes 16) on the same arc (first arc 11, second arc 12) at the excavation contour line is 80 - 90 cm, the distance between adjacent peripheral holes 10 in the vertical direction at the boundary of each blasting area is 90 - 105 cm, and the distance between adjacent peripheral holes 17 in the horizontal direction at the boundary of each blasting area is 80 - 90 cm;

[0067] When the rock mass firmness coefficient is 6 - 10, it is recommended that the circumferential distance between adjacent peripheral holes (tunnel arch peripheral holes 13, tunnel bottom peripheral holes 14, first-stage sidewall peripheral holes 15, second-stage sidewall peripheral holes 16) on the same arc (first arc 11, second arc 12) at the excavation contour line is 70 - 80 cm, the distance between adjacent peripheral holes 10 in the vertical direction at the boundary of each blasting area is 80 - 90 cm, and the distance between adjacent peripheral holes 17 in the horizontal direction at the boundary of each blasting area is 60 - 80 cm;

[0068] When the rock mass firmness coefficient is 10 - 16, it is recommended that the circumferential distance between adjacent peripheral holes (tunnel arch peripheral holes 13, tunnel bottom peripheral holes 14, first-stage sidewall peripheral holes 15, second-stage sidewall peripheral holes 16) on the same arc (first arc 11, second arc 12) at the excavation contour line is 50 - 70 cm, the distance between adjacent peripheral holes 10 in the vertical direction at the boundary of each blasting area is 60 - 80 cm, and the distance between adjacent peripheral holes 17 in the horizontal direction at the boundary of each blasting area is 50 - 60 cm;

[0069] When the rock mass firmness coefficient is 16 - 20, it is recommended that the circumferential distance between adjacent peripheral holes (tunnel arch peripheral holes 13, tunnel bottom peripheral holes 14, first-stage sidewall peripheral holes 15, second-stage sidewall peripheral holes 16) on the same arc (first arc 11, second arc 12) at the excavation contour line is 40 - 50 cm, the distance between adjacent peripheral holes 10 in the vertical direction at the boundary of each blasting area is 50 - 60 cm, and the distance between adjacent peripheral holes 17 in the horizontal direction at the boundary of each blasting area is 40 - 50 cm.

[0070] 1.2 Cut hole blasting design scheme

[0071] As Figure 3 shown, the cut holes include inner cut holes 24, main cut holes 25 and auxiliary cut holes 26. The middle blasting area 20 is evenly divided into two areas with the tunnel center line 8 as the center line. In the two areas, three rows of holes are drilled from the tunnel center line 8 to both sides, and from the inside to the outside are inner cut holes 24, main cut holes 25 and auxiliary cut holes 26.

[0072] The cut blasting design scheme specifically includes determining the parameters of the inner cut holes 24, main cut holes 25, and auxiliary cut holes 26. Among them, the function of the inner cut holes 24 is to provide a free face for the main cut holes 25 after blasting. In the blasting design for soft rock, the inner cut holes 24 can be not considered; the function of the main cut holes 25 is to detonate immediately after the inner cut holes 24, and use their greater depth to provide a deeper free face for the subsequent blasting of each blast hole. The main cut holes 25 ensure the single-pass depth; the function of the auxiliary cut holes 26 is to detonate immediately after the main cut holes 25, continue to expand the cut cavity, and provide a larger free face for the subsequent detonation of the auxiliary holes.

[0073] Combined with Figure 4 、 Figure 5 As shown, in the above cut blasting design scheme, the drilling diameter of the cut holes is selected as 40 - 42 mm; the single-cycle advance is selected in the following range: for relatively soft rock, it is 4 - 5 m, and for hard rock, it is 2 - 3 m.

[0074] 1.2.1 Design of the inner cut holes 24

[0075] The design (not required for soft rock) parameters of the inner cut holes 24 specifically include: the depth L1 of the inner cut holes 24, the bottom distance c1 between the paired inner cut holes 24, the angle α1 between the inner cut holes 24 and the tunnel face, the spacing a1 of the inner cut holes 24, the length L1 / cosα1, and the opening distance b1.

[0076] See Figure 5 , the depth L1 of the inner cut holes 24 is selected as 2 / 3 of the depth L2 + L3 of the main cut holes 25, where L2 is the depth of the auxiliary cut holes and L3 is the overbreak depth of the main cut holes.

[0077] The bottom distance c1 of the inner cut holes 24 is selected in the range of 17 - 42 cm, among which, for medium-hard rock, it is 25 - 42 cm; for hard rock, it is 15 - 25 cm, and its value decreases as the rock hardness increases.

[0078] The angle α1 between the inner cut holes 24 and the tunnel face 27 decreases as the rock hardness increases.

[0079] The hole spacing a1 of the inner cut holes 24 is selected in the following range: for medium-hard rock (surrounding rock firmness coefficient is 6 - 10), it is 43 - 51 cm; for hard rock (surrounding rock firmness coefficient is 10 - 20), it is 34 - 43 cm.

[0080] See Figure 4 、 Figure 5 , for the selection of each parameter of the inner cut holes 24, it specifically includes:

[0081]

[0082] The length L1 / cosα1 of the inner cut hole 24 and the opening distance b1 can be determined by determining the above information, that is, the opening distance b1 of the inner cut hole (24) = (L1 / tanα1)×2 + c1;

[0083] 1.2.2 Design of the main cut hole 25

[0084] The design parameters of the main cut hole 25 specifically include the bottom distance c2 of the main cut hole 25, the included angle α2 between the main cut hole 25 and the heading face 27, the overbreak depth L3, the hole spacing a2 of the main cut hole 25, the length (L2 + L3) / cosα2, and the opening distance (b1 + 2b2).

[0085] As Figure 5 shown, the bottom distance c2 of the main cut hole 25 is generally selected as 17 - 56 cm, and the higher the rock firmness coefficient, the smaller its value.

[0086] The included angle α2 between the main cut hole 25 and the heading face 27 decreases as the rock hardness increases.

[0087] The overbreak depth L3 of the main cut hole 25 increases as the rock firmness coefficient increases.

[0088] The main cut hole 25 plays a decisive role in the cut blasting effect. In the blasting design for harder surrounding rocks, if the hole spacing of the main cut hole 25 is large, the general cut effect is poor.

[0089] See Figure 4 、 Figure 5 For the selection of various parameters of the main cut hole 25, specifically including:

[0090]

[0091] The length (L2 + L3) / cosα2 and the opening distance (b1 + 2b2) of the main cut hole 25 can be determined by determining the above information. Among them, (L2 + L3) is the depth of the main cut hole, b1 = (L1 / tanα1)×2 + c1, and b2 = [2×(L2 + L3) / tanα2 + c2 - b1] / 2.

[0092] 1.2.3 Design of the auxiliary cut hole 26

[0093] The design parameters of the auxiliary cut hole 26 (not required for soft rocks) specifically include the hole spacing a3 of the auxiliary cut hole 26, the row spacing b2 between the inner cut hole 24 and the main cut hole 25, the row spacing b3 between the main cut hole 25 and the auxiliary cut hole 26, the included angle α3 between the auxiliary cut hole 26 and the heading face 27, and the length L2 / cosα3 of the auxiliary cut hole 26.

[0094] As Figure 4As shown, the auxiliary cut holes 26 mainly play the role of further expanding the cut cavity, providing a larger free face for the subsequent blasting of the auxiliary holes. The higher the hardness of the surrounding rock, the smaller the hole spacing of the auxiliary cut holes.

[0095] As Figure 5 shown, the row spacing b2 between the main cut holes 25 and the inner cut holes 24 = (the opening distance of the main cut holes (b1 + 2b2) - the opening distance of the inner cut holes b1) / 2.

[0096] The row spacing b3 between the auxiliary cut holes 26 on the heading face and the holes in its front row is selected as the equal division of the distance between the auxiliary holes and the main cut holes, which is affected by the hardness of the surrounding rock.

[0097] Similarly, the selected range of the bottom row spacing d of the auxiliary cut holes is 65 - 120 cm.

[0098] See Figure 4 、 Figure 5 , the specific selection of the parameters of the auxiliary cut holes 26 includes:

[0099]

[0100]

[0101] The included angle α3 between the auxiliary cut holes 26 and the heading face 27 can be determined through the above row spacing.

[0102] The design parameters of the auxiliary cut holes (26) specifically include the hole spacing a3 of the auxiliary cut holes (26), the row spacing b2 between the inner cut holes (24) and the main cut holes (25), the row spacing b3 between the main cut holes (25) and the auxiliary cut holes (26), the included angle α3 between the auxiliary cut holes (26) and the heading face (27), and the length L2 / cosα3 of the auxiliary cut holes (26);

[0103] where: b2 = [2×(L2 + L3) / tanα2 + c2 - b1] / 2; α3 = arctan[L2 / (b3 + L2 / tanα2 - d)];

[0104] Furthermore, the depths of the auxiliary cut holes 26 and the auxiliary holes 28 are the same. Among them, the auxiliary holes 28 are used to further expand the free face formed by the blasting of the cut holes (inner cut holes 24, main cut holes 25, auxiliary cut holes 26). The length of the auxiliary cut holes 26 can be determined by determining the depth of the auxiliary holes 28 and the included angle α3 between the auxiliary cut holes 26 and the heading face 27.

[0105] 1.3 Blasting design scheme of the auxiliary holes 28

[0106] The present invention makes full use of the unloading effect of the rock after blasting under the influence of high in-situ stress to achieve the effect of reducing the number of blast holes, specifically as follows:

[0107] Combined withFigure 7 , Figure 8 , Figure 9 , under the influence of high in-situ stress, each blasting area is divided into four regions after the perimeter holes are blasted. Among them, Figure 7 is the upper left blasting area 18, which is exactly the same as the upper right blasting area 19; Figure 8 is the left blasting area, which is exactly the same as the right blasting area; Figure 9 is the blasting area on the left side of the center line of the lower bench tunnel, which is exactly the same as the blasting area on the right side of the center line of the lower bench tunnel. After blasting, the rock mass in each blasting area can be divided into four regions, specifically including the strong unloading and relaxation zone 29, the weak unloading and relaxation zone 30, the micro-unloading and relaxation zone 31, and the intact rock mass zone 32. Among them, the rock mass in the strong unloading and relaxation zone 29 has been broken and relaxed under the influence of blasting construction and has lost its self-stabilizing ability; the rock mass in the weak unloading and relaxation zone 30 is severely damaged under the influence of blasting construction, the rock mass structure in this area has changed, and the surrounding rock has poor self-stabilizing ability; the degree of rock damage in the micro-unloading and relaxation zone 31 is relatively light, the crack spacing is relatively large, the rock mass structure has a certain degree of relaxation, and the surrounding rock still has self-stabilizing ability; the rock in the intact rock mass zone 32 is basically not affected by the blasting construction excavation and stress adjustment unloading and relaxation. The original rock fractures in this area are well cemented and tightly compacted.

[0108] Combining the above 4 regions, a layout design for the auxiliary holes 28 is carried out. Specifically, it can be divided into Scheme 1: All the auxiliary holes 28 are set in the intact rock mass zone 32; Scheme 2: The auxiliary holes 28 are arranged in the intact rock mass zone 32 and the micro-unloading and relaxation zone 31; Scheme 3: The auxiliary holes 28 are arranged in the remaining 3 regions except the strong unloading and relaxation zone 29; Scheme 4: The auxiliary holes 28 are arranged in the 4 regions.

[0109] Considering that the self-stabilizing ability of the rock mass in the strong unloading and relaxation zone 29 and the weak unloading and relaxation zone 30 is already relatively poor, there is no need to drill and blast the rock mass in this area. Therefore, the above Scheme 3 and Scheme 4 are not feasible.

[0110] Considering the above Scheme 1 and Scheme 2 comprehensively, it is the best scheme to start arranging the auxiliary holes 28 at the critical position of the intact rock mass region 32. Through the auxiliary holes 28 at the critical position of the intact rock mass region 32, the rock mass in the micro-unloading and relaxation zone 31 can be fully blasted, and the cracks in the weak unloading and relaxation zone 30 can be further expanded, resulting in the complete loss of self-stabilizing ability of the rock mass in the weak unloading and relaxation zone 30 under the blasting construction of the auxiliary holes 28. This scheme can effectively reduce the number of the auxiliary holes 28, achieve the effect of safe construction, improve the blasting forming quality and reduce the explosive consumption.

[0111] Further, a design scheme for the auxiliary holes 28 in the intact rock mass zone 32 is as follows:

[0112]

[0113] Furthermore, after the middle explosion area 20 detonates, it provides a free face for the other four explosion areas, improving the blasting efficiency. At the same time, since the left explosion area 21 and the right explosion area 22 are symmetric about the tunnel center line 8, the blast holes in both explosion areas are symmetric, and two symmetric blast holes can be detonated simultaneously during the detonation process. Since the upper left explosion area 18 and the upper right explosion area 19 are symmetric about the tunnel center line 8, the blast holes in both explosion areas are symmetric, and two symmetric blast holes can be detonated simultaneously during the detonation process.

[0114] The blasting of the auxiliary holes 28 adopts a columnar charge structure, and during the blasting process, it can be regarded as the formation and synthesis of several columnar charge blasting funnels. Under the condition of columnar charge, without considering the action of high in-situ stress, the condition for forming a standard blasting funnel is that the sum of the tangential tensile stress generated by the incident stress wave and the radial tensile stress generated by the reflected stress wave at the edge of the funnel is equal to the tensile strength of the rock, that is

[0115] σ θi +σ rR =σ t (1)

[0116] In the formula: σ θi is the tangential tensile stress generated by the incident stress wave; σ rR is the radial tensile stress generated by the reflected stress wave; σ t is the tensile strength of the rock.

[0117]

[0118]

[0119] p0=ρ e D 2 (V c / V b ) γ n / 8 (4)

[0120]

[0121]

[0122] In the formula: p0 is the explosion load acting on the wall of the auxiliary hole; b is the lateral pressure factor, b = μ / (1 - μ), where μ is the Poisson's ratio of the rock; w0 is the minimum charge resistance line without considering high in-situ stress; r b is the diameter of the auxiliary hole; α is the explosion stress wave attenuation index. If the action of the shock wave is ignored, then α = 2 - b; R is the stress wave reflection factor; ρ e is the density of the explosive; D is the detonation velocity of the explosive; V c is the charge volume; V bis the volume of the blast hole; γ is the adiabatic expansion index of the explosion-generated gas products; n is the pressure increase factor caused by the collision of the explosion-generated gas products with the hole wall, and n = 8 - 10; are the incident angle of the longitudinal stress wave and the reflection angle of the longitudinal wave; θ is the reflection angle of the transverse stress wave. See Figure 13 , rotating the oxyz coordinate system by 45° gives the coordinate system ox1y1z1.

[0123] Furthermore, considering the influence of high in-situ stress, during the blasting of the relief holes, the existence of high in-situ stress changes the stress state of the rock at the edge of the blasting funnel from unidirectional tension to triaxial tension-compression stress state. Considering the brittle failure characteristics of the rock and the specific conditions of the relief hole blasting, using the maximum tensile-compressive stress strength theory, the conditions for forming the relief hole blasting funnel should be modified to:

[0124] [σ x1 +μ(σ y1 +σ z1 )] / E = ε t = σ t / E (7)

[0125]

[0126] In the formula: σ x , σ y are the in-situ stresses in the x and z directions in the oxyz coordinate system; σ x1 , σ y1 , σ z1 are the stress components in the x1, y1, and z1 directions in the ox1y1z1 coordinate system respectively; μ is the Poisson's ratio of the rock; E is the elastic modulus of the rock; ε t is the tensile failure limit strain of the rock.

[0127] Substitute Equation (8) into Equation (7):

[0128] (σ θi +σ rR -σ x cos45°)+μ(σ x cos45°+σ z ) = σ t (9)

[0129] Since there are 2 free surfaces before the relief hole blasting and the depth of the relief hole is not large (relative to the tunnel face size), it can be considered that the in-situ stress component along the axis of the relief hole is 0, that is, σ t = 0, so Equation (9) is rewritten as:

[0130]

[0131] In the formula: δ is the high in-situ stress influence factor, reflecting the influence degree of high in-situ stress on the formation of blasting crater; λ is the ratio of tensile strength of rock under high in-situ stress, reflecting the magnitude of in-situ stress, expressed as σ x = λσ t .

[0132] Formula (10) is the mechanical criterion for forming a standard blasting crater under the condition of considering the influence of high in-situ stress on the auxiliary hole blasting. It can be seen that the effect of high in-situ stress is equivalent to increasing the tensile strength of the rock. Therefore, it will inevitably affect the selection of auxiliary hole blasting parameters.

[0133] Furthermore, under the condition of determining the layout scheme of auxiliary holes above, considering the influence of high in-situ stress comprehensively, optimize the charge amount in the auxiliary holes to achieve the purpose of improving blasting efficiency.

[0134] Furthermore, for the standard blasting crater formed by columnar charge blasting, its volume

[0135] V = w 2 L

[0136] In the formula: L is the length of the blast hole; w is the minimum burden of the auxiliary hole.

[0137] And the charge amount in the blast hole

[0138] Q = π(r b / k de ) 2 Lρ e

[0139] In the formula: k de is the decoupling factor of the blast hole charge.

[0140] Furthermore, the unit consumption of explosives for auxiliary hole blasting

[0141] q = Q / V = π(r b / k de ) 2 ρ e / w 2 (11)

[0142] The unit consumption of explosives for auxiliary hole blasting increases at a relatively large rate with the increase of in-situ stress. However, if explosives with a higher detonation velocity are used to increase the explosion load value acting on the rock in the auxiliary hole wall, the rate of change of the unit consumption of explosives with the increase of in-situ stress can be slowed down, and then the purpose of reducing the amount of explosives used can be achieved. For the formation of a blasting crater, the effect of high in-situ stress is equivalent to increasing the tensile strength of the rock. Therefore, under the condition of high in-situ stress, choosing explosives with a higher detonation velocity conforms to the existing principle of rock blasting by explosion, and the principle of using explosives with a higher detonation velocity for high-strength rocks.

[0143] Reduce the clamping effect of rock by the blasting construction method when passing through each blasting area, and improve the blasting efficiency.

[0144] Step 2: Lofting, arrange the specific positions of the cut holes, auxiliary holes 28 and perimeter holes on the excavation face to lay a foundation for subsequent drilling;

[0145] See Figure 9 , according to the blasting design scheme in Step 1 above and combined with the actual site conditions (rock mass strength coefficient and high ground stress distribution state), taking the rock mass strength coefficient of 10 - 16 as an example, loft the perimeter holes, cut holes and auxiliary holes 28 respectively.

[0146] 2.1 Lofting of perimeter holes

[0147] The lofting of perimeter holes specifically includes:

[0148] See Figure 9 , for each perimeter hole separated at the excavation contour line, the circumferential distance between the perimeter holes 13 at the tunnel arch, the perimeter holes 14 at the tunnel bottom, the perimeter holes 15 in the first stage and the perimeter holes 16 in the second stage is 50 - 70 cm, the distance between adjacent perimeter holes 10 in the vertical direction at the boundary of each blasting area is 60 - 80 cm, and the distance between adjacent perimeter holes 17 in the horizontal direction at the boundary of each blasting area is 40 - 50 cm.

[0149] 2.2 Lofting of cut holes

[0150] According to the cut blasting design scheme in Step 1 above, taking the rock mass strength coefficient of 10 - 16 as an example, loft the cut holes (inner cut holes 24, main cut holes 25, auxiliary cut holes 26) in the medium blasting area 20.

[0151] 2.2 Lofting of auxiliary holes 28

[0152] Taking the rock mass strength coefficient of 10 - 16 as an example, loft the auxiliary holes 28 in the upper left blasting area and the upper right blasting area. See Figure 6 , the connection line of the auxiliary holes in this area is an arc, and its central angle is kept between 30 degrees and 60 degrees, and the distance between adjacent auxiliary holes on the same arc is 60 - 80 cm.

[0153] Taking the rock mass strength coefficient of 10 - 16 as an example, loft the auxiliary holes 28 in the left blasting area and the right blasting area. The hole spacing of the auxiliary holes in this area is 50 - 70 cm, and the row spacing of the auxiliary holes is 100 - 120 cm.

[0154] Set out the positions of the auxiliary holes 28 in the lower bench 23 of the tunnel. The auxiliary holes 28 in this area specifically include the auxiliary holes 28 on the left and right sides of the center line 8 of the lower bench tunnel. The auxiliary holes 28 on the left and right sides of the lower bench 23 of the tunnel are arranged in multiple rows of parallel straight lines. The row spacing of the auxiliary holes in the same area is 100 - 120 cm, and the distance between adjacent auxiliary holes 28 on the same straight line is 50 - 70 cm.

[0155] Step 3: Drilling. Manually hold the pneumatic drill and position and drill the face after setting out according to the drill and blast design; carry out the drilling work on the face to form the perimeter holes, cut holes, and auxiliary holes 28.

[0156] The specific steps of the drilling work for each of the above blast holes include:

[0157] 3.1 Drilling of perimeter holes

[0158] See Figure 3 、 Figure 4 , and carry out the drilling work on the perimeter holes 13 of the tunnel arch near the center line 8 of the tunnel, the perimeter holes 14 at the bottom of the tunnel near the center line 8 of the tunnel, and the perimeter holes of the tunnel side walls on both sides of the center line 8 of the tunnel.

[0159] The perimeter holes of the tunnel side walls in the left blasting area 21 and the right blasting area 22 are the first-stage perimeter holes 15 of the side walls; carry out the drilling work on the perimeter holes of the side walls between the perimeter holes 13 of the tunnel arch that have completed the drilling work on the left side of the excavation contour line and the perimeter holes 15 of the tunnel side walls. Further, the perimeter holes of the tunnel side walls in the lower bench 23 area are the second-stage perimeter holes 16 of the side walls. The second-stage perimeter holes of the side walls throughout the text have the same meaning.

[0160] At the same time, carry out the drilling work on the second-stage perimeter holes 16 of the side walls between the perimeter holes 13 of the tunnel arch that have completed the drilling work on the right side of the excavation contour line and the perimeter holes of the tunnel side walls; carry out the drilling work on the second-stage perimeter holes 16 of the side walls between the perimeter holes 14 of the tunnel bottom that have completed the drilling work on the left side of the excavation contour line and the perimeter holes of the tunnel side walls, and at the same time carry out the drilling work on the second-stage perimeter holes 16 of the side walls between the perimeter holes 14 of the tunnel bottom that have completed the drilling work on the right side of the excavation contour line and the perimeter holes of the tunnel side walls.

[0161] Further, the drilling sequence of the peripheral holes 13 around the tunnel arch is to drill from the tunnel center line 8 along the excavation contour line to both sides; the drilling sequence of the peripheral holes 14 at the tunnel bottom is to drill from the tunnel center line 8 along the excavation contour line to both sides; the drilling sequence of the peripheral holes 15 on the side walls in the first stage is to drill from the centers of the excavation contours outside the left blasting area 21 and the right blasting area 22 along the excavation contour line to both sides; the drilling sequence of the peripheral holes 16 on the left side wall in the second stage of the tunnel is to excavate from the peripheral holes 15 on the side walls in the first stage along the excavation contour line to the peripheral holes 14 at the tunnel bottom, and at the same time, the drilling sequence of the peripheral holes 16 on the right side wall in the second stage of the tunnel is to drill from the peripheral holes 15 on the side walls in the first stage along the excavation contour line to the peripheral holes 14 at the tunnel bottom.

[0162] Further, the diameter of the peripheral holes 13 around the tunnel arch is 50 - 70 mm, the diameter of the peripheral holes 14 at the tunnel bottom is 40 - 50 mm, and the diameter of the peripheral holes on the tunnel side walls (peripheral holes 15 in the first stage and peripheral holes 16 in the second stage) is 55 - 70 mm.

[0163] Drilling work is carried out on the peripheral holes 10 in the vertical direction and the peripheral holes 17 in the horizontal direction at the boundaries of each blasting area. The construction sequence for the peripheral holes at the boundaries of each blasting area is to drill from the tunnel center line 8 to both sides first and then from top to bottom. The diameter of the peripheral holes at the boundaries of each blasting area (peripheral holes 10 in the vertical direction and peripheral holes 17 in the horizontal direction at the boundaries of each blasting area) is 40 - 50 mm.

[0164] See Figure 3 , and drill the cut holes (inner cut holes 24, main cut holes 25, and auxiliary cut holes 26) in the middle blasting area 20 in a serpentine drilling sequence. Specifically, it starts with drilling the inner cut hole 24 from top to bottom and ends with the auxiliary cut hole 26. Among them, the drilling sequence of the last row of the auxiliary cut holes is based on its row number.

[0165] See Figure 3 , and carry out drilling work on the auxiliary holes 28 in the upper left blasting area 18, the upper right blasting area 19, the left blasting area 21, and the right blasting area 22;

[0166] The drilling steps for the auxiliary holes 28 in the upper left blasting area 18 specifically include: drilling the auxiliary hole 28 closest to the tunnel center line 8 and with the largest arc radius in the upper left blasting area 18, and then drilling the remaining auxiliary holes below in sequence along the arc where this auxiliary hole 28 is located. Further, after the drilling work of the last auxiliary hole 28 in the above steps is completed, drill the arc below the arc where the above auxiliary holes are located in reverse order. At the same time, use the same steps to drill the auxiliary holes 28 in the upper right blasting area 19.

[0167] See Figure 3, further, the drilling steps for the auxiliary holes 28 in the left blasting area 21 specifically include: Firstly, drill the first row of auxiliary holes 28 in the left blasting area 21 in the construction sequence from near the tunnel center line 8 to away from the tunnel center line 8; then drill the second row of auxiliary holes 28 in the left blasting area 21 in the construction sequence from away from the tunnel center line 8 to near the tunnel center line 8; repeat the above two steps to complete the drilling work of the auxiliary holes 28 in the left blasting area 21. Meanwhile, drill the auxiliary holes 28 in the right blasting area 22 using the same steps.

[0168] Carry out the drilling work for the auxiliary holes 28 in the lower bench 23. See Figure 3 , further, the drilling steps for the auxiliary holes 28 in the lower bench 23 of the tunnel specifically include: Drill the first row of auxiliary holes 28 on the left side of the tunnel center line 8 in the lower bench 23 of the tunnel in the construction sequence from near the tunnel center line 8 to away from the tunnel center line 8; then drill the second row of auxiliary holes 28 on the left side of the tunnel center line 8 in the lower bench 23 in the construction sequence from away from the tunnel center line 8 to near the tunnel center line 8; repeat the above two steps to complete the drilling work of the auxiliary holes 28 on the left side of the tunnel center line 8 in the lower bench 23 of the tunnel.

[0169] Meanwhile, drill the auxiliary holes 28 on the right side of the tunnel center line 8 in the lower bench 23 of the tunnel using the same steps.

[0170] See Figure 5 , further, except for the above cut holes (inner cut holes 24, main cut holes 25, auxiliary cut holes 26), there is a non-90-degree angle between the cut holes and the excavation face, so the cut holes are wedge-shaped holes, and the remaining perimeter holes and auxiliary holes are straight holes, that is, the inclination angle between their axes and the face is 90 degrees.

[0171] Step 4: Charging, use waterproof emulsion explosive, adopt an uncoupled charging structure for the perimeter holes, and adopt a coupled charging structure for the cut holes and auxiliary holes. Each blast hole is charged according to smooth blasting;

[0172] Charge the perimeter holes (vertical perimeter holes 10, horizontal perimeter holes 17) at the boundary of each blasting area according to presplitting blasting, adopt an uncoupled charging structure, select waterproof emulsion cartridges, ensure that the diameter of the waterproof emulsion cartridges is 10 mm smaller than the diameter of the perimeter holes at the boundary of each blasting area. Thus, the detonation wave generated by the emulsion explosive in the perimeter holes at the boundary of each blasting area during blasting propagates through the air medium to the rock on the inner wall of the perimeter holes at the boundary of each blasting area. The air between the inner wall of the perimeter holes at the boundary of each blasting area and the emulsion explosive is like an air cushion, which can store part of the energy of the gas products at the initial stage of detonation, weaken the initial pressure peak acting on the perimeter holes at the boundary of each blasting area, and the further compressed gas releases a large amount of stored energy, thereby prolonging the action time of the detonation gas and improving the blasting effect, realizing the presplitting blasting of the perimeter holes at the boundary of each blasting area.

[0173] Further, for the peripheral holes 13 around the arch of the tunnel, the peripheral holes on the side walls of the tunnel (the first-stage peripheral holes 15 and the second-stage peripheral holes 16), and the peripheral holes 14 at the bottom of the tunnel, smooth blasting charging is carried out, adopting an uncoupled charging structure. Waterproof emulsion cartridges are selected to ensure that there is a certain interval between the waterproof emulsion cartridges in the peripheral holes 13 around the arch of the tunnel, the peripheral holes on the side walls of the tunnel (the first-stage peripheral holes 15 and the second-stage peripheral holes 16), and the peripheral holes 14 at the bottom of the tunnel. For the auxiliary holes 28 and the cut holes on the left and right sides of the tunnel center line (the inner cut holes 24, the main cut holes 25, and the auxiliary cut holes 26), charging is carried out according to ordinary blasting, adopting a coupled charging structure.

[0174] See Figure 10 , further, during the blasting excavation process, the rock within the single-round advance range is damaged by the blasting in the previous cycle and can be divided into a crushed zone 33, a fractured zone 34, and a surrounding rock zone 35. Among them, the crushed zone 33 is affected by the blasting shock wave, and the rock mass is severely crushed, but its range is small; in the fractured zone 34, under the action of the blasting stress wave, circumferential and radial fractures develop in the rock mass, and then the fractures are further expanded by the "wedge action" of the explosion-generated gas, forming a large-scale fracture-intensive zone; the surrounding rock zone 35 and the original rock zone 36 are regarded as not affected by the blasting excavation and retain the strength of the original rock. Considering the damage range comprehensively, a bottom charging structure is adopted. That is, the emulsion cartridges are preferentially arranged at the bottom of the blast holes 37.

[0175] Step 5: Initiation. The sectional and timed initiation method is used to ensure that the blastholes in each blasting area are not initiated simultaneously, leaving a millisecond time difference, achieving the effect of providing more free faces for the next blasting area after the previous blasting area is initiated, and realizing the functions of vibration reduction and improving blasting efficiency.

[0176] Combined with Figure 11 , Figure 12 , a further detailed description of the initiation of each blasthole in the above step 5 is as follows:

[0177] The millisecond blasting method is adopted for the upper bench and the lower bench. Specifically, it includes: the peripheral holes 13 at the arch crown, the first-stage side wall peripheral holes 15, the second-stage side wall peripheral holes 16, the bottom peripheral holes 14, and the peripheral holes at the boundaries of each blasting area (the vertical peripheral holes 10 and the horizontal peripheral holes 17) are respectively formed into synchronous initiation segments with the same section of detonators, and different sections of detonators are used between different synchronous initiation segments to achieve millisecond blasting between different types of peripheral holes.

[0178] For the inner cut holes (the inner cut holes 24, the main cut holes 25, and the auxiliary cut holes 26) and the auxiliary holes 28 in each blasting area (the upper left blasting area 18, the upper right blasting area 19, the middle blasting area 20, the left blasting area 21, and the right blasting area 22), different sections of detonators are respectively used to form millisecond blasting within the blasting area, and different sections of detonators are used between each blasting area (the upper left blasting area 18, the upper right blasting area 19, the middle blasting area 20, the left blasting area 21, and the right blasting area 22) to form millisecond blasting between each blasting area.

[0179] Further, different-section external area outboard detonators are respectively set for the arch perimeter holes 13, the first-stage sidewall perimeter holes 15, the second-stage sidewall perimeter holes 16 in the upper bench, the perimeter holes at the boundaries of each blasting area (the vertical perimeter holes 10 at the boundaries of each blasting area, the horizontal perimeter holes 17 at the boundaries of each blasting area), the auxiliary holes 28 in the upper left blasting area 18, the auxiliary holes 28 in the upper right blasting area 19, the cut holes (inner cut holes 24, main cut holes 25, auxiliary cut holes 26) in the middle blasting area 20, the auxiliary holes 28 in the left blasting area 21, and the auxiliary holes 28 in the right blasting area 22. The external area outboard detonators of different sections are sequentially connected in series to form the millisecond blasting of the upper bench.

[0180] Combined with Figure 11 The millisecond blasting of the upper bench perimeter holes in the inventive scheme is further described. The perimeter holes at the boundaries of each blasting area include the first perimeter hole 38, the second perimeter hole 39, the third perimeter hole 40, the fourth perimeter hole 41, and the fifth perimeter hole 42. The first perimeter hole 38 is the perimeter hole at the boundary between the left blasting area and the middle blasting area; the second perimeter hole 39 is the perimeter hole at the boundary between the right blasting area and the middle blasting area; the third perimeter hole 40 is the perimeter hole at the boundaries of the upper left blasting area, the upper right blasting area, the left blasting area, the middle blasting area, and the right blasting area; the fourth perimeter hole 41 is the perimeter hole at the boundary between the upper left blasting area and the upper right blasting area; the fifth perimeter hole 42 is the perimeter hole at the boundary between the upper bench blasting area and the lower bench blasting area.

[0181] The out-of-area detonators include the first-area out-of-area detonator 501, the second-area out-of-area detonator 502, the third-area out-of-area detonator 503, the fourth-area out-of-area detonator 504, the fifth-area out-of-area detonator 505, the upper-bench initiating detonator 506, the lower-bench initiating detonator 507, the sixth-area out-of-area detonator 508, the seventh-area out-of-area detonator 509, the eighth-area out-of-area detonator 510, the ninth-area out-of-area detonator 511, the tenth-area out-of-area detonator 512, the eleventh-area out-of-area detonator 513, the out-of-area detonator 514 in the middle explosion area, and the twelfth-area out-of-area detonator 515. The first-area out-of-area detonator 501 is the out-of-area detonator for the perimeter holes in the side wall of the upper bench in the second stage of the tunnel; the second-area out-of-area detonator 502 is the out-of-area detonator for the perimeter holes in the arch of the tunnel; the third-area out-of-area detonator 503 is the out-of-area detonator for the perimeter holes in the side wall in the first stage of the tunnel; the fourth-area out-of-area detonator 504 is the out-of-area detonator for the perimeter holes in the side wall of the lower bench in the second stage of the tunnel; the fifth-area out-of-area detonator 505 is the out-of-area detonator for the perimeter holes at the bottom of the tunnel; the sixth-area out-of-area detonator 508 is the out-of-area detonator for the boundary area between the upper left explosion area and the upper right explosion area; the seventh-area out-of-area detonator 509 is the out-of-area detonator for the left explosion area and the boundary area between the right explosion area and the middle explosion area; the eighth-area out-of-area detonator 510 is the out-of-area detonator for the boundary area between the upper bench and the lower bench; the ninth-area out-of-area detonator 511 is the out-of-area detonator for the boundary area between the upper left explosion area, the upper right explosion area, the left explosion area, the middle explosion area, and the right explosion area; the tenth-area out-of-area detonator 512 is the out-of-area detonator for the upper left explosion area and the upper right explosion area; the eleventh-area out-of-area detonator 513 is the out-of-area detonator for the left explosion area and the right explosion area; the twelfth-area out-of-area detonator 515 is the out-of-area detonator for the explosion areas on both sides of the center line of the stepped tunnel.

[0182] The perimeter holes (vertical perimeter holes 10 and horizontal perimeter holes 17) at the explosion area boundary are connected in parallel with the perimeter holes 40 at the explosion area boundary through the out-of-area detonator 509, and the out-of-area detonator 511 is set; the out-of-area detonator 508 is set for the perimeter holes 41 at the explosion area boundary; the out-of-area detonator 510 is set for the perimeter holes 42 at the explosion area boundary; the out-of-area detonator 502 is set for the perimeter holes 13 in the arch of the tunnel; the out-of-area detonator 501 is set for the perimeter holes 16 in the side wall of the upper bench in the second stage of the tunnel; the out-of-area detonator 503 is set for the perimeter holes 15 in the side wall in the first stage of the tunnel. The above-mentioned out-of-area detonators in each area are set with different detonator segments and are connected in series to connect to the initiating detonator 506.

[0183] Furthermore, in combination with Figure 12A further description is made on the millisecond blasting of the upper bench cut holes (inner cut holes 24, main cut holes 25, auxiliary cut holes 26) and the auxiliary holes 28 in the invention solution. Different detonator segments are respectively set for the cut holes (inner cut holes 24, main cut holes 25, auxiliary cut holes 26) and the auxiliary holes 28 in the middle blasting area 20 to achieve millisecond blasting. The external connecting detonators 514 of the connecting area in the middle blasting area 20; Different detonator segments are respectively set for the auxiliary holes 28 in the upper left blasting area 18 and the upper right blasting area 19, and are connected to the external connecting detonators 512 of the area; Different detonator segments are respectively set for the auxiliary holes 28 in the left blasting area 21 and the right blasting area 22, and are connected to the external connecting detonators 513 of the area. The above-mentioned external connecting detonators of the area are respectively set with different detonator segments and are connected in series to connect the initiating detonator 506.

[0184] External connecting detonators in different segments are respectively set for the bottom perimeter holes 14, the sidewall perimeter holes 16 in the second stage of the lower bench, and the auxiliary holes 28 in the lower bench blasting area 23. The external connecting detonators in different segments are sequentially connected in series to form the millisecond blasting of the lower bench.

[0185] Furthermore, in combination with Figure 11 A further description is made on the millisecond blasting of the perimeter holes in the lower bench of the invention solution. The external connecting detonator 505 is set for the tunnel bottom perimeter hole 14, and the external connecting detonator 504 is set for the sidewall perimeter hole 16 in the second stage of the tunnel lower bench. The above-mentioned external connecting detonators are respectively set with different detonator segments and are connected in series to connect the initiating detonator 507.

[0186] In combination with Figure 12 A further description is made on the millisecond blasting of the auxiliary holes 28 in the lower bench of the invention solution. Different detonator segments are respectively set for the auxiliary holes 28 in the blasting areas on the left and right sides of the center line 8 of the lower bench tunnel, and are connected to the external connecting detonator 515 of the area, and finally connected to the initiating detonator 507. a1, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, a16, a17, a18, a19, a20, a21 are all detonator segments.

[0187] Pre-splitting blasting is carried out on the perimeter holes around the boundaries of the upper left blasting area 18, upper right blasting area 19, middle blasting area 20, left blasting area 21, and right blasting area 22 (the perimeter holes in the vertical direction at the boundaries of each blasting area 10, the perimeter holes in the horizontal direction at the boundaries of each blasting area 17). The above perimeter holes are detonated simultaneously to form cracks penetrating the longitudinal excavation surface of the tunnel, effectively reducing the clamping effect of the rock under large cross-section conditions; smooth blasting is carried out on the perimeter holes 13 in the tunnel arch, the perimeter holes on the tunnel sidewalls (the first-stage perimeter holes 15, the second-stage perimeter holes 16), and the perimeter holes 14 at the tunnel bottom to form a closed ring. This closed ring penetrates the blasting excavation contour line, separating the pre-excavated rock from the surrounding rock, reducing the disturbance to the surrounding rock during the internal rock blasting process, ensuring the integrity of the contour line after blasting, and effectively reducing the clamping effect of the rock under large cross-section conditions.

[0188] The blasting priorities in the millisecond blasting of the above-mentioned auxiliary holes 28 and cut holes (inner cut holes 24, main cut holes 25, auxiliary cut holes 26) are further described as follows:

[0189] Detonate the emulsion explosive in the cut holes (inner cut holes 24, main cut holes 25, auxiliary cut holes 26) on both sides of the tunnel center line 8 in the middle blasting area 20, and complete the shaping of the cut area in cooperation with the angle between the cut holes (inner cut holes 24, main cut holes 25, auxiliary cut holes 26) and the tunnel face, providing more free faces for the rock blasting in the remaining blasting areas and optimizing the blasting effect.

[0190] Detonate the emulsion explosive packages in the upper left blasting area 18 and simultaneously detonate the emulsion explosive packages in the upper right blasting area 19. Since the perimeter holes (vertical perimeter holes 10, horizontal perimeter holes 17) at the boundaries between the upper left blasting area 18 and the upper right blasting area 19 and other blasting areas are detonated first to provide free faces for each blasting area, and the perimeter holes 13 in the tunnel arch and the perimeter holes on the tunnel sidewalls (the first-stage perimeter holes 15, the second-stage perimeter holes 16) have completed blasting, effectively isolating the connection between the rock in the upper left blasting area 18 and the upper right blasting area 19 and the surrounding rock, effectively avoiding the clamping effect of the surrounding rock on the blasting area rock under large cross-section conditions. Therefore, the upper left blasting area 18 and the upper right blasting area 19 can easily complete the blasting according to the design requirements, avoiding insufficient blasting and effectively reducing the disturbance to the surrounding rock.

[0191] The emulsion explosive packages in the left blasting area 21 and the right blasting area 22 are detonated simultaneously. Since the perimeter holes (vertical perimeter holes 10 and horizontal perimeter holes 17) at the boundaries between the left blasting area 21 and the right blasting area 22 and other blasting areas are detonated first to provide a free face for each blasting area, the upper left blasting area 18 and the upper right blasting area 19 above the left blasting area 21 and the right blasting area 22 have completed blasting, and the perimeter holes of the tunnel sidewall (first-stage perimeter holes 15 and second-stage perimeter holes 16) have completed blasting, effectively isolating the connection between the rocks in the left blasting area 21 and the right blasting area 22 and the surrounding rock, effectively avoiding the clamping effect of the surrounding rock on the blasting area rocks under the condition of a large cross-section. Therefore, the left blasting area 21 and the right blasting area 22 can easily complete blasting according to the design requirements, avoiding insufficient blasting and effectively reducing the disturbance to the surrounding rock at the same time.

[0192] After all the slag removal work in the upper bench is completed, the emulsion explosive packages in the auxiliary holes 28 on both sides of the tunnel center line 8 in the lower bench 23 are detonated simultaneously. Since the rocks in the upper bench have all completed blasting, the clamping effect of the surrounding rock on the rocks in this blasting area is effectively avoided. At the same time, the perimeter holes at the bottom of the tunnel 14 and the perimeter holes of the tunnel sidewall (first-stage perimeter holes 15 and second-stage perimeter holes 16) have completed detonation, effectively avoiding the disturbance to the surrounding rock during the detonation of the lower bench 23 and achieving a better smooth blasting effect.

[0193] Step 6: Slag removal and danger removal.

[0194] The solution of the present invention only needs to activate the detonating detonators 506 and 507 to complete the excavation work during the construction process. The operation is simple, and it has greater flexibility in dealing with more high in-situ stress distribution states. The principle of the solution is easy to understand, and the construction safety factor is relatively large. It can consider the influence of high in-situ stress to a greater extent during the design of the blasting plan and effectively reduce the clamping effect of the rocks during the construction process.

Claims

1. A construction method for induced blasting of damaged rock mass in a large-section high in-situ stress tunnel, characterized in that: The steps are as follows: Step 1: Conduct a site exploration, consider the influence of high in-situ stress on the expansion of rock blasting cracks, divide the damaged rock mass in the large-section high in-situ stress tunnel, determine the envelope of single-hole blasting cracks, and then design the layout schemes of cut holes, auxiliary holes (28) and perimeter holes; Step 2: Specifically arrange the positions of the cut holes, auxiliary holes (28) and perimeter holes at the excavation face for lofting; Step 3: Conduct positioning drilling on the face after lofting; Step 4: Charge the face after positioning drilling; Step 5: Use the method of sectional and time-divided initiation to initiate the charged holes; Step 6: Muck out and remove risks; It includes the first face (1), the second face (2) and the third face (3), wherein the second face (2) is the excavation face; in Step 1, the division of the damaged rock mass in the large-section high in-situ stress tunnel is as follows: divide the second face (2) into the upper bench and the lower bench (23) of the face, the upper bench of the face is divided into the upper layer and the lower layer according to the ratio of 2:3 of the length of the tunnel center line (8), the upper layer is divided into the upper left blasting area (18) and the upper right blasting area (19), and the upper left blasting area (18) and the upper right blasting area (19) are symmetrically structured with respect to the tunnel center line (8), the lower layer is divided into the middle blasting area (20), the left blasting area (21), the right blasting area (22), the left blasting area (21) and the right blasting area (22) are respectively located on the left and right sides of the middle blasting area (20), the middle blasting area (20) is symmetrically structured with respect to the tunnel center line (8), and the left blasting area (21) and the right blasting area (22) are symmetrically structured with respect to the tunnel center line (8); The holes opened on the peripheries of the upper left blasting area (18), the upper right blasting area (19), the middle blasting area (20), the left blasting area (21), the right blasting area (22) and the lower bench (23) are perimeter holes, and the perimeter holes include the tunnel arch perimeter holes (13) opened on the peripheries of the upper left blasting area (18) and the upper right blasting area (19), the tunnel bottom perimeter holes (14) opened at the bottom of the lower bench (23), the second-stage sidewall perimeter holes (16) opened on both sides of the lower bench (23), the first-stage sidewall perimeter holes (15) opened outside the left blasting area (21) and the right blasting area (22), the horizontal perimeter holes (17) opened in the horizontal direction above and below the middle blasting area (20), the left blasting area (21) and the right blasting area (22), and the vertical perimeter holes (10) opened in the vertical direction between the middle blasting area (20) and the left blasting area (21), and between the middle blasting area (20) and the right blasting area (22); The holes set in the areas of the upper left blasting area (18), the upper right blasting area (19), the left blasting area (21), the right blasting area (22) and the lower bench (23) are auxiliary holes (28); The holes set in the middle blasting area (20) are cut holes, and the cut holes specifically include a row of inner cut holes (24), a row of main cut holes (25) and a row of auxiliary cut holes (26), which are arranged in sequence from the tunnel center line (8) to both sides as the inner cut holes (24), the main cut holes (25) and the auxiliary cut holes (26).

2. The construction method of induced blasting for damaged rock mass zoning in a large-section high in-situ stress tunnel according to claim 1, characterized in that: In Step 1: The method for determining the envelope of single-hole blasting cracks: A test hole (4) is set at the second heading face (2) and blasted. Combining with the crack envelope line (6) after blasting under the condition of no in-situ stress, the influence of high in-situ stress on the crack envelope line of a single blast hole is analyzed. When σ v > σ h , the crack length in the vertical direction increases and the crack length in the horizontal direction decreases. The crack envelope line after blasting is elliptical, with the major axis along the vertical direction and the minor axis along the horizontal direction. This is the first single-hole blast crack envelope line (5) under this high in-situ stress state; When σ h > σ v At this time, combined with the crack envelope line (6) after blasting under the condition of no in-situ stress, the crack length in the horizontal direction increases and the crack length in the vertical direction decreases. The crack envelope line after blasting is elliptical, with the major axis along the horizontal direction and the minor axis along the vertical direction. This is the second single-hole blasting crack envelope line (7) under the high in-situ stress state.

3. A construction method for induced blasting of damaged rock mass in a large-section high in-situ stress tunnel according to claim 1, characterized in that: The specific layout plan of the perimeter holes is as follows: ; The cut holes include inner cut holes (24), main cut holes (25) and auxiliary cut holes (26), The design parameters of the inner cut holes (24) specifically include: the depth L1 of the inner cut holes (24), the bottom spacing c1 of the paired inner cut holes (24), the angle α1 between the inner cut holes (24) and the tunnel face, the hole spacing a1 of the inner cut holes (24), the length L1 / cosα1 of the inner cut holes (24), and the opening distance b1 of the inner cut holes (24); ; The depth L1 of the inner cut holes (24) = (L2 + L3) × 2 / 3, where L2 is the depth of the auxiliary cut holes (26) and L3 is the overbreak depth of the main cut holes (25); The opening distance b1 of the inner cut holes (24) = (L1 / tanα1) × 2 + c1; The design parameters of the main cut holes (25) specifically include the bottom distance c2 of the main cut holes (25), the angle α2 between the main cut holes (25) and the tunnel face, the overbreak depth L3 of the main cut holes (25), the hole spacing a2 of the main cut holes (25), the length (L2 + L3) / cosα2 of the main cut holes (25), and the opening distance (b1 + 2b2) of the main cut holes (25); ; The design parameters of the auxiliary cut holes (26) specifically include the hole spacing a3 of the auxiliary cut holes (26), the row spacing b2 between the inner cut holes (24) and the main cut holes (25), the row spacing b3 between the auxiliary cut holes (26) on the tunnel face and the front row of holes, the angle α3 between the auxiliary cut holes (26) and the tunnel face (27), and the length L2 / cosα3 of the auxiliary cut holes (26); Where: b2 = [2×(L2 + L3) / tanα2 + c2 - b1] / 2; α3 = arctan[L2 / (b3 + L2 / tanα2 - d)]; ; The layout plan of the auxiliary holes (28) is as follows: 。 4. A construction method for induced blasting of damaged rock mass in a large-section high in-situ stress tunnel according to claim 1, characterized in that: The blasting of the auxiliary holes (28) adopts a columnar charge structure to form a standard blasting crater; The conditions for forming a standard blasting crater are: ; Wherein: δ is the high ground stress influence factor, reflecting the influence degree of high ground stress on the formation of blasting funnel; λ is the ratio of tensile strength of rock under high ground stress, reflecting the magnitude of ground stress, expressed as σ x = λσ t ; The volume of the standard blasting crater is: V = w 2 L In the formula: L is the length of the blast hole; w is the minimum burden of the relief hole; The charge amount of the blast holes in the standard blasting crater is: ; Where: k de is the decoupling factor of the blast hole charge; The unit consumption of explosives for the blasting of the auxiliary holes in the standard blasting crater is: ; In the formula: r b is the diameter of the auxiliary hole; ρ e is the density of the explosive.

5. A construction method for induced blasting of damaged rock mass in a large-section high in-situ stress tunnel according to claim 1, characterized in that: In step 3, the drilling sequence of the perimeter holes is as follows: The drilling sequence of the perimeter holes (13) in the tunnel arch is to drill from the tunnel center line (8) along the excavation contour line to both sides; The drilling sequence of the perimeter holes (14) at the bottom of the tunnel is to drill from the tunnel center line (8) along the excavation contour line to both sides; The drilling sequence of the perimeter holes (15) on the side walls in the first stage is to drill from the center of the excavation contour line outside the left blasting area (21) and the right blasting area (22) along the excavation contour line to both sides; The drilling sequence of the perimeter holes (16) on the side walls in the second stage is to drill from the perimeter holes (15) on the side walls in the first stage along the excavation contour line towards the perimeter holes (14) at the bottom of the tunnel; The drilling sequence of the vertical perimeter holes (10) and the horizontal perimeter holes (17) follows the construction sequence of first from the tunnel center line (8) to both sides and then from top to bottom; Drilling sequence of the cut holes: A serpentine drilling sequence starting from the inner cut holes (24) drilled from top to bottom and ending with the auxiliary cut holes (26); Drilling sequence of the auxiliary holes (28) in the upper left blasting area (18) and upper right blasting area (19): Drill the auxiliary hole (28) closest to the tunnel center line (8) and with the largest arc radius. Then, drill the remaining auxiliary holes (28) in sequence along the arc where this auxiliary hole (28) is located. Next, drill the lower arcs of this arc in reverse order, and alternate the drilling sequence for adjacent arcs; Drilling sequence of the auxiliary holes (28) in the left blasting area (21) and right blasting area (22): In the left blasting area (21), first drill the first row of auxiliary holes (28) in the construction sequence from close to the tunnel center line (8) to away from the tunnel center line (8); then drill the second row of auxiliary holes (28) in the left blasting area (21) in the construction sequence from away from the tunnel center line (8) to close to the tunnel center line (8). Repeat the above two steps to complete the drilling of the auxiliary holes (28) in the left blasting area (21). At the same time, use the same steps to drill the auxiliary holes (28) in the right blasting area (22); Drilling sequence of the auxiliary holes (28) in the lower bench (23): The drilling steps for the auxiliary holes (28) in the lower bench (23) of the tunnel specifically include: Drill the first row of auxiliary holes (28) on the left side of the tunnel center line (8) in the lower bench (23) in the construction sequence from close to the tunnel center line (8) to away from the tunnel center line (8); then drill the second row of auxiliary holes (28) on the left side of the tunnel center line (8) in the lower bench (23) in the construction sequence from away from the tunnel center line (8) to close to the tunnel center line (8). Repeat the above two steps to complete the drilling of the auxiliary holes (28) on the left side of the tunnel center line (8) in the lower bench (23). At the same time, use the same steps to drill the auxiliary holes (28) on the right side of the tunnel center line (8) in the lower bench (23).

6. A construction method for induced blasting of damaged rock mass in a large-section high in-situ stress tunnel according to claim 1, characterized in that: In step 4, an uncoupled charge structure is adopted for the perimeter holes, and a coupled charge structure is adopted for the auxiliary holes (28) and the cut holes. Waterproof emulsion explosive cartridges are selected for the perimeter holes, auxiliary holes (28), and cut holes.

7. A construction method for induced blasting of damaged rock mass in a large-section high in-situ stress tunnel according to claim 1, characterized in that: In step 5, millisecond blasting method is adopted for initiation.

8. A construction method for induced blasting of damaged rock mass in a large-section high in-situ stress tunnel according to claim 1, characterized in that: The steps of the sectional and timed initiation method in step 5 are as follows: First step, conduct pre-splitting blasting on the vertical perimeter holes (10) and horizontal perimeter holes (17) simultaneously to form a crack running through the longitudinal excavation surface of the tunnel; conduct smooth blasting on the arch perimeter holes (13), first-stage sidewall perimeter holes (15), second-stage sidewall perimeter holes (16), and bottom perimeter holes (14) of the tunnel to form a closed ring that runs through the blasting excavation contour line, separating the pre-excavated rock from the surrounding rock and ensuring the integrity of the contour line after blasting; Second step, initiate the emulsion explosive in the cut holes and complete the formation of the cut area in cooperation with the angle between the cut holes and the tunnel face; Third step, simultaneously initiate the emulsion explosive cartridges in the upper left blasting area (18) and upper right blasting area (19); Fourth step, simultaneously initiate the emulsion explosive cartridges in the left blasting area (21) and right blasting area (22); In the fifth step, after all the mucking work in the blast areas on the upper bench is completed, the emulsion cartridges in the auxiliary holes (28) on both the left and right sides of the tunnel center line (8) of the lower bench (23) are detonated simultaneously.

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