A blasting control structure for overbreak of a tunnel in surrounding rock conditions
By arranging multiple types of blasting holes in different sections on the tunnel cross-section and using high-precision electronic detonators, the problem of controlling blasting disturbance during tunnel construction under weak surrounding rock conditions was solved, achieving precise layered stripping of the surrounding rock and improving construction safety.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- NORTHEASTERN UNIV CHINA
- Filing Date
- 2025-09-11
- Publication Date
- 2026-07-10
AI Technical Summary
When constructing tunnels in weak surrounding rock conditions, traditional blasting methods are difficult to control blasting disturbances, resulting in low construction safety, difficulty in controlling over-excavation and under-excavation, and the existing technology is not ideal under complex rock conditions.
By employing zoned layout of blasting holes and using electronic detonators for high-precision delay control, and by setting multiple types of blasting holes and different zones with different detonation delay patterns on the tunnel cross-section, combined with the high-precision delay control of electronic detonators, refined management of blasting sequence, charge quantity, and inter-hole delay is achieved.
It achieves precise layered stripping of the surrounding rock, reduces blasting disturbance and damage to the surrounding rock, and significantly improves the control effect of over-excavation and under-excavation and construction safety.
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Figure CN224480098U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of blasting construction technology, and more specifically, to a blasting control structure for over- and under-excavation of tunnels in fractured surrounding rock conditions. Background Technology
[0002] Currently, in tunnel construction under weak surrounding rock conditions, traditional blasting methods generally employ conventional borehole layouts and ordinary detonators. However, in complex surrounding rock conditions, the effectiveness of smooth blasting is often difficult to guarantee. Blasting disturbances can easily trigger or accelerate local collapses, rockfalls, and rock instability. This not only affects construction safety but also significantly increases the cost of subsequent reinforcement. While existing technologies attempt to reduce disturbances by optimizing borehole layouts and reducing charge quantities, the original layout methods struggle to control disturbances and greatly increase the difficulty of controlling over- and under-excavation, with unsatisfactory results in complex rock conditions. Furthermore, traditional detonation methods suffer from low delay accuracy and large detonation errors, leading to uneven blasting energy distribution and significant blasting disturbances. Therefore, existing technologies have shortcomings in addressing tunnel over- and under-excavation control, including insufficient construction accuracy, poor disturbance control, and low construction safety. Utility Model Content
[0003] The purpose of this invention is to provide a blasting control structure for over- and under-excavation in tunnels with fractured surrounding rock conditions, thereby improving the aforementioned problems. To achieve this purpose, the technical solution adopted by this invention is as follows:
[0004] This application provides a blasting control structure for over- and under-excavation of tunnels in fractured surrounding rock conditions, comprising: tunnel rock strata, first blasting detonators, second blasting detonators, and a blasting controller. The tunnel rock strata include a first tunnel section and a second tunnel section, the area of the first tunnel section being larger than that of the second tunnel section. Multiple first tunnel blasting holes are provided on the first tunnel section. The second tunnel section is adjacent to the first tunnel section and has multiple second tunnel blasting holes. The first tunnel blasting holes on the first tunnel section are arranged in at least one column, with the connecting lines between each column of first tunnel blasting holes being straight lines or arcs. The second tunnel section also has at least one column of second tunnel blasting holes, with the connecting lines between each column of second tunnel blasting holes being arcs. The first blasting detonators are correspondingly installed in the first tunnel blasting holes. The second blasting detonators are correspondingly installed in the second tunnel blasting holes. The blasting controller is electrically connected to all the first and second blasting detonators, and is used to control the detonation of the first and second blasting detonators.
[0005] Preferably, the second tunnel blasting hole includes a first blasting hole, a second blasting hole, and a third blasting hole. The first blasting hole is located on the side of the tunnel rock stratum away from the tunnel sidewall, and the third blasting hole is located on the side of the tunnel sidewall. The second blasting hole is located between the first blasting hole and the third blasting hole. There are at least two of each of the first, second, and third blasting holes. The detonation time interval between any two adjacent first blasting holes is set to 3 ms, the detonation time interval between any two adjacent second blasting holes is set to 3 ms, and the detonation time interval between any two adjacent third blasting holes is set to 2 ms.
[0006] Preferably, the detonation time range of the second detonator in the first blasting hole is 0ms-21ms, the detonation time range of the second detonator in the second blasting hole is 24ms-35ms, and the detonation time range of the second detonator in the third blasting hole is 37ms-59ms. The single-hole charge coefficient of the first and second blasting holes is 0.4, and the single-hole charge coefficient of the third blasting hole is 0.3.
[0007] Preferably, the ratio of the number of blasting holes in the first, second, and third blasting holes is 8:5:12, and the depth of each hole in the first, second, and third blasting holes is 1.5m, and the diameter is 42mm.
[0008] Preferably, the second tunnel blasting hole includes a fourth blasting hole and a fifth blasting hole, and at least two of each of the fourth and fifth blasting holes are provided. The detonation time interval between any two adjacent fourth blasting holes is set to 3 ms, and the detonation time interval between any two adjacent fifth blasting holes is set to 2 ms. The single-hole charge coefficient of the fourth blasting hole is 0.4, and the single-hole charge coefficient of the fifth blasting hole is 0.3.
[0009] Preferably, the ratio of the number of blasting holes in the fourth blasting hole to the number of blasting holes in the fifth blasting hole is 8:9, and the depth of each hole in the fourth blasting hole and the fifth blasting hole is 1.5m and the diameter is 42mm.
[0010] Preferably, the second tunnel blasting hole includes a sixth blasting hole, and at least two sixth blasting holes are provided. The detonation time interval between any two adjacent sixth blasting holes is set to 2ms, and the single-hole charge coefficient of each sixth blasting hole is 0.3.
[0011] Preferably, the second tunnel section is provided with at least 3 holes, and the distance between any two adjacent holes is 30cm.
[0012] The beneficial effects of this utility model are as follows:
[0013] This invention achieves refined control over blasting sequence, charge quantity, and inter-hole delay by dividing the tunnel cross-section into zones and designing multiple types of blasting holes and corresponding detonation delay rules in different zones, combined with the high-precision delay control advantages of electronic detonators. By arranging the blasting holes in different zones in straight lines or arcs and adopting a top-down and inside-out detonation method, precise layered stripping of the surrounding rock can be achieved, effectively reducing blasting disturbance and surrounding rock damage, and significantly improving the control effect of over-excavation and under-excavation. Simultaneously, the introduction of void design and differentiated charge coefficients in typical cross-sections further improves the stability of the surrounding rock and construction safety. Specifically, this invention rationally selects the stripping layer thickness and blasting parameters of the second tunnel zone based on the thickness of the sidewall surrounding rock, thereby achieving layered stripping of the sidewall surrounding rock by setting different numbers of blasting holes.
[0014] Other features and advantages of this invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing embodiments of the invention. The objects and other advantages of this invention can be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings. Attached Figure Description
[0015] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0016] Figure 1 This is a schematic diagram of a blasting control structure for over- and under-excavation of tunnels in fractured surrounding rock conditions, as described in an embodiment of this utility model.
[0017] Figure 2 This is a schematic diagram showing the arrangement of the first blasting hole, the second blasting hole, and the third blasting hole in a blasting control structure for over- or under-excavation of a tunnel under fractured surrounding rock conditions, as described in an embodiment of this utility model.
[0018] Figure 3 This is a schematic diagram showing the arrangement of the fourth and fifth blasting holes in a blasting control structure for over- or under-excavation of tunnels in fractured surrounding rock conditions, as described in an embodiment of this utility model.
[0019] Figure 4 This is a schematic diagram showing the arrangement of the sixth blasting hole in a blasting control structure for over- or under-excavation of tunnels in fractured surrounding rock conditions, as described in an embodiment of this utility model.
[0020] The markings in the diagram are: 1. First tunnel section; 2. Second tunnel section; 3. First blasting hole; 4. Second blasting hole; 5. Third blasting hole; 6. Fourth blasting hole; 7. Fifth blasting hole; 8. Sixth blasting hole; 9. Hole; 10. Blasting controller. Detailed Implementation
[0021] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. The components of the embodiments of this utility model described and shown in the accompanying drawings can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this utility model provided in the accompanying drawings is not intended to limit the scope of the claimed utility model, but merely to illustrate selected embodiments of the utility model. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without inventive effort are within the scope of protection of this utility model.
[0022] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this utility model, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.
[0023] Example 1
[0024] like Figure 1 , Figure 2 , Figure 3 and Figure 4As shown, this embodiment provides a blasting control structure for over- and under-excavation of tunnels in fractured surrounding rock conditions, including: tunnel rock strata, a first blasting detonator, a second blasting detonator, and a blasting controller 10. The tunnel rock strata include a first tunnel section 1 and a second tunnel section 2. The area of the first tunnel section 1 is larger than that of the second tunnel section 2. Multiple first tunnel blasting holes are provided on the first tunnel section 1. The second tunnel section 2 is adjacent to the first tunnel section 1 and is provided with multiple second tunnel blasting holes. The first tunnel section 1... The blasting holes are arranged in at least one row, and the lines connecting the first tunnel blasting holes in each row are straight lines or arcs. The second tunnel blasting holes in the second tunnel section 2 are arranged in at least one row, and the lines connecting the second tunnel blasting holes in each row are arcs. The first blasting detonators are installed one-to-one in the first tunnel blasting holes. The second blasting detonators are installed one-to-one in the second tunnel blasting holes. The blasting controller 10 is electrically connected to all the first blasting detonators and the second blasting detonators respectively. The blasting controller 10 is used to control the detonation of the first blasting detonators and the second blasting detonators.
[0025] Understandably, this step first divides the tunnel excavation section into a main rock-breaking zone (first tunnel section 1) and a disturbance control buffer zone (second tunnel section 2) according to function and stress differences. Using electronic detonators in groups and a unified controller with precise timing as a carrier, it realizes the zonal release of energy and the controllable guidance of fractures: the main rock-breaking zone has a larger area and undertakes the main excavation task. Its hole array can be arranged in a straight line or a large-radius arc to form a regular free surface and a stable cut, ensuring the efficiency of advancement and block size control; the adjacent buffer zone adopts an arc hole array to fit the geometry of the sidewall and surrounding rock. The arc connection helps to make the blasting stress wave "turn" along the curve and attenuate at the arch shoulder and sidewall, suppressing radial over-blasting and shearing block, which is equivalent to setting a "stress damping zone" between the main rock-breaking zone and the forming boundary. Two types of blasting holes are each equipped with electronic detonators in different groups. All detonators are triggered by the same blasting controller 10 in a predetermined sequence, so that the main rock breaking zone first forms a stable free surface and unloading space. Then, the buffer zone completes contour modification and damage control at a milder energy level, improving the contour forming quality and reducing the amount of over-excavation and under-excavation repair. The second tunnel zone is the zone close to the adjacent tunnel, and the first tunnel zone is the zone far away from the adjacent tunnel.
[0026] Furthermore, the blasting hole arrangement in the first tunnel section 1 is the existing arrangement, as follows: Figure 1 As shown, it will not be described here. The detonators in this utility model are all electronic detonators. Their advantages are that the delay can be accurate to 1ms, the error is 0.1 to 0.5ms within 100ms, and the error is 0.1 to 0.5ms when it is greater than 100ms. Moreover, the detonation time can be set arbitrarily according to the needs of the site.
[0027] The second tunnel blasting hole includes a first blasting hole 3, a second blasting hole 4, and a third blasting hole 5. The first blasting hole 3 is located on the side away from the tunnel rock strata and the tunnel sidewall. The third blasting hole 5 is located on the side closer to the tunnel sidewall. The second blasting hole 4 is located between the first blasting hole 3 and the third blasting hole 5. There are at least two of each of the first blasting hole 3, the second blasting hole 4, and the third blasting hole 5. The detonation time interval between any two adjacent first blasting holes 3 is set to 3ms, the detonation time interval between any two adjacent second blasting holes 4 is set to 3ms, and the detonation time interval between any two adjacent third blasting holes 5 is set to 2ms.
[0028] Understandably, this step further refines the setting of the first, second, and third types of blasting holes in the second tunnel section 2. Essentially, it utilizes the spatial distribution of the hole positions and the slight difference in the detonation delay to control the energy release sequence in layers and zones: the first blasting hole 3 is arranged on the side away from the tunnel sidewall, which is equivalent to a "pilot hole". Its function is to preferentially break the inner rock mass, release the initial energy, and form a free surface for subsequent blasting; the second blasting hole 4 is located in the middle position and acts as a "transition hole". It receives the unloading fracture generated by the first blasting hole 3, expands the breaking range, and transfers energy to the edge; the third blasting hole 5 is close to the sidewall and undertakes the final finishing and shaping task. Since it is near the design outline, it must operate in a relatively low disturbance environment. Therefore, a shorter 2ms delay is used to form a continuous but gentle energy transfer chain to avoid impact concentration that causes sidewall rockfall. This gradual delay from the inside out (3ms-3ms-2ms) not only creates a gradient in energy distribution from strong to weak, but also allows for layer-by-layer peeling to approximate the design profile, achieving a balance between reducing rock mass damage and blasting effectiveness.
[0029] Specifically, the detonation time range of the second detonator in the first blasting hole 3 is 0ms-21ms, the detonation time range of the second detonator in the second blasting hole 4 is 24ms-35ms, and the detonation time range of the second detonator in the third blasting hole 5 is 37ms-59ms. The single-hole charge coefficient of the first blasting hole 3 and the second blasting hole 4 is 0.4, and the single-hole charge coefficient of the third blasting hole 5 is 0.3.
[0030] It is understandable that this step optimizes the initiation time design of the three types of holes in the second tunnel section 2 by coordinating the optimization: the second blasting detonator is set with a 0–21ms window (3ms arithmetic progression) in the first hole row, a 24–35ms window (maintaining a 3ms arithmetic progression with the first row) in the second hole row, and a 37–59ms window (2ms arithmetic progression, corresponding to 12 holes) in the third hole row. In addition, the charge intensity decreases from the inside to the outside (charge coefficient of 0.4 for the first and second hole rows, and 0.3 for the third hole row). The first row forms a stable free surface and unloading zone, suppressing the direct impact of the subsequent wavefront on the sidewall; the second row expands the fracture with the help of the existing free surface but does not excessively approach the contour; the third row increases the probability of the destructive superposition of stress peaks with a short delay of 2ms, limits the penetration depth of microcracks, and makes the contour formation more in line with the design line. Meanwhile, the coupling of the charge gradient and the order of charge is equivalent to arranging an "energy buffer layer" in space, reducing the disturbance intensity of peak vibration velocity and explosive stress on weak surrounding rock, and avoiding spalling and rockfall; wherein, the blasting method of the first blasting hole 3, the second blasting hole 4 and the third blasting hole 5 is set to the initiation method from top to bottom and from inside to outside.
[0031] The ratio of the number of blasting holes in the first blasting hole 3, the second blasting hole 4, and the third blasting hole 5 is 8:5:12. The depth of each hole in the first blasting hole 3, the second blasting hole 4, and the third blasting hole 5 is 1.5m, and the diameter is 42mm.
[0032] It is understandable that this step involves configuring the number of three types of holes in the second tunnel section 2 in a ratio of 8:5:12, and unifying the hole depth to 1.5m and the hole diameter to 42mm. The 8 inner zone holes provide the main rock breaking and slotting free surface, the 5 middle zone holes are used to receive and expand the unloading fractures, and the 12 outer zone holes complete the contour line and damage control with denser coverage, thereby achieving precise layered stripping of the surrounding rock.
[0033] The second tunnel blasting hole includes a fourth blasting hole 6 and a fifth blasting hole 7. At least two of each of the fourth blasting holes 6 and the fifth blasting hole 7 are provided. The detonation time interval between any two adjacent fourth blasting holes 6 is set to 3 ms, and the detonation time interval between any two adjacent fifth blasting holes 7 is set to 2 ms. The single-hole charge coefficient of the fourth blasting hole 6 is 0.4, and the single-hole charge coefficient of the fifth blasting hole 7 is 0.3.
[0034] It is understandable that the second tunnel section 2 in this step adopts a combination of the fourth and fifth types of blasting holes. The essence of this is to form a two-level effect of "main breaking - flexible control" by adjusting the charge intensity and delay pattern: the fourth blasting hole 6 is arranged with a charge coefficient of 0.4 and an inter-hole delay of 3ms, so that it has a high energy release capability and is mainly responsible for further breaking the inner rock mass and forming a secondary free surface, creating conditions for subsequent fine shaping; while the fifth blasting hole 7 is arranged on the side closer to the outline with a charge coefficient of 0.3 and a shorter delay of 2ms, which is equivalent to a "shaping hole". It is detonated at a lower energy and a higher timing resolution, which can reduce stress concentration and make the fracture propagation more controlled and closer to the design outline. Both types of holes follow the order of "from top to bottom and from inside to outside" to ensure that the blasting energy is consumed internally first and then gradually transmitted to the periphery, avoiding the falling of blocks due to premature breakage of the upper or side parts. The blasting method of the fourth blasting hole 6 and the fifth blasting hole 7 is set to be a top-down and inside-out initiation method.
[0035] The ratio of the number of blasting holes in the fourth blasting hole 6 and the fifth blasting hole 7 is 8:9. The depth of each hole in the fourth blasting hole 6 and the fifth blasting hole 7 is 1.5m and the diameter is 42mm.
[0036] It is understandable that this step configures the number of fourth and fifth blasting holes 7 in an 8:9 ratio, and unifies the hole depth to 1.5m and the hole diameter to 42mm. The purpose is to establish a slightly outward-sloping hole density gradient between the "inner" and "outer" zones to ensure that the contour follows the line and the damage is controllable. This makes the cracks present shorter, more numerous, and more directional micro-crack groups when they approach the design line, thus avoiding long crack penetration and over-excavation.
[0037] The second tunnel blasting hole includes a sixth blasting hole 8, and at least two sixth blasting holes 8 are provided. The detonation time interval between any two adjacent sixth blasting holes 8 is set to 2ms, and the single-hole charge coefficient of each sixth blasting hole 8 is 0.3.
[0038] It is understandable that the sixth blasting hole 8 in this step, as a "single-zone flexible control" scheme for the second tunnel section 2 under specific surrounding rock and cross-sectional morphology, is intended to perform directional modification of the contour or sensitive area with lower energy levels and higher temporal resolution: a uniform single-hole charge coefficient of 0.3 is adopted to keep the blast stress and gas pressure in the hole near the threshold of "sufficient to extend existing micro-fractures without penetrating beyond the boundary"; the short delay of 2ms between adjacent holes allows the stress wave and the fracture front to advance hole by hole in a "relay" manner, which avoids the peak velocity amplification caused by in-phase superposition and maintains continuous free surface expansion, suitable for edge finishing of sidewalls / shoulders in areas with foliation, soft inclusions, or existing disturbances. The setting of at least two holes ensures sufficient geometric continuity in the length direction, allowing the fracture zone to advance along the design line and reducing local tooth-like over-excavation caused by single-hole action. The blasting method of the sixth blasting hole 8 is set to a top-down initiation method.
[0039] It is understood that the present invention achieves the purpose of precise layered peeling of sidewall surrounding rock of different thicknesses by rationally selecting the number of rows and blasting parameters of blasting holes in the second tunnel section according to the thickness of the sidewall surrounding rock, and then by setting different numbers of rows and blasting parameters of blasting holes.
[0040] The second tunnel section 2 is provided with at least 3 holes 9, and the distance between any two adjacent holes 9 is 30cm.
[0041] It is understood that this step introduces at least three holes 9 in the second tunnel section 2, and arranges adjacent holes 9 at multiples of each other. The holes 9 themselves provide significant medium discontinuity, and the incident blast stress wave is reflected and refracted at the hole wall. The peak tensile stress is weakened and a low disturbance zone is formed behind the hole 9, thereby playing a "vibration isolation buffer" role for weak interlayers or sensitive areas of sidewalls. The arrangement of at least two holes forms a continuous "flexible barrier". The holes are set in the closest area between two adjacent tunnels, with a range of 60cm above and below the closest point. This prevents the vibration or energy disturbance caused by the blast from affecting adjacent tunnels and prevents the occurrence of blasting through the walls of adjacent tunnels.
[0042] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this utility model is in use. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.
[0043] In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of these terms in this utility model based on the specific circumstances.
[0044] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.
[0045] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope of the claims.
Claims
1. A blasting control structure for over- and under-excavation in tunnels with fractured surrounding rock, characterized in that: The tunnel rock strata include a first tunnel section (1) and a second tunnel section (2). The area of the first tunnel section (1) is larger than that of the second tunnel section (2). The first tunnel section (1) is provided with a plurality of first tunnel blasting holes. The second tunnel section (2) is arranged adjacent to the first tunnel section (1). The second tunnel section (2) is provided with a plurality of second tunnel blasting holes. The first tunnel blasting holes on the first tunnel section (1) are arranged in at least one column. The connecting line between each column of first tunnel blasting holes is a straight line or an arc. The second tunnel section (2) is provided with at least one column of second tunnel blasting holes. The connecting line between each column of second tunnel blasting holes is an arc. The first explosive detonator is installed one-to-one in the first tunnel blast hole; The second blasting detonator is installed one-to-one in the blasting hole of the second tunnel; A blasting controller (10) is electrically connected to all the first blasting detonators and the second blasting detonators respectively. The blasting controller (10) is used to control the detonation of the first blasting detonators and the second blasting detonators.
2. The blasting control structure for over- and under-excavation of tunnels in fractured surrounding rock conditions according to claim 1, characterized in that: The second tunnel blasting hole includes a first blasting hole (3), a second blasting hole (4), and a third blasting hole (5). The first blasting hole (3) is located on the side away from the tunnel rock stratum and the tunnel sidewall. The third blasting hole (5) is located on the side close to the tunnel sidewall. The second blasting hole (4) is located between the first blasting hole (3) and the third blasting hole (5). There are at least two of each of the first blasting hole (3), the second blasting hole (4), and the third blasting hole (5). The detonation time interval between any two adjacent first blasting holes (3) is set to 3ms. The detonation time interval between any two adjacent second blasting holes (4) is set to 3ms. The detonation time interval between any two adjacent third blasting holes (5) is set to 2ms.
3. The blasting control structure for over- and under-excavation of tunnels in fractured surrounding rock conditions according to claim 2, characterized in that: The detonation time range of the second detonator in the first blasting hole (3) is 0ms-21ms, the detonation time range of the second detonator in the second blasting hole (4) is 24ms-35ms, and the detonation time range of the second detonator in the third blasting hole (5) is 37ms-59ms. The single-hole charge coefficient of the first blasting hole (3) and the second blasting hole (4) is 0.4, and the single-hole charge coefficient of the third blasting hole (5) is 0.
3.
4. The blasting control structure for over- and under-excavation of tunnels in fractured surrounding rock conditions according to claim 3, characterized in that: The ratio of the number of blasting holes in the first blasting hole (3), the second blasting hole (4), and the third blasting hole (5) is 8:5:
12. The depth of each hole in the first blasting hole (3), the second blasting hole (4), and the third blasting hole (5) is 1.5m, and the diameter is 42mm.
5. The blasting control structure for over- and under-excavation of tunnels in fractured surrounding rock conditions according to claim 1, characterized in that: The second tunnel blasting hole includes a fourth blasting hole (6) and a fifth blasting hole (7). There are at least two of each of the fourth blasting holes (6) and the fifth blasting hole (7). The detonation time interval between any two adjacent fourth blasting holes (6) is set to 3ms, and the detonation time interval between any two adjacent fifth blasting holes (7) is set to 2ms. The single-hole charge coefficient of the fourth blasting hole (6) is 0.4, and the single-hole charge coefficient of the fifth blasting hole (7) is 0.
3.
6. The blasting control structure for over- and under-excavation in tunnels with fractured surrounding rock conditions according to claim 5, characterized in that: The ratio of the number of blasting holes in the fourth blasting hole (6) and the fifth blasting hole (7) is 8:
9. The depth of each hole in the fourth blasting hole (6) and the fifth blasting hole (7) is 1.5m and the diameter is 42mm.
7. The blasting control structure for over- and under-excavation of tunnels in fractured surrounding rock conditions according to claim 1, characterized in that: The second tunnel blasting hole includes a sixth blasting hole (8), and at least two sixth blasting holes (8) are provided. The detonation time interval between any two adjacent sixth blasting holes (8) is set to 2ms. The single-hole charge coefficient of the sixth blasting hole (8) is 0.
3. The blasting method of the sixth blasting hole (8) is set to a top-down detonation method.
8. The blasting control structure for over- and under-excavation in tunnels with fractured surrounding rock conditions according to claim 1, characterized in that: The second tunnel section (2) is provided with at least 3 holes (9), and the distance between any two adjacent holes (9) is 30cm.