A blasting + milling soft rock composite excavation method based on the theory of surrounding rock loose circle

Abstract

The application discloses a kind of based on surrounding rock loose circle theory's blasting+milling soft rock composite excavation method, comprising, based on surrounding rock loose circle theory numerical simulation software calculation, blasting different size section;The plastic zone calculated by the numerical simulation software is most similar to tunnel design contour, at this time it is the best blasting section;According to the size of the best blasting section design blasthole layout, determine blasting parameter;Contrast design drawing in the face measurement positioning, slot drilling, hole inspection is qualified after line charging;Initiation sequence is set as: slot eye-assistant eye-peripheral eye;Using total station lofting out excavation contour line or through auxiliary infrared irradiation excavation contour;Milling machine excavation is used, and the blasting section is trimmed to tunnel design contour after blasting.The present application is based on loose circle theory, and the plastic zone of different blasting section excavation is simulated using numerical simulation software, so as to achieve the minimum damage to the surrounding rock of the designed tunnel section contour.

Description

Technical Field

[0001] This invention relates to the technical field of construction in underground engineering and underground structures such as tunnels, and particularly to a composite excavation method for soft rock based on the theory of loosened surrounding rock, which combines blasting and milling. Background Technology

[0002] Excavation plays a crucial role in the entire tunnel construction process, and the excavation method determines the construction time and quality.

[0003] Currently, there are two main methods for excavating mountain tunnels in my country: drill-and-blast method and mechanical excavation method. Smooth blasting technology, supported by the New Austrian Tunneling Method (NATM), can effectively control excavation quality and is relatively low-cost for most tunnels in hard surrounding rock. However, in engineering practice, it has been found that for Class IV or V soft rock with well-developed joints, even with smooth blasting, severe over- and under-excavation phenomena still occur due to the significant disturbance to the surrounding rock mass.

[0004] TBMs are more suitable for use in long tunnels due to their high price. Milling machines cause less disturbance during construction, but their advance is limited and their construction efficiency is less than that of the drill-and-blast method.

[0005] Therefore, developing a high-efficiency and damage-controlled excavation method for rock breaking and accelerating tunneling is an urgent problem to be solved in tunnel and underground structure construction. Summary of the Invention

[0006] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0007] In view of the aforementioned existing problems, the present invention is proposed.

[0008] Therefore, the technical problem solved by this invention is that existing methods for excavating tunnels in soft rock formations in mountainous areas cannot satisfy the problem of achieving both a small excavation damage zone and construction efficiency.

[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solution: including numerical simulation software calculation based on the theory of loosened surrounding rock, and blasting cross sections of different sizes;

[0010] The plastic zone calculated by the numerical simulation software is closest to the tunnel design profile, and this is the optimal blasting section.

[0011] Design the borehole layout diagram based on the optimal blasting cross-section size, and determine the blasting parameters;

[0012] Measure and locate the working face according to the design drawings, cut grooves and drill holes, and connect the lines to load explosives after the holes pass inspection;

[0013] The detonation sequence is set as follows: cut-out eye—auxiliary eye—surrounding eye;

[0014] The excavation outline is laid out using a total station or by using auxiliary infrared illumination.

[0015] A milling machine was used for excavation, and the blasted section was trimmed to the tunnel design outline.

[0016] As a preferred embodiment of the blasting + milling composite excavation method for soft rock based on the theory of loosened surrounding rock as described in this invention, the numerical simulation software calculations include:

[0017] A numerical model was established based on geological survey data;

[0018] In numerical simulation software, the tunnel design outline is shrunk inwards at equal intervals and divided into multiple meshes;

[0019] Blasting different sized cross sections.

[0020] As a preferred embodiment of the blasting + milling composite excavation method for soft rock based on the loosened rock zone theory described in this invention, determining the optimal blasting cross-section includes:

[0021] The numerical simulation software was used to simulate blasting of cross-sections of different sizes and to calculate the plastic zone;

[0022] When the designed blasting range is within 0.9m of the tunnel design outline, the plastic zone of the surrounding rock at the tunnel sidewall just touches the tunnel design outline. This is the blasting section with the least damage to the surrounding rock and the highest blasting efficiency.

[0023] This is the optimal blasting cross section.

[0024] As a preferred embodiment of the blasting + milling composite excavation method for soft rock based on the loosened rock zone theory described in this invention, the determination of blasting parameters includes:

[0025] Using smooth blasting excavation, the depth of the blast holes and the amount of explosives are strictly controlled during blasting.

[0026] Digital detonators with 1-15 segments are used, and No. 2 emulsion explosive is used. The specifications are as follows: Medicine roll;

[0027] The detonation system uses detonating cords for detonation transmission and a hybrid connection detonation network with clusters as the main component.

[0028] Network initiation uses an in-hole micro-delay method, selecting 1-15 segment non-electric millisecond detonators.

[0029] As a preferred embodiment of the blasting + milling composite excavation method for soft rock based on the loosened zone theory of surrounding rock described in this invention, the blasting parameters include: total explosive quantity, explosive consumption per unit, detonator segment, detonation sequence, and charging method.

[0030] As a preferred embodiment of the blasting + milling composite excavation method for soft rock based on the loosened rock zone theory described in this invention, the method includes: measuring and positioning at the working face according to the design drawings.

[0031] Construction surveying is carried out for each cycle of tunnel excavation to control the excavation cross-section. The tunnel excavation outline and blast hole positions are drawn on the tunnel face with red paint, with an error not exceeding 5cm. A laser collimator is used to control the excavation direction.

[0032] As a preferred embodiment of the blasting + milling composite excavation method for soft rock based on the loosened zone theory of surrounding rock described in this invention, the following features are provided: during drilling, the excavation hole is kept parallel to the tunnel axis; except for the bottom hole, the openings of other blast holes are 5cm lower than the bottom of the hole to allow rock powder to flow out naturally during drilling; the outer angle of the peripheral holes is controlled within 3° to 4°; the slotted holes are strictly prohibited from penetrating or intersecting each other; and the bottom of the slotted hole is 20cm deeper than other blast holes.

[0033] As a preferred embodiment of the blasting + milling composite excavation method for soft rock based on the loosened zone theory of surrounding rock described in this invention, the following is provided: before charging the explosives, the blast holes are cleaned with high-pressure air and the number of blast holes is checked.

[0034] When loading explosives, designated personnel should classify the sections and load explosives according to the blasting design sequence. The loading operation should be carried out in groups and sections, with designated personnel and positions to ensure that the loading operation is carried out in an orderly manner and to prevent confusion between the detonator sections.

[0035] After each blast hole is filled with explosives, it is plugged with blasting mud.

[0036] The detonation adopts a compound network, non-electric detonation system, and each group is controlled to have no more than 12 wires when connected;

[0037] Connecting detonators uses the same segment, and uses detonators of the lower segment;

[0038] After the detonators are connected, a designated person will inspect them to check the connection quality and whether any detonators are missing. Once the inspection is completed, the detonation will proceed.

[0039] The peripheral eye uses a spaced-out charge structure, and the charge roll diameter is [missing information]. To overcome the resistance of the bottom blast hole, half a standard explosive charge is placed at the bottom of the blast hole to make the blast layer easier to detach from the rock mass;

[0040] Other eye medications use a continuous loading structure, with a cartridge diameter of [missing information].

[0041] As a preferred embodiment of the blasting + milling composite excavation method for soft rock based on the loosened rock zone theory described in this invention, the detonation sequence includes:

[0042] Multi-stage micro-delay detonation is adopted, in which the peripheral eye of the main detonation zone is detonated in two stages compared to the auxiliary eye, and the same detonator is used;

[0043] Non-electric millisecond detonators are used in the main blast zone, while detonating cords are used to detonate the flash blast holes simultaneously.

[0044] As a preferred embodiment of the blasting + milling composite excavation method for soft rock based on the loosened zone theory of surrounding rock described in this invention, the following applies: during the excavation process, attention should be paid to observing the changes in the surrounding rock and the blasting effect, and the drilling and blasting design parameters should be adjusted in a timely manner.

[0045] An 1140V transformer is installed at the tunnel entrance and connected to a mobile distribution box inside the tunnel via a cable. The cable on the cantilever tunneling machine's reel is then connected to the distribution box to supply power to the tunneling machine.

[0046] A 50mm plastic hose is connected to the back of the tunneling machine and then to the three-stage sedimentation tank at the tunnel entrance. The clear water after sedimentation is drained into the existing ditch, and the accumulated sludge is cleaned regularly.

[0047] The beneficial effects of this invention are as follows: Based on the loosened zone theory, this invention uses numerical simulation software to simulate the plastic zone of excavation at different blasting cross-sections in order to minimize damage to the surrounding rock of the designed tunnel cross-section. It also combines the advantages of drill-and-blast and milling methods, achieving both efficient excavation and controlled damage to the surrounding rock. This avoids the disadvantages of tunnel boring machine excavation, such as slow excavation speed and high tool wear, as well as the disadvantage of large damage to the surrounding rock caused by blasting. Finally, the blasting parameters for the next cycle are adjusted and optimized based on the actual blasting results on site. Attached Figure Description

[0048] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0049] Figure 1 This is a schematic diagram of the process of the blasting + milling composite excavation method for soft rock based on the theory of loosened surrounding rock of the present invention;

[0050] Figure 2 This is a diagram showing the elastoplastic stress distribution around the circular tunnel of the present invention.

[0051] Figure 3 This is a cross-sectional outline diagram of a simulated blasting tunnel according to the present invention;

[0052] Figure 4 This is a diagram of the plastic zone surrounding the blasting profile calculated by the software numerical calculation of the present invention;

[0053] Figure 5 This is a diagram showing the layout of the blast holes for the present invention;

[0054] Figure 6 This is a diagram of the peripheral eye delivery structure of the present invention;

[0055] Figure 7 This is a diagram of the continuous charge structure of the present invention;

[0056] Figure 8 This is a construction drawing for the excavation of the milling machine according to the present invention.

[0057] Figure descriptions: 100—Tunnel design outline; 200—Different cross-section sizes; 300—Optimal blasting cross-section; 101—Resulting plastic zone; A—Cut-out hole; B—Auxiliary hole; C—Surrounding hole; 102—Detonator; 103— 104—Detonating cord and bamboo strips; 105—Leading wire or detonating tube; 106—Firing clay; 107— Medicine roll; 108—milling machine. Detailed Implementation

[0058] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0059] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0060] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0061] This invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of this invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not be construed as limiting the scope of protection of this invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0062] Furthermore, in the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used solely for the convenience of describing the invention and for 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 the invention. In addition, the terms "first," "second," or "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0063] Unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" in this invention should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; similarly, they can refer to mechanical connections, electrical connections, or direct connections, or indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0064] Example 1

[0065] Reference Figures 1 to 8 This is one embodiment of the present invention, which provides a blasting + milling composite excavation method for soft rock based on the theory of loosened surrounding rock, specifically including:

[0066] S1: Numerical simulation software calculations were performed based on the theory of loosened surrounding rock to attempt to calculate the blasting of different sized cross sections of 200.

[0067] S2: The simulation shows that the edge of the plastic zone 101 obtained when blasting a certain cross section is closest to the tunnel design outline 100. This is the optimal blasting cross section 300.

[0068] S3: Design the borehole layout diagram according to the size of the blasting cross section, and determine the total amount of explosives, explosive consumption per unit, detonator section, detonation sequence, charging method and blasting parameters.

[0069] S4: Measure and locate the working face according to the design drawings, cut grooves and drill holes, and connect the lines to load explosives after the holes pass inspection.

[0070] S5: The detonation sequence is as follows: first detonate the slotted eye A, then detonate the auxiliary eye B, and finally detonate the surrounding eye C.

[0071] S6: Use a total station to lay out the excavation outline or use auxiliary infrared illumination to lay out the excavation outline.

[0072] S7: Milling machine 108 excavates, and the cross-section after blasting is trimmed to the tunnel design outline.

[0073] Furthermore, numerical simulation software calculations include:

[0074] A numerical model was established based on geological survey data;

[0075] In numerical simulation software, the tunnel design outline is shrunk inwards at equal intervals and divided into multiple meshes;

[0076] Blasting different sized cross sections.

[0077] Specifically, determining the optimal blasting cross-section includes:

[0078] Numerical simulation software was used to simulate blasting of cross sections of different sizes and to calculate the plastic zone.

[0079] When the designed blasting range is within 0.9m of the tunnel design outline, the plastic zone of the surrounding rock at the tunnel sidewall just touches the tunnel design outline. This is the blasting section with the least damage to the surrounding rock and the highest blasting efficiency.

[0080] This is the optimal blasting cross section.

[0081] Preferably, determining blasting parameters includes: using smooth blasting excavation methods and strictly controlling the depth of the blast holes and the amount of explosives during blasting;

[0082] The 102 digital detonator with 1-15 segments is used, and the explosive is No. 2 emulsion explosive with the following specifications: Medicine roll;

[0083] The detonation system uses detonating cords for detonation transmission and a hybrid connection detonation network with clusters as the main component.

[0084] Network initiation uses an in-hole micro-delay method, selecting 1-15 segment non-electric millisecond detonators.

[0085] This embodiment also requires explanation of the following: Measuring and positioning at the working face according to the design drawings includes:

[0086] Construction surveying is carried out for each cycle of tunnel excavation to control the excavation cross-section. The tunnel excavation outline and blast hole positions are drawn on the tunnel face with red paint, with an error not exceeding 5cm. A laser collimator is used to control the excavation direction.

[0087] When drilling, the excavation hole should be kept parallel to the tunnel axis. Except for the bottom hole, the opening of other blast holes should be 5cm lower than the bottom of the hole to allow rock powder to flow out naturally during drilling. The outer angle of the peripheral holes should be controlled within 3° to 4°. The cut holes must not be drilled through or intersect each other. The bottom of the cut hole should be 20cm deeper than other blast holes.

[0088] Before loading the explosive, clean the blast holes with high-pressure air and check the number of blast holes;

[0089] When loading explosives, designated personnel should classify the sections and load explosives according to the blasting design sequence. The loading operation should be carried out in groups and sections, with designated personnel and positions to ensure that the loading operation is carried out in an orderly manner and to prevent confusion between the detonator sections.

[0090] After each blast hole is filled with explosives, it is plugged with blasting mud.

[0091] The detonation adopts a compound network, non-electric detonation system, and each group is controlled to have no more than 12 wires when connected;

[0092] Connecting detonators uses the same segment, and uses detonators of the lower segment;

[0093] After the detonators are connected, a designated person will inspect them to check the connection quality and whether any detonators are missing. Once the inspection is completed, the detonation will proceed.

[0094] The peripheral eye uses a spaced-charge structure, employing To overcome the resistance of the bottom blast hole, half a standard explosive cartridge is placed at the bottom of the blast hole to make the blast layer easier to detach from the rock mass.

[0095] Other eyes use a continuous delivery structure, employing... After each eye is filled with gunpowder, it is sealed with clay 106.

[0096] Furthermore, the detonation sequence includes:

[0097] Multi-stage micro-delay detonation is adopted, in which the peripheral eye of the main detonation zone is detonated in two stages compared to the auxiliary eye, and the same detonator is used;

[0098] Non-electric millisecond detonators are used in the main blast zone, while detonating cords are used to detonate the flash blast holes simultaneously.

[0099] Preferably, during the excavation process, attention should be paid to the changes in the surrounding rock and the blasting effect, and the drilling and blasting design parameters should be adjusted in a timely manner; an 1140V transformer should be installed at the tunnel entrance and connected to a mobile distribution box inside the tunnel via a cable, and the cable on the cantilever tunneling machine's reel should be connected to the distribution box to supply power to the tunneling machine; a 50mm plastic hose should be connected to the back of the tunneling machine and connected to the three-stage sedimentation tank at the tunnel entrance, and the clear water after sedimentation should be drained into the existing ditch, and the accumulated mud should be cleaned regularly.

[0100] Preferably, in this embodiment, a total station is used to lay out the excavation outline, with an excavation outline point every 50cm in the circumference. These points are connected by red paint to form the excavation outline control line. An excavation elevation control line is set at a position 1.5m away from the arch foot to control the excavation elevation of the arch foot.

[0101] Alternatively, auxiliary infrared illumination can be used to outline the excavation contour, allowing the tunnel boring machine to control the tunnel perimeter when cutting rock. The infrared projector is fixed to the completed initial support surface by two M16 bolts. The projector can be positioned by moving the screw laterally and rotating the screw 360°. Before excavation, the infrared projector's illumination point is precisely located using a total station. During excavation, the excavation contour is controlled based on the infrared projection point.

[0102] Based on the tunnel boring machine's own operating range, the tunnel needs to be excavated in upper and lower steps. The upper step is 6m high and the lower step is 3.3m high. According to the actual excavation situation on site, in order to facilitate mechanical operation, the excavation area of ​​the upper step should be larger than that of the lower step, which is conducive to the utilization of the advantages of mechanization. The upper step tunnel boring machine is more flexible in construction and has a more favorable working length space than the lower step, which is conducive to improving the construction progress.

[0103] Further preferred options include the Dashazui Tunnel, located on the Jinyang-Ningnan section of the Yibin-Panzhihua Expressway in Liangshan Prefecture, Sichuan Province. The tunnel is designed with separate left and right lines, with a maximum burial depth of 375.1m and surrounding rock grades V and IV. Grade IV surrounding rock is prone to loosening and deformation during excavation, while Grade V surrounding rock has poor self-stabilizing capacity and is prone to large collapses during excavation, making construction difficult. The surrounding rock is composed of sericite phyllite with steep dips and a strike that intersects the tunnel at a large angle. In this construction section, if the drill-and-blast method is used, it will not only result in over-excavation and under-excavation but also cause great disturbance to the surrounding rock, damaging its self-supporting capacity. Although using a milling machine can ensure excavation quality, it is not conducive to the construction period.

[0104] Based on theoretical analysis and numerical calculations of the loosening zone, and combined with relevant construction experience, this section adopted a combined blasting and milling method for soft rock excavation. Adhering to the principles of safety, reliability, environmental protection, and advanced technology, this method successfully and economically solved the shortcomings of over-excavation and under-excavation in drilling and blasting tunnel construction in adverse geological conditions and the slow progress of mechanical excavation.

[0105] It should be noted again in this embodiment that the blasting + milling composite excavation method for soft rock based on the theory of loosened surrounding rock successfully solved the problems of serious over- and under-excavation in soft rock excavation and blasting during the construction of Dashazui Tunnel, and slow progress of mechanical excavation. At the same time, it provides theoretical support for the combination of the two methods and scientifically and rigorously demonstrates the optimal blasting cross section.

[0106] On the one hand, the excavation method provided in this embodiment avoids over- and under-excavation caused by drilling and blasting in soft rock tunnels with poor geological conditions, saves concrete usage, avoids the slow progress of mechanical excavation, and saves construction time. On the other hand, supported by the loosened zone theory and calculated by numerical simulation software, a balanced combination point is found between drilling and blasting and mechanical excavation, eliminating the choice between the two methods. This solves the pain points of over- and under-excavation in blasting and slow mechanical construction. The proposed method can provide valuable experience for similar projects and can serve as a reference for future similar projects. At the same time, the method of this invention reduces tunnel over-excavation, effectively saves material resources, protects the environment, and improves environmental benefits during construction.

[0107] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A composite excavation method for soft rock based on the theory of loosened surrounding rock, characterized in that: include, Numerical simulation software was used to calculate the blasting of cross sections of different sizes based on the theory of loosened surrounding rock. The plastic zone of the blasting section of different sizes calculated by the numerical simulation software is closest to the tunnel design profile, and this is the optimal blasting section. Design the borehole layout diagram based on the optimal blasting cross-section size, and determine the blasting parameters; Measure and locate the working face according to the design drawings, cut grooves and drill holes, and connect the lines to load explosives after the holes pass inspection; The detonation sequence is set as follows: cut-out eye—auxiliary eye—surrounding eye; The excavation outline is laid out using a total station or by using auxiliary infrared illumination. A milling machine was used for excavation, and the blasted section was trimmed to the tunnel design outline.

2. The blasting + milling composite excavation method for soft rock based on the loosened zone theory of surrounding rock as described in claim 1, characterized in that: The numerical simulation software calculations include, A numerical model was established based on geological survey data; In numerical simulation software, the tunnel design outline is shrunk inwards at equal intervals and divided into multiple meshes; Blasting different sized cross sections.

3. The blasting + milling composite excavation method for soft rock based on the loosened zone theory of surrounding rock according to claim 1 or 2, characterized in that: Determining the optimal blasting cross-section includes, The numerical simulation software was used to simulate blasting of cross-sections of different sizes and to calculate the plastic zone; When the designed blasting range is within 0.9m of the tunnel design outline, the plastic zone of the surrounding rock at the tunnel sidewall just touches the tunnel design outline. This is the blasting section with the least damage to the surrounding rock and the highest blasting efficiency. This is the optimal blasting cross section.

4. The blasting + milling composite excavation method for soft rock based on the loosened zone theory of surrounding rock as described in claim 3, characterized in that: Determining the blasting parameters includes, Using smooth blasting excavation, the depth of the blast holes and the amount of explosives are strictly controlled during blasting. Digital detonators with 1-15 segments are used, and No. 2 emulsion explosive is used. The specifications are as follows: Medicine roll; The detonation system uses detonating cords for detonation transmission and a hybrid connection detonation network with clusters as the main component. Network initiation uses an in-hole micro-delay method, selecting 1-15 segment non-electric millisecond detonators.

5. The blasting + milling composite excavation method for soft rock based on the loosened zone theory of surrounding rock according to claim 4, characterized in that: The blasting parameters include total explosive quantity, explosive consumption per unit, detonator section, detonation sequence, and loading method.

6. The blasting + milling composite excavation method for soft rock based on the loosened zone theory of surrounding rock as described in claim 5, characterized in that: The measurement and positioning at the working face according to the design drawings includes: Construction surveying is carried out for each cycle of tunnel excavation to control the excavation cross-section. The tunnel excavation outline and blast hole positions are drawn on the tunnel face with red paint, with an error not exceeding 5cm. A laser collimator is used to control the excavation direction.

7. The blasting + milling composite excavation method for soft rock based on the loosened zone theory of surrounding rock as described in claim 6, characterized in that: When drilling, the excavation hole should be kept parallel to the tunnel axis. Except for the bottom hole, the opening of other blast holes should be 5cm lower than the bottom of the hole to allow rock powder to flow out naturally during drilling. The outer angle of the peripheral holes should be controlled within 3° to 4°. The cut holes must not be drilled through or intersect each other. The bottom of the cut hole should be 20cm deeper than other blast holes.

8. The blasting + milling composite excavation method for soft rock based on the loosened zone theory of surrounding rock according to claim 7, characterized in that: Before loading the explosive, clean the blast holes with high-pressure air and check the number of blast holes; When loading explosives, designated personnel should classify the sections and load explosives according to the blasting design sequence. The loading operation should be carried out in groups and sections, with designated personnel and positions to ensure that the loading operation is carried out in an orderly manner and to prevent confusion between the detonator sections. After each blast hole is filled with explosives, it is plugged with blasting mud. The detonation adopts a compound network, non-electric detonation system, and each group is controlled to have no more than 12 wires when connected; Connecting detonators uses the same segment, and uses detonators of the lower segment; After the detonators are connected, a designated person will inspect them to check the connection quality and whether any detonators are missing. Once the inspection is completed, the detonation will proceed. The peripheral eye uses a spaced-out charge structure, and the charge roll diameter is [missing information]. To overcome the resistance of the bottom blast hole, half a standard explosive charge is placed at the bottom of the blast hole to make the blast layer easier to detach from the rock mass; Other eye medications use a continuous loading structure, with a cartridge diameter of [missing information].

9. The blasting + milling composite excavation method for soft rock based on the loosened zone theory of surrounding rock as described in claim 8, characterized in that: The detonation sequence includes, Multi-stage micro-delay detonation is adopted, in which the peripheral eye of the main detonation zone is detonated in two stages compared to the auxiliary eye, and the same detonator is used; Non-electric millisecond detonators are used in the main blast zone, while detonating cords are used to detonate the flash blast holes simultaneously.

10. The blasting + milling composite excavation method for soft rock based on the loosened zone theory of surrounding rock according to claim 9, characterized in that: During the excavation process, pay close attention to the changes in the surrounding rock and the blasting effect, and adjust the drilling and blasting design parameters in a timely manner. An 1140V transformer is installed at the tunnel entrance and connected to a mobile distribution box inside the tunnel via a cable. The cable on the cantilever tunneling machine's reel is then connected to the distribution box to supply power to the tunneling machine. A 50mm plastic hose is connected to the back of the tunneling machine and then to the three-stage sedimentation tank at the tunnel entrance. The clear water after sedimentation is drained into the existing ditch, and the accumulated sludge is cleaned regularly.

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