Tunnel construction method

Abstract

The invention relates to a tunnel construction method, and belongs to the field of tunnel construction.The tunnel construction method comprises the steps that S100, a temporary steel arch is erected, specifically, S110, a bottom steel plate is arranged; s120, an annular arch frame is installed; s130, the annular arch frame is fixed; and S140, longitudinal I-shaped steel is installed. S200, grouting reinforcement is conducted, specifically, S220, a first batch of grouting pipes are inserted into the inner wall of the tunnel; s240, first-time grouting is conducted through the first batch of grouting pipes; s260, a second batch of grouting pipes are inserted into the inner wall of the tunnel; and S270, second-time grouting is conducted through a second batch of grouting pipes. S300, dismantling and primary support reconstruction are conducted, specifically, the temporary steel arch is dismantled; and original secondary lining concrete is dismantled, an original primary support is dismantled, and primary support reconstruction is conducted. And S400, inverted arch construction, wherein inverted arch excavation, inverted arch primary support steel arch laying, inverted arch lining steel bar laying, formwork installation, inverted arch concrete pouring and inverted arch backfilling are included. And S500, water prevention and drainage and secondary lining reconstruction.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel construction, and in particular relates to a tunnel construction method. Background Art

[0002] Tunnels are engineering structures buried in the ground, and are a form of human use of underground space. Tunnels can be divided into traffic tunnels, hydraulic tunnels, municipal tunnels, mining tunnels, and military tunnels.

[0003] However, as time goes by, the tunnel will crack and fall off due to the aging of its structure, or may collapse as a whole due to the aging of the structure. Therefore, the tunnel needs to be renovated or rebuilt.

[0004] In the prior art, there is no efficient and fast method for renovating or rebuilding a tunnel. Therefore, it is urgent to provide a tunnel construction method to fill this gap. Summary of the invention

[0005] In view of the shortcomings existing in the related technologies, the present invention provides a tunnel construction method, the entire construction method has a clear process and reasonable steps, which not only ensures the construction quality but also improves the construction efficiency. At the same time, by strengthening temporary support and grouting reinforcement and other measures, the safety risks in the construction process are reduced, and the life safety of the construction personnel is guaranteed, so as to solve the technical problem that the existing technology cannot renovate or rebuild the tunnel.

[0006] The present invention provides a tunnel construction method, comprising:

[0007] S100, erect temporary steel arch frame, including:

[0008] S110, install the bottom steel plate at the bottom of the tunnel near the walls on both sides;

[0009] S120, installing the circumferential arch frames, and arranging the circumferential arch frames at intervals along the length direction of the tunnel;

[0010] S130, fixing the annular arch frame, fixing the annular arch frame to the tunnel;

[0011] S140, install the longitudinal I-beam, and connect and fix the longitudinal I-beam to the annular arch frame;

[0012] After step S100, step S200 is also included;

[0013] S200, grouting reinforcement, specifically including:

[0014] S220, inserting the first batch of grouting pipes into the inner wall of the tunnel;

[0015] S240, performing the first grouting through the first batch of grouting pipes;

[0016] S260, inserting a second batch of grouting pipes into the inner wall of the tunnel;

[0017] S270, performing a second grouting through a second batch of grouting pipes;

[0018] After step S200, step S300 is also included;

[0019] S300, demolition and reconstruction of primary support, specifically including: demolition of temporary steel arch frame; demolition of original secondary lining concrete, demolition of original primary support and reconstruction of primary support;

[0020] After step S300, step S400 is also included;

[0021] S400, invert construction, including: invert excavation, laying of invert primary support steel arch frame, laying of invert lining steel bars, installation of formwork, pouring of invert concrete, pouring of invert backfill;

[0022] After step S400, step S500 is also included;

[0023] S500, waterproofing and drainage and secondary lining reconstruction: laying waterproofing and drainage on the inner wall of the tunnel and re-casting the inner wall of the tunnel.

[0024] In the technical solution, by setting up temporary steel arches, including setting up bottom steel plates, installing and fixing circumferential arches, and installing longitudinal I-beams for reinforcement, the overall stability and safety of the tunnel during construction are significantly improved, and safety accidents such as tunnel collapse are effectively prevented. Through the grouting reinforcement step, two groutings can be performed to more comprehensively fill the cracks and gaps in the tunnel surrounding rock, enhance the integrity of the surrounding rock, and further improve the bearing capacity and waterproof performance of the tunnel. The dismantling and initial support reconstruction step not only removes possible structural hazards, but also ensures the long-term stability and durability of the tunnel structure by reconstructing the initial support system. The invert construction step ensures the construction quality of the invert through standardized excavation, laying of initial support steel arches, laying of lining steel bars, installation of formwork and pouring of concrete, and improves the overall bearing capacity and deformation resistance of the tunnel. The drainage and secondary lining reconstruction step waterproofs the inner wall of the tunnel, and re-casts the secondary lining to perform the final maintenance of the tunnel, providing a reliable guarantee for the long-term operation of the tunnel. In this application, the entire construction method has a clear process and reasonable steps, which not only ensures the construction quality but also improves the construction efficiency. At the same time, by strengthening temporary support and grouting reinforcement measures, the safety risks in the construction process are reduced and the life safety of the construction workers is guaranteed.

[0025] In some embodiments, in step S220, the specific steps include:

[0026] Inserting the first batch of grouting tubes into the tunnel wall in a rectangular array;

[0027] Eleven rows of grouting pipes are inserted in sequence along the circumferential direction of the tunnel wall, and each row of grouting pipes is arranged at intervals along the length direction of the tunnel; among them, the sixth row of grouting pipes is inserted into the arch and perpendicular to the ground, and the remaining 10 rows of grouting pipes are symmetrically arranged on both sides of the sixth row of grouting pipes in a 50-50 ratio.

[0028] In the technical solution, through this design, the first batch of grouting pipes can be inserted into the wall of the tunnel in a rectangular array, ensuring a large area coverage of the tunnel wall by the first batch of grouting pipes, thereby improving the effect and efficiency of the first grouting.

[0029] In some of the embodiments, in step S260, the specific steps include: inserting a second batch of grouting pipes into the wall of the tunnel in a rectangular array, and when inserting the second batch of grouting pipes, controlling the spacing between the inserted second batch of grouting pipes and any adjacent first batch of grouting pipes to be the same.

[0030] In the technical solution, the second batch of grouting pipes are inserted into the gaps of the first batch of grouting pipes. The second grouting can fill the gaps missed by the first grouting, ensuring that the grouting pipes fully cover the tunnel wall without missing any areas. This layout allows the grouting material to evenly and fully fill the cracks and gaps in the tunnel surrounding rock, thereby enhancing the integrity and stability of the tunnel structure and improving the effect of grouting reinforcement.

[0031] In some embodiments, in step S260, the specific steps of inserting the second batch of grouting pipes are as follows: among the grouting pipes inserted in the first batch in a rectangular array, the four closest grouting pipes inserted in the first batch are calibrated as a, b, c, and d; a, b, c, and d are the four corners of the rectangle, respectively; a and c are diagonals, and b and d are diagonals; the corresponding grouting pipes to be inserted in the second batch are inserted to the midpoint of the diagonal formed by a and c, or inserted into the midpoint of the diagonal formed by b and d.

[0032] In the technical solution, the insertion position of the second batch of grouting pipes is selected at the midpoint of the corresponding diagonal line in the grouting pipes formed by the first batch of rectangular arrays. This layout not only takes into account the symmetry of the tunnel structure, but also fully considers the diffusion law of the grouting material in the surrounding rock. It helps to achieve uniform distribution of grouting materials, reduces the problem of local stress concentration caused by uneven grouting, and thus optimizes the grouting layout. In addition, this method facilitates manual rapid alignment when inserting the grouting pipe, improving work efficiency.

[0033] In some embodiments, in step S300, the specific steps include:

[0034] S310, dismantle the temporary steel arch;

[0035] S320, first job-hopping removal;

[0036] S330, first primary branch reconstruction;

[0037] S340, second job-hopping removal;

[0038] S350, second primary branch reconstruction.

[0039] In the technical solution, the temporary steel arch frame is first dismantled to provide space for the subsequent trench removal and primary support reconstruction. As a temporary support structure during the construction process, the timely removal of the temporary steel arch frame helps to reduce safety hazards during the construction process and ensure construction safety. Through the first trench removal and the second trench removal, part of the original support structure can be removed in sections and steps, which helps to more flexibly respond to geological changes that may be encountered during tunnel excavation. The trench removal strategy can be adjusted according to the actual situation on site to ensure the stability and safety of the tunnel structure. The first primary support reconstruction and the second primary support reconstruction can optimize the support structure and parameters according to the actual geological conditions revealed during the tunnel excavation process by reconstructing the initial support system, thereby improving the support effect. The new initial support system can better adapt to the deformation and stress changes of the tunnel surrounding rock and ensure the long-term stability of the tunnel structure. The trench removal and primary support reconstruction adopt a segmented construction method to reduce interference with the construction activities of the unremoved section. This construction method helps to maintain order and efficiency on the construction site, and also helps to reduce the impact of construction activities on the surrounding environment. And through accurate planning of the removal of the jump slot and the reconstruction of the initial support, the construction cost can be effectively controlled. Reasonable arrangement of the construction sequence and resource input can reduce unnecessary waste and rework, thereby improving economic benefits. In addition, the alternation of the removal of the jump slot and the reconstruction of the initial support helps to achieve the continuity and efficiency of the construction process. The construction personnel can flexibly adjust the construction plan according to the construction progress and on-site conditions to ensure the smooth completion of the construction task.

[0040] In some embodiments, in step S300,

[0041] S320, the specific steps of the first demolition by skipping are: marking the first demolition area at intervals along the length direction of the tunnel, and removing the original secondary lining concrete and the original primary support in the first demolition area;

[0042] S330. The specific steps of the first initial support reconstruction are: erecting an initial support steel arch frame in the first demolition area, laying a double-layer steel mesh, and filling the first demolition area with sprayed concrete.

[0043] In the technical solution, during the first demolition by slot-hopping, the first demolition area is marked at intervals along the length of the tunnel to ensure the orderly progress of the construction. This method of segmented construction helps to control the construction rhythm and avoid excessive impact on the entire tunnel structure. And by defining clear demolition areas, we can concentrate our efforts and resources on demolition operations and reduce construction interference in other undemolished areas. This helps to keep the construction site clean and orderly and improve construction efficiency. Moreover, the method of slot-hopping demolition allows construction personnel to flexibly adjust the construction plan according to actual geological conditions. During the demolition process, if it is found that the geological conditions are not in line with expectations, the subsequent construction plan can be adjusted in time to ensure the safety and stability of the tunnel structure.

[0044] In the first initial support reconstruction, the initial support steel arch frame was erected in the first demolition area, and a double-layer steel mesh was laid, which significantly enhanced the strength and stability of the support system. This structure can better withstand the deformation and stress changes of the tunnel surrounding rock, ensuring the long-term safety of the tunnel structure. In addition, the use of shotcrete for filling can ensure the close integration of the support system and the tunnel surrounding rock. Shotcrete has good compactness and adhesion, and can fill the gap between the support system and the surrounding rock to improve the support effect. In addition, the construction speed of shotcrete is fast, and the support system can be completed in a short time. This helps to shorten the construction period and improve construction efficiency. By reconstructing the initial support system, the construction environment can be improved. The new support system can provide better support and protection, and reduce safety hazards and dust pollution during construction.

[0045] In some embodiments, in step S300,

[0046] S340, the specific steps of the second demolition by skipping are: marking a portion of the tunnel excluding the first demolition area as the second demolition area, and removing the original secondary lining concrete in the second demolition area;

[0047] S350. The specific steps of the second primary support reconstruction are: erecting the initial support steel arch frame in the second demolition area, laying a double-layer steel mesh, and filling the second demolition area with shotcrete.

[0048] In the technical solution, in the second slot-jump demolition, the zoning-refined construction method helps to better control the construction progress and quality. It allows the construction team to accurately handle the remaining areas after the first demolition and initial support reconstruction are completed. By dividing the demolition work into two stages, the mutual influence between different construction stages can be reduced. After the first demolition and initial support reconstruction are completed, the tunnel structure has been stabilized to a certain extent. When the second slot-jump demolition is carried out, the impact on the surrounding area will be relatively small. The second slot-jump demolition area may face different geological conditions from the first demolition area. Through zoning construction, the construction team can adjust the construction plan according to the actual situation, better adapt to geological changes, and ensure construction safety and the stability of the tunnel structure.

[0049] During the second reconstruction of the primary support, the primary support steel arch was erected in the second demolition area, and a double-layer steel mesh was laid and filled with shotcrete. This series of operations significantly enhanced the overall stability of the tunnel structure. The new primary support system can better withstand the surrounding rock pressure and deformation, ensuring the safety and durability of the tunnel during operation.

[0050] In some embodiments, in step S400, specifically including:

[0051] S410, excavating the first invert; planning a plurality of first excavation areas at intervals on the ground along the length direction of the tunnel; and demolishing the first excavation areas;

[0052] S420, laying of the initial supporting steel arch frame of the invert for the first time;

[0053] S430, laying the invert lining steel bars above the initial supporting steel arch frame of the invert in the first excavation area, installing the formwork, pouring the invert concrete, and pouring the invert backfill;

[0054] S440, second invert excavation; the tunnel surface except the first excavation area is planned as the second excavation area; the second excavation area is demolished;

[0055] S450, laying of the primary supporting steel arch frame of the invert for the second time;

[0056] S460. Lay the arch lining steel bars above the primary supporting steel arch frame in the second excavation area, install the formwork, pour the arch concrete, and pour the arch backfill.

[0057] In some embodiments, in step S400:

[0058] The specific steps of S420 include: laying the inverted arch primary support steel arch frame at intervals in the first excavation area along the length direction of the tunnel; connecting the inverted arch primary support steel arch frame with the corresponding initial support steel arch frame to form a closed loop structure;

[0059] The specific steps of S450 include: laying the initial supporting steel arch frames of the inverted arch at intervals along the length direction of the tunnel in the second excavation area; and connecting the initial supporting steel arch frames of the inverted arch with the corresponding initial supporting steel arch frames to form a closed-loop structure.

[0060] In some of the embodiments, in steps S240 and S270:

[0061] First, grouting is performed symmetrically and simultaneously at the arch feet on both sides, then symmetrically and simultaneously at the arch shoulders on both sides, and finally symmetrically and simultaneously at the arch top; the slurry is diluted first and then concentrated, and the slurry is gradually concentrated according to the grouting absorption situation; the grouting pressure is controlled by the one-time pressure boost method.

[0062] Based on the above technical solution, in the embodiment of the present invention, the entire construction method has a clear process and reasonable steps, which not only ensures the construction quality but also improves the construction efficiency. At the same time, by strengthening temporary support and grouting reinforcement and other measures, the safety risks in the construction process are reduced and the life safety of the construction personnel is guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0064] Figure 1 A schematic diagram of the local structure of an embodiment of the tunnel construction method of the present invention;

[0065] Figure 2 A transverse cross-sectional view of an embodiment of a tunnel construction method of the present invention;

[0066] Figure 3 It is a schematic diagram of the overall structure of an embodiment of the tunnel construction method of the present invention;

[0067] Figure 4 A schematic diagram of the local structure of an embodiment of the tunnel construction method of the present invention;

[0068] Figure 5 A transverse cross-sectional view of an embodiment of a tunnel construction method of the present invention;

[0069] Figure 6 A cross-sectional view from the top of a tunnel of an embodiment of a tunnel construction method of the present invention;

[0070] Figure 7 A transverse cross-sectional view of an embodiment of a tunnel construction method of the present invention;

[0071] Figure 8 A cross-sectional view from the top of a tunnel of an embodiment of a tunnel construction method of the present invention;

[0072] Fig. 9A transverse cross-sectional view of an embodiment of a tunnel construction method of the present invention;

[0073] Fig.10 A construction flow chart of an embodiment of a tunnel construction method of the present invention;

[0074] Fig.11 A construction flow chart of step S100 of an embodiment of a tunnel construction method of the present invention;

[0075] Fig.12 A construction flow chart of step S200 of an embodiment of the tunnel construction method of the present invention;

[0076] Fig.13 A construction flow chart of step S300 of an embodiment of the tunnel construction method of the present invention;

[0077] Fig.14 A construction flow chart of step S400 of an embodiment of the tunnel construction method of the present invention;

[0078] Fig.15 This is a construction flow chart of step S500 of an embodiment of the tunnel construction method of the present invention.

[0079] In the figure:

[0080] 100, tunnel; 200, steel base plate; 300, bottom reinforcement; 400, circumferential arch; 500, fixed guide tube; 600, longitudinal I-beam; 700, first batch of grouting pipes; 800, second batch of grouting pipes; 900, first demolition area. DETAILED DESCRIPTION

[0081] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0082] In the description of the present invention, it should be understood that the terms "center", "lateral", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0083] The terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Thus, a feature defined as "first", "second", and "third" may explicitly or implicitly include one or more of the features.

[0084] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0085] Referring to all the accompanying drawings, in an illustrative embodiment of a tunnel 100 construction method of the present invention, the tunnel 100 construction method includes:

[0086] S100, erecting a temporary steel arch frame: erecting a temporary steel arch frame in the tunnel 100. This improves the overall stability and safety of the tunnel 100 during the construction process, and effectively prevents the occurrence of safety accidents such as collapse of the tunnel 100.

[0087] In step S100, steps S110 to S140 are included.

[0088] S110, setting a bottom steel plate;

[0089] In step S110, steps S111 and S112 are specifically included.

[0090] S111, installing a steel bottom plate 200 at the bottom of the tunnel 100 near the walls on both sides;

[0091] The steel bottom plate 200 is a rectangular plate. When installing the steel bottom plate 200 , the length direction of the steel bottom plate 200 is the same as the length direction of the tunnel 100 , and one side of the steel bottom plate 200 in the width direction is attached to the corresponding wall.

[0092] Furthermore, the width of the steel bottom plate 200 is 0.5 meters and the thickness is 2 centimeters. Under this size, the thickness and weight of the steel bottom plate 200 are sufficient to provide a good fixing effect.

[0093] S112, fixing the steel bottom plate 200: inserting the bottom steel bars 300 into the bottom of the tunnel 100, the bottom steel bars 300 being attached to the side of the steel bottom plate 200 away from the corresponding wall.

[0094] The bottom reinforcement bars 300 are arranged at intervals along the length direction of the laid steel bottom plate 200 .

[0095] The bottom steel bar 300 is used to block the steel bottom plate 200 to prevent the steel bottom plate 200 from shifting, thereby ensuring the fixing effect. At the same time, there is no rigid connection between the bottom steel bar 300 and the steel bottom plate 200, which is convenient for installation and removal.

[0096] The bottom steel bar 300 is a steel bar with a diameter of 22 mm and a length of 15 cm. The bottom steel bar 300 with a changed size can provide better support strength.

[0097] S120, installing the annular arch 400;

[0098] S121. Use I20a I-beams to bend according to the curvature of the inner wall of the tunnel 100 to form a circumferential arch 400.

[0099] S122, arranging the annular arches 400 at intervals along the length direction of the tunnel 100.

[0100] In some embodiments, the distance between any two adjacent annular arches 400 is 0.75 meters.

[0101] Furthermore, in sections of the tunnel 100 where cracks, falling blocks or water leakage are serious, the distance between any two adjacent annular arches 400 is set to 0.5 meters.

[0102] S130 , fixing the annular arch frame 400 , and fixing the annular arch frame 400 to the tunnel 100 .

[0103] In step S130, steps S131 to S132 are specifically included.

[0104] S131, inserting a fixed conduit 500 into the inner wall of the tunnel 100, wherein the fixed conduit 500 is located on both sides of the corresponding annular arch 400; the fixed conduit 500 is fixed to the inner wall of the tunnel 100; and the annular arch 400 is connected to the inner wall of the tunnel 100 by using the fixed conduit 500.

[0105] In some embodiments, the tunnel 100 is in an arch shape, or a semicircle, with both ends located on a horizontal line. Taking the dot of the tunnel 100 as a clock dot as an example, the range between 9 o'clock and 10 o'clock and between 2 o'clock and 3 o'clock is defined as the arch foot. The range between 10 o'clock and 11 o'clock and between 1 o'clock and 2 o'clock is the arch spandrel, and 11 o'clock to 1 o'clock is the arch crown. Preferably, 12 o'clock is the arch crown.

[0106] Furthermore, the tunnel 100 also includes a haunch, with a horizontal line passing through the dot of the tunnel 100 as a reference line, and a minimum angle between the line connecting the spandrel and the dot and the reference line of 45° to 75°, preferably 60°. The minimum angle between the line connecting the haunch and the dot and the reference line of 0° to 45°, preferably 30°. The foot of the arch can be located on the reference line or below the reference line.

[0107] In another embodiment, the minimum angle between the line connecting the haunch and the dot and the reference line is 0° to 75°, preferably 60°.

[0108] Further, in S131, each annular arch 400 corresponds to 8 fixed conduits 500. Every two fixed conduits 500 form a group, and four groups of fixed conduits 500 are sequentially arranged along the extension direction of the annular arch 400. The two corresponding fixed conduits 500 in each group are bundled together, so as to fix the annular arch 400 to the tunnel 100.

[0109] Furthermore, four groups of fixed conduits 500 are sequentially arranged at the arch foot, the arch shoulder, the arch shoulder and the arch foot along the extension direction of the annular arch frame 400.

[0110] In some other embodiments, S131 is to connect the fixed conduit 500 to the steel arch frame by welding, or to directly bind the steel arch frame by the fixed conduit 500, or to connect the fixed conduit 500 to the steel arch frame by bonding.

[0111] S132, inserting the two ends of the steel arch frame between the corresponding steel bottom plate 200 and the corresponding side wall of the tunnel 100. This realizes the bottom fixation of the steel arch frame. In addition, the bottom of the steel arch frame and the steel bottom plate 200 are not rigidly connected, which is convenient for installation and disassembly.

[0112] It is worth noting that the order of S132 and S131 is not fixed.

[0113] In some embodiments, the specific step of S130 is to first execute S132 and then execute S120. The specific execution method is that the steel arch frame is placed sideways or horizontally, and the two ends of the steel arch frame are first inserted between the corresponding steel bottom plate 200 and the corresponding side wall of the tunnel 100. Then the steel arch frame is pulled up to make the steel arch frame fit the surrounding wall of the tunnel 100.

[0114] S140, installing the longitudinal I-beam 600, and connecting and fixing the longitudinal I-beam 600 to the annular arch 400;

[0115] In step S140, step S141 is specifically included.

[0116] S141, longitudinal I-beams 600 are installed on the arch top, two arch waists and two arch feet, and the length direction of the longitudinal I-beams 600 is the same as the length direction of the tunnel 100. Each circumferential arch frame 400 is connected to the longitudinal I-beams 600.

[0117] Through the above scheme, in S100, by erecting a temporary steel arch frame, including setting up a bottom steel plate, installing and fixing the annular arch frame 400, and installing a longitudinal I-beam 600 for reinforcement, the overall stability and safety of the tunnel 100 during the construction process are significantly improved, and the occurrence of safety accidents such as the collapse of the tunnel 100 is effectively prevented.

[0118] S200, grouting reinforcement: grouting is performed on the surrounding rock outside the outer wall of the tunnel 100 to reinforce the surrounding area of ​​the tunnel 100.

[0119] S210. Select a grouting pipe: Select a grouting pipe with a length of 6 meters, a diameter of 42 mm, and a wall thickness of 3.5 mm. The end of the grouting pipe used for inserting into the wall is the insertion end, and the end of the grouting pipe used for injecting slurry is the injection end. Multiple grouting holes are opened on the peripheral wall of the grouting pipe, and the shortest distance between the grouting holes and the injection end is 2 meters.

[0120] In some embodiments, the grouting holes are arranged in a plum blossom array or a mesh array on the peripheral wall of the grouting pipe.

[0121] In some embodiments, each grouting pipe is interconnected so that during grouting, cement can automatically enter each grouting pipe under pressure and perform grouting. It is not necessary to connect the grouting pipes to the grouting equipment one by one.

[0122] S220, inserting the first batch of grouting pipes 700 into the inner wall of the tunnel 100: inserting the grouting pipes along the length direction of the tunnel 100 and the circumferential direction of the peripheral wall of the tunnel 100. The distance between any two adjacent grouting pipes is 2.4 meters.

[0123] In some embodiments, step S220 further includes: inserting the first batch of grouting pipes 700 into the wall of the tunnel 100 in a rectangular array.

[0124] Furthermore, the specific steps of step S220 are as follows: 11 rows of grouting pipes are sequentially inserted along the circumferential direction of the peripheral wall of the tunnel 100, and the grouting pipes of each row are arranged at intervals along the length direction of the tunnel 100. Among them, the 6th row of grouting pipes is plugged into the vault and perpendicular to the ground, and the remaining 10 rows of grouting pipes are symmetrically arranged on both sides of the 6th row of grouting pipes in a 50-50 ratio. The first batch of grouting pipes 700 can be inserted into the wall of the tunnel 100 in a rectangular array, ensuring that the first batch of grouting pipes 700 cover a large area on the peripheral wall of the tunnel 100, thereby improving the effect and efficiency of the first grouting.

[0125] S230, prepare slurry: select fast-hardening aluminum sulfate 42.5 cement. The mix ratio is 1:1 to 0.75:1. In this scheme, it is conducive to the rapid consolidation of the slurry and the surrounding rock.

[0126] S240, first grouting, performing first grouting through the first batch of grouting pipes 700;

[0127] First, grouting is performed symmetrically at the arch feet on both sides, then at the arch shoulders on both sides, and finally at the arch top. The grouting is diluted first and then concentrated, and the grouting is gradually concentrated according to the grouting absorption. The grouting pressure control adopts the one-time pressure increase method.

[0128] In step S240, step S241 is included.

[0129] S241, connect the ball valve, pressure gauge, sleeve, quick connector to the injection end of the corresponding grouting pipe, and connect the grouting pressure pipe of the grouting machine. Grouting is performed in the surrounding rock above the tunnel 100 through the grouting machine and the grouting pipe. After the grouting is completed, close the grouting stop valve.

[0130] S250, wait for the first grouting to solidify.

[0131] S260 , inserting a second batch of grouting pipes 800 into the inner wall of the tunnel 100 .

[0132] Furthermore, step S260 is: inserting a second batch of grouting pipes 800 into the wall of the tunnel 100 in a rectangular array.

[0133] In some embodiments, the specific steps of step S260 are: inserting the grouting pipe along the length direction of the tunnel 100 and the circumferential direction of the peripheral wall of the tunnel 100. Among the grouting pipes inserted in the second batch, the distance between any two adjacent grouting pipes is 2.4 meters.

[0134] In some embodiments, step S260 further includes: when inserting the second batch of grouting pipes 800, controlling the spacing between the second batch of inserted grouting pipes and any adjacent first batch of grouting pipes 700 to be the same. That is, the second batch of grouting pipes 800 are inserted into the gaps between the first batch of grouting pipes 700, and it can also be considered that the second batch of grouting pipes 800 and the first batch of grouting pipes 700 are distributed in a plum blossom shape.

[0135] Through the above solution, the second batch of grouting pipes are inserted into the gaps of the first batch of grouting pipes, and the second grouting can fill the gaps missed by the first grouting, ensuring that the grouting pipes fully cover the surrounding wall of the tunnel 100 without missing any area. This layout allows the grouting material to evenly and fully fill the cracks and gaps in the surrounding rock of the tunnel 100, thereby enhancing the integrity and stability of the tunnel 100 structure and improving the effect of grouting reinforcement.

[0136] In step S260, the specific steps of inserting the second batch of grouting pipes 800 are as follows: among the grouting pipes inserted in the rectangular array of the first batch, the four closest first batch grouting pipes are marked as a, b, c, and d. The a, b, c, and d are the four corners of the rectangle. Wherein a and c are diagonal, and b and d are diagonal. The corresponding grouting pipes to be inserted in the second batch are inserted to the midpoint of the diagonal formed by a and c, or inserted to the midpoint of the diagonal formed by b and d.

[0137] Through the above scheme, the insertion position of the second batch of grouting pipes 800 is selected at the midpoint of the corresponding diagonal in the grouting pipes formed by the first batch of rectangular arrays. This layout not only takes into account the symmetry of the tunnel 100 structure, but also fully considers the diffusion law of the grouting material in the surrounding rock. It helps to achieve uniform distribution of grouting materials, reduces the problem of local stress concentration caused by uneven grouting, and thus optimizes the grouting layout. In addition, this method facilitates manual rapid alignment when inserting the grouting pipe, thereby improving work efficiency.

[0138] In some other embodiments, in S260, the distance between the grouting pipes inserted in the second batch and the adjacent grouting pipes inserted in the first batch is 1.2 meters.

[0139] S270, second grouting, the second grouting is performed through the second batch of grouting pipes 800; the steps of the second grouting are the same as the steps S240 of the first grouting.

[0140] S280, wait for the second grouting to solidify.

[0141] S290, grouting effect detection; adopt the drilling coring inspection method, and / or, adopt the micro camera imaging detection.

[0142] Through the above step S200, through the grouting reinforcement step, through two groutings, the cracks and gaps in the surrounding rock of the tunnel 100 can be filled more comprehensively, the integrity of the surrounding rock can be enhanced, and the bearing capacity and waterproof performance of the tunnel 100 can be further improved.

[0143] S300, removal and primary branch reconstruction. Step S300 includes steps S310 to S352.

[0144] S310, dismantling the temporary steel arch frame. Step S310 includes step S311.

[0145] S311. Dismantle 400 circumferential arch frames and 600 longitudinal I-beams; dismantle from the arch crown to the arch shoulders on both sides, then from the arch shoulders to the arch waist, and then from the arch waist to the arch foot. The construction is carried out symmetrically from top to bottom on both sides at the same time.

[0146] Furthermore, in step S311, the steel base plate 200 is also removed.

[0147] In the above steps, the temporary steel arch frame is first dismantled to provide space for the subsequent removal and reconstruction of the primary support. As a temporary support structure during the construction process, the timely dismantling of the temporary steel arch frame helps reduce safety hazards during the construction process and ensure construction safety.

[0148] S320, first demolition by skipping: in the tunnel 100, first demolition areas 900 are marked at intervals along the length direction of the tunnel 100, and the original secondary lining concrete and the original primary support are demolished in the first demolition areas 900.

[0149] The original secondary lining concrete may be understood as the inner wall concrete of the original tunnel 100 .

[0150] Step S320 includes S321 to S324.

[0151] S321. Mark a first demolition area 900 every 6 to 7 meters, and demolish the original secondary lining concrete in the first demolition area 900.

[0152] S322. Use an excavator with a demolition head to perform demolition by using the woodpecker method (which can also be understood as breaking concrete with an impact drill).

[0153] Furthermore, in S312, demolition is performed from the arch crown to the arch shoulders on both sides, then from the arch shoulders to the arch waist, and then from the arch waist to the arch foot, and the construction is performed symmetrically from top to bottom on both sides at the same time.

[0154] S323. The specific steps for dismantling the original support are: dismantle from the arch crown to the arch shoulders on both sides, then from the arch shoulders to the arch waist, and then from the arch waist to the arch foot. The construction is carried out symmetrically from top to bottom on both sides at the same time.

[0155] Among them, the original support structure can be considered as the steel frame support structure when the tunnel 100 is initially constructed.

[0156] S324, the waste is cut by a welder and an excavator and then transported out by a transport vehicle. The waste may also include the annular arch 400 and the longitudinal I-beam 600 removed in step S211.

[0157] In the above step S320, through the first slot-hopping demolition and the second slot-hopping demolition, part of the original support structure can be removed in sections and steps, which helps to more flexibly deal with the geological changes that may be encountered during the excavation of the tunnel 100. The slot-hopping demolition strategy can be adjusted according to the actual situation on site to ensure the stability and safety of the tunnel 100 structure. In the first slot-hopping demolition, the first demolition area 900 is demarcated at intervals along the length direction of the tunnel 100 to ensure the orderly progress of the construction. This method of segmented construction helps to control the construction rhythm and avoid excessive impact on the entire tunnel 100 structure. And by defining a clear demolition area, it is possible to concentrate forces and resources on the demolition operation and reduce construction interference in other undemolished areas. This helps to keep the construction site clean and orderly and improve construction efficiency. Moreover, the slot-hopping demolition method allows construction personnel to flexibly adjust the construction plan according to the actual geological conditions. During the demolition process, if it is found that the geological conditions are not in line with expectations, the subsequent construction plan can be adjusted in time to ensure the safety and stability of the tunnel 100 structure.

[0158] S330, first initial support reconstruction: erecting an initial support steel arch frame in the first demolished area 900, laying a double-layer steel mesh, and filling the first demolished area 900 with shotcrete. For specific steps, please refer to the following steps S331 to S332.

[0159] Step S330 includes S331 to S332.

[0160] S331. Use I20b I-beams as initial support steel arch frames; distribute the initial support steel arch frames at intervals of 0.5 meters along the length direction of the tunnel 100 in the first demolition area 900 after demolition.

[0161] The shape of the initial supporting steel arch can fit the surrounding wall of the first demolition area 900 after the tunnel 100 is demolished.

[0162] Furthermore, in step S331 , the outer peripheral wall of the initial supporting steel arch frame is fitted inside the peripheral wall of the first demolition area 900 .

[0163] S332. Lay double-layer steel mesh on the inner wall of the initial support steel arch frame. Use sprayed concrete to fill the first demolition area of ​​900.

[0164] Furthermore, if the depth of the first demolished area 900 is less than 50 centimeters, sprayed concrete is used for filling.

[0165] The depth of the first demolition area 900 is the minimum or average distance between the outer wall of the first demolition area 900 and the inner wall of the tunnel 100 that has not been demolished.

[0166] It is worth noting that step S330 can be performed simultaneously with step S320, that is, after demolishing a first demolition area 900, the first primary support reconstruction is immediately performed in the area. This can meet the support in the tunnel 100 and avoid the risk of collapse in the tunnel 100. It is preferred to use this method in old or severely damaged tunnels 100.

[0167] Alternatively, step S330 can be performed after step S320 is completely completed. It does not require multiple parties to perform construction at the same time, which is convenient for mobilizing human and material resources and for management.

[0168] In the above step S330, the first initial support reconstruction and the second initial support reconstruction can optimize the support structure and parameters according to the actual geological conditions revealed during the excavation of the tunnel 100 by reconstructing the initial support system, thereby improving the support effect. The new initial support system can better adapt to the deformation and stress changes of the surrounding rock of the tunnel 100, ensuring the long-term stability of the tunnel 100 structure. The slitting removal and initial support reconstruction adopt a segmented construction method, which can reduce the interference with the construction activities of the unremoved section. This construction method helps to maintain the order and efficiency of the construction site, and also helps to reduce the impact of construction activities on the surrounding environment. And through accurate slitting removal and initial support reconstruction plans, the construction cost can be effectively controlled. Reasonably arrange the construction sequence and resource input, reduce unnecessary waste and rework, and thus improve economic benefits. In addition, the alternation of slitting removal and initial support reconstruction helps to achieve the continuity and efficiency of the construction process. Construction personnel can flexibly adjust the construction plan according to the construction progress and on-site conditions to ensure the smooth completion of the construction task.

[0169] In addition, an initial support steel arch frame is erected in the first demolition area 900, and a double-layer steel mesh is laid, which significantly enhances the strength and stability of the support system. This structure can better withstand the deformation and stress changes of the surrounding rock of the tunnel 100, ensuring the long-term safety of the tunnel 100 structure. In addition, the use of sprayed concrete for filling can ensure the close integration of the support system and the surrounding rock of the tunnel 100. Sprayed concrete has good compactness and adhesion, and can fill the gap between the support system and the surrounding rock to improve the support effect. Moreover, the construction speed of sprayed concrete is fast, and the construction of the support system can be completed in a relatively short time. This helps to shorten the construction period and improve construction efficiency. By reconstructing the initial support system, the construction environment can be improved. The new support system can provide better support and protection, and reduce safety hazards and dust pollution during construction.

[0170] S340, second demolition by skipping: in the tunnel 100, the original secondary lining concrete and the original primary support are removed at intervals along the length direction of the tunnel 100.

[0171] Step S340 specifically includes steps S341 to S345.

[0172] S341. Mark a portion of the tunnel 100 excluding the first demolition area 900 as a second demolition area.

[0173] S342. Remove the original secondary lining concrete in the second demolition area.

[0174] S343. Use an excavator with a demolition head to perform trench-hopping demolition using the woodpecker method.

[0175] Furthermore, in S343, demolition is carried out from the arch crown to the arch shoulders on both sides, then from the arch shoulders to the arch waist, and then from the arch waist to the arch foot. The construction is carried out symmetrically from top to bottom on both sides at the same time.

[0176] S344. The specific steps for dismantling the original support are: dismantle from the arch crown to the arch shoulders on both sides, then from the arch shoulders to the arch waist, and then from the arch waist to the arch foot. The construction is carried out symmetrically from top to bottom on both sides at the same time.

[0177] S345. The waste is cut by welders working with excavators and then transported out by transport vehicles.

[0178] In step S340, in the second slot-hopping demolition, the zoning and refinement construction method helps to better control the construction progress and quality. It allows the construction team to accurately handle the remaining areas after the first demolition and initial support reconstruction are completed. By dividing the demolition work into two stages, the mutual influence between different construction stages can be reduced. After the first demolition and initial support reconstruction are completed, the structure of tunnel 100 has been stabilized to a certain extent. When the second slot-hopping demolition is carried out, the impact on the surrounding area will be relatively small. The second slot-hopping demolition area may face different geological conditions from the first demolition area 900. Through zoning construction, the construction team can adjust the construction plan according to actual conditions, better adapt to geological changes, and ensure construction safety and the stability of the tunnel 100 structure.

[0179] S350, second primary support reconstruction: erecting initial support steel arch frame in the second demolition area, laying double-layer steel mesh, and filling the second demolition area with shotcrete.

[0180] Step S350 includes step S351 to step S352.

[0181] S351. In the second demolition area after demolition, initial support steel arch frames are distributed at intervals of 0.5 meters along the length direction of the tunnel 100.

[0182] The shape of the initial supporting steel arch frame can fit the surrounding wall of the second demolition area after the tunnel 100 is demolished.

[0183] Furthermore, in step S351, the outer peripheral wall of the initial supporting steel arch frame is fitted inside the peripheral wall of the second demolition area.

[0184] S352. Lay double-layer steel mesh on the inner wall of the initial support steel arch frame. Use sprayed concrete to fill the second demolition area.

[0185] Furthermore, if the depth of the second demolition area is less than 50 cm, sprayed concrete is used for filling.

[0186] The depth of the second demolition area is the minimum or average distance between the outer wall of the second demolition area and the inner wall after the first primary support reconstruction.

[0187] It is worth noting that step S340 can be performed simultaneously with step S350, that is, after a second demolition area is demolished, the second primary support reconstruction is immediately performed in the area. This can meet the support in the tunnel 100 and avoid the risk of collapse in the tunnel 100. This method is preferably used in old or severely damaged tunnels 100.

[0188] Alternatively, step S340 can be performed after step S350 is completely completed. It does not require multiple parties to perform construction at the same time, which is convenient for mobilizing human and material resources and for management.

[0189] In step S350, an initial support steel arch is erected in the second demolition area, a double-layer steel mesh is laid, and shotcrete is used for filling. This series of operations significantly enhances the overall stability of the structure of the tunnel 100. The new initial support system can better withstand surrounding rock pressure and deformation, ensuring the safety and durability of the tunnel 100 during operation.

[0190] S360, for the 100 sections of the tunnel with falling blocks, collapse and depth greater than 50 cm, three pumping pipes of different lengths are inserted. One is the exhaust pipe and the other two are the pumping pipes. After the shotcrete filling concrete solidifies, pump C20 concrete filling.

[0191] S370. Monitoring points are set at the arch crown, arch shoulder and arch foot at intervals of 6 to 7 meters along the length of tunnel 100.

[0192] Through the above step S300, the dismantling and initial support reconstruction steps not only eliminate possible structural hazards, but also ensure the long-term stability and durability of the tunnel 100 structure by reconstructing the initial support system.

[0193] S400, invert construction. In step S400, it includes invert excavation, laying of invert primary supporting steel arch frame, laying of invert lining steel bars, installation of formwork, pouring of invert concrete, and pouring of invert backfill.

[0194] S410, first invert excavation; planning a plurality of first excavation areas at intervals on the ground along the length direction of the tunnel 100;

[0195] The first excavation area was demolished using the woodpecker method with an excavator.

[0196] Furthermore, S410 also includes that the waste is transferred to a transport vehicle through a blasting machine and an excavator and transported out.

[0197] In some embodiments, step S410 also includes setting up a trestle bridge on the first excavation area for passage.

[0198] The distance between any two adjacent first excavation areas may be 6 meters to 7 meters.

[0199] S420, laying of the initial supporting steel arch frame of the invert for the first time;

[0200] S421, laying the initial supporting steel arch frames of the invert arch at intervals along the length direction of the tunnel 100 in the first excavation area.

[0201] Furthermore, in the first excavation area, the number of the initial supporting steel arch frames of the invert is the same as the number of the initial supporting steel arch frames installed above it and are arranged in a one-to-one correspondence.

[0202] S422, connecting the initial supporting steel arch frame of the invert with the corresponding initial supporting steel arch frame to form a closed loop structure, wherein the connection methods include but are not limited to welding, bolt connection, riveting, etc.

[0203] S430. Lay the arch lining steel bars above the primary supporting steel arch frame in the first excavation area, install the formwork, pour the arch concrete, and pour the arch backfill.

[0204] It is worth noting that step S410 can be performed simultaneously with step S420, that is, after removing a first excavation area, the first invert arch primary support steel arch frame is immediately laid in the area. This can meet the support in the tunnel 100 and avoid the risk of collapse in the tunnel 100. It is preferred to use this method in old or severely damaged tunnels 100.

[0205] Alternatively, step S410 can be performed after step S420 is completely completed. It does not require multiple parties to perform construction at the same time, which is convenient for mobilizing human and material resources and for management.

[0206] S440, second invert excavation; the ground of tunnel 100 except the first excavation area is planned as the second excavation area;

[0207] The second excavation area was demolished using the woodpecker method using an excavator.

[0208] Furthermore, S440 also includes that the waste is transferred to a transport vehicle through a blasting machine and an excavator and transported out.

[0209] In some embodiments, step S440 also includes setting up a trestle bridge on the second excavation area for passage.

[0210] S450, laying of the primary supporting steel arch frame of the invert for the second time;

[0211] S451, laying the primary supporting steel arch frames of the invert arch at intervals along the length direction of the tunnel 100 in the second excavation area.

[0212] Furthermore, in the second excavation area, the number of the initial supporting steel arch frames of the invert arch is the same as the number of the initial supporting steel arch frames installed above it and are arranged in a one-to-one correspondence.

[0213] S452, connecting the initial supporting steel arch frame of the invert arch with the corresponding initial supporting steel arch frame to form a closed loop structure, wherein the connection methods include but are not limited to welding, bolt connection, riveting, etc.

[0214] S460. Lay the arch lining steel bars above the primary supporting steel arch frame in the second excavation area, install the formwork, pour the arch concrete, and pour the arch backfill.

[0215] It is worth noting that step S440 can be performed simultaneously with step S450, that is, after removing a second excavation area, the second laying of the inverted arch primary support steel arch frame is performed in the area immediately. This can meet the support in the tunnel 100 and avoid the risk of collapse in the tunnel 100. It is preferred to use this method in old or severely damaged tunnels 100.

[0216] Alternatively, step S440 can be performed after step S450 is completely completed. It does not require multiple parties to perform construction at the same time, which is convenient for mobilizing human and material resources and for management.

[0217] Through the above step S400, the invert construction step ensures the construction quality of the invert through standardized excavation, laying of primary support steel arch frame, laying of lining steel bars, template installation and concrete pouring, thereby improving the overall bearing capacity and deformation resistance of the tunnel 100.

[0218] S500 , waterproofing and drainage and secondary lining reconstruction; that is, laying waterproofing and drainage on the inner wall of the tunnel 100 and re-casting the inner wall of the tunnel 100 .

[0219] S510, the parts of the grouting pipe and the pumping pipe protruding from the surface of the tunnel 100 are removed and ground flat.

[0220] S520 , affix a waterproof cloth to the inner wall of the tunnel 100 .

[0221] S530, tying a secondary lining steel mesh to the inner peripheral wall of the tunnel 100, and pouring concrete on the steel mesh.

[0222] Specifically, pouring concrete means pouring concrete.

[0223] Through the above step S500, the waterproofing and drainage and secondary lining reconstruction step waterproofs the inner wall of the tunnel 100, and re-casts the secondary lining, performing the final maintenance on the tunnel 100, providing a reliable guarantee for the long-term operation of the tunnel 100.

[0224] In the entire steps S100 to S500, the entire construction method has a clear process and reasonable steps, which not only ensures the construction quality but also improves the construction efficiency. At the same time, by strengthening temporary support and grouting reinforcement measures, the safety risks in the construction process are reduced and the life safety of the construction workers is guaranteed.

[0225] Finally, it should be noted that: the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0226] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A tunnel construction method, characterized in that: include: S100, erect temporary steel arch frame, including: S110, install the bottom steel plate at the bottom of the tunnel near the walls on both sides; S120, installing the circumferential arch frames, and arranging the circumferential arch frames at intervals along the length direction of the tunnel; S130, fixing the annular arch frame, fixing the annular arch frame to the tunnel; S140, install the longitudinal I-beam, and connect and fix the longitudinal I-beam to the annular arch frame; After step S100, step S200 is also included; S200, grouting reinforcement, specifically including: S220, inserting the first batch of grouting pipes into the inner wall of the tunnel; S240, performing the first grouting through the first batch of grouting pipes; S260, inserting a second batch of grouting pipes into the inner wall of the tunnel; S270, performing a second grouting through a second batch of grouting pipes; After step S200, step S300 is also included; S300, demolition and reconstruction of primary support, specifically including: demolition of temporary steel arch frame; demolition of original secondary lining concrete, demolition of original primary support and reconstruction of primary support; After step S300, step S400 is also included; S400, invert construction, including: invert excavation, laying of invert primary support steel arch frame, laying of invert lining steel bars, installation of formwork, pouring of invert concrete, pouring of invert backfill; After step S400, step S500 is also included; S500, waterproofing and drainage and secondary lining reconstruction: laying waterproofing and drainage on the inner wall of the tunnel and re-casting the inner wall of the tunnel.

2. The tunnel construction method according to claim 1, characterized in that: In step S220, the specific steps include: The first batch of grouting tubes were inserted into the tunnel wall in a rectangular array.

3. The tunnel construction method according to claim 2, characterized in that: In step S260, the specific steps include: inserting the second batch of grouting pipes into the wall of the tunnel in a rectangular array, and when inserting the second batch of grouting pipes, controlling the spacing between the inserted second batch of grouting pipes and any adjacent first batch of grouting pipes to be the same.

4. The tunnel construction method according to claim 3, characterized in that: In step S260, the specific steps of inserting the second batch of grouting pipes are as follows: among the grouting pipes inserted in the first batch in a rectangular array, the four closest grouting pipes inserted in the first batch are calibrated as a, b, c, and d; a, b, c, and d are the four corners of the rectangle; a and c are diagonals, and b and d are diagonals; the corresponding grouting pipes to be inserted in the second batch are inserted to the midpoint of the diagonal formed by a and c, or inserted into the midpoint of the diagonal formed by b and d.

5. The tunnel construction method according to claim 1, characterized in that: In step S300, the specific steps include: S310, dismantle the temporary steel arch; S320, first job-hopping removal; S330, first primary branch reconstruction; S340, second job-hopping removal; S350, second primary branch reconstruction.

6. The tunnel construction method according to claim 5, characterized in that: In step S300, S320, the specific steps of the first demolition by skipping are: marking the first demolition area at intervals along the length direction of the tunnel, and removing the original secondary lining concrete and the original primary support in the first demolition area; S330. The specific steps of the first initial support reconstruction are: erecting an initial support steel arch frame in the first demolition area, laying a double-layer steel mesh, and filling the first demolition area with sprayed concrete.

7. The tunnel construction method according to claim 6, characterized in that: In step S300, S340, the specific steps of the second demolition by skipping are: marking a portion of the tunnel excluding the first demolition area as the second demolition area, and removing the original secondary lining concrete in the second demolition area; S350. The specific steps of the second primary support reconstruction are: erecting the initial support steel arch frame in the second demolition area, laying a double-layer steel mesh, and filling the second demolition area with shotcrete.

8. The tunnel construction method according to claim 1, characterized in that: In step S400, it specifically includes: S410, excavating the first invert; planning a plurality of first excavation areas at intervals on the ground along the length direction of the tunnel; and demolishing the first excavation areas; S420, laying of the initial supporting steel arch frame of the invert for the first time; S430, laying the invert lining steel bars above the primary supporting steel arch frame of the invert in the first excavation area, installing the formwork, pouring the invert concrete, and pouring the invert backfill; S440, second invert excavation; the tunnel surface except the first excavation area is planned as the second excavation area; the second excavation area is demolished; S450, laying of the primary supporting steel arch frame of the invert for the second time; S460. Lay the arch lining steel bars above the primary supporting steel arch frame in the second excavation area, install the formwork, pour the arch concrete, and pour the arch backfill.

9. The tunnel construction method according to claim 8, characterized in that: In step S400: The specific steps of S420 include: laying the inverted arch primary support steel arch frame at intervals in the first excavation area along the length direction of the tunnel; connecting the inverted arch primary support steel arch frame with the corresponding initial support steel arch frame to form a closed loop structure; The specific steps of S450 include: laying the initial supporting steel arch frames of the inverted arch at intervals along the length direction of the tunnel in the second excavation area; and connecting the initial supporting steel arch frames of the inverted arch with the corresponding initial supporting steel arch frames to form a closed-loop structure.

10. The tunnel construction method according to claim 1, characterized in that: In steps S240 and S270: First, grouting is performed symmetrically and simultaneously at the arch feet on both sides, then symmetrically and simultaneously at the arch shoulders on both sides, and finally symmetrically and simultaneously at the arch top; the slurry is diluted first and then concentrated, and the slurry is gradually concentrated according to the grouting absorption situation; the grouting pressure is controlled by the one-time pressure boost method.

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