Rapid conversion construction method for arch cover method underground excavated subway main body elevated air passing channel

Abstract

The invention discloses a rapid conversion construction method for an arch cover method underground excavated subway main body elevated air passage, and belongs to the technical field of subway construction. The method comprises the following steps that excavation is stopped when a left line of a main body is excavated to the position 3 m in front of an air duct, and a left pilot tunnel face is closed; a left pilot tunnel procedure switching channel is elevated one by one through a first portal frame to enter an air duct, C25 concrete is sprayed to the arch crown and the side wall of the elevated section for sealing, and an outer layer elevated section support is formed; a second portal steel frame is erected on the small mileage side of a main body of the left pilot tunnel, then a plurality of air duct grating steel frames perpendicular to the first portal steel frame are erected on the inner side of the first portal steel frame of the left pilot tunnel one by one, and C25 concrete is sprayed; holing excavation is carried out in the left pilot tunnel in the air duct end point direction, excavation is stopped when excavation is carried out to the end in the air duct end point direction, and a tunnel face is closed; holing excavation is conducted in the left pilot tunnel in the starting point direction of the air duct, excavation is stopped when the air duct is excavated to the position 5 m away from the right line of the main body, three air duct grating steel frames are erected in parallel, and the tunnel face is closed.

Description

Technical Field

[0001] The invention relates to a construction method for quickly converting a raised air duct through a concealed excavation subway body using an arch cover method, and belongs to the technical field of subway construction. Background Art

[0002] In underground subway stations or large-section sections constructed using the arch-cover method, elevated load transfer occurs at the junctions between the main structure and the air ducts, and between the main structure and the entrances and exits. This junction presents a complex load-bearing system, with concentrated stress in the surrounding rock, posing high construction risks and significant challenges. Therefore, load transfer areas are a weak link in arch-cover construction.

[0003] The large-section parking line in the Shanwu section of Qingdao Metro Line 8 features a construction inclined shaft and a construction vertical shaft. The main section is located directly beneath Shandong Road in Shinan District, Qingdao City, in a bustling area near buildings and numerous underground pipelines. Construction work is prone to damaging surrounding buildings and pipelines. Conventional construction methods involve using a horizontal tunnel in the vertical shaft to access the large-section main section. The horizontal tunnel is excavated using the CRD method, and the main structure is then excavated from the horizontal tunnel to either side. The support system at the transition point utilizes intermediate partition walls and temporary inverts. Because vertical shaft construction is less efficient than inclined shaft construction, and the use of intermediate partition walls and temporary inverts as a support system requires significant temporary construction and demolition work, blasting significantly disturbs the surrounding rock. Multiple blasts within a confined area impacting the intermediate partition wall can easily crack and damage the primary support structure of the air duct, posing a safety hazard. Therefore, consideration is being given to using an inclined shaft working face to excavate the entire main section, with the main section elevated above the air duct before continuing with the main section excavation. However, the construction of the main elevated air duct requires the demolition of multiple tunnel doors. The force conversion system of the guide tunnel group is relatively complex, with high risks and major safety hazards. In addition, conventional construction methods have low construction efficiency. Summary of the Invention

[0004] In response to the above-mentioned problems existing in the prior art, the present invention provides a rapid conversion construction method for the elevated air duct of a subway main body using the arch cover method, which can effectively solve the problems of low construction efficiency and great safety hazards of conventional construction methods when the main body is elevated through the air duct.

[0005] The present invention is achieved through the following technical solution: a method for rapid conversion of a subway main body elevated through an air duct by an arch cover method, characterized in that: the left line of the main body is first constructed, with the left and right lines staggered by no less than 15m; when the left line of the main body reaches the air duct position, it is elevated through the air duct, and then the remaining part of the air duct is excavated. The elevated section is elevated one by one using a first portal steel frame to enter the air duct, and the air duct structure is supported by a grid steel frame. Specifically, the method comprises the following steps: (1) Excavation of the main left line to the air duct: The main left pilot tunnel is excavated and initial support is provided in time. Excavation of the left pilot tunnel is stopped 3m in front of the air duct, and then the left pilot tunnel face is closed; (2) With good support, the initial support of the tunnel face at the process conversion channel of the left pilot tunnel is removed and excavation is carried out in the direction of the air duct. During excavation, the first portal steel frame is used to lift up the tunnel into the air duct one by one. The first portal steel frame is supported on the rock layer, and the arch and side walls of the lifting section are sealed with C25 concrete to form the outer lifting section support. After the lifting construction reaches the long mileage end of the air duct, three first portal steel frames are connected to close the tunnel face and complete the construction of the outer lifting section; (3) A second portal steel frame is erected at the small mileage side of the main body of the left guide tunnel, and then several air duct grille steel frames perpendicular to the first portal steel frame are erected one by one on the inner side of the first portal steel frame of the left guide tunnel. One side of the air duct grille steel frame is erected on the second portal steel frame, and the other side is placed on the bottom. After the air duct grille steel frame is erected, C25 concrete is sprayed. After the initial support is completed, the outer arch replacement force conversion process is completed; (4) Carry out excavation in the left pilot tunnel in the direction of the air duct end point: break down the first portal steel frame side wall of the elevated section within the range of the air duct end point, excavate the remaining air duct, and promptly implement the initial support of the air duct. When the excavation reaches the end point of the air duct, stop excavation and close the tunnel face; (5) Carry out excavation in the left guide tunnel in the direction of the air duct starting point: construct advance support of the horse head gate from the process conversion channel to the direction of the air duct starting point, remove the initial support of the first portal steel frame side wall of the elevated section on the side of the air duct starting point at the process conversion channel, excavate the remaining part of the air duct in the direction of the air duct starting point, stop excavation of the air duct to 5m outside the right line of the main body, and erect three air duct grid steel frames in parallel to close the heading face.

[0006] Furthermore, in step (2), after the initial support of the face at the process conversion channel is broken, three first portal steel frames are erected at the horse head gate.

[0007] Furthermore, in step (3), when erecting the air duct grille steel frame, three of the air duct grille steel frames are erected on each of the left and right sides.

[0008] Furthermore, in step (4), before breaking down the first portal steel frame side wall of the elevated section within the direction of the air duct end point, a small advance duct is first set outside the air duct excavation outline and grouting reinforcement is performed.

[0009] Furthermore, the arrangement spacing of the first portal steel frame is 0.75m.

[0010] Furthermore, in step (5), after the initial support of the side wall of the first portal steel frame of the elevated section on the side of the air duct starting point at the process conversion channel is removed, the air duct grille steel frame is promptly erected, and the air duct grille steel frame is firmly connected to the I-beam of the first portal steel frame that has been cut off through pre-bent steel bars; and an expansion shell anchor rod is driven on the top of the air duct grille steel frame.

[0011] Furthermore, after the excavation in the direction of the air duct terminal is completed, the main left guide tunnel will be opened and excavated in the directions of large mileage and small mileage.

[0012] Furthermore, after the excavation in the starting direction of the air duct is completed, the holes and excavation in the long and short mileage directions of the right line of the main body will be carried out.

[0013] Furthermore, when drilling and excavating in the long mileage direction of the main left guide tunnel and the main right line, a temporary portal steel frame must be erected behind the closed heading face to support the upper air duct grille steel frame, and advance support must be set up on top. Then, the initial support of the heading face within the range of the temporary portal steel frame must be removed, and the main grille steel frame must be erected in time. It must be ensured that the air duct grille steel frame is firmly connected to the main grille steel frame. Multiple main grille steel frames must be connected at the opening for initial support to complete the force conversion of the opening before continuing with the tunnel excavation.

[0014] The beneficial effects of the present invention are as follows: the present invention adopts the construction method of raising the main body through the air duct, and the air duct enters the main body again. It can be expanded from a single working surface to multiple working surfaces with the gradual transformation of the force system, so as to achieve the effect of synchronous construction, with high construction efficiency, which can greatly speed up the construction progress and shorten the construction period; the present invention adopts a portal steel frame as the support of the raised section, the support system is simplified, the support is reliable, and the construction efficiency is high; the present invention utilizes the portal steel frame according to the construction sequence, which can smoothly complete the inner and outer layer force conversion: by first constructing the portal steel frame at the raised part, the portal steel frame is placed on the hard rock layer, the raised support bears the arch surrounding rock load, and the whole section is excavated After completion, an inner layer of grille support perpendicular to the direction of the portal steel frame is applied to complete the outer layer arch replacement force conversion. A temporary portal steel frame is constructed behind the closed face and an advance support is set up on the top. The temporary portal steel frame and the upper air duct grille form an effective support. Then the initial support of the face within the range of the temporary portal steel frame is removed, and multiple grid initial supports are applied to complete the inner layer opening force conversion. The construction method of the present invention reduces the amount of temporary engineering construction and demolition work, simplifies the excavation steps, improves work efficiency, and at the same time reduces the number of disturbances to the surrounding rock caused by blasting, eliminating the safety hazards caused by multiple blasting impacts in a narrow range that cause the initial support structure of the air duct to be torn and damaged by the adjacent wall. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a construction flow chart of the present invention; Figure 2 This is a schematic diagram of the left line of the main body excavated to the air duct in the present invention; Figure 3 This is a schematic diagram of the elevated outer door frame of the air duct structure of the present invention; Figure 4 It is a schematic diagram of the inner grille support of the air duct structure in the present invention; Figure 5 It is a schematic diagram of the excavation of the hole in the direction of the end point of the air duct in the present invention; Figure 6 It is a schematic diagram of the opening and excavation in the large mileage and small mileage directions of the left line of the main body in the present invention; Figure 7 It is a schematic diagram of the excavation of the hole in the starting direction of the air duct in the present invention; Figure 8 This is a schematic diagram of the excavation of the main body right line in the direction of large mileage and small mileage in the present invention; Figure 9 It is a schematic diagram of the transition portion between the main body and the air duct in the present invention; In the figure, 1, the first portal steel frame, 2, the second portal steel frame, 3, the air duct grille steel frame, 4, the temporary portal steel frame c, 5, the main grille steel frame, 6, the temporary portal steel frame a, 7, the temporary portal steel frame b, 8, the third portal steel frame, 9, the fourth portal steel frame. DETAILED DESCRIPTION

[0016] The present invention will be further described below by way of non-limiting embodiments with reference to the accompanying drawings: The present invention will be described below by taking the large-section parking line of the Shanwu section of Qingdao Metro Line 8 as an example. It adopts a construction method in which the entire main project is excavated from the inclined shaft working face, and the main body is lifted up to pass through the air duct before continuing with the main body excavation. When the main line of the main body is excavated, the left line of the main body is constructed first, and the staggered distance between the left and right lines is not less than 15m. When the left line of the main body is constructed to the position of the air duct, it is lifted up to pass through the air duct, and then the remaining part of the air duct is excavated. After the excavation of the air duct is completed, the main body excavation can continue. During the lifting construction, the lifting section adopts the first portal steel frame to lift up one by one to enter the air duct, and the air duct structure is supported by a grid steel frame.

[0017] The construction process is as attached Figure 1 shown.

[0018] As attached Figure 2-Figure 9 As shown, the specific construction steps include the following steps: (1) Excavation of the left line of the main body to the air duct Excavate the main line and implement initial support in a timely manner. Start with the left pilot tunnel, with a staggered distance of at least 15m between the left and right pilot tunnels. Stop excavation 3m before the air duct and seal the left pilot tunnel face.

[0019] (2) The outer door frame of the air duct structure is raised In the left pilot tunnel, advance support was installed above the first portal steel frame of the process transfer channel. The initial support of the tunnel face within the scope of the first portal steel frame was then removed and excavation began in the direction of the air duct. Three first portal steel frames (1) were erected at the horse head gate. The first portal steel frames (1) were then raised one by one into the air duct. The first portal steel frames (1) were arranged at a spacing of 0.75m. The tunnel face was closed when excavation reached the high mileage end. The raised section was 7.8m wide. 3.5m long hollow grouting anchors were driven in advance at the arch position. The arch and side walls were sealed with 300mm thick sprayed C25 concrete. After the raised construction reached the high mileage end of the air duct, three first portal steel frames (1) were erected, the tunnel face was closed, and the outer portal frame was raised.

[0020] (3) Inner grille support of air duct structure A second portal steel frame 2 was erected on the lower mileage side of the main structure of the left pilot tunnel. Several air duct grille steel frames 3 were then erected perpendicular to the first portal steel frame 1, one after another, inside the left pilot tunnel. The air duct grille steel frames 3 were arranged at 1m intervals, with three frames on each side. One side of the air duct grille steel frame 3 rested on the second portal steel frame 2, while the other side rested on the bottom. After the air duct grille steel frames 3 were erected, C25 concrete was sprayed to a thickness of 300mm. After the initial support was completed, the outer arch replacement and force conversion process was completed.

[0021] (4) Excavation at the end of the air duct In the left guide tunnel, towards the end of the duct, a small advance duct is set outside the duct excavation outline and grouting reinforcement is carried out. The first portal steel frame side wall of the elevated section within the direction of the duct end is removed, the remaining duct is excavated, and initial support for the duct is carried out in time. When excavation reaches the end of the duct end, excavation is stopped and the heading face is closed.

[0022] (5) Excavation at the starting point of the air duct In the left pilot tunnel, advance support with horse-head gates was installed from the process transfer channel toward the air duct starting point. The primary support for the side wall of the first portal steel frame, located at the elevated section of the process transfer channel and facing the air duct starting point, was removed. The remaining portion of the air duct toward the air duct starting point was excavated, and the air duct grille steel frame was promptly erected. The grille steel frame was securely connected to the I-beam of the removed first portal steel frame using pre-bent steel bars. Two φ32 expansion shell anchors, 4m long, were driven into the top of each grille steel frame. Excavation was stopped 5m beyond the right line of the main body, and three grille steel frames were erected in parallel to seal the tunnel face.

[0023] (6) Opening and excavating holes in the left lane of the main body in the direction of long mileage and short mileage After the air duct construction within the left pilot tunnel is completed and the end face is sealed (after excavation is completed towards the end of the air duct), a temporary portal steel frame C4 is erected at the large mileage end to support the primary support structure of the air duct's inner layer. Advance support is then installed toward the horse head gate at the large mileage end. The primary support grid at the large mileage end of the air duct is then removed, and the main grid steel frame 5 is promptly erected to ensure a secure connection between the air duct grid steel frame and the main grid steel frame. Five main grid steel frames are then installed at the opening to ensure the safety of the portal under concentrated force. After the five main grid steel frames are installed, excavation of the main left pilot tunnel continues, and initial support is promptly implemented.

[0024] On the small mileage side of the main body, temporary portal steel frames a6 and b7 are respectively erected to support the upper air duct grille steel frame. First, the remaining surrounding rock on the left line of the section is excavated, the initial support at the opening is removed, and the third portal steel frame 8 is erected in time to ensure that the air duct grille steel frame is firmly connected to the third portal steel frame, and the remaining surrounding rock on the left line is continued to be excavated forward.

[0025] (7) Opening and excavating holes in the right lane of the main body in the direction of long and short mileage Set up advance support toward the main gate at the large mileage section, erecting a temporary portal steel frame to support the primary support structure within the air duct. First, remove the primary support at the right pilot tunnel opening and promptly erect the main grid steel frame. Connect the duct grid steel frame to the main grid steel frame with "L"-shaped steel bars to ensure a secure connection. Five main grid steel frames will be connected at the opening. Continue excavating the main right pilot tunnel in the section, promptly implementing initial support. Note that the right pilot tunnel must be staggered at least 15m from the left pilot tunnel.

[0026] After the construction in the long-distance direction exceeds 15m, the small-distance tunnel gate (same as the long-distance direction) is broken, the force system conversion at the tunnel gate is completed, and finally the right line of the main body is penetrated, completing the entire construction of the main body and the air duct elevation conversion.

[0027] The other parts of this embodiment are all existing technologies and will not be described in detail here.

Claims

1. A construction method for rapid conversion of underground excavation of subway main body elevated air duct by arch cover method, characterized by: First, construct the left line of the main structure, with the left and right lines staggered at no less than 15m. When the left line of the main structure reaches the air duct position, it is elevated to pass through the air duct, and then the remaining part of the air duct is excavated. The elevated section uses the first portal steel frame to be elevated one by one to enter the air duct. The air duct structure is supported by a grid steel frame. The specific steps include the following: (1) Excavation of the main left line to the air duct: The main left pilot tunnel is excavated and initial support is provided in time. Excavation of the left pilot tunnel is stopped 3m in front of the air duct, and then the left pilot tunnel face is closed; (2) With good support, the initial support of the tunnel face at the process conversion channel of the left pilot tunnel is removed and excavation is carried out in the direction of the air duct. During excavation, the first portal steel frame is used to lift up the tunnel into the air duct one by one. The first portal steel frame is supported on the rock layer, and the arch and side walls of the lifting section are sealed with C25 concrete to form the outer lifting section support. After the lifting construction reaches the long mileage end of the air duct, three first portal steel frames are connected to close the tunnel face and complete the construction of the outer lifting section; (3) A second portal steel frame is erected at the small mileage side of the main body of the left guide tunnel, and then several air duct grille steel frames perpendicular to the first portal steel frame are erected one by one on the inner side of the first portal steel frame of the left guide tunnel. One side of the air duct grille steel frame is erected on the second portal steel frame, and the other side is placed on the bottom. After the air duct grille steel frame is erected, C25 concrete is sprayed. After the initial support is completed, the outer arch replacement force conversion process is completed; (4) Carry out excavation in the left pilot tunnel in the direction of the air duct end point: break down the first portal steel frame side wall of the elevated section within the range of the air duct end point, excavate the remaining air duct, and promptly implement the initial support of the air duct. When the excavation reaches the end point of the air duct, stop excavation and close the tunnel face; (5) Carry out excavation in the left guide tunnel in the direction of the air duct starting point: construct advance support of the horse head gate from the process conversion channel to the direction of the air duct starting point, remove the initial support of the first portal steel frame side wall of the elevated section on the side of the air duct starting point at the process conversion channel, excavate the remaining part of the air duct in the direction of the air duct starting point, stop excavation of the air duct to 5m outside the right line of the main body, and erect three air duct grid steel frames in parallel to close the heading face.

2. The rapid conversion construction method for elevated air ducts in underground subway excavation using the arch cover method according to claim 1 is characterized by: In step (2), after the initial support of the face at the process conversion channel is removed, three first portal steel frames are erected at the horse head gate.

3. The rapid conversion construction method for elevated air ducts in underground subway excavation using the arch cover method according to claim 1 is characterized by: In step (3), when erecting the air duct grille steel frame, three of the air duct grille steel frames are erected on each of the left and right sides.

4. The rapid conversion construction method for elevated air ducts in underground subway excavation using the arch cover method according to claim 1 is characterized by: In step (4), before breaking down the first portal steel frame side wall of the elevated section within the direction of the air duct end point, a small advance duct is first set outside the air duct excavation outline and grouting reinforcement is performed.

5. The rapid conversion construction method for elevated air ducts in underground subway excavation using the arch cover method according to claim 1 is characterized by: The arrangement spacing of the first portal steel frame is 0.75m.

6. The rapid conversion construction method for elevated air ducts in underground subway excavation using the arch cover method according to claim 1, 2, 3, 4, or 5 is characterized by: In step (5), after the initial support of the side wall of the first portal steel frame of the elevated section on the side of the air duct starting point at the process conversion channel is removed, the air duct grille steel frame is promptly erected, and the air duct grille steel frame is firmly connected to the I-beam of the first portal steel frame that has been cut off through pre-bent steel bars; an expansion shell anchor rod is driven on the top of the air duct grille steel frame.

7. The rapid conversion construction method for elevated air ducts in underground subway excavation using the arch cover method according to claim 1 is characterized by: After the excavation at the end of the air duct is completed, the main left guide tunnel will be opened and excavated in the directions of large and small mileages.

8. The rapid conversion construction method for elevated air ducts in underground subway excavation using the arch cover method according to claim 1 is characterized by: Starting point of air duct After the directional excavation is completed, the holes and excavation in the large and small mileage directions of the right line of the main body will be carried out.

9. The rapid conversion construction method for elevated air ducts in underground subway excavation using the arch cover method according to claim 7 or 8 is characterized by: When drilling and excavating in the long mileage direction of the main left pilot tunnel and the main right line, a temporary portal steel frame must be erected behind the closed heading face to support the upper air duct grille steel frame, and advance support must be set up on top. Then, the initial support of the heading face within the range of the temporary portal steel frame must be removed, and the main grille steel frame must be erected in time. Ensure that the air duct grille steel frame is firmly connected to the main grille steel frame, and set up multiple main grille steel frames at the opening for initial support to complete the force conversion of the opening before continuing with the tunnel excavation.

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