A construction method for opening a connecting passage in an existing shield tunnel

Abstract

The present invention discloses a method for constructing the opening of an existing shield tunnel communication channel, which is as follows: first, a segment support reinforcement device is used to complete the support reinforcement of the segment that does not occupy the road in the opening area and the influence range, and after the advance system grouting treatment is applied to achieve the expected effect, a three-guide tunnel three-step construction method is adopted to carry out the segment opening construction: first, a middle guide tunnel is excavated, and the middle guide tunnel interface ring beam and columns and temporary steel support are applied; then, a left guide tunnel is constructed and the left ring beam is closed; finally, a right guide tunnel is constructed and the right ring beam is closed, and the full-closed construction of the ring beam in the opening area is completed at this time; after the ring beam is closed and reaches the design strength, the temporary support is removed. The method of the present invention can safely and quickly complete the construction and processing of the evacuation channel and the entrance and exit segment opening of the existing shield tunnel, with fast construction progress, small structural deformation, guaranteed safety and quality, and effectively shortened the processing period, ensuring the smooth realization of the established goals of the construction unit, and significant social and economic benefits.

Description

Technical Field

[0001] The invention belongs to the technical field of shield tunnel access channel opening construction reinforcement equipment, and relates to an existing shield tunnel communication channel opening construction method. Background Art

[0002] Currently, due to rapid urban development and rapidly increasing social demand, the construction of urban rail transit inevitably requires additional stations to meet the rapidly growing traffic demand. The station's shield tunnel section utilizes a construction technique where a small shield tunnel is first passed through, followed by a larger shield tunnel for excavation. Since the shield tunnel's track top structure, platform slab, and track have already been constructed, the conditions on site are no longer available to construct segment openings, evacuation routes, and entrance and exit passages as originally planned, including the erection of full-section temporary steel supports. To ensure the subway's hot slip targets are achieved as planned, the temporary support opening plan must be adjusted to avoid the track area, allowing for off-track construction and minimizing impacts on the hot slip. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a construction method for opening a connecting passage in an existing shield tunnel, so as to solve the technical problems existing in the prior art.

[0004] The technical solution adopted by the present invention is: a method for constructing the opening of an existing shield tunnel connecting channel, the method being: first, a segment support reinforcement device is used to complete the support reinforcement of the segment that does not occupy the road in the opening area and the affected range, and after the advance system grouting treatment is performed to achieve the expected effect, a three-guide tunnel three-step construction method is adopted to carry out the segment opening construction: first, a middle guide tunnel is excavated, and the middle guide tunnel interface ring beam and columns, and temporary steel supports are constructed; then the left guide tunnel is constructed and the left ring beam is closed; finally, the right guide tunnel is constructed and the right ring beam is closed. At this time, the full closure construction of the ring beam in the opening area is completed, and the temporary support is removed after the ring beam is closed and reaches the design strength.

[0005] A method for constructing an opening for a connecting passage in an existing shield tunnel, the specific steps of the method are as follows:

[0006] (1) Construction of temporary beams between the cross beams of the track top structure: using a buckle bracket, 100×100mm longitudinal square timber is set under the top formwork, and φ48 steel pipe with a wall thickness of 3.5mm is set under the square timber. The side formwork system uses 18mm thick bamboo plywood, the secondary keel is a wooden square with a spacing of 250mm, the cross-section of the square timber is 100×100mm, the main keel is a double-jointed φ48 steel pipe with a wall thickness of 3.5mm, and the bracket horizontal spacing is 600 / 450mm×longitudinal 500mm;

[0007] (2) Construction of double-row steel column support system: The construction process is as follows: measurement and setting out → roughening of pipe segments → embedding of steel bars on pipe segments → installation of bottom longitudinal beam steel bars and pre-embedding of supporting steel plates → installation of formwork brackets → pouring of concrete → removal of formwork and maintenance → setting up of operating platform → installation of steel supports → installation of steel wedges → installation of steel troughs for tightening pipe segments → epoxy material filling;

[0008] (3) Systematic grouting of the opening area and its affected area: including grouting behind the segment wall, grouting between the left and right lines, and grouting of the segment opening and affected area. The grouting sequence is: grouting behind the segment wall → grouting of the segment opening and affected area → grouting between the left and right lines;

[0009] (4) Segment opening construction: The opening is opened from the inside of the shield tunnel toward the entrance and exit. The opening size is 8.1m (width) × 4.3m (height). The three-pilot tunnel and three-step construction method is adopted: first, the middle pilot tunnel is excavated, and the middle pilot tunnel interface ring beam and columns are constructed; then the left pilot tunnel is constructed and the left ring beam is closed; finally, the right pilot tunnel is constructed and the right ring beam is closed. At this time, the ring beam in the opening area is fully closed; after the ring beam is closed and reaches the design strength, the temporary support is removed. During the segment opening construction process, strengthen monitoring work and provide timely feedback to guide on-site construction.

[0010] The construction method in step (2) includes the following specific steps:

[0011] 2.1. Measurement and staking out: Measure the positions of temporary support bottom beams and temporary support columns in the segments according to the design drawings and actual site conditions;

[0012] 2.2. Chiseling: The contact surface between the cast-in-place structure and the segment structure is chiseled to form an artificial rough surface with a concave and convex area of ​​not less than 4mm. The contact surface between the new and old concrete is clean and dry.

[0013] 2.3. Planting reinforcement: Plant reinforcement according to the point, and try to avoid the existing segment structure reinforcement. The planting depth of reinforcement with a diameter less than 25mm is 24d1, where d1 represents the diameter of the reinforcement. If there is a sleeve in the segment within the column range, use the 18mm diameter steel bar end to thread and connect it to the sleeve;

[0014] 2.4. Installation of reinforcement for the supporting bottom longitudinal beam: Before tying the reinforcement, a scaffolding platform is set up. The main reinforcement for the temporary supporting bottom beam is 13 C20 steel bars. There is a pre-buried sleeve within the bottom beam, and C18 steel bars are used to connect the sleeve. The length of the bent anchor anchored in the bottom beam is 15d2, d2 represents the diameter of the C18 steel bar. C10 steel bars are used for embedding reinforcement on the pipe segments, 4 in each row, with an embedding depth of 24d3, d3 represents the diameter of the C10 steel bar. The spacing between each row is adjusted according to the actual situation on site. A8 steel bars are used for tensioning, with a spacing of 300mm. After the bottom beam reinforcement is tied, anchor plate A is embedded, with the center position of the anchor plate corresponding to the center of the rail top air duct crossbeam. Anchor plate B is embedded in the rail top air duct crossbeam with an embedding depth of 300mm.

[0015] 2.5. Formwork: The bottom beam support is made of steel pipe with a horizontal spacing of 500mm, a vertical spacing of 900mm, and a step distance of 1m. The support pedals are arranged and fixed on the upper row of horizontal bars. The side formwork is 1.5cm thick wooden formwork, with 50×100mm square timbers at a spacing of 20cm. There are double rows of steel pipes in the horizontal direction. The screw rods are mechanically connected to the pipe segments and the steel bars are welded. The steel pipe top support reinforcement and the screw rod reinforcement are staggered.

[0016] 2.6. Concrete pouring: Concrete is pumped by sky pump, and manually transported to the opening by wheelbarrow, poured into the silo by chute, and compacted by vibrating rod;

[0017] 2.7. Concrete formwork removal and curing: 1) Pay attention to safe construction when removing the formwork to prevent the formwork from falling and injuring people; 2) After the concrete is removed from the formwork, arrange for a dedicated person to use watering to maintain curing. According to the temperature and weather conditions, timely watering should be carried out to ensure the surface moisture of the concrete, and relevant records should be kept;

[0018] 2.8. Installation of Steel Columns: Two rows of steel columns are set up within the opening. The steel columns on the side close to the dark-excavated tunnel are assembled with double-jointed I40 I-beams, totaling 10 columns. The I-beam columns on the platform slab are 4220mm long and are assembled in 4 sections, each 1m long, connected with bolts and reinforced by welding. Expansion screws are driven into the rail top structure on site, and a hoist is used to assist in manual installation. Steel wedges are installed above the rail top air duct beam to connect with the pipe segments. The steel columns on the side close to the track area are assembled with double-jointed 22b I-beams, totaling 6 columns. The double-jointed 22b I-beam columns on the platform slab are 3620mm long and assembled in 2 sections. The I-beams are welded with 320×320mm T20mm steel plates at the bottom and top of the columns. The top of the section above the air duct beam (1.265m to 1.33m high) is beveled and is installed manually.

[0019] 2.9. Installation of steel wedges and segment tensioning channel steel: The steel wedges are made of double-jointed I25b I-beams with a center spacing of 1.5m. Each steel wedge is tightly connected to the segment and crossbeam using epoxy resin glue. Two C22 steel bars are welded together longitudinally. The segment tensioning channel steel 22b uses M16 and is connected to the segment through a reserved sleeve.

[0020] 2.10. Epoxy material filling: The contact surface between the bottom and top of the steel support and the concrete is sealed with central structural sealant around the periphery, and filled tightly with high-permeability reinforced modified epoxy grouting liquid.

[0021] When sealing the joints with sealant, be sure to reserve small holes for venting at high locations and holes for grouting at low locations. Use a dual-fluid automatic chemical grouting pump for grouting. When grouting, stop grouting when thick slurry flows out of the small holes for venting at high locations, and continue to use sealant to seal the venting holes and grouting holes.

[0022] The construction method in step (3) includes the following specific steps:

[0023] 3.1. Backfill grouting behind the segment wall: Secondary grouting behind the segment includes 14 rings, 4 in front and 4 behind the opening, with a grouting pressure not exceeding 0.3 MPa. Use 1:1 cement slurry for grouting. After reaching the designed grouting pressure, maintain it for 3-4 minutes before stopping grouting. Do not force or blindly grout the segment. Strengthen monitoring of the segment during the grouting process.

[0024] Secondary grouting is carried out behind the segments in the open ring and deformation zone. The grouting distribution is as follows: top section A7, sections A1 and A6 adjacent to the top section A7, sections A2 and A5 connecting sections A1 and A6, and sections A3 and A4 connecting sections A2 and A5. Grouting holes A1, A6, A2, and A5 are arranged in the central and southern parts of sections A1, A6, A2, and A5, respectively. Grouting pipes with valves are inserted into the secondary grouting holes. The grouting sequence is: A2-A5-A1-A6 symmetrical grouting. A3 and A4 are not grouted due to the influence of the track and backfill. A7 is the top pressure relief vent.

[0025] 3.2. Grouting of Segment Openings and Impact Areas: Advance Φ42 small guide tube supports are installed at the segment openings, with a spacing of 0.4m and a length of 5m. Seven rows of grouting holes are set up within the segment opening ring for full-section systematic grouting. The system grouting holes are 7 to 9m deep, and Φ42 steel flower tubes are inserted into the holes. After grouting, the steel flower tubes are not removed as a safety reserve. Simultaneously, 22 grouting holes are arranged in adjacent rings, with a drilling depth of 4m. After positioning on the segment, the holes are opened with a water-grinding drill and then drilled with an air drill. Grouting is carried out from the outside to the inside, with three holes skipped at a time to prevent grouting. A 1:1 cement single-liquid slurry is used, with a designed grouting pressure of 0.8 to 1.5MPa. This pressure is dynamically adjusted during construction based on monitoring conditions.

[0026] 3.3. Grouting between the left and right lines: Grouting reinforcement is carried out for the soil between the left and right lines. On the basis of grouting holes (hole depth 4m) arranged by utilizing the original grouting holes of the pipe segments, a row of anchor pipes (Φ42 steel flower pipes) are added on the upper and lower sides for grouting reinforcement support. The anchor pipes are Φ42 steel flower pipes with an outward inclination angle of 45 degrees, a hole depth of 4m, and a spacing of 3m.

[0027] A total of 33 grouting holes are arranged between the left and right lines, including 13 secondary grouting holes and 20 new holes;

[0028] A water-grinding drill is used to drill through the pipe segments, and a pneumatic drill is used to form holes. Φ42 steel flower pipes are inserted into the grouting holes for grouting. A 1:1 cement single-liquid slurry is used, and the designed grouting pressure is 0.8~1.5MPa. During actual construction, it is dynamically adjusted according to the monitoring conditions.

[0029] The segment opening construction method in step (4) includes the following specific steps:

[0030] 4.1. Remove the two middle ring segments from the shield tunnel, excavate the central pilot tunnel to 0.35m outside the deformation joint (a total of 1.5m), spray 300mm thick concrete to seal the tunnel face to form a blocking wall, and promptly construct the central column and corresponding ring beam using a buckle frame and bamboo plywood formwork. After the construction of the central column and its upper ring beam is completed, erect temporary steel supports under the ring beam. Fill the space between the cast ring beam and the blocking wall with dense concrete.

[0031] The excision area for the central pilot tunnel construction is 3m (height) × 3m (width) × 0.4m (thickness). Before cutting the segments, the central pilot tunnel is first positioned and measured, and the outline to be cut is drawn. A water-grinding drill is then used to drill holes from top to bottom according to the outline, and the segments are excised in sequence. First, the segments are divided vertically, cutting one by one from both sides to the center (staggered left and right). Then, the segments are divided horizontally, cutting sequentially from top to bottom. The volume of each segment is no larger than 1 cubic meter and the weight is no more than 2.4 tons. The cut concrete blocks are sequentially hoisted onto a water cart using a small winch. The cart is then transported to the station stairwell and lifted out. The segments around the ring beam are broken with a jackhammer to avoid damaging the main reinforcement in the segments, which must be anchored into the ring beam.

[0032] 4.2. Remove the two ring segments on the left side of the shield tunnel, excavate the left pilot tunnel to 0.35m outside the deformation joint (a total of 1.5m), spray 300mm thick concrete to seal the tunnel face to form a blocking wall, and promptly construct the corresponding ring beam. Fill the space between the cast ring beam and the blocking wall with concrete.

[0033] The segment cutting, dismantling, construction and transportation are the same as step 4.1;

[0034] 4.3. Remove the two right ring segments from the shield tunnel, excavate the right pilot tunnel to 0.35m outside the deformation joint (a total of 1.5m), spray 300mm thick concrete to seal the tunnel face to form a blocking wall, and promptly construct the corresponding ring beam. Fill the space between the cast ring beam and the blocking wall with concrete.

[0035] The segment cutting, dismantling, construction and transportation are the same as step 4.1;

[0036] 4.4. After the ring beam reaches the required strength, remove the temporary steel support below the interface ring beam.

[0037] The segment support and reinforcement device includes a temporary concrete structural plate on the track top, a temporary concrete bottom longitudinal beam, column 1, column 2, column 3, steel wedges and annular curved I-beams. The temporary concrete bottom longitudinal beam is arranged on the inner side of the bottom of the access passage opening. The lower ends of multiple columns 1 and multiple columns 2 are respectively and longitudinally fixedly connected to the temporary concrete bottom longitudinal beam and the platform plate at intervals, and column 2 faces the side wall of the bottom of the platform plate. The upper ends of multiple columns 1 and multiple columns 2 are fixedly connected to the temporary concrete structural plate on the track top. The temporary concrete structural slab on the track top and the track top beam structure are cast into an integral track top beam slab structure. The lower ends of multiple columns are fixedly connected to the track top beam structure at longitudinal intervals and are located directly above column two. The upper ends are fixedly connected to an annular arc-shaped I-beam. The outer arc surface of the annular arc-shaped I-beam rests on the annular pipe segment and is fixedly connected to it. Multiple steel wedges are used, which are evenly spaced and fixedly connected to the annular pipe segment and the track top beam structure and are located at the corner formed by the annular pipe segment and the track top beam structure.

[0038] Preferably, the above-mentioned column one, column two and column three all adopt double-piece I-steel columns, the upper and lower ends of column one are fixedly connected to steel plate two and steel plate one respectively, the upper and lower ends of column two are fixedly connected to steel plate four and steel plate three respectively, and the lower end of column three is fixedly connected to steel plate five.

[0039] Preferably, epoxy filling material 2 is filled between the contact surface between the annular arc-shaped I-steel and the annular segment.

[0040] Preferably, epoxy filling material 1 is filled between the contact surface of the steel wedge and the annular segment.

[0041] Preferably, both sides of the middle part of the above-mentioned multiple columns are fixedly connected by two middle longitudinal connecting channel steel beams, and the inner side near the bottom is fixedly connected by a bottom longitudinal connecting I-beam. The corresponding columns one and two are fixedly connected by an I-beam connecting beam, and the bottoms between two adjacent columns two are fixedly connected by an I-beam connecting beam between the two columns. The middle and upper parts of the multiple columns two are fixedly connected by a middle longitudinal connecting I-beam and an upper longitudinal connecting I-beam respectively.

[0042] Preferably, the lower parts of the plurality of columns three are fixedly connected by longitudinally connecting I-beams, and the column three and the steel wedge block are fixedly connected by an upper I-beam connecting beam.

[0043] Preferably, the above-mentioned segment support and reinforcement device for the construction of the opening of the existing shield tunnel entrance and exit channel also includes a plurality of segment longitudinal fastening channel steels, which are longitudinally fixedly connected to the annular segment and circumferentially spaced between the column three and the steel wedge block.

[0044] Beneficial effects of the present invention: Compared with the prior art, the effects of the present invention are as follows:

[0045] 1) The method of the present invention can safely and quickly complete the construction of evacuation passages and entrance and exit segment openings in existing shield tunnels. The construction progress is fast, structural deformation is minimal, and safety and quality are guaranteed. It effectively shortens the construction period and ensures the smooth realization of the construction unit's established goals. It has significant social and economic benefits and has been highly praised by supervisors and owners.

[0046] 2) This invention fully utilizes the existing shield tunnel track top structural beams and platform slab bottom side walls, and adds a temporary track top concrete structural slab and temporary concrete bottom longitudinal beams that are cast as an integral structure with the track top beam structure, forming a stable load-bearing support point on one side of the access passage opening. The new steel support structure system forms an effective temporary support structure solution only on one side of the access passage opening, avoiding and effectively protecting the track area and preventing the impact of thermal slip. This effectively solves the problems of blocking traffic in the tunnel, interrupting other construction work, and easily causing damage to the existing track. The technology is safe and reliable, ensuring the construction schedule.

[0047] 3) The present invention uses double-jointed steel sections to form the main columns, and uses steel sections that are rationally segmented (to enable manual transport) for connection, thereby forming a stable frame support structure. This is very suitable for transporting structural components and erecting facilities in relatively narrow spaces, greatly improving construction safety and efficiency, shortening construction period, and achieving significant economic benefits.

[0048] 4) Use two middle longitudinal connecting channel steel beams, the bottom longitudinal connecting I-beam, the I-beam connecting beam, the I-beam connecting beam between the two columns, the middle longitudinal connecting I-beam and the upper longitudinal connecting I-beam to connect column one, column two, the temporary concrete structure slab on the top of the track and the platform slab into a stable support system one. Use the longitudinal connecting I-beam and the upper I-beam connecting beam to connect column three, the steel wedge block and the annular pipe segment, and the track top beam structure into a stable support system two, so that the entire support system is interconnected in the vertical and horizontal directions to form a more stable framework system structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a flow chart of the construction process for the opening of the connecting passage in an existing shield tunnel;

[0050] Figure 2 This is a schematic diagram of the three-step construction process of three pilot tunnels;

[0051] Figure 3 This is a schematic diagram of backfill grouting behind the segment wall;

[0052] Figure 4 This is the layout diagram of the soil reinforcement holes between the left and right lines;

[0053] Figure 5 It is the cross-section diagram of soil reinforcement between the left and right lines;

[0054] Figure 6 This is a schematic diagram of the layout of grouting holes in the opening range;

[0055] Figure 7 This is a schematic diagram of the grouting cross section of the opening range;

[0056] Figure 8 Schematic diagram of hole arrangement for core drilling inspection;

[0057] Figure 9 This is a schematic diagram of the interface ring beam and columns;

[0058] Figure 10 This is a schematic diagram of the construction of the middle pilot tunnel;

[0059] Figure 11 This is the schematic diagram of the left pilot tunnel construction;

[0060] Figure 12 This is the schematic diagram of the right pilot tunnel construction;

[0061] Figure 13 This is a schematic diagram of the completion of the piece opening construction;

[0062] Figure 14 Provide a schematic diagram of the monitoring system layout;

[0063] Figure 15 This is the overall flow chart of the segment opening;

[0064] Figure 16 Remove the outline drawing for the middle guide tunnel;

[0065] Figure 17 It is a structural schematic diagram of the present invention;

[0066] Figure 18 It is a schematic diagram of the top view of the arrangement structure of the present invention;

[0067] Figure 19 This is a schematic diagram of the structure of the three connection points of the column. DETAILED DESCRIPTION

[0068] The present invention will be further described below with reference to specific embodiments.

[0069] Example 1: Figure 1-16As shown, a construction method for the opening of a connecting channel in an existing shield tunnel is as follows: first, a segment support reinforcement device is used to complete the support reinforcement of the segment in the opening area and the affected area that does not occupy the road, and after the advanced system grouting treatment is carried out to achieve the expected effect, a three-pilot tunnel and three-step construction method is adopted to carry out the segment opening construction: first, the middle pilot tunnel is excavated, and the middle pilot tunnel interface ring beam and columns and temporary steel supports are constructed; then the left pilot tunnel is constructed and the left ring beam is closed; finally, the right pilot tunnel is constructed and the right ring beam is closed, and the ring beam is removed after it is closed and reaches the design strength. In addition to temporary supports, the segment opening measures 8.1m (width) by 4.3m (height), requiring the removal of six rings of segments, all of which are removed from within the shield tunnel, with excavation proceeding outward. Internal support for the segments utilizes a "track-top structural crossbeam for top support" coupled with steel columns and channel steel fastening. Within the segment opening, a 500mm x 350mm x 1500mm track-top structural crossbeam serves as top support for the segments. Beneath the crossbeam, double-jointed I40b I-beam columns are installed for temporary support, spaced 1.5m apart and topped with steel wedges. Considering the high-deformation area above the shield tunnel segment opening, three 22b channel steels, spaced 0.43m circumferentially, are used to tension the segments to ensure safety during the opening. Each longitudinal segment opening has a 15m (10 rings) of segments affected. The openings of the left and right shield tunnels are staggered, with the track section closed during the openings. When the segments are broken, the segments and supports work together to bear the stratum load.

[0070] The specific steps of this method are as follows:

[0071] (1) Construction of temporary beams between the cross beams of the track top structure: using a buckle bracket, 100×100mm longitudinal square timber is set under the top formwork, and φ48 steel pipe with a wall thickness of 3.5mm is set under the square timber. The side formwork system uses 18mm thick bamboo plywood, the secondary keel is a wooden square with a spacing of 250mm, the cross-section of the square timber is 100×100mm, the main keel is a double-jointed φ48 steel pipe with a wall thickness of 3.5mm, and the bracket horizontal spacing is 600 / 450mm×longitudinal 500mm;

[0072] (2) Construction of double-row steel column support system: The construction process is as follows: measurement and setting out → roughening of pipe segments → embedding of steel bars on pipe segments → installation of bottom longitudinal beam steel bars and pre-embedding of supporting steel plates → installation of formwork brackets → pouring of concrete → removal of formwork and maintenance → setting up of operating platform → installation of steel supports → installation of steel wedges → installation of steel troughs for tightening pipe segments → epoxy material filling;

[0073] The specific steps include:

[0074] 2.1. Measurement and staking out: Measure the positions of temporary support bottom beams and temporary support columns in the segments according to the design drawings and actual site conditions;

[0075] 2.2. Chiseling: The contact surface between the cast-in-place structure and the segment structure is chiseled to form an artificial rough surface with a concave and convex area of ​​not less than 4mm. The contact surface between the new and old concrete is clean and dry.

[0076] 2.3. Planting reinforcement: Plant reinforcement according to the point, and try to avoid the existing segment structure reinforcement. The planting depth of reinforcement with a diameter less than 25mm is 24d1, where d1 represents the diameter of the reinforcement. If there is a sleeve in the segment within the column range, use the 18mm diameter steel bar end to thread and connect it to the sleeve;

[0077] 2.4. Installation of reinforcement for the supporting bottom longitudinal beam: Before tying the reinforcement, a scaffolding platform is set up. The main reinforcement for the temporary supporting bottom beam is 13 C20 steel bars. There is a pre-buried sleeve within the bottom beam, and C18 steel bars are used to connect the sleeve. The length of the bent anchor anchored in the bottom beam is 15d2, d2 represents the diameter of the C18 steel bar. C10 steel bars are used for embedding reinforcement on the pipe segments, 4 in each row, with an embedding depth of 24d3, d3 represents the diameter of the C10 steel bar. The spacing between each row is adjusted according to the actual situation on site. A8 steel bars are used for tensioning, with a spacing of 300mm. After the bottom beam reinforcement is tied, anchor plate A is embedded, with the center position of the anchor plate corresponding to the center of the rail top air duct crossbeam. Anchor plate B is embedded in the rail top air duct crossbeam with an embedding depth of 300mm.

[0078] 2.5. Formwork: The bottom beam support is made of steel pipe with a horizontal spacing of 500mm, a vertical spacing of 900mm, and a step distance of 1m. The support pedals are arranged and fixed on the upper row of horizontal bars. The side formwork is 1.5cm thick wooden formwork, with 50×100mm square timbers at a spacing of 20cm. There are double rows of steel pipes in the horizontal direction. The screw rods are mechanically connected to the pipe segments and the steel bars are welded. The steel pipe top support reinforcement and the screw rod reinforcement are staggered.

[0079] 2.6. Concrete pouring: Concrete is pumped by sky pump, and manually transported to the opening by wheelbarrow, poured into the silo by chute, and compacted by vibrating rod;

[0080] 2.7. Concrete formwork removal and curing: 1) Pay attention to safe construction when removing the formwork to prevent the formwork from falling and injuring people; 2) After the concrete is removed from the formwork, arrange for a dedicated person to use watering to maintain curing. According to the temperature and weather conditions, timely watering should be carried out to ensure the surface moisture of the concrete, and relevant records should be kept;

[0081] 2.8. Steel column installation: Two rows of steel columns are set up within the opening range. The steel columns on the side close to the dark tunnel are assembled with double-jointed I40 I-beams, totaling 10 columns. The I-beam columns on the platform slab are 4220mm long and are assembled in 4 sections, each 1m long, connected with bolts and reinforced by welding. Expansion screws are driven into the rail top structure on site, and a hoist is used to assist in manual installation. Steel wedges are installed above the rail top air duct beam to connect with the pipe segments. The steel columns on the side close to the track area are assembled with double-jointed 22b I-beams, totaling 6 columns. The double-jointed 22b I-beam columns on the platform slab are 3620mm long and are assembled in 2 sections. T20mm steel plates 320×320mm are welded at the bottom and top of the columns. The top of the section above the air duct beam (1.265m to 1.33m high) is beveled and is installed manually.

[0082] 2.9. Installation of steel wedges and segment tensioning channel steel: The steel wedges are made of double-jointed I25b I-beams with a center spacing of 1.5m. Each steel wedge is tightly connected to the segment and crossbeam using epoxy resin glue. Two C22 steel bars are welded together longitudinally. The segment tensioning channel steel 22b uses M16 and is connected to the segment through a reserved sleeve.

[0083] 2.10. Epoxy material filling: The bottom and top of the steel support are in contact with the concrete. The periphery is sealed with central structural sealant and filled with high-permeability reinforced modified epoxy grouting liquid.

[0084] When sealing the joints with sealant, be sure to reserve small holes for venting at high locations and holes for grouting at low locations. Use a dual-fluid automatic chemical grouting pump for grouting. When grouting, stop grouting when thick slurry flows out of the small holes for venting at high locations, and continue to use sealant to seal the venting holes and grouting holes.

[0085] (3) Systematic grouting of the opening area and its affected area: including grouting behind the segment wall, grouting between the left and right lines, and grouting of the segment opening and affected area. The grouting sequence is: grouting behind the segment wall → grouting of the segment opening and affected area → grouting between the left and right lines;

[0086] The specific steps include:

[0087] 3.1. Backfill grouting behind the segment wall: Secondary grouting behind the segment includes 14 rings, 4 in front and 4 behind the opening, with a grouting pressure not exceeding 0.3 MPa. Use 1:1 cement slurry for grouting. After reaching the designed grouting pressure, maintain it for 3-4 minutes before stopping grouting. Do not force or blindly grout the segment. Strengthen monitoring of the segment during the grouting process.

[0088] Secondary grouting is carried out behind the segments in the open ring and deformation zone. The grouting distribution is as follows: top section A7, sections A1 and A6 adjacent to the top section A7, sections A2 and A5 connecting sections A1 and A6, and sections A3 and A4 connecting sections A2 and A5. Grouting holes A1, A6, A2, and A5 are arranged in the central and southern parts of sections A1, A6, A2, and A5, respectively. Grouting pipes with valves are inserted into the secondary grouting holes. The grouting sequence is: A2-A5-A1-A6 symmetrical grouting. A3 and A4 are not grouted due to the influence of the track and backfill. A7 is the top pressure relief vent.

[0089] 3.2. Grouting of Segment Openings and Impact Areas: Advance Φ42 small guide tube supports are installed at the segment openings, with a spacing of 0.4m and a length of 5m. Seven rows of grouting holes are set up within the segment opening ring for full-section systematic grouting. The system grouting holes are 7 to 9m deep, and Φ42 steel flower tubes are inserted into the holes. After grouting, the steel flower tubes are not removed as a safety reserve. Simultaneously, 22 grouting holes are arranged in adjacent rings, with a drilling depth of 4m. After positioning on the segment, the holes are opened with a water-grinding drill and then drilled with an air drill. Grouting is carried out from the outside to the inside, with three holes skipped at a time to prevent grouting. A 1:1 cement single-liquid slurry is used, with a designed grouting pressure of 0.8 to 1.5MPa. This pressure is dynamically adjusted during construction based on monitoring conditions.

[0090] 3.3. Grouting between the left and right lines: Grouting reinforcement is carried out for the soil between the left and right lines. On the basis of grouting holes (hole depth 4m) arranged by utilizing the original grouting holes of the pipe segments, a row of anchor pipes (Φ42 steel flower pipes) are added on the upper and lower sides for grouting reinforcement support. The anchor pipes are Φ42 steel flower pipes with an outward inclination angle of 45 degrees, a hole depth of 4m, and a spacing of 3m.

[0091] A total of 33 grouting holes are arranged between the left and right lines, including 13 secondary grouting holes and 20 new holes;

[0092] A water-grinding drill is used to drill through the segments, and a pneumatic drill is used to form holes. Φ42 steel pipes are inserted into the grouting holes for grouting. A 1:1 cement single-liquid slurry is used, and the designed grouting pressure is 0.8-1.5MPa. During actual construction, it is dynamically adjusted according to monitoring conditions.

[0093] Grouting effect verification: Figure 8 The inspection hole arrangement shown is as follows: after all the grouting holes are grouting, 6 holes are drilled in each grouting treatment section to test the grouting effect. The water seepage in the inspection hole is not greater than 0.2L / min.m. Otherwise, the drilling and grouting should be increased for grouting. When the grouting effect does not meet the requirements, excavation is strictly prohibited. The drilling and grouting should be increased for grouting. Excavation can only be carried out after passing the inspection.

[0094] Handling of abnormal situations during grouting:

[0095] ① If water gushing occurs during drilling, stop drilling immediately and carry out grouting.

[0096] ② When the grouting pressure suddenly increases, only inject pure cement slurry or clean water. After the pump pressure returns to normal, grouting can be carried out again. If the pressure does not return to normal, stop grouting and check whether the management is blocked.

[0097] ③ When the slurry is injected very quickly and the pressure does not rise for a long time, adjust the slurry concentration and mix ratio, shorten the gel time, and perform grouting with a small pump volume and low pressure to allow the slurry to have a relative residence time in the cracks to facilitate gelation. Intermittent grouting can also be used, but the residence time cannot exceed the slurry gel time.

[0098] (4) Segment opening construction: The opening is opened from the inside of the shield tunnel to the outside entrance and exit, with an opening size of 8.1m (width) × 4.3m (height). The three-pilot tunnel three-step construction method is adopted: first, the middle pilot tunnel is excavated, and the middle pilot tunnel interface ring beam and columns are constructed; then the left pilot tunnel is constructed and the left ring beam is closed; finally, the right pilot tunnel is constructed and the right ring beam is closed. After the ring beam is closed and reaches the design strength, the temporary support is removed. During the segment opening construction process, monitoring work is strengthened and timely feedback is given to guide on-site construction; before laying the track, the steel supports of the opening ring and the adjacent ring are erected, the entrance and exit channels are constructed to the outside of the segment, and the ground reinforcement is completed and the secondary lining is constructed to the deformation joint. The two rings of the open ring segment adjacent to the adjacent ring are chiseled out; the following specific steps are included:

[0099] 4.1. Remove the two middle ring segments from the shield tunnel (remain 0.3m on the left and right sides of both rings to ensure the rigidity of the segment support, which will be removed after support is completed). Excavate the central pilot tunnel to 0.35m outside the deformation joint (a total of 1.5m). Spray 300mm thick concrete to seal the tunnel face to form a blocking wall. Promptly construct the central column and corresponding ring beam using a buckle frame and bamboo plywood formwork. After the construction of the central column and its upper ring beam is completed, erect temporary steel supports below the ring beam. Fill the space between the cast ring beam and the blocking wall with dense concrete.

[0100] The cutting range of the middle guide hole is 3m (height) × 3m (width) × 0.4m (thickness). Before cutting the pipe segment, the middle guide hole should be positioned and measured, and the outline to be cut should be drawn, such as Figure 16 The horizontal and vertical drilling outlines (multiple horizontal and vertical slits) shown are then drilled from top to bottom using a water-grinding drill, and the blocks are removed in sequence. First, vertical strips are cut from both sides toward the center (alternating left and right, cutting and breaking in the order 1-6 in the figure). Then, horizontal blocks are cut from top to bottom. The volume of each block is no larger than 1 cubic meter and the weight is no more than 2.4 tons. The cut concrete blocks are hoisted onto a water cart using a small winch. The cart is then transported to the station stairwell and lifted out. The segments around the ring beam are removed using a jackhammer to avoid damaging the main reinforcement in the segments, which must be anchored into the ring beam.

[0101] 4.2. Remove the two left rings of segments from the shield tunnel (remaining 0.45m of the side ring to ensure the rigidity of the segment support, which will be removed after support is completed). Excavate the left pilot tunnel to 0.35m outside the deformation joint (a total of 1.5m). Spray 300mm thick concrete to seal the tunnel face to form a blocking wall. Promptly construct the corresponding ring beams. Fill the space between the cast ring beam and the blocking wall with dense concrete.

[0102] Segment cutting, dismantling, construction and transportation are the same as step 4.1;

[0103] 4.3. Remove the two right ring segments from the shield tunnel, excavate the right pilot tunnel to 0.35m outside the deformation joint (a total of 1.5m), spray 300mm thick concrete to seal the tunnel face to form a blocking wall, and promptly construct the corresponding ring beam. Fill the space between the cast ring beam and the blocking wall with concrete.

[0104] Segment cutting, dismantling, construction and transportation are the same as step 4.1;

[0105] Concrete pouring method for ring beam and central column:

[0106] 1. The ring beam casting concrete adopts C50 and P12 waterproof concrete; the thickness of the steel bar protection layer is 45mm on the soil surface and 35mm on the soil surface.

[0107] 2. The ring beam is cast in two parts. Cast the two middle rings first, and then construct the ring beams on both sides after the strength meets the requirements.

[0108] 3. Install a ceiling pump on the ground and a ground pump in the stairwell, and use the ground pump to cast the center column and ring beam.

[0109] 4. To ensure the density of concrete, pour it in layers and windows. Pump concrete into the warehouse from bottom to top, from the joint of the poured section to the unpoured section. Make full use of the upper, middle and lower windows of the template, pour concrete in layers symmetrically, and control the uneven height difference of the walls on both sides within 1m. Connect a 3-5m hose of the same diameter to the front end of the discharge pipe, so that the pipe mouth is downward to avoid pumping directly to the concrete surface. The free fall height during concrete pouring cannot exceed 2 meters. If it exceeds, use the method of extending the hose to solve the problem of excessive concrete drop.

[0110] 4.4. After the ring beam reaches the required strength, remove the temporary steel support below the interface ring beam.

[0111] This method, for constructing segment openings in existing shield tunnels, retains external soil constraints and opens from the inside out. Adhering to the principles of "adequate support and reinforcement, advanced grouting, and monitoring and measurement," the method strictly adheres to the 18-character guideline for underground tunnel construction: "advanced grouting, rigorous grouting, short excavation, strong support, early closure, and frequent measurement." Monitoring and measurement are integrated into process management. Segments within the opening area and the affected area are reinforced using a method called "top support with track-mounted structural beams and temporary slabs, double-row steel column support, and channel steel fastening." After achieving the desired effect through advanced systematic grouting, the segment openings are constructed using a three-pilot tunnel, three-step construction method: excavating the central pilot tunnel, constructing the central pilot tunnel interface ring beam and columns, and temporary steel supports; then constructing the left pilot tunnel and closing the left ring beam; and finally, constructing the right pilot tunnel and closing the right ring beam, completing the full closure of the ring beams in the opening area. Once the ring beams are closed and have reached their design strength, the temporary supports are removed.

[0112] The present invention monitors the segment opening construction period: Before the segment opening construction, a monitoring system for the segment and track must be established (the longitudinal spacing of the monitoring sections is 1.5m). Since the track laying of this project has been completed, a monitoring system must be established for the roadbed structure settlement, track settlement, track gauge change, track lateral deformation, and shield tunnel settlement, uplift, horizontal convergence, and horizontal absolute displacement, and the monitoring frequency must be increased, such as Figure 14 .

[0113] Dismantling of the temporary support system composed of the segment support reinforcement device: After the casting and forming reaches the demolding time, the formwork is removed and maintained: The dismantling time of the formwork and temporary support system should comply with the concrete strength required by the "Concrete Structure Engineering Construction Acceptance Code" (GB50204-2015), and it can only be dismantled when it reaches 100% of the design strength.

[0114] When dismantling the temporary support system, dismantle it in sections, working from top to bottom. During dismantling, continue to monitor the deformation of the segments and openings to ensure absolute safety.

[0115] Construction of blind tunnel for communication channel:

[0116] The method of the present invention is applicable to the construction of non-road-occupying openings such as evacuation passages, entrance and exit passages of existing (shield) tunnels in soft surrounding rock formations, as well as similar engineering construction.

[0117] Application example of the method of the present invention: Shenzhen Metro Line 14 started construction in full swing in early 2018 and is scheduled to open to traffic at the end of 2022. At the beginning of 2020, the Cancer Hospital Station was added between Dayun Station and Baohe Station, about 3 kilometers away from Dayun Station and about 3 kilometers away from Baohe Station. The Cancer Hospital Station is located on the hillside of Paibeiwei Mountain. It is an underground tunnel station with left and right line separated platforms and a station hall set on the ground. The station is 223m long and has a cover of 18.5m to 43.5m. The shield section of the station adopts a construction process of small shield passing first and then large shield expansion. Since the construction of the Cancer Hospital Station was delayed by about two years, in order to meet the goal of simultaneous opening of the entire Shenzhen Metro Line 14, the order of the project implementation plan has been partially changed. At present, the shield tunnel track top structure, platform plate and track have been completed. The site no longer has the conditions to erect full-section temporary steel supports and other measures as originally planned to open the pipe segments, construct evacuation passages and entrances and exits. In order to ensure that the hot-rolling target of Shenzhen Metro Line 14 is achieved as scheduled, the opening plan of the temporary support segments must be adjusted to avoid the track area, achieve construction without occupying the road, and avoid affecting the hot-rolling.

[0118] The Cancer Hospital Station has two entrances and exits, B and C, and two evacuation passages, A and D. The structure is buried at a depth of 34.6 to 46 meters at the opening of the shield tunnel. The main strata are massive strongly weathered sandstone and massive strongly weathered carbonaceous shale.

[0119] During the construction of this project, by studying and applying the existing shield tunnel connecting channel opening construction method, fully utilizing the existing track beam-slab structure, and using high-rigidity steel materials to rationally design the support system, the on-site assembly process was simple and clear, and the construction was convenient and fast. It effectively avoided the track area, achieved non-roadside construction, and avoided the impact of construction on adjacent track areas. The pipe segment opening construction progress was fast, and the structural deformation was small. The maximum deformation during the pipe segment opening construction was controlled within 2mm, far less than the design standard requirement of 10mm. Safety and quality were guaranteed. Despite the two-year delay in the project start time, the project avoided the impact of the project on related units causing suspension and idle work, as well as the delayed opening of Metro Line 14. The smooth realization of the construction unit's established goals was ensured, creating direct economic benefits of approximately 8 million yuan, with significant social and economic benefits, and received high praise from the supervisor and the owner.

[0120] Example 2: Figure 17-19 As shown, for Figure 1The existing structure consists of an annular segment 1, a tunnel bottom backfill 2 installed at the bottom of the annular segment, a track 3 installed on the tunnel bottom backfill 2, a platform plate 26, a side wall 4 at the bottom of the platform plate and a track top beam structure 5. The track plate is arranged at the track top beam structure 5 facing the track 3. The segment support and reinforcement device designed by the present invention includes a temporary concrete structure plate 6 on the track top, a temporary concrete bottom longitudinal beam 7, a column 9, a column 2 12, a column 3 16, a steel wedge 17 and an annular arc-shaped I-beam 22. The temporary concrete bottom longitudinal beam 7 is arranged on the inner side of the bottom of the entrance and exit channel opening 26. The lower ends of multiple columns 1 9 and multiple columns 2 12 are respectively and longitudinally fixedly connected to the temporary concrete structure plate 6 at intervals. The soil bottom longitudinal beam 7 and the platform plate 27 are on the side wall 4 with the column 2 12 facing the bottom of the platform plate 27. The upper ends of multiple columns 1 9 and multiple columns 2 12 are fixedly connected with the temporary concrete structure plate 6 on the top of the track. The temporary concrete structure plate 6 and the track top beam structure 5 are cast into an integral structure and are flush with the lower end surface of the track top beam structure 5. The lower ends of multiple columns 3 16 are longitudinally fixedly connected to the track top beam structure 5 and are located directly above the column 2 12. The upper ends are fixedly connected with an annular arc-shaped I-beam 22. The outer arc surface of the annular arc-shaped I-beam 22 rests on the annular pipe segment 1 and is fixedly connected to it. The steel wedges 17 are made of multiple pieces and are evenly spaced with the annular pipe segment 1 and the track top. The beam structure 5 is fixedly connected and located at the corner formed by the annular segment 1 and the rail top beam structure 5, and also includes a plurality of segment longitudinal fastening channel steels 24, which are longitudinally fixedly connected to the annular segment 1 and circumferentially spaced between the column three 16 and the steel wedge 17. The segments within the influence range around the segment demolition area are fastened with the segment longitudinal fastening channel steels 24 to ensure that the segments in the non-demolition area are not deformed or displaced. The spacing between adjacent columns one and two is 1.5m, the circumferential spacing of the segment longitudinal fastening channel steels is 0.43m, the temporary concrete bottom longitudinal beam 7 is connected to the segment with embedded steel bars, and the track top temporary concrete structure plate 6 is fixed to the segment with embedded steel bars. The longitudinal fastening channel steel of the pipe segment is connected to the pipe segment using M16 and the pipe segment through a reserved sleeve. The present invention makes full use of the existing shield tunnel track top structural beams and the bottom side walls of the platform slab, and adds temporary concrete structural slabs and temporary concrete bottom longitudinal beams on the track top to form a stable force support point. On this basis, a new type of steel support structure system is designed, which forms an effective temporary support structure scheme only on one side of the entrance and exit opening, avoiding and effectively protecting the track area to prevent the impact on hot slip, effectively solving the problems of blocking traffic in the tunnel, interrupting other construction operations, and easily causing damage or damage to the existing track. The technology is safe and reliable, and the construction period is guaranteed.

[0121] Preferably, the above-mentioned column 1 9, column 2 12 and column 3 16 all adopt double-piece I-steel columns, the upper and lower ends of column 1 9 are fixedly connected to steel plate 2 8-2 and steel plate 1 8-1 respectively, the upper and lower ends of column 2 12 are fixedly connected to steel plate 4 11-2 and steel plate 3 11-1 respectively, and the lower end of column 3 16 is fixedly connected to steel plate 5 11-3.

[0122] Preferably, epoxy filling material 23-2 is filled between the contact surface of the above-mentioned annular arc I-beam 22 and the annular tube segment 1; epoxy filling material 1 23-1 is filled between the contact surface of the steel wedge block 17 and the annular tube segment 1, and the epoxy filling material 1 23-1 and the epoxy filling material 2 23-2 are filled in their respective gaps and filled densely to ensure effective force transmission.

[0123] Preferably, both sides of the middle part of the above-mentioned multiple columns 19 are fixedly connected by two middle longitudinal connecting channel steel beams 10, and are fixedly connected by a bottom longitudinal connecting I-beam 13 near the inner side of the bottom. The corresponding column 19 and column 2 12 are fixedly connected by an I-beam connecting beam 25, and the bottom between two adjacent columns 2 12 is fixedly connected by an I-beam connecting beam 15 between the two columns. The middle and upper parts of multiple columns 2 12 are fixedly connected by a middle longitudinal connecting I-beam 14-1 and an upper longitudinal connecting I-beam 14-2 respectively; the middle and lower parts of multiple columns 3 16 are fixedly connected by a longitudinal connecting I-beam 19, and the column 3 16 and the steel wedge block 17 are fixedly connected by an upper I-beam connecting beam 18. The various steel structures are mainly connected by welding, and some are supplemented by high-strength bolts to be reliably connected into one. The use of high-strength bolts is convenient for assembly and disassembly, and also convenient for completing the demolition of the reinforced treatment of the access channel opening.

[0124] Preferably, the above-mentioned annular arc I-beam 22 and the column three 16 are fixedly connected on both sides with steel plate stiffening rib 1 20 and steel plate stiffening rib 2 21 respectively. The steel plate stiffening rib 1 20 and steel plate stiffening rib 2 21 are used to strengthen the structural support, thereby improving the rigidity and strength of the connection between the annular arc I-beam 22 and the column three 16, and making the support reliability better.

[0125] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for constructing an opening for a communication channel of an existing shield tunnel, characterized in that: First, the segment support reinforcement device is used to complete the support reinforcement of the segment in the opening area and the affected area that does not occupy the road. After the advanced system grouting treatment is carried out to achieve the expected effect, the three-pilot-tunnel three-step construction method is used to carry out the segment opening construction; The segment support and reinforcement device comprises a temporary concrete structural plate on the top of the track, a temporary concrete bottom longitudinal beam, a column 1, a column 2, a column 3, a steel wedge and an annular arc-shaped I-beam. The temporary concrete bottom longitudinal beam is arranged at the inner side of the bottom of the entrance and exit passage opening. The lower ends of the plurality of columns 1 and the plurality of columns 2 are respectively and longitudinally fixedly connected to the temporary concrete bottom longitudinal beam and the platform plate at intervals, and the column 2 faces the side wall at the bottom of the platform plate. The upper ends of the plurality of columns 1 and the plurality of columns 2 are fixedly connected to the temporary concrete structural plate on the top of the track. The temporary concrete structural plate on the track top and the track top beam structure are cast into an integral track top beam plate structure. The lower ends of the plurality of columns are respectively and longitudinally fixedly connected to the track top beam structure at intervals and are located directly above the second column. The upper ends are fixedly connected to an annular arc-shaped I-beam. The outer arc surface of the annular arc-shaped I-beam abuts against the annular segment and is fixedly connected thereto. A plurality of steel wedges are used, which are evenly spaced and fixedly connected to the annular segment and the track top beam structure and are located at the corner formed by the annular segment and the track top beam structure. The three-pilot tunnel three-step construction method is as follows: first, excavate the middle pilot tunnel, construct the middle pilot tunnel interface ring beam and columns, and temporary steel supports; then construct the left pilot tunnel and close the left ring beam; finally, construct the right pilot tunnel and close the right ring beam, at which point the full-closed construction of the ring beam in the opening area is completed, and the temporary supports are removed after the ring beam is closed and reaches the designed strength; The specific steps of the existing shield tunnel communication channel opening construction method are as follows: (1) Construction of temporary beams between the cross beams of the track top structure: using a disc-type bracket, a 100×100mm longitudinal square timber is set under the top formwork, and a Φ48 steel pipe with a wall thickness of 3.5mm is set under the square timber. The side formwork system uses 18mm thick bamboo plywood, the secondary keel is a wooden square with a spacing of 250mm, the cross-section size of the square timber is 100×100mm, and the main keel is a double-jointed Φ48 steel pipe with a wall thickness of 3.5mm; (2) Construction of double-row steel column support system: The construction work is carried out by adopting the construction process of surveying and setting out → roughening the pipe segments → embedding the steel bars on the pipe segments → installing the steel bars of the bottom longitudinal beam and pre-embedding the supporting steel plates → installing the formwork brackets → pouring concrete → removing the formwork for maintenance → setting up the operating platform → installing the steel supports → installing the steel wedges → installing the steel troughs for tightening the pipe segments → filling the gaps with epoxy materials; (3) Systematic grouting of the opening area and its affected area: including grouting of the backfill behind the segment wall, grouting between the left and right lines, and grouting of the segment opening and affected area. The grouting sequence is: grouting of the backfill behind the segment wall → grouting of the segment opening and affected area → grouting between the left and right lines; (4) Segment opening construction: The opening is opened from the inside of the shield tunnel toward the outside entrance. The opening size is 8.1m wide × 4.3m high. The three-pilot-tunnel three-step construction method is adopted. During the segment opening construction process, monitoring work is strengthened and timely feedback is provided to guide on-site construction.

2. The method for constructing an opening for a communication channel of an existing shield tunnel according to claim 1, characterized in that: The construction method in step (2) includes the following specific steps: 2.

1. Measurement and setting out: measure the positions of temporary support bottom beams and temporary support columns in the segments according to the design drawings and actual conditions on site; 2.

2. Roughening: The contact surface between the cast-in-place structure and the segment structure is roughened to form an artificial rough surface with a concave and convex surface of not less than 4mm. The contact surface between the new and old concrete is cleaned and dried; 2.

3. Planting reinforcement: Plant reinforcement according to the point, try to avoid the existing segment structure reinforcement, the planting depth of reinforcement with a diameter less than 25mm is 24d1, d1 represents the diameter of the reinforcement; 2.

4. Installation of reinforcement for the bottom longitudinal beam: a scaffolding platform is set up before tying the reinforcement. The main reinforcement for the temporary support bottom beam is 13 C20 steel bars. There is a pre-buried sleeve within the bottom beam. C18 steel bars are used to connect the sleeve. The length of the bent anchor anchored in the bottom beam is 15d2, d2 represents the diameter of the C18 steel bar. C10 steel bars are used for embedding reinforcement on the pipe segment, 4 in each row, and the embedding depth is 24d3, d3 represents the diameter of the C10 steel bar. The spacing of each row is adjusted according to the actual situation on site. A8 steel bars are used for tensioning, and the spacing is 300mm. After the bottom beam reinforcement is tied, the anchor plate A is embedded, and the center position of the anchor plate corresponds to the center of the rail top air duct crossbeam. The anchor plate B is embedded in the rail top air duct crossbeam, and the embedding depth is 300mm. 2.

5. Formwork: The bottom beam support is made of steel pipe, with a horizontal distance of 500mm, a vertical distance of 900mm, and a step distance of 1m. The support pedal is arranged and fixed on the upper row of cross bars. The side formwork is a 1.5cm thick wooden formwork, with vertical 50×100mm square wood and a spacing of 20cm. The steel bars for mechanical connection between the double-row steel pipes and the screw rods and the pipe segments are welded, and the steel pipe top support reinforcement and the screw rod reinforcement are staggered; 2.

6. Concrete pouring: Concrete is pumped by sky pump, and transported to the opening by wheelbarrow, then put into the warehouse by chute, and compacted by vibrator. 2.

7. Concrete demoulding and maintenance: 1) Pay attention to safe construction when removing the formwork; 2) After the concrete is demoulded, arrange a special person to use watering maintenance. According to the temperature and weather conditions at the time, water should be poured in time to ensure the surface humidity of the concrete, and relevant records should be kept; 2.

8. Installation of steel supports: Two rows of steel columns are set within the opening range. The steel columns close to the dark tunnel side are assembled with double I40 I-beams, totaling 10; the I-beam columns on the platform plate are 4220mm long, and the I-beams are assembled in 4 sections, each section is 1m long, connected by bolts, and reinforced by welding; expansion screws are driven into the rail top structure on site, and a hoist is used to assist in manual installation; steel wedges are set above the rail top air duct beam to connect with the pipe segment; the steel columns close to the track area are assembled with double 22b I-beams, totaling 6; the double 22b I-beam columns on the platform plate are 3620mm long, and the I-beams are assembled in 2 sections. T20mm steel plates 320×320mm are welded at the bottom and top of the columns, and the top of the section above the air duct beam is beveled and installed manually; 2.

9. Installation of steel wedges and segment tensioning channel steel: The steel wedges are made of double-jointed I25b I-beams with a center spacing of 1.5m. Each steel wedge is tightly connected to the segment and the crossbeam using epoxy resin glue; two C22 steel bars are welded longitudinally; the segment tensioning channel steel 22b uses M16 to connect to the segment through a reserved sleeve; 2.

10. Epoxy material filling: The bottom and top of the steel support are in contact with the concrete. The periphery is sealed with central structural sealant, and the high-permeability reinforced modified epoxy grouting liquid is used to fill the seams tightly; When sealing the seams with sealant, pay attention to leaving small holes for exhaust at high places and holes for grouting at low places; Use a double-liquid automatic chemical grouting pump for grouting. When grouting, stop grouting when thick slurry flows out of the high exhaust holes, and still use sealant to seal the exhaust holes and grouting holes.

3. The method for constructing an opening for a communication channel of an existing shield tunnel according to claim 1, characterized in that: The construction method in step (3) includes the following specific steps: 3.

1. Backfill grouting behind the segment wall: The secondary grouting behind the segment includes 14 rings, 4 rings before and after the opening, with a grouting pressure of no more than 0.3MPa. Grouting is done with 1:1 cement slurry. After reaching the designed grouting pressure, it can be stopped after 3-4 minutes. During the grouting process, the monitoring of the segment should be strengthened; Secondary grouting is carried out behind the segments of the opening ring and deformation zone; the grouting distribution is the top A7 section, the A1 section and A6 section close to the top A7 section, the A2 section and A5 section butting against the A1 section and A6 section, and the A3 section and A4 section butting against the A2 section and A5 section. The A1 section, A6 section, A2 section, and the middle and southern part of the A5 section are respectively arranged with the A1 grouting hole, A6 grouting hole, A2 grouting hole, and A5 grouting hole. A 0.8m long grouting pipe with a valve is inserted into the secondary grouting hole. The grouting sequence is: A2-A5-A1-A6 symmetrical grouting. A3 and A4 are not grouted due to the influence of the track and backfill. A7 is the top pressure relief vent. 3.

2. Grouting of the segment opening and affected area: Arrange advance Φ42 small guide tube support at the segment opening, with a spacing of 0.4m and a length of 5m; set 7 rows of grouting holes in the segment opening ring for full-section system grouting, with a system grouting hole depth of 7-9m, insert Φ42 steel flower pipes in the holes, and do not remove the steel flower pipes after grouting as a safety reserve; at the same time, arrange 22 grouting holes in adjacent rings, with a drilling depth of 4m. After positioning on the segment, use a water-grinding drill to open the holes, and then use an air drill to drill the holes; grouting is carried out from the outside to the inside, with intervals of 3 holes each time, using 1:1 cement single-liquid slurry, and the designed grouting pressure is 0.8-1.5MPa, which is dynamically adjusted according to the monitoring situation during construction; 3.

3. Grouting between left and right lines: Grouting reinforcement is carried out for the soil between the left and right lines. On the basis of using the original grouting holes of the pipe segments to arrange the grouting holes, a row of anchor pipes are added on the upper and lower sides for grouting to strengthen the support. The anchor pipes are Φ42 steel flower pipes with an outward inclination angle of 45 degrees, a hole depth of 4m, and a spacing of 3m; A total of 33 grouting holes are arranged between the left and right lines, including 13 secondary grouting holes and 20 new holes; A water-grinding drill is used to drill through the pipe segments, and a pneumatic drill is used to form holes. Φ42 steel flower pipes are inserted into the grouting holes for grouting. A 1:1 cement single-liquid slurry is used, and the designed grouting pressure is 0.8~1.5MPa, which will be dynamically adjusted according to the monitoring conditions during actual construction.

4. The method for constructing an opening for a communication channel of an existing shield tunnel according to claim 1, characterized in that: The segment opening construction method in step (4) includes the following specific steps: 4.

1. Remove the middle two ring segments from the shield tunnel, excavate the middle guide hole to 0.35m outside the deformation joint, spray 300mm thick concrete to seal the tunnel face to form a blocking wall, and promptly construct the central column and corresponding ring beam, using disc-type brackets and bamboo plywood formwork for casting. After the construction of the central column and its upper ring beam is completed, a temporary steel support is erected under the ring beam, and the space between the cast ring beam and the blocking wall is filled with concrete; The excision range of the middle guide hole construction is 3m high × 3m wide × 0.4m thick. Before cutting the pipe segment, the middle guide hole is first positioned and measured, and the contour line to be cut is drawn. According to the contour line, a water-grinding drill is used to bite holes from top to bottom and cut in blocks in sequence. First, it is divided into strips vertically and cut from both sides to the middle one by one. When cutting from both sides to the middle one by one, it is staggered left and right. Then it is divided into blocks horizontally and cut from top to bottom in sequence. The volume of each block is not more than 1 cubic meter and the weight is not more than 2.4 tons. The cut concrete blocks are hoisted to the trolley by a small winch in sequence. The trolley is transported to the station staircase hole and hoisted out. The pipe segments around the ring beam are broken with a pneumatic pick. The main reinforcement in the pipe segment needs to be anchored into the ring beam. 4.

2. Remove the two ring segments on the left side from the shield tunnel, excavate the left pilot tunnel to 0.35m outside the deformation joint, a total of 1.5m, spray 300mm thick concrete to seal the tunnel face to form a blocking wall, and promptly construct the corresponding ring beam, and fill the space between the cast ring beam and the blocking wall with concrete; The segment cutting, dismantling, construction and transportation are the same as step 4.1; 4.

3. Remove the two ring segments on the right side of the shield tunnel, excavate the right pilot tunnel to 0.35m outside the deformation joint, a total of 1.5m, spray 300mm thick concrete to seal the tunnel face to form a blocking wall, and promptly construct the corresponding ring beam, and fill the space between the cast ring beam and the blocking wall with concrete; The segment cutting, dismantling, construction and transportation are the same as step 4.1; 4.

4. After the ring beam reaches sufficient strength, remove the temporary steel support under the interface ring beam.

5. The method for constructing an opening for a communication channel of an existing shield tunnel according to claim 1, characterized in that: Column one, column two and column three are all made of double I-beam columns. The upper and lower ends of column one are fixedly connected with steel plate two and steel plate one respectively, the upper and lower ends of column two are fixedly connected with steel plate four and steel plate three respectively, and the lower end of column three is fixedly connected with steel plate five.

6. The method for constructing an opening for a communication channel of an existing shield tunnel according to claim 1, characterized in that: The contact surface between the annular arc I-beam and the annular segment is filled with epoxy filling material No. 2; the contact surface between the steel wedge block and the annular segment is filled with epoxy filling material No.

1.

7. The method for constructing an opening for a communication channel of an existing shield tunnel according to claim 1, characterized in that: Both sides of the middle part of multiple columns one are fixedly connected by two middle longitudinal connecting channel steel beams, and the inner side near the bottom is fixedly connected by a bottom longitudinal connecting I-beam. The corresponding column one and column two are fixedly connected by an I-beam connecting beam, and the bottom between two adjacent columns two is fixedly connected by an I-beam connecting beam between the two columns. The middle and upper parts of multiple columns two are fixedly connected by a middle longitudinal connecting I-beam and an upper longitudinal connecting I-beam respectively; the lower part of multiple columns three is fixedly connected by a longitudinal connecting I-beam, and column three and the steel wedge block are fixedly connected by an upper I-beam connecting beam.

8. The method for constructing an opening for a communication channel of an existing shield tunnel according to claim 1, characterized in that: The segment support and reinforcement device also includes a plurality of segment longitudinal fastening channel steels, which are longitudinally fixedly connected to the annular segment and circumferentially spaced and arranged between the column three and the steel wedge block.

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