A double-split starting method for a double-track tunnel shield with small clearance

Abstract

The present invention discloses a double-split starting method for a small-clearance double-track tunnel shield, comprising the following steps: layout of the starting station main structure, backfill reinforcement of the starting end, installation of temporary sealing of the tunnel door, installation of the starting frame, shield assembly and debugging, installation of the reaction frame, installation of the negative ring segment, and shield starting trial excavation. The present invention reasonably arranges the starting station structure well, adopts the construction of temporary reverse dark excavation guide tunnel to assist the split starting, and sequentially installs the shield starting frame, the reaction frame, and the negative ring segment to achieve the split starting construction of the double-track small-clearance tunnel shield under the condition of overall starting difficulties due to insufficient site space. It has been verified by engineering practice that the split starting method has the advantages of small construction cross-influence, small impact on the surrounding environment, reduced construction period pressure, safety and reliability, etc., and can be applied to subway shield starting station end well length insufficient projects.

Description

Technical Field

[0001] The invention belongs to the field of tunnel starting engineering, and in particular relates to a double-split starting method for a small-clearance double-line tunnel shield. Background Art

[0002] With the rapid development of urban rail transit, shield construction has gradually become the main method for building underground tunnels. According to the conventional shield construction process requirements, it is necessary to set up a shield starting shaft at the end of the station, and the construction scope of the station main structure should have the conditions for placing the shield machine head, the length of the supporting equipment, and the setting of the slag hole, and complete the corresponding starting work in the starting shaft at the end.

[0003] To meet the above conditions, the main construction of the station needs to occupy a large amount of construction site to meet the construction needs. The conventional shield starting method has the characteristics of large land occupation and long station main construction period. Under the complex surrounding environment of the city, it is difficult to construct a starting station with a suitable length due to the demolition and occupation of ground buildings (structures), the relocation of underground municipal pipelines, and the diversion of ground traffic. When the ground demolition and land occupation coordination progress slowly, and the section main line has to be constructed first due to the construction period constraints, in order to meet the construction period requirements of the subway without affecting the structural safety, it is necessary to study a new type of double-track tunnel split starting method in a shorter end starting shaft, which can not only ensure the safety of shield starting, but also reduce construction delays. Summary of the invention

[0004] The present invention is proposed to solve the problems existing in the prior art, and its purpose is to provide a double-split starting method for a double-line tunnel shield with a small clearance.

[0005] The technical solution of the present invention is: a double-split starting method for a small-clearance double-line tunnel shield, comprising the following steps:

[0006] ⅰ. Layout of the main structure of the departure station

[0007] The shield machine is started by using a split start method. The distance between the start shaft portal and the excavation port must be large enough to accommodate the shield machine host, equipment bridge, and trailer #1. Trailers #2, #3, #4, and #5 are placed in the space near the side wall. Trailers #1 and #2 can be connected by extending the pipeline, and trailer #6 is placed on the ground for standby use.

[0008] ⅱ. Backfill and reinforce the starting end

[0009] After the main structure of the station is completed, C15 plain concrete is backfilled between the fertilizer troughs in front of the tunnel gate at the starting end of the shield tunnel;

[0010] ⅲ. Install temporary seal of tunnel door

[0011] During the construction of the side wall at the starting end, the shield pre-buried steel ring is installed at the tunnel portal, and the shield pre-buried steel ring must be tightly connected with the side wall structural steel bars; before the shield is officially started, the sealing folding plate and rubber curtain are installed at the tunnel portal;

[0012] ⅳ. Install the launch frame

[0013] The starting frame is installed before the shield machine is assembled. The two sides of the starting frame are reinforced with starting frame reinforcement steel. During the reinforcement process, the starting frame reinforcement steel is reinforced symmetrically to avoid misalignment of the starting frame.

[0014] ⅴ. Conduct shield assembly and debugging

[0015] The starting equipment of the split starter is hoisted into the shield body according to the left and right lines. After the shield machine mainframe advances a certain distance, it connects the 2# trailer, 3# trailer, 4# trailer, and 5# trailer on the side to the 1# trailer;

[0016] ⅵ. Install the reaction frame

[0017] In order to ensure that the reaction frame provides sufficient reaction force for the shield machine to start and ensure the stability of the reaction frame, steel plates are pre-buried according to the reaction frame legs and the reaction frame rear support installation positions during the station floor construction, and the reaction frame is installed later;

[0018] ⅶ. Install the negative ring segment

[0019] The negative ring segments are assembled according to the through-seam segments. The assembled negative ring segments are pushed out of the shield tail and the next ring segment assembly begins.

[0020] ⅷ. Shield tunneling starts trial excavation

[0021] The cutterhead of the shield machine main unit is pushed forward to the tunnel gate, the blockage in front of the tunnel gate is broken, the rubber curtain is pressed against the outside of the shield machine, the cutterhead cuts the soil, and the fixed length at the beginning of excavation is used as the trial excavation section. After completing the excavation of this section, the negative ring segment is removed, and then the supporting trailers 2#, 3#, 4#, 5# and 6# all enter the tunnel.

[0022] Furthermore, in step i, temporary excavation openings and lifting openings are set on the main structure of the station, and the 6# trailer is lifted in for overall connection, and temporary columns are set in the main structure of the station to meet the travel needs of the gantry crane.

[0023] Furthermore, in step i, a temporary reverse guide tunnel is secretly excavated at the end of the main structure of the station to meet the needs of horizontal transportation of the shield machine.

[0024] Furthermore, in step iv, the spatial position of the shield's starting posture needs to be determined based on the tunnel design axis, and then the spatial position of the starting frame is inferred. The spatial position of the starting frame is adjusted based on the net size, diameter, center position of the starting portal, geological conditions, and installation form of the negative ring segments.

[0025] Furthermore, the assembly sequence of step V is: 2# trailer, 3# trailer, 4# trailer, 5# trailer → 1# trailer → equipment bridge → screw conveyor downhole → middle shield → front shield → cutter head → shield tail downhole → screw conveyor installation → equipment bridge and main engine connection → hydraulic, fluid, and electrical circuit installation.

[0026] Furthermore, the debugging in step V includes no-load debugging and load debugging.

[0027] Furthermore, in step ⅲ, the rubber curtain and the annular baffle are arranged on the outside of the embedded steel ring of the shield, one end of the stud bolt passes through the baffle, the rubber curtain and the embedded steel ring of the shield and is screwed into the embedded nut, and a nut is screwed on the other end of the stud bolt. The baffle is hinged with multiple sealing folding plates through pin sleeves and pin shafts, and a gasket is arranged between the baffle and the nut.

[0028] Furthermore, in step ⅵ, the reaction frame includes two vertical reaction frame columns and two horizontal reaction frame beams between the reaction frame columns, reaction frame diagonal braces are arranged between adjacent reaction frame columns and reaction frame beams, and reaction frame rear supports are arranged on the backs of the two reaction frame columns and the top reaction frame beam, and the reaction frame rear supports are connected to the embedded steel plate.

[0029] Furthermore, the assembly sequence of the negative ring segments in step ⅶ is as follows: the assembly position of the A2 segment is measured and located, the A2 segment is placed on the shield tail welding channel steel according to the measured position, and the A1 segment and A3 segment are assembled in sequence. When assembling the segments, the segment connecting bolts are tightened in time. When assembling the B1 segment and B2 segment, the B1 segment and B2 segment are welded and fixed to the shield tail with L-shaped steel plates near the shield tail brush position, and the segment connecting bolts are tightened in time. When assembling the K-type segment, pay attention to the assembling machine cylinder thrust not being too large to avoid the B1 segment and B2 segment being fixed with the L-shaped steel plates. After the segments are assembled, the segment bolts are tightened in time and the L-shaped steel plates are cut off.

[0030] The present invention makes a reasonable spatial layout of the structural shaft of the starting station, constructs a temporary reverse dark excavation guide tunnel to assist the split starting, and sequentially installs the shield starting frame, reaction frame, and negative ring segment to achieve the split starting construction of the double-track small clear distance tunnel shield under the condition that the overall starting is difficult due to insufficient site space. It has been verified by engineering practice that the split starting method has the advantages of small construction cross-influence, small impact on the surrounding environment, reduced construction period pressure, safety and reliability, etc., and can be applied to subway shield starting station end shaft length insufficient projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the backfill reinforcement of the station end of the present invention;

[0032] Figure 2 It is a schematic diagram of the plan layout of the shield right line split starting equipment facilities of the present invention;

[0033] Figure 3 It is a schematic diagram of the plan layout of the left-line split starting equipment facilities of the shield machine of the present invention;

[0034] Figure 4 It is a schematic diagram of the cross-sectional layout of the shield split launching equipment facilities of the present invention;

[0035] Figure 5 It is a side view of the installation of the sealing folding plate and the rubber curtain in the present invention;

[0036] Figure 6 This is a front view of the installation of the sealing folding plate and the rubber curtain in the present invention;

[0037] Figure 7 is a cross-sectional view of the initiating frame of the present invention;

[0038] Figure 8 It is a schematic front elevation view of the initial reaction frame of the present invention;

[0039] Fig. 9 It is a side elevation schematic diagram of the initial reaction frame in the present invention;

[0040] Fig.10 This is a schematic diagram of the shield machine starting to enter the hole of the present invention;

[0041] Fig.11 This is a schematic diagram of the installation of the negative ring segment of the present invention;

[0042] in:

[0043] 1 Fertilizer trough in front of tunnel gate 2 C15 plain concrete

[0044] 3 Shield embedded steel ring 4 Station roof

[0045] 5 Station middle plate 6 Station bottom plate

[0046] 7 Station side wall 8 Shield machine main unit

[0047] 9 Equipment bridge 10 1# trailer

[0048] 11 2# trailer 12 3# trailer

[0049] 13 4# trailer 14 5# trailer

[0050] 15 Cave Gate 16 Excavation Entrance

[0051] 17 6# trailer 18 lifting port

[0052] 19 Lifting mouth door crane 20 Excavation mouth door crane

[0053] 21 Temporary reverse guide hole 22 Temporary pillar

[0054] 23 Screw conveyor 24 Counterforce frame column

[0055] 25 Reaction frame cross beam 26 Reaction frame diagonal brace

[0056] 27 Reaction frame rear support 28 Embedded steel plate

[0057] 29 Sealing folding plate 30 Rubber curtain

[0058] 31 Washer 32 Nut

[0059] 33 stud bolt 34 embedded nut

[0060] 35 Pin Bushing 36 Axis Pin

[0061] 37 Launching frame reinforcement steel 38 Launching frame

[0062] 39 Extension pipeline 40 A1 type segment

[0063] 41 A2 segment 42 B1 segment

[0064] 43 B2 segment 44 A3 segment

[0065] 45 K tube segment 46 baffle. DETAILED DESCRIPTION

[0066] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings and embodiments:

[0067] like Figures 1 to 11 As shown, a double-split starting method for a small-clearance double-line tunnel shield includes the following steps:

[0068] ⅰ. Layout of the main structure of the departure station

[0069] The shield machine is started by using a split start method. The distance between the tunnel gate 15 of the start shaft and the excavation port 16 must be enough to place the shield machine mainframe 8, the equipment bridge 9, and the 1# trailer 10. The 2# trailer 11, the 3# trailer 12, the 4# trailer 13, and the 5# trailer 14 are placed in the space near the side wall. The 1# trailer 10 can be connected to the 2# trailer 11 through the extension pipeline 39, and the 6# trailer 17 is placed on the ground for standby use.

[0070] ⅱ. Backfill and reinforce the starting end

[0071] After the main structure of the station is completed, fill the trough in front of the tunnel gate at the starting end of the shield with C15 plain concrete 2;

[0072] ⅲ. Install temporary seal of tunnel door

[0073] During the construction of the starting side wall, the shield pre-embedded steel ring 3 is installed at the tunnel door 15, and the shield pre-embedded steel ring 3 must be tightly connected with the side wall structural steel bars; before the shield is officially started, the sealing folding plate 29 and the rubber curtain 30 are installed at the tunnel door 15;

[0074] ⅳ. Install the launch frame

[0075] Before the shield machine is assembled, the starting frame 38 is installed. The starting frame reinforcement steel 37 is used to reinforce both sides of the starting frame 38. During the reinforcement process, the starting frame reinforcement steel 37 is reinforced symmetrically to avoid misalignment of the starting frame 38.

[0076] ⅴ. Conduct shield assembly and debugging

[0077] The starting equipment of the split starter is hoisted into the shield body according to the left and right lines respectively. After the shield machine main machine 8 advances forward for a certain distance, the 2# trailer 11, 3# trailer 12, 4# trailer 13, and 5# trailer 14 located on the side are connected to the 1# trailer 10;

[0078] ⅵ. Install the reaction frame

[0079] In order to ensure that the reaction frame provides sufficient reaction force for the shield to start and ensure the stability of the reaction frame, a steel plate 28 is pre-buried according to the reaction frame legs and the reaction frame rear support installation position during the station floor construction, and the reaction frame is subsequently installed;

[0080] ⅶ. Install the negative ring segment

[0081] The negative ring segments are assembled according to the through-seam segments. The assembled negative ring segments are pushed out of the shield tail and the next ring segment assembly begins.

[0082] ⅷ. Shield tunneling starts trial excavation

[0083] The cutterhead of the shield machine main unit 8 is pushed to the tunnel gate 15, breaking the blockage in front of the tunnel gate 15, the rubber curtain 30 is pressed against the outside of the shield machine, the cutterhead cuts the soil, and the fixed length of the starting excavation is used as the trial excavation section. After completing the excavation of this section, the negative ring segment is removed, and then the supporting trailers 2# 11, 3# trailer 12, 4# trailer 13, 5# trailer 14, and 6# trailer 17 all enter the tunnel.

[0084] In step i, a temporary unearthing opening 16 and a lifting opening 18 are set on the main structure of the station, and the 6# trailer 17 is lifted in for overall connection. A temporary column 22 is set in the main structure of the station to meet the travel needs of the gantry crane.

[0085] In step i, a temporary reverse guide tunnel 21 is secretly excavated at the end of the main structure of the station to meet the needs of horizontal shield transportation.

[0086] In step iv, the spatial position of the shield starting posture needs to be determined based on the tunnel design axis, and then the spatial position of the starting frame 38 is inferred. The spatial position of the starting frame 38 is adjusted by comprehensively considering factors such as the net size, diameter, center position of the starting portal 15, geological conditions, and installation form of the negative ring segment.

[0087] The assembly sequence of step V is: 2# trailer 11, 3# trailer 12, 4# trailer 13, 5# trailer 14→1# trailer 10→equipment bridge 9→screw conveyor 23 lowered into the well→middle shield→front shield→cutter head→shield tail lowered into the well→screw conveyor 23 installed→equipment bridge 9 connected to the main engine→hydraulic, fluid, and electrical circuit installation.

[0088] The debugging in step V includes no-load debugging and load debugging.

[0089] In step iii, the rubber curtain 30 and the annular baffle 46 are arranged on the outside of the embedded steel ring 3 of the shield, one end of the stud bolt 33 passes through the baffle 46, the rubber curtain 30, and the embedded steel ring 3 of the shield and is screwed into the embedded nut 34, and the other end of the stud bolt 33 is screwed with a nut 32. The baffle 46 is hinged with multiple sealing folding plates 29 through a pin sleeve 35 and a pin shaft 36, and a gasket 31 is arranged between the baffle 46 and the nut 32.

[0090] In step ⅵ, the reaction frame includes two vertical reaction frame columns 24 and two horizontal reaction frame beams 25 between the reaction frame columns 24, and reaction frame diagonal braces 26 are arranged between adjacent reaction frame columns 24 and reaction frame beams 25. The backs of the two reaction frame columns 24 and the top reaction frame beams 25 are provided with reaction frame rear supports 27, and the reaction frame rear supports 27 are connected to the embedded steel plates 28.

[0091] The assembly sequence of the negative ring segments in step ⅶ is as follows: measure and locate the assembly position of the A2 type segment 41, place the A2 type segment 41 on the shield tail welding channel steel according to the measured position, assemble the A1 type segment 40 and the A3 type segment 44 in sequence, tighten the segment connecting bolts in time when assembling the segments, and when assembling the B1 type segment 42 and the B2 type segment 43, weld the B1 type segment 42 and the B2 type segment 43 to the shield tail with L-shaped steel plates near the shield tail brush position, and tighten the segment connecting bolts in time, and when assembling the K type segment 45, pay attention to the assembling machine cylinder thrust not being too large to avoid the B1 type segment 42 and the B2 type segment 43 fixing L-shaped steel plates from being pushed off, and after the segments are assembled, tighten the segment bolts in time and cut off the L-shaped steel plates.

[0092] The starting station structure corresponding to the present invention includes a main station structure located underground, and the main station structure is provided with a lifting port 18 for lifting equipment and an excavation port 16 for excavation. A shield embedded steel ring 3 is provided at a tunnel gate 15 on one side of the main station structure. The tunnel gate 15 is sequentially assembled with a shield machine main unit 8, an equipment bridge 9, and a No. 1 trailer 10 in the length direction. A middle trailer that can be connected to the rear of the No. 1 trailer 10 through an extension pipeline 39 is provided outside the axis of the tunnel gate 15, and a tail trailer that can be lowered through the lifting port 18 and connected to the middle trailer is provided on the ground.

[0093] The station main structure comprises two tunnel doors 15, and a temporary reverse guide tunnel 21 is formed at the opposite side walls of the station main structure.

[0094] The hoisting opening 18 is located above one side of the tunnel door 15 , and the lateral distance between the unearthing opening 16 and the tunnel door 15 is sufficient to place the shield machine mainframe 8 , the equipment bridge 9 , and the No. 1 trailer 10 .

[0095] The hoisting port 18 is provided with a hoisting port gantry crane 19 for vertical transportation of pipe segments and grease, and the unearthed port 16 is provided with an unearthed port gantry crane 20 for transportation of slag.

[0096] The fertilizer trough 1 in front of the tunnel gate on the side wall of the station main structure is backfilled with C15 plain concrete 2 to ensure the stability of the stratum at the starting end of the shield.

[0097] The shield pre-embedded steel ring 3 is connected to the steel bars of the station main structure, and a sealing structure is arranged on the outer side of the shield pre-embedded steel ring 3 to seal the gap between the tunnel door 15 and the shield machine main body 8.

[0098] The sealing structure includes a rubber curtain 30 and a circular baffle 46 which are sequentially arranged on the outside of the shield embedded steel ring 3. One end of the stud bolt 33 passes through the baffle 46, the rubber curtain 30, and the shield embedded steel ring 3 and is screwed into the embedded nut 34. The other end of the stud bolt 33 is screwed with a nut 32. The baffle 46 is hinged to multiple sealing folding plates 29 through a pin sleeve 35 and a pin shaft 36. A gasket 31 is arranged between the baffle 46 and the nut 32.

[0099] A starting frame 38 is provided in the main structure of the station, and a starting frame reinforcement steel 37 is provided on the starting frame 38 for reinforcement along the length direction.

[0100] A shield tail support assembly is provided in the main structure of the station, and the shield tail support assembly includes a reaction frame and a negative ring pipe segment. The reaction frame includes two vertical reaction frame columns 24 and two transverse reaction frame beams 25 between the reaction frame columns 24. Reaction frame diagonal braces 26 are provided between adjacent reaction frame columns 24 and reaction frame beams 25. A reaction frame rear support 27 is provided on the back of the two reaction frame columns 24 and the top reaction frame beam 25, and the reaction frame rear support 27 is connected to the embedded steel plate 28.

[0101] The negative ring segment includes an A2-type segment 41 at the bottom, and an A1-type segment 40 and an A3-type segment 44 are respectively arranged on both sides of the A2-type segment 41. A B2-type segment 43 is arranged on the A1-type segment 40, and a B1-type segment 42 is arranged on the A3-type segment 44. A K-type segment 45 is arranged between the B2-type segment 43 and the B1-type segment 42.

[0102] The main structure of the station includes a station roof 4 at the top, a station floor 6 at the bottom, a station middle plate 5 at the middle, and a station side wall 7.

[0103] The tunnel gate 15 , the shield embedded steel ring 3 , and the temporary reverse guide tunnel 21 are all located in the station side wall 7 .

[0104] The middle trailer includes a 2# trailer 11, a 3# trailer 12, a 4# trailer 13, and a 5# trailer 14. The 2# trailer 11, the 3# trailer 12, the 4# trailer 13, and the 5# trailer 14 are parallel to the shield machine main body 8, the equipment bridge 9, and the 1# trailer 10.

[0105] The tail trailer includes a 6# trailer 17.

[0106] Preferably, the station main structure has space in the transverse width direction to place supporting equipment and facilities after the shield machine is started. The length distance does not meet the conventional starting length requirement and is solved by using a temporary reverse guide tunnel 21 constructed by dark excavation.

[0107] The 2# trailer 11, the 3# trailer 12, the 4# trailer 13, and the 5# trailer 14 are located on the side close to the side wall.

[0108] like Figure 2 , Figure 3 As shown, the main structure of the station includes a shield right line split starting device and a shield left line split starting device, and the shield right line split starting device and the shield left line split starting device have the same and symmetrical structures.

[0109] There are two unearthed openings 16, one for each of the right-line split starting equipment and the left-line split starting equipment of the shield machine.

[0110] There are four lifting openings 18, two of which are respectively provided for the right-line split starting equipment of the shield machine and the left-line split starting equipment of the shield machine.

[0111] Temporary columns 22 are also provided in the main structure of the station, and the temporary columns 22 meet the travel requirements of the gantry crane.

[0112] The length of the rubber curtain 30 is greater than the length of the sealing folding plate 29 and the baffle 46.

[0113] The rubber curtain 30 is turned up and contacts the shield machine mainframe 8 , and the sealing folding plate 29 presses the rubber curtain 30 .

[0114] The shield machine main unit 8 includes a cutter head, a front shield, a middle shield, a rear shield and a screw conveyor 23 . Example

[0115] Take the case where the total length of the shield machine main body 8, the equipment bridge 9, and the 1# trailer 10 is about 85m, and the fixed excavation distance is 100m as an example.

[0116] ⅰ. Layout of the main structure of the departure station

[0117] Due to the length limitation of the main structure of the station, the shield is started in a split-type starting mode. The distance between the starting shaft door 15 and the excavation port 16 is enough to place the shield machine main unit 8, the equipment bridge 9 and the 1# trailer 10. The 2# trailer 11, the 3# trailer 12, the 4# trailer 13 and the 5# trailer 14 are placed in the space close to the side wall. The 1# trailer 10 is connected to the 2# trailer 11 through the extension pipeline 39. The 6# trailer 17 is placed on the ground and is not used temporarily. After the excavation is completed for 100m, the negative ring is removed to transfer the 2# trailer 11, the 3# trailer 12, the 4# trailer 13 and the 5# trailer 14 to the shield excavation axis, and the 6# trailer 17 is hoisted into the shield starting shaft for the whole machine connection. Two temporary shield hoisting ports 18 and two unearthed ports 16 are set up in the starting shaft of the station. Temporary columns 22 are set up at the long-distance end of the middle longitudinal beam of the structure to meet the needs of gantry crane travel. A hoisting port gantry crane 19 is set up on the upper part of the shield hoisting port 18 for vertical transportation of pipe segments, grease, etc., and an unearthed port gantry crane 20 is installed on the unearthed port 16 mainly for transportation of slag. In order to meet the needs of horizontal transportation of shield, the end of the split starting station needs to be dark-dug to complete the temporary reverse guide hole 21, and the shield machine uses a tower crane to hoist from the shield hoisting port 18 into the bottom plate 6.

[0118] ⅱ. Backfill and reinforce the starting end

[0119] After the main structure of the station is completed, C15 plain concrete 2 is backfilled in the slope fertilizer trough 1 at the starting end of the shield to ensure the stability of the stratum at the starting end of the shield.

[0120] ⅲ. Install temporary seal of tunnel door

[0121] In order to prevent mud and water from leaking from the gap between the tunnel portal 15 and the shield shell, affecting the stability of the excavation surface soil, during the construction of the starting end wall, a shield embedded steel ring 3 is installed at the starting tunnel portal, and the steel ring 3 must be tightly connected to the end wall structural steel bars; before the shield is officially started, the tunnel portal sealing folding plate 29 and the rubber curtain 30 are installed to ensure the sealing effect.

[0122] ⅳ. Install the launch frame

[0123] Before the shield machine is assembled, the spatial position of the shield's starting posture is determined according to the tunnel design axis, and then the spatial position of the starting frame 38 is inferred. Combined with the net size, diameter, and center position of the starting tunnel portal 15, as well as the geological conditions of the end well and the installation form of the negative ring segment, the spatial position of the starting frame 38 is adjusted. Since the starting frame 38 must withstand the longitudinal and lateral thrusts and the torque to resist the rotation of the shield when the shield is started, the starting frame must be reinforced on both sides before the shield is started. When the axial and lateral starting frame reinforcement steel 37 of the starting frame is installed, it needs to be installed symmetrically to avoid the change of the position of the starting frame 38 caused by the reinforcement steel during the installation process.

[0124] ⅴ. Conduct shield assembly and debugging

[0125] The shield machine and its supporting equipment are composed of the shield machine main machine 8 including the cutter head / front shield / middle shield / rear shield, the equipment bridge 9 and 6 subsequent trailers, with a total length of about 85m. The components of the shield body are hoisted into the shield body according to the left and right lines. Trailer 2# 11, trailer 3# 12, trailer 4# 13, and trailer 5# 14 are placed at the side wall for assembly and connected to trailer 1# 10 through the extension pipeline 39. After excavating 100m, all trailers are assembled.

[0126] The downhole assembly steps are as follows:

[0127] 2# trailer 11, 3# trailer 12, 4# trailer 13, 5# trailer 14 → 1# trailer 10 → equipment bridge 9 → screw conveyor 23 lowered into the well → middle shield → front shield → cutter head → shield tail lowered into the well → screw conveyor installed → equipment bridge connected to main engine → hydraulic, fluid and electrical circuit installed.

[0128] After the shield is assembled and connected, no-load debugging can be carried out. The purpose of no-load debugging is mainly to check whether the equipment can operate normally. The main debugging contents are: hydraulic system, lubrication system, cooling system, power distribution system, grouting system, and calibration of various instruments. After no-load debugging is completed, load debugging can be carried out. The main purpose of load debugging is to check the load capacity of various pipelines and seals, and to further improve the work that cannot be completed by no-load debugging.

[0129] ⅵ. Install the reaction frame

[0130] The power of the shield machine is provided by the thrust cylinder, and the thrust cylinder top force acts on the shield tail support system when the shield machine starts. Generally, the shield tail support system is composed of a steel reaction frame, a negative ring segment, etc. The reaction frame column 24 is a box-type structure, made of Q235-A, with a cross-sectional size of 1000×700mm; there are 2 reaction frame beams 25, which are box-type structures, divided into upper beams and lower beams, made of Q235-A, and the cross-sectional size of the box structure is 1000×400mm; there are 4 reaction frame diagonal braces 26, made of Q235-A, and the cross-sectional size of the box structure is 1000×400mm; there are 5 reaction frame rear supports 27, which are divided into column rear supports and reaction frame rear supports 27 according to the installation position, and the material is 56b double-piece I-beam with a horizontal angle of 45°. In order to ensure that the reaction frame provides sufficient reaction force for the shield machine to start and ensure the stability of the reaction frame, steel plates 28 are embedded in advance according to the reaction frame legs and the reaction frame rear support installation positions during the station floor construction to fix the reaction frame.

[0131] ⅶ. Install the negative ring segment

[0132] Negative ring segments are assembled as through-seam segments. The assembly position of A2 segment 41 is measured and located. A2 segment 41 is placed on the shield tail welding channel according to the measured position. A1 segment 40 and A3 segment 44 are assembled in sequence. When assembling the segments, the segment connection bolts are tightened in time. When assembling B1 segment 42 and B2 segment 43, B1 segment 42 and B2 segment 43 are welded and fixed to the shield tail with L-shaped steel plates near the shield tail brush position, and the segment connection bolts are tightened in time. When assembling K segment 45, pay attention to the assembling machine cylinder thrust not being too large to avoid the L-shaped steel plates used to fix B1 segment 42 and B2 segment 43 being dislodged. After the segments are assembled, the segment bolts are tightened in time and the L-shaped steel plates are cut off. Push the assembled negative ring segment out of the shield tail and start assembling the next ring segment. Assemble 10 rings of negative ring segments in sequence.

[0133] ⅷ. Shield tunneling starts trial excavation

[0134] The cutter head of the shield machine is pushed forward to the tunnel gate, the blockage in front of the tunnel gate is broken, the curtain rubber plate is pressed against the outside of the shield machine, the cutter head cuts the soil, and the first 100m of excavation is the trial excavation section. After completing the excavation of this section, the negative ring segments are removed, and then the supporting trailers 2# 11, 3# 12, 4# 13, 5# 14, and 6# 17 all enter the tunnel.

[0135] The present invention makes a reasonable spatial layout of the structural shaft of the starting station, constructs a temporary reverse dark excavation guide tunnel to assist the split starting, and sequentially installs the shield starting frame, reaction frame, and negative ring segment to achieve the split starting construction of the double-track small clear distance tunnel shield under the condition that the overall starting is difficult due to insufficient site space. It has been verified by engineering practice that the split starting method has the advantages of small construction cross-influence, small impact on the surrounding environment, reduced construction period pressure, safety and reliability, etc., and can be applied to subway shield starting station end shaft length insufficient projects.

Claims

1. A double-split starting method for a double-line tunnel shield with a small clearance, characterized by: The following steps are involved: (i) Layout of the main structure of the departure station The shield machine is started by using a split start method. The distance between the tunnel door (15) of the start shaft and the excavation port (16) must be large enough to accommodate the shield machine mainframe (8), the equipment bridge (9), and the No. 1 trailer (10). The 2# trailer (11), the 3# trailer (12), the 4# trailer (13), and the 5# trailer (14) are placed in a space near the side wall, the 1# trailer (10) and the 2# trailer (11) can be connected via an extended pipeline (39), and the 6# trailer (17) is placed on the ground for standby use; (ii) Backfill and reinforce the starting end After the main structure of the station is completed, C15 plain concrete (2) is backfilled between the trough (1) in front of the tunnel gate at the starting end of the shield tunnel; (iii) Install temporary seal of tunnel door During the construction of the starting end side wall, a shield pre-embedded steel ring (3) is installed at the tunnel door (15), and the shield pre-embedded steel ring (3) must be tightly connected with the side wall structural steel bars; before the shield is officially started, a sealing folding plate (29) and a rubber curtain (30) are installed at the tunnel door (15); (iv) Install the launch frame Before the shield machine is assembled, the launching frame (38) is installed. Both sides of the launching frame (38) are reinforced with launching frame reinforcement steel (37). During the reinforcement process, the launching frame reinforcement steel (37) is reinforced symmetrically to avoid misalignment of the launching frame (38). (v) Conduct shield assembly and debugging The starting equipment of the split starter is hoisted into the shield body according to the left and right lines respectively. After the shield machine main machine (8) advances forward for a certain distance, the 2# trailer (11), 3# trailer (12), 4# trailer (13), and 5# trailer (14) located on the side are connected to the 1# trailer (10); (vi) Install the reaction frame In order to ensure that the reaction frame provides sufficient reaction force for the shield machine to start and to ensure the stability of the reaction frame, a steel plate (28) is pre-buried according to the reaction frame legs and the reaction frame rear support installation position during the station floor construction, and the reaction frame is subsequently installed; (ⅶ) Installing the negative ring segment The negative ring segments are assembled according to the through-seam segments. The assembled negative ring segments are pushed out of the shield tail and the next ring segment assembly begins. (ⅷ) Shield tunneling started trial excavation The cutterhead of the shield machine main unit (8) is advanced to the tunnel gate (15), the blockage in front of the tunnel gate (15) is broken, the rubber curtain (30) is pressed against the outside of the shield machine, and the cutterhead cuts the soil. The fixed length of the starting excavation is used as the trial excavation section. After the excavation of this section is completed, the negative ring segment is removed, and then the supporting trailers 2# (11), 3# (12), 4# (13), 5# (14), and 6# (17) are all put into the tunnel.

2. The double-split starting method of a small-clearance double-line tunnel shield according to claim 1 is characterized by: In step (i), a temporary unearthing opening (16) and a lifting opening (18) are provided on the main structure of the station, and the 6# trailer (17) is lifted in for overall connection, and a temporary column (22) is provided in the main structure of the station to meet the travel requirements of the gantry crane.

3. The double-split starting method of a small-clearance double-line tunnel shield according to claim 1 is characterized by: In step (i), a temporary reverse guide hole (21) is secretly excavated at the end of the station main structure to meet the needs of horizontal transportation of the shield machine.

4. The double-split starting method of a small-clearance double-line tunnel shield according to claim 1 is characterized in that: In step (iv), the spatial position of the shield starting posture needs to be determined based on the tunnel design axis, and then the spatial position of the starting frame (38) is inferred. The spatial position of the starting frame (38) is adjusted by combining the net size, diameter, and center position of the starting tunnel portal (15), the geological conditions, and the installation form of the negative ring segment.

5. The double-split starting method of a double-track tunnel shield with a small clearance as claimed in claim 1 is characterized by: The assembly sequence of step (v) is: trailer #2 (11), trailer #3 (12), trailer #4 (13), trailer #5 (14) → trailer #1 (10) → equipment bridge (9) → screw conveyor (23) lowered into the well → middle shield → front shield → cutter head → shield tail lowered into the well → screw conveyor (23) installed → equipment bridge (9) connected to the main engine → hydraulic, fluid, and electrical circuits installed.

6. The double-split starting method of a double-track tunnel shield with a small clearance as claimed in claim 1, characterized in that: The debugging in step (v) includes no-load debugging and load debugging.

7. The double-split starting method of a double-track tunnel shield with a small clearance as claimed in claim 1 is characterized by: In step (iii), the rubber curtain (30) and the annular baffle (46) are arranged outside the shield embedded steel ring (3), one end of the stud bolt (33) passes through the baffle (46), the rubber curtain (30) and the shield embedded steel ring (3) and is screwed into the embedded nut (34), and the other end of the stud bolt (33) is screwed with a nut (32), the baffle (46) is hinged with a plurality of sealing folding plates (29) through a pin sleeve (35) and a pin shaft (36), and a gasket (31) is arranged between the baffle (46) and the nut (32).

8. The double-split starting method of a double-track tunnel shield with a small clearance as claimed in claim 1 is characterized by: In step (vi), the reaction frame comprises two vertical reaction frame columns (24) and two horizontal reaction frame beams (25) between the reaction frame columns (24), reaction frame diagonal braces (26) are arranged between adjacent reaction frame columns (24) and reaction frame beams (25), and a reaction frame rear support (27) is arranged on the back of the two reaction frame columns (24) and the top reaction frame beam (25), and the reaction frame rear support (27) is connected to the embedded steel plate (28).

9. The double-split starting method of a double-track tunnel shield with a small clearance as claimed in claim 1, characterized in that: The assembly sequence of the negative ring segments in step (ⅶ) is as follows: the assembly position of the A2 segment (41) is measured and positioned, the A2 segment (41) is placed on the shield tail welding channel steel according to the measured position, the A1 segment (40) and the A3 segment (44) are assembled in sequence, and the segment connection bolts are tightened in time when the segments are assembled. When assembling the B1 segment (42) and the B2 segment (43), the B1 segment (42) and the B2 segment (43) are welded and fixed to the shield tail with an L-shaped steel plate near the shield tail brush position, and the segment connection bolts are tightened in time. When assembling the K segment (45), it is important to note that the thrust of the assembly machine cylinder should not be too large to avoid the L-shaped steel plate used to fix the B1 segment (42) and the B2 segment (43) being dislodged. After the segments are assembled, the segment bolts are tightened in time and the L-shaped steel plate is cut off.

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