Offshore forebay limited space shield launching structure and construction method

Abstract

The invention discloses an offshore forebay limited space shield launching structure and a construction method, and belongs to the technical field of shield construction.The offshore forebay limited space shield launching structure comprises a hole launching assembly, a counter-force frame and an unearthing mechanism, the hole launching assembly comprises a steel sleeve and a semi-ring pipe piece, the steel sleeve is installed at a launching hole and pre-buried at the launching hole, and the semi-ring pipe piece is installed on the steel sleeve; the length of the part, penetrating out of the starting hole, of the steel sleeve ranges from 45 cm to 55 cm, and the semi-ring segment is installed on the side, away from the starting hole, of the steel sleeve; the counter-force frame is arranged on the side, away from the steel sleeve, of the semi-ring pipe piece. The unearthing mechanism comprises a winch and a flat car, the flat car is used for bearing muck, and the winch is used for pulling the flat car out of the launching hole. According to the method, the occupation of the space in the offshore forebay can be effectively reduced, and the water intake tunnel can be directly excavated by taking the offshore forebay as a starting well, so that the construction efficiency is improved, and the occupation and damage of large-area excavation and backfilling to land resources in an offshore water intake project are reduced.

Description

Technical Field

[0001] The invention relates to the field of shield construction, and in particular to an offshore forebay limited space shield starting structure and a construction method. Background Art

[0002] In the cooling system of offshore nuclear power plants, it is usually necessary to set up an offshore forebay for storing and regulating seawater to meet the applications in specific industrial fields such as nuclear power plant cooling.

[0003] After the construction of the offshore forebay, seawater needs to be introduced. The construction of the water intake tunnel for introducing seawater usually adopts the shield method, the dark excavation method and the jacking method. Among them, when the shield method is used to construct the introduced water intake tunnel, due to the small space of the offshore forebay, the starting mechanism of the shield machine is usually large and complex, and the installation space of the offshore forebay is insufficient. Therefore, an additional starting well is usually excavated in the offshore area, and the shield machine is started through the starting well.

[0004] The excavation of an additional launching well requires large-scale excavation and backfilling of the ground, which involves a large amount of earthwork and occupies and damages a lot of land resources. Therefore, there is an urgent need for a launching structure that can be set in the limited space of an offshore forebay. Summary of the invention

[0005] In order to reduce the occupation and damage to land resources in offshore water intake projects, the present application provides an offshore forebay limited space shield starting structure and construction method.

[0006] In the first aspect, the present application provides an offshore forebay limited space shield starting structure, which adopts the following technical solution: A shield starting structure in a limited space of an offshore forebay comprises a tunnel starting component, a reaction frame and an excavation mechanism, wherein the tunnel starting component comprises a steel sleeve and a semi-ring segment, wherein the steel sleeve is pre-buried and installed in the starting tunnel, and the length of the steel sleeve passing through the starting tunnel is between 45 cm and 55 cm, and the semi-ring segment is installed on the side of the steel sleeve away from the starting tunnel; the reaction frame is arranged on the side of the semi-ring segment away from the steel sleeve; the excavation mechanism comprises a winch and a flatbed car, wherein the flatbed car is used to carry slag, and the winch is used to pull the flatbed car out of the starting tunnel.

[0007] By adopting the above technical solution, the steel sleeve between 45 cm and 55 cm out of the launching hole is convenient for reducing the occupation of the space in the offshore forebay by the launching structure, and the setting of the half-ring segment is convenient for realizing the stable support of the initial stage of the shield machine on the premise of occupying a small space in the offshore forebay, which is convenient for ensuring the stability during the construction of the tunnel portal. The above settings of the steel sleeve and the half-ring segment effectively reduce the occupation of the space in the offshore forebay, which is convenient for directly excavating the water intake tunnel with the offshore forebay as the launching shaft, thus helping to improve the construction efficiency and reduce the occupation and damage of land resources due to large-area excavation and backfilling in the offshore water intake project. The winch is convenient for quickly transporting the muck during the tunneling process out of the excavation tunnel by driving the flatbed truck.

[0008] Optionally, negative ring segments are arranged in the launching hole. One end of the negative ring segment is located outside the launching hole and is fixedly provided with a steel backrest, and the steel backrest and the half-ring segment are fixed by grouting.

[0009] By adopting the above technical solution, the setting of the steel backrest is convenient for providing a more stable supporting force during the initial tunneling of the shield machine, thus ensuring that the shield machine tunnels smoothly and accurately along the designed axis.

[0010] Optionally, fixed diagonal braces are arranged on both sides of the half-ring segment.

[0011] By adopting the above technical solution, the setting of the fixed diagonal braces is beneficial to further ensure the stability of the position where the half-ring segment is located, thus further ensuring the supporting stability of the initial stage of the shield machine.

[0012] Optionally, the reaction frame includes a frame body, a diagonal brace assembly and a counter brace assembly. The frame body is installed on the side of the half-ring segment away from the steel sleeve. The diagonal brace assembly includes a number of inclined supporting diagonal braces, and the supporting diagonal braces are located on the side of the frame body away from the half-ring segment and are used to support the frame body; the counter brace assembly includes a counter brace frame and a counter brace pipe. The counter brace frame is fixed to the side wall of the offshore forebay, and one end of the counter brace pipe is installed on the counter brace frame and the other end is installed on the frame body.

[0013] By adopting the above technical solution, the setting of the supporting diagonal braces is convenient for transmitting the reaction force received by the frame body to the bottom of the offshore forebay, and the setting of the counter brace pipe and the counter brace frame is convenient for transmitting the reaction force received by the frame body to the side wall of the offshore forebay, thus being beneficial to fully ensuring the structural firmness of the reaction frame.

[0014] Optionally, the muck removal mechanism further includes a muck removal guide rail, which is installed in the launching hole and arranged along the extension direction of the launching hole. The flatbed truck is slidably matched with the muck removal guide rail, and the flatbed truck is provided with a clamping mechanism fixed to the muck removal guide rail.

[0015] By adopting the above technical solution, the setting of the unearthed guide rail plays a further limiting role in the movement of the flatbed truck, which is beneficial to further ensure the stability of the flatbed truck during movement.

[0016] Optionally, the clamping mechanism includes two clamping plates and a driving component. The two clamping plates are respectively located on both sides of the unearthed guide rail, and the driving component is used to drive the two clamping plates to move towards or away from each other.

[0017] By adopting the above technical solution, the driving component drives the two clamping plates to move towards each other to clamp the unearthed guide rail, thereby fixing the position of the flatbed truck. It is convenient and fast, and is conducive to ensuring the movement stability of the flatbed truck in case of large slopes, with strong applicability.

[0018] Optionally, the driving component includes a clamping mounting seat, a clamping telescopic cylinder and a clamping rotating member. The clamping mounting seat is fixedly installed on the flatbed truck, the clamping telescopic cylinder is vertically installed on the clamping mounting seat, there are two clamping rotating members which are both rotatably installed on the clamping mounting seat, the output end of the clamping telescopic cylinder is fixedly provided with two driving rods, and two strip-shaped driving grooves are respectively formed in the two clamping rotating members. The two driving rods are respectively slidably matched in the two strip-shaped driving grooves; the two clamping plates are both slidably matched with the clamping mounting seat, two strip-shaped chutes are respectively formed in the two rotating members, and two clamping slide rods are fixedly installed on the two clamping plates. The two clamping slide rods are respectively slidably matched in the two strip-shaped chutes.

[0019] By adopting the above technical solution, when the clamping telescopic cylinder drives the movement of its output end, the driving rod slides in the strip-shaped driving groove to drive the clamping rotating member to rotate, and then drives the two clamping plates to move towards or away from each other through the cooperation of the strip-shaped chute and the clamping slide rod, which is convenient and fast.

[0020] Optionally, a clamping fixing plate is fixedly installed at the output end of the clamping telescopic cylinder, the driving rod is fixedly installed on the clamping fixing plate, and a vertically arranged clamping guide rod is fixedly installed on the clamping mounting seat. The clamping guide rod passes through and is slidably matched with the clamping fixing plate.

[0021] By adopting the above technical solution, the setting of the clamping guide rod plays a further limiting role in the sliding of the clamping fixing plate, which is beneficial to fully ensure the stability of the clamping telescopic cylinder finally driving the two clamping plates to move towards or away from each other.

[0022] Optionally, the flatbed truck includes a vehicle body base and a vehicle body bearing part. The vehicle body bearing part is used for bearing the muck. The vehicle body base is provided with an adjusting assembly. The adjusting assembly includes an adjusting motor, an adjusting lead screw, and an adjusting slider. The vehicle body base is provided with an adjusting chute extending along the width direction of the soil outlet guide rail. The adjusting slider is fixedly installed on the vehicle body bearing part and is slidably matched with the adjusting chute. The adjusting lead screw is rotatably installed on the vehicle body base. The adjusting motor is used to drive the adjusting lead screw to rotate. The adjusting lead screw penetrates along the width direction of the soil outlet guide rail and is threadedly matched with the adjusting slider.

[0023] By adopting the above technical solution, when the adjusting motor drives the adjusting lead screw to rotate, the adjusting slider moves along the width direction of the soil outlet guide rail due to the threaded fit with the adjusting lead screw and the limiting effect of the adjusting chute, so as to facilitate the adjustment of the position of the vehicle body bearing part, facilitate the avoidance of external objects during soil excavation, and has strong applicability.

[0024] In a second aspect, the present application provides a construction method for a shield starting structure in a limited space of an offshore forebay, adopting the following technical solution: A construction method for a shield starting structure in a limited space of an offshore forebay includes the following specific steps: S1, excavate a starting hole in the offshore forebay and pre-embed and install a steel sleeve. The length of the installed steel sleeve extending out of the starting hole is between 45 cm and 55 cm; S2, install a negative ring segment in the starting hole. One end of the installed negative ring segment is located outside the starting hole; S3, fixedly install a steel backrest at one end of the negative ring segment located outside the starting hole, and install a half-ring segment on the side of the steel backrest away from the negative ring segment; S4, fix the steel backrest and the half-ring segment by grouting; S5, install a reaction frame, and stably support the frame body through a diagonal bracing assembly and an opposing bracing assembly; S6, install a winch. After the shield machine starts tunneling construction, lay a soil outlet guide rail in the starting hole along the tunneling direction of the shield machine, and make the flatbed truck installed on the steel wire rope of the winch slidably cooperate with the soil outlet guide rail.

[0025] By adopting the above technical solution, the setting of the steel sleeve and the half-ring segment effectively reduces the occupation of the space in the offshore forebay, facilitates the direct excavation of the water intake tunnel with the offshore forebay as the starting shaft, thereby helping to improve the construction efficiency and reduce the occupation and damage of land resources caused by large-area excavation and backfilling in the offshore water intake project. Moreover, the winch facilitates the rapid transportation of the muck during the tunneling process of the shield machine out of the excavation tunnel through the drive of the flatbed truck, and the construction efficiency is relatively high.

[0026] In summary, the present application includes at least one of the following beneficial technical effects: 1. The setting of the sleeve and the semi-circular segment effectively reduces the occupation of the space in the offshore forebay, facilitating the direct excavation of the water intake tunnel with the offshore forebay as the launching shaft, which is conducive to improving the construction efficiency and reducing the occupation and damage of land resources caused by large-area excavation and backfilling in the offshore water intake project.

[0027] 2. The setting of the steel backrest facilitates the provision of a more stable supporting force during the initial tunneling of the shield machine, thus ensuring that the shield machine tunnels smoothly and accurately along the designed axis.

[0028] 3. The setting of the supporting diagonal brace facilitates the transfer of the reaction force received by the frame to the bottom of the offshore forebay, and the setting of the cross brace pipe and the cross brace frame facilitates the transfer of the reaction force received by the frame to the side wall of the offshore forebay, which is conducive to fully ensuring the structural firmness of the reaction frame. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present application.

[0030] Figure 2 It is a schematic diagram of the main structure of the clamping mechanism in an embodiment of the present application.

[0031] Figure 3 It is a partial sectional view schematic diagram of the flatbed truck in an embodiment of the present application.

[0032] DESCRIPTION OF THE REFERENCE NUMERALS: 1. Steel sleeve; 2. Semi-circular segment; 3. Launching hole; 4. Negative segment; 5. Steel backrest; 6. Fixed diagonal brace; 7. Reaction frame; 701. Frame body; 702. Supporting diagonal brace; 703. Cross brace frame; 704. Cross brace pipe; 8. Winch; 9. Flatbed truck; 901. Vehicle body base; 902. Vehicle body bearing part; 10. Excavated soil guide rail; 11. Bearing groove; 12. Adjusting motor; 13. Adjusting screw rod; 14. Adjusting slider; 15. Adjusting chute; 16. Clamping plate; 17. Clamping mounting seat; 18. Clamping telescopic cylinder; 19. Clamping rotating part; 191. First rotating part; 192. Second rotating part; 20. Clamping fixing plate; 21. Clamping guide rod; 22. Driving rod; 23. Strip-shaped driving groove; 24. Strip-shaped chute; 25. Clamping slide rod. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The following is a further detailed description of the present application in conjunction with the attached Figures 1-3 drawings.

[0034] An embodiment of the present application discloses a shield launching structure in a limited space of an offshore forebay.

[0035] Refer to Figure 1, the shield launching structure in the limited space of the offshore forebay includes a portal launching assembly, a reaction frame 7, and an earth excavation mechanism. Among them, the portal launching assembly includes a steel sleeve 1 and a half-ring segment 2. The steel sleeve 1 is fixedly installed through embedding at the launching portal 3, and the launching portal 3 is located within the area surrounded by the steel sleeve 1. After the steel sleeve 1 is installed, the length protruding through the launching portal 3 is between 45 cm and 55 cm. In the embodiment of the present application, the length of the steel sleeve 1 protruding through the launching portal 3 is 50 cm.

[0036] Continue to refer to Figure 1 , a number of negative-ring segments 4 are arranged in the launching portal 3. Among them, one end of the negative-ring segment 4 near the launching portal 3 is located outside the launching portal 3 and is fixedly provided with a steel backrest 5 through bolts. The half-ring segment 2 is installed on the side of the steel sleeve 1 away from the launching portal 3. Specifically, in the embodiment of the present application, the steel backrest 5 adopts double-pitch 70# "H" steel, and the steel backrest 5 and the half-ring segment 2 are fixed by grouting, that is, cement mortar (or concrete) is poured into the gap between the steel backrest 5 and the half-ring segment 2 to make the stressed half-ring segment 2 uniform and the ring surface flat. Fixed inclined braces 6 are arranged on both sides of the half-ring segment 2. One end of the fixed inclined brace 6 is fixedly installed on the half-ring segment 2, and the other end is installed on the bottom wall of the offshore forebay to further ensure the stability of the position of the half-ring segment 2.

[0037] Continue to refer to Figure 1 , the reaction frame 7 is arranged on the side of the half-ring segment 2 away from the steel sleeve 1. Specifically, the reaction frame 7 includes a frame body 701, a diagonal brace assembly, and an opposing brace assembly. Among them, the frame body 701 is installed on the side of the half-ring segment 2 away from the steel sleeve 1. The diagonal brace assembly includes a number of inclined support braces 702. Each support brace 702 is located on the side of the frame body 701 away from the half-ring segment 2, and one end of each support brace 702 is fixedly installed on the frame body 701, and the other end abuts against the bottom wall of the offshore forebay, so that the support brace 702 realizes the support of the frame body 701.

[0038] Continue to refer to Figure 1 , the opposing brace assembly includes an opposing brace frame 703 and an opposing brace pipe 704. Among them, there are two opposing brace frames 703. The two opposing brace frames 703 are respectively located on the side of the frame body 701 close to and away from the launching portal 3. The two opposing brace frames 703 are fixedly installed on the side wall of the offshore forebay (the side wall is not shown). In the embodiment of the present application, there are two groups of opposing brace pipes 704 corresponding to the opposing brace frames 703. Each group of opposing brace pipes 704 has two. One end of each group of two opposing brace pipes 704 is installed on the opposing brace frame 703, and the other end is installed on the frame body 701 to realize further support and fixation of the frame body 701. The setting of the support brace 702 facilitates the transfer of the reaction force received by the frame body 701 to the bottom of the offshore forebay. The setting of the opposing brace pipe 704 and the opposing brace frame 703 facilitates the transfer of the reaction force received by the frame body 701 to the side wall of the offshore forebay, which is conducive to fully ensuring the structural firmness of the reaction frame 7.

[0039] Reference Figure 1 and Figure 2 As shown in Figure 2 and Figure 1 , the soil excavation mechanism includes a winch 8, a flatbed truck 9 and soil excavation guide rails 10. Among them, the soil excavation guide rails 10 are installed in the starting hole 3 and arranged along the extension direction of the starting hole 3. One end of the soil excavation guide rails 10 extends to one end of the semi-circular segment 2 away from the starting hole 3. The longitudinal section of the soil excavation guide rails 10 is T-shaped. The flatbed truck 9 is slidably matched with the soil excavation guide rails 10, so that the soil excavation guide rails 10 play a further limiting role in the movement of the flatbed truck 9, thus fully ensuring the stability of the flatbed truck 9 during movement.

[0040] Reference Figure 1 and Figure 3 Specifically, the flatbed truck 9 includes a vehicle body base 901 and a vehicle body bearing part 902. The vehicle body base 901 is installed at one end of the steel wire rope of the winch 8, and the vehicle body base 901 is slidably matched with the soil excavation guide rails 10. The vehicle body bearing part 902 is arranged on the top of the vehicle body base 901, and a bearing groove 11 is opened at the top of the vehicle body bearing part 902 for bearing the muck. The vehicle body base 901 is provided with an adjusting assembly. The adjusting assembly includes an adjusting motor 12, an adjusting lead screw 13 and an adjusting slider 14. An adjusting chute 15 extending along the width direction of the soil excavation guide rails 10 is opened at the top of the vehicle body base 901. The adjusting slider 14 is fixedly installed at the bottom of the vehicle body bearing part 902 and is slidably matched in the adjusting chute 15. The adjusting lead screw 13 is rotatably installed on the vehicle body base 901. The adjusting lead screw 13 passes through and is threadedly matched with the adjusting slider 14 along the width direction of the soil excavation guide rails 10. The adjusting motor 12 is installed on one side of the vehicle body bearing part 902, and the adjusting lead screw 13 is fixedly installed at the output end of the adjusting motor 12, so that the adjusting motor 12 is used to drive the adjusting lead screw 13 to rotate, so as to realize the adjustment of the position of the vehicle body bearing part 902 by driving the rotation of the adjusting lead screw 13 by the adjusting motor 12, and it is convenient to avoid external objects during soil excavation.

[0041] Reference Figure 1 and Figure 2 In order to further ensure the stability of the flatbed truck 9 during movement, the adjusting base is also provided with a clamping mechanism. There are two groups of soil excavation guide rails 10 and the clamping mechanism. Specifically, the clamping mechanism includes two clamping plates 16 and a driving assembly. Among them, the two clamping plates 16 are respectively located on both sides of the soil excavation guide rails 10. The driving assembly is used to drive the two clamping plates 16 to move towards or away from each other. When the two clamping plates 16 move towards each other to a state of tightly pressing the soil excavation guide rails 10, the position of the flatbed truck 9 is fixed.

[0042] Reference Figure 2, specifically, the driving assembly includes a clamping mounting seat 17, a clamping telescopic cylinder 18, and a clamping rotating member 19. The clamping mounting seat 17 is fixedly installed on the flatbed truck 9. The clamping telescopic cylinder 18 is vertically installed on the clamping mounting seat 17. A clamping fixing plate 20 is fixedly installed at the output end of the clamping telescopic cylinder 18, so that the clamping telescopic cylinder 18 drives the clamping fixing plate 20 to move in the vertical direction. Two vertically arranged clamping guide rods 21 are fixedly installed on the clamping mounting seat 17. The two clamping guide rods 21 are respectively located on both sides of the clamping telescopic cylinder 18. The two clamping guide rods 21 penetrate through and are slidably matched with the clamping fixing plate 20 to further limit the clamping fixing plate 20, thereby further ensuring the stability of the clamping fixing plate 20 during movement.

[0043] Continue to refer to Figure 2 , two driving rods 22 are fixedly installed on one side of the clamping fixing plate 20. There are two clamping rotating members 19, and both are rotatably installed on the clamping mounting seat 17. The clamping rotating member 19 includes a first rotating portion 191 and a second rotating portion 192 fixedly installed at one end of the first rotating portion 191. The rotation point of the clamping rotating member 19 is located at the connection between the first rotating portion 191 and the second rotating portion 192. Two strip-shaped driving grooves 23 are respectively formed in the two first rotating portions 191. The two driving rods 22 are respectively slidably matched in the two strip-shaped driving grooves 23.

[0044] Continue to refer to Figure 2 , two strip-shaped sliding grooves 24 are respectively formed in the two second rotating portions 192. The two clamping plates 16 are both slidably matched with the clamping mounting seat 17 along the width direction of the excavation guide rail 10, and two clamping sliding rods 25 are fixedly installed on the two clamping plates 16. The two clamping sliding rods 25 are respectively slidably matched in the two strip-shaped sliding grooves 24. When the clamping telescopic cylinder 18 drives the movement of its output end, the driving rod 22 slides in the strip-shaped driving groove 23 to drive the clamping rotating member 19 to rotate. Subsequently, through the cooperation of the strip-shaped sliding groove 24 and the clamping sliding rod 25, the two clamping plates 16 are driven to move towards each other or away from each other, facilitating the quick fixation or non-fixation of the position where the flatbed truck 9 is located.

[0045] The implementation principle of the embodiment of this application is as follows: The steel sleeve 1 penetrating out of the starting hole between 345 cm and 55 cm in the offshore forebay occupies a relatively small space in the offshore forebay. The setting of the semi-circular segment 2 also facilitates the stable support of the initial stage of the shield machine under the premise of occupying a relatively small space in the offshore forebay, ensuring the stability during the construction of the tunnel portal. That is, the above settings of the steel sleeve 1 and the semi-circular segment 2 effectively reduce the occupation of the space in the offshore forebay, thus facilitating the direct excavation of the water intake tunnel with the offshore forebay as the starting shaft, which is conducive to improving the construction efficiency and reducing the occupation and damage of land resources due to large-area excavation and backfilling in the offshore water intake project. In addition, the driving of the flatbed truck 9 by the winch 8 through the excavation guide rail 10 facilitates the rapid and stable transportation of the muck during the tunneling process out of the excavation tunnel.

[0046] The embodiment of the present application also discloses a construction method for a shield starting structure in a limited space of an offshore forebay. The construction method for the shield starting structure in the limited space of the offshore forebay specifically includes the following steps: S1, excavate a starting hole 3 in the offshore forebay, and pre-embed and install a steel sleeve 1. The length of the installed steel sleeve 1 protruding out of the starting hole 3 is between 45 cm and 55 cm. In the embodiment of the present application, the length of the installed steel sleeve 1 protruding out of the starting hole 3 is 50 cm.

[0047] S2, install the negative ring segment 4 in the starting hole 3. One end of the installed negative ring segment 4 is located outside the starting hole 3.

[0048] S3, fixedly install a steel backrest 5 at one end of the negative ring segment 4 located outside the starting hole 3, and install a half-ring segment 2 on the side of the steel backrest 5 away from the negative ring segment 4.

[0049] S4, fix it through grouting between the steel backrest 5 and the half-ring segment 2.

[0050] S5, install a reaction frame 7, and stably support the frame body 701 through a diagonal bracing assembly and a cross bracing assembly.

[0051] S6, install a winch 8. After the shield machine starts tunneling construction, lay an earth excavation guide rail 10 in the starting hole 3 along the tunneling direction of the shield machine, and make the flatbed truck 9 installed on the steel wire rope of the winch 8 slide and cooperate with the earth excavation guide rail 10.

[0052] The implementation principle of the construction method for the shield starting structure in the limited space of the offshore forebay in the embodiment of the present application is as follows: The setting of the steel sleeve 1 and the half-ring segment 2 effectively reduces the occupation of the space in the offshore forebay, facilitating the direct excavation of the water intake tunnel with the offshore forebay as the starting shaft, which is beneficial to improving the construction efficiency and reducing the occupation and damage of land resources due to large-area excavation and backfilling in the offshore water intake project. Moreover, the winch 8 facilitates the rapid transportation of the muck during the tunneling process of the shield machine out of the excavation tunnel through the drive of the flatbed truck 9, and the construction efficiency is relatively high.

[0053] The above are all the preferred embodiments of the present application. The protection scope of the present application is not limited by this. Therefore, all equivalent changes made according to the structure, shape, and principle of the present application should be covered within the protection scope of the present application.

Claims

1. An offshore forebay limited space shield starting structure, characterized by: The invention comprises a tunnel opening starting component, a reaction frame (7) and an excavation mechanism, wherein the tunnel opening starting component comprises a steel sleeve (1) and a semi-ring pipe segment (2), wherein the steel sleeve (1) is pre-buried and installed in the starting tunnel opening (3), wherein the length of the steel sleeve (1) passing through the starting tunnel opening (3) is between 45 cm and 55 cm, and the semi-ring pipe segment (2) is installed on a side of the steel sleeve (1) away from the starting tunnel opening (3); the reaction frame (7) is arranged on a side of the semi-ring pipe segment (2) away from the steel sleeve (1); and the excavation mechanism comprises a winch (8) and a flatbed car (9), wherein the flatbed car (9) is used to carry the slag, and the winch (8) is used to pull the flatbed car (9) out of the starting tunnel opening (3).

2. According to claim 1, a shield starting structure with limited space in an offshore forebay, characterized in that: A negative ring segment (4) is arranged in the starting tunnel opening (3), one end of the negative ring segment (4) is located outside the starting tunnel opening (3) and is fixedly provided with a steel backrest (5), and the steel backrest (5) is fixed to the semi-ring segment (2) by grouting.

3. According to claim 2, a shield starting structure with limited space in an offshore forebay is characterized by: Fixed diagonal braces (6) are provided on both sides of the semi-ring segment (2).

4. The offshore forebay limited space shield starting structure according to claim 1 is characterized by: The reaction frame (7) comprises a frame body (701), a diagonal brace assembly and a brace assembly. The frame body (701) is installed on the side of the semi-ring segment (2) away from the steel sleeve (1). The diagonal brace assembly comprises a plurality of inclined supporting diagonal braces (702). The supporting diagonal braces (702) are located on the side of the frame body (701) away from the semi-ring segment (2) and are used to support the frame body (701). The brace assembly comprises a brace frame (703) and a brace pipe (704). The brace frame (703) is fixed to the side wall of the offshore forebay. One end of the brace pipe (704) is installed on the brace frame (703) and the other end is installed on the frame body (701).

5. The offshore forebay limited space shield starting structure according to claim 1 is characterized by: The excavation mechanism further comprises an excavation guide rail (10), the excavation guide rail (10) being installed in the starting tunnel opening (3) and arranged along the extension direction of the starting tunnel opening (3), the flatbed car (9) being slidably matched with the excavation guide rail (10), and the flatbed car (9) being provided with a locking mechanism fixed to the excavation guide rail (10).

6. The offshore forebay limited space shield starting structure according to claim 5, characterized in that: The locking mechanism comprises two locking plates (16) and a driving assembly, wherein the two locking plates (16) are respectively located on two sides of the excavation guide rail (10), and the driving assembly is used to drive the two locking plates (16) to move in a direction of approaching or moving away from each other.

7. The offshore forebay limited space shield starting structure according to claim 6 is characterized by: The driving assembly comprises a positioning mounting seat (17), a positioning telescopic cylinder (18) and a positioning rotating member (19); the positioning mounting seat (17) is fixedly mounted on the flatbed vehicle (9); the positioning telescopic cylinder (18) is vertically mounted on the positioning mounting seat (17); two positioning rotating members (19) are provided and are both rotatably mounted on the positioning mounting seat (17); two driving rods (22) are fixedly provided at the output end of the positioning telescopic cylinder (18); The positioning rotating member (19) is provided with a strip driving groove (23), and the two driving rods (22) are respectively slidably matched in the two strip driving grooves (23); the two positioning plates (16) are respectively slidably matched in the positioning mounting seat (17), the two rotating members are provided with a strip sliding groove (24), the two positioning plates (16) are respectively fixedly installed with a positioning slide rod (25), and the two positioning slide rods (25) are respectively slidably matched in the two strip sliding grooves (24).

8. The offshore forebay limited space shield starting structure according to claim 7 is characterized by: A locking plate (20) is fixedly mounted on the output end of the locking telescopic cylinder (18), the driving rod (22) is fixedly mounted on the locking plate (20), and a vertically arranged locking guide rod (21) is fixedly mounted on the locking mounting seat (17), the locking guide rod (21) penetrates and slidably engages with the locking plate (20).

9. The offshore forebay limited space shield starting structure according to claim 5, characterized in that: The flatbed vehicle (9) comprises a vehicle body base (901) and a vehicle body bearing portion (902), wherein the vehicle body bearing portion (902) is used for bearing slag, and the vehicle body base (901) is provided with an adjustment component, wherein the adjustment component comprises an adjustment motor (12), an adjustment screw rod (13) and an adjustment slider (14), and the vehicle body base (901) is provided with an adjustment slide groove (15) extending along the width direction of the excavation guide rail (10), and the adjustment slider (14) is fixedly mounted on the vehicle body bearing portion (902) and slidably engaged with the adjustment slide groove (15), and the adjustment screw rod (13) is rotatably mounted on the vehicle body base (901), and the adjustment motor (12) is used for driving the adjustment screw rod (13) to rotate, and the adjustment screw rod (13) is penetrated along the width direction of the excavation guide rail (10) and threadedly engaged with the adjustment slider (14).

10. A construction method for a limited space shield starting structure in an offshore forebay, characterized by: The method comprises the following specific steps: S1, excavating a starting hole (3) in an offshore forebay, and pre-buried and installed a steel sleeve (1), wherein the length of the installed steel sleeve (1) passing through the starting hole (3) is between 45 cm and 55 cm; S2, installing the negative ring segment (4) in the starting tunnel opening (3), wherein one end of the negative ring segment (4) is located outside the starting tunnel opening (3) after installation; S3, a steel backrest (5) is fixedly arranged at one end of the negative ring segment (4) outside the starting hole (3), and a half ring segment (2) is installed on the side of the steel backrest (5) away from the negative ring segment (4); S4, fixing the steel backrest (5) and the semi-ring segment (2) by grouting; S5, installing the reaction frame (7), and stably supporting the frame body (701) through the diagonal support assembly and the parallel support assembly; S6, installing a winch (8), laying an excavation guide rail (10) in the starting tunnel (3) along the excavation direction of the shield machine after the shield machine has started excavation construction, and making a flatbed car (9) installed on the wire rope of the winch (8) slide and cooperate with the excavation guide rail (10).

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