A method for constructing an integral high-altitude circular shield

Abstract

The present invention relates to the technical field of tunnel engineering, and specifically discloses a method for constructing an integral high-altitude circular shield plate. Based on the existing shield construction method, multiple improvements are made. A circular shield tunnel is adopted to replace the original rectangular jacking tunnel, thereby reducing the reliance on pre-processing of bedrock protrusions and avoiding road occupation during construction. A reserved pit is opened in the middle plate to construct a modular starting platform, thereby realizing the combination of permanent and temporary. While stably bearing the starting reaction force, the material waste and construction time investment of the temporary middle plate and full-floor scaffolding are eliminated. A split starting and full-process split excavation scheme is adopted, thereby eliminating the two hoisting constructions of the bridge frame and the trolley into and out of the well, and can adapt to complex construction conditions such as starting in a narrow space, receiving on a limited site, a short tunnel, and crossing an important road.

Description

Technical Field

[0001] The present invention relates to the field of tunnel engineering, and more particularly to a method for constructing an integral high-altitude circular shield. Background Art

[0002] With the acceleration of urbanization, the scale of subway construction continues to expand. Factors such as ground conditions, underground space environment, and surface site conditions are placing increasingly stringent demands on the technical and economic feasibility of subway construction. For example, limited construction space within subway stations makes it difficult to accommodate tunneling equipment and its supporting systems. Within the launching shaft, the heavy tunneling equipment and the significant starting reaction force necessitate the erection of a full-height scaffolding and even the construction of a temporary mid-slab as a shield launching platform, which is time-consuming and impacts the project schedule. Furthermore, the limited width of the receiving shaft prevents the complete lifting of the shield machine or trolley.

[0003] In the complex surrounding environment of the city, affected by the demolition of ground buildings (structures), the relocation of underground municipal pipelines, and the diversion of ground traffic, it is often difficult to provide suitable site space and starting shaft width for the initial excavation of stations. Among the many subway construction scenarios, the initial excavation of subway crossings is particularly difficult, especially the problem of bedrock protrusions invading the tunnel. The first reason is that the ground traffic volume is higher and construction cannot occupy the road. The vertical treatment of the ground needs to avoid pipelines, leaving blind spots. Therefore, the bedrock protrusion is difficult to be treated vertically on the ground; the second reason is that it is difficult to treat horizontally. When the rock strength is high, the posture and direction of the horizontal treatment are difficult to control; the third reason is that both treatment methods have the risk of disturbing the ground layer and causing secondary disturbance during the tunneling of the pipe jacking machine.

[0004] During current subway station construction, rectangular pipe jacking machines are primarily used for tunneling entrances and exits. Limited by the shape of the cutterhead, rectangular pipe jacking machines inevitably leave blind spots at the four corners of the rectangle during tunneling. When encountering harder rock formations, relying solely on the machine's own thrust may make it difficult to control tunneling deviations and may even lead to serious consequences such as the pipe becoming stuck or equipment becoming trapped. Summary of the Invention

[0005] The present invention aims to overcome at least one of the shortcomings of the above-mentioned existing technologies and provide an integral high-altitude plate circular shield construction method, which can effectively utilize the construction site and underground space, eliminate the rock layer processing steps, reduce the excavation blind spots, and thus replace the existing rectangular jacking machine solution; it can also simplify the construction of the shield starting platform, reduce the excavation construction risk of the subway station, and shorten the construction period.

[0006] The technical solution adopted by the present invention is to provide an integral high-altitude plate circular shield construction method, comprising the following steps:

[0007] S1. Arrange the construction site and construct the starting well. A reserved pit is set in the lower middle plate of the starting well.

[0008] S2. Hoisting construction materials into the starting shaft through the reserved pit to construct a high-altitude plate shield starting platform;

[0009] S3. Hoist the various components of the shield machine into the starting shaft, assemble the shield machine, assemble the bridge and trolley on the ground, connect the bridge and trolley to the shield machine through pipelines, debug the shield machine, and install the negative ring segments;

[0010] S4, split start, the whole process adopts split excavation, and the connection between the shield machine and the bridge and trolley is ensured by extending the pipeline;

[0011] S5. Install the shield receiving bracket, receive the shield machine out of the hole, and hoist the shield machine out of the receiving shaft;

[0012] S6. Dismantle the starting platform of the high-altitude middle plate shield, backfill the reserved pit of the lower middle plate, and reconstruct the upper middle plate.

[0013] The present invention provides an integrated high-altitude circular shield construction system and method, which improves upon existing shield construction methods by making the following improvements. First, a circular shield tunnel is used instead of the existing rectangular jacking tunnel, reducing excavation blind spots, reducing reliance on pre-treatment of bedrock protrusions, and avoiding road occupation during construction. Second, the entire mid-plate in the launch shaft is not removed. Instead, the majority of the lower mid-plate structure is retained, and only a reserved pit, less long than the launch frame and less wide than the diameter of the shield machine, is excavated to construct a modular launch platform. This achieves a combination of permanent and temporary structures, where the permanent mid-plate and temporary steel platform share the load and stably withstand the launch reaction force. This also eliminates the material waste and time investment associated with constructing temporary mid-plates and full-scale scaffolding. The pit design also simplifies subsequent shield machine installation steps, avoiding repeated adjustments to the mid-plate structure. Finally, a split launch and full-scale split excavation scheme is adopted, eliminating the need for the bridge and trolley to be hoisted down and out of the shaft twice. This makes it suitable for complex construction conditions such as launch in narrow spaces, limited site reception, short tunnels, and underpasses of important roads.

[0014] Furthermore, the distance between the starting shaft and the receiving shaft is no more than twice the total length of the trolley. In the embodiment of excavating a street crossing tunnel, the present invention adopts a split starting and full-length split excavation scheme, which avoids the two-time hoisting construction of the bridge frame and the trolley into and out of the shaft. It not only reduces the downtime waiting time of the shield machine in the process of passing under important roads and reduces construction risks, but also shortens the construction period by about 5 days, making it suitable for short tunnel excavation. This scheme also solves the problem of limited space inside the station, and can adapt to the shield starting and excavation in the narrow station space, as well as the shield receiving in the limited ground space. Taking the street crossing of an urban rail transit station as an example, on the one hand, its receiving shaft is small in size, making it difficult to lift out the trolley. On the other hand, the overall length of the street crossing is limited, which can neither accommodate multiple trolleys nor bring about the side effect of reduced pumping pressure due to excessively long pipelines. Therefore, it is suitable to adopt a split starting and full-length split excavation scheme.

[0015] Furthermore, the width of the receiving shaft is smaller than the length of the trolley. If the receiving shaft is smaller than the trolley's length, once the trolley enters the launch shaft and follows the main shield machine, it cannot be hoisted out of the receiving shaft and must be towed back to the launch shaft and hoisted out, slowing the construction schedule. Therefore, when the receiving shaft is narrow, a split launch and full-scale split tunneling approach is suitable.

[0016] Furthermore, the long sides of the reserved pit are provided with a tongue and groove, which is equipped with a first steel rail for supporting the shield machine. The reserved pit matches the dimensions of the shield machine, and the tongue and rail provide a stable guide, providing stable support for the shield machine and reducing the risk of deviation during startup.

[0017] Furthermore, when multiple tunnels are excavated at the lower middle plate height, step S1 needs to open multiple corresponding reserved pits, and step S4 starts the shield machine alone in a reserved pit, while temporary supports are set horizontally in other reserved pits.

[0018] Furthermore, when excavating multiple tunnels in the same direction, the shield machines of different tunnels in step S4 can excavate simultaneously at different progress rates.

[0019] Furthermore, in step S5, if the receiving shaft is not wide enough, the shield machine is disassembled in the receiving shaft and then hoisted out. If the receiving shaft is less than the full length of the shield machine, after a portion of the shield machine has exited the hole, the shield machine is disassembled in the receiving shaft and hoisted out separately. The order of hoisting is cutterhead, screw machine, front shield, middle shield, and tail shield. The screw machine is disassembled and dragged back to the starting shaft for hoisting, and the rest are hoisted out in sequence in the receiving shaft.

[0020] Furthermore, the high-altitude plate shield starting platform includes a starting frame and a reaction frame. The starting frame is fixed on the station floor, the top of the starting frame is lower than the lower middle plate and is fixedly connected to the lower middle plate, and the reaction frame is arranged on the starting frame.

[0021] Furthermore, the reaction frame includes:

[0022] The steel ring is located on the side close to the shield machine and is used to directly withstand the impact of the shield tail of the shield machine;

[0023] A rear shield frame is provided on a side away from the shield machine and is fixedly connected to the steel ring;

[0024] The first diagonal brace is a structural beam connecting the backing frame and the upper middle plate;

[0025] The second diagonal brace connects the backing frame and the lower middle plate.

[0026] Furthermore, the number of the second diagonal braces is greater than that of the first diagonal braces. More diagonal braces diagonally downward are provided, thereby enhancing the support capacity of the shield machine for heavy loads, balancing the force, and preventing the platform from tilting due to uneven vertical loads.

[0027] Furthermore, the angle between the first and second diagonal braces and the horizontal plane is 20-25 degrees. This specific inclination angle optimizes the efficiency of horizontal force transmission, effectively offsetting frictional resistance during shield advancement, and preventing the reaction frame from floating due to the reaction force of the diagonal braces.

[0028] Furthermore, the originating frame includes:

[0029] The column has its lower end connected to the station floor and its upper end is lower than the lower middle plate;

[0030] The third diagonal brace is used to connect adjacent columns;

[0031] The plate layer is laid on the upper end of the column, with one edge closely attached to the station structure beam under the departure tunnel;

[0032] Multiple middle plate supports are located above two rows of columns on both sides of the shield direction, connected to the plate layer below and the lower middle plate above;

[0033] The shield machine bracket is laid on the plate layer, under the starting tunnel door, and between the top supports of the two rows of middle plates. The shield machine bracket is provided with a second steel rail.

[0034] The above-mentioned starting frame distributes the shield machine load to multiple columns in the vertical direction and to the lower middle plate in the horizontal direction; the components adopt a modular design, which helps to simplify the on-site construction process. The middle plate support is connected to the steel plate at the bottom and the lower middle plate at the top, realizing a permanent combination of the middle plate and the starting platform, jointly bearing the shield starting load, and being able to safely and stably support the shield starting. One edge of the steel plate is closely attached to the station structure beam under the starting tunnel portal to prevent the forward friction during the shield starting process from causing the starting platform to overturn forward as a whole. The second steel rail set on the shield machine bracket has a similar function to the first steel rail, providing stable guidance and reducing the risk of deviation when the shield machine is started.

[0035] Furthermore, the columns, the third diagonal brace, the plate layer, the middle plate support top and the shield machine bracket are connected by welding. The welding connection ensures the structural integrity and reduces safety risks.

[0036] Furthermore, the width-to-depth ratio of each weld in the welded connection should not be less than 1.1. Controlling the width-to-depth ratio avoids brittle fracture caused by excessively deep welds, enhances welding reliability, and improves the fatigue and impact resistance of the structure.

[0037] Furthermore, the plate layer includes an upper steel plate, a longitudinal and transverse frame, and a lower steel plate that are fixedly connected in sequence from top to bottom, which is beneficial to improving the overall rigidity.

[0038] Furthermore, the longitudinal and transverse frames include longitudinal steel beams and transverse steel beams, and the intersections of the longitudinal and transverse steel beams are both located above the columns, so that the pressure on the upper steel plate is more evenly transmitted to the lower steel plate, which is conducive to reducing the risk of local deformation.

[0039] Furthermore, the middle plate top support comprises a short steel pipe and / or a plurality of assembled I-beams, and the upper portion of the short steel pipe is connected to the I-beam, thereby achieving easy assembly and a stable structure.

[0040] Furthermore, the number of the second diagonal braces is greater than that of the first diagonal braces. More diagonal braces on the lower layer enhance the support capacity of the heavy load of the shield machine, balance the force, and prevent the platform from tilting due to uneven vertical load.

[0041] Furthermore, the first diagonal brace has an inclination angle of 20-25° to the horizontal plane. This specific inclination angle optimizes the efficiency of horizontal force transmission, effectively offsetting frictional resistance during shield advancement, and preventing the reaction frame from floating due to the reaction force of the diagonal brace.

[0042] The above-mentioned starting frame distributes the shield machine load to multiple columns in the vertical direction and to the lower middle plate in the horizontal direction; the components adopt a modular design, which helps to simplify the on-site construction process. The middle plate support is connected to the steel plate at the bottom and the lower middle plate at the top, realizing the permanent combination of the middle plate and the starting platform, jointly bearing the shield starting load, and being able to safely and stably support the shield starting. One edge of the steel plate is closely attached to the station structure beam under the starting tunnel portal, preventing the forward friction during the shield starting process from causing the starting platform to overturn forward as a whole. The second steel rail installed on the shield machine bracket has a similar function to the first steel rail, providing stable guidance and reducing the risk of deviation when the shield machine is started. The welded connection ensures the integrity of the structure and reduces safety risks.

[0043] Furthermore, the steel plate comprises an upper steel plate, a longitudinal and transverse frame and a lower steel plate which are fixedly connected in sequence from top to bottom. The layered steel plate and frame design can improve the overall rigidity.

[0044] Furthermore, the intersections of the longitudinal and transverse frames are all located above the columns, so that the pressure on the upper steel plate is more evenly transmitted to the lower steel plate, which is conducive to reducing the risk of local deformation.

[0045] Furthermore, the middle plate support comprises short steel pipes and / or spliced ​​I-beams, which are easy to assemble and have a stable structure.

[0046] Furthermore, the width-to-depth ratio of each weld in the welded connection should not be less than 1.1. Controlling the width-to-depth ratio avoids brittle fracture caused by excessively deep welds, enhances welding reliability, and improves the fatigue and impact resistance of the structure.

[0047] Furthermore, when excavating multiple tunnels at the height of the lower middle plate, multiple reserved pits need to be opened, and the shield machine starts separately in a reserved pit; during the starting and excavation process, steel pipes are arranged horizontally in other reserved pits as temporary support.

[0048] Furthermore, in step S5, when the receiving shaft is not wide enough, after a portion of the shield machine is removed from the hole, the shield machine is disassembled in the receiving shaft and hoisted out separately. Disassembling the shield machine when the receiving shaft is not wide enough solves the problem of insufficient hoisting space in traditional solutions.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] The present invention provides an integral high-altitude upper plate circular shield construction method, which makes multiple improvements on the basis of the existing shield construction method. A circular shield tunnel is adopted to replace the original rectangular jacking tunnel, reducing the dependence on advance treatment of bedrock protrusions and avoiding road construction. A reserved pit is opened in the middle plate to construct a modular starting platform, realizing the combination of permanent and temporary. While stably bearing the starting reaction force, the material waste and construction time investment of the temporary middle plate and full-floor scaffolding are saved. A split starting and full-process split excavation scheme is adopted to save the two hoisting constructions of the bridge and trolley into and out of the well, which can adapt to complex construction conditions such as starting in narrow space, limited site reception, short tunnel, and crossing important roads. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a longitudinal section of the high-altitude plate shield starting platform provided in Example 1.

[0052] Figure 2 This is a cross-sectional view of the high-altitude plate shield starting platform provided in Example 1.

[0053] Figure 3 This is a partially enlarged cross-sectional view of the high-altitude plate shield starting platform provided in Example 1.

[0054] Figure 4This is a top view of the vertical and horizontal skeletons above the columns of the high-altitude plate shield starting platform provided in Example 1.

[0055] Figure 5 This is a cross-sectional schematic diagram of the layout of the shield machine, bridge and trolley during the starting and excavation process of Example 1.

[0056] Figure 6 This is a schematic diagram of the temporary support for the right line pit when the left line starts.

[0057] Figure 7 This is the flow chart for hoisting the shield machine out of the receiving shaft: a. After the second-to-last ring segment is assembled, the cutterhead is removed and hoisted out; b. Move forward 400mm, assemble the last ring segment, remove the screw machine in the tunnel and drag it back; c. Remove the front shield and hoist it out; d. Move the middle shield and tail shield forward, disassemble and hoist them out.

[0058] Explanation of reference numerals: Bottom plate 110, lower middle plate 120, reserved pit 121, first rail 122, upper middle plate 130, starting portal 140, station structural beam 150, shield machine 160, cutterhead 161, front shield 162, middle shield 163, shield tail 164, screw machine 165, top plate 170, reaction frame 200, rear shield frame 210, first diagonal brace 220, second diagonal brace 230, starting frame 300, column 310, third diagonal brace 320, plate layer 330, longitudinal and transverse skeleton 331, middle plate support 340, short steel pipe 341, I-beam 342, shield machine bracket 350, second rail 351, temporary support 360. Pipeline 400, bridge and trolley 500. DETAILED DESCRIPTION

[0059] The drawings of the present invention are for illustrative purposes only and are not to be construed as limiting the present invention. In order to better illustrate the following embodiments, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; it is understandable to those skilled in the art that some well-known structures and their descriptions in the drawings may be omitted. Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which this application belongs. It should be noted that the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0060] The present invention will now be further described with reference to specific examples. The following examples are intended only to illustrate the present invention but are not intended to limit the present invention. The tools, building materials, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial sources.

[0061] Example 1

[0062] like Figures 1 to 7 As shown, this embodiment provides a method for constructing an integral high-altitude circular shield, including the following steps:

[0063] S1. Arrange the construction site and construct the starting shaft. According to the size of the shield machine, open a reserved pit 121 in the lower middle plate 120;

[0064] S2. Hoisting construction materials into the starting shaft through the reserved pit 121 to construct a high-altitude plate shield starting platform;

[0065] S3. Lift the various components of the shield machine 160 into the launching shaft, assemble the shield machine 160, assemble the bridge and trolley 500 on the ground and connect the bridge and trolley 500 to the shield machine 160 via the pipeline 400, debug the shield machine 160, and install the negative ring segments;

[0066] S4, split start, using split excavation throughout the entire process, and ensuring the connection between the shield machine 160 and the bridge and trolley through the extension pipeline 400;

[0067] S5. Install the shield receiving bracket, the shield machine is taken out of the hole to receive the shield, and the shield main machine 160 is hoisted out of the receiving shaft;

[0068] S6. Dismantle the starting platform of the high-altitude middle plate shield, backfill the reserved pit 121 of the lower middle plate 120, and reconstruct the upper middle plate 130.

[0069] The present invention provides an integral high-altitude circular shield construction system and method, which makes the following improvements on the basis of the existing shield construction method. First, a circular shield tunnel is adopted to replace the original rectangular jacking tunnel, which reduces the excavation blind area, reduces the dependence on the advance treatment of bedrock protrusions, and avoids road construction. Secondly, instead of removing all the middle plates in the starting shaft, the majority of the structure of the lower middle plate 120 is retained, and only a reserved pit 121 with a length less than the starting frame 300 and a width less than the diameter of the shield machine is dug out to construct a modular starting platform, realizing the combination of permanent and temporary, that is, the permanent structure middle plate and the temporary structure steel platform jointly bear the load and stably bear the starting reaction force; at the same time, it saves the material waste and construction time investment of constructing temporary middle plates and full-floor scaffolding; the pit design also simplifies the subsequent shield machine installation steps, avoiding repeated adjustments to the middle plate structure. Finally, a split-start and full-length split-excavation scheme was adopted, with the rear accessories placed entirely on the top plate 170, eliminating the need for two hoisting operations of the bridge and trolley down and out of the well. This can adapt to complex construction conditions such as starting in narrow spaces, receiving in limited sites, short tunnels, and crossing important roads.

[0070] The distance between the starting shaft and the receiving shaft is no more than twice the total length of the trolley. In the embodiment of excavating a street crossing tunnel, the present invention adopts a split starting and full-length split excavation scheme, which avoids the two-time hoisting construction of the bridge frame and the trolley into and out of the shaft. It not only reduces the downtime waiting time of the shield machine in the process of crossing important roads, reduces construction risks, but also shortens the construction period by about 5 days, making it suitable for short tunnel excavation. This scheme also solves the problem of limited space inside the station, and can adapt to the shield starting and excavation in the narrow station space, as well as the shield receiving in the limited ground space. Taking the street crossing of an urban rail transit station as an example, on the one hand, its receiving shaft is small in size, making it difficult to lift out the trolley. On the other hand, the overall length of the street crossing is limited, which can neither accommodate multiple trolleys nor bring about the side effect of reduced pumping pressure due to excessively long pipelines. Therefore, it is suitable to adopt a split starting and full-length split excavation scheme.

[0071] The receiving shaft is narrower than the trolley's length. If the receiving shaft is narrower than the trolley's length, if the trolley enters the launch shaft and follows the shield machine 160, it cannot be hoisted out of the receiving shaft and must be towed back to the launch shaft and hoisted out, slowing the construction schedule. Therefore, when the receiving shaft is narrower, a split launch and full-scale split tunneling scheme is suitable.

[0072] The long side of the reserved pit 121 is provided with a tongue and groove, and the tongue and groove is provided with a first rail 122 for supporting the shield mainframe 160. Figure 3 The reserved pit 121 matches the size of the shield machine, and the groove and rail provide a stable guide, which not only provides stable support for the shield machine, but also reduces the risk of deviation when the shield machine starts.

[0073] When digging multiple tunnels at a height of 120° in the lower middle plate, Figure 6 As shown, step S1 requires opening a corresponding plurality of reserved pits 121 , and step S4 requires the shield machine 160 to start alone in a certain reserved pit 121 , while temporary supports 360 are laterally set in other reserved pits 121 .

[0074] When excavating multiple tunnels in the same direction, the shield machines of different tunnels can excavate simultaneously at different progress in step S4.

[0075] In step S5, when the receiving well width is insufficient, the shield machine 160 is disassembled in the receiving well and then hoisted out. Figure 7 As shown, when the width of the receiving well is smaller than the full length of the shield machine 160, after a part of the shield machine 160 comes out of the hole, the shield machine 160 is disassembled in the receiving well and hoisted out separately. The order of hoisting out is the cutter head 161, the screw machine 165, the front shield 162, the middle shield 163 and the shield tail 164. After the screw machine 165 is disassembled, it is dragged back to the starting well for hoisting out, and the others are hoisted out in the receiving well in sequence.

[0076] The high-altitude plate shield starting platform includes a starting frame 300 and a reaction frame 200. The starting frame 300 is fixed on the station floor 110. The top of the starting frame 300 is lower than the lower middle plate 120 and is fixedly connected to the lower middle plate 120. The reaction frame 200 is arranged on the starting frame 300.

[0077] like Figure 1 As shown, the reaction frame 200 includes:

[0078] The steel ring is located on the side close to the shield machine and is used to directly withstand the impact of the shield tail 164 of the shield machine;

[0079] The rear shield frame 210 is located on a side away from the shield machine and is fixedly connected to the steel ring;

[0080] The first diagonal brace 220 is a structural beam connecting the backing frame 210 and the upper middle plate 130;

[0081] The second diagonal brace 230 connects the rear shield frame 210 and the lower middle plate 120 .

[0082] The number of the second diagonal braces 230 is greater than the number of the first diagonal braces 220. More diagonal braces diagonally downward enhance the support capacity of the heavy load of the shield machine, balance the force, and prevent the platform from tilting due to uneven vertical load.

[0083] The first and second diagonal braces 220 and 230 are arranged at an angle of 20-25° to the horizontal plane. This specific inclination angle optimizes the efficiency of horizontal force transmission, effectively offsetting frictional resistance during shield advancement, and preventing the reaction frame 200 from floating upward due to the reaction force of the diagonal braces.

[0084] like Figure 2 and Figure 3 As shown, the originating frame 300 includes:

[0085] The column 310 has a lower end connected to the station floor 110 and an upper end lower than the lower middle plate 120;

[0086] A third diagonal brace 320 is used to connect adjacent columns 310;

[0087] The plate layer 330 is laid on the upper end of the column 310, with one edge closely attached to the station structure beam 150 under the starting tunnel 140;

[0088] Multiple middle plate supports 340 are located above the two rows of columns 310 on both sides of the shield direction, connected to the plate layer 330 below and the lower middle plate 120 above;

[0089] The shield machine bracket 350 is laid on the plate layer 330 , under the starting tunnel portal 140 , and between the two rows of middle plate supports 340 . The shield machine bracket 350 is provided with a second steel rail 351 .

[0090] The above-mentioned starting frame 300 disperses the shield machine load to multiple columns 310 in the vertical direction and to the lower middle plate 120 in the horizontal direction; the components adopt a modular design, which helps to simplify the on-site construction process. The middle plate support 340 is connected to the steel plate at the bottom and the lower middle plate 120 at the top, realizing a permanent combination of the middle plate and the starting platform, jointly bearing the shield starting load, and being able to safely and stably support the shield starting. One edge of the steel plate is closely attached to the station structure beam 150 under the starting portal 140, preventing the forward friction during the shield starting process from causing the starting platform to overturn forward as a whole. The second steel rail 351 set on the shield machine bracket 350 has a similar function to the first steel rail 122, providing stable guidance and reducing the risk of deviation when the shield machine is started.

[0091] The columns 310, the third diagonal braces 320, the plate layers 330, the middle plate supports 340 and the shield machine bracket 350 are connected by welding, which ensures structural integrity and reduces safety risks.

[0092] The width-to-depth ratio of each weld in the welded connection should not be less than 1.1. Controlling the width-to-depth ratio avoids brittle fracture caused by excessively deep welds, enhances welding reliability, and improves the fatigue and impact resistance of the structure.

[0093] The plate layer 330 includes an upper steel plate, a longitudinal and transverse frame 331 and a lower steel plate that are fixedly connected in sequence from top to bottom, which is beneficial to improving the overall rigidity.

[0094] The longitudinal and transverse skeleton 331 includes longitudinal steel beams and transverse steel beams, and the intersection of the longitudinal and transverse steel beams is located above the column 310. The pressure on the upper steel plate is more evenly transmitted to the lower steel plate, which is conducive to reducing the risk of local deformation.

[0095] The middle plate support 340 includes a short steel pipe 341 and / or a plurality of assembled I-beams 342, and the upper portion of the short steel pipe 341 is connected to the I-beam 342. The assembly is simple and the structure is stable.

[0096] The number of the second diagonal braces 230 is greater than the number of the first diagonal braces 220. More diagonal braces on the lower layer enhance the support capacity of the heavy load of the shield machine, balance the force, and prevent the platform from tilting due to uneven vertical load.

[0097] The first diagonal brace 220 has an inclination angle of 20-25° to the horizontal plane. This specific inclination angle optimizes the efficiency of horizontal force transmission, effectively offsetting friction during shield advancement, and preventing the reaction frame 200 from floating due to the reaction force of the diagonal brace.

[0098] The above-mentioned starting frame 300 distributes the shield machine load to multiple columns 310 in the vertical direction and to the lower middle plate 120 in the horizontal direction; the components adopt a modular design, which helps to simplify the on-site construction process. The middle plate support 340 is connected to the steel plate at the bottom and the lower middle plate 120 at the top, realizing a permanent combination of the middle plate and the starting platform, jointly bearing the shield starting load, and being able to safely and stably support the shield starting. One edge of the steel plate is closely attached to the station structure beam 150 under the starting portal 140, preventing the forward friction during the shield starting process from causing the starting platform to overturn forward as a whole. The second steel rail 351 set on the shield machine bracket 350 has a similar function to the first steel rail 122, providing stable guidance and reducing the risk of deviation when the shield machine is started. The welded connection ensures the integrity of the structure and reduces safety risks.

[0099] The steel plates include an upper steel plate, a longitudinal and transverse frame 331 and a lower steel plate that are fixedly connected in sequence from top to bottom. The layered steel plate and frame design can improve the overall rigidity.

[0100] The intersection points of the vertical and horizontal frames 331 are all located above the columns 310. Figure 4 The pressure on the upper steel plate is transmitted more evenly to the lower steel plate, which helps to reduce the risk of local deformation.

[0101] The middle plate support 340 includes a short steel pipe 341 and / or a spliced ​​I-beam 342. It is easy to assemble and has a stable structure.

[0102] The width-to-depth ratio of each weld in the welded connection should not be less than 1.1. Controlling the width-to-depth ratio avoids brittle fracture caused by excessively deep welds, enhances welding reliability, and improves the fatigue and impact resistance of the structure.

[0103] The embodiment provides an integral high-altitude circular shield construction method, which makes multiple improvements on the basis of the existing shield construction method. A circular shield tunnel is adopted to replace the original rectangular jacking tunnel, which reduces the dependence on the advance treatment of bedrock protrusions and avoids road construction. A reserved pit 121 is opened in the middle plate to construct a modular starting platform, realizing the combination of permanent and temporary. While stably bearing the starting reaction force, it saves the material waste and construction time investment of the temporary middle plate and full-floor scaffolding. The split starting and full-process split excavation scheme is adopted to save the two hoisting constructions of the bridge and the trolley into and out of the well, which can adapt to complex construction conditions such as starting in narrow space, limited site reception, short tunnel, and crossing important roads.

[0104] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the technical solutions of the present invention, and are not intended to limit the specific implementation methods of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A method for constructing an integral high-altitude circular shield tunnel, characterized in that: The following steps are involved: S1. Arrange the construction site and construct the starting well. A reserved pit is set in the lower middle plate of the starting well. S2. Hoisting construction materials into the starting shaft through the reserved pit to construct a high-altitude plate shield starting platform; S3. Hoist the various components of the shield machine into the starting shaft, assemble the shield machine, assemble the bridge and trolley on the ground, connect the bridge and trolley to the shield machine through pipelines, debug the shield machine, and install the negative ring segments; S4, split start, the whole process adopts split excavation, and the connection between the shield machine and the bridge and trolley is ensured by extending the pipeline; S5. Install the shield receiving bracket, receive the shield machine out of the hole, and hoist the shield machine out of the receiving shaft; S6. Dismantle the starting platform of the high-altitude plate shield, backfill the reserved pit of the lower middle plate, and reconstruct the upper middle plate; The long side of the reserved pit in step S1 is provided with a tongue and groove, and the tongue and groove is provided with a first rail for supporting the shield machine; When multiple tunnels are excavated at the lower middle plate height, multiple corresponding reserved pits need to be opened in step S1. In step S4, the shield machine starts alone in one of the reserved pits, and temporary supports are set horizontally in other reserved pits. The high-altitude plate shield starting platform includes a starting frame and a reaction frame. The starting frame is fixed to the station floor, the top of the starting frame is lower than the lower middle plate and is fixedly connected to the lower middle plate, and the reaction frame is installed on the starting frame; The reaction frame includes: a steel ring, which is provided on the side close to the shield machine and is used to directly withstand the impact of the shield tail of the shield machine; a rear shield frame, which is provided on the side away from the shield machine and is fixedly connected to the steel ring; a first diagonal brace, which connects the rear shield frame and the structural beam of the upper middle plate; a second diagonal brace, which connects the rear shield frame and the lower middle plate; The starting frame includes: a column, the lower end of which is connected to the bottom plate of the station, and the upper end is lower than the lower middle plate; a third diagonal brace for connecting adjacent columns; a plate layer, laid on the upper end of the column, with one edge closely attached to the station structure beam under the starting tunnel gate; multiple middle plate supports, located above two rows of columns on both sides of the shield direction, connected to the plate layer at the bottom and the lower middle plate at the top; a shield machine bracket, laid on the plate layer, under the starting tunnel gate, and between the two rows of middle plate supports, and a second steel rail is provided on the shield machine bracket.

2. The method for constructing an integral high-altitude circular shield according to claim 1, characterized in that: The distance between the starting well and the receiving well shall not exceed twice the total length of the trolley.

3. The method for constructing an integral high-altitude circular shield according to claim 1, characterized in that: The width of the receiving well is smaller than the length of the trolley.

4. The method for constructing an integral high-altitude circular shield according to claim 1, characterized in that: When excavating multiple tunnels in the same direction, the shield machines of different tunnels can excavate simultaneously at different progress in step S4.

5. The method for constructing an integral high-altitude circular shield according to any one of claims 1 to 3, characterized in that: In step S5, when the receiving well is not wide enough, the shield machine is disassembled in the receiving well and then hoisted out.

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