A steel shield tunnel cutterhead replacement space structure and construction method

Abstract

This invention provides a steel structure shield tunneling cutterhead replacement space structure and construction method. The structure comprises: a vertical steel casing arranged on the front axis of the tunnel boring machine (TBM) at a distance of 1.2m from the shield head; a horizontal steel box extending horizontally between the vertical steel casing and the TBM head, with one end connected to the vertical steel casing and the other end maintaining a 10cm gap from the TBM head, serving as a horizontal passage from the vertical steel casing to the TBM head; a corresponding under-box space excavated within the rock strata at the bottom of the lowest box; the vertical steel casing, multiple layers of horizontal steel boxes, and the under-box space together form the cutterhead replacement operation space for the TBM. This invention creates a safe, reliable, and easily constructed and dismantled cutterhead replacement operation space for TBMs, solving the problem of cutterhead replacement in tunnel boring machines.

Description

Technical Field

[0001] This invention relates to the field of tunnel boring machine (TBM) construction technology, and more specifically to a steel structure TBM cutterhead replacement space structure and construction method. Background Technology

[0002] Urban subway tunnels are often constructed using the shield tunneling method, with appropriate shield cutters selected based on soil conditions. In most cases, the tunnel boring machine (TBM) operates within soil strata, and under normal circumstances, the same type of cutter can complete the construction of one section. However, when geological conditions change, such as encountering rock strata where the original cutters are severely worn and unable to continue construction, it is necessary to replace them with high-strength cutters capable of cutting rock.

[0003] However, changing the cutting tools is technically challenging, and creating the necessary space for the operation is extremely difficult. Past methods primarily included: if the tunnel face was self-stabilizing or could be stabilized after pretreatment, atmospheric pressure cutting tool replacement was used; if the tunnel face was not self-stabilizing but met the airtightness requirements for pressurized operations, pressurized cutting tool replacement was used; if ground reinforcement was available, but the tunnel face was not self-stabilizing and could not meet the airtightness requirements for pressurized operations, ground reinforcement methods were used; if ground reinforcement was unavailable, but the tunnel face was not self-stabilizing and could not meet the airtightness requirements for pressurized operations, mortar replacement methods were used. If the stability of the soil and rock in front of the tunnel boring machine was extremely poor, and none of the aforementioned four methods could solve the problem, then only open-cut excavation from in front of the machine head was possible, resulting in a large workload and high costs. Summary of the Invention

[0004] This invention aims to solve the above-mentioned technical problems. To this end, it proposes a steel structure shield cutterhead replacement space structure and a corresponding construction method, which creates a safe, reliable, easy-to-construct and easy-to-dismantle safe operating space for shield machines to replace cutters, thus solving the problem of cutterhead replacement in tunnel shield machines.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A steel-structured shield tunnel cutterhead changing space structure, characterized by the following features:

[0007] A vertical steel casing is arranged on the axis in front of the tunnel shield machine at a distance of 1.2m from the shield head. The vertical steel casing is a multi-section splicing structure with a larger diameter at the top and a smaller diameter at the bottom. The section above the 1.0m height of the tunnel top is a large diameter section with a diameter of 2.0m, and the section below is a small diameter section with a diameter of 1.8m.

[0008] Mounting holes are made on the wall of the vertical steel casing facing the tunnel boring machine (TBM) at the position directly opposite the TBM, for mounting horizontal steel boxes. The horizontal steel boxes have up to two layers, with the maximum height of a single layer not exceeding 1.5m. They all adopt a multi-segment splicing structure, with each layer stacked vertically. The overall height is set according to the soil thickness. They are horizontally suspended between the vertical steel casing and the TBM head, with one end inserted into the mounting hole and the other end leaving a 10cm gap with the TBM head, serving as a horizontal channel from the vertical steel casing to the TBM head. The bottom of the bottom layer is supported on the rock layer. Within the rock layer, directly below the bottom layer, vertically downwards from the bottom of the bottom layer to a depth of 0.4m below the center of the shield head, a space of the same width as the horizontal steel box is excavated.

[0009] The horizontal steel box is constructed by jacking it in sections one by one. Starting from the vertical steel casing and moving towards the shield machine head, the upper box is divided into sections A1, A2...An, and the lower box is divided into sections B1, B2...Bn. The construction sequence of jacking the upper and lower layers alternates, and each section of the box is jacked in the order of A1-B1-A2-B2...An-Bn from the vertical steel casing towards the shield machine head.

[0010] The vertical steel casing, the multiple layers of horizontal steel boxes, and the space beneath the boxes together form a cutter replacement operation space for the tunnel boring machine to change cutters.

[0011] The structural features of this steel shield tunnel cutterhead replacement space structure also lie in:

[0012] The vertical steel casing is made of 3cm thick steel plate.

[0013] The vertical steel casing is assembled by vertically splicing multiple sections of the casing, with adjacent sections welded together. Each section is 3-5m long.

[0014] Each section of the horizontal steel box is spliced ​​sequentially from the vertical steel casing towards the shield machine head along the horizontal direction, and the length of each section is evenly divided according to the total length of the water tank steel box.

[0015] In each layer of horizontal steel boxes, the length of each box section is 40-50cm.

[0016] The width of the horizontal steel box is 1.2m.

[0017] This invention also proposes a construction method for a steel shield tunnel cutterhead replacement space structure, comprising the following steps:

[0018] Step 1: Install deep dewatering wells and lower the groundwater level.

[0019] After determining the center position of the vertical steel casing on the tunnel's forward axis, three dewatering wells are arranged within a 5m radius of the center of the vertical steel casing. The well locations should avoid the already excavated tunnel, and the bottom elevation of the wells should be below the bottom of the shield tunnel. The outer diameter of the dewatering well is Φ50cm, and the inner diameter is Φ40cm. Concrete filter pipes are installed in the dewatering layer, and water pumps are installed inside the wells to pump out groundwater and lower the groundwater level around the vertical steel casing.

[0020] Step 2: Drilling the hole with a rotary drilling rig and installing the vertical steel casing.

[0021] A vertical steel casing is installed 1.2m away from the shield head on the axis in front of the tunnel boring machine. First, the center of the vertical steel casing is determined by measurement and positioning. A full-rotation casing machine is used to drive the vertical steel casing into the machine in sections using a multi-section splicing method. Simultaneously, a rotary drilling rig is used to excavate the soil inside the vertical steel casing in sections. After the 2m diameter section reaches an elevation 1.0m below the tunnel center, a 1.8m diameter section is driven into the machine in sections to 1.0m below the tunnel center. Then, the large diameter section is lifted to 1.0m above the tunnel top. The overlap length between the large and small diameter sections is no less than 0.5m, and they are welded together. Each section of the large diameter section is 3-5m long and is welded together.

[0022] Step 3: Construct a horizontal steel box

[0023] Each layer of horizontal steel box is made in sections. Each box section is made directly using 40-50cm wide channel steel. Each box section is made by welding 4 channel steel sections end to end. 4 holes are arranged on each side flange of the channel steel for temporary connection and fixation with 8.8 grade M27 bolts when the two box sections are joined.

[0024] A steel plate of the same width as the steel box, thin at the front end, 3cm thick at the rear end, and no more than 10cm long is welded to the top of the first section of the steel box located on the side of the shield machine head. This plate serves as the front cutting tool and retaining top plate when the steel box is pushed forward.

[0025] Step 4: Steel box jacking and back construction

[0026] Each layer of horizontal steel box is constructed using a horizontal jacking method. A jacking backing is installed at the middle of the rear of each layer of horizontal steel box: First, the back of the jack and the jacking track of the steel box are measured and positioned to determine the position of the backing; a 2cm thick backing flat steel plate is welded onto the vertical steel casing, with a maximum distance of 30cm from the vertical steel casing and a height of 0.5m. C20 concrete is poured between the flat steel plate and the vertical steel casing to form the jacking backing;

[0027] Step 5: Pipe Roof Construction

[0028] The soil above the horizontal steel box is reinforced by pipe roof support inside the vertical steel casing. A pipe roof is formed between the vertical steel casing and the tunnel boring machine and above the horizontal steel box to ensure the construction safety of each layer of horizontal steel box: within a range of 40cm above the top of the top horizontal steel box, with a spacing of no more than 5cm and a width of no less than 2m, steel pipes with a length of no less than 1.5m and a diameter of ￠50 are driven into the soil. After the steel pipes are driven in, the ends of the steel pipes are welded to the vertical steel casing.

[0029] Step Six: Layered and Segmented Alternating Jacking Construction of the Steel Box

[0030] 6.1 Divide the upper horizontal steel box into three sections: A1, A2, and A3; and divide the lower horizontal steel box into three sections: B1, B2, and B3.

[0031] 6.2 Jack arrangement: Two 20T jacks are used to lift the upper horizontal steel box, and two 50T jacks are used to lift the lower horizontal steel box;

[0032] 6.3 Jacking sequence: The construction sequence of alternating jacking in two layers is adopted, that is, jacking in the order of A1-B1-A2-B2-A3-B3.

[0033] 6.4 Steel box jacking operation:

[0034] 1) Cut out appropriate mounting holes on the vertical steel casing according to the cross-sectional size of the two layers of horizontal steel boxes;

[0035] 2) The lower part of the horizontal steel box is a rock layer. Before jacking, the rock surface should be cleaned and leveled to form a horizontal working surface for the horizontal jacking of the steel box. Two No. 43 steel rails are installed on the horizontal working surface to serve as the direction and route for the jacking of the lower horizontal steel box. Channel steel is welded to the top of each section of the lower horizontal steel box for auxiliary control of the direction when the upper horizontal steel box is jacked.

[0036] 3) Install sections A1 and B1 of the box body. The front end extends out from the mounting hole on the vertical steel casing, and the rear end is installed between the rear end and the jacking backing. The front end of the jack is supported on the side frames of sections A1 and B1 respectively, and the rear end is supported on the jacking backing. Use a pneumatic pick to excavate the soil inside sections A1 and B1. When the pneumatic pick excavates a small section, the jack will jack in a corresponding small section. First, jack in section A1, with section A1 ahead, and then jack in section B1. During the jacking process, keep section B1 close to section A1.

[0037] 4) After the A1 and B1 sections of the box girder have completely entered the soil layer, the A2 and B2 sections of the box girder should be installed in a timely manner. The A2 and B2 sections of the box girder should be connected to the A1 and B1 sections of the box girder respectively with bolts. In this way, the jacking construction of all horizontal steel boxes is completed.

[0038] 5) After the upper and lower layers are horizontally pushed into the steel box, they are welded together with the vertical steel casing to form a whole;

[0039] Step 7: Construction of the space beneath the inner box of the rock strata

[0040] The rock strata below the steel box were excavated using impact and other mechanical methods to form a space under the box with the same width as the horizontal steel box. Steel supports were installed on both sides of the rock space to support the steel box above.

[0041] Step 8: Tunnel Boring Machine Cutter Replacement Operation

[0042] After the cutter replacement operation space is formed, open the shield machine cabin door and replace the cutter heads on the shield machine cutterhead that are facing the cutter replacement operation space one by one. After replacement, rotate the shield machine cutterhead and rotate the unreplaced cutter heads to face the cutter replacement operation space in sequence and replace the cutter heads until the cutter replacement operation of the entire shield machine cutterhead is completed.

[0043] Step 9: Dismantle the tool changing space structure

[0044] After the cutter replacement is completed, dismantle the equipment in the reverse order of installation, proceeding as follows: remove the lower rock steel support - remove the lower horizontal steel box - remove the upper horizontal steel box - pull out the roof steel pipe - pull out the vertical steel casing.

[0045] 9.1 Remove the steel supports of the lower rock layer and backfill the space under the box in the rock layer and the space under the vertical steel casing with cement and soil;

[0046] 9.2. Dismantle the lower horizontal steel box section by section; weld two triangular supports onto the vertical steel casing outside the steel box as fulcrums for hydraulic jacks; use 200 I-beams as crossbeams, connect them to the B3 section of the box to be pulled out, use 50T jacks to support the triangular supports, hold the crossbeams, gradually apply pressure, and push out the lower horizontal steel box. Remove the connecting bolts between the B3 and B2 sections of the box, and lift the B3 section from the vertical steel casing to the ground; then connect the B2 section to the 200 I-beams, and push it out with jacks, lifting the B2 section from the vertical steel casing to the ground. Similarly, lift the B1 section out and lift it to the ground, completing the dismantling of the entire lower horizontal steel box. After dismantling, promptly fill the space left by the dismantling of the lower horizontal steel box with lightweight precast concrete blocks and cement soil.

[0047] 9.3. Referring to step 8.2, remove the upper horizontal steel box in the same way. After removal, fill the space left by the removal of the upper horizontal steel box with lightweight precast concrete blocks and cement soil in a timely manner.

[0048] 9.4. Promptly remove the ceiling steel pipes; cut the steel pipes directly and remove them one by one;

[0049] 9.5. Backfill the vertical steel casing section above the upper horizontal steel box with soil. The soil moisture content should be 19%-23% and the compaction coefficient should be not less than 0.93. Before backfilling, install 2-3 grouting pipes that extend into the ground.

[0050] 9.6. Use a full-rotation casing machine to remove the vertical steel casing, and tidy up the removed part. After the shield body passes through the vertical steel casing section, promptly grout the vertical steel casing section to reinforce it and prevent ground subsidence.

[0051] Compared with existing technologies, the beneficial effects of this invention are reflected in:

[0052] This invention utilizes a combination of a vertical steel casing, a horizontal steel box, and the space beneath the excavation box within the rock strata to form a shield cutterhead replacement operating space. Even at the rock-soil interface, where the upper soil layer is extremely unstable and prone to collapse under the influence of groundwater, this invention creates a safe operating space for cutterhead replacement in front of the tunnel boring machine (TBM), effectively solving the problem of cutterhead replacement in tunnel boring machines. Furthermore, it is easy to install and dismantle, has low construction costs, and offers significant economic benefits. Specifically:

[0053] 1. Vertical steel casings are high-strength steel structures, and being cylindrical, they possess excellent mechanical properties, high rigidity, and good stability. This invention fully utilizes the advantageous structure of vertical steel casings to create vertical underground space. Furthermore, the simple structure and easy construction of vertical steel casings, combined with equipment such as rotary drilling rigs, allow for the rapid formation of stable underground working spaces.

[0054] 2. The horizontal steel box is also a steel structure with high strength. It can be processed into multiple layers and sections. It can be conveniently used in the limited space of the vertical steel casing to form a horizontal underground space section by section.

[0055] 3. The vertical steel casing, together with the horizontal steel box and the space under the inner box of the rock stratum, form an underground working space with ample space for tool changing operations. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the elevation structure of the present invention;

[0057] Figure 2 This is a side view of the structure of the present invention;

[0058] Figure 3 This is a schematic diagram of the planar structure of the present invention;

[0059] Figure 4 This is a front view structural diagram of the horizontal steel box;

[0060] Figure 5 This is a side view of the horizontal steel box structure.

[0061] Figure 6 This is a schematic diagram of the cross-sectional structure of the horizontal steel box;

[0062] Figure 7 This is a structural diagram of the horizontal steel box being dismantled.

[0063] In the diagram, 1 is the axis; 2 is the vertical steel casing; 3 is the horizontal steel box; 4 is the tunnel boring machine; 5 is the space under the box; 6 is the dewatering well; 7 is the pipe roof; 8 is the jacking backing; 9 is the jack; and 10 is the bolt hole. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0065] Please refer to Figures 1 to 7 The cutterhead replacement space structure of the steel structure shield tunneling machine in this embodiment is set as follows:

[0066] A vertical steel casing 2 is arranged on the axis 1 in front of the tunnel shield machine 4, 1.2m away from the shield head. The vertical steel casing 2 is a multi-section splicing structure with a larger diameter at the top and a smaller diameter at the bottom. The section above the 1.0m height of the tunnel top is a large diameter section with a diameter of 2.0m, and the section below is a small diameter section with a diameter of 1.8m.

[0067] Mounting holes are made on the wall of the vertical steel casing 2 facing the tunnel boring machine 4, directly opposite the tunnel boring machine 4, for installing the horizontal steel box 3. Considering the strength, rigidity, and stability of the steel box structure, the horizontal steel box 3 has a maximum of two layers, with the maximum height of a single layer not exceeding 1.5m. All layers adopt a multi-segment splicing structure, with each layer stacked vertically. The overall height is set according to the soil thickness. It extends horizontally between the vertical steel casing 2 and the tunnel boring machine 4 head, with one end inserted into the mounting hole and the other end maintaining a 10cm gap from the tunnel boring machine 4 head, serving as the passageway between the vertical steel casing 2 and the tunnel boring machine 4 head. The horizontal channel of the shield head is supported on the bottom of the bottom box. Within the rock layer, directly below the bottom box, vertically downwards from the bottom of the bottom box to a depth of 0.4m below the center of the shield head, a space 5 under the box, adapted to the width of the horizontal steel box 3, is excavated using a combination of manual and mechanical methods. The length of the space under the box from the vertical steel casing towards the shield machine should be greater than the length of the horizontal steel box. In this embodiment, the space under the box extends to the location of the shield machine in the length direction, forming a through channel between the vertical steel casing and the shield machine in the length direction.

[0068] The horizontal steel box 3 is constructed by jacking it up in sections. Starting from the vertical steel casing 2 and moving towards the shield machine 4 head, the upper box body is divided into sections A1, A2...An, and the lower box body is divided into sections B1, B2...Bn. The construction sequence of alternating jacking of the upper and lower layers is adopted. The box body sections are jacked up from the vertical steel casing 2 towards the shield machine 4 head in the order of A1-B1-A2-B2...An-Bn.

[0069] The vertical steel casing 2, the multi-layer horizontal steel box 3, and the space below the box 5 together form the cutter replacement operation space for the tunnel boring machine 4 to change cutters.

[0070] The structural features of this steel shield tunnel cutterhead replacement space structure also lie in:

[0071] The vertical steel casing 2 is made of 3cm thick steel plate.

[0072] The vertical steel casing 2 is assembled by vertically splicing multiple sections of the casing. Adjacent sections are welded together, and each section is 3-5m long.

[0073] Each section of the horizontal steel box 3 is spliced ​​sequentially from the vertical steel casing 2 towards the shield machine head 4 along the horizontal direction, and the length of each section is evenly divided according to the total length of the water tank steel box.

[0074] In each layer of horizontal steel box 3, the length of each box section is 40-50cm.

[0075] The width of the horizontal steel box 3 is 1.2m.

[0076] Since the bottom horizontal steel box 3 is located below the rock layer, there is no need for a steel box. It is sufficient to install steel supports on the rock layer on both sides of the bottom horizontal steel box 3, with the upper end connected to the bottom horizontal steel box 3 and the lower end supported on the rock.

[0077] In practice, the tool change operation space should meet the following requirements:

[0078] 1. The cutterhead changing operating space should be large enough to allow the largest cutterhead box, located at the center of the tunnel boring machine (TBM), to be smoothly hoisted from the ground into the operating space and reach the shield head, with sufficient space to facilitate operation by skilled workers. At the same time, the operating space should not be excessively large; it should only meet the requirements to control construction costs.

[0079] 2. The cutter replacement operation space should be located directly in front of the tunnel boring machine (TBM) 4, and the center line of the vertical steel casing should be located on the center line of the shield tunnel.

[0080] 3. The cutterhead changing operation space must have both vertical space to meet the vertical space requirements from the ground to the tunnel boring machine (TBM) 4, and horizontal space to meet the horizontal space requirements to reach the shield head. The bottom elevation of the vertical steel casing should be 1.0m lower than the shield head rotation center to allow space for cutterhead changing operations and the installation space for the bottom drainage pump. The top of the horizontal steel box 3 should be at least 0.4m higher than the top of the TBM, and the bottom operating space should be at least 0.4m lower than the shield head rotation center. The width of the horizontal operating space should not be less than 1.2m to ensure sufficient operating space.

[0081] This invention also proposes a shield cutterhead replacement method based on the above-mentioned steel structure shield cutterhead replacement space structure:

[0082] After the cutterhead replacement operation space is formed, open the door of the fourth chamber of the tunnel boring machine (TBM) and carry out the cutterhead replacement operation from both sides of the fourth cutterhead. Replace the cutterheads on the fourth cutterhead of the TBM one by one that are facing the cutterhead replacement operation space. After replacement, rotate the fourth cutterhead of the TBM and rotate the unreplaced cutterheads to face the cutterhead replacement operation space in sequence and replace the cutterheads until the cutterhead replacement operation of the entire fourth cutterhead of the TBM is completed, and all the damaged cutterheads are replaced with cutterheads that can excavate rock.

[0083] This invention also proposes a construction method for a steel shield tunnel cutterhead replacement space structure, comprising the following steps:

[0084] Step 1: Install 6 deep dewatering wells and lower the groundwater level.

[0085] After determining the center position of the vertical steel casing 2 on the tunnel's forward axis 1, three dewatering deep wells 6 are arranged within a radius of 5m around the center of the vertical steel casing 2. The well locations should avoid the already excavated tunnel, and the bottom elevation of the wells should be below the bottom of the shield tunnel. The outer diameter of the dewatering deep well 6 is Φ50cm, and the inner diameter is Φ40cm. Concrete filter pipes are installed in the dewatering layer, and water pumps are installed inside the wells to pump out groundwater to lower the groundwater level around the vertical steel casing 2.

[0086] Step 2: Drilling the hole with a rotary drilling rig and installing the vertical steel casing.

[0087] A vertical steel casing 2 is installed 1.2m away from the shield head on the axis 1 in front of the tunnel boring machine 4. First, the center of the vertical steel casing 2 is determined by measurement and positioning. The vertical steel casing is driven in sections using a multi-section splicing method with a full-rotation casing machine. At the same time, the soil inside the vertical steel casing is excavated in sections using a rotary drilling rig. After the large-diameter section with a diameter of 2m reaches an elevation of 1.0m below the tunnel center, a small-diameter section with a diameter of 1.8m is driven in to 1.0m below the tunnel center using a multi-section splicing method. Then, the large-diameter section is lifted to 1.0m above the tunnel top. The overlap length between the large-diameter section and the small-diameter section is not less than 0.5m, and they are welded together. Each section of the large-diameter section is 3-5m long and is welded together.

[0088] Step 3: Construct horizontal steel box 3

[0089] Each layer of horizontal steel box is made in 3 sections. Each section of the box is made directly using 40-50cm wide channel steel. Each section of the box is made by welding 4 sections of channel steel end to end. 4 holes are arranged on each side flange of the channel steel as bolt holes 10, which are used for temporary connection and fixation with 8.8 grade M27 bolts when the two sections of the box are joined.

[0090] A steel plate of the same width as the steel box, thin at the front end, 3cm thick at the rear end, and no more than 10cm long is welded to the top of the first section of the steel box 3 located on the side of the shield machine head 4. This plate serves as the front cutting tool and retaining top plate when the steel box is pushed forward.

[0091] Step 4: Steel box jacking into the back 8 construction

[0092] Each layer of horizontal steel box 3 is constructed using a horizontal jacking method. A jacking backrest 8 is set at the middle of the rear of each layer of horizontal steel box 3. First, the backrest of the jack 9 and the jacking track of the steel box are measured and positioned to determine the position of the backrest. A 2cm thick backrest flat steel plate is welded on the vertical steel casing 2, with a maximum distance of 30cm from the vertical steel casing 2 and a height of 0.5m. C20 concrete is poured between the flat steel plate and the vertical steel casing 2 to form the jacking backrest 8.

[0093] Step 5, Pipe Roof 7 Construction

[0094] The soil above the horizontal steel box 3 is reinforced by pipe roof 7 inside the vertical steel casing 2. Pipe roof 7 is formed between the vertical steel casing 2 and the shield machine 4 and above the horizontal steel box 3 to ensure the construction safety of each layer of horizontal steel box 3 and effectively prevent soil collapse. Within 40cm above the top of the top horizontal steel box 3, with a spacing of no more than 5cm and a width of no less than 2m, steel pipes with a length of no less than 1.5m and a diameter of ￠50 are driven into the soil. After the steel pipes are driven in, the ends of the steel pipes are welded to the vertical steel casing 2.

[0095] Step Six: Layered and Segmented Alternating Jacking Construction of the Steel Box

[0096] The installation of the horizontal steel box 3 is constrained by the size of the vertical steel casing 2. The segmented jacking method is adopted for construction. During jacking, a 10cm distance is reserved between the front end of the steel box and the cutterhead of the tunnel boring machine 4 to provide space for the rotation of the cutterhead of the tunnel boring machine 4 when changing the cutter.

[0097] 6.1 Divide the upper horizontal steel box 3 into three sections: A1, A2, and A3; and divide the lower horizontal steel box 3 into three sections: B1, B2, and B3.

[0098] 6.2 Arrangement of jacks 9: Two 20T jacks 9 are used to lift the upper layer horizontally towards the steel box 3, and two 50T jacks 9 are used to lift the lower layer horizontally towards the steel box 3;

[0099] 6.3 Jacking sequence: The construction sequence of alternating jacking in two layers is adopted, that is, jacking in the order of A1-B1-A2-B2-A3-B3.

[0100] 6.4 Steel box jacking operation:

[0101] 1) Cut out appropriate mounting holes on the vertical steel casing 2 according to the cross-sectional size of the two horizontal steel boxes 3;

[0102] 2) The lower part of the horizontal steel box 3 is a rock layer. Before jacking, the rock surface should be cleaned and leveled to form a horizontal working surface for the horizontal jacking of the steel box. Two No. 43 steel rails are installed on the horizontal working surface to serve as the direction and route for the jacking of the lower horizontal steel box 3. Channel steel is welded to the top of each section of the lower horizontal steel box 3 for auxiliary control of the direction when the upper horizontal steel box 3 is jacked.

[0103] 3) Install sections A1 and B1 of the box body. The front end extends out from the mounting hole on the vertical steel casing 2, and the rear end is installed between the rear end and the jacking backing 8. The front end of the jack 9 is supported on the side frames of sections A1 and B1 respectively, and the rear end is supported on the jacking backing 8. Use a pneumatic pick to excavate the soil inside sections A1 and B1. When the pneumatic pick excavates a small section, the jack 9 will jack in a corresponding small section. First, jack in section A1, with section A1 ahead, and then jack in section B1. During the jacking process, keep section B1 close to section A1.

[0104] 4) After the A1 and B1 sections of the box body have entered the soil layer, the A2 and B2 sections of the box body shall be installed in a timely manner. The A2 and B2 sections of the box body shall be connected to the A1 and B1 sections of the box body respectively with bolts. In this way, the jacking construction of all horizontal steel box 3 shall be completed.

[0105] 5) After the upper and lower layers are pushed horizontally into the steel box 3, they are welded together with the vertical steel casing 2 to form a whole;

[0106] Step 7: Construction of the space below the inner box of the rock strata 5

[0107] The rock strata below the steel box are excavated using impact and other mechanical methods to form a space 5 under the box with the same width as the horizontal steel box 3. Steel supports are installed on both sides of the rock space to support the upper steel box and ensure the stability and safety of the upper steel box.

[0108] Step 8: Tunnel Boring Machine Cutter Replacement Operation

[0109] After the cutter replacement operation space is formed, open the shield machine cabin door and replace the cutter heads on the shield machine cutterhead that are facing the cutter replacement operation space one by one. After replacement, rotate the shield machine cutterhead and rotate the unreplaced cutter heads to face the cutter replacement operation space in sequence and replace the cutter heads until the cutter replacement operation of the entire shield machine cutterhead is completed.

[0110] Step 9: Dismantle the tool changing space structure

[0111] After the cutter replacement is completed, dismantle the equipment in the reverse order of installation, proceeding as follows: remove the lower rock steel support - remove the lower horizontal steel box 3 - remove the upper horizontal steel box 3 - pull out the roof steel pipe - pull out the vertical steel casing 2.

[0112] 9.1 Remove the steel support of the lower rock layer and backfill the space under the box 5 in the rock layer and the space under the vertical steel casing 2 with cement and soil;

[0113] 9.2. Dismantle the lower horizontal steel box 3 section by section; weld two triangular supports onto the vertical steel casing 2 outside the steel box to serve as fulcrums for the hydraulic jacks 9; use 200 I-beams as crossbeams, connecting them to the B3 section of the box to be pulled out, and use 50T jacks 9 to support the triangular supports, holding the crossbeams in place, gradually applying pressure to push out the lower horizontal steel box 3, remove the connecting bolts between the B3 section and the B2 section, and pull the B3 section from the vertical steel casing 2. The B2 section box is then hoisted to the ground; the B2 section box is then connected to the 200 I-beam, and jacked out using jack 9. The B2 section steel box is then hoisted to the ground from inside the vertical steel casing 2. Similarly, the B1 section box is hoisted to the ground after being jacked out, completing the dismantling of the entire lower horizontal steel box 3. After dismantling, the space left by the dismantling of the lower horizontal steel box is promptly filled with lightweight precast concrete blocks and cement soil. Low-strength lightweight precast concrete blocks should be selected, and in this embodiment, they should not exceed C15.

[0114] 9.3. Referring to step 8.2, remove the upper horizontal steel box 3 in the same way. After removal, fill the space left by the removal of the upper horizontal steel box with lightweight precast concrete blocks and cement soil in a timely manner.

[0115] 9.4. Promptly remove the ceiling steel pipes; cut the steel pipes directly and remove them one by one;

[0116] 9.5. Backfill the vertical steel casing section 2 above the upper horizontal steel box 3 with loam soil. The moisture content of the loam soil should be 19%-23% and the compaction coefficient should be not less than 0.93. Before backfilling, 2-3 grouting pipes extending into the ground should be buried in advance.

[0117] 9.6. Use a full-rotation casing machine to remove the vertical steel casing 2, and tidy up the removed part. After the shield body passes through the vertical steel casing 2 section, promptly grout the vertical steel casing 2 section to reinforce it and prevent ground subsidence.

[0118] Working principle:

[0119] This embodiment combines the vertical steel casing 2 with the horizontal steel box 3 and the space 5 under the inner box of the rock stratum to form a semi-open space in both the vertical and horizontal directions. At the same time, it can realize the rapid installation of the vertical steel casing 2 and the segmented and layered alternating jacking installation of the horizontal steel box 3 under complex conditions. Its high-strength structure ensures the stability and safety of the assembly and effectively solves the problems of material transportation and personnel access in both the vertical and horizontal directions. The cutter replacement space structure is arranged in front of the shield machine 4, creating a working space for cutter replacement.

[0120] Application examples:

[0121] The Hefei Metro Line 4 South Extension Civil Engineering General Contracting Project starts at Jinqiao Road Station and connects to the under-construction Fenglehe Station of Line 4, with a total length of 13.62km. The section between Mingzhu Avenue Station and Fuxing Road Station is a component of this project. After the right tunnel boring machine (TBM) started, construction proceeded normally. On April 21, 2022, when the right tunnel reached the 628th ring, the equipment malfunctioned and the machine was shut down for repair. On the night of April 23, the tunnel was restarted, but the screw conveyor experienced water inrush throughout the ring, and a small amount of schist boulders of varying shapes (30×20cm) were excavated. At the 1500mm mark, the amount of slag discharged was one bucket more than normal (containing more water). Construction was immediately stopped on site, and the ground collapsed.

[0122] On-site investigations and verifications were conducted on the left and right lines of the Mingzhu Avenue Station-Fuxing Road Station section. The current tunneling stratum is olivine basalt, and the current cutting tools of TBM 4 (suitable for soil tunneling) are not suitable for tunneling in olivine basalt strata. After multiple discussions among all participating parties and experts, it was deemed necessary to open the cutterhead and replace the cutting tools of TBM 4 in the Mingzhu Avenue Station-Fuxing Road Station section.

[0123] For the right tunnel, which had reached the rock section, the tunnel cross-section was not a single rock layer; the upper part was soil, and the lower part was rock. Groundwater was abundant in the soil and rock, resulting in extremely poor stability at the tunnel face. To address this, the right tunnel adopted a shield cutterhead replacement space structure combining a vertical steel casing 2, a horizontal steel box 3, and an excavated space 5 under the box within the rock layer. This effectively solved the shield cutterhead replacement problem. The method is technically feasible, safe, reliable, and has low construction costs, and the entire cutterhead replacement process was successful.

[0124] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A steel-structured shield tunnel cutterhead changing space structure, characterized in that: A vertical steel casing is arranged on the axis in front of the tunnel shield machine at a distance of 1.2m from the shield head. The vertical steel casing is a multi-section splicing structure with a larger diameter at the top and a smaller diameter at the bottom. The section above the 1.0m height of the tunnel top is a large diameter section with a diameter of 2.0m, and the section below is a small diameter section with a diameter of 1.8m. Mounting holes are made on the wall of the vertical steel casing facing the tunnel boring machine (TBM) at the position directly opposite the TBM, for mounting horizontal steel boxes. The horizontal steel boxes have up to two layers, with the maximum height of a single layer not exceeding 1.5m. They all adopt a multi-segment splicing structure, with each layer stacked vertically. The overall height is set according to the soil thickness. They are horizontally suspended between the vertical steel casing and the TBM head, with one end inserted into the mounting hole and the other end leaving a 10cm gap with the TBM head, serving as a horizontal channel from the vertical steel casing to the TBM head. The bottom of the bottom layer is supported on the rock layer. Within the rock layer, directly below the bottom layer, vertically downwards from the bottom of the bottom layer to a depth of 0.4m below the center of the shield head, a space of the same width as the horizontal steel box is excavated. The horizontal steel box is constructed by jacking it in sections one by one. Starting from the vertical steel casing and moving towards the shield machine head, the upper box is divided into sections A1, A2...An, and the lower box is divided into sections B1, B2...Bn. The construction sequence of jacking the upper and lower layers alternates, and each section of the box is jacked in the order of A1-B1-A2-B2...An-Bn from the vertical steel casing towards the shield machine head. The vertical steel casing, the multiple layers of horizontal steel boxes, and the space beneath the boxes together form a cutter replacement operation space for the tunnel boring machine to change cutters.

2. The steel structure shield tunnel cutterhead replacement space structure according to claim 1, characterized in that: The vertical steel casing is made of 3cm thick steel plate.

3. The steel structure shield tunnel cutterhead replacement space structure according to claim 1, characterized in that: The vertical steel casing is assembled by vertically splicing multiple sections of the casing, with adjacent sections welded together. Each section is 3-5m long.

4. The steel structure shield tunnel cutterhead replacement space structure according to claim 1, characterized in that: Each section of the horizontal steel box is spliced ​​sequentially from the vertical steel casing towards the shield machine head along the horizontal direction, and the length of each section is evenly divided according to the total length of the water tank steel box.

5. The steel shield tunnel cutterhead replacement space structure according to claim 1 or 4, characterized in that: In each layer of horizontal steel boxes, the length of each box section is 40-50cm.

6. The steel structure shield tunnel cutterhead replacement space structure according to claim 1, characterized in that: The width of the horizontal steel box is 1.2m.

7. A construction method for a steel-structured shield tunnel cutterhead replacement space structure, characterized in that, The method for implementing the steel structure shield cutterhead replacement space structure according to any one of claims 1-6 includes the following steps: Step 1: Install deep dewatering wells and lower the groundwater level. After determining the center position of the vertical steel casing on the tunnel's forward axis, three dewatering wells are arranged within a 5m radius of the center of the vertical steel casing. The well locations should avoid the already excavated tunnel, and the bottom elevation of the wells should be below the bottom of the shield tunnel. The outer diameter of the dewatering well is Φ50cm, and the inner diameter is Φ40cm. Concrete filter pipes are installed in the dewatering layer, and water pumps are installed inside the wells to pump out groundwater and lower the groundwater level around the vertical steel casing. Step 2: Drilling the hole with a rotary drilling rig and installing the vertical steel casing. A vertical steel casing is installed 1.2m away from the shield head on the axis in front of the tunnel boring machine. First, the center of the vertical steel casing is determined by measurement and positioning. A full-rotation casing machine is used to drive the vertical steel casing into the machine in sections using a multi-section splicing method. Simultaneously, a rotary drilling rig is used to excavate the soil inside the vertical steel casing in sections. After the 2m diameter section reaches an elevation 1.0m below the tunnel center, a 1.8m diameter section is driven into the machine in sections to 1.0m below the tunnel center. Then, the large diameter section is lifted to 1.0m above the tunnel top. The overlap length between the large and small diameter sections is no less than 0.5m, and they are welded together. Each section of the large diameter section is 3-5m long and is welded together. Step 3: Construct a horizontal steel box Each layer of horizontal steel box is made in sections. Each box section is made directly using 40-50cm wide channel steel. Each box section is made by welding 4 channel steel sections end to end. 4 holes are arranged on each side flange of the channel steel for temporary connection and fixation with 8.8 grade M27 bolts when the two box sections are joined. A steel plate of the same width as the steel box, thin at the front end and thick at the rear end, and no more than 10cm in length, is welded to the top of the first section of the steel box located on the side of the tunnel boring machine head. This plate serves as the front cutting tool and retaining top plate when the steel box is pushed forward. The rear end of the steel plate is 3cm thick. Step 4: Steel box jacking and back construction Each layer of horizontal steel box is constructed using a horizontal jacking method. A jacking backing is installed at the middle of the rear of each layer of horizontal steel box: First, the back of the jack and the jacking track of the steel box are measured and positioned to determine the position of the backing; a 2cm thick backing flat steel plate is welded onto the vertical steel casing, with a maximum distance of 30cm from the vertical steel casing and a height of 0.5m. C20 concrete is poured between the flat steel plate and the vertical steel casing to form the jacking backing; Step 5: Pipe Roof Construction The soil above the horizontal steel box is reinforced by pipe roof support inside the vertical steel casing. A pipe roof is formed between the vertical steel casing and the tunnel boring machine and above the horizontal steel box to ensure the construction safety of each layer of horizontal steel box: within a range of 40cm above the top of the top horizontal steel box, with a spacing of no more than 5cm and a width of no less than 2m, steel pipes with a length of no less than 1.5m and a diameter of ¢50 are driven into the soil. After the steel pipes are driven in, the ends of the steel pipes are welded to the vertical steel casing. Step Six: Layered and Segmented Alternating Jacking Construction of Steel Boxes 6.1 Divide the upper horizontal steel box into three sections: A1, A2, and A3; and divide the lower horizontal steel box into three sections: B1, B2, and B3. 6.2 Jack arrangement: Two 20T jacks are used to lift the upper horizontal steel box, and two 50T jacks are used to lift the lower horizontal steel box; 6.3 Jacking sequence: The construction sequence of alternating jacking in two layers is adopted, that is, jacking in the order of A1-B1-A2-B2-A3-B3; 6.4 Steel box jacking operation: 1) Cut out appropriate mounting holes on the vertical steel casing according to the cross-sectional size of the two layers of horizontal steel boxes; 2) The lower part of the horizontal steel box is a rock layer. Before jacking, the rock surface should be cleaned and leveled to form a horizontal working surface for the horizontal jacking of the steel box. Two No. 43 steel rails are installed on the horizontal working surface to serve as the direction and route for the jacking of the lower horizontal steel box. Channel steel is welded to the top of each section of the lower horizontal steel box for auxiliary directional control when the upper horizontal steel box is jacked. 3) Install sections A1 and B1 of the box body. The front end extends out from the mounting hole on the vertical steel casing, and the rear end is installed between the rear end and the jacking backing. The front end of the jack is supported on the side frames of sections A1 and B1 respectively, and the rear end is supported on the jacking backing. Use a pneumatic pick to excavate the soil inside sections A1 and B1. When the pneumatic pick excavates a small section, the jack will jack in a corresponding small section. First, jack in section A1, with section A1 ahead, and then jack in section B1. During the jacking process, keep section B1 close to section A1. 4) After the A1 and B1 sections of the box girder have completely entered the soil layer, the A2 and B2 sections of the box girder should be installed in a timely manner. The A2 and B2 sections of the box girder should be connected to the A1 and B1 sections of the box girder respectively with bolts. In this way, the jacking construction of all horizontal steel boxes is completed. 5) After the upper and lower layers are pushed horizontally into the steel box, they are welded together with the vertical steel casing to form a whole; Step 7: Construction of the space beneath the inner box of the rock strata The rock strata below the steel box were excavated using impact machinery to form a space under the box with the same width as the horizontal steel box. Steel supports were installed on both sides of the rock space to support the steel box above. Step 8: Tunnel Boring Machine Cutter Replacement Operation After the cutter replacement operation space is formed, open the shield machine cabin door and replace the cutter heads on the shield machine cutterhead that are facing the cutter replacement operation space one by one. After replacement, rotate the shield machine cutterhead and rotate the unreplaced cutter heads to face the cutter replacement operation space in sequence and replace the cutter heads until the cutter replacement operation of the entire shield machine cutterhead is completed. Step 9: Dismantle the tool changing space structure After the cutter replacement is completed, dismantle the equipment in the reverse order of installation, proceeding as follows: remove the lower rock steel support - remove the lower horizontal steel box - remove the upper horizontal steel box - pull out the roof steel pipe - pull out the vertical steel casing. 9.1 Remove the steel supports of the lower rock layer and backfill the space under the box in the rock layer and the space under the vertical steel casing with cement and soil; 9.

2. Dismantle the lower horizontal steel box section by section; weld two triangular supports onto the vertical steel casing outside the steel box as fulcrums for hydraulic jacks; use 200 I-beams as crossbeams, connect them to the B3 section of the box to be pulled out, use 50T jacks to support the triangular supports, hold the crossbeams, gradually apply pressure, and push out the lower horizontal steel box. Remove the connecting bolts between the B3 and B2 sections of the box, and lift the B3 section from the vertical steel casing to the ground; then connect the B2 section to the 200 I-beams, and push it out with jacks, lifting the B2 section from the vertical steel casing to the ground. Similarly, lift the B1 section out and lift it to the ground, completing the dismantling of the entire lower horizontal steel box. After dismantling, promptly fill the space left by the dismantling of the lower horizontal steel box with lightweight precast concrete blocks and cement soil. 9.

3. Referring to step 9.2, remove the upper horizontal steel box in the same way. After removal, fill the space left by the removal of the upper horizontal steel box with lightweight precast concrete blocks and cement soil in a timely manner. 9.

4. Promptly remove the ceiling steel pipes; cut the steel pipes directly and remove them one by one; 9.

5. Backfill the vertical steel casing section above the upper horizontal steel box with soil. The soil moisture content should be 19%-23% and the compaction coefficient should be not less than 0.

93. Before backfilling, install 2-3 grouting pipes that extend into the ground. 9.

6. Use a full-rotation casing machine to remove the vertical steel casing, and tidy up the removed part. After the shield body passes through the vertical steel casing section, promptly grout the vertical steel casing section to reinforce it and prevent ground subsidence.

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