Construction structure for ventilation shafts in sections where tunnel boring machines (TBMs) pass directly.

Abstract

This utility model relates to a construction structure for a ventilation shaft in a tunnel section for direct shield tunneling. The construction structure includes: end reinforcements on the outer sides of the shaft walls on both sides opposite to each other along the shield tunneling direction; a portal on the inner end of the shaft wall of the end reinforcement structure, through which the reinforcing steel bars of the shaft wall are cut; and a backfill structure in the third basement level, comprising a cement-soil filling section and a mortar filling section. The cement-soil filling section is frustoconical with each side sloping upwards; the upper side of the sloping surface on each side of the cement-soil filling section is the mortar filling section. This utility model solves the problem that hydrogeological conditions cannot pre-reserve portals for direct shield tunneling, enabling direct shield tunneling construction and ensuring the safety and stability of the shield.

Description

Technical Field

[0001] This utility model belongs to the field of underground railway tunnel construction technology, specifically relating to a construction structure for a ventilation shaft in a section where a shield tunnel can pass directly. Background Technology

[0002] In recent years, with the rapid development of urban rail transit, shield tunneling has been widely used due to its relatively small impact on ground traffic and the surrounding environment. For long tunnel projects, to ensure the safety of the tunnel interior environment, it is necessary to design ventilation shafts, connecting passages, and other structures at certain intervals.

[0003] Typically, tunnel boring machines (TBMs) are launched from a starting point and received at the end point. The TBM starts excavating from the starting point and continues to the receiving point. However, in tunnel projects with ventilation shafts, connecting passages, and other structures, a receiving point and a second launch are required at the ventilation shaft location. An example is the construction of Phase I of Wuhan Metro Line 6.

[0004] Because the reception and launch of tunnel boring machines (TBMs) involve significant safety risks, are cumbersome to operate, and affect the construction period, existing technologies also provide a construction method that involves backfilling the ventilation shaft so that the TBM can pass directly through it.

[0005] In existing technologies, ventilation shafts that allow tunnel boring machines (TBMs) to pass through directly are constructed using underground continuous walls as enclosures, underwater concrete structures as bottom seals, and pre-drilled holes for the TBM to enter and exit. After the TBM enters and exits the tunnel and passes through the ventilation shaft, excess tunnel segments inside the shaft are removed, and finally the tunnel portal is constructed, thus completing the ventilation shaft structure.

[0006] China has a vast territory and diverse geological structures. In water-rich, soft soil areas, the reserved entrance and exit holes for tunnel boring machines (TBMs) during ventilation shaft construction pose a risk of water ingress, resulting in significant safety hazards. Therefore, the construction method of having the TBM directly pass through the ventilation shaft is difficult to implement in water-rich areas. Utility Model Content

[0007] The technical problem this invention aims to solve is that, in hydrogeological conditions, it is impossible to allow a tunnel boring machine to directly pass through a ventilation shaft for construction.

[0008] The technical solution adopted by this utility model to solve the aforementioned problem is: A construction structure for a ventilation shaft for direct shield tunneling, the main structure of which spans the left and right tunnels, includes a diaphragm wall shaft. Inside the shaft, there are a first-level negative structural slab, a second-level negative middle slab, and a second-level negative structural slab for separating spaces. Below the second-level negative structural slab is the third-level negative space of the stratum where the tunnel is located. Outside the shaft, on the outer sides of the two opposite sides of the shaft wall along the shield tunneling direction, there are end reinforcement structures. The cross section of the end reinforcement structures is larger than the shield cutting surface. The well wall at the inner end of the end reinforcement structure is provided with a portal, which includes a protective layer cutting groove and a wall concrete cutting groove. The protective layer cutting groove is a slot formed by removing the steel reinforcement protective layer on the inner surface of the well wall. The inner layer steel reinforcement of the well wall is set as a cut-off zone corresponding to the range of the protective layer cutting groove. The wall concrete cutting groove is a slot from the protective layer cutting groove to the outer layer steel reinforcement of the well wall. The outer layer steel reinforcement of the well wall is set as a cut-off zone corresponding to the range of the wall concrete cutting groove. A concrete cushion layer is set on the bottom slab of the third basement level, with the elevation of the concrete cushion layer reaching the lower side of the portal. A backfill structure is set in the third basement level, which includes a cement-soil filling part and a mortar filling part. The cement-soil filling part is frustoconical, with its bottom surface located in the middle of the concrete cushion layer and each side surface sloping upwards. The mortar filling part is located above the sloping surface on each side of the cement-soil filling part. Construction openings are provided through the structural slabs of the first basement level, the middle slab of the second basement level, and the structural slab of the second basement level, and cover plates are installed on the construction openings.

[0009] Compared with the prior art, the advantages of this utility model with the above structure are: 1) The structure provided by this utility model enables the shield tunneling machine to directly pass through the ventilation shaft in a hydrogeological environment, avoiding the need for receiving and starting construction at the ventilation shaft location, thus saving construction time and ensuring construction safety; 2) The backfilling structure in this utility model makes the tunneling of the shield machine gradually transition between different soft and hard structures when the shield machine passes through the ventilation shaft, protecting the safety and stability of the shield machine and avoiding the shield machine head-down situation.

[0010] As a preferred option, a further technical solution to the above structure is: After the tunnel boring machine passes through the ventilation shaft, an end-face sealing structure is installed at the tunnel entrance on the inner wall of the shaft.

[0011] The inner wall of the construction opening is a sloping socket, and the cover plate is a precast reinforced concrete structural slab. The cover plate is installed inside the construction opening, and the periphery of the cover plate matches the sloping surface of the socket. Anchor bolt rods are also provided, which are perpendicular to the sloping surface of the socket and penetrate through the cover plate and the second basement structural slab into the third basement space. A grouting port is reserved on the surface of the cover plate.

[0012] The end-face closure structure is a ring beam that covers the well wall opening and the circumference of the shield tunnel segment ends. The ring beam is a concrete structure with an internal ring-shaped steel lattice. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the construction structure of the inter-section ventilation shaft of this utility model; Figure 2 This is a structural diagram (front elevation) of the initial stage (cement-soil) of the internal backfilling of the ventilation shaft of this utility model. Figure 3 This is a schematic diagram of the portal opening structure of this utility model; Figure 4 This is a structural diagram (front elevation) of the completed backfill state of the ventilation shaft inside the section of this utility model. Figure 5 for Figure 4 Sectional view of the middle AA line; Figure 6 This is a schematic diagram of the structure of an embodiment of the cover plate installation of this utility model; Figure 7 This is a schematic diagram showing the shield tunnel passing through the ventilation shaft of this utility model. Figure 8 This is a structural diagram of the ventilation shaft after the backfill structure inside the shaft has been removed and the tunnel lining segments have been dismantled.

[0014] In the diagram: 1. Basement Level 1 Structural Slab; 2. Basement Level 2 Middle Slab; 3. Basement Level 2 Structural Slab; 31. Construction Portal; 4. Basement Level 3 Space; 5. Well Wall; 6. End Reinforcement Structure; 7. Concrete Pad; 8. Cement-Soil Filling Section; 9. Portal; 10. Inner Reinforcing Steel; 11. Outer Reinforcing Steel; 12. Mortar Filling Section; 13. Cover Plate; 14. Shield Tunnel Segment; 15. Ring Beam. Detailed Implementation

[0015] The present invention will be further described below with reference to embodiments, the purpose of which is only to better understand the content of the present invention. Therefore, the examples given do not limit the scope of protection of the present invention.

[0016] The planned subway line from Dongli District Tumor Hospital to Lijiang Road Station in Tianjin is located in an area with silty clay soil. The ventilation shaft is located in the northeast quadrant of the PetroChina overpass at the intersection of Weijin South Road and Heiniucheng Road. The ventilation shaft has a large mileage end with hydrogeological conditions. In order to ensure waterproofing inside the shaft, the ventilation shaft must be constructed as a whole. The shield tunnel opening cannot be reserved in advance, otherwise a large amount of water will accumulate inside the shaft.

[0017] This utility model provides a design scheme that allows the tunnel boring machine (TBM) to pass directly through the ventilation shaft in this section. See also... Figures 1 to 6 As shown, this utility model provides a construction structure for a ventilation shaft for direct shield tunneling. The main structure of the ventilation shaft spans the left and right tunnels and includes a diaphragm wall shaft. Inside the shaft, there are a first-level negative structural plate 1, a second-level negative middle plate 2, and a second-level negative structural plate 3 for separating spaces. Below the second-level negative structural plate 3 is the third-level negative space 4 of the stratum where the tunnel is located. Outside the shaft, the outer sides of the two opposite sides of the third-level negative space 4 are provided with end reinforcement structures 6. The cross section of the end reinforcement structure 6 is larger than the shield cutting surface. The well wall 5 at the inner end of the end reinforcement structure 6 is provided with a portal 9. The portal 9 includes a protective layer cutting groove and a wall concrete cutting groove. The protective layer cutting groove is a slot formed by removing the steel reinforcement protective layer on the inner surface of the well wall 5. The inner layer steel reinforcement 10 of the well wall 5 is set as a cut-off zone corresponding to the range of the protective layer cutting groove. The wall concrete cutting groove is a slot from the protective layer cutting groove to the outer layer steel reinforcement 11 of the well wall 5. The outer layer steel reinforcement 11 of the well wall 5 is set as a cut-off zone corresponding to the range of the wall concrete cutting groove. Inside the ventilation shaft, construction openings 31 are provided through the structural slab 1 of the first basement level, the middle slab 2 of the second basement level, and the structural slab 3 of the second basement level; a concrete cushion 7 is provided above the bottom slab of the third basement level space 4, with the elevation of the concrete cushion 7 reaching the lower side of the portal 9; a backfill structure is provided inside the third basement level space 4. The backfill structure includes a cement-soil filling section 8 and a mortar filling section 12. The cement-soil filling section 8 is frustoconical, with its bottom surface located in the middle of the concrete cushion layer 7 and each side surface being an upward sloping surface. The mortar filling section 12 is located above the sloping surface on each side of the cement-soil filling section 8.

[0018] In the backfill structure, the mortar filling section 12 and the cement-soil filling section 8 are fitted at an angle. When the tunnel boring machine (TBM) enters, the higher-strength mortar filling section 12 gradually transitions to the lower-strength cement-soil filling section 8. When the TBM exits, it gradually transitions from the cement-soil filling section 8 back to the mortar filling section 12, avoiding the instability risks brought about by sudden structural changes during TBM construction. Compared with the conventional backfill chamber filled with plain concrete in existing technologies, this design saves construction costs and avoids the situation where the TBM suddenly encounters a soft structural layer and head-down. Similarly, when the TBM exits the ventilation shaft section, it gradually transitions from a soft structural layer to a hard structural layer, thus protecting the stability of the TBM's tunneling.

[0019] After the tunnel boring machine passes through the ventilation shaft, an end-face sealing structure is installed on the inner wall of the shaft at the location of the tunnel opening, thereby sealing the tunnel opening and the gap between the tunnel segments and restoring the waterproofing of the ventilation shaft and the tunnel.

[0020] Specifically, the longitudinal length of the end reinforcement structure 6 on both sides of the shaft is 5m, and the reinforcement range is 3m of the outer contour of the tunnel structure.

[0021] As an alternative, the cover plate 13 is a precast reinforced concrete structural slab with a construction opening 31 on the upper side. Each end of the cover plate is 300mm larger than the construction opening 31. Reinforcing bars are set in the overlapping area of ​​the cover plate 13 and the construction opening 31. The upper end of the reinforcing bars is connected to the second basement structural slab 3. In this example, the cover plate 13 has good sealing stability.

[0022] Alternatively, the inner wall of the construction opening 31 is a sloping socket, and the cover plate 13 is a precast reinforced concrete structural slab. The cover plate 13 is installed inside the construction opening 31, and its periphery matches the sloping surface of the socket. It is also equipped with anchor bolts, which are perpendicular to the sloping surface of the socket and penetrate the cover plate 13 and the second-floor structural slab 3, inserting into the third-floor space 4. A grouting port is provided on the surface of the cover plate 13. Optionally, during construction, the cover plate 13 is installed before the grouting of the mortar filling part 12. Grout is injected into the interior through the grouting port, and air is vented through the gap between the cover plate 13 and the sloping socket. When the mortar fills to the top surface, the gap is further sealed, thereby fixing the cover plate 13 to the construction opening 31. The bolts are also embedded in the mortar filling part 12. Alternatively, the cover plate 13 can be installed after the mortar filling part 12 is grouted, and the bolt rods are inserted into the mortar for anchoring. The bottom surface of the cover plate 13 is bonded to the mortar filling part 12. This method is more convenient when the cover plate 13 is removed later.

[0023] Optionally, the end-face closure structure is a ring beam 15 covering the opening of the shaft wall 5 and the periphery of the end of the shield tunnel segment 14. The ring beam 15 is a concrete structure with an internal ring-shaped steel lattice. After the shield passes through, the tunnel segments inside the ventilation shaft are removed, the tunnel segments around the opening are cut off, the steel lattice frame is tied along the opening, the mold is installed, concrete is poured, and after reaching a certain strength, it is cured.

[0024] The following describes the specific construction process of the above-mentioned structural design, combined with... Figures 1-8 This plan is described in detail.

[0025] Construction method for directly tunneling a shield tunnel through an inter-section ventilation shaft: S1: When constructing the ventilation shaft in the interval, the diaphragm wall is constructed as a whole, and the shaft is waterproofed to form an internal shaft.

[0026] S2: Reinforce the tunnel ends at the external tunnel shaft. Specifically, use the sleeve valve pipe grouting reinforcement method to form a cast-in-place structure with a longitudinal length of more than 5m and a range of more than 3m from the outer contour of the tunnel structure.

[0027] S3: Backfill the space inside the shaft where the tunnel boring machine is located. The specific operation steps are as follows: 1) Construct a concrete cushion layer 7 on the surface of the bottom slab of the third basement level 4, using M2.5 mortar concrete, and construct it to the lower side of the portal 9. 2) Before backfilling, obstacles such as hard lumps, steel bars, and iron parts with a particle size greater than 150mm that may affect the tunnel boring machine should be cleared away. 3) The top slab of the third basement level (i.e., the structural slab 3 of the second basement level) and the side walls and end walls of the third basement level are all covered with 10cm thick color steel plate double-layer cored polystyrene composite board (1.00mm core thickness 100V220 / 880) to buffer the force on the top slab when the shield tunnel enters the station; 4) Start filling the concrete cushion layer 7 with cement soil. Leave a 2m gap between the cement soil and the tunnel entrance 9 on both sides. Backfill with a slope. The backfill height is controlled at 4.2m. Backfill with a slope with a slope of no more than 50°. The platform width is no less than 1.2m. The backfilled cement soil is compacted in layers. The thickness of each layer is controlled at 20-30cm. Leave a gap between the top and the second basement structural slab 3 for equipment operation.

[0028] S4: When the tunnel boring machine is nearing its arrival, the portal 9 will be demolished. The demolition of portal 9 at the high and low mileage ends of the left line of the ventilation shaft will be carried out simultaneously. Portal 9 in the cylinder wall will be manually demolished using a high-pressure pneumatic pick. The cylinder wall thickness is 1000mm, and the demolition work will be carried out in three layers: 1) Protective layer removal groove: First, remove the 70mm protective layer on the outer side of the well wall 5, and then cut off the inner reinforcing steel. 2) Break through the concrete in the middle of the 860mm thick wall from top to bottom; 3) Cut off the outer layer of steel reinforcement and retain a 70mm thick protective layer on the inner side of the well wall.

[0029] After S5 and portal 9 are demolished, the second layer of backfill is carried out. The backfill cement soil height is 6.2m. The backfill cement soil is compacted in layers, with the thickness of each layer controlled between 20cm and 30cm, and filled to the upper limit of the operating height. The trapezoidal area reserved at both ends of portal 9 is backfilled with mortar, and mortar is backfilled 1.3m below the second basement structural slab 3, with a total backfill height of 8.29m.

[0030] S6: Install a cover plate 13 on the construction opening 31 of the third basement level slab (i.e., the second basement level structural slab 3). The cover plate 13 is 500mm thick, and its coverage area is 300mm larger than the construction opening 31 at each end. The cover plate extends 300mm outward from the construction opening 31, completely covering the construction opening 31. The extended area is connected to the second basement level slab 2 using double-row HRB400 steel bars with a diameter of 28@150. The main and distribution bars are double-layered, bidirectional HRB400 steel bars with a diameter of 28@150, and the tie bars are HRB400 steel bars with a diameter of 12@300x300. The cover plate 13 is temporarily sealed with C35 concrete. Backfill reinforcement soil from the bottom of the steel ring of the portal 9 to the lower part of the temporary cover plate 13, and compact the backfill soil to ensure that the backfill soil is dense.

[0031] The removal of portal 9 should be carried out continuously to minimize the operation time. After the removal is completed, the concrete blocks and other debris inside portal 9 should be cleaned up immediately.

[0032] S7: Shield tunneling station passage. The tunneling parameters when the shield tunnels pass through the ventilation shaft are: The specific tunneling construction steps are as follows: Before the tunnel boring machine (TBM) enters the ventilation shaft, the construction speed of the TBM is slowed down according to the actual situation. When it is 80 rings away from the ventilation shaft, a ground monitoring measurement, ground control point connection measurement, and tunnel traverse re-measurement are carried out. When it is 50 rings away from the ventilation shaft, the traverse is checked again and the preparation work for entering the station is inspected.

[0033] After the shield cutterhead reaches the backfill mortar area, the thrust and cutterhead rotation speed are reduced, and the advance speed is decreased.

[0034] When the tunnel boring machine enters and passes through the ventilation shaft, secondary grouting is carried out at the entrance in 5 rings to seal the entrance. The grout used is a two-component grout.

[0035] Grout: A cement-water glass two-component grout is used, consisting of component A (water + cement) and component B (water glass + water). 1-day strength ≥ 0.3 MPa, 28-day strength ≥ 3.0 MPa.

[0036] Initial setting time: Under normal circumstances, the initial setting time should not exceed 30-50 seconds. Under special circumstances, it can be adjusted according to the geological conditions and tunneling speed.

[0037] Grouting sequence: The general sequence is to start from both sides of the tunnel, first grouting the side where there may be larger voids, then grouting the top and then the bottom. Alternatively, it can be adjusted to be carried out at multiple points simultaneously according to the site conditions. After grouting is completed, the grouting holes are sealed.

[0038] S8: After the shield tunneling is completed, first remove the cover plate 13, then excavate the backfill soil above the shield segment 14 in the third basement level space 4. Excavate both cement soil and mortar to the horizontal line of the segment center, and begin breaking the upper shield segment 14; then break the lower shield segment 14. After the lower shield segment 14 is broken, excavate the remaining backfill material and cut off any excess shield segment 14 at the shield tunnel opening. Here, the shield tunnel opening refers to the hole formed in the shaft wall 5 after the shield passes through.

[0039] After the two tunnel boring machines (TBMs) passed through one after another, grouting was carried out on the entry and exit sections to seal the gap between the tunnel entrance ring and the TBM segment 14. After no water flowed out of the test hole, backfilling and excavation were carried out in the ventilation shaft. The excavation was carried out by a PC200 mini excavator in conjunction with manual excavation. The excavated soil was transported to the hoisting hole and lifted out. When the excavation reached the top of the tunnel, the backing steel plates of the tunnel entrance ring and the entry and exit ring were welded and sealed with arc steel plates while excavating. The segments in the ventilation shaft were removed and lifted out after the TBMs advanced 70 rings.

[0040] When the tunnel boring machine (TBM) enters the end reinforcement zone and tunnels in the ventilation shaft, the thrust is relatively small, which can cause the tunnel segments to loosen. Therefore, when removing the tunnel segments, it is necessary to tighten the 10 rings of tunnel segments in the tunnel section.

[0041] Details of the dismantling and hoisting of tunnel segment 14: The crane used is a 130t truck crane, which can be positioned either to the side or directly in front of the end shaft.

[0042] A special bolt is passed through the bolt hole of the target segment and then secured to the wire rope of the truck crane. The truck crane slowly lifts the wire rope, keeping it taut but not under tension. The longitudinal connecting bolt nuts are removed, and the segment bolts are used as jacking tools. A hammer is used to strike the segment bolts, thus jacking out the longitudinal connecting bolts. Then, the circumferential connecting nuts on both sides are removed, and the circumferential connecting bolts are removed in the same way. The crane hook is then lifted vertically to the ground. If the segment is too tight to be pulled out, a pry bar can be used manually to pry it out horizontally. Other segments are removed in the same way. For safety and stability, the last (or two) circumferential bolts should not be completely removed. They can be pulled out using the lifting hook when 1 / 4 to 1 / 3 of the bolt remains.

[0043] S9: Shield Tunnel Portal Sealing. Construct ring beam 15 at the shield tunnel portal on the side wall of the ventilation shaft to seal the gap between the shield tunnel portal and the tunnel lining segments on the cylindrical wall, and simultaneously implement waterproofing measures.

[0044] This plan designs different stages of construction structure for the ventilation shaft. Before the shield tunneling, the integrity of the shaft is ensured to guarantee waterproofing. When the shield tunneling is about to arrive, the opening is quickly broken to protect the inner concrete protective layer. After the opening is broken, the shield tunneling is immediately installed and passed through. Then, backfilling and excavation are carried out, the tunnel lining segments are removed, and the opening is sealed. The construction time is short, and the time for groundwater to seep into the shaft is short in hydrogeological conditions, thus effectively ensuring the safety of the project.

[0045] The above description is only a preferred embodiment of the present utility model and does not limit the scope of the present utility model. All equivalent changes made based on the content of the present utility model specification and its drawings are included within the scope of the present utility model.

Claims

1. A construction structure for a ventilation shaft for direct shield tunneling, the main structure of which spans the left and right tunnels, including a diaphragm wall shaft, wherein the shaft contains a first-level negative structural slab (1), a second-level negative middle slab (2), and a third-level negative structural slab (3) for separating spaces, and below the second-level negative structural slab (3) is a third-level negative space (4) of the stratum where the tunnel is located, characterized in that: Outside the shaft, the negative three-layer space (4) has end reinforcement structures (6) on the outer sides of the opposite sides of the shaft wall along the shield direction. The cross section of the end reinforcement structure (6) is larger than the shield cutting surface. The well wall (5) at the inner end of the end reinforcement structure (6) is provided with a doorway (9). The doorway (9) includes a protective layer cutting groove and a wall concrete cutting groove. The protective layer cutting groove is a slot formed by removing the steel reinforcement protective layer on the inner surface of the well wall (5). The inner layer steel reinforcement (10) of the well wall (5) is set as a cut-off zone corresponding to the range of the protective layer cutting groove. The wall concrete cutting groove is a slot from the protective layer cutting groove to the outer layer steel reinforcement (11) of the well wall (5). The outer layer steel reinforcement (11) of the well wall (5) is set as a cut-off zone corresponding to the range of the wall concrete cutting groove. A concrete cushion layer (7) is set on the bottom slab of the third basement level, and the elevation of the concrete cushion layer (7) reaches the lower side of the portal (9); a backfill structure is set in the third basement level (4), which includes a cement-soil filling part (8) and a mortar filling part (12). The cement-soil filling part (8) is frustum-shaped, and its bottom surface is located in the middle of the concrete cushion layer (7). Each side is an upward sloping surface; the mortar filling part (12) is located on the upper side of the sloping surface of each side of the cement-soil filling part (8). Construction openings (31) are provided through the first basement structural slab (1), the second basement middle slab (2), and the second basement structural slab (3), and a cover plate (13) is installed on the construction openings (31).

2. The construction structure for a ventilation shaft in a section where a shield tunnel passes directly, as described in claim 1, is characterized in that: After the tunnel boring machine passes through the ventilation shaft, an end-face sealing structure is installed at the tunnel entrance on the inner wall of the shaft.

3. The construction structure for a ventilation shaft in a section for direct shield tunneling as described in claim 1, characterized in that: The inner wall of the construction opening (31) is a sloping socket, and the cover plate (13) is a precast reinforced concrete structural slab. The cover plate (13) is installed inside the construction opening (31). The periphery of the cover plate (13) matches the sloping surface of the socket. An anchor bolt rod is also provided, which is perpendicular to the sloping surface of the socket and penetrates the cover plate (13) and the second basement structural slab (3) and is inserted into the third basement space (4). A grouting port is provided on the surface of the cover plate (13).

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