Urban rail transit station structure and construction method with shallow-buried excavation and limited dewatering

Abstract

The invention city rail transit shallow-buried excavation limited dewatering station structure and construction method belongs to the technical field of underground engineering, and aims to realize the non-dewatering construction of the shallow-buried excavation station under the condition that the underground water level is high or the station is deeply buried in the water-rich stratum. The invention comprises a water stop system and a structure system. The water stop system comprises a dewatering pilot tunnel and a water stop curtain. The dewatering pilot tunnel is located above the water level line, and the water stop curtain extends downward in the dewatering pilot tunnel to the impervious layer. The structure system comprises a side pilot tunnel, a middle pilot tunnel, an advanced support, a first layer of primary support structure, a second layer of primary support structure and a main body secondary lining structure. The water stop curtain is arranged in the dewatering pilot tunnel which is independent of the main body pilot tunnel to implement dewatering, effectively solving the situation that the construction cannot be carried out when the water level line is located above the main body pilot tunnel. The water stop curtain is additionally arranged to avoid the dewatering problem in the station construction process and effectively control the surrounding building settlement. The dewatering pilot tunnel is located outside the station, and its arrangement position is flexible. The underground pipeline can be avoided according to the actual situation.

Description

Technical Field

[0001] The present invention belongs to the technical field of underground engineering, specifically a structure and construction method of a limited dewatering shallow buried and mined station for urban rail transit. Background Art

[0002] In the traditional shallow buried and mined method for urban rail transit, dewatering wells are set on the ground surface for dewatering before construction. As the urban road traffic volume continues to increase, the construction conditions for setting dewatering wells on the ground surface become increasingly harsh. At the same time, the selected site of the mined station is relatively close to buildings. A large amount of dewatering often causes the surface deformation to exceed the limit and the buildings to settle unevenly and crack. These factors have gradually prohibited a large amount of dewatering during the construction of the mined station. Therefore, the mined method based on conventional dewatering will no longer be applicable.

[0003] Currently, there has emerged a technology for stopping water in a mined station by constructing a water-stop curtain using the excavation pilot tunnel of the station, that is, constructing a water-stop curtain using the construction pilot tunnel of the station within the scope of the new station. However, with the development of projects such as groundwater protection and groundwater recharge, the urban groundwater level has gradually risen; in order to avoid existing lines, the buried depth of the mined station for the new line will continue to be lowered. Due to these two factors, it is impossible for the pilot tunnel of the shallow buried and mined method station to be completely above the groundwater level, and the risk of underground station operation with water is extremely high. There are currently no relevant patents to solve this problem.

[0004] Currently, the urban groundwater level has risen, and there may be more leakage problems during the later operation of the station, and it is necessary to strengthen the treatment of weak waterproof nodes of the structure. The conventional bored pile method is to continue to excavate the soil downward to the bottom plate after completing the second lining and arch closure, construct the bottom plate cushion layer and waterproof layer, pour the bottom plate, side walls and other second lining structures, and finally connect with the completed second lining arch part. In the construction process of this kind of station, since the concrete of the arch top is poured first, it is easy to produce weak waterproof areas with the later poured concrete such as the side walls, which is not conducive to the formation of an overall waterproof system for the station. Summary of the Invention

[0005] The purpose of the present invention is to provide a structure and construction method of a limited dewatering shallow buried and mined station for urban rail transit, which can realize the construction of a shallow buried and mined station for urban rail transit in a waterless environment under the condition of a high groundwater level or a deep buried station in a water-rich stratum. At the same time, a station structure supporting this construction method is provided, which can realize rapid construction in a water-rich stratum and can better reduce leakage.

[0006] The technical solution adopted by the present invention is: a structure of a limited dewatering shallow buried and mined station for urban rail transit, including a water-stop system and a structure system; the water-stop system includes a dewatering pilot tunnel, a water-stop curtain and a dewatering well. The dewatering pilot tunnel is above the water level line, and the water-stop curtain extends downward in the dewatering pilot tunnel to the impervious layer; dewatering wells are drilled in the dewatering pilot tunnel to drain the limited amount of water in the area surrounded by the water-stop curtain and the impervious layer.

[0007] The structural system includes a side tunnel, a central tunnel, advanced support, a first-layer primary support structure, a second-layer primary support structure, and a main secondary lining structure.

[0008] The side guide tunnel and the central guide tunnel are located at the arch of the station; the side walls of the side guide tunnel are provided with side piles and pile cap beams, the side piles extend downward to the bearing layer, and the pile cap beams are provided at the top of the side piles; a central pile is provided at the center of the central guide tunnel, the central pile extends downward to the bearing layer; the first layer of initial support structure connects the side guide tunnel and the central guide tunnel; the second layer of initial support structure connects the pile cap beams at the top of the side piles and the central piles, and the second layer of initial support structure is located inside the first layer of initial support structure; the main secondary lining structure is located inside the second layer of initial support structure.

[0009] Furthermore, the first layer of initial support structure is formed by spraying concrete onto a grid steel frame. The steel frame includes a side arch section located in the side guide tunnel, a connecting arch section located in the middle guide tunnel, and a middle arch section located between the side guide tunnel and the middle guide tunnel. The middle arch section connects the side arch section and the middle arch section. The side arch section is connected to the initial support steel frame of the corresponding side guide tunnel itself, and the connecting arch section is the arch top of the middle guide tunnel itself.

[0010] Furthermore, the structural system includes a waterproof layer, which is laid on the back side of the main secondary lining structure.

[0011] Furthermore, the main secondary lining structure is cast from bottom to top, and the waterproof layer is laid sequentially from bottom to top.

[0012] Furthermore, the side piles and the pile cap beams are reinforced concrete structures; the central piles are constructed along their vertical steel pipe columns and the reinforced concrete structure below the steel pipe columns, with coarse sand filling the space between the steel pipe columns and the steel sleeves.

[0013] Furthermore, the second-layer initial support structure includes an arched section and a top longitudinal beam, the top longitudinal beam being connected to the top of the steel pipe column; one end of the arched section is connected to the top longitudinal beam, and the inner side of the arch foot at the other end is enlarged to form an enlarged arch foot, the enlarged arch foot including a reinforced concrete arch foot and a steel connecting block, the outer side of the enlarged arch foot being connected to the arched section, and the top end being connected to the arched section through the steel connecting block.

[0014] The construction method for shallow-buried and cut-and-cover stations in urban rail transit includes the following steps:

[0015] S1. Construct a dewatering guide tunnel on the outside of the initial support outline of the station. The dewatering guide tunnel is set above the water level line. After the dewatering guide tunnel is completed, construct a water-stop curtain to the impermeable layer inside the dewatering guide tunnel.

[0016] S2. Drill dewatering wells in the dewatering tunnel to the design elevation to pump out the limited amount of water in the area surrounded by the water-stop curtain and impermeable layer;

[0017] S3. Excavate the side and central guide tunnels of the station using the cross passage, construct side piles in the side guide tunnels, and construct central piles in the central guide tunnels.

[0018] S4. Cast the pile cap beam at the top of the side pile, construct the side arch section of the first layer of initial support structure, and support the arch foot of the side arch section on the pile cap beam. Backfill behind the side arch section.

[0019] S5. Use the cross passage to construct advanced support between the side tunnel and the central tunnel. Under the advanced support, excavate the soil, erect a steel frame, and connect the steel frame in the structure of the side tunnel and the central tunnel of the station. Shot concrete is sprayed to form the first layer of the initial support structure of the station.

[0020] S6. Construct the second layer of initial support structure inside the first layer of initial support structure. The second layer of initial support structure is a continuous arch structure, forming a large arch foot at the side piles and the middle piles to realize the initial support arch of the upper part of the station.

[0021] S7. Excavate the soil below the second layer of initial support structure, and install multiple steel supports in sequence. As the excavation is carried out, the pile-to-pile mesh spraying support is applied. After the excavation reaches the design elevation, the foundation should be leveled in time, the water in the pit should be drained, and the foundation should be sealed with a cushion layer in time.

[0022] S8. Remove the bottom steel support layer by layer from bottom to top, lay the corresponding waterproof layer and cast the main secondary lining structure in place.

[0023] Furthermore, during the excavation of the S7 soil, local grouting was performed to seal the seepage points.

[0024] Furthermore, in steps S1 and S3, the advanced support scheme for the pilot tunnel is adjusted according to the geological conditions of the surrounding rock at the tunnel entrance, and grouting measures are added.

[0025] The beneficial effects of this invention are as follows: This invention implements dewatering by setting up a water-stop curtain in a dewatering guide tunnel independent of the main guide tunnel, effectively solving the problem of construction being impossible when the water level is above the main guide tunnel; compared with conventional underground station construction methods, the addition of a water-stop curtain avoids dewatering problems during station construction, effectively controlling excessive ground deformation and uneven building settlement; the dewatering guide tunnel is located outside the station, and its layout is more flexible, allowing it to avoid underground pipelines according to actual conditions; the addition of a dewatering guide tunnel avoids the need for road occupation for conventional dewatering or water-stop curtain construction, reducing the impact on ground traffic; during the excavation of the main station soil, engineering measures can be adopted in the dewatering guide tunnel to strengthen the water-stopping nodes according to the leakage situation during the main station excavation process, without interfering with the construction of the main station area.

[0026] The adoption of a double-layer initial support structure, with a first-layer initial support structure and a second-layer initial support structure, can simultaneously ensure timely support and enhance the load-bearing effect of the initial support. During the construction of the first-layer initial support, support is provided simultaneously with excavation to avoid prolonged soil exposure and potential local collapse, thus promptly forming a support system and reducing ground settlement. The second-layer initial support structure is rigidly connected to the side piles and center piles, forming a continuous and complete arched load-bearing structure. This evenly distributes the load to the retaining pile system, significantly enhancing the overall integrity of the station roof, controlling differential settlement, and creating favorable conditions for the bottom-up construction of the main secondary lining structure. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the construction of the station dewatering tunnel and water-stop curtain disclosed in this invention;

[0028] Figure 2 This is a schematic diagram of precipitation disclosed in this invention;

[0029] Figure 3 This is a schematic diagram of the construction of the side tunnel, side piles, central tunnel, and central piles disclosed in this invention.

[0030] Figure 4 This is a schematic diagram of the construction of the pile cap beam and the first layer of initial support structure disclosed in this invention;

[0031] Figure 5 This is a schematic diagram of the construction of the side tunnel and the central tunnel connected by the first layer of the initial support structure disclosed in this invention;

[0032] Figure 6 This is a schematic diagram of the construction of the second-layer initial support structure disclosed in this invention;

[0033] Figure 7 This is a schematic diagram of the soil excavation within the main body of the station disclosed in this invention;

[0034] Figure 8 This is a schematic diagram of the pouring of the base slab of the secondary lining structure of the station main body disclosed in this invention;

[0035] Figure 9 This is a schematic diagram of the pouring of the side walls and middle slab of the secondary lining structure of the station main body disclosed in this invention;

[0036] Figure 10 This is a schematic diagram of the pouring of the top slab of the secondary lining structure of the station main body disclosed in this invention;

[0037] Figure 11 This is a schematic diagram of the cross-section of the precipitation guide tunnel, the side guide tunnel, and the central guide tunnel disclosed in this invention;

[0038] Figure 12 This is a structural diagram of the central column disclosed in this invention;

[0039] Figure 13 This is a structural diagram of the second layer of the initial support structure disclosed in this invention;

[0040] Figure 14 This is a detailed drawing of the second layer of the initial support structure disclosed in this invention.

[0041] In the diagram, the following structures are included: 1. Dewatering guide tunnel; 2. Steel grid frame and shotcrete; 3. Small guide pipe; 4. Large pipe shed; 5. Waterproof curtain; 6. Water level line; 7. Impermeable layer; 8. Dewatering well; 9. Side guide tunnel; 10. Middle guide tunnel; 11. Side pile; 11. Middle pile; 12. Steel sleeve; 13. Steel pipe column; 14. Coarse sand; 15. Reinforced concrete structure under column; 16. Pile top cap beam; 17. Plain concrete; 18. First layer initial support structure; 19. Side arch section; 10. Connecting arch section; 11. Middle arch section; 12. Advanced support; 13. Second layer initial support structure; 14. Top longitudinal beam; 15. Arch section; 16. Enlarged arch foot; 17. Reinforced concrete arch foot; 18. Steel connecting block; 19. Steel support; 20. Waterproof layer; 21. Main secondary lining structure. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0043] The structure of shallow-buried tunnel stations for urban rail transit with limited dewatering includes a water-stopping system and a structural system;

[0044] The water-stopping system includes a dewatering tunnel 1 and a water-stopping curtain 2. The dewatering tunnel 1 is located above the water level line 3 and outside the initial support outline of the station. The water-stopping curtain 2 extends downwards into the impermeable layer 4 within the dewatering tunnel 1.

[0045] The dewatering guide tunnel 1 is specifically used for constructing the water-stop curtain 2. Located outside the initial support outline of the station, it does not encroach on the main station construction area, and its construction will not interfere with the main station construction. The dewatering guide tunnel 1 is independent of the station's side guide tunnels 6-1 and central guide tunnel 6-2, providing a waterless working environment under high water levels and avoiding the drawbacks of relying on the main guide tunnels for dewatering. Because the dewatering guide tunnel 1 is independent of the main guide tunnels, the water-stopping effect can be monitored in real time within the dewatering guide tunnel 1, and additional water-stopping measures (such as interlocking piles) can be installed to strengthen the joints without interfering with the main construction.

[0046] In this embodiment, the top of the dewatering tunnel 1 structure is supported by advanced support such as large pipe shed 1-3 and small pipe 1-2, and its initial support structure is a grid steel frame and shotcrete 1-1.

[0047] The structural system includes a side tunnel 6-1, a central tunnel 6-2, advanced support 12, a first-layer initial support structure 11, a second-layer initial support structure 13, and a main secondary lining structure 16. The side tunnel 6-1 and the central tunnel 6-2 are located at the arch of the station, and their structures are similar to those of the dewatering tunnel 1. The top is supported by advanced support such as a large pipe shed 1-3 and small pipes 1-2, and their own initial support structure is a grid steel frame and shotcrete 1-1.

[0048] Side piles 7 and pile cap beams 9 are installed at the side walls of the side tunnel 6-1. The side piles 7 extend downward to the bearing layer, and the pile cap beams 9 are located at the top of the side piles 7. A central pile 8 is installed at the center of the central tunnel 6-2, and the central pile 8 extends downward to the bearing layer. The side piles 7 and pile cap beams 9 are reinforced concrete structures, which have good stability.

[0049] The first-layer initial support structure 11 connects the side guide tunnel 6-1 and the central guide tunnel 6-2. The first-layer initial support structure 11 consists of a grid steel frame and shotcrete, and the gap between its back side and the side guide tunnel 6-1 is filled with plain concrete 10. The initial support steel frames of the side guide tunnel 6-1 and the central guide tunnel 6-2 are connected to the initial support steel frame of the first-layer initial support structure 11. The second-layer initial support structure 13 connects the pile cap beam 9 at the top of the side pile 7 and the central pile 8, and the second-layer initial support structure 13 is located inside the first-layer initial support structure 11; the main secondary lining structure 16 is located inside the second-layer initial support structure 13.

[0050] This invention implements dewatering by setting up a water-stop curtain 2 in a dewatering guide tunnel 1 that is independent of the main guide tunnel. This effectively solves the problem of construction being impossible when the water level is above the main guide tunnel. Compared with conventional tunneling methods for railway stations, the addition of a water-stop curtain avoids dewatering issues during station construction. The dewatering guide tunnel is located outside the station, allowing for flexible placement and the ability to avoid underground pipelines depending on the actual situation. The addition of a dewatering guide tunnel avoids the need for road closures for conventional dewatering or water-stop curtain construction, reducing the impact on ground traffic. When excavating the main station soil, engineering measures can be used in the dewatering guide tunnel to strengthen the water-stopping nodes based on leakage during the main station excavation process, without interfering with the construction of the main station area.

[0051] This invention employs a double-layer initial support structure, consisting of a first-layer initial support structure 11 and a second-layer initial support structure 13, which offers the following advantages: Firstly, after the side piles 7 and the pile cap beam 9 are formed, the first-layer initial support structure 11 immediately constructs a local arched support, such as a side arch, to quickly transfer the top load to the side piles 7 and the pile cap beam 9. This avoids prolonged soil exposure leading to settlement, reduces the suspension time of the soil between the guide tunnels, prevents local collapse, and provides a stable working surface for the second-layer initial support. The second-layer initial support structure 13 is rigidly connected to the side piles 7 and the central piles 8, forming a continuous and complete arched load-bearing structure. This evenly distributes the load to the retaining pile system, significantly enhancing the overall integrity of the station roof and controlling differential settlement.

[0052] Secondly, the double-layer initial support layer controls deformation: the first layer of initial support structure 11 seals the soil between the guide tunnels and inhibits the loosening of shallow soil; after the second layer of initial support structure 13 is arched, the main earthwork is excavated downwards to avoid the instability of the working face caused by large-scale excavation at one time. It is especially suitable for water-rich sandy layers and reduces the construction accident rate.

[0053] Thirdly, after the double-layer initial support structure forms a stable arch shell, the main secondary lining structure can be constructed from bottom to top, which can solve the leakage problem of the post-cast strip at the arch crown in the traditional reverse construction method and improve the overall waterproof reliability. This avoids the need for the secondary lining structure at the arch crown to reach its strength before continuing to excavate downwards in the conventional underground excavation method, reducing waiting time and saving construction period.

[0054] The first-layer initial support structure 11 is formed by spraying concrete onto a grid steel frame. The steel frame includes a side arch section 11-1 located in the side guide tunnel 6-1, a connecting arch section 11-2 located in the central guide tunnel 6-2, and a central arch section 11-3 located between the side guide tunnel 6-1 and the central guide tunnel 6-2. The central arch section 11-3 connects the side arch section 11-1 and the central arch section 11-3. The side arch section 11-1 is connected to the initial support steel frame of the corresponding side guide tunnel 6-1, and the connecting arch section 11-2 forms the arch crown of the central guide tunnel 6-2. This structure, where the first-layer initial support structure 11 is connected to the initial support structures of the side guide tunnel 6-1 and the central guide tunnel 6-2 to form a whole, ensures good stability of the steel frame of the first-layer initial support structure 11. The side arch section 11-1 and the connecting arch section 11-2 provide supports for the construction of the central arch section 11-3.

[0055] The structural system includes a waterproof layer 15, which is laid on the back side of the main secondary lining structure 16. The waterproof layer 15 is laid at the bottom between the base and the main secondary lining structure 16, at the side walls between the side piles 7 and the main secondary lining structure 16, and at the top between the second primary support structure 13 and the main secondary lining structure 16.

[0056] The main secondary lining structure 16 is cast from bottom to top, and the waterproof layer 15 is laid sequentially from bottom to top. This allows for the construction of the main secondary lining structure 16 and the laying of the waterproof layer 15 from bottom to top, avoiding the need for conventional tunneling methods where the secondary lining structure at the arch crown must reach sufficient strength before further excavation can proceed. This reduces waiting time, saves construction time, facilitates the laying of the waterproof layer and concrete pouring, solves the leakage problem of the post-cast strip at the arch crown in traditional reverse construction methods, and improves the overall reliability of waterproofing.

[0057] In this embodiment, depending on the geological conditions, the side piles 7 include, but are not limited to, prestressed pipe piles, H-shaped steel columns, rotary drilling cast-in-place piles, long spiral piles, and mud wall cast-in-place piles.

[0058] The central pile 8 vertically comprises a steel pipe column 8-2 and a reinforced concrete structure 8-4 beneath the steel pipe column 8-2. The space between the steel pipe column 8-2 and its steel sleeve 8-1 is filled with coarse sand 8-3. Later, reinforcing bars will be tied to the central pile 8 and concrete will be poured, serving as a permanent central column for the station's main structure. The central pile 8 is located at the center of the central tunnel 6-2 and needs to bear most of the arch load. The coarse sand 8-3 filling between the steel pipe column 8-2 and the steel sleeve 8-1 forms a compressible layer to absorb vibration energy.

[0059] The second-layer initial support structure 13 includes an arched section 13-2 and a top longitudinal beam 13-1. The top longitudinal beam 13-1 is connected to the top of the steel pipe column 8-2, i.e., the steel pipe column 8-2 is inserted into the top longitudinal beam 13-1. One end of the steel frame of the arched section 13-2 is connected to the top longitudinal beam 13-1, and the other end is enlarged at the inner side of the arch foot to form an enlarged arch foot 13-3. The enlarged arch foot 13-3 includes a reinforced concrete arch foot 13-3-1 and a steel connecting block 13-3-2. The outer side of the enlarged arch foot 13-3 is connected to the arched section 13-2, and the top end is connected to the arched section 13-2 through the steel connecting block 13-3-2. The arched section 13-2 is a grid steel frame and shotcrete structure, and the top longitudinal beam 13-1 is a reinforced concrete structure. The reinforced concrete arch foot 13-3-1 increases the arch foot area at the side arch. The support reaction force at the arch foot is large, and the poor soil conditions prevent the provision of high foundation bearing capacity. In this embodiment, a large arch foot is used to reduce the pressure and meet the soil bearing capacity requirements. The second-layer initial support structure 13 is rigidly connected to the side piles 7 and the central piles 8 through the large arch foot structure, forming a continuous and complete arched bearing structure. This evenly distributes the load to the retaining pile system, significantly enhancing the overall integrity of the station roof, controlling differential settlement, and reducing the measured settlement by more than 15%.

[0060] The construction method for shallow-buried, cut-and-cover stations with limited precipitation in urban rail transit includes the following steps:

[0061] S1. Construct a dewatering tunnel 1 on the outer side of the initial support outline of the station. The dewatering tunnel 1 is located above the water level line 3. After the dewatering tunnel 1 is completed, construct a water-stop curtain 2 to an impermeable layer 4 inside the dewatering tunnel 1. In this way, the water-stop curtain 2 forms a closed water barrier to surround the station construction area and isolate groundwater.

[0062] S2. Drill dewatering wells 5 to the design elevation in the dewatering tunnel 1 to pump out the limited water volume within the area enclosed by the water-stop curtain 2 and the impermeable layer 4. Pumping out the limited water volume within the area enclosed by the water-stop curtain 2 through the dewatering wells 5 creates a waterless construction environment in the water-rich strata. By enclosing the station area with the water-stop curtain 2, water from outside the water-stop curtain 2 is prevented from entering the station area, thus controlling the water volume within the area enclosed by the water-stop curtain 2. Therefore, the water to be pumped out is a limited amount of water within the station area, not a traditional, continuous flow of water. In this way, limited dewatering creates a waterless construction environment for subsequent station construction, effectively controlling the water volume outside the water-stop curtain while meeting the station's waterless construction requirements, effectively preventing settlement and deformation of surrounding buildings.

[0063] S3. Excavate the side guide tunnel 6-1 and the central guide tunnel 6-2 of the station using the cross passage. Construct side piles 7 in the side guide tunnel 6-1 and central piles 8 in the central guide tunnel 6-2.

[0064] S4. Cast the top cap beam 9 on the top of the side pile 7, construct the side arch section of the first layer of initial support structure 11, and support the arch foot of the side arch section on the top cap beam 9. Backfill behind the side arch section.

[0065] S5. Using the cross passage, construct the advanced support 12 between the side guide tunnel 6-1 and the middle guide tunnel 6-2. Excavate the soil under the advanced support 12, erect a steel frame, connect the steel frame in the structure of the side guide tunnel 6-1 and the middle guide tunnel 6-2 of the station, and spray concrete to form the first layer of the initial support structure 11 of the station.

[0066] S6. Construct the second layer of initial support structure 13 inside the first layer of initial support structure 11. The second layer of initial support structure 13 is a continuous arch structure, forming a large arch foot at the side pile 7 and the middle pile 8, realizing the initial support arch of the upper part of the station.

[0067] S7. Excavate the soil below the second-layer initial support structure 13, and sequentially erect multiple steel supports 14. During excavation, inter-pile shotcrete support is installed. After excavation to the design elevation, the foundation should be leveled promptly, water in the pit drained, and a cushion layer constructed to seal the foundation. For example, in this embodiment, three steel supports 14 are erected, from top to bottom as the first, second, and third steel supports 14. As excavation progresses, the first, second, and third steel supports 14 are erected sequentially, and inter-pile shotcrete support is installed during excavation.

[0068] S8. Remove the bottommost steel support 14 layer by layer from bottom to top, lay the corresponding waterproof layer 15, and cast the main secondary lining structure 16 in place. The specific operation is as follows: First, remove the third steel support 14, lay the waterproof layer 15 at the bottom slab and lower section of the side walls, and construct the bottom longitudinal beam, bottom slab, and lower section of the side walls of the main secondary lining structure 16; next, remove the second steel support 14, lay the waterproof layer 15 at the middle section of the side walls, and construct the middle section of the side walls, the middle slab of the second basement level, and the middle longitudinal beam of the main secondary lining structure 16; finally, remove the first steel support 14, lay the waterproof layer 15 at the top section of the side walls, and construct the side walls, middle slab, and middle longitudinal beam of the first basement level of the main secondary lining structure 16. Lay the waterproof layer 15 on the top slab, and construct the top slab and top longitudinal beam of the main secondary lining structure 16.

[0069] In step S1, the water-stop curtain scheme can be adjusted according to geological conditions and engineering experience, such as jet grouting piles, mixing piles, diaphragm walls, and interlocking piles.

[0070] In steps S1 and S3, the advanced support scheme for the pilot tunnel can be adjusted according to the geological conditions of the surrounding rock at the tunnel entrance. For example, if the geological conditions of the dewatering pilot tunnel 1, the side pilot tunnel 6-1, and the central pilot tunnel 6-2 are poor, grouting and other measures can be added before excavation.

[0071] In step S3, the water volume in the hole is assessed based on the driving of the side piles and the middle piles to determine the effectiveness of the water-stopping curtain. In addition, plain interlocking piles are driven in the dewatering guide tunnel to supplement the water-stopping effect at the nodes.

[0072] In steps S5 and S6, grouting pipes can be pre-embedded during the construction of the first and second initial support structures. If water leakage occurs in the initial support structure during construction, grouting can be performed to seal the leak.

[0073] In step S8, grouting pipes can be pre-embedded in the secondary lining structure of the arch after the waterproof layer is laid. The grout fills the gap between the waterproof layer and the secondary lining structure in the arch, which is difficult to pour due to the concrete arch.

[0074] To reduce water leakage during excavation, local grouting was performed at the leakage points during the excavation of the S3 soil to enhance the water-stopping effect of the water-stopping curtain 2.

[0075] In the description of this specification, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0076] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art 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 appended claims and their equivalents.

Claims

1. A shallow-buried, tunnel-excavated station structure for urban rail transit with limited dewatering, characterized in that: Including waterproofing systems and structural systems; The water-stopping system includes a dewatering tunnel (1), a water-stopping curtain (2), and a dewatering well (5). The dewatering tunnel (1) is located above the water level line (3). The water-stopping curtain (2) extends downward into the impermeable layer (4) within the dewatering tunnel (1). A dewatering well (5) is installed in the dewatering tunnel (1) to pump out the limited amount of water within the area surrounded by the water-stopping curtain (2) and the impermeable layer (4). The structural system includes a side tunnel (6-1), a central tunnel (6-2), an advance support (12), a first-layer primary support structure (11), a second-layer primary support structure (13), and a main secondary lining structure (16). The side guide tunnel (6-1) and the central guide tunnel (6-2) are located at the arch of the station; the side guide tunnel (6-1) is provided with a side pile (7) and a pile cap beam (9) at the side wall, the side pile (7) extends downward to the bearing layer, and the pile cap beam (9) is provided at the top of the side pile (7); the central guide tunnel (6-2) is provided with a central pile (8) at the center, the central pile (8) extends downward to the bearing layer; the first layer of initial support structure (11) is connected between the side guide tunnel (6-1) and the central guide tunnel (6-2); the second layer of initial support structure (13) is connected between the pile cap beam (9) at the top of the side pile (7) and the central pile (8), and the second layer of initial support structure (13) is located inside the first layer of initial support structure (11); the main secondary lining structure (16) is located inside the second layer of initial support structure (13); The first layer of initial support structure (11) is formed by spraying concrete onto a grid steel frame. The steel frame includes a side arch section (11-1) located in the side guide tunnel (6-1), a connecting arch section (11-2) located in the middle guide tunnel (6-2), and a middle arch section (11-3) located between the side guide tunnel (6-1) and the middle guide tunnel (6-2). The middle arch section (11-3) connects the side arch section (11-1) and the connecting arch section (11-2). The side arch section (11-1) is connected to the initial support steel frame of the corresponding side guide tunnel (6-1). The connecting arch section (11-2) is the arch top of the middle guide tunnel (6-2). The second layer of initial support structure (13) includes an arched section (13-2) and a top longitudinal beam (13-1). The top longitudinal beam (13-1) is connected to the top of the steel pipe column (8-2). One end of the arched section (13-2) is connected to the top longitudinal beam (13-1), and the inner side of the arch foot at the other end is enlarged to form an enlarged arch foot (13-3). The enlarged arch foot (13-3) includes a reinforced concrete arch foot (13-3-1) and a steel connecting block (13-3-2). The outer side of the enlarged arch foot (13-3) is connected to the arched section (13-2), and the top end is connected to the arched section (13-2) through the steel connecting block (13-3-2).

2. The shallow-buried, tunnel-excavated, limited-water-depletion station structure for urban rail transit as described in claim 1, characterized in that: The structural system includes a waterproof layer (15), which is laid on the back side of the main secondary lining structure (16).

3. The shallow-buried, tunnel-excavated, limited-water-depletion station structure for urban rail transit as described in claim 2, characterized in that: The main secondary lining structure (16) is cast from bottom to top, and the waterproof layer (15) is laid sequentially from bottom to top.

4. The shallow-buried, tunnel-excavated, limited-dewatering station structure for urban rail transit as described in claim 3, characterized in that: The side piles (7) and the pile cap beams (9) are reinforced concrete structures; the central pile (8) includes a steel pipe column (8-2) and a reinforced concrete structure (8-4) under the steel pipe column (8-2) along its vertical direction, and the space between the steel pipe column (8-2) and its steel sleeve (8-1) is filled with coarse sand (8-3).

5. The construction method of the shallow-buried tunnel-excavated limited-dewatering station structure for urban rail transit as described in claim 1, characterized in that: Includes the following steps: S1. Construct a dewatering guide tunnel (1) on the outside of the initial support outline of the station. The dewatering guide tunnel (1) is set above the water level line (3). After the dewatering guide tunnel (1) is completed, construct a water-stop curtain (2) to the impermeable layer (4) inside the dewatering guide tunnel (1). S2. Drill a dewatering well (5) in the dewatering tunnel (1) to the design elevation and pump out the limited amount of water in the area surrounded by the water-stop curtain (2) and the impermeable layer (4); S3. Excavate the side guide tunnel (6-1) and the middle guide tunnel (6-2) of the station using the cross passage. Construct side piles (7) in the side guide tunnel (6-1) and middle piles (8) in the middle guide tunnel (6-2). S4. Cast the top cap beam (9) on the top of the side pile (7), construct the side arch section of the first layer of initial support structure (11), and support the arch foot of the side arch section on the top cap beam (9). Backfill plain concrete (10) behind the side arch section. S5. Using the cross passage, construct advanced support (12) between the side guide tunnel (6-1) and the middle guide tunnel (6-2). Under the advanced support (12), excavate the soil and erect a steel frame. The steel frame connects the steel frame in the structure of the side guide tunnel (6-1) and the middle guide tunnel (6-2) of the station, and spray concrete to form the first layer of the initial support structure (11) of the station. S6. Construct the second layer of initial support structure (13) inside the first layer of initial support structure (11). The second layer of initial support structure (13) is a continuous arch structure. Large arch feet are formed at the side piles (7) and the middle piles (8) to realize the initial support arch of the upper part of the station. S7. Excavate the soil below the second layer of initial support structure (13), and install multiple steel supports (14) in sequence. During the excavation, the piles are sprayed with mesh support. After excavating to the design elevation, the foundation should be leveled in time, the water in the pit should be drained, and the foundation should be sealed with a cushion layer in time. S8. Remove the bottom steel support layer by layer from bottom to top (14), lay the corresponding waterproof layer (15), and cast the main secondary lining structure in place (16).

6. The construction method for shallow-buried, tunnel-excavated, limited-dewatering station structures for urban rail transit as described in claim 5, characterized in that: During step S7, when the soil is being excavated, local grouting is performed to seal the seepage points.

7. The construction method for shallow-buried, tunnel-excavated, limited-water-depletion station structures for urban rail transit as described in claim 5, characterized in that: In steps S1 and S3, the advanced support scheme for the pilot tunnel is adjusted according to the geological conditions of the surrounding rock at the tunnel entrance, and grouting measures are added.

8. The construction method for shallow-buried, tunnel-excavated, limited-water-depletion station structures for urban rail transit as described in claim 5, characterized in that: In step S3, based on the water volume in the hole when the side piles (7) and the middle piles (8) are driven, the effect of the water-stopping curtain (2) is judged, and plain interlocking piles are driven in the dewatering guide tunnel (1) to supplement the water-stopping effect at the node.

Images