A subway station entrance and exit tunneling passage structure and construction process

Abstract

The application provides a subway station entrance and exit tunneling passage structure and construction process, and belongs to the technical field of subway construction, which comprises S1, a dewatering well construction, dewatering wells are arranged on both sides of the tunneling passage to reduce the underground water level and increase the stability of the soil body around the tunneling passage; S2, pipeline surrounding soil body grouting reinforcement, drilling and grouting are carried out around the pipeline before the tunneling construction to improve the overall mechanical properties of the pipeline surrounding soil body; the application avoids damaging the surrounding pipeline during the construction process by grouting reinforcement of the pipeline surrounding soil body, maximally reduces the risks possibly generated during the construction process, and further avoids delaying the construction progress. The waterproof structure mainly adopts two-lining concrete self-waterproofing, combines a fully-closed waterproof layer and two-lining backfill grouting, and adopts a double water-expanding sealing glue and grouting pipe mode for waterproof treatment at special positions where a water stop belt cannot be arranged, so that the waterproof effect of the waterproof structure is improved.

Description

Technical Field

[0001] This invention relates to the field of subway construction technology, specifically to a tunnel structure and construction process for subway station entrances and exits. Background Technology

[0002] The cut-and-cover method for subway construction refers to a subway construction method that, under specific conditions, involves excavation and construction of the lining structure entirely underground without excavating the surface. Because subway stations are typically built in urban centers with complex surrounding environments, numerous underground pipelines and above-ground buildings and structures, and heavy surface traffic, the cut-and-cover or top-and-bottom methods are often not feasible. In such cases, the cut-and-cover method becomes almost the only viable option.

[0003] The following problems were encountered during the construction of a subway tunnel in a certain city in the country:

[0004] 1. The main pipelines above the subway entrance / exit include sewage pipes, water supply pipes, heating pipes, and power lines. Among them, the deepest sewage pipe is only 2 meters away from the initial support, which is prone to causing damage to surrounding pipelines. In addition, the presence of sewage pipes, water supply pipes, and other pipelines makes it easier to encounter problems such as water leakage during construction.

[0005] 2. This tunnel section is mainly located in silty clay and clayey silt layers, which can easily lead to the collapse of the tunnel face during construction.

[0006] 3. Before the construction of the tunnel section, the retaining wall at the gate location must be removed to convert the load-bearing system. During the removal process, the gate is difficult to break and the construction risk is relatively high. Summary of the Invention

[0007] This invention provides a structure and construction process for a tunnel entrance / exit of a subway station, in order to solve the technical problems in the prior art.

[0008] To solve the above problems, the construction process for underground tunnels at subway entrances and exits provided by this invention adopts the following technical solution, including the following steps:

[0009] S1, Dewatering well construction: Dewatering wells are set up on both sides of the tunnel to lower the groundwater level and increase the stability of the soil around the tunnel.

[0010] S2, Grouting reinforcement of the soil around the pipeline: Before the underground excavation, drilling and grouting are carried out around the pipeline to improve the overall mechanical properties of the soil around the pipeline.

[0011] S3, Long pipe roof construction and full-section grouting: Several long pipe roofs are used as advance support for the arch of the tunnel. The long pipe roofs are arranged in an arch shape. Grouting is carried out to reinforce the soil within 2m outside the excavation outline of the tunnel. Then, double rows of advance small pipes are set above the long pipe roofs to ensure the stability of the excavation face.

[0012] S4, demolition of the horse-head gate: demolish the No. 1, No. 2, No. 3 and No. 4 openings of the horse-head gate in the order of upper left, lower left, upper right and lower right, and erect temporary horizontal and vertical supports.

[0013] S5, Excavation of the cut-and-cover tunnel: The CRD method is used to excavate the cut-and-cover tunnel; the upper bench section 1, lower bench section 2, upper bench section 3 and lower bench section 4 are excavated in sequence, and initial support, intermediate partition walls and intermediate partitions are installed in a timely manner.

[0014] S6, Initial support construction: Prepare steel arch frame and steel mesh. First, install the steel arch frame, then weld the steel mesh to the steel arch frame. After the steel mesh is welded, spray concrete in the order of arch foot first and arch top second. After the concrete has solidified, cure the concrete for no less than 14 days. Finally, perform grouting behind the initial support.

[0015] S7, Waterproofing layer and secondary lining construction: the central partition wall is removed intermittently, the waterproofing layer is laid and the bottom secondary lining is poured. The waterproofing layer includes a buffer layer and a waterproofing board. Then the central partition wall is removed intermittently, the waterproofing layer is laid and the upper secondary lining is poured.

[0016] S8, secondary lining backfill grouting, involves grouting the backfill behind the secondary lining through a grouting pipe.

[0017] As a further improvement, in S1, the construction process of the dewatering well includes drilling, hole completion, casing installation, filling with gravel and mud to seal the hole, and well washing.

[0018] The well casing is equipped with a water filter pipe, and the outside of the water filter pipe is wrapped with two layers of 80-100 mesh nylon mesh as a filter layer. A sedimentation pipe is also provided below the water filter pipe.

[0019] As a further improvement, in S2, grouting with sleeve valves is used to reinforce the soil within 2m before and after the pipeline along the direction of the underground tunnel, 2m above and below, and 2m outside the excavation outline. The spacing is 1×1m, arranged in a quincunx pattern. The grouting slurry is silicate cement slurry with a water-cement ratio of 1:1 and a slurry pressure of 0.2~0.3MPa.

[0020] As a further improvement, in S3, the construction process for the long pipe shed includes: constructing a guide wall, drilling, jacking the long pipe shed, cleaning the holes, and grouting. The circumferential spacing of the long pipe shed is 400mm, and the external insertion angle is 0.5°. During installation, the long pipe shed is installed in two sections, and the overlap length of the two sections is not less than 10% of the length of each section.

[0021] Within a 180° radius of the arch section, except at the tunnel entrance, double rows of advanced small guide pipes are installed. The advanced small guide pipes are 4m long, with a circumferential spacing of 300mm and an external insertion angle of 5-10°. Grouting holes are formed by staggered drilling every 150mm along the pipe wall. The hole diameter is 6mm, and the grouting diffusion radius is not less than 0.3m.

[0022] As a further improvement, in S5, the excavation of the cut-and-cover tunnel includes the following steps:

[0023] (1) Excavate the upper step in one section, advance 0.5m in a cycle, and construct initial support, set up intermediate partition wall and intermediate partition plate, and grout behind the initial support at the same time;

[0024] (2) The lower step is excavated in two parts, with a cycle advance of 0.5m, lagging behind the upper step by 3m. Initial support is constructed and a middle partition wall is set up. At the same time, grouting is carried out behind the initial support.

[0025] (3) The upper step is excavated in three parts, with a cycle advance of 0.5m, lagging behind the lower step in two parts by 3m. Initial support is installed and a middle diaphragm is set up. At the same time, grouting is carried out behind the initial support.

[0026] (4) The lower step is excavated in four sections, with a cyclic advance of 0.5m, lagging behind the upper step in three sections by 3m, and initial support is carried out. At the same time, grouting is carried out behind the initial support.

[0027] As a further improvement, in S7, the waterproofing layer construction includes the following steps: cleaning and substrate treatment, laying of non-woven fabric buffer layer and plastic waterproofing membrane, construction of fine stone concrete protective layer, construction joint waterproofing, special area waterproofing and grouting system construction.

[0028] The secondary lining construction includes the following steps: steel bar fabrication and installation, formwork and support system construction, scaffolding erection, and secondary lining concrete pouring.

[0029] The present invention also provides a tunnel for subway entrances and exits, using the above-mentioned construction technology for tunnels for subway entrances and exits.

[0030] The beneficial effects of the above-described technical solution of the present invention are as follows:

[0031] 1. This invention effectively lowers the groundwater level by setting up dewatering wells, improves the stability of the soil around the tunnel, reduces safety risks during construction, reduces the water content of the soil within the excavation area, and facilitates construction operations within the tunnel; the well pipe is equipped with a filter pipe and filler material to improve the filtration effect and reduce clogging.

[0032] 2. This invention reinforces the soil around the pipeline by grouting, thus avoiding damage to the surrounding pipeline during construction, minimizing potential risks during construction, and preventing delays in construction progress.

[0033] 3. The waterproof structure of the present invention is mainly based on the self-waterproofing of the secondary lining concrete, combined with a fully enclosed waterproof layer and backfill grouting behind the secondary lining. In special areas where waterstops cannot be installed, a double layer of water-swellable waterproof sealant plus grouting pipes are used for waterproofing treatment, which improves the waterproofing effect of the waterproof structure.

[0034] 4. In this invention, the No. 1, No. 2, No. 3 and No. 4 openings of the tunnel are demolished in the order of upper left, lower left, upper right and lower right, and temporary supports are set up to improve the stability of the tunnel structure. Attached Figure Description

[0035] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent upon reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of the invention are illustrated by way of example and not limitation, and like or corresponding reference numerals denote like or corresponding parts, wherein:

[0036] Figure 1 This is a cross-sectional view of the underground tunnel used in the construction process of the underground tunnel at the subway entrance / exit of this invention.

[0037] Figure 2 This is a longitudinal section view of the underground tunnel in the construction process of the underground tunnel at the subway entrance of the present invention.

[0038] Figure 3 This is a schematic diagram of the guide pipe structure for the construction process of the underground tunnel at the subway entrance / exit of the present invention.

[0039] Figure 4 for Figure 3 Section II;

[0040] Figure 5 This is a flowchart illustrating the long pipe roof construction process of the underground tunnel construction technology for subway entrances and exits according to the present invention.

[0041] Figure 6 This is a cross-sectional view of the full-section grouting process for the construction technology of the underground tunnel at the subway entrance of the present invention.

[0042] Figure 7 This is a plan view of the grouting borehole for full-section grouting in the construction process of the underground tunnel at the subway entrance of this invention.

[0043] Figure 8 This is a process flow diagram of the advanced small guide pipe in the construction technology of the underground tunnel at the subway entrance of the present invention;

[0044] Figure 9 This is a schematic diagram of the advanced small guide pipe structure of the underground tunnel construction process for subway entrances and exits according to the present invention;

[0045] Figure 10 This is a schematic diagram of the structure of the horse-head gate in the underground tunnel construction process of the subway station entrance and exit of the present invention.

[0046] Figure 11 This is a step-by-step diagram of the excavation construction process for the underground tunnel at the subway entrance of the present invention.

[0047] Figure 12 This is a schematic diagram of the steel arch frame used for the initial support of the underground tunnel construction process at the subway entrance of this invention.

[0048] Figure 13 This is a schematic diagram of the cross-sectional waterproof structure of the underground tunnel construction process for subway entrances and exits according to the present invention.

[0049] Figure 14 This is a diagram showing the laying of the buffer layer in the construction process of the underground tunnel at the subway entrance of the present invention.

[0050] Figure 15 This is a diagram showing the laying of the waterproof membrane in the construction process of the underground tunnel at the subway entrance of this invention.

[0051] Figure 16 This is a schematic diagram of the circumferential construction joint structure in the underground tunnel construction process for subway station entrances and exits according to the present invention.

[0052] Explanation of reference numerals in the attached figures:

[0053] 1. Excavated tunnel; 2. Civil defense reserved connection port; 3. Long pipe shed; 4. Advanced small guide pipe; 5. Waterproof layer; 51. Waterproof membrane; 52. Gasket; 53. Cement nail; 54. Buffer layer; 6. Steel mesh; 7. Guide pipe; 8. Excavation outline; 9. Grouting pipe; 10. Tunnel No. 1; 11. Tunnel No. 2; 12. Tunnel No. 3; 13. Tunnel No. 4; 14. Upper step one; 15. Lower step two; 16. Upper step three; 17. Lower step four; 18. Steel arch frame; 19. Central diaphragm; 20. Central diaphragm wall. Detailed Implementation

[0054] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Those skilled in the art should understand that the embodiments described below are only some, not all, of the embodiments disclosed. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0055] Various non-limiting embodiments of the present invention are described in detail below. Any number of elements in the accompanying drawings is for illustrative purposes only and not for limitation, and any naming is for distinction only and has no limiting meaning.

[0056] The principles and spirit of the present invention will be explained in detail below with reference to several representative embodiments.

[0057] Example 1 of the underground tunnel construction process for subway station entrances and exits provided by this invention:

[0058] like Figures 1-16 As shown, it includes the following steps:

[0059] S1, Dewatering well construction: Dewatering wells are set on both sides of the tunnel 1 to lower the groundwater level and increase the stability of the soil around the tunnel 1.

[0060] The construction process of dewatering wells includes drilling, hole completion, casing installation, backfilling with gravel and mud to seal the hole, and well washing.

[0061] In this embodiment, 12 dewatering wells are installed, with a depth of 23.2m and a maximum spacing of 9m. They are arranged 2m apart on both sides of the tunnel 1, with 6 wells on each side (local adjustments can be made if obstacles or areas where construction is not possible are encountered). These dewatering wells lower the groundwater level to 1.0m below the bottom of the tunnel 1.

[0062] The well casing for dewatering is made of welded steel pipe, with a diameter of φ273mm, a wall thickness of 3mm, and an aperture of 600mm. A filter pipe, using a bridge-type design, is installed inside the casing to reduce clogging. The diameter of the filter pipe should be the same as the diameter of the well casing. Two layers of 80-100 mesh nylon mesh are wrapped around the outside of the filter pipe as a filtration layer, with an overlap length of 20%-50% of the single width of the nylon mesh (in practice, a test well is first run with 80 mesh nylon mesh to check the water output and sand content, and adjustments can be made as needed). 18# iron wire is used for spiral winding at 100mm. A 1m long sedimentation pipe is installed at the bottom of the bridge-type filter pipe to prevent sand from clogging the well and affecting water intake; the bottom of the sedimentation pipe is sealed with an iron plate.

[0063] S2, Grouting reinforcement of the soil around the pipeline: Before the underground excavation, drilling and grouting are carried out around the pipeline to improve the overall mechanical properties of the soil around the pipeline.

[0064] In this embodiment, soil reinforcement is carried out by grouting within a 2m radius before and after the pipeline along the direction of the underground tunnel 1, a 2m radius above and below the pipeline, and a 2m radius outside the excavation outline 8. The grouting is done by grouting with A48mm sleeve valve pipes at 1×1m intervals in a quincunx pattern. The grouting slurry is 42.5 grade ordinary silicate cement slurry with a water-cement ratio of 1:1. The slurry pressure is controlled at 0.2-0.3MPa. The grouting pressure is gradually increased during the grouting process until the design grouting pressure is reached and grouting continues for more than 30 minutes.

[0065] S3, construction of long pipe shed 3 and full-section grouting: several long pipe sheds 3 are used as advance support for the arch of the tunnel 1. The long pipe sheds 3 are arranged in an arch shape. Grouting is carried out to reinforce the soil within 2m outside the excavation outline 8 of the tunnel 1. Then, double rows of advance small pipes 4 are set above the long pipe sheds 3 to ensure the stability of the excavation face.

[0066] The construction process of the long pipe shed 3 includes: constructing guide walls, drilling, jacking in the long pipe shed 3, cleaning the holes, and grouting.

[0067] In this embodiment, the tunnel section is 55m long, and the arch is equipped with a single row of 32 long pipe sheds with diameters of 108mm and 6mm, totaling 54m in length, with a circumferential spacing of 400mm and an external insertion angle of 0.5°.

[0068] like Figure 3 and Figure 4 As shown, in order to ensure the precise advancement of the long pipe shed 3, a guide pipe 7 is installed in the hole after drilling to improve the installation accuracy.

[0069] Because the long pipe shed 3 is relatively long and difficult to control the accuracy, in this embodiment, the long pipe shed 3 is divided into two sections and installed separately. Each section is 30m long and the overlap length should be no less than 3m.

[0070] Full-section grouting, such as Figure 6 and Figure 7 As shown, grouting reinforcement is carried out on the soil within 2m outside the excavation outline 8 of the tunnel 1. The opening diameter of the grouting holes is not less than 108mm, and the final diameter is not less than 90mm. The pipes at the borehole openings are Φ108mm hot-rolled seamless steel pipes with a wall thickness of 5mm and a length of 3m. The grouting holes are spaced 1.4m apart at the bottom, and within each ring, the grouting holes are spaced approximately 0.7m apart along the axis of that ring. Each grouting cycle is 15m long, with 12m of excavation and a 3m retaining of a grout-stopping rock mass. The drilling and grouting sequence proceeds from the outside to the inside, with holes in the same ring being constructed at intervals.

[0071] Before the demolition of the horse-head gate, to ensure construction safety, a double row of advanced small guide pipes (4) were installed above the large pipe shed (reference). Figure 2 and Figure 9 The advanced small guide pipe 4 is installed in double rows within 180° of the arch excavation area, excluding the entrance position. Each guide pipe is 4m long, circumferentially spaced 300mm apart, with an external insertion angle of 5-10°. Grouting holes are formed by staggered drilling every 150mm along the pipe wall, with a hole diameter of 6mm. The grouting slurry is 42.5 ordinary silicate cement slurry, with a water-cement ratio of 1:1 (by weight). The grouting pressure is 0.5-1.0MPa, and the grouting diffusion radius is not less than 0.3m.

[0072] Within a 180° range of the arch section, except at the entrance position, double rows of advance small guide pipes 4 are installed. The advance small guide pipes 4 are 4m long, with a circumferential spacing of 300mm and an external insertion angle of 5-10°. Grouting holes are formed by staggered drilling every 150mm on the pipe wall. The hole diameter is 6mm and the grouting diffusion radius is not less than 0.3m.

[0073] S4. Demolition of the horse-head gate: Following the order of upper left, lower left, upper right, and lower right, demolish the No. 10, No. 2, No. 11, No. 3, No. 12, and No. 4, No. 13 openings of the horse-head gate in sequence, and erect temporary horizontal and vertical supports. The specific steps include:

[0074] (1) Begin the circumferential demolition of the retaining wall and shotcrete surface at the No. 1 tunnel 10 horse-head gate, leaving the core soil portion undemolished for the time being. After the cleanup is completed, three steel frames are erected closely under the retaining wall, temporary vertical supports are erected in the middle, wire mesh is hung, and shotcrete support is provided; the core soil area is retained, with the reserved core soil area not less than 50% of the excavation area, and the cyclic excavation continues, demolishing the core soil and the retaining wall and shotcrete surface at the temporary invert arch, erecting temporary horizontal supports, so that the No. 1 tunnel is temporarily closed into a ring;

[0075] (2) After the No. 1 tunnel 10 is excavated and temporarily closed into a 3m ring, the retaining wall and shotcrete surface of the No. 2 tunnel 11 horse-head gate area will be demolished. The reserved core soil part will not be demolished for the time being. After the cleaning is completed, three steel frames are closely arranged at the horse-head gate, temporary vertical supports are erected in the middle, and connected to the reserved steel frame nodes of the No. 1 tunnel 10, and the whole is closed into a ring, with netting and shotcrete support.

[0076] (3) After the No. 2 tunnel 11 is closed into a 3m ring, the retaining wall and shotcrete surface of the No. 3 tunnel 12 are demolished in a circumferential manner, while the core soil part is not demolished for the time being. After the cleaning is completed, three steel frames are erected closely under the retaining wall and connected to the reserved node of the No. 1 tunnel 10. The netting is hung and shotcrete support is provided; the core soil area is retained and the excavation continues in a cyclic manner, the core soil and the retaining wall and shotcrete surface at the temporary invert arch are demolished, and temporary horizontal bracing is erected to make the No. 3 tunnel temporarily closed into a ring.

[0077] (4) After the No. 3 tunnel 12 is excavated and temporarily closed into a 3m ring, the retaining wall and shotcrete surface of the No. 4 tunnel 13 horse head gate area will be demolished.

[0078] Tunnel No. 4, No. 13, was excavated in its entirety. Three steel frames were densely arranged at the entrance and connected to the reserved steel frame nodes of Tunnel No. 2 and No. 3, forming a closed loop.

[0079] S5, Excavation of the cut-and-cover tunnel 1, using the CRD method for excavation of the cut-and-cover tunnel 1; such as Figure 11 As shown, the upper step 14, the lower step 2 15, the upper step 3 16 and the lower step 4 17 are excavated in sequence, and initial support is carried out in a timely manner, and the middle partition wall 20 and the middle partition plate 19 are set up.

[0080] In S5, the excavation of the cut-and-cover tunnel 1 includes the following steps:

[0081] (1) Excavate part 14 of the upper step, advance 0.5m in a cycle, and carry out initial support, set up middle partition wall 20 and middle partition plate 19, and grout behind the initial support at the same time;

[0082] (2) The second section of the lower step is excavated at 15 meters, with a cycle advance of 0.5 meters, lagging behind the first section of the upper step at 143 meters. Initial support is constructed, and a middle partition wall 20 is set up. At the same time, grouting is carried out behind the initial support.

[0083] (3) The upper step of the third section 16 is excavated, with a cycle advance of 0.5m, lagging behind the lower step of the second section 153m. Initial support is constructed and a middle diaphragm 19 is installed. At the same time, grouting is carried out behind the initial support.

[0084] (4) The fourth section of the lower step is excavated at 17 meters, with a cyclic advance of 0.5 meters, lagging behind the third section of the upper step by 3 meters. Initial support is then implemented, and grouting is performed behind the initial support.

[0085] In addition, the tunnel is equipped with a reserved connection point for civil defense purposes, in order to deal with emergencies.

[0086] S6, Initial support construction: Prepare steel arch frame 18 and steel mesh 6. First, install steel arch frame 18, then weld steel mesh 6 to steel arch frame 18. After welding steel mesh 6, spray concrete in the order of arch foot first and arch top. After the concrete solidifies, cure the concrete for no less than 14 days. Finally, perform grouting operation behind the initial support.

[0087] S7, Waterproof layer 5 and secondary lining construction: Intermittently remove the central partition wall 20, lay the waterproof layer 5 and pour the bottom secondary lining. The waterproof layer 5 includes a buffer layer 54 and a waterproof board 51. The waterproof layer 5 is a non-woven fabric buffer layer and an ECB waterproof board. The thickness of the ECB waterproof board is not less than 2.0mm. The non-woven fabric buffer layer uses 400g / m² short-fiber non-woven fabric. Then, remove the central partition wall 19 and intermittently remove the central partition wall 20, lay the waterproof layer 5, and pour the upper secondary lining.

[0088] In S7, the construction of waterproof layer 5 includes the following steps: cleaning and base surface treatment, laying of non-woven fabric buffer layer and plastic waterproof board, construction of fine stone concrete protective layer, construction joint waterproofing, special part waterproofing and grouting system construction.

[0089] 1. Cleaning and surface preparation:

[0090] (1) The bottom should be cleaned by a combination of manual labor and machinery. During the cleaning process, care should be taken to protect the initial support of the channel.

[0091] (2) There should be no open water flow on the base surface where the waterproof board 51 is laid.

[0092] (3) The base surface for laying the waterproof membrane 51 should be flat. Before laying the waterproof membrane 51, the base surface should be leveled. The treatment method can be sprayed concrete or 1:2.5 cement mortar. The treated base surface should meet the following conditions: the base surface should be flat, clean, free from looseness, hollowness, and cracks. Its flatness should meet the requirement that D / L≤1 / 10, where D--the maximum depth of the concavity between two adjacent convex surfaces; L--the shortest distance between two adjacent convex surfaces.

[0093] (4) The base surface shall not have any sharp burrs. In particular, large sharp stones and other hard objects often appear on the surface of shotcrete. They should be removed cleanly or covered with 1:2.5 cement mortar to avoid puncturing the waterproof membrane 51 when pouring concrete.

[0094] (5) Metal components that protrude from the base layer, such as steel bar ends, anchor bolt ends, steel pipe ends, etc., should be cut off and smoothed with mortar. Metal components that cannot be cut off must be covered with shotcrete or mortar, and their arc radius R is greater than 200mm.

[0095] (6) The base surface within 50cm on both sides of the expansion joint shall be leveled with 1:2.5 waterproof cement mortar for the whole section, and its flatness shall meet the requirements for the installation of the back-attached waterstop.

[0096] 2. Laying of buffer layer 54 and waterproof membrane 51:

[0097] The waterproof membrane 51 is laid using a nail-free installation process, such as... Figure 15 As shown, the welding adopts hot-melt double-seam welding (hand welding can also be used for some details). The overlap width of the waterproof membrane 51 is 100mm, and the weld width is 15mm for each strip. When laying the waterproof layer 5, it is laid in two rings, one for the invert arch and one for the arch wall. The waterproof membrane 51 of the bottom plate is laid 500mm higher than the bottom plate reinforcement and 500mm longer in the longitudinal direction to facilitate the overlap with the arch wall and the next cycle. The waterproof layer 5 is laid along the circumferential direction.

[0098] (1) Laying a buffer layer 54

[0099] like Figure 14 As shown, a buffer layer 54 should be laid before laying the waterproof membrane 51. The buffer layer 54 is then fixed to the base surface using cement nails 53 (or expansion bolts) and plastic round washers 52 that mate with the waterproof membrane 51. During fixing, the nail heads must not protrude beyond the plane of the washers 52. The fixing points are arranged in a staggered pattern. The fixing spacing on the side walls is 80–100 cm; the fixing spacing on the top arch is 50–80 cm; the fixing spacing on the inverted arch is 1.5–2 m; and the fixing spacing at the connection between the base plate and the side walls should be appropriately increased to 50 cm. Round washers 52 should be added to recessed areas of the base surface to prevent the waterproof membrane 51 from being suspended in the recesses. The plastic round washers 52 have a recessed hole in the middle to prevent nails from protruding beyond the plane of the round washers 52, thus avoiding puncturing the waterproof layer 5.

[0100] The buffer layer 54 is connected by the lapping method with a lapping width of 50 mm. The lap joint can be welded by the dot bonding method or fixed with the plastic gasket 52. When laying the buffer layer 54, it should be closely attached to the base surface without being pulled too tightly or showing large bulges, so as not to affect the laying of the waterproof board 51.

[0101] (2)Laying the waterproof board 51

[0102] 1) When laying the waterproof board 51, the laying direction of the waterproof board 51 should be mainly based on minimizing the manual welds and no cross welds (i.e., no overlapping parts of four layers of materials) should appear. The waterproof board 51 on the arch wall and invert is preferably laid longitudinally along the mined tunnel 1. The specific laying direction should be determined according to the structural form.

[0103] 2) The waterproof board 51 is manually welded to the plastic round gasket 52 with a hot air welding gun. The welding should be firm and reliable to avoid the detachment of the waterproof board 51 during the pouring and vibration of the concrete. When welding, it is strictly prohibited to weld through the waterproof board 51.

[0104] 3) When fixing the waterproof board 51, it should be noted that it should not be pulled too tightly or show large bulges. The laid waterproof board 51 should be consistent with the unevenness of the base surface, being natural, flat and adherent, so as not to affect the size of the concrete pouring of the secondary lining or cause the waterproof board 51 to separate from the round gasket 52.

[0105] 4) The joints between the waterproof boards 51 are hot-melt welded with double welds. The lapping width is 10 cm. After welding, an airtightness test is carried out by inflating. The inflation pressure is 0.25 Mpa (2.5 Rar). Observe for 15 minutes. If the pressure drop value is less than 10%, it is qualified. If the pressure drop is too large and does not meet the requirements, the leakage point should be found in time and repaired.

[0106] 5) At the longitudinal lap and circumferential lap of the waterproof board 51, in addition to normal construction, another layer of the same type of waterproof board 51 material is covered and welded by the hot-melt welding method. When circumferentially lapping, the lower waterproof board 51 should press the upper waterproof board 51. When welding multiple layers of waterproof boards 51, the welds at the lapping parts must be staggered, and there should be no overlapping of more than three layers of joints.

[0107] 6) After the waterproof board 51 is laid, a comprehensive inspection should be carried out on its surface. When finding damaged parts, they should be repaired by welding in time. The patch should be cut into a round corner. The distance between the edge of the patch and the damaged edge should not be less than 7 cm. The patch should be fully welded, and the weld seam should be strengthened with a plastic welding rod without any upturned edges or bulging parts.

[0108] 7) All the laps of the waterproof board 51 should exceed the reserved lapping reinforcement by at least 40 cm, or the lap can be rolled up and fixed. If the lap is too short, it will cause the later joint operation to be impossible.

[0109] 3. Waterproofing of construction joints

[0110] For the excavated tunnel 1, the expansion joint uses a centrally shaped steel-edged rubber waterstop, the circumferential construction joint uses a flat-webbed steel-edged rubber waterstop, and the horizontal construction joint uses a galvanized steel plate waterstop. Reusable grouting pipes (9) are pre-embedded in the construction joints. The location of settlement joints must ensure that the arch, sidewalls, and invert are continuous at the same mileage.

[0111] (1) Waterproofing construction of circumferential construction joints

[0112] 1) such as Figure 16 As shown, the waterstop is positioned at half the thickness of the lining, with the width embedded in the concrete and the exposed portion being half the width of the waterstop. Every 50cm along the lining ring, a φ12mm rebar hole is drilled in the end formwork. Precast rebar clips are passed through the end formwork, with half of the waterstop tightly secured inside, and the other half resting flat against the end plate and fixed with tie wire. After the concrete has hardened, the end plate is removed, the waterstop is straightened, and then the rebar is bent and secured to the waterstop before pouring the next cycle of concrete.

[0113] 2) When pouring the secondary lining concrete, strengthen the concrete vibration to remove air bubbles and voids at the bottom of the waterstop, so that the waterstop and concrete are tightly bonded.

[0114] 3) Before pouring concrete into the circumferential construction joint, its surface must be roughened and cleaned.

[0115] (2) Waterproofing construction of longitudinal construction joints

[0116] 1) The width of the galvanized steel waterstop is 30cm and the thickness is 3mm. It is made of Q235b steel plate and hot-dip galvanized, with a zinc coating thickness of not less than 30 microns.

[0117] 2) Installation of steel plate waterstops: The waterstops are fixed to the structural steel bars using wire or welding at 40cm intervals. The fixing must be firm and reliable to prevent the fixing points from falling off during concrete pouring and vibration, which could cause the waterstops to collapse or twist and affect their water-stopping effect. The waterstops should be accurately positioned and firmly fixed. In particular, the formwork sealing plates should be firmly fixed to prevent bulging of the formwork from affecting the positioning accuracy of the waterstops.

[0118] 3) Connection of steel plate waterstops: The connection of steel plate waterstops in the same direction adopts full-width butt welding and lap full welding connection, with an lap width of not less than 50mm. The connection of intersecting steel plate waterstops adopts full welding full-width lap connection.

[0119] 4) Roughening, debris removal, and surface treatment of construction joints: Before pouring concrete at horizontal construction joints, the surface laitance and debris must be removed, a 2cm layer of cement mortar should be laid first, and then the concrete should be poured. The roughening depth should be no less than 20mm, and the fresh concrete surface must be completely exposed.

[0120] (3) Waterproofing construction of expansion joints

[0121] 1) An external waterstop is installed on the outside of the expansion joint.

[0122] 2) A steel-edged rubber waterstop with a grouting pipe 9 is installed in the middle of the expansion joint (with a central air hole type) to form a closed waterproof line.

[0123] 3) Stainless steel water collection channels are installed on the inner side of the arch and side wall at the expansion joint to guide a small amount of seepage water into the vehicle ditch and discharge it into the wastewater pump room. Polyurethane sealant is embedded on the inner side of the base plate.

[0124] 4. Waterproofing construction for special areas

[0125] (1) Special finishing treatment of waterproof membrane 51

[0126] 1) At the interface of the underground tunnel 1, a cast-in-place ring beam is constructed, and a grouting pipe 9 is pre-embedded between the cast-in-place ring beam and the inner lining of each structure. The end ring protrudes 5-10cm from the wall end, and a water diversion channel is set up for water diversion. A stainless steel interface groove should be set at the junction of the pipe segment and the cast-in-place opening. The surrounding rock outside the interface should be grouted.

[0127] 2) The waterproofing materials of each structure should be self-sealing at the joints.

[0128] (2) For special locations where waterstops cannot be installed, waterproofing should be carried out by using double-layer water-swellable sealant + grouting pipe 9.

[0129] The secondary lining construction includes the following steps: steel bar fabrication and installation, formwork and support system construction, scaffolding erection, and secondary lining concrete pouring.

[0130] S8, secondary lining backfill grouting, grouting is performed on the backfill behind the secondary lining through grouting pipe 9.

[0131] In this embodiment, the grout is prepared using a cement grout with a water-cement ratio of 1:0.5, and 2-3% of a micro-expansion agent is added to the cement grout.

[0132] Before grouting, water should be injected first to detect leaks (and to estimate the amount of grout needed). For larger leaks, quick-drying cement or epoxy resin can be used for surface sealing before directly injecting the grout into the leaking area. The grouting pressure should be controlled below 0.2 MPa.

[0133] Grouting should be carried out after the secondary lining concrete has reached more than 75% of its design strength. Grouting of this hole can be stopped when the grouting pressure reaches the design final pressure or when cross-grouting occurs between adjacent holes. After grouting is stopped, the hole valve should be closed immediately, and then the pipeline should be removed and cleaned. After the grout has initially set, the hole valve should be removed again, and the grouting hole should be filled and compacted with cement mortar.

[0134] The present invention also provides a tunnel for subway entrances and exits, using the above-mentioned construction technology for tunnels for subway entrances and exits.

[0135] While various embodiments of the invention have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Many modifications, alterations, and alternatives will occur to those skilled in the art without departing from the spirit and essence of the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in the practice of the invention. The appended claims are intended to define the scope of the invention and therefore cover any modular compositions, equivalents, or alternatives within the scope of these claims.

Claims

1. A construction technique for a tunnel entrance / exit of a subway station, characterized in that, Includes the following steps: S1, Dewatering well construction: Dewatering wells are set on both sides of the tunnel (1) to lower the groundwater level and increase the stability of the soil around the tunnel (1); S2, Grouting reinforcement of the soil around the pipeline: Before the underground excavation, drilling and grouting are carried out around the pipeline to improve the overall mechanical properties of the soil around the pipeline. For the pipeline within 2m before and after the tunnel (1), 2m above and below, and 2m outside the excavation outline (8), the soil is reinforced by grouting with sleeve valve pipes. The spacing is 1×1m, arranged in a quincunx pattern. The grouting slurry is silicate cement slurry with a water-cement ratio of 1:1 and a slurry pressure of 0.2~0.3MPa. S3, Long pipe shed (3) construction and full-section grouting, the arch of the tunnel (1) is supported by several long pipe sheds (3), which are arranged in an arch shape; the soil within 2m outside the excavation outline (8) of the tunnel (1) is reinforced by grouting, and then double rows of small pipes (4) are set above the long pipe sheds (3) to ensure the stability of the excavation face; S4, the demolition of the horse-head gate is carried out in the order of upper left, lower left, upper right and lower right. The first hole (10), the second hole (11), the third hole (12) and the fourth hole (13) of the horse-head gate are demolished in sequence, and temporary horizontal and vertical supports are erected. S5, excavation of the tunnel (1) using the CRD method; excavation of the upper bench section 1 (14), lower bench section 2 (15), upper bench section 3 (16) and lower bench section 4 (17) in sequence, and initial support, middle partition wall (20) and middle partition plate (19) are installed. S6, initial support construction, prepare steel arch frame (18) and steel mesh (6), first install steel arch frame (18), then weld steel mesh (6) to steel arch frame (18), after welding steel mesh (6), concrete spraying is carried out in the order of arch foot first and arch top, after the concrete solidifies, the concrete is cured, the curing time is not less than 14 days, and finally the initial support back grouting operation is carried out. S7, Waterproof layer (5) and secondary lining construction, the middle partition wall (20) is removed intermittently, the waterproof layer (5) is laid and the bottom secondary lining is poured. The waterproof layer (5) includes a non-woven buffer layer (54) and a plastic waterproof board (51). The construction of the waterproof layer (5) includes cleaning and base treatment, laying of non-woven buffer layer and plastic waterproof board, construction of fine stone concrete protective layer, construction joint waterproofing, special part waterproofing and grouting system construction. The special part adopts the waterproofing method of double water-swellable sealant plus grouting pipe. Then the middle partition wall (19) is removed and the middle partition wall (20) is removed intermittently, the waterproof layer (5) is laid and the upper secondary lining is poured. Secondary lining construction includes steel reinforcement fabrication and installation, formwork and support system construction, scaffolding erection, and secondary lining concrete pouring. S8, secondary lining backfill grouting, grouting is performed on the backfill behind the secondary lining through grouting pipe (9). The secondary lining backfill grouting uses cement grout with a water-cement ratio of 1:0.5, with 2~3% micro-expansion agent added, and the grouting pressure is controlled within 0.2MPa.

2. The construction method for the underground tunnel at the entrance / exit of a subway station according to claim 1, characterized in that: In S1, the construction process of the dewatering well includes drilling, hole completion, casing installation, filling with gravel and mud to seal the hole, and well washing. The well casing is equipped with a water filter pipe, and the outside of the water filter pipe is wrapped with two layers of 80-100 mesh nylon mesh as a filter layer. A sedimentation pipe is also provided below the water filter pipe.

3. The construction method for the underground tunnel at subway entrances and exits according to claim 1, characterized in that: In S3, the construction process of the long pipe shed (3) includes: building a guide wall, drilling, jacking the long pipe shed (3), cleaning the hole and grouting. The long pipe shed (3) has a circumferential spacing of 400mm and an external insertion angle of 0.5°. When installing, the long pipe shed (3) is installed in two sections, and the overlap length of the two sections of the long pipe shed (3) is not less than 10% of the length of each section of the long pipe shed (3). Within a 180° range of the arch section, except for the entrance position, double rows of advanced small guide pipes (4) are set. The advanced small guide pipes (4) are 4m long, with a circumferential spacing of 300mm and an external insertion angle of 5-10°. The pipe wall is staggered every 150mm to form grouting holes with a hole diameter of 6mm and a grouting diffusion radius of not less than 0.3m.

4. The construction method for the underground tunnel at the entrance / exit of a subway station according to claim 1, characterized in that: In S5, the excavation of the cut-and-cover tunnel (1) includes the following steps: (1) Excavate the upper step (14), advance 0.5m in a cycle, and carry out initial support, set up the middle partition wall (20) and the middle partition plate (19), and grout behind the initial support at the same time; (2) The second step of the lower step (15) is excavated, with a cyclic advance of 0.5m, lagging behind the first step of the upper step (14) by 3m. Initial support is constructed and a middle partition wall (20) is set up. At the same time, grouting is carried out behind the initial support. (3) The upper step three sections (16) are excavated, with a cyclic advance of 0.5m, lagging behind the lower step two sections (15) by 3m. Initial support is installed and a middle partition (19) is set up. At the same time, grouting is carried out behind the initial support. (4) The fourth step of the lower step (17) is excavated, with a cyclic advance of 0.5m, lagging behind the third step of the upper step by 3m, and initial support is carried out. At the same time, grouting is carried out behind the initial support.

5. A tunnel structure for a subway station entrance / exit, characterized in that: The construction process of the underground tunnel at the entrance and exit of the subway station as described in any one of claims 1-4 shall be adopted.

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