Subway station entrance and exit underground excavation channel structure and construction technology

Abstract

The invention provides a metro station entrance and exit underground excavation channel structure and a construction technology, and belongs to the technical field of metro construction.The construction technology comprises the steps that S1, precipitation well construction is conducted, specifically, precipitation wells are arranged on the two sides of an underground excavation channel so as to lower the underground water level, and the stability of soil around the underground excavation channel is improved; s2, grouting reinforcement is conducted on soil around the pipeline, and before underground excavation construction, drilling and grouting are conducted on the periphery of the pipeline so that the overall mechanical property of the soil around the pipeline can be improved; according to the method, the soil body around the pipeline is subjected to grouting reinforcement, damage to the surrounding pipeline in the construction process is avoided, risks possibly generated in the construction process are reduced to the maximum extent, and then the construction progress is prevented from being delayed. According to the waterproof structure, secondary lining concrete self-waterproofing is mainly adopted, the totally-closed waterproof layer and secondary lining back backfilling grouting are combined, waterproof treatment is carried out on the special portion where the water stop belt cannot be arranged in the mode that double water-swelling water stop glue is injected into the grouting pipe, and the waterproof effect of the waterproof structure is improved.

Description

Technical Field

[0001] The invention relates to the technical field of subway construction, and in particular to a dark-dig passage structure and a construction process for a subway station entrance and exit. Background Art

[0002] The underground excavation method for subway construction refers to a subway construction method that does not dig up the ground under certain conditions, but excavates and builds the lining structure entirely underground. Since subway stations are usually built in the central area of ​​the city, the surrounding environment is very complex, with a large number of underground pipelines, above-ground (underground) buildings (structures) and busy ground traffic, in many cases it is impossible to use the open excavation method or the covered excavation method to build the subway. At this time, the underground excavation method for subway construction has become almost the only option.

[0003] When digging a subway tunnel in a certain urban area in the country, the following problems were encountered:

[0004] 1. The main pipelines above the subway entrance and exit are sewage pipes, water pipes, heat pipes and power pipes. Among them, the deepest buried depth of the sewage pipe is only 2m away from the primary branch, which is easy to cause damage to surrounding pipelines. In addition, due to the existence of sewage pipes, water pipes and other pipelines, it is easier to encounter problems such as water leakage during the construction process.

[0005] 2. The underground excavation section is mainly located in the silty clay and clayey silt layers, which may easily lead to face collapse during construction.

[0006] 3. Before the construction of the dark excavation section, the retaining wall at the position of the horse head gate should be chiseled out first to convert the force system. During the chiseling process, it is difficult to break the tunnel door and the construction risk is relatively high. Summary of the invention

[0007] The invention provides a dark-dig passage structure and a construction process for an entrance and exit of a subway station, so as to solve the technical problems in the prior art.

[0008] In order to solve the above problems, the underground tunnel construction process provided by the present invention adopts the following technical solution, including the following steps:

[0009] S1, construction of drainage wells: setting up drainage wells on both sides of the underground tunnel to lower the groundwater level and increase the stability of the soil around the underground tunnel;

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

[0011] S3, long pipe shed construction and full-section grouting. Several long pipe sheds are used as advance support for the arch of the dark excavation channel. The long pipe sheds are arranged in an arch shape. Grouting reinforcement is carried out on the soil within 2m outside the excavation contour line of the dark excavation channel. After that, double rows of advance small guide tubes are set above the long pipe shed to ensure the stability of the excavation working surface.

[0012] S4, demolition of the horse head gate. In the order of upper left, lower left, upper right and lower right, the No. 1 hole, No. 2 hole, No. 3 hole and No. 4 hole of the horse head gate are demolished in turn, and temporary horizontal braces and temporary vertical braces are set up;

[0013] S5, excavation of dark tunnel, using CRD method to excavate dark tunnel; excavate the first part of upper step, the second part of lower step, the third part of upper step and the fourth part of lower step in sequence, and carry out initial support in time, and set up middle partition wall and middle partition board;

[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 welding the steel mesh, spray concrete in the order of arch foot first and then arch top, after the concrete solidifies, cure the concrete, the curing time is not less than 14 days, and finally carry out grouting behind the initial support;

[0015] S7, waterproof layer and secondary lining construction, remove the middle partition wall at intervals, lay the waterproof layer and pour the bottom secondary lining, the waterproof layer includes a buffer layer and a waterproof board; then remove the middle partition board and the middle partition wall at intervals, lay the waterproof layer, and pour the upper secondary lining;

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

[0017] As a further improvement, in S1, the dewatering well construction process includes drilling a hole, finishing the hole, lowering the well pipe, surrounding the hole with gravel and mud, and washing the well;

[0018] A water filter pipe is arranged in the well pipe, and two layers of 80-100 mesh nylon mesh are wrapped on the outside of the water filter pipe as a filter layer. A sedimentation pipe is also arranged below the water filter pipe.

[0019] As a further improvement, in S2, sleeve valve pipe grouting was used to reinforce the soil 2m front and back, 2m up and down along the direction of the underground excavation channel, and 2m outside the excavation contour line. The spacing was 1×1m and the arrangement was in a plum blossom shape. The grouting slurry used was 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 long pipe shed construction process includes: building a guide wall, drilling, jacking the long pipe shed, cleaning the hole and grouting, the long pipe shed has a circumferential spacing of 400 mm and an external insertion angle of 0.5°; when being installed, the long pipe shed is divided into two sections and installed separately, and the overlapping length of the two sections of the long pipe shed is not less than 10% of the length of each section of the long pipe shed;

[0021] In addition to the entrance position, double rows of advance small ducts are set within the 180° range of the arch excavation. The advance small ducts are 4m long, with an annular spacing of 300mm and an external insertion angle of 5 to 10°. Grouting holes are formed by staggered drilling every 150mm on the pipe wall. The diameter of the holes is 6mm and the grouting diffusion radius is not less than 0.3m.

[0022] As a further improvement, in S5, the dark tunnel excavation includes the following steps:

[0023] (1) Excavate the upper step, with a cycle advance of 0.5m, and carry out initial support, set up middle partitions and temporary middle partitions, and grouting behind the initial support;

[0024] (2) Excavation of the lower step part 2, with a cycle advance of 0.5m, lagging behind the upper step part 1 by 3m, and initial support, middle partition wall and grouting behind the initial support;

[0025] (3) Excavation of the third part of the upper step, with a cycle advance of 0.5m, lagging 3m behind the second part of the lower step, and initial support, temporary partition board, and grouting behind the initial support;

[0026] (4) The fourth part of the lower step is excavated with a cycle advance of 0.5m, lagging behind the third part of the lower step by 3m, and initial support is applied, while grouting is carried out behind the initial support.

[0027] As a further improvement, in S7, the waterproof layer construction includes the following steps: bottom cleaning and base surface treatment, non-woven fabric buffer layer and plastic waterproof board laying, fine stone concrete protective layer construction, construction joint waterproofing construction, special part waterproofing construction and grouting system construction;

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

[0029] The present invention also provides a dark-cut passage at an entrance and exit of a subway station, which adopts the above-mentioned dark-cut passage construction process at the entrance and exit of the subway station.

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

[0031] 1. The present invention effectively lowers the groundwater level by setting up precipitation wells, improves the stability of the soil around the dark excavation channel, reduces the safety risks during the construction process, reduces the water content of the soil within the excavation range, and facilitates construction operations in the channel; a water filter pipe and surrounding filter material are provided in the well pipe to improve the filtering effect and reduce clogging.

[0032] 2. The present invention avoids damage to surrounding pipelines during the construction process by grouting the soil around the pipeline, thereby minimizing the risks that may arise during the construction process and avoiding delays in the construction progress.

[0033] 3. The waterproof structure of the present invention mainly uses the self-waterproofing of the second lining concrete, combined with a fully enclosed waterproof layer and backfill grouting behind the second lining, and uses a double-channel water-swelling water-stop glue plus a grouting pipe to perform waterproofing treatment in special locations where waterstop strips cannot be set, thereby improving the waterproof effect of the waterproof structure.

[0034] 4. The horse head gate of the present invention breaks down the No. 1 hole, No. 2 hole, No. 3 hole and No. 4 hole of the horse head gate in the order of upper left, lower left, upper right and lower right, and sets temporary support to improve the stability of the tunnel structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] By reading the following detailed description with reference to the accompanying drawings, the above and other objects, features and advantages of the exemplary embodiments of the present invention will become readily understood. In the accompanying drawings, several embodiments of the present invention are shown in an exemplary and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0036] Figure 1 It is a cross-sectional view of a dark excavation tunnel of a subway station entrance and exit dark excavation tunnel construction process of the present invention;

[0037] Figure 2 A longitudinal section diagram of a dark-digging tunnel of a subway station entrance and exit dark-digging tunnel construction process of the present invention;

[0038] Figure 3 It is a schematic diagram of the guide pipe structure of the underground tunnel construction process of the subway station entrance and exit of the present invention;

[0039] Figure 4 for Figure 3 II section view;

[0040] Figure 5 It is a long pipe shed construction process flow chart of the underground tunnel construction process for the subway station entrance and exit of the present invention;

[0041] Figure 6 It is a cross-sectional view of the full-section grouting of the underground tunnel construction process for the subway station entrance and exit of the present invention;

[0042] Figure 7 It is a plan view of the grouting drilling holes for full-section grouting in the construction process of the underground tunnel at the entrance and exit of the subway station of the present invention;

[0043] Figure 8 It is a process flow chart of the advanced small conduit for the construction process of the underground tunnel at the entrance and exit of the subway station of the present invention;

[0044] Fig. 9 It is a structural schematic diagram of the advanced small guide tube of the underground tunnel construction process of the subway station entrance and exit of the present invention;

[0045] Fig.10 It is a structural schematic diagram of a horse head door of a construction process for a dark excavation passage at an entrance and exit of a subway station according to the present invention;

[0046] Fig.11 It is a construction step diagram of the dark excavation passage of the dark excavation passage construction process of the subway station entrance and exit of the present invention;

[0047] Fig.12 It is a structural schematic diagram of a steel arch frame for initial support of a construction process for a dark excavation passage at an entrance and exit of a subway station according to the present invention;

[0048] Fig.13 It is a schematic diagram of the cross-sectional waterproof structure of the construction process of the underground tunnel at the entrance and exit of the subway station of the present invention;

[0049] Fig.14 It is a laying diagram of the buffer layer of the underground tunnel construction process for the entrance and exit of the subway station of the present invention;

[0050] Fig.15 It is a laying diagram of the waterproof board of the construction process of the underground tunnel at the entrance and exit of the subway station of the present invention;

[0051] Fig.16 It is a schematic diagram of the circumferential construction joint structure of the underground station entrance and exit dark excavation passage construction process of the present invention.

[0052] Description of reference numerals:

[0053] 1. Underground excavation passage; 2. Reserved connection port for civil air defense; 3. Long pipe shed; 4. Advance small duct; 5. Waterproof layer; 51. Waterproof board; 52. Gasket; 53. Cement nail; 54. Buffer layer; 6. Steel mesh; 7. Guide pipe; 8. Excavation contour line; 9. Grouting pipe; 10. Hole No. 1; 11. Hole No. 2; 12. Hole No. 3; 13. Hole No. 4; 14. First part of the upper step; 15. Second part of the lower step; 16. Third part of the upper step; 17. Fourth part of the lower step; 18. Steel arch frame; 19. Middle partition; 20. Middle partition wall. DETAILED DESCRIPTION

[0054] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Those skilled in the art should know that the embodiments described below are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0055] Various non-limiting embodiments of the present invention are described in detail below. The number of any element in the drawings is for illustration and not for limitation, and any naming is only for distinction and does not have any limiting meaning.

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

[0057] Example 1 of the construction process for the underground tunnel at the entrance and exit of the subway station provided by the present invention:

[0058] like Figure 1-Figure 16 As shown, the following steps are included:

[0059] S1, construction of dewatering wells: setting up dewatering wells on both sides of the underground tunnel 1 to lower the groundwater level and increase the stability of the soil around the underground tunnel 1;

[0060] The construction process of dewatering wells includes drilling, hole completion, lowering of well pipes, surrounding with gravel and mud to seal the hole and wash the well.

[0061] In this embodiment, there are 12 precipitation wells, with a depth of 23.2m and a maximum spacing of 9m, arranged at 2m on both sides of the dark excavation channel 1, with 6 wells on one side (local adjustments can be made if obstacles or construction sites are not possible). Through the precipitation wells, the groundwater level is lowered to 1.0m below the bottom of the dark excavation channel 1.

[0062] The well pipe of the precipitation well is made of welded steel pipe, the diameter of the well wall pipe is φ273mm, the well wall thickness is 3mm, and the aperture is 600mm. A water filter pipe is set in the well pipe, and the water filter pipe adopts a bridge-type water filter pipe to reduce blockage. The diameter of the water filter pipe should be the same as the diameter of the well wall pipe; the outside of the filter pipe is wrapped with 2 layers of 80-100 mesh nylon mesh as a filter layer, and the nylon mesh overlap length is 20% to 50% of the single width of the nylon mesh (in specific implementation, first use 80 mesh nylon mesh to test one well, check the water output and sand content, and then make adjustments), and use 18# iron wire @100 spiral winding. A sedimentation pipe with a length of 1m is set at the bottom of the bridge-type water filter pipe to prevent the well from being blocked by sand settling and affecting the water inlet; the bottom of the sedimentation pipe is sealed with an iron plate.

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

[0064] In this embodiment, A48mm sleeve valve pipe grouting is used to reinforce the soil within 2m front and back, 2m up and down, and 2m outside the excavation contour line 8 along the dark excavation channel 1, with a spacing of 1×1m and a plum blossom-shaped arrangement. The grouting slurry uses 42.5 grade ordinary Portland cement slurry with a water-cement ratio of 1:1. The slurry pressure is controlled at 0.2-0.3MPa. The grouting pressure gradually increases with the grouting process to reach the designed grouting pressure and continue grouting for more than 30 minutes.

[0065] S3, construction of long pipe sheds 3 and full-section grouting. The arch of the dark excavation channel 1 uses several long pipe sheds 3 as advance support, and the long pipe sheds 3 are arranged in an arch shape; the soil within 2m outside the excavation contour line 8 of the dark excavation channel 1 is grouting reinforced, and then double rows of advance small guide tubes 4 are arranged above the long pipe sheds 3 to ensure the stability of the excavation working surface;

[0066] The construction process of the long pipe shed 3 includes: building a guide wall, drilling holes, jacking the long pipe shed 3, cleaning holes and grouting.

[0067] In this embodiment, the dark excavation section is 55m long, and the arch is provided with a single row of Φ108mm×6mm long pipe racks 3, a total of 32 pipe racks, 54m long, with an annular 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 accurate advancement of the long pipe rack 3, a guide pipe 7 is arranged in the hole after drilling to improve the installation accuracy.

[0069] Since the long pipe shed 3 is long and difficult to control the accuracy, in this embodiment, the long pipe shed 3 is divided into two sections and laid separately, each section is laid for 30m, and the overlapping 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 in the soil within 2m outside the excavation contour line 8 of the dark excavation channel 1. The diameter of the grouting hole opening is not less than 108mm, and the diameter of the final hole is not less than 90mm. The orifice pipe adopts a hot-rolled seamless steel pipe with a diameter of 108mm and a wall thickness of 5mm, and the pipe length is 3m. The spacing between the bottom of the grouting holes is 1.4m, and the grouting holes in each circle are arranged at a spacing of about 0.7m along the axis of the circle. The length of each grouting cycle is 15m, 12m is excavated, and a 3m stop rock plate is retained. The drilling and grouting sequence is from outside to inside, and the holes in the same circle are constructed at intervals.

[0071] Before the horse head gate is demolished, in order to ensure construction safety, a double row of advanced small guide tubes 4 are set above the large pipe shed (reference Figure 2 and Fig. 9 ), the advance small pipe 4 adopts double rows of φ42×3.5mm advance small pipes 4 within the 180° range of the arch part except the hole entry position, with a length of 4m, annular spacing of 300mm, external insertion angle of 5~10°, and holes are drilled every 150mm on the pipe wall to form grouting holes, with a hole diameter of 6mm. The grouting slurry adopts 42.5 ordinary silicate cement slurry, the water-cement ratio of cement slurry is 1:1 (weight ratio), the grouting pressure is: 0.5~1.0MPa, and the grouting diffusion radius is not less than 0.3m.

[0072] In the 180° range of the arch excavation, double rows of small advance guide tubes 4 are set except for the entrance position. The small advance guide tubes 4 are 4m long, with an annular spacing of 300mm and an external insertion angle of 5 to 10°. Grouting holes are formed by staggered drilling every 150mm on the pipe wall. The diameter of the holes is 6mm and the grouting diffusion radius is not less than 0.3m.

[0073] S4, the demolition of the horse head gate, in the order of upper left, lower left, upper right and lower right, the No. 1 hole 10, No. 2 hole 11, No. 3 hole 12 and No. 4 hole 13 of the horse head gate are demolished in turn, and temporary horizontal braces and temporary vertical braces are set up, which specifically includes the following steps:

[0074] (1) Start to break the retaining wall and sprayed anchor surface at the 10th horse head gate of the No. 1 tunnel in a circular manner, and the reserved core soil will not be broken for the time being. After the cleaning is completed, three steel frames are closely arranged under the retaining wall, and temporary vertical supports are set up in the middle, nets are hung, and sprayed anchor support is provided; the core soil area is retained, and the reserved core soil area is not less than 50% of the excavation area. The excavation cycle is continued, the core soil and the retaining wall and sprayed anchor surface at the temporary invert are broken, and temporary horizontal supports are set up to make the No. 1 temporary closure into a ring;

[0075] (2) After the excavation of No. 1 tunnel 10 is temporarily closed into a ring of 3m, the retaining wall and sprayed anchor surface of the No. 2 tunnel 11 horse head gate area are removed. The reserved core soil is not removed for the time being. After the cleaning is completed, three steel frames are closely arranged at the horse head gate, and a temporary vertical support is set up in the middle, which is connected to the reserved steel frame node of No. 1 tunnel 10, and the whole is closed into a ring, and the net is hung and sprayed anchor support is provided.

[0076] (3) After the No. 2 tunnel 11 is closed into a ring of 3m, the retaining wall and sprayed anchor surface of the No. 3 tunnel 12 are broken in the ring direction, and the reserved core soil is not broken for the time being. After the cleaning is completed, three steel frames are erected closely under the retaining wall, connected to the reserved node of the No. 1 tunnel 10, and meshes are hung and sprayed anchors are used for support; the core soil area is retained, and the circular excavation is continued, the core soil and the retaining wall and sprayed anchor surface at the temporary invert are broken, and temporary cross braces are erected to make the No. 3 tunnel temporarily closed into a ring.

[0077] (4) After the excavation of tunnel No. 3 12 is temporarily closed into a ring of 3m, the demolition of the retaining wall and shotcrete surface of the gate area of ​​tunnel No. 4 13 begins.

[0078] Tunnel No. 4 13 is excavated in full section, with three steel frames densely arranged at the horse head gate, and connected with the reserved steel frame nodes of Tunnel No. 2 and Tunnel No. 3 12, forming a closed ring as a whole.

[0079] S5, excavation of the dark excavation channel 1, using the CRD method to excavate the dark excavation channel 1; Fig.11 As shown, the upper step part 14, the lower step part 2 15, the upper step part 3 16 and the lower step part 4 17 are excavated in sequence, and initial support is provided in time, and the middle partition wall 20 and the middle partition board 19 are set;

[0080] In S5, the underground tunnel 1 includes the following steps:

[0081] (1) Excavation of the first part 14 of the upper step, with a cycle advance of 0.5 m, initial support, installation of the middle partition 20 and temporary middle partition 19, and grouting behind the initial support;

[0082] (2) The lower step 2 was excavated at 15, with a cycle advance of 0.5 m, lagging behind the upper step 1 at 143 m, and initial support was applied, a middle partition wall 20 was set, and grouting was carried out behind the initial support;

[0083] (3) Excavation of the upper step 3 16, with a cycle advance of 0.5m, lagging behind the lower step 2 153m, and initial support, temporary partition 19, and grouting behind the initial support;

[0084] (4) The excavation of the fourth part of the lower step 17 was carried out with a cycle advance of 0.5m, lagging behind the third part of the lower step by 3m, and initial support was applied, and grouting was carried out behind the initial support.

[0085] In addition, the underground excavation passage is also provided with a reserved connection opening 2 for civil air defense in order to cope with emergencies.

[0086] S6, initial support construction, prepare the steel arch frame 18 and the steel mesh 6, first install the steel arch frame 18, then weld the steel mesh 6 to the steel arch frame 18, after the steel mesh 6 is welded, spray concrete in the order of arch foot first and arch top, wait for the concrete to solidify, and cure the concrete for no less than 14 days, and finally perform grouting behind the initial support;

[0087] S7, waterproof layer 5 and secondary lining construction, remove the middle partition 20 at intervals, 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 54 and an ECB waterproof board 51, the thickness of the ECB waterproof board 51 is not less than 2.0 mm, the non-woven fabric buffer layer 54 is made of 400g / m 2 Short brazing non-woven fabric; then remove the middle partition 19 and the partition wall 20, lay the waterproof layer 5, and pour the upper secondary lining;

[0088] In S7, the construction of the waterproof layer 5 includes the following steps: bottom cleaning and base surface treatment, laying of the non-woven fabric buffer layer 54 and the plastic waterproof board 51, construction of the fine stone concrete protective layer, construction joint waterproofing, special location waterproofing and construction of the grouting system.

[0089] 1. Bottom cleaning and base surface treatment:

[0090] (1) Use manual labor and mechanical means to clean the bottom, and pay attention to the protection of the initial support of the channel during the cleaning process.

[0091] (2) The base surface for laying the waterproof board 51 should be free of visible water flow.

[0092] (3) The base surface for laying the waterproof board 51 should be flat. Before laying the waterproof board 51, the base surface should be leveled. The treatment method can be spraying concrete or 1:2.5 cement mortar plastering. The treated base surface should meet the following conditions: the surface of the base layer should be flat and clean, without looseness, hollows, and cracks. Its flatness should meet the requirement of D / L≤1 / 10, where D is the maximum depth of the concave of two adjacent convex surfaces; L is the shortest distance between two adjacent convex surfaces.

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

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

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

[0096] 2. Laying of non-woven fabric buffer layer 54 and plastic waterproof sheet 51:

[0097] The waterproof board 51 is laid using a nail-free laying process, such as Fig.15 As shown, hot-melt double-seam welding is adopted for welding (local details can also be welded manually), the overlap width of the waterproof board 51 is 100mm, and the width of each weld is 15mm. When laying the waterproof layer 5, it is divided into two rings, the inverted arch and the arch wall. The bottom plate waterproof board 51 is laid 500mm higher than the bottom plate steel bar and 500mm longer than the steel bar in the longitudinal direction, so as to overlap with the arch wall and the next cycle. The waterproof layer 5 is laid along the ring direction.

[0098] (1) Laying buffer layer 54

[0099] like Fig.14As shown, before laying the waterproof board 51, the buffer layer 54 should be laid first, and the buffer layer 54 should be fixed on the base surface with cement nails 53 (or expansion bolts) and plastic round washers 52 that match the waterproof board 51. When fixing, the nail heads must not protrude from the plane of the washers 52. The fixing points are arranged in a plum blossom shape, with a fixed spacing of 80 to 100 cm on the side wall; a fixed spacing of 50 to 80 cm on the top arch; a fixed spacing of 1.5 to 2 m on the waterproof board 51 on the inverted arch; and the fixed spacing of the connection between the bottom plate and the side wall should be appropriately increased to 50 cm. Round washers 52 should be added to the concave parts of the base surface to prevent the waterproof board 51 from hanging in the concave parts; the plastic round washers 52 have a concave hole in the middle to prevent the nails from exceeding the plane of the round washers 52 to avoid piercing the waterproof layer 5.

[0100] The buffer layer 54 is connected by overlapping, and the overlapping width is 50mm. The overlapping seam can be welded by spot bonding or fixed with a plastic gasket 52. When laying, the buffer layer 54 should be closely attached to the base surface and should not be pulled too tight or have large bulges, so as not to affect the laying of the waterproof board 51.

[0101] (2) Laying plastic waterproof board 51

[0102] 1) When laying the waterproof board 51, the laying direction of the waterproof board 51 is mainly to minimize the occurrence of manual welds, and no cross welds should appear (that is, no four-layer material tower connection parts should appear). The arch wall and inverted arch waterproof board 51 should be laid longitudinally along the dark excavation channel 1, and 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 by a hot air welding gun. The welding should be firm and reliable to avoid the waterproof board 51 from falling off during pouring and vibrating the concrete. It is strictly forbidden to weld through the waterproof board 51 during welding.

[0104] 3) When fixing the waterproof sheet 51, care should be taken not to overtighten it or cause large bulges. The laid waterproof sheet 51 should be consistent with the undulations of the base surface and remain natural, flat and close to the base surface, so as not to affect the size of the secondary lining concrete or cause the waterproof sheet 51 to separate from the round gasket 52.

[0105] 4) The joints between the waterproof boards 51 are welded by double welds with a lap width of 10 cm. After welding, the leak detection is performed with a leak detection gas with an inflation pressure of 0.25 Mpa (2.5 Rar). After 15 minutes of observation, if the pressure drop is less than 10%, it is qualified. If the pressure drop is too large and does not meet the requirements, the leak point should be found and repaired in time.

[0106] 5) In addition to normal construction, the longitudinal and circumferential overlaps of the waterproof sheet 51 are covered with another layer of waterproof sheet 51 of the same material and welded by hot-melt welding; when overlapping circumferentially, the lower waterproof sheet 51 should press the upper waterproof sheet 51. When welding multiple layers of waterproof sheets 51, the welds at the overlaps must be staggered, and no more than three layers of seams may overlap.

[0107] 6) After the waterproof board 51 is laid, its surface should be fully inspected. If damaged parts are found, they should be repaired in time. The patch should be cut into rounded corners, and the distance between the edge of the patch and the damaged edge should not be less than 7cm. The patch should be fully welded, and plastic welding rods should be used to reinforce the weld. There should be no warped edges or hollow parts.

[0108] 7) The joints of all waterproof boards 51 should be at least 40cm longer than the reserved lap reinforcement. The joints can also be rolled up and fixed. If the joints are too short, the subsequent jointing will be impossible to operate.

[0109] 3. Waterproof construction of construction joints

[0110] The deformation joint of the dark excavation channel 1 adopts a medium-hole steel edge rubber waterstop, the circumferential construction joint adopts a flat web steel edge rubber waterstop, and the horizontal construction joint adopts a galvanized steel plate waterstop. The construction joint is pre-buried with a repeatable grouting pipe 9. The location of the settlement joint must allow the arch ring, side wall and invert to penetrate at the same mileage.

[0111] (1) Circumferential construction joint waterproofing construction

[0112] 1) If Fig.16 As shown, the water stop is set at the position of half the lining thickness, and the width buried in the concrete and exposed is half the width of the water stop. Drill a φ12mm steel bar hole on the end template every 50cm along the lining loop. Pass the prefabricated steel bar clamp through the stop template, clamp the inner side into half of the water stop, and the other half of the water stop is flat against the stop board and fixed with wire. After the concrete solidifies, remove the stop board, straighten the water stop, then bend the steel bar to clamp the water stop, and mold the next cycle of concrete.

[0113] 2) When pouring secondary lining concrete, strengthen the concrete vibration to eliminate bubbles and gaps at the bottom of the waterstop and ensure that the waterstop and concrete are tightly combined.

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

[0115] (2) Longitudinal construction joint waterproofing construction

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

[0117] 2) Installation of steel plate waterstop: The waterstop is fixed to the structural steel bar by wire or welding, with a fixed spacing of 40cm. It is required to be fixed firmly and reliably to avoid the fixing point falling off during pouring and vibrating concrete, causing the waterstop to fall over and twist, affecting the waterstop effect. The waterstop should be accurately positioned and firmly fixed. In particular, the template sealing plate should be firmly fixed to avoid the expansion of the mold affecting the positioning accuracy of the waterstop.

[0118] 3) Connection of steel plate waterstop: The connection of steel plate waterstop in the same direction adopts full-width butt welding and lap full welding, and the lap width is not less than 50mm. The connection of steel plate waterstops that intersect each other adopts full-width lap connection.

[0119] 4) Chiseling, debris treatment and chiseling surface treatment of construction joints: Before pouring concrete on horizontal construction joints, the surface slurry and debris must be removed, cement mortar must be spread 2cm first, and then concrete is poured. The chiseling depth should not be less than 20mm, and the fresh surface of the concrete must be completely chiseled out.

[0120] (3) Expansion joint waterproof structure

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

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

[0123] 3) Stainless steel water collection troughs are installed on the inner side of the arch and side walls at the deformation joints to guide a small amount of seepage water into the ditch in an organized manner and discharge it into the wastewater pump room. Polyurethane sealant is embedded inside the bottom plate.

[0124] 4. Waterproof construction of special parts

[0125] (1) Special closing treatment of waterproof board 51

[0126] 1) At the interface of the dark excavated channel 1, a post-cast hole opening ring beam is molded, and a grouting pipe 9 is pre-buried between the post-cast hole opening ring beam and the inner lining of each structure. The closing ring protrudes 5 to 10 cm from the wall end, and a water diversion trough is set to divert water. A stainless steel interface groove should be set at the pipe segment and the cast-in-place hole opening. The surrounding rock outside the interface should be grouting treated.

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

[0128] (2) In special locations where it is not possible to install waterstop strips, double-pass water-swelling waterstop glue + grouting pipe 9 should be used for waterproofing.

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

[0130] S8, secondary lining backfill grouting, backfill grouting to the back of the secondary lining through the grouting pipe 9.

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

[0132] Before grouting, water is injected first to detect the leak (and to estimate the amount of slurry used). For larger leaks, quick-drying cement or epoxy resin can be used to plug the surface before injecting directly into the leaking part. The grouting pressure is controlled within 0.2MPa.

[0133] Grouting should be carried out after the secondary lining concrete strength reaches more than 75% of the design strength. When the grouting pressure reaches the design final pressure or grouting occurs in adjacent holes, the grouting of this hole can be ended. After stopping the grouting, immediately close the orifice valve, then remove and clean the pipeline, and after the slurry has initially set, remove the orifice valve and fill and compact the grouting hole with cement mortar.

[0134] The present invention also provides a dark-cut passage at an entrance and exit of a subway station, which adopts the above-mentioned dark-cut passage construction process at the entrance and exit of the subway station.

[0135] Although this specification has shown and described a plurality of embodiments of the present invention, it is obvious to those skilled in the art that such embodiments are provided by way of example only. Those skilled in the art will think of many changes, modifications and alternatives without departing from the thought and spirit of the present invention. It should be understood that in the process of practicing the present invention, various alternatives to the embodiments of the present invention described herein may be adopted. The attached claims are intended to define the scope of protection of the present invention, and therefore cover the modular composition, equivalent or alternatives within the scope of protection of these claims.

Claims

1. A construction process for a dark excavation tunnel at a subway station entrance and exit, characterized in that: The following steps are involved: S1, construction of drainage wells, setting drainage wells on both sides of the underground tunnel (1) to lower the groundwater level and increase the stability of the soil around the underground tunnel (1); S2, grouting reinforcement of soil around pipelines. Before dark excavation, drilling and grouting are performed around pipelines to improve the overall mechanical properties of soil around pipelines. S3, long pipe shed (3) construction and full-section grouting, the arch of the dark excavation channel (1) uses a number of long pipe sheds (3) as advance support, and the long pipe sheds (3) are arranged in an arch shape; grouting reinforcement is performed on the soil within a range of 2m outside the excavation contour line (8) of the dark excavation channel (1), and then double rows of advance small guide tubes (4) are arranged above the long pipe sheds (3) to ensure the stability of the excavation working surface; S4, demolition of the horse head gate: demolition of the No. 1 hole (10), No. 2 hole (11), No. 3 hole (12) and No. 4 hole (13) of the horse head gate in the order of upper left, lower left, upper right and lower right, and erection of temporary horizontal braces and temporary vertical braces; S5, excavation of the dark tunnel (1), using the CRD method to excavate the dark tunnel (1); sequentially excavate the upper step part (14), the lower step part (15), the upper step part (16) and the lower step part (17), and perform initial support, and set up the middle partition wall (20) and the middle partition plate (19); S6, initial support construction, preparing the steel arch frame (18) and the steel mesh (6), first installing the steel arch frame (18), then welding the steel mesh (6) to the steel arch frame (18), after the steel mesh (6) is welded, concrete is sprayed in the order of arch foot first and arch top later, after the concrete solidifies, the concrete is cured for a curing time of not less than 14 days, and finally grouting operation is performed behind the initial support; S7, construction of waterproof layer (5) and secondary lining, dismantling the middle partition wall (20) at intervals, laying the waterproof layer (5) and pouring the bottom secondary lining, wherein the waterproof layer (5) includes a buffer layer (54) and a waterproof board (51); then dismantling the middle partition board (19) and dismantling the middle partition wall (20) at intervals, laying the waterproof layer (5), and pouring the upper secondary lining; S8, secondary lining backfill grouting, backfill grouting is performed behind the secondary lining through the grouting pipe (9).

2. The underground tunnel construction process for subway station entrance and exit according to claim 1 is characterized by: In S1, the dewatering well construction process includes drilling a hole, finishing the hole, lowering the well pipe, surrounding the hole with gravel and mud, and washing the well; A water filter pipe is arranged in the well pipe, and two layers of 80-100 mesh nylon mesh are wrapped on the outside of the water filter pipe as a filter layer. A sedimentation pipe is also arranged below the water filter pipe.

3. The underground tunnel construction process for subway station entrance and exit according to claim 1 is characterized by: In S2, sleeve valve pipe grouting is used to reinforce the soil within 2m in front and behind, 2m up and down, and 2m outside the excavation contour line (8) along the direction of the underground excavation channel (1). The spacing is 1×1m and the plum blossom shape is arranged. The grouting slurry uses silicate cement slurry with a water-cement ratio of 1:1 and a slurry pressure of 0.2~0.3MPa.

4. The underground tunnel construction process for subway station entrance and exit according to claim 1 is characterized by: 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 circumferential spacing of the long pipe shed (3) is 400 mm, and the external insertion angle is 0.5°; when being installed, the long pipe shed (3) is divided into two sections and installed separately, and the overlapping 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); In the 180° range of the arch excavation, double rows of small advance conduits (4) are arranged except for the hole entry position. The small advance conduits (4) are 4m long, with an annular 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 diameter of the holes is 6mm, and the grouting diffusion radius is not less than 0.3m.

5. The underground tunnel construction process for subway station entrance and exit according to claim 1 is characterized by: In S5, the underground tunnel (1) includes the following steps: (1) Excavation of the upper step (14), with a cycle advance of 0.5 m, initial support, installation of the middle partition wall (20) and temporary middle partition board (19), and grouting behind the initial support; (2) The lower step part 2 (15) is excavated with a cycle advance of 0.5 m, lagging 3 m behind the upper step part 1 (14), and initial support is applied, a middle partition wall (20) is set, and grouting is performed behind the initial support; (3) Excavation of the third part of the upper step (16) with a cycle advance of 0.5 m, lagging 3 m behind the second part of the lower step (15), and initial support and temporary partition (19) are carried out, while grouting is carried out behind the initial support; (4) The fourth part of the lower step (17) was excavated with a cycle advance of 0.5 m, lagging 3 m behind the third part of the lower step, and initial support was applied, while grouting was carried out behind the initial support.

6. The underground tunnel construction process for subway station entrance and exit according to claim 1 is characterized by: In S7, the construction of the waterproof layer (5) includes the following steps: Bottom cleaning and surface treatment, laying of non-woven fabric buffer layer (54) and plastic waterproof board (51), construction of fine stone concrete protective layer, waterproofing of construction joints, waterproofing of special parts and construction of grouting system; The secondary lining construction includes the following steps: steel bar production and installation, formwork and support system construction, scaffolding erection and secondary lining concrete pouring.

7. A dark excavation tunnel structure at the entrance and exit of a subway station, characterized in that: The underground subway station entrance and exit dark excavation passage construction process described in any one of claims 1-6 is adopted.

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