Construction method for subway station with upper portion and lower portion closely attached to existing tunnel

Abstract

The invention discloses a construction method for a subway station with the upper portion and the lower portion closely attached to an existing tunnel. Firstly, an area to be excavated is subjected to advance support; 2, dividing a to-be-excavated area into a plurality of pilot tunnels, preferentially constructing the pilot tunnels which are closely attached to the existing tunnel at the upper part and the lower part, and constructing the other pilot tunnels at intervals; and thirdly, an upper step with the upper portion and the lower portion tightly attached to the existing tunnel pilot tunnel is excavated, after one step pitch is excavated, a temporary support is built, primary support construction is conducted immediately, after a primary support structure is formed, a corresponding lower step is excavated, the temporary support is built, and primary support construction is conducted immediately. And fourthly, after the primary supporting structures of the upper step and the lower step are formed, the temporary supports are dismantled, and secondary lining construction is conducted. And fifthly, the third step and the fourth step are repeated, advancing is conducted one by one step pitch, and pilot tunnel construction is completed. And 6, excavating the rest pilot tunnels at intervals to finish the construction of the subway station. By applying the method, the technical problem that construction safety and structural safety are difficult to guarantee during construction of the subway station which is closely attached to the existing tunnel up and down in the existing construction technology can be solved.

Description

Technical Field

[0001] The invention relates to the technical field of underground structure construction, in particular to a method for constructing a subway station which is closely attached to an existing tunnel from top to bottom. Background Art

[0002] In order to achieve an ideal transfer effect between new subway lines and existing line stations, the new station will be built under the existing station in a cross-shaped manner to minimize the transfer distance. However, there are often multiple existing tunnels at the appropriate construction location for the new station, which has led to a gradual increase in the number of projects that cross over and under existing lines.

[0003] For the construction of close-fitting underpasses of existing structures, the underpass section construction must be completed under the condition of ensuring the normal operation of the existing line. Therefore, the settlement control of the existing tunnel is extremely strict, and the basic requirement is to control the settlement within 3mm. For the construction of subway stations that cross existing tunnels, since it is necessary to excavate the soil layer above the existing structure below, the pressure above the existing structure will be lost, which may cause the existing tunnel to float up.

[0004] At present, the research on close-fitting overspan and underpass engineering at home and abroad mainly focuses on the single working condition of close-fitting overspan or close-fitting underpass, and there is less research on engineering close-fitting existing structures above and below. In addition, close-fitting construction mostly adopts multiple guide holes and small step distances to ensure construction safety, mainly reducing the disturbance to the existing structure from the new structure, but it cannot actively control the disturbance during the construction process. There are also grouting between the bottom plate of the existing structure and the top plate of the new structure to provide a certain lifting force to the overlying existing structure, filling the gap between the existing structure and the new structure caused by the inability to compact the confined space or the shrinkage of concrete, thereby reducing its settlement. The existing grouting method mainly uses reserved grouting holes or buried grouting bags. Since the position of the cavity caused by concrete shrinkage is difficult to confirm, the method of reserving grouting holes cannot control the problem of slurry loss, and the grouting effect cannot be guaranteed. The buried grouting bag causes the existing structure and the new structure to separate, posing a safety hazard, and cannot effectively fill the shrinkage cavity. Summary of the invention

[0005] The purpose of the present invention is to provide a method for constructing a subway station that is closely attached to an existing tunnel, which can solve the technical problem that it is difficult to ensure construction safety and structural safety during the construction of a subway station that is closely attached to an existing tunnel.

[0006] In order to achieve the above object, the present invention adopts the following technical solution.

[0007] A method for constructing a subway station that is closely attached to an existing tunnel from top to bottom comprises the following steps.

[0008] Step 1: Carry out advance support construction on the area to be excavated.

[0009] Step 2: Divide the area to be excavated into multiple pilot tunnels, give priority to constructing the pilot tunnels that are closely attached to the existing tunnels above and below, and construct the remaining pilot tunnels at intervals.

[0010] Step 3: Excavate the upper and lower steps closely following the upper step of the existing tunnel guide tunnel. After excavating one step, build temporary support. After the temporary support is built, carry out the initial support construction. After the initial support structure of the upper step is formed, excavate the corresponding lower step. After the excavation is in place, build temporary support. After the temporary support is built, carry out the initial support construction.

[0011] Step 4: After the primary support structures of the upper and lower steps in a step are formed, remove the temporary support and carry out the secondary lining construction of the step.

[0012] Step 5. Repeat steps 3 and 4 above, advancing step by step, to complete the excavation, primary support and secondary lining construction of the existing tunnel guide tunnel that is closely attached to the top and bottom.

[0013] Step 6: Dig the remaining guide tunnels at intervals to complete the construction of the subway station that is closely attached to the existing tunnel above and below.

[0014] Furthermore, in step three, after the upper step is excavated in place, an arch foot groove is excavated at the bottom of the side wall along the length direction of the tunnel, the arch foot groove is cleaned and reinforced, and an upper step support plate, an arch top support plate and a support rod for temporary support are installed. A protrusion embedded in the arch foot groove is provided at the lower part of the upper step support plate, one end of the support rod is connected to the inner side of the protrusion, and the other end is connected to the bottom of the arch top support plate, which is used to simultaneously provide an upward supporting force to the arch top support plate and provide pressure to the upper step support plate to the side wall of the guide tunnel, and the temporary support of the upper step part is completed.

[0015] After the excavation of the lower step is completed, the arch foot is cleaned and reinforced, and the lower step support plate and support rod for temporary support are installed. The lower step support plate is L-shaped, and the two lower step support plates are arranged opposite to each other for temporary support of the lower step. One end of the support rod in the lower step is connected to the connection point on the support rod in the upper step, and the other end is connected to the corner of the lower step support plate, which is used to apply downward pressure to the lower step support plate and to the side wall of the guide tunnel.

[0016] Furthermore, the length of the support rod is adjustable. The support rod includes a supporting part and an adjusting part. Both ends of the adjusting part are provided with threads with opposite rotation directions. The two supporting parts are respectively matched with the two ends of the adjusting part through threads. Rotating the adjusting part can make the two supporting parts approach or move away from each other to shorten or lengthen the support rod. The end of the supporting part is provided with a hinge hole for connecting with the support plate.

[0017] Furthermore, a locking structure for locking the supporting part and the adjusting part is provided on the supporting part, and the locking structure includes a tapered thread clip and a locking nut provided at one end of the supporting part close to the adjusting part. The supporting part is provided with a tapered thread at one end close to the adjusting part, and a plurality of grooves are circumferentially provided at the position where the tapered thread is provided to form a plurality of tapered thread clips. Rotating the locking nut can enable the tapered thread clip to clamp the adjusting part to achieve locking of the supporting part and the adjusting part.

[0018] Furthermore, in step three, when performing the initial support construction of the upper step, a rubber bag is first laid on the top of the guide tunnel, and then the initial support structure is constructed.

[0019] Furthermore, a closed grouting port which can be broken open under a certain pressure is provided on the rubber bladder, a hard grouting pipe is passed through the rubber bladder, and grouting ports are evenly provided on the grouting pipe.

[0020] Furthermore, in step five, after the second lining that is tightly attached to the existing tunnel guide tunnel at both top and bottom is completed, grouting is injected into the pre-buried rubber bag through a hard grouting pipe to fill the gap between the newly built structure and the bottom of the existing tunnel above, so that the newly built structure and the existing tunnel structure above are consolidated into an integral structure through the slurry.

[0021] Furthermore, in step six, when the remaining guide tunnels are excavated, the upper step of the guide tunnel is excavated first. After excavating one step, a temporary support is built. After the temporary support is built, the initial support construction is carried out immediately. After the initial support structure of the upper step is formed, the corresponding lower step is excavated. After the excavation is in place, a temporary support is built. After the temporary support is built, the initial support construction is carried out immediately. After the initial support structure is formed, the temporary support is removed, and the secondary lining construction of the step is carried out. The construction is advanced step by step to complete the construction of the corresponding guide tunnel.

[0022] Furthermore, since there is no existing tunnel below the remaining pilot tunnels, the temporary support adopts a normal vertical arch frame or jack structure.

[0023] Furthermore, in step six, after the secondary lining structural strength of the previous batch of pilot tunnels reaches 80%, the construction of the next batch of pilot tunnels begins.

[0024] After adopting the above technical solution, the present invention has the following beneficial effects: 1. The present invention gives priority to excavating a pilot tunnel that is closely attached to the existing tunnel from top to bottom. At this time, the soil is not disturbed and is in a safe state. After the pilot tunnel is excavated, the surrounding rock can be used as a force-bearing structure to provide conditions for the installation of the supporting structure. 2. When excavating the pilot tunnel, it is divided into upper and lower steps for step-by-step excavation, and temporary support and primary support construction are carried out in a timely manner to further reduce the disturbance caused by excavation construction to the surrounding soil and existing structures; 3. The present invention uses support plates and support rods as temporary support structures, which can be prefabricated in factories and assembled on site, making the construction convenient, safe and fast; the support rods adopt a telescopic design, which can actively control the settlement of the existing upper structure and transfer part of the pressure to the existing tunnel below, which can effectively prevent the existing tunnel below from floating up; the support rods are connected to the support plates by high-strength bolts, which are convenient for installation and removal, and can be recycled; 4. Support plates and support rods are used as temporary supports. The existing tunnel structure below is not directly stressed, which avoids possible damage to the existing structure during construction. The support rods are tilted from the arch top to the arch foot, which can minimize the occupation of construction space; 5. A grouting bag is provided between the primary support structure of the pilot tunnel and the existing tunnel above. It is used to inject grout into the gap between the new structure and the existing structure after the secondary lining structure is completed. The settlement of the existing structure above can also be actively controlled by grouting. Grouting makes the new structure and the existing structure form a whole, thereby improving the safety of the overall structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of dividing the area to be excavated into multiple pilot tunnels in the present invention.

[0026] Figure 2 It is a schematic diagram of the position of the pilot tunnel of the existing tunnel which is preferably constructed above and below.

[0027] Figure 3 It is a schematic diagram of the state of the first batch of construction guide tunnels of the intermediate excavation of the remaining guide tunnels in the present invention.

[0028] Figure 4 It is a schematic diagram of the state of the second batch of construction guide tunnels of the intermediately excavated remaining guide tunnels of the present invention.

[0029] Figure 5 It is a schematic diagram of the state in which the upper and lower parts of the present invention are closely attached to the upper steps of the existing tunnel pilot tunnel excavation.

[0030] Figure 6 It is a schematic diagram of the state in which the upper and lower parts of the present invention are closely attached to the arch foot groove excavated on the step of the existing tunnel guide hole.

[0031] Figure 7 It is a schematic diagram of the overall structure of the temporary support for the upper steps of the existing tunnel guide hole, which is tightly attached to the upper and lower parts in the present invention.

[0032] Figure 8 It is a schematic diagram of the state in which the upper and lower parts of the present invention are closely attached to the lower step of the excavation of the existing tunnel pilot hole.

[0033] Fig. 9 It is a schematic diagram of the overall structure of the temporary support for the lower step of the existing tunnel guide tunnel in the present invention, which is tightly attached to the upper and lower parts.

[0034] Fig.10 yes Fig. 9 A magnified schematic diagram of center A.

[0035] Fig.11 It is a schematic diagram of the overall structure of the support rod in the present invention.

[0036] Fig.12 It is an enlarged schematic diagram of the support rod locking structure in the present invention.

[0037] Description of the drawings: 1. existing tunnel, 2. new structure, 21. existing tunnel guide holes tightly attached to the upper and lower parts, 22. other guide holes, 3. upper step, 31. arch foot groove, 4. lower step, 51. upper step support plate, 52. arch top support plate, 53. lower step support plate, 6 support rod, 61. support part, 62. adjustment part, 63. tapered thread clip, 64. locking nut. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the characteristics and performance of a subway station construction method that is closely attached to an existing tunnel above and below in the present invention are further described in detail below in conjunction with the accompanying drawings and embodiments.

[0039] Embodiment 1 Please see attached Figures 1 to 12 A method for constructing a subway station that is closely attached to an existing tunnel from top to bottom includes the following steps.

[0040] Step 1: Carry out advance support construction in the area to be excavated. Considering that the new tunnel is closely attached to the existing tunnel, a large pipe shed and full-section grouting can be used to reinforce the soil in front of the excavation.

[0041] Step 2: Divide the area to be excavated into multiple pilot tunnels, give priority to constructing the pilot tunnel 21 that is closely attached to the existing tunnel from top to bottom, and construct the remaining pilot tunnels at intervals.

[0042] like Figures 1 to 4 As shown, the locations of multiple pilot tunnels are divided in the area to be excavated. First, the pilot tunnel 21 of the existing tunnel is excavated closely above and below, that is, the pilot tunnel in the area I position. Then, the pilot tunnels in the area II position are excavated at intervals. After the secondary lining structure strength of the pilot tunnel in the area II reaches 80%, the excavation construction of the pilot tunnel in the area III is finally carried out.

[0043] Step 3: Figure 5 As shown, the upper step 3 of the existing tunnel guide 21 is excavated closely on both the upper and lower sides. After excavating a step distance, an arch foot groove 31 is excavated at the bottom of the side wall along the length direction of the tunnel, as shown in FIG. Figure 6 As shown, the arch foot groove 31 is cleaned and reinforced. The length of each step is determined according to factors such as the project scale and the terrain structure. As a preferred embodiment, each step is set to 0.5 meters in this embodiment.

[0044] like Figure 7 As shown, after the upper step 3 is excavated in place, temporary support is built, and the upper step support plate 51, the arch support plate 52 and the support rod 6 for temporary support are installed. The lower part of the upper step support plate 51 is provided with a protrusion embedded in the arch foot groove 31. One end of the support rod 6 is connected to the inner side of the protrusion, and the other end is connected to the bottom of the arch support plate 52, which is used to simultaneously provide an upward support force to the arch support plate 52 and provide pressure to the side wall of the guide tunnel on the upper step support plate 51. The temporary support of the upper step 3 is completed. After the temporary support is built, the initial support construction is immediately carried out. When the initial support construction of the upper step 3 is carried out, a rubber bag is first laid on the top of the guide tunnel, and then the initial support structure is constructed. The rubber bag is provided with a closed grouting port that can be broken under a certain pressure. A hard grouting pipe is inserted into the rubber bag, and the grouting port is evenly arranged on the grouting pipe.

[0045] After the initial support structure of the upper step 3 is formed, the corresponding lower step 4 is excavated. After the excavation of the lower step 4 is completed, the arch foot is cleaned and reinforced. Figure 8 shown.

[0046] like Fig. 9 As shown, after the lower step 4 is excavated in place, temporary support is built, and the lower step support plate 53 and support rod 6 for temporary support are installed. The lower step support plate 53 is L-shaped, and two lower step support plates 53 are relatively arranged for temporary support of the lower step 4. One end of the support rod 6 in the lower step 4 is connected to the connection point on the support rod 6 in the upper step 3, and the other end is connected to the corner of the lower step support plate 53, which is used to apply downward pressure to the lower step support plate 53 and the side wall of the guide tunnel to prevent the existing tunnel below from floating due to the unloading of earthwork excavation. After the temporary support is built, the initial support construction is carried out immediately.

[0047] When the existing tunnel guide hole 21 is excavated, the excavated side wall is not vertical, but presents an arc shape toward the surrounding rock. This shape can better disperse the pressure of the upper supporting structure to the side wall surrounding rock.

[0048] The length of the support rod 6 can be adjusted. Fig.11 As shown, the support rod 6 includes a support portion 61 and an adjusting portion 62. Both ends of the adjusting portion 62 are provided with threads with opposite rotation directions. The two support portions 61 are respectively matched with the two ends of the adjusting portion 62 through threads. Rotating the adjusting portion 62 can make the two support portions 61 approach or move away from each other to achieve the shortening or lengthening of the support rod 6. The end of the support portion 61 is provided with a hinge hole for connecting with the support plate.

[0049] like Fig.12As shown, the support portion 61 is also provided with a locking structure for locking the support portion 61 and the adjusting portion 62. The locking structure includes a tapered thread clip 63 and a locking nut 64 provided at one end of the support portion 61 close to the adjusting portion 62. The support portion 61 is provided with a tapered thread at one end close to the adjusting portion 62, and a plurality of grooves are circumferentially provided at the position where the tapered thread is provided to form a plurality of tapered thread clips 63. Rotating the locking nut 64 can enable the tapered thread clip 63 to clamp the adjusting portion 62 to achieve locking of the support portion 61 and the adjusting portion 62.

[0050] When the support rod 6 is used to support the support plate, the adjusting portion 62 is rotated to adjust the length of the support rod 6 so that both ends thereof are connected to the connecting members provided at corresponding positions on the support plate through high-strength bolts, and the adjusting portion 62 is further rotated to extend the support rod 6 so that the support plates at both ends are pressed against the corresponding support surfaces. When the adjusting portion 62 is rotated so that the supporting force reaches a predetermined value, the locking nut 64 is rotated so that the tapered threaded clip 63 clamps the adjusting portion 62 to lock the length of the support rod 6.

[0051] The construction of the primary support structure includes erecting I-beams, hanging mesh, and shotcrete construction. The I-beams can be set close to the temporary support structure. After the primary support is formed, the main support structure is transferred from the temporary support structure to the primary support structure.

[0052] Step 4: After the primary support structures of the upper and lower steps in a step are formed, remove the temporary support and carry out the secondary lining construction of the step.

[0053] Step 5: Repeat the above steps 3 and 4, and advance step by step to complete the excavation, primary support and secondary lining construction of the existing tunnel guide hole 21 that is closely attached to the upper and lower parts.

[0054] After the secondary lining 21 of the existing tunnel guide hole 21 is completed, grouting is injected into the pre-buried rubber bag through the hard grouting pipe. The slurry flows along the hard grouting pipe and enters the rubber bag through the grouting port on the hard grouting pipe. When there is a cavity between the bottom of the existing tunnel above and the top plate of the newly built station, the closed grouting holes on the rubber bag located at the cavity position are broken open by the slurry inside under the action of pressure, and the slurry flows into the cavity for compaction, so that the newly built station and the upper tunnel are consolidated into an integral structure through the slurry.

[0055] In addition, the settlement of the upper tunnel can be monitored. When the settlement of a certain location is too large, the rubber bag can be grouting to achieve the purpose of lifting the upper tunnel.

[0056] Step 6: Excavate the remaining pilot tunnels at intervals to complete the construction of the subway station that is close to the existing tunnel above and below. Figures 3-4As shown, the pilot tunnels in area I have been excavated, and the remaining pilot tunnels will be excavated first in area II. After the secondary lining structure strength of the previous batch of pilot tunnels reaches 80%, the construction of the next batch of pilot tunnels, namely the pilot tunnels in area III, will begin.

[0057] When excavating the remaining pilot tunnels, first excavate the upper step 3 of the pilot tunnel. After excavating one step, build a temporary support. After the temporary support is built, carry out the initial support construction. After the initial support structure of the upper step 3 is formed, excavate the corresponding lower step 4. After the excavation is in place, build a temporary support. After the temporary support is built, carry out the initial support construction. After the initial support structure is formed, remove the temporary support, and carry out the secondary lining construction of the step. Advance step by step to complete the construction of the corresponding pilot tunnel.

[0058] In particular, since there is no existing tunnel below the remaining pilot tunnels, the temporary support adopts a normal vertical arch frame or jack structure.

[0059] Embodiment 2 Different from the first embodiment, in the second embodiment, there are multiple existing tunnels below the newly built structure 2. After the excavation of the pilot tunnels that are closely attached to the existing tunnels above and below is completed, the pilot tunnel that is closely attached to the existing tunnel below is excavated first when the remaining pilot tunnels are excavated at intervals.

[0060] The method and steps for excavating the existing tunnel guide tunnel closely attached to the bottom are the same as those for excavating the existing tunnel guide tunnel closely attached to the top and bottom. Support plates and support rods are also used to form temporary support to avoid damage to the existing tunnel structure below.

[0061] It should be noted that the parts not described in detail in this scheme are all prior art, and the above embodiments are only used to illustrate the present invention, but the present invention is not limited to the above embodiments. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention fall within the protection scope of the present invention.

Claims

1. A method for constructing a subway station that is closely attached to an existing tunnel, characterized in that: The following steps are included: Step 1: Carry out advance support construction on the area to be excavated; Step 2: Divide the area to be excavated into multiple pilot tunnels, give priority to constructing the pilot tunnel (21) that is closely attached to the existing tunnel from top to bottom, and construct the remaining pilot tunnels at intervals; Step 3: excavate an upper step (3) that is closely attached to the existing tunnel guide hole (21) on both sides. After excavating a step distance, build a temporary support. After the temporary support is built, the primary support construction is immediately carried out. After the primary support structure of the upper step (3) is formed, the corresponding lower step (4) is excavated. After the excavation is in place, build a temporary support. After the temporary support is built, the primary support construction is immediately carried out; Step 4: After the primary support structures of the upper and lower steps in a step are formed, remove the temporary support and carry out the secondary lining construction of the step; Step 5: Repeat the above steps 3 and 4, and advance step by step to complete the excavation, primary support and secondary lining construction of the existing tunnel guide hole (21) that is closely attached to the upper and lower parts; Step 6: Dig the remaining guide tunnels at intervals to complete the construction of the subway station that is closely attached to the existing tunnel above and below.

2. A method for constructing a subway station that is closely attached to an existing tunnel from top to bottom as claimed in claim 1, characterized in that: In step 3, after the upper step (3) is excavated in place, an arch foot groove (31) is excavated at the bottom of the side wall along the length direction of the tunnel, the arch foot groove (31) is cleaned and reinforced, and an upper step support plate (51), an arch top support plate (52) and a support rod (6) for temporary support are installed. The lower part of the upper step support plate (51) is provided with a protrusion embedded in the arch foot groove (31), and one end of the support rod (6) is connected to the inner side of the protrusion, and the other end is connected to the bottom of the arch top support plate (52) to simultaneously provide an upward supporting force to the arch top support plate (52) and provide pressure to the upper step support plate (51) to the side wall of the guide tunnel. The temporary support of the upper step (3) part is completed. After the excavation of the lower step (4) is completed, the arch foot is cleaned and reinforced, and a lower step support plate (53) and a support rod (6) for temporary support are installed. The lower step support plate (53) is L-shaped, and two lower step support plates (53) are arranged opposite to each other for temporary support of the lower step (4). One end of the support rod (6) in the lower step (4) is connected to a connection point on the support rod (6) in the upper step (3), and the other end is connected to the corner of the lower step support plate (53) for applying pressure downward and toward the side wall of the guide hole to the lower step support plate (53).

3. A method for constructing a subway station that is closely attached to an existing tunnel from top to bottom as claimed in claim 2, characterized in that: The length of the support rod (6) is adjustable. The support rod (6) comprises a support portion (61) and an adjustment portion (62). Two ends of the adjustment portion (62) are provided with threads with opposite rotation directions. The two support portions (61) are respectively matched with two ends of the adjustment portion (62) through threads. By rotating the adjustment portion (62), the two support portions (61) can be moved closer to or farther from each other to shorten or lengthen the support rod (6). A hinge hole for connecting to a support plate is provided at the end of the support portion (61).

4. A method for constructing a subway station that is closely attached to an existing tunnel from top to bottom as claimed in claim 3, characterized in that: The support portion (61) is provided with a locking structure for locking the support portion (61) and the adjusting portion (62), the locking structure comprising a tapered thread clip (63) and a locking nut (64) provided at one end of the support portion (61) close to the adjusting portion (62), the support portion (61) being provided with a tapered thread at one end close to the adjusting portion (62), and a plurality of slots are provided along the circumferential direction at a position where the tapered thread is provided to form a plurality of tapered thread clips (63), and the locking nut (64) can be rotated to enable the tapered thread clip (63) to clamp the adjusting portion (62) to achieve locking of the support portion (61) and the adjusting portion (62).

5. The method for constructing a subway station that is closely attached to an existing tunnel from top to bottom as claimed in claim 1, characterized in that: In step 3, when the initial support construction of the upper step (3) is carried out, a rubber bag is first laid on the top of the guide hole, and then the initial support structure is constructed.

6. A method for constructing a subway station that is closely attached to an existing tunnel from top to bottom as claimed in claim 5, characterized in that: The rubber bag is provided with a closed grouting port which can be broken open under a certain pressure. A hard grouting pipe is passed through the rubber bag, and the grouting ports are evenly arranged on the grouting pipe.

7. A method for constructing a subway station that is closely attached to an existing tunnel from top to bottom as claimed in claim 6, characterized in that: In step 5, after the secondary lining is completed, which is closely attached to the existing tunnel guide hole (21) at both top and bottom, grouting is injected into the pre-buried rubber bag through a hard grouting pipe to fill the gap between the newly built structure and the bottom of the existing tunnel above, so that the newly built structure and the existing tunnel structure above are consolidated into an integral structure through grouting.

8. The method for constructing a subway station that is closely attached to an existing tunnel from top to bottom as claimed in claim 1, characterized in that: In step 6, when the remaining pilot tunnels are excavated, the upper step (3) of the pilot tunnel is excavated first. After excavating one step, a temporary support is built. After the temporary support is built, the primary support construction is immediately carried out. After the primary support structure of the upper step (3) is formed, the corresponding lower step (4) is excavated. After the excavation is in place, a temporary support is built. After the temporary support is built, the primary support construction is immediately carried out. After the primary support structure is formed, the temporary support is removed and the secondary lining construction of the step is carried out. The construction of the corresponding pilot tunnel is completed step by step.

9. A method for constructing a subway station that is closely attached to an existing tunnel from top to bottom as claimed in claim 8, characterized in that: Since there is no existing tunnel under the remaining pilot tunnels, temporary support adopts normal vertical arch frame or jack structure.

10. The method for constructing a subway station that is closely attached to an existing tunnel from top to bottom as claimed in claim 1, characterized in that: In step six, after the secondary lining structure strength of the previous batch of pilot tunnels reaches 80%, the construction of the next batch of pilot tunnels will begin.

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