Improved double-side-wall heading construction method for urban super-large-section shallow-buried station

Abstract

The application discloses an improved double-side-wall pilot tunnel construction method for urban super-large-section shallow-buried stations, which divides the double-side-wall pilot tunnel to be excavated into upper steps, middle steps and lower steps, and comprises the following steps: step A, excavating the upper step left and right pilot tunnels, and then performing main body structure support I and temporary support; step B, excavating the upper step core soil, and then constructing main body structure support II; step C, excavating the middle steps; first, excavating the middle step core soil opposite to the upper step core soil to form a draw groove, and then excavating the middle step left pilot tunnel and the middle step right pilot tunnel; step D, excavating the lower steps; excavating the lower step core soil located directly below the middle step core soil, and then continuously excavating the lower step left pilot tunnel and the lower step right pilot tunnel; and step E, performing inverted arch construction, and continuously excavating and advancing along the front and back directions of the pilot tunnels, which has the characteristics of safety and reliability, easy operation and implementation, good construction quality, fast construction progress, reduced engineering cost and reduced construction cost.

Description

Technical Field

[0001] This invention relates to the field of double-sided wall pilot tunnel construction technology, specifically to an improved double-sided wall pilot tunnel construction method for shallow-buried urban railway stations with ultra-large cross-sections. Background Technology

[0002] In the current construction of urban rail transit in my country, traditional station tunnels are mostly large cross sections exceeding 400 square meters, with geological conditions mostly classified as Class IV or V surrounding rock. Due to the influence of urban master planning and operating lines, they inevitably have to pass under dense ground buildings and structures. It is necessary not only to ensure the safety of the tunnel construction itself and properly address the impact of the tunnel project on nearby existing buildings, but also to take into account the overall construction period requirements of the TBM passing through the station.

[0003] For the excavation of ultra-large cross-section tunnels under ultra-shallow buried conditions in cities, the complex construction environment necessitates considerations of safety, reliability, speed, quality, and effective avoidance of disturbance to the surrounding area during excavation. However, the traditional double-side-wall pilot tunnel construction procedure for large cross-section tunnels has the following disadvantages: 1) long construction period and large amount of temporary support work; 2) multiple pilot tunnels requiring support; 3) high difficulty and risk in excavating the core soil of the middle and upper benches; 4) limited excavation working faces for each pilot tunnel, making it impossible to use high-power customized excavation equipment; 5) significant impact on surrounding structures from drilling and blasting operations; 6) inability to quickly form a continuous working face for initial support and lining, especially for large-span underground station tunnels that require TBM air-pushing for station passage, where it is impossible to quickly complete the invert arch construction to provide conditions for TBM passage. Summary of the Invention

[0004] This invention aims to provide an improved double-sided wall guide tunnel construction method for shallow-buried urban stations with ultra-large cross-sections, which has a short construction period, requires fewer support guide tunnels, and solves the problems of time-consuming, labor-intensive, inefficient, and poor quality of mechanical connection of steel bars caused by using torque wrenches to rotate sleeves to connect steel bars.

[0005] Therefore, the technical solution adopted in this invention is as follows: an improved construction method for double-sided wall pilot tunnels of shallow-buried urban super-large cross-section stations, which divides the double-sided wall pilot tunnel to be excavated into an upper step, a middle step, and a lower step, including the following steps:

[0006] Step A: Excavate the left and right guide tunnels of the upper step; excavate the left guide tunnel of the upper step near the left side wall of the guide tunnel and the right guide tunnel of the upper step near the right side wall of the guide tunnel in sequence, and then construct the main structure support and temporary support for the left and right guide tunnels of the upper step.

[0007] Step B: Excavate the core soil of the upper bench; After excavating the core soil of the upper bench, construct the second main structure support connected to the first main structure support at the top of the arch of the excavated core soil of the upper bench, and set up monitoring and measurement points at the arch. Finally, remove the temporary support and set up temporary grid columns to replace the excavated core soil of the upper bench to temporarily support the tunnel arch. The temporary grid columns are set at intervals along the longitudinal direction of the tunnel.

[0008] Step C: Excavate the middle bench; First, excavate the core soil of the middle bench directly opposite the core soil of the upper bench to form a trench. The excavation length of the core soil of the middle bench is less than that of the core soil of the upper bench. The temporary grid columns encountered during the excavation of the core soil of the middle bench are extended to the bottom of the middle bench by splicing, so as to continue to temporarily support the tunnel arch. Then, the left guide tunnel and the right guide tunnel of the middle bench located on both sides of the core soil of the middle bench are excavated in sequence. Finally, the initial support is constructed. The middle bench after excavation can form a bench with the upper bench.

[0009] Step D: Excavate the lower bench; excavate the core soil of the lower bench located directly below the core soil of the middle bench. The excavation length of the lower bench core soil is less than that of the middle bench core soil. Extend the temporary lattice columns encountered during the excavation of the lower bench core soil to the bottom of the lower bench by splicing, so as to continue to temporarily support the tunnel arch. Then, excavate the left and right guide tunnels of the lower bench located on both sides of the core soil of the lower bench. The excavation lengths of the left and right guide tunnels of the lower bench are less than those of the left and right guide tunnels of the middle bench, respectively. Finally, perform initial support. The excavated lower bench can form a step with the middle bench.

[0010] Step E: Construct the invert arch. When constructing the invert arch, the temporary lattice columns within the invert arch pouring area need to be removed from top to bottom. Then, pour the secondary lining concrete. At the same time, according to the steps formed by the upper, middle and lower steps, continue to excavate and advance along the front and back direction of the guide tunnel in the excavation sequence of the above steps.

[0011] As a preferred embodiment of the above scheme, in step A, excavation is carried out using customized excavation equipment. The customized excavation equipment is a 420-type excavator with a single-head drill bit and a boom shortened to 2.9m and an extension boom shortened to 3.65m. The shortened boom and extension boom of the 420-type excavator are more suitable for excavating the inside corners and perimeter of the tunnel face, greatly reducing the overall excavation time. The use of a single-head drill bit on the 420-type excavator can reduce disturbance to the unexcavated soil and reduce the risk of rockfall at the tunnel face. During excavation, the tunnel faces of the left and right guide tunnels of the upper bench are staggered by more than 5m to ensure construction safety and avoid instability caused by construction too close together. The main structure support uses I-beams to form an arch frame, and expansion shell anchors are installed at the top of each arch frame. After excavation, the left and right guide tunnels of the upper bench can penetrate the double-sided wall guide tunnels, adding active protection and effectively improving construction safety.

[0012] Further preferably, in step B, the length of the core soil excavated on the upper step is 80m. During the excavation process, a microseismic monitoring system is provided for real-time monitoring, effectively ensuring the safety of construction personnel during the excavation of the pilot tunnel and providing a safety early warning function. The second main structure support adopts an arched steel frame support, and an expansion shell anchor is installed at the arch top of each arch to enhance protection. During excavation, the excavation is carried out in cycles of no more than two arch frames. After the second main structure support is completed and the monitoring and measurement data of this part is stable, the temporary support is removed to ensure the stability of the initial support structure, effectively improve construction safety, and protect the personal safety of construction personnel.

[0013] More preferably, in step B, the temporary support is first removed manually at the connection between the temporary support and the main structure support, and the connection is broken. Only after the connection is broken can the lower half of the temporary support be removed mechanically. The removal method is simple and quick, and the temporary support can be removed quickly without affecting the stability of the initial support.

[0014] More preferably, in step B, the temporary lattice columns are arranged longitudinally at intervals of 15m to 20m to ensure that the temporary support is in place. The temporary lattice columns are made of 480X300X10 steel plates as gusset plates and welded with 200X20 angle steel, which makes the structure stable.

[0015] Further preferably, in step C, a high-powered excavator is used to excavate the middle step. The cross-section of the core soil of the middle step is trapezoidal, and the side walls on both sides slope outward to form a slope with a width of not less than 3m, ensuring sufficient working space and preventing landslides at the corners of the left and right guide tunnels of the middle step after the core soil of the middle step is excavated, which could threaten the lives of construction workers and affect the construction progress. After the core soil of the middle step is excavated to meet the working space, the left and right guide tunnels of the middle step are excavated in sequence. The simultaneous excavation of the left and right guide tunnels effectively improves the construction progress and saves time and costs. It also ensures that the working faces of the core soil of the middle step, the left guide tunnel, and the right guide tunnel are staggered by more than 5m during the excavation process, effectively ensuring construction safety and preventing the overall instability of the guide tunnels caused by the two working faces being too close together.

[0016] A further preferred embodiment is that, in step C, the temporary lattice columns are spliced ​​in sections using flanges and bolts to ensure vertical stability and facilitate convenient and quick assembly and disassembly of the temporary lattice columns.

[0017] Further preferably, in step D, a high-powered excavator is used to excavate the lower step. The core soil of the lower step has a trapezoidal cross-section, and the side walls on both sides slope outward to form a slope with a width of not less than 3m. This ensures sufficient working space and prevents landslides from occurring at the corners of the left and right guide tunnels of the lower step after the core soil is excavated, which could threaten the lives of construction workers and affect the construction progress. After the core soil of the lower step is excavated to meet the working space requirements, the left and right guide tunnels of the lower step are excavated sequentially. The simultaneous excavation of the left and right guide tunnels effectively improves the construction progress and saves time and costs. It also ensures that the working faces of the core soil of the lower step, the left guide tunnel, and the right guide tunnel are staggered by more than 5m during the excavation process, effectively ensuring construction safety and preventing the overall instability of the guide tunnels caused by the two working faces being too close together.

[0018] More preferably, in step E, the secondary lining concrete is poured after the invert arch is constructed for a length of not less than 30m, in accordance with the invert arch construction specifications. The excavation speed is based on the invert arch pouring speed, and the safe step distance between the upper, middle, and lower steps is strictly controlled at 7.5m, and the safe step distance between the invert arch and the tunnel face is 50m, in accordance with the safety standards for pilot tunnel construction.

[0019] A further preferred embodiment is that, in step E, when the invert arch is poured to a depth of 0.8m to 1.2m from the temporary lattice column, the temporary lattice column is dismantled using a steel reinforcement platform in conjunction with a self-propelled lifting platform, ensuring that the dismantling of the temporary lattice column does not interfere with the invert arch pouring.

[0020] The beneficial effects of this invention are:

[0021] (1) First, excavate the left and right guide tunnels of the upper step, then construct the main structure support one and temporary support of the left and right guide tunnels of the upper step, excavate the core soil of the upper step, construct the main structure support two connected to the main structure support one, and set up monitoring and measurement points at the arch top. Finally, remove the temporary support and replace it with a temporary grid column. The initial support of the upper step can be closed into a ring in advance, which effectively enhances the overall stability of the initial support structure under stress, improves construction safety, forms a large space excavation working face, facilitates the excavation of the next layer of steps, effectively shortens the construction period, and saves time and costs.

[0022] (2) By adopting a layered excavation method (upper, middle, and lower), the safety risks associated with excavating core soil exceeding 20m in height and dismantling temporary supports are avoided. This method allows for the rapid formation of a continuous construction surface for the initial support, invert arch, and lining. Both the middle and lower steps adopt the sequence of excavating the core soil first, followed by the excavation of the left and right guide tunnels. The excavation of the core soil provides a working surface for the excavation of the left and right guide tunnels, eliminating the need for temporary supports. This effectively reduces project and construction costs, improves the overall efficiency of the station, and enables the station to quickly meet the requirements for TBM passage, shortening the construction period and reducing costs.

[0023] (3) The steps formed by the upper, middle and lower steps can provide a working face for the next cycle of upper, middle and lower step excavation, and can simultaneously carry out the construction of the invert arch and the next cycle of upper, middle and lower step excavation, ensuring construction quality while speeding up the construction progress.

[0024] (4) Temporary lattice columns are set at intervals along the longitudinal direction of the tunnel to fully ensure the stability of the tunnel during the excavation process and avoid the situation where insufficient support leads to collapse, thereby endangering the personal safety of construction personnel. The temporary lattice columns are flexible and can be set at the bottom of the core soil of the upper step, the middle step, and the lower step, fully ensuring the stability of the upper, middle, and lower steps.

[0025] In summary, it features safety and reliability, ease of operation and implementation, high construction quality, fast construction progress, reduced project cost, and reduced construction expenses. Attached Figure Description

[0026] Figure 1 A schematic diagram of the cross-section after excavating the left and right guide tunnels of the upper step.

[0027] Figure 2 for Figure 1 Top view.

[0028] Figure 3 A schematic diagram of the cross-section of the core soil for excavating the upper step.

[0029] Figure 4 for Figure 3 Top view.

[0030] Figure 5 This is a schematic diagram of the cross-section after the step is excavated.

[0031] Figure 6 for Figure 5 Top view.

[0032] Figure 7 This is a schematic diagram of the cross-section after the lower step has been excavated.

[0033] Figure 8 for Figure 7 Top view.

[0034] Figure 9 This is a top view of the inverted arch construction.

[0035] Figure 10 This is a schematic diagram of the temporary lattice columns, inverted arches, secondary lining, and initial support flow operation elevation.

[0036] Figure 11 A schematic diagram of the structure of a customized excavation equipment for the double-sided guide tunnel of a shallow-buried station with an ultra-large cross-section in the city.

[0037] Figure 12 for Figure 11 The front view. Detailed Implementation

[0038] The present invention will be further described below with reference to the embodiments and accompanying drawings:

[0039] Combination Figure 1 — Figure 12 As shown, an improved construction method for a shallow-buried urban railway station with a large cross-section is proposed, which divides the pilot tunnel to be excavated into an upper step, a middle step, and a lower step. The specific implementation steps are as follows:

[0040] Step A: Excavate the left and right guide tunnels of the upper step; excavate the left guide tunnel 1 of the upper step near the left side wall of the guide tunnel and the right guide tunnel 2 of the upper step near the right side wall of the guide tunnel in sequence, and then construct the main structure support 10 and temporary support 11 for the left guide tunnel 1 and the right guide tunnel 2 of the upper step.

[0041] In step A, excavation is carried out using customized excavation equipment. The customized excavation equipment is a 420-type excavator with a single-head drill bit and the boom shortened to 2.9m and the extension boom shortened to 3.65m. During excavation, the working faces of the left guide tunnel 1 and the right guide tunnel 2 of the upper bench are staggered by a safe distance of more than 5m. The main structure support 10 uses I-beams to form an arch frame, and expansion shell anchors are installed at the top of each arch frame. After excavation, the left guide tunnel 1 and the right guide tunnel 2 of the upper bench can penetrate the guide tunnels on both side walls.

[0042] Step B: Excavate the core soil 3 of the upper bench; After excavating the core soil 3 of the upper bench, construct the second main structure support 3a connected to the main structure support 10 at the top of the arch of the excavated core soil 3 of the upper bench, and set up monitoring and measurement points at the arch. Finally, remove the temporary support 11 and set up temporary lattice columns 12 to replace the excavated core soil 3 of the upper bench to temporarily support the tunnel arch. The temporary lattice columns 12 are set at intervals along the longitudinal direction of the tunnel.

[0043] In step B, the length of the core soil 3 of the upper step is 80m. During the excavation, a microseismic monitoring system is used for real-time monitoring. The main structure support 2 3a is supported by an arched steel frame. Expansion shell anchors are installed at the arch top of each arch frame to enhance protection. During excavation, the excavation advance is cyclical, not exceeding two arch frames. After the main structure support 2 3a is completed and the monitoring and measurement data of this part is stable, the temporary support 11 is removed.

[0044] In step B, the temporary support 11 is first removed manually at the connection between the temporary support 11 and the main structure support 10. Only after the connection is broken can the lower half of the temporary support 11 be removed mechanically.

[0045] In step B, the temporary lattice columns 12 are arranged longitudinally at intervals of 15m to 20m. The temporary lattice columns 12 are made of 480X300X10 steel plates as gusset plates and welded with 200X20 angle steel.

[0046] Step C: Excavate the middle bench; First, excavate the middle bench core soil 4, which is directly opposite the upper bench core soil 3, to form a trench. The excavation length of the middle bench core soil 4 is less than that of the upper bench core soil 3. The temporary lattice columns 12 encountered during the excavation of the middle bench core soil 4 are extended to the bottom of the middle bench by splicing, so as to continue to temporarily support the tunnel arch. Then, the left guide tunnel 5 and the right guide tunnel 6 of the middle bench, located on both sides of the middle bench core soil 4, are excavated in sequence. Finally, the initial support is constructed. After excavation, the middle bench can form a bench with the upper bench.

[0047] In step C, a high-powered excavator is used to excavate the middle bench. The cross-section of the core soil 4 of the middle bench is trapezoidal, and the side walls on both sides slope outward to form a slope with a width of not less than 3m. After the core soil 4 of the middle bench is excavated to meet the working space, the left guide tunnel 5 and the right guide tunnel 6 of the middle bench are excavated in sequence, and the working faces of the core soil 4, the left guide tunnel 5 and the right guide tunnel 6 of the middle bench are staggered by a safe distance of more than 5m between each other during the excavation process.

[0048] In step C, the temporary lattice column 12 is spliced ​​in sections using flanges and bolts.

[0049] Step D: Excavate the lower bench; excavate the lower bench core soil 7 located directly below the middle bench core soil 4. The excavation length of the lower bench core soil 7 is less than that of the middle bench core soil 5. Extend the temporary lattice columns 12 encountered during the excavation of the lower bench core soil 7 to the bottom of the lower bench by splicing, so as to continue to temporarily support the tunnel arch. Then, excavate the lower bench left guide tunnel 8 and lower bench right guide tunnel 9 located on both sides of the lower bench core soil 7. The excavation lengths of the lower bench left guide tunnel 8 and lower bench right guide tunnel 9 are less than those of the middle bench left guide tunnel 5 and middle bench right guide tunnel 6, respectively. Finally, perform initial support. The excavated lower bench can form a step with the middle bench.

[0050] In step D, a high-powered excavator is used to excavate the lower bench. The cross-section of the core soil 7 of the lower bench is trapezoidal, and the side walls on both sides slope outward to form a slope with a width of not less than 3m. After the core soil 7 of the lower bench is excavated to meet the working space, the left guide tunnel 8 and the right guide tunnel 9 of the lower bench are excavated in sequence, and the working faces of the core soil 7, the left guide tunnel 8, and the right guide tunnel 9 of the lower bench are staggered by a safe distance of more than 5m between each other during the excavation process.

[0051] Step E: Construct the invert arch. When constructing the invert arch, the temporary lattice columns 12 within the invert arch pouring area need to be removed from top to bottom. Then, the secondary lining concrete is poured. At the same time, according to the steps formed by the upper, middle and lower steps, the excavation continues along the front and back direction of the guide tunnel in the excavation sequence of the above steps.

[0052] In step E, after the invert arch is constructed for a length of not less than 30m, the secondary lining concrete is poured. The excavation speed is based on the invert arch pouring speed, and the safe step distance between the upper, middle and lower steps is strictly controlled at 7.5m, and the safe step distance between the invert arch and the working face is 50m.

[0053] In step E, when the invert arch is poured to the range of 120.8m to 1.2m from the temporary lattice column 12, the temporary lattice column 12 is dismantled by using a steel reinforcement platform in conjunction with a self-propelled lifting platform.

[0054] Figure 11 , Figure 12 A schematic diagram of the customized excavation equipment structure for the double-sided guide tunnel of a shallow-buried urban station with an ultra-large cross-section is shown.

[0055] The customized excavation equipment for the double-sided guide tunnel of the shallow buried station with super large cross section in the city is mainly composed of a drive base 25, on which a new short rod excavation structure is installed.

[0056] The new short-bar excavator structure includes: several drive wheels 26, a pair of tracks 27, an engine box 28, a cab 29, a rotating hinge 30, a boom 31, an extension arm 32, a blast head 33, a blasting rod 34, a hydraulic drive assembly, and a structural reinforcement assembly.

[0057] Several drive wheels 26 are mounted on the output end of the drive base 25, a pair of tracks 27 are mounted on the drive wheels 26, an engine box 28 is mounted on the drive base 25 and connected to the drive base 25, a cab is mounted on the front right side of the drive base 25, a rotating hinge 30 is mounted on the drive base 25, the lower end of the boom 31 is mounted on the rotating hinge 30, one end of the extension arm 32 is mounted on the upper end of the boom 31, the gun head 33 is mounted on the front end of the extension arm 32, the ramming rod is mounted on the gun head 33, a hydraulic drive assembly is mounted on the drive base 25, the boom 31, the extension arm 32 and the gun head 33, and a structural reinforcement assembly is mounted on the boom 31 and the extension arm 32.

[0058] It should be noted that when using the new short-bar excavation structure, the engine box 28 installed on the drive base 25 starts to provide driving power. The movement is achieved by the rotation of several transmission drive wheels 26 installed on the drive base 25 in conjunction with the track 27. After moving to the excavation position, the hydraulic drive assembly starts to drive the boom 31, extension arm 32 and blast head 33 to adjust. The excavation is carried out by the blasting rod 34 installed on the blast head 33.

[0059] An exhaust pipe 35 for exhaust is installed on the engine housing 28.

[0060] The boom 31 is 2.9m long and the cantilever 32 is 3.65m long. Their function is to be more suitable for the excavation of the inside corner and perimeter of the tunnel face, which greatly reduces the overall excavation time.

[0061] The drill bit 34 is a single-head drill bit, and its function is to reduce disturbance to the unexcavated soil and reduce the risk of rockfall at the working face.

[0062] The drive assembly includes: boom cylinder 36, first connecting mounting bracket 13, first mounting pin 14, second connecting mounting bracket 15, boom extension cylinder 16, second mounting pin 17, third connecting mounting bracket 18, adjusting cylinder 19, and third mounting pin 20.

[0063] The lower end of the boom cylinder 36 is movably mounted on the drive base 25. The first connecting mounting bracket 13 is mounted on the lower wall of the boom 31. The upper end of the boom cylinder 36 is mounted on the first connecting mounting bracket 13 via the first mounting pin 14. The second connecting mounting bracket 15 is mounted in the middle of the upper wall of the boom 31. The rear end of the extension cylinder 16 is mounted on the second connecting mounting bracket 15 via the second mounting pin 17. The extension cylinder 16 is mounted at the rear end of the extension boom 32. The third connecting mounting bracket 18 is mounted on the upper wall of the extension boom 32. One end of the adjusting cylinder 19 is mounted on the third connecting mounting bracket 18 via the third mounting pin 20. The other end of the adjusting cylinder 19 is mounted on the adjusting end of the gun head 33.

[0064] It should be noted that when using the hydraulic drive assembly, the boom cylinder 36 mounted on the drive base 25 extends its output end and drives the boom 31 to be raised around the rotating hinge 30 to a certain height via the first connecting mounting bracket 13. The extension cylinder 16 mounted on the second connecting mounting bracket 15 extends its output end and drives the extension arm 32 mounted on the boom 31 to adjust its angle. The digging angle of the blasting head 33 mounted on the extension arm 32 can be adjusted by extending and retracting the output end of the adjusting cylinder 19 mounted on the extension arm 32 via the third connecting mounting bracket 18.

[0065] The structural reinforcement assembly includes: a pair of structural reinforcement frames 21, a number of first reinforcement rods 22, two pairs of reinforcement ribs 23, and a number of second reinforcement rods 24;

[0066] A pair of structural reinforcing frames 21 are installed on the front and rear walls of the boom 31, a number of first reinforcing rods 22 are installed inside the pair of structural reinforcing frames 21, two pairs of reinforcing ribs 23 are installed on the upper and lower positions of the front and rear walls of the extension arm 32, and a number of second reinforcing rods 24 are installed in the middle position of the two pairs of reinforcing ribs 23.

[0067] It should be noted that when using the structural reinforcement components, the structural reinforcement frame 21 installed on both sides of the boom 31 increases the support strength of the boom, and the several first reinforcement rods 22 installed on the structural reinforcement frame 21 distribute the force evenly to ensure stable support. The two pairs of reinforcing ribs 23 installed on the extension boom 32, together with several second reinforcement rods 24, increase the support strength of the extension boom 32.

Claims

1. An improved double-side-wall pilot tunnel construction method for a city super-large cross-section shallow-buried station, wherein a double-side-wall pilot tunnel to be excavated is divided into an upper step, a middle step and a lower step, characterized in that, It comprises the following steps: Step A, excavate the upper step left and right guide holes; excavate the upper step left guide hole (1) close to the left side wall of the guide hole and the upper step right guide hole (2) close to the right side wall of the guide hole in turn, then make the main structure support one (10) and the temporary support (11) of the upper step left guide hole (1) and the upper step right guide hole (2); Step B, excavate the upper step core soil (3); after excavating the upper step core soil (3), then construct the main structure support two (3a) connected with the main structure support one (10) at the arch top of the excavated upper step core soil (3), and arrange monitoring and measuring points at the arch top, finally remove the temporary support (11) and set the temporary lattice column (12) to replace the excavated upper step core soil (3) to temporarily support the tunnel arch top, the temporary lattice column (12) is arranged along the longitudinal direction of the tunnel; Step C, excavate the middle step; first excavate the middle step core soil (4) opposite to the upper step core soil (3) to form a draw slot, the excavation length of the middle step core soil (4) is less than that of the upper step core soil (3), the temporary lattice column (12) encountered during the excavation of the middle step core soil (4) is extended to the bottom of the middle step by splicing, so as to continue to temporarily support the tunnel arch top, then excavate the middle step left guide hole (5) and the middle step right guide hole (6) located on both sides of the middle step core soil (4) in turn, and finally make the initial support, the excavated middle step can form a step with the upper step; Step D, excavate the lower step; excavate the lower step core soil (7) directly below the middle step core soil (4), the excavation length of the lower step core soil (7) is less than that of the middle step core soil (4), the temporary lattice column (12) encountered during the excavation of the lower step core soil (7) is extended to the bottom of the lower step by splicing, so as to continue to temporarily support the tunnel arch top, then excavate the lower step left guide hole (8) and the lower step right guide hole (9) located on both sides of the lower step core soil (7), and the excavation lengths of the lower step left guide hole (8) and the lower step right guide hole (9) are respectively less than those of the middle step left guide hole (5) and the middle step right guide hole (6), finally make the initial support, the excavated lower step can form a step with the middle step; Step E, perform the inverted arch construction, the inverted arch is cast in one mold, the temporary lattice column (12) in the inverted arch pouring range needs to be removed from top to bottom, then the secondary lining concrete is poured, and meanwhile the steps formed by the upper step, the middle step and the lower step continue to be excavated and advanced along the front and back directions of the guide hole according to the excavation sequence of the above steps; In step C, the middle step is excavated by using a high-power hook machine device, the cross section of the middle step core soil (4) is trapezoidal, the side walls on both sides are inclined outward to form a slope surface with a width not less than 3m, after the middle step core soil (4) is excavated to meet the operation space, the middle step left guide hole (5) and the middle step right guide hole (6) are excavated in turn, and the safety distance between the excavation surfaces of the middle step core soil (4), the middle step left guide hole (5) and the middle step right guide hole (6) is more than 5m.

2. The improved double-side-wall guided hole construction method of urban super-large cross-section shallow-buried stations according to claim 1, characterized in that: In the step A, the excavation is performed by a customized excavation equipment, which is a 420 excavator with a single-head drill rod and shortened boom to 2.9 m and shortened stick to 3.65 m, and the upper step left pilot hole (1) and the upper step right pilot hole (2) are staggered by more than 5 m safety distance, the main structure support one (10) is formed by an I-beam arch, and an expansion shell anchor is arranged at the top of each arch, and the upper step left pilot hole (1) and the upper step right pilot hole (2) can penetrate the double side wall pilot holes.

3. The improved double-sidewall pilot tunnel construction method of urban super-large cross-section shallow-buried stations according to claim 1, characterized in that: In the step B, the upper step core soil (3) is 80 m long, and a microseismic monitoring system is provided during the excavation for real-time monitoring, the main structure support two (3a) is supported by an arch top steel frame, and an expansion shell anchor is arranged at the top of each arch for reinforcement, and the excavation is performed in a cycle of not more than two arches, and after the main structure support two (3a) is completed, the monitoring and measurement data of this part are stable, and then the temporary support (11) is removed.

4. The improved double-side-wall guided hole construction method of urban super-large cross-section shallow-buried stations according to claim 3, characterized in that: In the step B, the temporary support (11) is disconnected by manually chiseling and disconnecting the connection between the temporary support (11) and the main structure support one (10), and then the lower half of the temporary support (11) is removed by machinery.

5. The improved double-sidewall pilot tunnel construction method of urban super-large cross-section shallow-buried stations according to claim 4, characterized in that: In the step B, the temporary lattice column (12) is arranged longitudinally at intervals of 15-20 m, and the temporary lattice column (12) is made of 480X300X10 steel plates as a patch and 200X20 angle steel welded together.

6. The improved double-sidewall guided hole construction method of urban super-large cross-section shallow-buried stations of claim 1, characterized in that: In the step C, the temporary lattice column (12) is segmented and spliced by flanges and bolts.

7. The improved double-sidewall guided hole construction method of urban super-large cross-section shallow-buried stations of claim 1, characterized in that: In the step D, the lower step is excavated by a high-power hook machine, the lower step core soil (7) has a trapezoidal cross section, the side walls are inclined outward to form a slope with a width of not less than 3 m, and after the lower step core soil (7) is excavated to meet the operation space, the lower step left pilot hole (8) and the lower step right pilot hole (9) are excavated in sequence, and the excavation process is ensured to be staggered by more than 5 m safety distance between the lower step core soil (7), the lower step left pilot hole (8) and the lower step right pilot hole (9).

8. The improved double-sidewall guided hole construction method of urban super-large cross-section shallow-buried stations of claim 1, characterized in that: In the step E, the invert is constructed for more than 30 m, the secondary lining concrete is poured, the excavation speed is determined according to the invert pouring speed, and the safety step distance between the upper step, the middle step and the lower step is strictly controlled to be 7.5 m, and the safety step distance between the invert and the working face is 50 m.

9. The improved double-sidewall pilot tunnel construction method of urban super-large cross-section shallow-buried stations according to claim 8, characterized in that: In the step E, when the invert is poured to the range of 0.8-1.2 m of the temporary lattice column (12), the temporary lattice column (12) is removed by a steel reinforcement rack combined with a self-propelled lifting platform.

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