Construction method for removing rock pillar in super-large section hard rock tunnel in deep underground space

Abstract

The invention provides a construction method for removing a rock pillar in a deep underground space super-large section hard rock tunnel, which comprises the following steps of: firstly, establishing a tunnel three-dimensional model by utilizing finite element software Midas GTS, determining a safety distance from a secondary lining to a middle rock pillar in a station excavation process through simulation analysis, dividing a tunnel section into an upper step, a middle step and a lower step according to height, and constructing a tunnel model; each step is further divided into a left pilot tunnel, a middle pilot tunnel and a right pilot tunnel. The construction process comprises the steps of top lifting, main body tunnel upper step left and right pilot tunnel excavation and support, middle step left and right pilot tunnel excavation and support, upper step middle pilot tunnel excavation and support, middle step middle pilot tunnel excavation and support, lower step left and right pilot tunnel excavation and support, lower step middle pilot tunnel excavation and support and inverted arch and arch wall lining construction. According to the construction method, the pilot tunnel construction sequence is optimized, space is provided for mechanical excavation, the problem that the upper step and the middle step of the core rock pillar cannot be mechanically trimmed is solved, and the construction efficiency is improved. Manual and automatic monitoring is adopted in the whole process to ensure tunnel safety and stability. The construction risk is effectively reduced, carbon emission and dust pollution are reduced, the method is suitable for hard rock geological tunnel construction with good self-stability, and remarkable social benefits are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of subway tunnel construction and relates to a construction method for removing rock pillars in a super-large-section hard rock tunnel in a deep underground space. Background Art

[0002] With the rapid development of my country's economic construction and urban construction, the number of cars per capita in cities continues to increase, urban traffic pressure has increased dramatically, and urban traffic congestion has become increasingly prominent in major cities. In order to alleviate urban traffic pressure, urban rail transit is being built rapidly and comprehensively. Subway stations are usually located in the core areas of cities. The traditional open-cut method has a great impact on surface traffic and the environment. The open-cut method has gradually failed to adapt to station construction in complex environments. In addition, the open-cut method is not suitable for lines with greater burial depths, resulting in an increase in underground excavation stations year by year, and various types of shallow buried underground excavation large-section station tunnels are emerging in an endless stream.

[0003] Conventional tunnel monitoring is a manual monitoring method, which has the main shortcomings of intermittent, human operation, and subjective evaluation of monitoring data. By introducing automated monitoring methods for data collection, the timeliness and reliability of monitoring data are ensured, providing reliable support for the safety of large-section tunnels; the construction methods of large-section dark-cut stations mainly include double-side wall pilot pit method, middle partition wall method, and cross middle partition wall method. In particular, the double-side wall pilot pit method is often used in the excavation construction of shallow buried dark-cut large-span subway tunnels. Its advantage is that it can effectively control the settlement of the surface and arch crown. The disadvantages are that the construction process conversion times are many and cumbersome, the construction speed is slow, the construction period is long, and the construction cost is high. Summary of the invention

[0004] In view of this, the purpose of the present invention is to solve the above-mentioned problem and to propose a construction method for removing rock pillars in a hard rock tunnel with a super-large cross-section in a deep underground space.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A construction method for removing the middle rock pillar in a deep underground space ultra-large cross-section hard rock tunnel. The method uses the finite element software Midas GTS to establish a three-dimensional finite element model to simulate the mechanical characteristics of the destruction or plastic flow of geological materials when reaching the strength limit or yield limit, analyze the progressive failure instability and simulate large deformation, determine the safe distance from the second lining to the middle rock pillar during the excavation of the main body of the station, and divide the tunnel section into three steps: upper step, middle step, and lower step according to the one-time excavation height. Each step is divided into three pilot tunnels on the left, middle, and right sides.

[0007] Then, we will enter through the station construction passage and carry out tunnel top construction; after the top construction is completed, the tunnel will be constructed by double-side wall pilot pit method, and the specific process flow is: top construction → excavation and support of pilot tunnels on the left and right sides of the upper step of the main tunnel → excavation and support of pilot tunnels on the left and right sides of the middle step of the main tunnel → excavation and support of the middle pilot tunnel on the upper step of the main tunnel → excavation and support of the middle pilot tunnel on the middle step of the main tunnel → excavation and support of the left and right pilot tunnels on the lower step of the main tunnel → excavation and support of the middle pilot tunnel on the lower step of the main tunnel → invert and filling construction → arch wall lining structure construction.

[0008] Furthermore, in the top-lifting construction step, the main tunnel of the station is excavated and supported. The station construction channel is entered from the top, and mechanical excavation is carried out using an excavator. The end of the construction channel is gradually expanded and raised within 5m. Three portal steel frames are closely arranged at the end of the construction channel, and a whole steel plate and a second-layer steel frame support steel plate are set on the top of the steel frame;

[0009] The cantilever section is excavated according to the two-step method. First, the upper step is excavated and a portal steel frame is installed. The excavation height of the upper step is ≤8m. The excavation height of the upper step is controlled according to the effective working height of the breaker. After the excavation is completed, the portal steel frame and other support construction are installed. The single-cycle excavation advance is the spacing of 2 steel frames. After the excavation and support of the upper step is completed, the second-layer annular steel frame is installed; then the excavation and support of the lower step of the cantilever section channel is carried out.

[0010] Furthermore, in the step of excavating and supporting the guide tunnels on the left and right sides of the upper steps of the main tunnel, the specific construction process is as follows:

[0011] (1) After the cantilever construction is completed, the cantilever primary support structure at the right guide tunnel of the step on the large mileage direction of the station is first removed, and the excavation and support of the right guide tunnel of the step on the large mileage direction is carried out; after the excavation and support of the right guide tunnel of the step on the large mileage direction is completed for 15m, the cantilever primary support structure at the left guide tunnel of the step on the small mileage direction is removed, and the excavation and support of the left guide tunnel of the step on the small mileage direction is carried out;

[0012] (2) After the excavation and support of the left pilot tunnel on the small mileage upper step is completed for about 15m, the primary support structure of the top of the right pilot tunnel on the small mileage upper step is removed, and the excavation and support of the right pilot tunnel on the small mileage upper step is carried out;

[0013] (3) After the excavation and support of the right pilot tunnel on the upper step of the small mileage is completed for 15 m, the excavation and support of the left pilot tunnel on the upper step in the direction of the large mileage is carried out; then the excavation and support of the four pilot tunnels in the directions of the large mileage and the small mileage are carried out simultaneously until the excavation and support of the left and right pilot tunnels on the upper step are completed;

[0014] (4) When the initial support structure of the canopy section is removed in each guide tunnel of the upper step, local slag padding is carried out in the canopy section channel to allow the passage of excavators and vehicles.

[0015] Furthermore, in the step of excavating and supporting the guide tunnels on the left and right sides of the steps in the main tunnel, the specific construction process is as follows:

[0016] (1) After the left guide tunnel of the upper step is excavated and supported to the ends of the large and small mileages, the left guide tunnel of the middle step is excavated and supported from the branch passage to both ends of the station;

[0017] (2) After the right guide tunnel of the upper step is excavated and supported to the ends of the large and small mileages, the right guide tunnel of the middle step is excavated and supported from the branch passage to both ends of the station;

[0018] (3) To ensure the access conditions for vehicles, a slope reduction construction with a slope of 19% was carried out near the construction channel. After the slope was reduced to the bottom elevation of the middle step, a pilot tunnel was excavated and supported toward the end of the station until the construction of the middle step was completed.

[0019] Furthermore, in the step of excavating and supporting the intermediate guide tunnel on the upper step of the main tunnel, the specific construction process is as follows:

[0020] (1) Excavation and construction of the long-mileage and short-mileage ends of the station, transportation of slag and materials, and construction of the interface position of the station's auxiliary structures. Under the condition that the left and right pilot tunnels of the station's upper steps are connected, the middle pilot tunnel of the upper steps within 10m of the station end, auxiliary structure and station structure position is excavated in advance;

[0021] (2) The remaining upper step middle guide tunnels shall be excavated and supported from the large mileage end and the small mileage end of the station to the middle part of the station; the excavation and support advance of each cycle shall be controlled to be ≤2.5m, and support construction shall be carried out in a timely manner after the excavation is completed. At the same time, the safe step distance of the rock column of the upper step middle guide tunnel shall be controlled to be ≤60m;

[0022] (3) When the middle rock column is removed, the arch is repaired and trimmed by mechanical construction, and the right guide hole of the middle step is partially padded with slag to meet the requirements for the passage of excavator equipment.

[0023] Furthermore, in the excavation and support steps of the middle guide tunnel in the middle step of the main tunnel, the middle guide tunnel in the middle step is excavated immediately following the middle guide tunnel in the upper step. The middle partition wall is first demolished, and then the middle rock column is excavated. The excavation cycle advance is not more than 3.5m.

[0024] Furthermore, when excavating the lower step of the main tunnel, the left guide tunnel of the lower step is excavated and supported first, followed by the right guide tunnel of the lower step, and finally the middle guide tunnel of the lower step is removed. The excavation cycle advance is not more than 3.5m.

[0025] Furthermore, the settlement of the tunnel vault, the convergence of clearance, and the settlement of surrounding pipelines are manually monitored throughout the construction process. At the same time, steel stress gauges, earth pressure boxes, wireless data acquisition instruments, data automation processing and early warning platforms are used to dynamically monitor the entire process of tunnel construction. All-round, three-dimensional and real-time monitoring of the initial support stress of the tunnel and the surrounding rock pressure is carried out, and early warning information is automatically pushed to personal mobile phones to ensure the timeliness and accuracy of the monitoring data and achieve a visual effect of stress monitoring. Manual monitoring and automatic monitoring are carried out in parallel to ensure that the initial support of the tunnel is safe, stable and controllable.

[0026] The beneficial effects of the present invention are:

[0027] 1. The present invention optimizes the construction sequence of each pilot tunnel of the traditional double-side wall pilot tunnel method, provides a good working space for mechanical excavation and trimming, avoids the problem that the left and right pilot tunnels of the traditional method are completely bottomed out, and the upper step and middle step rock columns of the core rock column cannot be mechanically trimmed and the arch excavated, thereby reducing the safety risk in the construction process; in Chongqing, the safe step distance of shallow buried and dark-excavated large-section tunnels is optimized from 45m to 55m, which solves the problem that the excavation of the station tunnel and the invert and second lining cannot be constructed simultaneously due to insufficient distance and insufficient operating space between the middle and lower steps of the tunnel and the second lining of the station, thereby improving the construction efficiency; during the construction process, monitoring items such as surrounding buildings, tunnel vault settlement, and clearance convergence are monitored and measured, the monitoring data is stable, the tunnel construction is safe and controllable, and the safety of the tunnel itself and the surrounding environment is effectively guaranteed, which provides reference for similar projects in the future and has obvious social benefits.

[0028] 2. After the excavation of the left and right guide tunnels in the middle step is completed, the left or right guide tunnel in the middle step is padded with slag to remove the middle guide tunnel in the upper step. At the same time, except for the left and right guide tunnels in the upper step which are excavated mechanically, the other guide tunnels are excavated by fine blasting. This effectively reduces the utilization rate of large-scale mechanical equipment, improves the working environment in confined spaces, improves the air quality of the tunnel, and reduces carbon emissions and dust pollution from large-scale mechanical equipment.

[0029] 3. The present invention is suitable for the excavation construction of shallow buried and dark-dig large-section subway tunnels under Grade IV hard rock geological conditions with good integrity and self-stability.

[0030] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0032] Figure 1 It is a schematic diagram of the process of the construction method for removing rock pillars in a super-large-section hard rock tunnel in a medium-deep underground space according to the present invention.

[0033] Figure 2 It is a schematic diagram of the construction sequence of the double-side wall pilot pit method in the present invention.

[0034] Figure 3 This is a schematic diagram of the tunnel roof construction process.

[0035] Figure 4 This is a schematic diagram of the construction process of the left and right guide tunnels for the upper steps.

[0036] Figure 5 This is a schematic diagram of the construction process of the left and right guide tunnels on the middle step.

[0037] Figure 6 This is a schematic diagram of the construction process of the middle guide tunnel in the middle step. DETAILED DESCRIPTION

[0038] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0039] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0040] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0041] See also Figures 1 to 6 It is a construction method for removing the middle rock pillar in a deep underground space ultra-large cross-section hard rock tunnel. The finite element software Midas GTS is used to establish a three-dimensional finite element model to simulate the mechanical characteristics of the destruction or plastic flow of geological materials when reaching the strength limit or yield limit of the large-section tunnel, analyze the progressive failure instability and simulate large deformation, determine the safe distance from the second lining to the middle rock pillar during the excavation of the main body of the station, and divide the tunnel section into three steps: upper step, middle step, and lower step according to the one-time excavation height. Each step is divided into three guide tunnels on the left, middle, and right sides.

[0042] Then, we will enter through the station construction passage and carry out tunnel top construction; after the top construction is completed, the tunnel will be constructed by double-side wall pilot pit method, and the specific process flow is: top construction → excavation and support of pilot tunnels on the left and right sides of the upper step of the main tunnel → excavation and support of pilot tunnels on the left and right sides of the middle step of the main tunnel → excavation and support of the middle pilot tunnel on the upper step of the main tunnel → excavation and support of the middle pilot tunnel on the middle step of the main tunnel → excavation and support of the left and right pilot tunnels on the lower step of the main tunnel → excavation and support of the middle pilot tunnel on the lower step of the main tunnel → invert and filling construction → arch wall lining structure construction.

[0043] In the top-lift construction step, the main tunnel of the station is excavated and supported. The station construction channel is entered from the top, and mechanical excavation is carried out using an excavator. The end of the construction channel is gradually expanded and raised within 5m. Three portal steel frames are closely arranged at the end of the construction channel. A whole steel plate and a second-layer steel frame support steel plate are set on the top of the steel frame.

[0044] The cantilever section is excavated according to the two-step method. First, the upper step is excavated and a portal steel frame is installed. The excavation height of the upper step is ≤8m. The excavation height of the upper step is controlled according to the effective working height of the breaker. After the excavation is completed, the portal steel frame and other support construction are installed. The single-cycle excavation advance is the spacing of 2 steel frames. After the excavation and support of the upper step is completed, the second-layer annular steel frame is installed; then the excavation and support of the lower step of the cantilever section channel is carried out.

[0045] Among them, in the steps of excavating and supporting the guide tunnels on the left and right sides of the upper steps of the main tunnel, the specific construction process is as follows:

[0046] (1) After the cantilever construction is completed, the cantilever primary support structure at the position of the No. 2 pilot tunnel in the direction of large mileage of the station shall be removed first, and the excavation and support of the No. 2 pilot tunnel in the direction of large mileage shall be carried out; after the excavation and support of the No. 2 pilot tunnel in the direction of large mileage is completed for 15m, the cantilever primary support structure at the position of the No. 1 pilot tunnel in the direction of small mileage shall be removed, and the excavation and support of the No. 1 pilot tunnel in the direction of small mileage shall be carried out;

[0047] (2) After the excavation and support of the small mileage No. 1 pilot tunnel is completed for about 15m, the primary support structure of the small mileage No. 2 pilot tunnel is removed and the excavation and support of the small mileage No. 2 pilot tunnel is carried out;

[0048] (3) After the excavation and support of the pilot tunnel No. ② in the small mileage direction is completed for 15m, the excavation and support of the pilot tunnel No. 1 in the large mileage direction is carried out; then the excavation and support of the four pilot tunnels in the large and small mileage directions are carried out simultaneously until the excavation and support of the left and right pilot tunnels on the upper step are completed;

[0049] (4) When the initial support structure of the canopy section is removed in each guide tunnel of the upper step, local slag padding is carried out in the canopy section channel to allow the passage of excavators and vehicles.

[0050] Among them, in the steps of excavating and supporting the guide tunnels on the left and right sides of the steps in the main tunnel, the specific construction process is as follows:

[0051] (1) After the station’s pilot tunnel No. 1 is excavated and supported to the ends of the large and small mileages, the pilot tunnel No. 3 is excavated and supported from the branch passage to both ends of the station;

[0052] (2) After the station’s pilot tunnel No. 2 is excavated and supported to the ends of the large and small mileages, the pilot tunnel No. 4 is excavated and supported from the branch passage to both ends of the station;

[0053] (3) To ensure the access conditions for vehicles, a slope reduction construction with a slope of 19% was carried out near the construction channel. After the slope was reduced to the bottom elevation of the middle step, a pilot tunnel was excavated and supported toward the end of the station until the construction of the middle step was completed.

[0054] Among them, in the steps of excavation and support of the intermediate guide tunnel on the upper step of the main tunnel, the specific construction process is as follows:

[0055] (1) Excavation and construction of the long-mileage and short-mileage ends of the station, transportation of slag and materials, and construction of the interface position of the station's auxiliary structures. Under the condition that the left and right pilot tunnels of the station's upper steps are connected, the middle pilot tunnel of the upper steps within 10m of the station end, auxiliary structure and station structure position is excavated in advance;

[0056] (2) The remaining upper step middle guide tunnels shall be excavated and supported from the large mileage end and the small mileage end of the station to the middle part of the station; the excavation and support advance of each cycle shall be controlled to be ≤2.5m, and support construction shall be carried out in a timely manner after the excavation is completed. At the same time, the safe step distance of the rock column of the upper step middle guide tunnel shall be controlled to be ≤60m;

[0057] (3) When the middle rock column is removed, the arch is repaired and repaired by mechanical construction, and the No. 4 guide tunnel is partially padded with slag to meet the requirements for the passage of excavator equipment.

[0058] Among them, in the excavation and support steps of the middle guide tunnel in the middle step of the main tunnel, the middle guide tunnel in the middle step is excavated immediately following the middle guide tunnel in the upper step. The middle partition wall is first demolished, and then the middle rock column is excavated. The excavation cycle advance is not more than 3.5m.

[0059] Among them, when excavating the lower step of the main tunnel, first carry out excavation and support of pilot tunnel No. 7, then carry out excavation and support of pilot tunnel No. 8, and finally break through pilot tunnel No. 9 of the lower step. The excavation cycle advance is not more than 3.5m.

[0060] During the entire construction process, the tunnel vault settlement, clearance convergence and surrounding pipeline settlement are monitored manually. At the same time, steel stress gauges, earth pressure boxes, wireless data acquisition instruments, data automation processing and early warning platforms are used to dynamically monitor the entire tunnel construction process. All-round, three-dimensional and real-time monitoring of the tunnel initial support stress and surrounding rock pressure is carried out, and early warning information is automatically pushed to personal mobile phones to ensure the timeliness and accuracy of monitoring data and achieve a visual effect of stress monitoring. Manual monitoring and automatic monitoring are carried out in parallel to ensure that the initial support of the tunnel is safe, stable and controllable.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A construction method for removing rock pillars in a deep underground space ultra-large cross-section hard rock tunnel, characterized by: By using the finite element software Midas GTS to establish a three-dimensional finite element model for the large-section tunnel, the mechanical characteristics of the destruction or plastic flow of geological materials when reaching the strength limit or yield limit are simulated, the progressive failure instability and large deformation simulation are analyzed, and the safe distance from the second lining to the middle rock column during the excavation of the main body of the station is determined. The tunnel section is divided into three steps: upper step, middle step, and lower step according to the one-time excavation height. Each step is divided into three pilot tunnels on the left, middle, and right sides. Then, we will enter through the station construction passage and carry out tunnel top construction; after the top construction is completed, the tunnel will be constructed by double-side wall pilot pit method, and the specific process flow is: top construction → excavation and support of pilot tunnels on the left and right sides of the upper step of the main tunnel → excavation and support of pilot tunnels on the left and right sides of the middle step of the main tunnel → excavation and support of the middle pilot tunnel on the upper step of the main tunnel → excavation and support of the middle pilot tunnel on the middle step of the main tunnel → excavation and support of the left and right pilot tunnels on the lower step of the main tunnel → excavation and support of the middle pilot tunnel on the lower step of the main tunnel → invert and filling construction → arch wall lining structure construction.

2. The construction method for removing rock pillars in a deep underground space ultra-large cross-section hard rock tunnel according to claim 1 is characterized by: In the top-lift construction step, the main tunnel of the station is excavated and supported. The station construction channel is entered from the top, and mechanical excavation is carried out using an excavator. The end of the construction channel is gradually expanded and raised within 5m. Three portal steel frames are closely arranged at the end of the construction channel. A whole steel plate and a second-layer steel frame support steel plate are set on the top of the steel frame. The cantilever section is excavated according to the two-step method. First, the upper step is excavated and a portal steel frame is installed. The excavation height of the upper step is ≤8m. The excavation height of the upper step is controlled according to the effective working height of the breaker. After the excavation is completed, the portal steel frame and other support construction are installed. The single-cycle excavation advance is the spacing of 2 steel frames. After the excavation and support of the upper step is completed, the second-layer annular steel frame is installed; then the excavation and support of the lower step of the cantilever section channel is carried out.

3. The construction method for removing rock pillars in a deep underground space ultra-large cross-section hard rock tunnel according to claim 1 is characterized in that: In the steps of excavating and supporting the guide tunnels on the left and right sides of the upper steps of the main tunnel, the specific construction process is as follows: (1) After the cantilever construction is completed, the cantilever primary support structure at the right guide tunnel of the step on the large mileage direction of the station is first removed, and the excavation and support of the right guide tunnel of the step on the large mileage direction is carried out; after the excavation and support of the right guide tunnel of the step on the large mileage direction is completed for 15m, the cantilever primary support structure at the left guide tunnel of the step on the small mileage direction is removed, and the excavation and support of the left guide tunnel of the step on the small mileage direction is carried out; (2) After the excavation and support of the left pilot tunnel on the small mileage upper step is completed for about 15m, the primary support structure of the top of the right pilot tunnel on the small mileage upper step is removed, and the excavation and support of the right pilot tunnel on the small mileage upper step is carried out; (3) After the excavation and support of the right pilot tunnel on the upper step of the small mileage is completed for 15 m, the excavation and support of the left pilot tunnel on the upper step in the direction of the large mileage is carried out; then the excavation and support of the four pilot tunnels in the directions of the large mileage and the small mileage are carried out simultaneously until the excavation and support of the left and right pilot tunnels on the upper step are completed; (4) When the initial support structure of the canopy section is removed in each guide tunnel of the upper step, local slag padding is carried out in the canopy section channel to allow the passage of excavators and vehicles.

4. The construction method for removing rock pillars in a deep underground space ultra-large cross-section hard rock tunnel according to claim 1 is characterized in that: In the steps of excavating and supporting the guide tunnels on the left and right sides of the steps in the main tunnel, the specific construction process is as follows: (1) After the left guide tunnel of the upper step is excavated and supported to the ends of the large and small mileages, the left guide tunnel of the middle step is excavated and supported from the branch passage to both ends of the station; (2) After the right guide tunnel of the upper step is excavated and supported to the ends of the large and small mileages, the right guide tunnel of the middle step is excavated and supported from the branch passage to both ends of the station; (3) To ensure the access conditions for vehicles, a slope reduction construction with a slope of 19% was carried out near the construction channel. After the slope was reduced to the bottom elevation of the middle step, a pilot tunnel was excavated and supported toward the end of the station until the construction of the middle step was completed.

5. The construction method for removing rock pillars in a deep underground space ultra-large cross-section hard rock tunnel according to claim 1 is characterized in that: In the steps of excavating and supporting the intermediate guide tunnel on the upper step of the main tunnel, the specific construction process is as follows: (1) Excavation and construction of the long-mileage and short-mileage ends of the station, transportation of slag and materials, and construction of the interface position of the station's auxiliary structures. Under the condition that the left and right pilot tunnels of the station's upper steps are connected, the middle pilot tunnel of the upper steps within 10m of the station end, auxiliary structure and station structure position is excavated in advance; (2) The remaining upper step middle guide tunnels shall be excavated and supported from the large mileage end and the small mileage end of the station to the middle part of the station; the excavation and support advance of each cycle shall be controlled to be ≤2.5m, and support construction shall be carried out in a timely manner after the excavation is completed. At the same time, the safe step distance of the rock column of the upper step middle guide tunnel shall be controlled to be ≤60m; (3) When the middle rock column is removed, the arch is repaired and trimmed by mechanical construction, and the right guide hole of the middle step is partially padded with slag to meet the requirements for the passage of excavator equipment.

6. The construction method for removing rock pillars in a deep underground space ultra-large cross-section hard rock tunnel according to claim 1 is characterized in that: In the excavation and support steps of the middle guide tunnel in the middle step of the main tunnel, the middle guide tunnel in the middle step is excavated immediately following the middle guide tunnel in the upper step. The middle partition wall is first demolished, and then the middle rock column is excavated. The excavation cycle advance is not more than 3.5m.

7. The construction method for removing rock pillars in a deep underground space ultra-large cross-section hard rock tunnel according to claim 1 is characterized by: When excavating the lower step of the main tunnel, first excavate and support the left guide tunnel of the lower step, then excavate and support the right guide tunnel of the lower step, and finally break the middle guide tunnel of the lower step. The excavation cycle advance is not more than 3.5m.

8. The construction method for removing rock pillars in a deep underground space ultra-large cross-section hard rock tunnel according to claim 1 is characterized by: During the whole construction process, manual monitoring is carried out on the settlement of the tunnel vault, the convergence of clearance, and the settlement of surrounding pipelines. At the same time, steel bar stress gauges, earth pressure boxes, wireless data acquisition instruments, data automation processing and early warning platforms are used to dynamically monitor the whole process of tunnel construction. All-round, three-dimensional and real-time monitoring of the initial support stress of the tunnel and the surrounding rock pressure is carried out, and early warning information is automatically pushed to personal mobile phones to ensure the timeliness and accuracy of the monitoring data and achieve a visual effect of stress monitoring; Manual monitoring and automated monitoring are carried out in parallel to ensure that the initial support of the tunnel is safe, stable and controllable.

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