Construction method of large-section metro underground excavation station expanded arch foot bench method

Abstract

The invention relates to the field of metro construction, in particular to a large-section metro underground excavation station expanded arch springing benching method construction method, which remarkably improves the construction efficiency, shortens the construction period and enhances the stability of primary support through step-by-step and step-by-step excavation in combination with expanded arch springing design. Meanwhile, the method can effectively reduce the disturbance of construction to the surrounding environment, reduce the dependence on geological conditions and improve the construction safety. In addition, the stability and safety of the construction process are ensured through real-time monitoring and flexible adjustment strategies. In general, the arch foot step expanding method for the large-section metro underground excavation station not only solves many limitations of a traditional construction method, but also promotes innovation and development of a metro construction technology, and provides powerful technical support for urban traffic construction.

Description

Technical Field

[0001] The invention relates to the field of subway construction, in particular to a construction method of a large-section subway dark-excavation station with an expanded arch foot step method. Background Art

[0002] With the rapid development of urbanization, subway construction is an important means to alleviate urban traffic pressure, and its construction demand is growing. However, in the central area of ​​the city or areas with complex geological conditions, traditional open-cut construction is subject to many limitations, such as long construction period, great impact on the surrounding environment, and high safety risks. Therefore, it is particularly important to explore efficient, safe, and environmentally friendly subway underground excavation construction technology.

[0003] The construction of large-section subway stations is one of the difficulties in subway construction, especially in areas with complex geological conditions and sensitive surrounding environments. As an advanced underground excavation construction method, the expanded arch foot step method has been widely used in subway construction at home and abroad in recent years. This method effectively improves construction efficiency, enhances the stability of initial support, and reduces disturbance to the surrounding environment through step-by-step excavation combined with the expanded arch foot design.

[0004] Specifically, the construction method of the expanded arch foot step method is based on the principle of the New Austrian Tunneling Method, making full use of the self-stabilizing ability of the surrounding rock and the spatial constraint of the excavation surface. During the construction process, the large-section tunnel is divided into multiple steps for layer-by-layer excavation through weak blasting or mechanical excavation. At the same time, an expanded arch foot is set in the initial support to effectively transfer the arch load to the surrounding rock of the arch foot, thereby improving the bearing capacity and stability of the support structure. In addition, this method also focuses on construction monitoring and adjustment. By real-time monitoring of key parameters such as deformation and stress during the excavation process, construction parameters and support measures are adjusted in a timely manner to ensure construction safety and quality.

[0005] In the practice of subway construction at home and abroad, the method of expanding the arch foot step has achieved remarkable results. For example, in projects such as Shanghai Metro Line 10 and Chongqing Rail Transit Line 9, this method has performed well in improving construction speed, controlling surrounding rock deformation, and ensuring construction safety. These successful cases not only verify the feasibility and superiority of the method of expanding the arch foot step, but also provide strong support for its promotion and application in more subway construction projects.

[0006] Therefore, in view of the importance and complexity of the construction of large-section subway underground stations, as well as the significant advantages of the expanded arch foot step method in actual engineering, it is necessary to conduct in-depth research and improvement on this method and apply for relevant patent protection to promote the continuous advancement and innovative development of subway construction technology. Summary of the invention

[0007] In view of this, the purpose of the present invention is to provide a step method construction method for expanding the arch foot of a large-section subway underground excavation station, reduce the setting and removal of temporary supports, and use the step method for rapid excavation below the arch cover.

[0008] To achieve the above object, the present invention provides the following technical solution: a construction method for expanding the arch foot step method of a large-section subway underground excavation station, comprising the following steps:

[0009] S1, construction preparation;

[0010] S11, conduct geological survey and risk assessment of the construction area, determine construction parameters and support scheme, lay out on-site wind and water pipes, temporary electricity and ventilation pipes, and prepare construction machinery and equipment;

[0011] S12, excavation and support of construction channel;

[0012] S13, the construction channel is topped, and the station main construction area is entered to complete the construction preparation of the construction channel to the station main body topping section;

[0013] S2, construction by expanding the arch foot step method;

[0014] S21, excavation and support of the upper step pilot tunnel: excavation of three pilot tunnels on the upper step of the station body, namely the left, middle and right ones; excavation of the left and right pilot tunnels first, and initial support for expanding the arch foot; temporary vertical supports are set up on both sides of the middle rock mass to ensure construction safety;

[0015] S22, excavation and support of the middle guide tunnel: on the premise of ensuring the stability of the surrounding rock and the initial support structure, the middle guide tunnel is excavated, and the initial support of the arch is carried out in time; after the initial support of the arch reaches the design strength and the monitoring data is stable, the temporary vertical support is removed, so that the upper surrounding rock pressure is transmitted to the surrounding rocks on both sides through the expansion of the arch foot, forming a stable arch structure;

[0016] S23, excavation and support of the middle and lower steps: under the protection of the arch cover, the middle and lower steps of the station are excavated by the step method, and initial support is carried out section by section; the excavation step distance of each pilot tunnel is determined according to the surrounding rock conditions and construction safety requirements to ensure safe and stable construction;

[0017] S24, invert and secondary lining construction; after the lower step is excavated to the bottom of the tunnel, the invert construction begins; after the invert construction is completed, the secondary lining construction of the tunnel is carried out to form a complete tunnel structure.

[0018] Optionally, the excavation and support steps adopt a combination of refined blasting and mechanical excavation to ensure the flatness of the excavation surface and reduce disturbance to the surrounding environment. At the same time, initial support is carried out in a timely manner, including steel support, shotcrete, etc., to ensure the stability of the excavation surface.

[0019] Optionally, after the tunnel is excavated to the bottom and a working surface is available, the invert construction is carried out first, and after the invert length reaches the requirement, the secondary lining trolley is assembled and the secondary lining is constructed to form a complete permanent support structure.

[0020] Optionally, the construction monitoring and adjustment step includes real-time monitoring of key parameters such as deformation and stress during the excavation process, and timely adjustment of construction parameters and support measures based on the monitoring results to ensure construction safety and quality.

[0021] Optionally, it also includes environmental protection measures during the construction process, such as controlling noise and dust pollution to reduce the impact on the surrounding environment and residents' lives.

[0022] Optionally, the initial support adopts support forms such as steel support, shotcrete or grid steel frame, and they are used in combination according to actual conditions.

[0023] The beneficial effects of the present invention are:

[0024] 1) Improve construction efficiency: By excavating in stages and steps, the construction space is expanded, allowing multiple machines and equipment to work simultaneously, significantly improving construction efficiency and shortening construction period.

[0025] 2) Enhance the stability of initial support: An enlarged arch foot is set in the initial support to effectively transfer the arch load to the surrounding rock of the arch foot, improve the bearing capacity and stability of the support structure, and reduce the risk of deformation of the support structure.

[0026] 3) Reduce disturbance to the surrounding environment: Weak blasting or mechanical excavation is used to reduce vibration and noise during construction, and reduce the impact on surrounding buildings and residents' lives. At the same time, through refined construction control, surface subsidence and groundwater leakage are effectively controlled, protecting the safety of the surrounding environment.

[0027] 4) Improve construction safety: By real-time monitoring of key parameters such as deformation and stress during excavation, timely adjustment of construction parameters and support measures ensures safety and stability during construction. In addition, the design of enlarging the arch foot also improves the overall stability of the support structure, further ensuring construction safety.

[0028] 5) Strong adaptability: This construction method can flexibly adapt to different geological conditions and construction environments, especially in areas with complex geological conditions and sensitive surrounding environments, showing stronger adaptability and superiority.

[0029] 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

[0030] 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:

[0031] Figure 1 is a process flow chart of the present invention;

[0032] Figure 2 It is a process flow chart of the step method construction process of the present invention, wherein 1 to 11 represent different pilot holes respectively;

[0033] Figure 3 This is a blasthole arrangement diagram for the station main body blasting construction of the present invention. DETAILED DESCRIPTION

[0034] 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.

[0035] 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.

[0036] 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.

[0037] See also Figure 1 to Figure 3 , which is a construction method for expanding the arch foot steps of a large-section subway underground excavation station, including the following steps:

[0038] S1, construction preparation;

[0039] S11, conduct geological survey and risk assessment of the construction area, determine construction parameters and support scheme, lay out on-site wind and water pipes, temporary electricity and ventilation pipes, and prepare construction machinery and equipment;

[0040] In this embodiment, high-pressure air ducts, high-pressure water pipes, and sewage pipes are configured according to the actual situation on site, and are generally laid out on the right side of the tunnel excavation direction. The order of laying out the air and water pipes from top to bottom is the high-pressure air duct and water pipe, and the diameters are respectively Φ200mm and Φ100mm flanges to connect the high-pressure steel pipes. The pipelines are painted. The pipe rack is made of L50*50 angle steel and fixed to the primary support structure of the tunnel by Φ14 expansion bolts. The vertical angle steel of the pipe rack should be in close contact with the tunnel structure surface, and the bottom of the pipe rack should be no less than 30cm from the ground;

[0041] In this embodiment, temporary electricity use at the construction site must strictly follow the requirements of the specifications, adopt the TN-S system, implement three-level power distribution and two-level protection, and achieve "one machine, one switch, one leakage, one box, and one lock" to eliminate potential accidents and ensure construction safety. The power line is set on the right side of the tunnel excavation direction and must be laid in layers, with high voltage on the top and low voltage on the bottom; the trunk line on the top and the branch line on the bottom; the power line on the top and the lighting line on the bottom. A power line cross arm is set every 6m, and a cable hook is set every 1.5m. A lighting line cross arm is set every 6m, a 36v energy-saving lamp is set every 12m, and a lighting-specific control distribution box is set every 300m of the lighting line. The tunnel electricity uses a three-level distribution (the distribution room is the first level, the electric box in the cave is the second level, and the distribution box on the working surface is the third level), a second-level protection system (distribution box leakage protector and switch box leakage protector), and the tunnel construction electricity should meet the "one box, one switch, one machine, one leakage, and one lock". The working surface uses 36V low-voltage lighting equipment, and the 36V low-voltage transformer is located in a safe and dry place, with the casing grounded. The pump and lighting have double circuits, double power supplies, and double insurance. The "three pipes and two wires" in the tunnel are laid out in accordance with the standardized requirements of civilized construction on the construction site;

[0042] In this embodiment, two 132KW*2 fans are arranged at the tunnel entrance, with air volume of 1695-3300m 3 / min, high-efficiency air volume 2691m3 / min. The air duct adopts zipper-type soft air duct, and customized aluminum air duct is used at the turning and tee parts. The diameter of the main air duct is φ1500mm, the diameter of the branch air duct is φ1200mm, and the diameter of the branch air duct of the working face is φ800mm. The ventilation duct is fixed to the left arch of the tunnel and hung on the tunnel arch with a wire rope. The ventilation ducts are connected with zippers. The ventilation duct buckle fixes the air duct to the wire rope. The wire rope is fixed to the tunnel structure with Φ14 expansion bolts, and the spacing between the expansion bolts is 5m. The ventilation duct should be hung straight and tightened to avoid wrinkles and increase local resistance. The front end of the air duct extends to the excavation face;

[0043] S12, excavation and support of construction channel;

[0044] S13, the construction channel is topped, and the station main construction area is entered to complete the construction preparation of the construction channel to the station main body topping section;

[0045] S2, construction by expanding the arch foot step method;

[0046] S21, remove the portal steel frame columns within the cross-section of the left upper step guide tunnel (guide tunnel No. ①), excavate in the longitudinal direction of the station and provide initial and temporary support for the guide tunnel;

[0047] S22, remove the portal steel frame columns within the cross section of the upper step guide tunnel (guide tunnel No. ②) on the right side, excavate in the longitudinal direction of the station and provide initial and temporary support for the guide tunnel;

[0048] S23, remove the portal steel frame columns within the core soil range of the upper step guide tunnel (guide tunnel No. ③), excavate in the longitudinal direction of the station and carry out initial and temporary support for the guide tunnel. After the monitoring data is stable, remove the temporary supporting steel arch frame;

[0049] S24, excavate the middle step ④ and ⑤ pilot tunnels in stages and provide temporary support. The excavation step distance of each pilot tunnel shall not be less than 10m;

[0050] S25, excavate the middle step ⑥ and ⑦ pilot tunnels respectively, and provide initial support for the side walls;

[0051] S26, excavate the lower step ⑧ and ⑨ pilot tunnels in steps and provide temporary support. The excavation step distance of each pilot tunnel shall not be less than 10m;

[0052] S27, excavate the lower steps ⑩, No. pilot tunnel and provide initial support;

[0053] S28, according to the monitoring and measurement results, determine the construction time of the secondary lining, lay the invert waterproof layer and cast the tunnel invert secondary lining structure;

[0054] S29, laying arch and wall waterproofing layers, and pouring tunnel arch and wall secondary lining structures.

[0055] Optionally, the excavation and support steps adopt a combination of refined blasting and mechanical excavation to ensure the flatness of the excavation surface and reduce disturbance to the surrounding environment. At the same time, initial support is carried out in a timely manner, including steel support, shotcrete, etc., to ensure the stability of the excavation surface.

[0056] In this embodiment, in order to speed up the excavation progress, in sections outside the existing line control protection range and with relatively low sensitivity to the surrounding environment, refined blasting construction is adopted in which digital electronic detonators are detonated hole by hole, and automated monitoring equipment is used to monitor the vibration velocity of surrounding important buildings (structures) to effectively control the impact of vibration generated by blasting on surface protection objects.

[0057] (1) Principles of refined blasting design

[0058] ① Information method construction optimizes tunnel blasting excavation parameters

[0059] Optimize the design of tunnel blasting, determine reasonable cycle footage, blasting parameters and slotting forms, use digital electronic detonators to detonate section by section, strictly control the amount of single-section charge, increase the open surface, and consider comprehensive vibration reduction and vibration reduction blasting measures to strictly control the blasting vibration speed to the minimum.

[0060] ② Strictly control the blasting vibration effect

[0061] In order to ensure the safety of buildings and facilities, the maximum allowable vibration velocity value of the national standard GB6722-2014 "Safety Regulations for Blasting" is strictly followed to estimate the amount of explosives for simultaneous blasting (single stage), and strictly control the blasting vibration effect.

[0062] ③ Blasting vibration speed monitoring

[0063] During blasting, the blasting vibration speed is monitored. By monitoring and analyzing the blasting vibration intensity, the characteristics of the vibration wave and the changes, the blasting parameters are reasonably adjusted in time to achieve the purpose of strictly controlling the seismic wave speed and ensure the safety of the surrounding buildings (structures) on the ground. According to the "Safety Regulations for Blasting" and the actual structural form of buildings, the safe allowable vibration speed of the buildings (structures) to be protected is determined respectively. The blasting vibration speed in sensitive urban areas is controlled at the minimum safe allowable vibration speed, that is, the blasting vibration speed is controlled within 0.5cm / s (sensitive buildings such as residential houses), and the cultural relics protection area is controlled within 0.3cm / s.

[0064] ④ Test gun adjustment parameters

[0065] To ensure the construction safety of blasting operations, the design parameters are first optimized through test blasting, and then adjusted and supplemented based on the blasting vibration monitoring data.

[0066] (2) Blasting parameter design

[0067] The main body of the station was excavated by blasting using the three-step method and the nine-step method. The upper step ①, ②, and ③ pilot tunnels were excavated using double wedge-shaped cutouts and smooth blasting. The middle and lower steps were blasted using horizontal holes with a penetration of 2.1m. Considering the utilization rate of blastholes, the blasthole depth was 2.5m. To ensure that the surrounding rock at the expanded arch foot is not affected, blastholes shall not be arranged within the 1.5m*1.5m range below the expanded arch foot during blasting excavation of the middle and lower steps.

[0068] Detonation time interval: the slot holes, auxiliary holes and bottom plate holes are detonated one by one, and two peripheral holes are detonated. The slot holes are detonated at an interval of 10ms, the auxiliary holes at an interval of 18ms, the peripheral holes at an interval of 10ms, and the bottom plate holes at an interval of 18ms, so as to achieve the effect of staggered shock absorption and reduce the impact on the surrounding environment.

[0069] The order of blasting and excavation of the main section of the station is: 1→2→3→4→5→6→7→8→9→10→11→12;

[0070] The order of detonating holes one by one is: wedge-shaped slot hole → auxiliary hole → smooth blast hole → bottom plate hole.

[0071] (3) Blasting excavation step distance

[0072] The step distance requirements for the main body of the station when blasting is used for construction are as follows:

[0073] The distance between the face of the blasting excavation of the pilot tunnels ①, ②, and ③ on the upper steps of the station body and the initial support is not more than 3.5m, and the advance of each support cycle is not more than 2.5m. The distance between the face of the blasting excavation of the side pilot tunnels of the middle step and the side pilot tunnels of the lower step and the initial support is not more than 4.5m, and the advance of each support cycle is not more than 3.5m. The distance between the face of the blasting excavation of the pilot tunnels in the middle step and the lower step and the initial support should be 5 to 10m.

[0074] (4) Blasting vibration velocity monitoring

[0075] In order to ensure the safe and smooth progress of the main blasting construction of the station, automated vibration velocity monitoring is carried out on important buildings and structures in the blasting impact area. The monitoring data is used to timely optimize the construction operation parameters to ensure the safety of residential buildings, railways, subways and other structures in the impact area, ensure the safe progress of the construction, and at the same time reduce unnecessary civil disputes and reduce social impact.

[0076] ① Monitoring instruments

[0077] The blasting vibration monitoring uses the TC-4850 blasting vibration meter. The TC-4850 blasting vibration meter is very small in size, light in weight, has the advantages of pressure resistance, impact resistance, and easy to carry, and is very suitable for engineering blasting data collection. The instrument consists of three parts: vector sensor, data acquisition system, and analysis software. It can complete the monitoring, recording, and analysis of dynamic processes such as acceleration, speed, frequency, and duration.

[0078] ②Installation of monitoring equipment

[0079] Conduct an environmental survey around the blasting construction area to identify important buildings (structures) within the impact range of the blasting, including existing rail transit lines, important underground pipelines, civil air defense caverns, high-rise buildings on the surface, etc., and install vibration monitoring equipment on the building structures to monitor the blasting vibration speed.

[0080] ③Data collection

[0081] During the blasting at the construction site, the operator remotely accesses the instrument through the client at a different location, starts the acquisition after completing the parameter setting, and the instrument enters the working state. When the vibration signal of the blasting is transmitted, the vibration measurement terminal automatically records and stores the vibration signal, and uploads the entire dynamic waveform collected to the cloud data center in real time. A few minutes after the blasting is initiated, the operator can analyze the uploaded data through the client at a different location and make corresponding types of reports according to needs.

[0082] In this embodiment, after the tunnel is excavated to the bottom and a working surface is available, the invert construction is carried out first. After the invert length reaches the requirement, the secondary lining trolley is assembled and the secondary lining is constructed to form a complete permanent support structure.

[0083] In this embodiment, the construction monitoring and adjustment step includes real-time monitoring of key parameters such as deformation and stress during the excavation process, and timely adjusting construction parameters and support measures according to the monitoring results to ensure construction safety and quality.

[0084] In this embodiment, environmental protection measures are also included during the construction process, such as controlling noise and dust pollution to reduce the impact on the surrounding environment and residents' lives.

[0085] In this embodiment, the initial support adopts support forms such as steel support, shotcrete or grid steel frame, and they are combined and used according to actual conditions.

[0086] 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. The construction method of expanding the arch foot step method for large-section subway underground excavation stations is characterized by: The following steps are involved: S1, construction preparation; S11, conduct geological survey and risk assessment of the construction area, determine construction parameters and support scheme, lay out on-site wind and water pipes, temporary electricity and ventilation pipes, and prepare construction machinery and equipment; S12, excavation and support of construction channel; S13, the construction channel is topped, and the station main construction area is entered to complete the construction preparation of the construction channel to the station main body topping section; S2, construction by expanding the arch foot step method; S21, excavation and support of the upper step pilot tunnel: excavation of three pilot tunnels on the upper step of the station body, namely the left, middle and right ones; excavation of the left and right pilot tunnels first, and initial support for expanding the arch foot; temporary vertical supports are set up on both sides of the middle rock mass to ensure construction safety; S22, excavation and support of the middle guide tunnel: on the premise of ensuring the stability of the surrounding rock and the initial support structure, the middle guide tunnel is excavated, and the initial support of the arch is carried out in time; after the initial support of the arch reaches the design strength and the monitoring data is stable, the temporary vertical support is removed, so that the upper surrounding rock pressure is transmitted to the surrounding rocks on both sides through the expansion of the arch foot, forming a stable arch structure; S23, excavation and support of the middle and lower steps: under the protection of the arch cover, the middle and lower steps of the station are excavated by the step method, and initial support is carried out section by section; the excavation step distance of each pilot tunnel is determined according to the surrounding rock conditions and construction safety requirements to ensure safe and stable construction; S24, invert and secondary lining construction; after the lower step is excavated to the bottom of the tunnel, the invert construction begins; after the invert construction is completed, the secondary lining construction of the tunnel is carried out to form a complete tunnel structure.

2. The construction method of expanding the arch foot step method for a large-section subway underground excavation station according to claim 1 is characterized in that: The excavation and support steps adopt a combination of refined blasting and mechanical excavation to ensure the flatness of the excavation surface and reduce disturbance to the surrounding environment. At the same time, initial support is carried out in a timely manner, including steel support, shotcrete, etc., to ensure the stability of the excavation surface.

3. The construction method of expanding the arch foot step method for a large-section subway underground excavation station according to claim 1 is characterized in that: The invert and secondary lining construction steps are as follows: After excavation reaches the bottom of the tunnel and a working surface is available, the invert construction is carried out first. After the invert length reaches the requirement, the secondary lining trolley is assembled and the secondary lining is constructed to form a complete permanent support structure.

4. The construction method of expanding the arch foot step method for a large-section subway underground excavation station according to claim 1 is characterized in that: The construction monitoring and adjustment steps include real-time monitoring of key parameters such as deformation and stress during the excavation process, and timely adjustment of construction parameters and support measures based on the monitoring results to ensure construction safety and quality.

5. The construction method of expanding the arch foot step method for a large-section subway underground excavation station according to claim 1 is characterized in that: It also includes environmental protection measures during the construction process, such as controlling noise and dust pollution to reduce the impact on the surrounding environment and residents' lives.

6. The construction method of expanding the arch foot step method for a large-section subway underground excavation station according to claim 1 is characterized by: The initial support adopts support forms such as steel support, shotcrete or grid steel frame, and they are combined according to actual conditions.

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