A tunnel arch removal and replacement auxiliary trolley and construction method thereof

Abstract

The present invention discloses a tunnel arch removal and replacement auxiliary trolley and a construction method thereof, including a temporary arch protection, a hydraulic jack A, a rubber tire, a hydraulic support leg, a work platform, a hydraulic jack B, a horizontal slide rail, a fixed latch, and a fixed pedestal. The beneficial effects of the present invention are: the mobile arch replacement trolley is flexible and can provide temporary support, and the size of the temporary support steel arch frame can be adjusted within a certain range in the circumferential direction to adapt to the change in the tunnel diameter. In addition, the spacing between the two temporary arch protections can also be adjusted forward and backward in the longitudinal direction of the tunnel to adapt to the change in the spacing between the initial support steel arch frames of the tunnel. With the help of the mobile arch replacement trolley, the safe and rapid removal and replacement of the steel arch frames of the local (arch top, side wall) of the initial support deformation intrusion limit of the tunnel can be achieved.

Description

Technical Field

[0001] The invention relates to an arch replacement auxiliary trolley, in particular to a tunnel arch removal and replacement auxiliary trolley and a construction method thereof, belonging to the technical field of tunnel construction. Background Art

[0002] In the construction of mountain tunnel projects, poor geological areas are often encountered, with developed joints and fissures, soft rock, and poor self-stabilization ability, which may cause problems such as arch sinking and cracking and intrusion of initial support. Especially in the construction of expansive rock areas, the surrounding rock will swell and soften to varying degrees when it encounters water, further increasing the deformation. Even if high-strength support and a large reserved deformation are adopted, initial support intrusion may occur. In addition, due to the large buried depth of the tunnel, the surrounding rock is subjected to a high level of ground stress. During the tunnel excavation process, as the ground stress is released, the surrounding rock deforms greatly, causing the initial support steel arch frame to bear a large stress, which is prone to excessive deformation of the initial support and excessive intrusion or insufficient support capacity. During the on-site construction process, the initial support intrusion problem occurred many times, especially in the core construction section crossing the fault fracture zone, where the surrounding rock deformation is greater, the initial support deformation is more serious, and part or all of the support capacity has been lost. It is necessary to scientifically and rationally replace the severely deformed initial support steel arch frame to ensure the quality and safety of tunnel construction.

[0003] An issue that requires special attention is that when the initial support intrusion limit of a tunnel passing through a fault fracture zone with squeezing soft surrounding rock needs to be replaced, due to the poor surrounding rock conditions and construction environment, the risk factors faced in the arch replacement process are more complex and changeable, the construction risk is high, the difficulty is large, the efficiency is low, and the safety of construction personnel and machinery and equipment will be greatly threatened.

[0004] The existing technology for excavating the initial support and replacing the arch due to deformation and intrusion in mountain tunnels mainly adopts backfilling in the range where the arch needs to be replaced, or uses a simple stand to create an arch replacement operation platform, and then performs the arch replacement operation. The existing technology has a large construction workload and slow construction progress, which has a great impact on the construction period. In addition, the temporary support used in the existing technology is generally not reusable, and the steel arch frame used for temporary support needs to be customized according to the on-site conditions, which is not convenient, and when applying temporary support, the on-site staff will face greater risks. Summary of the invention

[0005] The purpose of the present invention is to provide a tunnel arch removal and replacement auxiliary trolley and a construction method thereof in order to solve the problem.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions: a tunnel arch removal and replacement auxiliary trolley, comprising

[0007] A temporary arch protection, which is arranged on the outside of the door-shaped frame of the auxiliary trolley and has a double arch frame and segmented design;

[0008] A working platform, which is used to provide a working space for the staff and is located in the middle of the temporary arch protection on both sides and is fixed to the steel frame of the auxiliary trolley by welding;

[0009] The horizontal slide rail is used to drive the temporary arch guard to move forward and backward along the longitudinal direction of the tunnel along the site, and is opened on both sides of the steel frame of the auxiliary trolley and is located below the portal frame on which the temporary arch guard is installed.

[0010] As a further solution of the present invention: in an embodiment of the present invention, one end of the temporary arch protection of adjacent segments is designed as a groove, and the other end is designed as a protrusion, and the groove and the protrusion are connected by a fixing pin after being embedded.

[0011] As a further solution of the present invention: in an embodiment of the present invention, a hydraulic jack A is arranged between the temporary guard arch 1 and the portal frame of the auxiliary trolley, the bottom end of the hydraulic jack A is rigidly connected to the portal frame by bolts, and the movable top end of the hydraulic jack A is hingedly connected to a fixed pedestal arranged below the hinge of the temporary guard arch by a pin.

[0012] As a further solution of the present invention: in an embodiment of the present invention, a certain number of rubber tires of a certain size are installed at the front, rear and middle parts of the steel frame of the auxiliary trolley, and two rubber tires are installed on both sides of the steel frame at each location.

[0013] As a further solution of the present invention: in an embodiment of the present invention, a hydraulic support leg is installed on one side of the installation position of the rubber tire. When the arch changing trolley needs to move, the hydraulic support leg is controlled to retract and stow away when the trolley moves to the working position.

[0014] As a further solution of the present invention: in an embodiment of the present invention, the working platform is divided into two layers, an upper layer and an lower layer.

[0015] As a further solution of the present invention: a hydraulic jack B is connected between the portal frame of the auxiliary trolley and the steel frame of the auxiliary trolley located on the portal frame.

[0016] A tunnel arch replacement auxiliary trolley, the construction method of which comprises the following steps

[0017] (1) Preparation before construction

[0018] ① Set up settlement observation points. Increase the number of monitoring points in the arch replacement section. The spacing between each monitoring point is determined based on the actual situation on site. Surveyors increase the frequency of observations and promptly feed back data to on-site technicians to ensure that the surrounding rock deformation is within the safe allowable range before allowing the arch replacement trolley to enter the site for construction.

[0019] ② Carry out a comprehensive inspection of the mobile arch-changing trolley to ensure that all functions of the trolley are normal. Adjust the size of the steel arch frame of the temporary arch protection on the arch-changing trolley to ensure that the trolley can enter the site smoothly without touching the tunnel contour surface.

[0020] ③ Clean and inspect the ground within the arch replacement range to ensure that the trolley can enter the site safely and provide sufficient support for the arch replacement trolley.

[0021] (2) Temporary support provided by the arch replacement trolley

[0022] After the settlement observation meets the requirements, the mobile arch replacement trolley drives to the position where the arch needs to be replaced, and adjusts the distance between the two temporary arches. The distance must ensure sufficient construction space and good support effect. The distance between 1 to 2 arch frames can be selected. By controlling the extension of the hydraulic jack A, the arch guard is expanded along the circumferential direction and supported on both sides of the steel arch frame that needs to be replaced, providing temporary support for the surrounding rock of the arch replacement operation section. After the temporary support is completed, high-frequency settlement monitoring is required for the settlement observation point to confirm that the support effect of the temporary support can meet the safety construction requirements.

[0023] (3) Reinforcement of surrounding rock in the arch replacement area

[0024] After the arch-changing trolley provides temporary support, in order to enhance the strength and stability of the surrounding rock, it is necessary to reinforce the surrounding rock within a certain range of the arch-changing part, and anchor rods can be installed for grouting reinforcement. Under the temporary arch protection provided by the arch-changing trolley, the construction workers install anchor rods and perform grouting reinforcement on the working platform of the arch-changing trolley.

[0025] For areas where the initial support steel arch frame is severely deformed, locking anchor rods should be installed at appropriate positions above the deformation position and before and after the deformation section. Two groups should be installed on each side. The locking anchor rods should be made of seamless steel pipes. The installation angle should be controlled between 30-45°, and the installation depth should be controlled to be more than 95% of the total length of the anchor rod. Hot-rolled ribbed "U"-shaped bars should be used for welding. During welding, the welding quality between the locking anchor rod and the inner arc of the steel arch frame should be guaranteed to ensure joint force.

[0026] (4) Removal of deformed primary support steel arch

[0027] For the part where the arch is to be replaced, the concrete on the inner arc surface of the steel arch frame and the surrounding of the steel arch frame should be chiseled off, and the part protruding from the outline should be chiseled off to ensure the clearance of the initial support. The treatment is done manually with an electric pick. To ensure that the steel arch frame is not damaged by a large external force, it is forbidden to use a blasting hammer for treatment.

[0028] When partially dismantling and replacing the arch, the principle of dismantling in sections from top to bottom should be followed. The cutting position of the steel arch frame should be placed in advance using a total station, and the cutting point should be marked with red spray paint. On-site construction personnel use a plasma cutter to cut. When cutting, they should try to ensure that the cut of the steel arch frame is flush, so that the interface is straight and complete when the arch is replaced. After using the total station to place the points, each steel arch frame is numbered. The on-site management personnel obtain the specific arch replacement dimensions of each steel arch frame based on the measurement results. The steel structure processing center performs precise processing according to the numbered dimensions and numbers them to facilitate construction after they are transported to the site.

[0029] (5) Install new primary steel arch

[0030] When installing a new primary steel arch frame on site, thick steel plates should be used for welding the webs on both sides of the steel arch frame, and thick steel plates should also be used for welding the inner arc of the steel arch frame. The weld should be full during welding to avoid problems such as leaking welding and loose welding.

[0031] After the steel arch frame is replaced, the steel mesh and connecting steel bars must be re-welded to ensure the lap length and welding quality, and the concrete must be sprayed again. The inner arc protection layer of the steel arch frame is 2cm concrete. Before spraying concrete, check again whether the size is correct to ensure that no secondary under-excavation occurs. When installing a new primary steel arch frame on site, the settlement and convergence of the primary steel arch frame must be observed on site. Once the primary support deformation is found to be large, stop construction immediately and evacuate personnel.

[0032] (6) Withdraw the temporary support of the arch replacement trolley

[0033] After the arch replacement is completed, all construction workers evacuate the site. By controlling the retraction of the hydraulic jack A2, the size of the temporary arch protection on the arch replacement trolley is reduced in the circumferential direction to achieve the withdrawal of the arch protection. After that, high-frequency settlement observations are carried out on the primary support. After confirming that its deformation meets the construction safety requirements, the arch replacement trolley is driven away to the next location where the arch needs to be replaced.

[0034] The beneficial effects of the present invention are:

[0035] 1. The mobile arch-changing trolley has a reasonable walking and supporting device, which can realize free movement in the tunnel and adjustment of the walking direction within a certain range. The support enables the trolley to bear the supporting self-stabilizing capacity that meets the construction requirements;

[0036] 2. The mobile arch replacement trolley can provide temporary arch protection. During the arch replacement construction process, the temporary arch protection can be supported at reasonable positions on both sides of the steel arch frame that needs to be replaced, inhibiting the continuous deformation of the surrounding rock, providing a safe operating space for construction personnel, and ensuring the safety of arch replacement workers. After the arch replacement is completed, the temporary arch protection can be removed as a whole, realizing the reusability of the temporary arch protection;

[0037] 3. It can adapt to the changes in tunnel diameter. The circumferential size of the temporary arch protection of the mobile arch-changing trolley can be adjusted within a certain range. In addition, the position of the temporary arch protection on the mobile arch-changing trolley can be moved within a certain range, and the temporary arch protection can be supported at reasonable positions on both sides of the steel arch frame that needs to be replaced, so as to adapt to the changes in the longitudinal arrangement spacing of the initial steel arch frame in the tunnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic diagram of the movable arch changing trolley of the present invention;

[0039] Figure 2 A bottom view of the temporary arch protection connection structure of the present invention;

[0040] Figure 3 A side view of the temporary arch protection connection structure of the present invention;

[0041] Figure 4 This is a cross-sectional view of a temporary arch protection of the present invention;

[0042] Figure 5 It is a construction process flow chart of the present invention;

[0043] Figure 6 This is a side view of the steel arch replacement of the present invention;

[0044] Figure 7 This is a front view of the structural steel arch replacement of the present invention.

[0045] In the figure: 1. temporary arch protection, 2. hydraulic jack A, 3. rubber tire, 4. hydraulic support leg, 5. working platform, 6. hydraulic jack B, 7. horizontal slide rail, 8. fixing pin, 9. fixing base. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] Embodiment 1

[0048] See also Figures 1 to 4 , a tunnel arch replacement auxiliary trolley, comprising

[0049] A temporary arch 1 is arranged on the outside of the door-shaped frame of the auxiliary trolley and is designed in a double-arch frame and segmented manner;

[0050] The working platform 5 is used to provide a working space for the staff and is located in the middle of the temporary arches 1 on both sides and is fixed to the steel frame of the auxiliary trolley by welding;

[0051] The horizontal slide rail 7 is used to drive the temporary arch guard 1 to move forward and backward along the tunnel longitudinal direction along the site, and is opened on both sides of the steel frame of the auxiliary trolley and is located below the portal frame on which the temporary arch guard 1 is installed.

[0052] In an embodiment of the present invention, one end of the temporary arch protection 1 of adjacent segments is designed as a groove and the other end is designed as a protrusion, and the groove and the protrusion are connected by a fixed pin 8 after being embedded, and the adjacent segments of the temporary arch protection 1 are hingedly connected, so that the temporary arch protection steel arch frame can be rotated along the circumferential direction by a certain angle, thereby adjusting the arch protection size within a certain range. Therefore, the equivalent radius of the temporary arch protection 1 is variable within a certain range, and the segmented arch protection can better fit the tunnel excavation contour surface.

[0053] In the embodiment of the present invention, a hydraulic jack A2 is arranged between the temporary arch guard 1 and the portal frame of the auxiliary trolley, and the bottom end of the hydraulic jack A2 is rigidly connected to the portal frame by bolts, and the movable top end of the hydraulic jack A2 is hingedly connected to the fixed pedestal 9 arranged below the hinge of the temporary arch guard 1 by a latch. Through the advancement and retraction of the hydraulic jack A2, the equivalent size of the temporary arch guard 1 can be changed within a certain range, and it can be ensured that the hydraulic jack A2 has sufficient stability, can better support the temporary arch guard 1 itself and the load imposed on the arch by the surrounding rock, and provide protection for the safety of the arch replacement operation.

[0054] In the embodiment of the present invention, a certain number of rubber tires 3 of a certain size are installed at the front, rear and middle parts of the steel frame of the auxiliary trolley, and two rubber tires 3 are distributed and installed on both sides of the steel frame to achieve the mobility of the trolley and make the trolley walk more stably.

[0055] In the embodiment of the present invention, a hydraulic support leg 4 is installed on one side of the installation position of the rubber tire 3. When the arch changing trolley needs to move, the hydraulic support leg 4 is controlled to retract and stow. When the trolley moves to the working position, the hydraulic support leg 4 is controlled to push and extend, so that part or all of the load borne by the rubber tire 3 is transferred to the hydraulic support leg 4, which can improve the overall load-bearing capacity and stability of the trolley and ensure the safety of construction operations.

[0056] In the embodiment of the present invention, the working platform 5 is divided into two layers, which can provide a spacious platform for construction workers and meet the needs of dismantling and installing the primary support arch frame, drilling and anchoring, grouting and other operations.

[0057] In an embodiment of the present invention, a hydraulic jack B6 is connected between the portal frame of the auxiliary trolley and the steel frame of the auxiliary trolley located on the portal frame. Through the pushing and contraction of the hydraulic jack B6, the temporary arch guard 1 can be moved forward and backward within a certain range to adapt to the changes in the spacing of the initial supporting steel arch frame.

[0058] Embodiment 2

[0059] See also Figures 5 to 7 A tunnel arch replacement auxiliary trolley, the construction method of which includes the following steps

[0060] (1) Preparation before construction

[0061] ① Set up settlement observation points. Increase the number of monitoring points in the arch replacement section. The spacing between each monitoring point is determined based on the actual situation on site. Surveyors increase the frequency of observations and promptly feed back data to on-site technicians to ensure that the surrounding rock deformation is within the safe allowable range before allowing the arch replacement trolley to enter the site for construction.

[0062] ② Carry out a comprehensive inspection of the mobile arch-changing trolley to ensure that all functions of the trolley are normal. Adjust the size of the steel arch frame of the temporary arch protection on the arch-changing trolley to ensure that the trolley can enter the site smoothly without touching the tunnel contour surface.

[0063] ③ Clean and inspect the ground within the arch replacement range to ensure that the trolley can enter the site safely and provide sufficient support for the arch replacement trolley.

[0064] (2) Temporary support provided by the arch replacement trolley

[0065] After the settlement observation meets the requirements, the mobile arch replacement trolley drives to the position where the arch needs to be replaced, and adjusts the distance between the two temporary arch guards 1. The distance must ensure sufficient construction space and good support effect. The distance between 1 to 2 arch frames can be selected. By controlling the extension of the hydraulic jack A2, the arch guard is expanded along the circumferential direction and supported on both sides of the steel arch frame that needs to be replaced, providing temporary support for the surrounding rock of the arch replacement operation section. After the temporary support is completed, high-frequency settlement monitoring is required for the settlement observation point to confirm that the support effect of the temporary support can meet the safety construction requirements.

[0066] (3) Reinforcement of surrounding rock in the arch replacement area

[0067] After the arch-changing trolley provides temporary support, in order to enhance the strength and stability of the surrounding rock, it is necessary to reinforce the surrounding rock within a certain range of the arch-changing part, and anchor rods can be installed for grouting reinforcement. Under the temporary arch protection provided by the arch-changing trolley, the construction workers install anchor rods and perform grouting reinforcement on the working platform of the arch-changing trolley.

[0068] For areas where the initial support steel arch frame is severely deformed, locking anchor rods should be installed at appropriate positions above the deformation position and before and after the deformation section. Two groups should be installed on each side. The locking anchor rods should be made of seamless steel pipes. The installation angle should be controlled between 30-45°, and the installation depth should be controlled to be more than 95% of the total length of the anchor rod. Hot-rolled ribbed "U"-shaped bars should be used for welding. During welding, the welding quality between the locking anchor rod and the inner arc of the steel arch frame should be guaranteed to ensure joint force.

[0069] (4) Removal of deformed primary support steel arch

[0070] For the part where the arch is to be replaced, the concrete on the inner arc surface of the steel arch frame and the surrounding of the steel arch frame should be chiseled off, and the part protruding from the outline should be chiseled off to ensure the clearance of the initial support. The treatment is done manually with an electric pick. To ensure that the steel arch frame is not damaged by a large external force, it is forbidden to use a blasting hammer for treatment.

[0071] When partially dismantling and replacing the arch, the principle of dismantling in sections from top to bottom should be followed. The cutting position of the steel arch frame should be placed in advance using a total station, and the cutting point should be marked with red spray paint. On-site construction personnel use a plasma cutter to cut. When cutting, they should try to ensure that the cut of the steel arch frame is flush, so that the interface is straight and complete when the arch is replaced. After using the total station to place the points, each steel arch frame is numbered. The on-site management personnel obtain the specific arch replacement dimensions of each steel arch frame based on the measurement results. The steel structure processing center performs precise processing according to the numbered dimensions and numbers them to facilitate construction after they are transported to the site.

[0072] (5) Install new primary steel arch

[0073] When installing a new primary steel arch frame on site, thick steel plates should be used for welding the webs on both sides of the steel arch frame, and thick steel plates should also be used for welding the inner arc of the steel arch frame. The weld should be full during welding to avoid problems such as leaking welding and loose welding.

[0074] After the steel arch frame is replaced, the steel mesh and connecting steel bars must be re-welded to ensure the lap length and welding quality, and the concrete must be sprayed again. The inner arc protection layer of the steel arch frame is 2cm concrete. Before spraying concrete, check again whether the size is correct to ensure that no secondary under-excavation occurs. When installing a new primary steel arch frame on site, the settlement and convergence of the primary steel arch frame must be observed on site. Once the primary support deformation is found to be large, stop construction immediately and evacuate personnel.

[0075] (6) Withdraw the temporary support of the arch replacement trolley

[0076] After the arch replacement is completed, all construction workers evacuate the site. By controlling the retraction of the hydraulic jack A2, the size of the temporary arch protection on the arch replacement trolley is reduced in the circumferential direction to achieve the withdrawal of the arch protection. After that, high-frequency settlement observations are carried out on the primary support. After confirming that its deformation meets the construction safety requirements, the arch replacement trolley is driven away to the next location where the arch needs to be replaced.

[0077] Working principle: The rubber tire 3 enables free movement in the tunnel, and the support of the hydraulic legs 4 enables the trolley to bear the supporting self-stabilizing capacity that meets the construction requirements. During the arch replacement construction process, the temporary arch protection can be supported at reasonable positions on both sides of the steel arch frame that needs to be replaced, suppressing the continuous deformation of the surrounding rock, providing a safe operating space for construction personnel, and ensuring the safety of arch replacement workers. After the arch replacement is completed, the temporary arch protection can be withdrawn as a whole to achieve the reusability of the temporary arch protection; and the circumferential size of the temporary arch protection of the mobile arch replacement trolley can be adjusted within a certain range; in addition, the position of the temporary arch protection of the mobile arch replacement trolley on the trolley can be moved within a certain range, and the temporary arch protection can be supported at reasonable positions on both sides of the steel arch frame that needs to be replaced to adapt to the changes in the longitudinal arrangement spacing of the initial steel arch frame in the tunnel.

[0078] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0079] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A construction method of a tunnel arch removal and replacement auxiliary trolley, characterized in that: The tunnel arch replacement auxiliary trolley comprises: A temporary protective arch (1) is arranged on the outer side of the door-shaped frame of the auxiliary trolley and is of a double-arch frame and segmented design; A working platform (5), which is used to provide a working space for workers and is located in the middle of the temporary protective arches (1) on both sides, and is fixed to the steel frame of the auxiliary trolley by welding; A horizontal slide rail (7) used to drive the temporary arch guard (1) to move forward and backward along the tunnel longitudinal direction and along the site, and the horizontal slide rail (7) is provided on both sides of the steel frame of the auxiliary trolley and is located below the door-shaped frame on which the temporary arch guard (1) is installed; The ends of the temporary arch guard (1) of adjacent sections are designed as a groove and a protrusion, and the groove and the protrusion are connected by a fixed pin (8) after being embedded; a hydraulic jack A (2) is arranged between the temporary arch guard (1) and the portal frame of the auxiliary trolley, the bottom end of the hydraulic jack A (2) is rigidly connected to the portal frame by bolts, and the movable top end of the hydraulic jack A (2) is hingedly connected to a fixed pedestal (9) arranged below the hinge of the temporary arch guard (1) by a pin; rubber tires (3) are installed at the front, back and middle parts of the steel frame of the auxiliary trolley, and two rubber tires (3) are installed on both sides of the steel frame at each location; a hydraulic support leg (4) is installed on one side of the installation position of the rubber tire (3); the working platform (5) is divided into upper and lower layers; a hydraulic jack B (6) is connected between the portal frame of the auxiliary trolley and the steel frame of the auxiliary trolley located on the portal frame; The construction method comprises the following steps: (1) Preparation before construction ① Set up settlement observation points, increase the number of monitoring points in the arch replacement section, and determine the spacing between each monitoring point based on the actual situation on site. Surveyors should increase the frequency of observation and provide timely feedback of data to on-site technicians to ensure that the surrounding rock deformation is within the safe allowable range before allowing the arch replacement trolley to enter the site for construction; ② Carry out a comprehensive inspection of the mobile arch-changing trolley to ensure that all functions of the trolley are normal, adjust the size of the steel arch frame of the temporary arch protection on the arch-changing trolley, and ensure that the trolley can enter the tunnel smoothly without touching the tunnel contour surface; ③ Clean and inspect the ground within the arch replacement range to ensure that the trolley can enter the site safely and provide sufficient support for the arch replacement trolley; (2) The arch replacement trolley provides temporary support After the settlement observation meets the requirements, the mobile arch replacement trolley moves to the position where the arch needs to be replaced, and adjusts the distance between the two temporary arch guards (1). The distance should ensure sufficient construction space and good support effect. The distance between 1 to 2 arch frames is selected, and the extension of the hydraulic jack A (2) is controlled so that the arch guards are spread out along the circumferential direction and supported on both sides of the steel arch frame where the arch needs to be replaced, thereby providing temporary support for the surrounding rock of the arch replacement operation section. After the temporary support is completed, high-frequency settlement monitoring is required at the settlement observation point to confirm that the support effect of the temporary support can meet the safety construction requirements; (3) Reinforcement of surrounding rock in the arch replacement area After the arch-changing trolley provides temporary support, in order to enhance the strength and stability of the surrounding rock, it is necessary to reinforce the surrounding rock within a certain range of the arch-changing position, install anchor rods and perform grouting reinforcement. Under the temporary arch protection provided by the arch-changing trolley, the construction personnel install anchor rods and perform grouting reinforcement on the working platform of the arch-changing trolley; For the parts with serious deformation of the initial support steel arch frame, the locking foot anchor rods shall be installed at the appropriate position above the deformation position and at the appropriate position before and after the deformation section. Two groups shall be installed on each side. The locking foot anchor rods shall be made of seamless steel pipes. The installation angle shall be controlled between 30-45° and the installation depth shall be controlled at more than 95% of the total length of the anchor rods. Hot-rolled ribbed "U"-shaped bars shall be used for welding. During welding, the welding quality of the locking foot anchor rods and the inner arc of the steel arch frame shall be ensured to ensure joint force. (4) Removal of deformed primary support steel arch For the parts where the arches are to be replaced, the concrete on the inner arc surface of the steel arch frame and around the steel arch frame should be chiseled off, and the parts protruding from the contour line should be chiseled off to ensure the clearance of the initial support. The parts should be processed manually with electric picks. To ensure that the steel arch frame is not damaged by large external forces, it is forbidden to use a blasting hammer for processing. When partially dismantling and replacing arches, the principle of dismantling in sections from top to bottom should be followed. The cutting position of the steel arch frame should be placed in advance using a total station, and the cutting point should be marked with red spray paint. On-site construction personnel use a plasma cutter to cut. When cutting, they should try to ensure that the cut of the steel arch frame is flush, so that the interface is straight and complete when replacing the arch. After using the total station to place the points, each steel arch frame is numbered. The on-site management personnel obtain the specific arch replacement size of each steel arch frame based on the measurement results. The steel structure processing center performs precise processing according to the numbered size and numbers it to facilitate construction after it is transported to the site; (5) Install new primary steel arch frame When installing the new primary steel arch frame on site, thick steel plates should be used for welding the webs on both sides of the steel arch frame, and thick steel plates should also be used for welding the inner arc of the steel arch frame; After the steel arch frame is replaced, the steel mesh and connecting steel bars must be re-welded to ensure the lap length and welding quality, and the concrete must be sprayed again. The inner arc protection layer of the steel arch frame is 2cm concrete; before spraying concrete, check again whether the size is correct to ensure that no secondary under-excavation occurs. When installing a new primary support steel arch frame on site, the settlement and convergence of the primary support steel arch frame must be observed on site. Once a large deformation of the primary support is found, the construction will be stopped immediately and the personnel will be evacuated; (6) Withdraw the temporary support of the arch replacement trolley After the arch replacement is completed, all construction workers evacuate the site. By controlling the retraction of the hydraulic jack A (2), the size of the temporary arch protection on the arch replacement trolley is reduced along the circumferential direction to achieve the arch protection withdrawal. After that, the primary support is subjected to high-frequency settlement observation. After confirming that its deformation meets the construction safety requirements, the arch replacement trolley is driven away to the next location where the arch replacement is required.

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