Portal steel frame support structure for tunnel intersections and its construction method

Abstract

This invention discloses a portal steel frame support structure for tunnel intersections and its construction method, relating to the field of tunnel construction. The structure includes a ventilation connecting tunnel portal frame, a maintenance access tunnel portal frame, and an exhaust connecting tunnel portal frame. Each of these portal frames comprises a portal steel frame body, which includes a vertical support arch, a portal frame crossbeam, an arc-shaped support arch, anchor bolts, and diagonal braces. The vertical support arch uses two I28a I-beams symmetrically arranged on both sides of the portal steel frame body as the vertical support structure. The portal frame crossbeam is connected to the vertical support arch, and the arc-shaped support arch is also connected to the portal frame crossbeam. The anchor bolts are double-strength and embedded in the surrounding rock to fix the vertical support arch. The diagonal braces use I20a I-beams and are positioned between the portal frame crossbeam and the vertical support arch.

Description

Technical Field

[0001] This invention relates to the field of tunnel construction technology, and in particular to portal steel frame support structures for tunnel intersections and their construction methods. Background Technology

[0002] Tunnel intersections are critical and vulnerable points in tunnel construction. Due to the influence of multiple intersecting chambers, the stress distribution of the surrounding rock in this area is complex and the stress state is unstable, making it prone to safety hazards such as surrounding rock deformation and collapse, which seriously threaten the safety of construction personnel and the progress of construction.

[0003] Currently, the support structures for tunnel intersections mostly adopt conventional steel arch frame splicing, which has many defects: First, poor adaptability, unable to provide precise support for air supply connecting passages, exhaust connecting passages, and maintenance passages of different sizes at tunnel intersections, making it difficult to meet the support needs of different cross-sections; Second, insufficient support stability, with insufficient rigidity of the vertical support structure, inadequate arch foot treatment, and poor locking foot fixing effect, which easily leads to the displacement and instability of the support structure; Third, insufficient connection reliability, with each component having a single connection method, failing to form an overall load-bearing structure, and weak resistance to lateral displacement; Fourth, the construction process lacks systematicity, with unreasonable connections between various procedures, which easily leads to construction safety hazards.

[0004] Therefore, developing a portal steel frame support structure for tunnel intersections that is highly adaptable, provides stable support, and has reliable connections has become an urgent need to solve the above-mentioned technical problems. Summary of the Invention

[0005] In view of the above situation and to overcome the defects of the prior art, the present invention provides a portal steel frame support structure for tunnel intersections and its construction method, which effectively solves the problems of poor adaptability, insufficient stability and unreliable connection of the existing support structure, and realizes accurate and stable support for tunnel intersections and connecting roads, thus ensuring the safety of tunnel construction.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention includes an air supply connecting duct gantry, a maintenance access gantry, and an exhaust connecting duct gantry. Each of these gantry comprises a portal steel frame body. The portal steel frame body includes a vertical support arch, a gantry beam, an arc-shaped support arch, anchor bolts, and diagonal braces. The vertical support arch uses two I28a I-beams symmetrically arranged on both sides of the portal steel frame body as the vertical support structure. The gantry beam is connected to the vertical support arch, and the arc-shaped support arch is also connected to the gantry beam. The anchor bolts are double-stretched and embedded in the surrounding rock to fix the vertical support arch. The diagonal braces use I20a I-beams and are positioned between the gantry beam and the vertical support arch.

[0007] Preferably, the dimensions of the three sets of portal steel frame bodies are as follows: the width of the air supply connecting passage portal frame is 1200 cm and the height is 717.1 cm; the width of the exhaust connecting passage portal frame is 2400 cm and the height is 717.1 cm; and the width of the maintenance passage portal frame is 400 cm and the height is 497.5 cm.

[0008] Preferably, the bottom of the vertical support arch is provided with a double layer of 10 mm steel plates, which are laid between the bottom of the vertical support arch and the surrounding rock.

[0009] Preferably, the gantry beam and the vertical support arch are connected and fixed by arch bolts and welding.

[0010] Preferably, monitoring and measurement points are provided at the midpoint and both ends of the gantry beam to monitor the deformation of the gantry beam in real time.

[0011] Preferably, the two ends of the diagonal brace are fixedly connected to the portal frame beam and the vertical support arch frame by welding.

[0012] The construction method for portal steel frame support structures used at tunnel intersections includes the following steps: S1, the cross section of the fan room at the intersection of the construction tunnel, complete the excavation and initial support of the fan room. After the initial support structure of the fan room is stable, the excavation of the guide tunnels for the air supply connection, exhaust connection and maintenance passage will be carried out. S2. Based on the design positions of the air supply duct gantry, exhaust duct gantry, and maintenance passage gantry, determine the installation position and height of the corresponding vertical support arch for each gantry. After marking and positioning, clean up any loose debris at the marked positions. S3. Lay double-layer 10mm steel plates at the installation position of the cleaned vertical support arch frame to complete the arch foot treatment. Then, remove the initial support arch frame at the corresponding position of the fan room. After the removal is completed, hoist the two vertical support arch frames made of I28a I-beams to the designated position and adjust them into place. S4. After the vertical support arch is installed, double anchor bolts are installed at its bottom. The anchor bolts are embedded into the surrounding rock. The position of the vertical support arch is re-measured. After confirming that the position is correct, spray concrete is applied to the outside of the vertical support arch so that the spray concrete layer wraps around the vertical support arch and fits tightly with the surrounding rock, thus completing the fixation of the vertical support arch. S5. After the vertical support arch is reinforced, the portal frame beam of the main body of the portal steel frame is hoisted, and the portal frame beam is connected and fixed to the vertical support arch by arch bolts and welding. At the same time, the portal frame beam is welded to the steel arch of the fan room to form an integral load-bearing structure. Monitoring and measurement points are set at the midpoint and both ends of the portal frame beam. S6. After the gantry beam is installed, I20a diagonal bracing is added between the gantry beam and the vertical support arch. The installation position of the diagonal bracing is adjusted to ensure that it avoids the initial support arch of the air supply and exhaust ducts and does not encroach on the cross-sectional space of each duct. Then, the two ends of the diagonal bracing are welded and fixed to the gantry beam and the vertical support arch respectively. After the main body of the portal steel frame, vertical support arch frame, and diagonal brace are installed, a comprehensive inspection of the entire portal steel frame support structure is carried out to confirm that all connection parts are firm, the position is accurate, and the monitoring and measurement points are normal. Then, shotcrete operation is carried out to comprehensively spray the portal steel frame support structure and the surrounding rock. After the shotcrete layer reaches the design strength, the entire support construction is completed.

[0013] Compared with the prior art, the beneficial effects of the present invention are: 1. Strong adaptability: The present invention sets up three sets of masts: air supply connecting mast, exhaust connecting mast, and maintenance access mast, which correspond to connecting masts of different sizes at tunnel intersections. The size of each mast is precisely matched to the corresponding connecting mast, which can provide targeted support and solve the problem of poor adaptability of existing support structures.

[0014] 2. High support stability: The vertical support arch frame adopts two I28a I-beams, combined with double-layer 10mm steel plate arch foot treatment, which can effectively disperse stress and reinforce the arch foot; double locking anchor rods are embedded in the surrounding rock to further fix the vertical support arch frame and prevent it from shifting; the setting of diagonal bracing enhances the overall resistance to lateral displacement, ensuring that the entire support structure is stable and reliable, effectively resisting the pressure of the surrounding rock and avoiding the risk of collapse.

[0015] 3. Reliable connection: The gantry beam and the vertical support arch are fixed by a combination of bolt and welding. The diagonal brace is welded to the gantry beam and the vertical support arch. At the same time, the gantry beam and the steel arch of the fan room are welded to form an integral load-bearing structure. The connection is firm and the overall stress is balanced, which improves the load-bearing capacity of the support structure.

[0016] 4. Convenient and safe construction: The present invention has a reasonable structural design, and all components are made of standardized I-beams, which makes processing convenient and on-site installation efficient; the construction process is standardized, and the deformation of the support structure can be monitored in real time through monitoring and measurement points, which can promptly detect potential safety hazards and ensure construction safety. Attached Figure Description

[0017] Figure 1 This is a cross-sectional view of the intersection of the fan room on the inclined shaft side of the present invention.

[0018] Figure 2 This is a cross-sectional view of the intersection of the right-side tunnel and the fan room of the present invention.

[0019] Figure 3 This is a schematic diagram of the steel arch frame arrangement at the intersection of the present invention.

[0020] Figure 4 This is a completed construction diagram of the steel arch frame at the intersection according to the present invention.

[0021] Figure 5 The outline of the initial concrete breaking in this invention.

[0022] Figure 6 This is a schematic diagram of the cutting of the arch frame at the intersection of the air supply connection channel of the present invention.

[0023] Figure 7 This is a schematic diagram of the installation of a single-sided arch frame according to the present invention.

[0024] Figure 8 This is a schematic diagram of the layout of monitoring and measurement points for the tunnel entrance according to the present invention.

[0025] Figure 9 This is a schematic diagram showing the removal of the initial support arch at the intersection of the fan room and the exhaust duct.

[0026] Figure 10 This is a schematic diagram of the arch frame at the intersection of the fan room and exhaust duct of the present invention.

[0027] The diagram is labeled as follows: 1. Arc-shaped support arch; 2. Vertical support arch; 3. Diagonal brace; 4. Portal frame beam. Detailed Implementation

[0028] The following is in conjunction with the appendix Figures 1-10 The specific embodiments of the present invention will be described in further detail below.

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0030] This embodiment provides a portal steel frame support structure for tunnel intersections. Figure 1The images shown, from left to right, represent the air supply duct gantry, the maintenance passage gantry, and the exhaust duct gantry. Each of these gantry includes a portal steel frame body. The portal steel frame body includes a vertical support arch 2, a portal beam 4, an arc-shaped support arch 1, anchor bolts, and diagonal braces 3. The vertical support arch 2 uses two I28a I-beams, symmetrically arranged on both sides of the portal steel frame body, serving as the vertical support structure. The portal beam 4 is connected to the vertical support arch 2. Multiple arc-shaped support arches 1 are evenly arranged and connected to the portal beam 4, which can be fixed by bolts or welding. The anchor bolts are double-stretched and embedded in the surrounding rock to fix the vertical support arch 2. The diagonal braces 3 use I20a I-beams and are positioned between the portal beam 4 and the vertical support arch 2.

[0031] The main body of the portal steel frame is made of I28a I-beams, and the processing precision meets the requirements of tunnel construction specifications. Specifically, the width of the ventilation connecting tunnel portal frame is 1200 cm and the height is 717.1 cm, the width of the exhaust connecting tunnel portal frame is 2400 cm and the height is 717.1 cm, and the width of the maintenance passage portal frame is 400 cm and the height is 497.5 cm. The dimensions of each portal frame are precisely designed according to the cross-sectional dimensions of the corresponding connecting tunnel to ensure a tight fit with the inner wall of the connecting tunnel.

[0032] The vertical support arch 2 uses two I28a I-beams, symmetrically arranged on both sides of the main body of the portal steel frame. The spacing between the two I-beams matches the width of the portal frame beam 4, ensuring the uniformity of the vertical support. The bottom of the vertical support arch 2 is laid with double-layered 10mm steel plates. The steel plates are sized to match the bottom dimensions of the vertical support arch 2, laid flat and firmly, and closely fitted to the surrounding rock. This serves to disperse the vertical stress transmitted by the vertical support arch 2 and prevent the surrounding rock at the arch foot from being damaged by pressure.

[0033] The anchor bolts are doubled and embedded into the surrounding rock after being drilled with a drilling machine. They are anchored with cement mortar to ensure that the anchor bolts are firmly bonded to the surrounding rock, effectively fixing the vertical support arch 2 and preventing it from shifting laterally.

[0034] The diagonal brace 3 is made of I20a I-beams. Its length is determined according to the distance and installation angle between the portal frame beam 4 and the vertical support arch 2. The two ends of the diagonal brace 3 are fixedly connected to the portal frame beam 4 and the vertical support arch 2 by welding to ensure a firm connection and enhance the lateral displacement resistance of the entire support structure.

[0035] The gantry beam 4 is made of I28a I-beams, and its length is consistent with the width of the corresponding gantry. The gantry beam 4 is bolted to the vertical support arch 2, and the connection is reinforced by welding. The weld quality meets the specifications. The gantry beam 4 is fully welded to the tunnel ventilation room steel arch, forming an integral load-bearing structure to ensure uniform load distribution.

[0036] One monitoring and measurement point is set at the midpoint and one at each end of the gantry beam 4. Strain gauges and displacement sensors are used to monitor the strain and displacement changes of the gantry beam 4 in real time. The monitoring data is transmitted to the monitoring terminal in real time. When abnormal deformation is detected, an early warning is issued in time, so that construction personnel can take reinforcement measures in time.

[0037] Excavation of air supply tunnel The ventilation connection tunnel is 142.88 meters long and has two types of excavation sections, including a 40-meter transition section.

[0038] According to the design drawings, the outline of the portal arch frame of the air supply connection channel was laid out and positioned, and the outline and position were marked with red paint. There are two marking lines: one is the outline of the portal arch frame, and the other is the initial support concrete demolition line. The outline is offset inward by 15 cm from the portal outline to ensure accurate demolition and to minimize damage to the initial support concrete outside the intersection outline.

[0039] Original support treatment of the fan room A hydraulic breaker was used to demolish the concrete arch frame at the intersection of the fan room and the air supply duct. Temporary anchor points for the arch frame were erected 50cm above the portal frame outline before demolishing the initial concrete support. During demolition, the arch frame positions were staggered as much as possible to avoid damaging the original initial support arch frame of the fan room. Simultaneously, the reinforcing mesh and connecting bars were cut off. After completion, the arch frame outline was laid out and marked according to the portal frame outline for subsequent construction.

[0040] Removal of the initial support arch of the fan room To avoid affecting the initial support structure of the wind turbine room, it is strictly forbidden to cut off the original wind turbine room arch frame all at once before installing the portal frame. Instead, the installation should be carried out in a step-by-step manner, cutting off half of the original main tunnel arch frame and installing the other half. When cutting off the original main tunnel initial support arch frame, the cutting should be carried out according to the direction of the tunnel portal arch frame at that location to ensure that the main tunnel arch frame is completely placed on the tunnel portal arch frame and is well stressed.

[0041] Portal arch installation After the arch frame is cut, the portal arch frame is installed. Before installation, the cutting position of the main tunnel arch frame is checked again to ensure accuracy. Once confirmed, the portal arch frame is installed. Immediately after installation, the connection between the main tunnel arch frame and the portal arch frame is welded, with full welding along the contact surface. Simultaneously, temporary vertical supports are installed at the ends of the arch frame. The vertical support arch frame 2 is the same model as the vertical arch frames at both ends. After installation, locking feet are installed in two sets, downwards at a 45° angle. At the same time, the diagonal supports of the portal arch frame are installed and welded securely. After the arch frame installation is complete, the portal arch frame is re-measured to ensure accurate positioning and that it does not encroach on the flared end area. Once the re-measurement is confirmed to be correct, shotcrete application is carried out.

[0042] After the installation of one side of the gantry is completed, continue to dismantle and install the other side of the gantry in the same way as described above.

[0043] After the portal arch frame of the intersection is installed, the initial spraying operation is carried out immediately. At the same time, monitoring and measurement points are set up at the lower part of the portal arch frame. A total of 3 monitoring and measurement points are set up at the surface of the initial support concrete at the lower part of the portal arch frame to observe the settlement of the portal.

[0044] The construction method of the portal steel frame support structure for tunnel intersections in this embodiment utilizes the aforementioned support structure and includes the following steps: S1, the cross section of the fan room at the intersection of the construction tunnel, complete the excavation and initial support of the fan room. After the initial support structure of the fan room is stable, the excavation of the guide tunnels for the air supply connection, exhaust connection and maintenance passage will be carried out. S2. Based on the design positions of the air supply duct gantry, exhaust duct gantry, and maintenance passage gantry, determine the installation position and height of the vertical support arch 2 corresponding to each gantry, mark the positions, and clean up any loose debris at the marked positions. S3. Lay double-layer 10mm steel plates at the installation position of the cleaned vertical support arch 2 to complete the arch foot treatment. Then, break the initial support arch at the corresponding position of the fan room. After the breakage is completed, hoist the two vertical support arch 2 made of I28a I-beams to the designated position and adjust them into place. S4. After the vertical support arch 2 is installed, double anchor bolts are installed at its bottom. The anchor bolts are embedded into the surrounding rock. The position of the vertical support arch 2 is re-measured. After confirming that the position is correct, spray concrete is applied to the outside of the vertical support arch 2 so that the spray concrete layer wraps around the vertical support arch 2 and fits tightly with the surrounding rock, thus completing the fixation of the vertical support arch 2. S5. After the vertical support arch 2 is reinforced, the portal frame beam 4 of the main body of the portal steel frame is hoisted, and the portal frame beam 4 is connected and fixed to the vertical support arch 2 by arch frame bolts and welding. At the same time, the portal frame beam 4 is welded to the wind turbine room steel arch to form an integral load-bearing structure. Monitoring and measurement points are set at the midpoint and both ends of the portal frame beam 4. S6. After the gantry beam 4 is installed, I20a diagonal brace 3 is added between the gantry beam 4 and the vertical support arch 2. The installation position of the diagonal brace 3 is adjusted to ensure that it avoids the initial support arch of the air supply connection duct and the air exhaust connection duct and does not invade the cross-sectional space of each connection duct. Then, the two ends of the diagonal brace 3 are welded and fixed to the gantry beam 4 and the vertical support arch 2 respectively. After the installation of S7, the main body of the portal steel frame, the vertical support arch frame 2, and the diagonal brace 3 are completed, a comprehensive inspection of the entire portal steel frame support structure is carried out to confirm that all connection parts are firm, the position is accurate, and the monitoring and measurement points are normal. Then, shotcrete operation is carried out to comprehensively spray the portal steel frame support structure and the surrounding rock. After the shotcrete layer reaches the design strength, the entire support construction is completed.

[0045] Specifically, the construction of the ventilation room section at the tunnel intersection will begin first, completing the excavation and initial support work. After the initial support structure of the ventilation room is stable, the excavation of the guide tunnels for the air supply connecting tunnel, exhaust connecting tunnel, and maintenance passage will proceed. Based on the design positions of the air supply connecting tunnel gantry, exhaust connecting tunnel gantry, and maintenance passage gantry, the installation positions and heights of the corresponding vertical support arches 2 for each gantry will be determined, marked, and the loose debris at the marked positions will be cleaned. A double layer of 10mm [material / material] will then be laid at the cleaned installation positions of the vertical support arches 2. Steel plates were used to complete the arch foot treatment. Then, the initial support arch frame at the corresponding location of the fan room was dismantled. After dismantling, two vertical support arch frames 2 made of I28a I-beams were hoisted to the designated position and adjusted into place. After the vertical support arch frames 2 were installed, double-locking anchor rods were installed at their bottom, embedded into the surrounding rock. The position of the vertical support arch frames 2 was re-measured. After confirming that the position was correct, sprayed concrete was applied to the outside of the vertical support arch frames 2, ensuring the sprayed concrete layer completely enveloped the vertical support arch frames 2 and tightly adhered to the surrounding rock, thus completing the vertical support. Fixing the arch support 2; After the vertical support arch support 2 is reinforced, hoist the portal frame crossbeam 4 of the main body of the portal steel frame, connect and weld the portal frame crossbeam 4 to the vertical support arch support 2 with arch frame bolts, and weld the portal frame crossbeam 4 to the steel arch support of the fan room to form an integral load-bearing structure. Set monitoring and measurement points at the midpoint and both ends of the portal frame crossbeam 4; After the portal frame crossbeam 4 is installed, add I20a diagonal braces 3 between the portal frame crossbeam 4 and the vertical support arch support 2, and adjust the installation position of the diagonal braces 3 to ensure that they avoid the air supply connection duct. The initial support arch of the ventilation connecting passage does not encroach on the cross-sectional space of each connecting passage. Then, the two ends of the diagonal brace 3 are welded and fixed to the portal frame beam 4 and the vertical support arch 2 respectively. After the main body of the portal steel frame, the vertical support arch 2 and the diagonal brace 3 are installed, the entire portal steel frame support structure is fully inspected to confirm that all connection parts are firm, the position is accurate and the monitoring and measurement points are normal. Then, shotcrete operation is carried out to fully spray the portal steel frame support structure and the surrounding rock. After the shotcrete layer reaches the design strength, the entire support construction is completed.

[0046] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, such that a process, article, or apparatus / device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to those processes, articles, or apparatus / devices.

[0047] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A portal steel frame support structure for a tunnel crossing, characterized in that, The system includes a supply air duct gantry, a maintenance passage gantry, and an exhaust air duct gantry. Each of these gantry includes a portal steel frame body. The portal steel frame body includes a vertical support arch (2), a portal beam (4), an arc-shaped support arch (1), anchor rods, and diagonal braces (3). The vertical support arch (2) uses two I28a I-beams, symmetrically arranged on both sides of the portal steel frame body, serving as the vertical support structure of the portal steel frame body. The portal beam (4) is connected to the vertical support arch (2), and the arc-shaped support arch (1) is connected to the portal beam (4). The anchor rods are doubled and embedded in the surrounding rock to fix the vertical support arch (2). The diagonal braces (3) use I20a I-beams and are located between the portal beam (4) and the vertical support arch (2).

2. Portal steel arch support structure for tunnel crossings according to claim 1, characterized in that, The dimensions of the three sets of portal steel frame main bodies are as follows: the width of the air supply connecting passage portal frame is 1200 cm and the height is 717.1 cm; the width of the exhaust connecting passage portal frame is 2400 cm and the height is 717.1 cm; and the width of the maintenance passage portal frame is 400 cm and the height is 497.5 cm.

3. Portal steel arch support structure for tunnel crossings according to claim 1, characterized in that, The bottom of the vertical support arch (2) is provided with a double layer of 10 mm steel plate, which is laid between the bottom of the vertical support arch (2) and the surrounding rock.

4. Portal steel arch support structure for tunnel crossings according to claim 1, characterized in that, The gantry beam (4) and the vertical support arch (2) are connected and fixed by arch bolts and welding.

5. The portal steel arch support structure for a tunnel crossing according to claim 1, characterized in that, The gantry beam (4) is equipped with monitoring and measurement points at its midpoint and both ends for real-time monitoring of the deformation of the gantry beam (4).

6. The portal steel arch support structure for a tunnel crossing according to claim 1, characterized in that, The two ends of the diagonal brace (3) are fixedly connected to the portal frame beam (4) and the vertical support arch (2) by welding.

7. A method for construction of portal steel support structures for tunnel crossings, characterized in that: This is achieved using the portal steel frame support structure for tunnel intersections as described in claim 1, comprising the following steps: S1, the cross section of the fan room at the intersection of the construction tunnel, complete the excavation and initial support of the fan room. After the initial support structure of the fan room is stable, the excavation of the guide tunnels for the air supply connection, exhaust connection and maintenance passage will be carried out. S2. Based on the design positions of the air supply duct gantry, exhaust duct gantry and maintenance passage gantry, determine the installation position and height of the vertical support arch (2) corresponding to each gantry, mark the position and clean up the loose residue at the marked position. S3. Lay double-layer 10mm steel plates at the installation position of the cleaned vertical support arch (2) to complete the arch foot treatment. Then break the initial support arch at the corresponding position of the fan room. After the break is completed, hoist the two I28a I-beams made of vertical support arch (2) to the designated position and adjust them into place. S4. After the vertical support arch (2) is installed, double anchor bolts are installed at its bottom. The anchor bolts are embedded into the surrounding rock. The position of the vertical support arch (2) is re-measured. After confirming that the position is correct, spraying is carried out on the outside of the vertical support arch (2) so that the sprayed layer wraps the vertical support arch (2) and fits tightly with the surrounding rock, thus completing the fixation of the vertical support arch (2). S5. After the vertical support arch (2) is reinforced, the portal frame beam (4) of the main body of the portal steel frame is hoisted, and the portal frame beam (4) and the vertical support arch (2) are connected and fixed by arch bolts and welding. At the same time, the portal frame beam (4) is welded to the wind turbine room steel arch to form an overall load-bearing structure. Monitoring and measurement points are set at the midpoint and both ends of the portal frame beam (4). S6. After the gantry beam (4) is installed, I20a diagonal brace (3) is added between the gantry beam (4) and the vertical support arch (2). The installation position of the diagonal brace (3) is adjusted to ensure that it avoids the initial support arch of the air supply and exhaust ducts and does not invade the cross-sectional space of each duct. Then, the two ends of the diagonal brace (3) are welded and fixed to the gantry beam (4) and the vertical support arch (2) respectively. After the installation of the main body of the portal steel frame, the vertical support arch frame (2), and the diagonal brace (3) is completed, a comprehensive inspection of the entire portal steel frame support structure is carried out to confirm that the connection parts are firm, the position is accurate, and the monitoring and measurement points are normal. Then, the shotcrete operation is carried out to spray the portal steel frame support structure and the surrounding rock. After the shotcrete layer reaches the design strength, the entire support construction is completed.

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