A secondary lining construction method for large-section underground fan room in extra-long highway tunnel

Abstract

The present invention provides a method for constructing a secondary lining of a large-section underground wind machine room in an extra-long highway tunnel, which belongs to the technical field of tunnel engineering, including S1, re-measurement of the initial support section, S2, construction of a waterproof layer, S3, assembly of a secondary lining stand and a steel bar installation stand, S4, installation of secondary lining steel bars, S5, installation of corbel embedded parts, S6, assembly of formwork, S7, pouring of secondary lining concrete, and S8, concrete curing. The method pours secondary lining concrete at different heights, decomposing the primary stress problem in the large-section secondary lining concrete pouring process into two times, reducing the requirements for the trolley during construction, thereby reducing the project cost; combined with the intersection width and its distribution on both sides of the underground wind machine room, the single-plate secondary lining construction range is reasonably divided, avoiding the unfavorable situation that the annular construction joint is arranged in the intersection range.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel engineering, and in particular relates to a secondary lining construction method for a large-section underground fan room in an extra-long highway tunnel. Background Art

[0002] With the continuous development of tunnel construction technology, the number of extra-long tunnels is increasing. Most of the extra-long highway tunnels are equipped with inclined shafts and underground fan rooms to meet the ventilation needs during the operation period. Because the underground fan room needs to be equipped with large equipment such as ventilators and overhead cranes, the fan room is designed to be high and have a large span. Multiple intersections are set up to connect with various connecting air ducts, and there is an asymmetric setting at the intersection. It is necessary to avoid the unfavorable situation of the circumferential construction joint being arranged at the arch of the intersection, which seriously increases the difficulty of construction. At the same time, due to the short length of the fan room, the cost of using the traditional integral hydraulic trolley to construct the secondary lining is relatively high. Summary of the invention

[0003] The purpose of the present invention is to provide a secondary lining construction method for a large-section underground fan room in an extra-long highway tunnel, which can avoid the unfavorable situation that the annular construction joint is arranged in the intersection range, and is equipped with a secondary lining stand and a steel bar installation frame to reduce the project cost.

[0004] The present invention provides a method for constructing a secondary lining of a large-section underground fan room in an extra-long highway tunnel, comprising the following steps:

[0005] S1, re-measurement of the initial branch section

[0006] Before installing the waterproof board, re-measure the primary support section of the underground fan room to ensure that the secondary lining thickness meets the design requirements;

[0007] S2, waterproof layer construction

[0008] Before laying the waterproof layer, the protrusions on the primary support surface are cut and smoothed with mortar, and the looseness of the waterproof layer meets the design requirements;

[0009] Several steel bar joints are reserved at the top of each straight wall on each side of the secondary lining of each slab. The steel bar joints pass through the waterproof layer, one end is welded to the chiseled initial I-beam steel frame, and the other end is welded to the secondary lining main reinforcement. The holes where the steel bar joints pass through the waterproof layer are sealed.

[0010] S3, assemble the secondary lining stand and steel bar installation frame

[0011] In the underground fan room, the walking track is laid along the longitudinal direction of the underground fan room, and the secondary lining stand and the steel bar installation frame are assembled;

[0012] After the assembly is completed, the second lining stand is moved to the second lining position of the first plate, and the steel bar installation frame is moved to the end of the second lining stand to form a parallel operation mode;

[0013] S4, Secondary lining reinforcement installation

[0014] The steel bars are installed according to the designed steel bar model and spacing. The secondary lining steel bars of each plate are installed and formed in one go according to the full ring. The secondary lining main bars are welded firmly with several reserved steel bar joints at the top of the vertical wall. The secondary lining steel bars of the first plate are installed using the secondary lining stand, and the other secondary lining steel bars are installed using the steel bar installation stand.

[0015] S5, installation of corbel embedded parts

[0016] Measure the height of the corbel embedded parts on the annular main reinforcement on both sides of the secondary lining, and weld the corbel embedded parts to the secondary lining reinforcement firmly according to the designed spacing;

[0017] S6, template assembly

[0018] After the installation of the second lining steel bars of the first plate is completed, the second lining stand formwork is assembled. The second lining stand formwork frame is connected to the second lining stand through a screw, and the second lining stand formwork is reinforced and demoulded through the screw;

[0019] S7, secondary lining concrete pouring

[0020] The second lining of each slab is poured twice according to the height, the first pouring to the top of the vertical wall, and the second time to complete the arch concrete pouring;

[0021] When the longitudinal coverage length of the secondary lining rack fails to completely cover the intersections on both sides of the underground fan room, a vertical wall formwork and a vertical wall formwork frame for supporting the vertical wall formwork are set at the vertical wall position of the intersection outside the longitudinal coverage length range of the secondary lining rack. The vertical wall formwork is provided with grouting holes and working windows. The setting height and length principle of the vertical wall formwork are: when the secondary lining construction within the intersection range is completed at one time, the annular construction joint of the secondary lining is avoided to appear at the intersection arch;

[0022] S8, concrete curing.

[0023] In step S7, when the concrete is poured to the top of the vertical wall, a longitudinal steel plate water stop is reserved, and before the arch concrete is poured, the floating slurry is removed from the concrete on the top of the vertical wall until the aggregate is exposed.

[0024] Furthermore, the secondary lining frame includes a main portal frame I, a longitudinal bottom beam I, a longitudinal connecting beam I, a longitudinal diagonal brace I, a top working platform I and a lateral working platform I; the net height of the main portal frame I is adapted to the height of the secondary lining vertical wall, including a column I, an upper crossbeam I, a middle crossbeam, a vertical support, a diagonal brace I and a transverse support, the tops of the two columns I are connected by an upper crossbeam I, the middles of the two columns I are connected by a middle crossbeam, the middles of the upper crossbeam I and the middle crossbeam are connected by a vertical support, the columns I and the upper crossbeam I and the columns I and the middle crossbeam are connected by diagonal brace I, and the columns I and the diagonal brace I are connected by a transverse support; multiple main portal frames I are arranged along the longitudinal direction of the underground fan room. The main door frames Ⅰ are arranged in the longitudinal direction, the column Ⅰ is connected by the longitudinal bottom beam Ⅰ and the longitudinal connecting beam Ⅰ, the longitudinal bottom beam Ⅰ is located at the bottom end of the column Ⅰ, the longitudinal connecting beam Ⅰ is located above the longitudinal bottom beam Ⅰ, and a longitudinal diagonal brace Ⅰ is arranged between the columns Ⅰ of two adjacent main door frames Ⅰ; the longitudinal bottom beam Ⅰ is provided with a walking wheel Ⅰ matched with the walking track and a walking wheel motor Ⅰ for driving the walking wheel Ⅰ to walk; the top workbench Ⅰ includes a top frame Ⅰ arranged on the upper crossbeam Ⅰ and a plate longitudinally laid on multiple top frames Ⅰ; the lateral workbench Ⅰ includes a side crossbeam Ⅰ arranged on the outside of the column Ⅰ and a plate longitudinally laid on multiple side crossbeams Ⅰ, and the lateral workbench Ⅰ is provided with a working ladder.

[0025] Furthermore, the steel bar installation frame includes a main portal frame II, a longitudinal bottom beam II, a longitudinal connecting beam II, a longitudinal diagonal brace II, a top workbench II and a lateral workbench II; the main portal frame II includes a column II, an upper crossbeam II and a diagonal brace II; the tops of the two columns II are connected by an upper crossbeam II, and the columns II and the upper crossbeam II are connected by a diagonal brace II; multiple main portal frames II are arranged along the longitudinal direction of the underground fan room, the columns II are connected by the longitudinal bottom beam II and the longitudinal connecting beam II, the longitudinal bottom beam II is located at the bottom end of the column II, and the longitudinal connecting beam II is located at the longitudinal bottom Above beam Ⅱ, a longitudinal diagonal brace Ⅱ is arranged between the columns Ⅱ of two adjacent main portal frames Ⅱ; the longitudinal bottom beam Ⅱ is provided with a walking wheel Ⅱ cooperating with the walking track and a walking wheel motor Ⅱ for driving the walking wheel Ⅱ to walk; the top workbench Ⅱ includes a top frame Ⅱ arranged on the upper crossbeam Ⅱ and a plate longitudinally laid on multiple top frames Ⅱ; the lateral workbench Ⅱ includes a side crossbeam Ⅱ arranged on the outside of the column Ⅱ and a plate longitudinally laid on multiple side crossbeams Ⅱ; the side crossbeam Ⅱ and the column Ⅱ are connected by a diagonal brace Ⅲ.

[0026] The present invention has the following beneficial effects:

[0027] 1. Pour the secondary lining concrete at different heights, decomposing the primary force problem in the large-section secondary lining concrete pouring process into two times, reducing the requirements for the trolley during construction, thereby reducing the project cost;

[0028] 2. Considering the width of the intersection and its distribution on both sides of the underground fan room, the single-slab secondary lining construction range is reasonably divided to avoid the unfavorable situation of arranging the annular construction joint in the intersection range;

[0029] 3. The materials used for the processing of the secondary lining stand and the steel bar installation frame are all conventional materials on site, which are convenient to obtain, simple in processing technology and low in cost;

[0030] 4. The secondary lining stand has a simple structure, stable force, and is easy to disassemble and construct;

[0031] In summary, the present invention enriches tunnel construction technology and has extremely broad promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 This is a flow chart of the secondary lining construction method for large-section underground fan rooms in extra-long highway tunnels;

[0034] Figure 2 This is the main view of the secondary lining stand (before installing the formwork);

[0035] Figure 3 This is the main view of the secondary lining stand (after installing the template);

[0036] Figure 4 This is the side view of the secondary lining stand (before installing the formwork);

[0037] Figure 5 This is the main view of the steel bar installation frame;

[0038] Figure 6 This is a schematic elevation diagram of the intersection of the underground fan room;

[0039] Figure 7 It is a plan view of the pouring sequence of the secondary lining divided into panels and heights;

[0040] Figure 8 This is the pouring sequence diagram for the second lining of each slab.

[0041] Icons: longitudinal bottom beam Ⅰ101, longitudinal connecting beam Ⅰ102, longitudinal diagonal brace Ⅰ103, column Ⅰ104, upper crossbeam Ⅰ105, middle crossbeam 106, vertical support 107, diagonal brace Ⅰ108, transverse support 109, walking wheel Ⅰ110, walking wheel motor Ⅰ111, top frame Ⅰ112, side crossbeam Ⅰ113, working ladder 114;

[0042] Column II 201, upper cross beam II 202, diagonal brace II 203, longitudinal bottom beam II 204, running wheel II 205, top frame II 206, side cross beam II 207, diagonal brace III 208;

[0043] Walking track 300;

[0044] Second lining stand template 401, second lining stand template frame 402, lead screw 403, working window preset position 404;

[0045] Second lining inner contour 501, intersection 502, first pouring 503, first pouring 504, corbel embedded parts 505, top of vertical wall (dividing line of two pourings) 506, center line of underground fan room 507, one side of inclined shaft 508, one side of main hole 509, second lining stand construction end 510;

[0046] Vertical wall formwork frame 600. DETAILED DESCRIPTION

[0047] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. 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.

[0048] Taking a long highway tunnel as an example, the construction method of the secondary lining of a large-section underground fan room in a long highway tunnel is explained in detail. The inner contour 501 of the secondary lining of the underground fan room is 126m (length) × 10m (width) × 13m (height), the thickness of the secondary lining is 60cm, and the vertical wall is 9.25m high. There are 12 intersections 502 on the vertical walls on both sides, and 1 intersection 502 at each end. At 8m high on the vertical walls on both sides, there are embedded brackets 505 for overhead cranes, arranged at a spacing of 4m, with a total of 33 pairs, and the brackets are all at the same elevation.

[0049] The method comprises the following steps.

[0050] 1. Re-measurement of the initial support section: Re-measure the initial support section of the underground fan room before hanging the waterproof board to ensure that the secondary lining thickness meets the design requirements.

[0051] 2. Waterproof layer construction: Before laying the waterproof layer, the protrusions such as the steel bar heads on the surface of the initial support should be cut and smoothed with mortar. The looseness of the waterproof layer should meet the design requirements.

[0052] Due to the special characteristics of the underground wind room with high height and large span, in order to ensure the overall stability of the secondary lining steel bars, two steel bar joints are reserved at the top of each side wall of each plate of the secondary lining. The steel bar joints pass through the waterproof layer, one end is welded to the chiseled initial I-beam steel frame, and the other end is welded to the secondary lining main reinforcement, and the holes through which the steel bars pass through the waterproof layer are sealed.

[0053] 3. Assemble the secondary lining frame and the steel bar installation frame: In the underground fan room, lay the walking track along the longitudinal direction of the underground fan room, and assemble the secondary lining frame and the steel bar installation frame.

[0054] The length of the secondary lining platform is 7.5m, including the main portal frame Ⅰ, the longitudinal bottom beam Ⅰ101, the longitudinal connecting beam Ⅰ102, the longitudinal diagonal brace Ⅰ103, the top working platform Ⅰ and the side working platform Ⅰ.

[0055] The net height of the main portal frame I is adapted to the height of the secondary lining vertical wall, including the column I104, the upper crossbeam I105, the middle crossbeam 106, the vertical support 107, the diagonal support I108 and the transverse support 109, all of which are made of H20 steel and connected to each other by high-strength bolts. The tops of the two columns I104 are connected by the upper crossbeam I105, the middles of the two columns I104 are connected by the middle crossbeam 106, the middles of the upper crossbeam I105 and the middle crossbeam 106 are connected by the vertical support 107, the column I104 and the upper crossbeam I105 and the column I104 and the middle crossbeam 106 are connected by the diagonal support I108, and the column I104 and the diagonal support I104 are connected by the transverse support 109.

[0056] Six main portal frames I are arranged along the longitudinal direction of the underground fan room, with a spacing of 1.5m between adjacent main portal frames I and a span width of 7.2m. Column I104 is connected by longitudinal bottom beam I101 and longitudinal connecting beam I102. Longitudinal bottom beam I101 is made of double-jointed I25 I-beams, 8.0m long, and connected to the bottom of column I104 by high-strength bolts. Three longitudinal connecting beams I102 are all located above the longitudinal bottom beam I101, using I18 I-beams, and connected to column I104 by high-strength bolts. A longitudinal diagonal brace I103 is arranged between the columns I104 of two adjacent main portal frames I. The longitudinal diagonal brace I103 is located between the longitudinal bottom beam I101 and the longitudinal connecting beam I102 and between two adjacent longitudinal connecting beams I102, using 10# channel steel. The longitudinal bottom beam Ⅰ101 is provided with a traveling wheel Ⅰ110 matched with the traveling track 300 and a traveling wheel motor Ⅰ111 for driving the traveling wheel Ⅰ110 to travel.

[0057] The top workbench I includes a top frame I112 arranged on the upper crossbeam I105 and a plate material longitudinally laid on multiple top frames I112. The top frame I112 is a convex structure assembled from H20 steel sections, and the plate material is a 5-cm thick wooden board.

[0058] The lateral workbench I includes a lateral beam I113 disposed outside the column I104 and a plate longitudinally laid on a plurality of lateral beams I113. The lateral workbench I is provided with a working ladder 114. The specific distribution of the working ladder 114 is adjusted according to actual use. The lateral beam I113 is made of I22 I-beam.

[0059] The steel bar installation frame includes the main portal frame II, the longitudinal bottom beam II204, the longitudinal connecting beam II, the longitudinal diagonal brace II, the top workbench II and the lateral workbench II; the main portal frame II includes the column II201, the upper crossbeam II202 and the diagonal brace II203. The column II201 and the upper crossbeam II202 are made of I20 I-beams, and the diagonal brace II203 is made of I14 I-beams, which are connected to each other by high-strength bolts. The tops of the two columns II201 are connected by the upper crossbeam II202, and the column II201 and the upper crossbeam II202 are connected by the diagonal brace II203. Multiple main portal frames II are arranged along the longitudinal direction of the underground fan room, and are connected in the same way as the main portal frame I. The columns II 201 are connected by the longitudinal bottom beam II 204 and the longitudinal connecting beam II. The longitudinal bottom beam II 204 is located at the bottom of the column II 201, and the longitudinal connecting beam II is located above the longitudinal bottom beam II 204. A longitudinal diagonal brace II is arranged between the columns II 201 of two adjacent main portal frames II. The longitudinal bottom beam II 204 is provided with a walking wheel II 205 that cooperates with the walking track and a driving wheel Ⅱ205 is a walking wheel motor Ⅱ for walking; the top workbench Ⅱ includes a top frame Ⅱ206 arranged on the upper crossbeam Ⅱ202 and a plate longitudinally laid on multiple top frames Ⅱ206, and the top frame Ⅱ206 is a convex structure composed of 48 steel pipes; the lateral workbench Ⅱ includes a side crossbeam Ⅱ207 arranged on the outside of the column Ⅱ201 and a plate longitudinally laid on multiple side crossbeams Ⅱ207; the side crossbeam Ⅱ207 and the column Ⅱ201 are connected by a diagonal brace Ⅲ208.

[0060] After the assembly is completed, the second lining stand is moved to the second lining position of the first plate, and the steel bar installation frame is moved to the end of the second lining stand to form a parallel operation mode.

[0061] 4. Secondary lining reinforcement installation: The reinforcement installation operation is carried out according to the designed reinforcement model and spacing. The secondary lining reinforcement of each plate is installed and formed in one full ring. The secondary lining main reinforcement and the reserved reinforcement joint are welded firmly at the top of the vertical wall. The secondary lining reinforcement of the first plate is installed using the secondary lining stand, and the other secondary lining reinforcements are installed using the reinforcement installation frame.

[0062] 5. Installation of corbel embedded parts: Measure the height of the corbel embedded parts on the circumferential main reinforcement on both sides of the secondary lining, and weld the corbel embedded parts to the secondary lining steel bars firmly according to the designed spacing.

[0063] 6. Formwork assembly: After the installation of the second lining steel bars of the first plate is completed, the second lining stand formwork is assembled. The second lining stand formwork 401 is assembled from 1.5m long steel forms, and the second lining stand formwork skeleton 402 is made of I18 I-beams, arranged in the same ring as the H20 steel main portal frame I. 18 screws 403 are set in each main portal frame I circle, and the reinforcement and demoulding of the second lining stand formwork 401 are completed through the screws 403. Grouting holes and working windows are set on the second lining stand formwork 401. Two grouting holes are set at the top, and the working windows are set at 4.5m and 9m from the bottom. Three working windows are set on each side and each layer of the second lining stand.

[0064] 7. Secondary lining concrete pouring: The secondary lining of each plate is poured twice according to the height, the first pouring to the top of the vertical wall, and the second pouring of the arch concrete. In order to avoid the unfavorable situation that the secondary lining circumferential construction joint appears in the arch of the intersection, combined with the width of the intersection 502 and its distribution on both sides of the underground fan room, when the longitudinal coverage length of the secondary lining stand fails to completely cover the intersection 502 on both sides of the underground fan room, at the intersection 502 located outside the longitudinal coverage length of the secondary lining stand, an I16 I-beam is added as the vertical wall formwork skeleton 600, and a 1.5m long steel formwork is also installed as the vertical wall formwork. The I16 I-beam is reinforced by steel pipe diagonal bracing and bracing. The setting height and length principle of the vertical wall formwork are: while the secondary lining in the intersection range is completed at one time, the reserved position of the circumferential construction joint is taken into account to avoid the secondary lining circumferential construction joint appearing in the intersection arch. Grouting holes and working windows are also set on the vertical wall formwork. When pouring concrete to the top of the vertical wall, reserve a longitudinal steel plate waterstop. Before pouring the arch concrete, remove the floating slurry from the top of the vertical wall until the aggregate is exposed.

[0065] like Figure 7 and 8 As shown, 2-28 is the moving direction of the second lining stand. When the second lining stand is located at position No. 2, the second lining stand template 401 is installed. Since the intersection 502 on both sides of position No. 2 is outside the longitudinal coverage length of the second lining stand, a vertical wall template skeleton 600 and a vertical wall template are added at the vertical wall position where the intersection 502 is outside the longitudinal coverage length of the second lining stand. Position No. 1 is poured first, and then position No. 2 is poured. The vertical wall template skeleton 600 and the vertical wall template at position No. 1 are removed, the second lining stand is moved to position No. 3, and position No. 3 is poured. The second lining stand is moved to position No. 5, and position No. 4 is poured first, and then position No. 5, and so on.

[0066] 8. Concrete curing: The secondary lining concrete will be demoulded after reaching 85% of the design strength and will continue to be cured for 14 days after demoulding.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for constructing a secondary lining of a large-section underground fan room in a highway extra-long tunnel, characterized in that: The steps include: S1, re-measurement of the initial branch section S2, waterproof layer construction Several steel bar joints are reserved at the top of each straight wall on each side of the secondary lining of each slab. The steel bar joints pass through the waterproof layer, one end is welded to the chiseled initial I-beam steel frame, and the other end is welded to the secondary lining main reinforcement. The holes where the steel bar joints pass through the waterproof layer are sealed. S3, assemble the secondary lining stand and steel bar installation frame In the underground fan room, the walking track is laid along the longitudinal direction of the underground fan room, and the secondary lining stand and the steel bar installation frame are assembled; The secondary lining platform includes main portal frame Ⅰ, longitudinal bottom beam Ⅰ, longitudinal connecting beam Ⅰ, longitudinal diagonal brace Ⅰ, top working platform Ⅰ and lateral working platform Ⅰ; The net height of the main portal frame Ⅰ is adapted to the height of the secondary lining vertical wall, including column Ⅰ, upper crossbeam Ⅰ, middle crossbeam, vertical support, diagonal brace Ⅰ and transverse support. The tops of the two columns Ⅰ are connected by the upper crossbeam Ⅰ, the middles of the two columns Ⅰ are connected by the middle crossbeam, the middles of the upper crossbeam Ⅰ and the middle crossbeam are connected by the vertical support, the column Ⅰ and the upper crossbeam Ⅰ as well as the column Ⅰ and the middle crossbeam are connected by the diagonal brace Ⅰ, and the column Ⅰ and the diagonal brace Ⅰ are connected by the transverse support; Multiple main portal frames I are arranged along the longitudinal direction of the underground fan room, and the columns I are connected by longitudinal bottom beams I and longitudinal connecting beams I. The longitudinal bottom beams I are located at the bottom of the columns I, and the longitudinal connecting beams I are located above the longitudinal bottom beams I. A longitudinal diagonal brace I is arranged between the columns I of two adjacent main portal frames I. The longitudinal bottom beam I is provided with a travel wheel I matched with the travel track and a travel wheel motor I for driving the travel wheel I to travel; The top workbench I comprises a top frame I arranged on an upper crossbeam I and a plate material longitudinally laid on a plurality of top frames I; The lateral workbench I comprises a lateral crossbeam I arranged outside the column I and a plate material longitudinally laid on a plurality of lateral crossbeams I, and the lateral workbench I is provided with a working ladder; The steel bar installation frame includes main portal frame II, longitudinal bottom beam II, longitudinal connecting beam II, longitudinal diagonal brace II, top working platform II and lateral working platform II; The main portal frame II includes column II, upper crossbeam II and diagonal brace II; The tops of the two columns Ⅱ are connected by an upper crossbeam Ⅱ, and the columns Ⅱ and the upper crossbeam Ⅱ are connected by a diagonal brace Ⅱ; Multiple main portal frames II are arranged along the longitudinal direction of the underground fan room, and the columns II are connected by longitudinal bottom beams II and longitudinal connecting beams II. The longitudinal bottom beam II is located at the bottom of the columns II, and the longitudinal connecting beam II is located above the longitudinal bottom beam II. A longitudinal diagonal brace II is arranged between the columns II of two adjacent main portal frames II. The longitudinal bottom beam II is provided with a traveling wheel II matched with the traveling track and a traveling wheel motor II for driving the traveling wheel II to travel; The top workbench II includes a top frame II arranged on the upper crossbeam II and a plate material longitudinally laid on the multiple top frames II; The lateral workbench II includes a side crossbeam II arranged outside the column II and a plate material longitudinally laid on a plurality of side crossbeams II; The side crossbeam II and the column II are connected by diagonal brace III. After the assembly is completed, the second lining stand is moved to the second lining position of the first plate, and the steel bar installation frame is moved to the end of the second lining stand to form a parallel operation mode. S4, Secondary lining reinforcement installation The steel bars are installed according to the designed steel bar model and spacing. The secondary lining steel bars of each plate are installed and formed in one go according to the full ring. The secondary lining main bars are welded firmly with several reserved steel bar joints at the top of the vertical wall. The secondary lining steel bars of the first plate are installed using the secondary lining stand, and the other secondary lining steel bars are installed using the steel bar installation stand. S5, installation of corbel embedded parts Measure the height of the corbel embedded parts on the annular main reinforcement on both sides of the secondary lining, and weld the corbel embedded parts to the secondary lining reinforcement firmly according to the designed spacing; S6, template assembly After the installation of the second lining steel bars of the first plate is completed, the second lining stand formwork is assembled. The second lining stand formwork frame is connected to the second lining stand through a screw, and the second lining stand formwork is reinforced and demoulded through the screw; S7, secondary lining concrete pouring The second lining of each slab is poured twice according to the height, the first pouring to the top of the vertical wall, and the second time to complete the concrete pouring of the arch; When the longitudinal coverage length of the secondary lining stand fails to completely cover the intersections on both sides of the underground fan room, a vertical wall formwork and a vertical wall formwork frame for supporting the vertical wall formwork are set at the vertical wall position of the intersection outside the longitudinal coverage length of the secondary lining stand. The vertical wall formwork is provided with grouting holes and working windows. The setting height and length principle of the vertical wall formwork are as follows: when the secondary lining within the intersection range is constructed at one time, the annular construction joint of the secondary lining is avoided to appear in the arch part of the intersection.

2. The method for constructing the secondary lining of a large-section underground fan room in a highway extra-long tunnel according to claim 1 is characterized in that: In step S1, the primary support section of the underground fan room is re-measured before the waterproof board is installed to ensure that the secondary lining thickness meets the design requirements.

3. The method for constructing the secondary lining of a large-section underground fan room in a highway extra-long tunnel according to claim 1 is characterized in that: In step S2, before laying the waterproof layer, the protrusions on the surface of the primary support are cut and smoothed with mortar, and the looseness of the waterproof layer meets the design requirements.

4. The method for constructing the secondary lining of a large-section underground fan room in a highway extra-long tunnel according to claim 1 is characterized in that: In step S7, when the concrete is poured to the top of the vertical wall, a longitudinal steel plate water stop is reserved, and before the arch concrete is poured, the floating slurry is removed from the concrete on the top of the vertical wall until the aggregate is exposed.

5. The method for constructing the secondary lining of a large-section underground fan room in a highway extra-long tunnel according to claim 1 is characterized in that: The method further includes step S8, concrete curing.

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