A large underground power generation cavern side wall bus hole lock mouth supporting structure and construction method

Abstract

The application belongs to the technical field of underground protective structure, and particularly relates to a large underground power generation cavern side wall bus tunnel lock opening supporting structure and a construction method. The large underground power generation cavern side wall bus tunnel lock opening supporting structure comprises an H-shaped steel bottom beam located at the bottom of a side wall bus tunnel and a plurality of H-shaped steel arches, the surfaces of the H-shaped steel bottom beam and the H-shaped steel arches are respectively uniformly distributed with a plurality of anchor bars, a reinforced concrete plate is installed between the H-shaped steel arches, the outer surface of the reinforced concrete plate is provided with a meshed concrete spraying filler, a baffle is arranged between the H-shaped steel arches adjacent to the downstream wall of the power generation cavern and the rock wall of the side wall bus tunnel, and the baffle, the H-shaped steel arches, the reinforced concrete plate and the rock wall of the side wall bus tunnel are filled with concrete. The structure adopts a prefabricated reinforced concrete plate, can be quickly and conveniently constructed, adopts an H-shaped steel frame matched with anchor bars and prestressed anchor cables, can provide high rigidity and strength, and can prevent the generation of cracks and excessive deformation of the tunnel opening rock mass.

Description

Technical Field

[0001] This invention belongs to the field of underground protective structure technology, and specifically relates to a support structure and construction method for the busbar opening of the side wall of a large underground power generation chamber. Background Technology

[0002] Pumped storage power plant buildings are typically located within large underground caverns in rock masses. Due to topographical constraints, some of these large caverns have spans exceeding 25.0m, significant depths, and poor geological conditions, with some reaching depths of 500m. This results in high initial ground stress, with the surrounding rock generally classified as Class III and partially Class IV, leading to a rock strength-stress ratio of 2.5–4.0. Several busbar tunnels with excavation spans of approximately 10.0m pass through the downstream high sidewalls of these large underground caverns, which can reduce the strength and rigidity of the walls. Rock anchor beams, designed to support large bridge cranes, are positioned approximately 8.0–9.0m above the busbar tunnels. Insufficient support strength within a certain range around the busbar tunnel openings can exacerbate rock wall deformation during excavation below the busbar tunnels, causing excessive settlement and deformation of the rock anchor beams, potentially leading to cracking and jeopardizing their safe operation.

[0003] Existing support methods for such tunnel openings include two main types: First, steel arch frames with shotcrete. This is simple but lacks sufficient strength, easily causing rock cracks in a certain area near the opening, requiring secondary reinforcement later. This method is more suitable for environments with favorable rock conditions. Second, reinforced concrete lining. This method has higher rigidity but lower strength, requires formwork support during concrete pouring, involves greater construction intensity, and has a longer construction period. Furthermore, for tunnels with poor surrounding rock conditions, steel arch frames must still be constructed before reinforced concrete lining to maintain initial stability of the surrounding rock. Therefore, selecting appropriate reinforcement measures for the downstream high-sidewall busbar opening of large, deeply buried underground power generation tunnels with poor surrounding rock conditions is essential. Summary of the Invention

[0004] To address the aforementioned problems, the purpose of this invention is to provide a support structure and construction method for the busbar opening of a large underground power generation cavern sidewall. This structure uses precast reinforced concrete slabs, enabling rapid and convenient construction and achieving prefabricated construction. The use of an H-shaped steel frame combined with anchor bars and prestressed anchor cables provides high rigidity and strength, preventing rock mass cracking and excessive deformation at the opening, resulting in high economic efficiency and safety.

[0005] The technical solution of this invention is as follows: a support structure for the busbar opening of a large underground power generation cavern sidewall, comprising an H-shaped steel bottom beam located at the bottom of the busbar opening and multiple H-shaped steel arches fixedly connected to the H-shaped steel bottom beam. Multiple anchor bars are evenly distributed on the surfaces of the H-shaped steel bottom beam and the H-shaped steel arches, and the anchor bars are fixedly connected to the rock wall of the busbar opening. A reinforced concrete slab is installed between the H-shaped steel arches, and the outer surface of the reinforced concrete slab is provided with wire mesh and sprayed concrete. A baffle is provided between the H-shaped steel arches adjacent to the downstream wall of the power generation cavern and the rock wall of the busbar opening. Foam board is filled in the gap between the baffle and the rock wall. Filling concrete is provided between the baffle and the H-shaped steel arches, the reinforced concrete slab, and the rock wall of the busbar opening.

[0006] The H-shaped steel arch frame is also equipped with several prestressed anchor cables at positions corresponding to the tunnel walls of the sidewall busbar tunnels. The prestressed anchor cables are set within one tunnel span of the tunnel opening. The design tonnage of the prestressed anchor cables is 1000kN to 2000kN, and the pretension load is ≤60% of the design tonnage. The length of the prestressed anchor cables is ≥15m, and the spacing between adjacent prestressed anchor cables is 3.0m to 4.5m. The prestressed anchor cables applied to the rock walls between adjacent sidewall busbar tunnels are through anchor cables or end anchors are applied to the straight walls of the tunnel walls for fixation.

[0007] The distance between the H-shaped steel arch frame and the hole wall of the side wall busbar hole and the top arch rock wall is ≥25cm, and the distance e between adjacent H-shaped steel arch frames is ≤80cm.

[0008] For the top arch, straight wall, and bottom plate of the corresponding side wall busbar opening, the number of anchor bars on the surface of the H-shaped steel bottom beam and H-shaped steel arch frame shall be ≥ 1, the spacing between adjacent anchor bars shall be ≤ 3.0m, the length of the anchor bars shall be 2.5m~3.0m, and the rock penetration depth shall be 2.0m~2.5m.

[0009] The anchor bar consists of two intertwined HRB400 steel bars with a diameter of 25mm. One end extends into the anchor bar hole on the rock wall of the side wall busbar tunnel and is fixed with epoxy mortar. The other end is fixedly connected to the H-shaped steel bottom beam or H-shaped steel arch frame by weld.

[0010] The reinforced concrete slab is a precast component, internally equipped with anchor bars, horizontal bars, and vertical bars. The slab is 5cm thick, 50cm long, and has a width of e-0.75b+0.25t. w Where e is the distance between adjacent H-beam arches, b is the flange width of the H-beam, and t w The web thickness of the H-beam is given. The spacing between the horizontal and vertical reinforcing bars is 15cm. The diameter of the horizontal reinforcing bars is ≥22mm, and the diameter of the vertical reinforcing bars is ≥16mm.

[0011] The anchor bar is located in the middle of the reinforced concrete slab. The number of anchor bars is greater than or equal to the number of anchor bars. The anchor bars are made of HRB400 steel bars with a diameter of 10mm and have a U-shaped structure. The U-shaped open end extends out of the outer surface of the reinforced concrete slab and faces the rock wall of the side wall busbar hole.

[0012] The upper part of the H-shaped steel bottom beam is provided with a layer of steel mesh, and concrete is laid on the steel mesh. The spacing of the steel mesh is 20cm, and the steel bars of the steel mesh are HRB type steel bars with a diameter of ≥22mm. The thickness of the concrete on the steel mesh is ≥5cm.

[0013] Multiple grouting pipes are installed between the H-shaped steel arch frame and the top arch of the side wall busbar opening. The diameter of the grouting pipes is 30mm to 50mm and the material is PVC.

[0014] A construction method for a busbar opening interlocking support structure for the sidewall of a large underground power generation cavern, comprising the following steps:

[0015] S1: Before excavating the busbar opening in the side wall, precast reinforced concrete slabs at the prefabrication yard on the construction site;

[0016] S2: After excavating the busbar opening in the side wall, first complete the initial shotcrete and anchor system support according to the design drawings, and then install the H-shaped steel arch frame and H-shaped steel bottom beam in the busbar opening in the side wall. The two ends of the H-shaped steel bottom beam should be welded to the H-shaped steel arch frame in the straight wall part and fixed with anchor bars. The H-shaped steel bottom beam can be laid against the bottom rock surface of the busbar opening in the side wall. The distance between the outer edge of the H-shaped steel arch frame and the rock wall of the busbar opening in the side wall should be ≥25cm.

[0017] S3: Holes for prestressed anchor cables can be drilled when installing H-shaped steel arch frames and H-shaped steel bottom beams, and the stress anchor cables can be installed and tensioned; the design tonnage of the tensioned stress anchor cables is 1000kN~2000kN, and the pretension load is ≤60% of the design tonnage; the spacing between anchor cables is 3.0m~4.5m;

[0018] S4: Install precast reinforced concrete slabs between H-shaped steel arches, and smooth the gap between the reinforced concrete slabs and H-shaped steel arches with quick-setting resin mortar. At the same time, a baffle should be installed between the H-shaped steel arches adjacent to the downstream wall of the power generation chamber and the rock wall. The baffle is a steel template. The gap between the baffle and the rock wall can be filled with foam board. A layer of steel mesh should be laid on the bottom beam of the H-shaped steel. Multiple grouting pipes are installed between the top arch of the H-shaped steel arches and the busbar hole of the side wall.

[0019] S5: Fill the gaps between the H-shaped steel arch frame and the reinforced concrete slab and the rock wall, and the gaps between the H-shaped steel bottom beams with concrete. The height of each concrete filling for the straight side walls should be ≤2.0m, the height of each concrete filling for the top arch should be ≤1.0m, and the thickness of the concrete filling for the bottom slab should be ≥5cm higher than the top surface of the H-shaped steel bottom beam. The filling concrete should be graded and grade ≥C25. Apply a wire mesh to the outside of the reinforced concrete slab and spray concrete. The thickness of the concrete for the wire mesh sprayed concrete should be 5cm, and the concrete grade should be ≥C25.

[0020] S6: Grouting is performed through the grouting pipe to fill the gaps in the top arch, completing the construction of the interlocking support structure.

[0021] The technical advantages of this invention are as follows: 1. This invention, through H-shaped steel arch frames and H-shaped steel bottom beams, can be quickly installed after the initial shotcrete and anchor system support is completed during the excavation of the main line. Compared with the existing cast-in-place concrete lining structure, it eliminates the need for concrete lining formwork, maximizing rapid construction and reducing construction difficulty; 2. This invention, by configuring prestressed anchor cables within one span of the main line opening, actively applies radial pressure to the rock mass, placing the rock wall within one span of the main line opening under triaxial stress, effectively increasing the rock mass strength. Existing support methods, which involve appropriately lengthening mortar anchors at this location, cannot actively apply pressure and limit the relaxation deformation of the surrounding rock under the vertical pressure from above. Therefore, this arrangement not only more tightly connects the filling concrete with the surrounding rock, but also... Together, they can better improve the structural strength and rigidity, and effectively limit the deformation of the surrounding rock, reduce the damage to the rock mass near the tunnel entrance caused by the excavation and unloading of the lower part of the power generation tunnel, and play a good protective role in the safe operation of the rock anchor beam above the busbar tunnel entrance; 3. This invention makes full use of the characteristics of the H-shaped steel section and the material strength and rigidity. By erecting H-shaped steel arch frames on the side walls and top arch, installing precast reinforced concrete slabs between adjacent H-shaped steel arch frames, filling the gap between the H-shaped steel arch frames and the rock wall with concrete, hanging a layer of steel mesh on the outside of the reinforced concrete slab, and spraying 5cm thick concrete, compared with the existing steel arch frame + sprayed concrete or erecting formwork and pouring reinforced concrete, in addition to increasing the construction speed and reducing the construction difficulty, it can also effectively increase the integrity of the steel arch frame and concrete structure and improve the structural compressive strength.

[0022] The following will provide further explanation in conjunction with the accompanying drawings. Attached Figure Description

[0023] Figure 1 This is a front view of the location of a busbar opening support structure for a side wall of a large underground power generation chamber according to an embodiment of the present invention.

[0024] Figure 2 This is an embodiment of the present invention. Figure 1 BB section view.

[0025] Figure 3 This is an embodiment of the present invention. Figure 2 CC section view.

[0026] Figure 4 This is an embodiment of the present invention. Figure 3 DD section view.

[0027] Figure 5 This is a schematic diagram of the anchor bar structure according to an embodiment of the present invention.

[0028] Figure 6 This is a schematic diagram of the arrangement and structure of the reinforced concrete slab in the straight wall section of the tunnel according to an embodiment of the present invention.

[0029] Figure 7 This is a schematic diagram of the arrangement of reinforced concrete slabs in the tunnel arch section according to an embodiment of the present invention.

[0030] Figure 8 This is an embodiment of the present invention. Figure 7 FF sectional view.

[0031] Figure 9 This is an embodiment of the present invention. Figure 8 EE section view.

[0032] Attached reference numerals: 1-H-shaped steel arch frame, 2-H-shaped steel bottom beam, 3-anchor bar, 4-prestressed anchor cable, 5-reinforced concrete slab, 6-filling concrete, 7-wire mesh sprayed concrete, 8-baffle, 9-grouting pipe, 10-anchor tie bar, 11-horizontal reinforcement bar, 12-vertical reinforcement bar, 13-anchor bar hole, 14-weld. Detailed Implementation

[0033] Example 1

[0034] like Figures 1-9 As shown, Figure 1 In this context, Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ, Ⅵ, Ⅶ, and Ⅷ represent the sequence numbers of the layered excavation of the tunnel; 'a' represents the length of the interlock at the entrance of the busbar tunnel. Figure 2 In this context, 'b' represents the excavation span of the busbar tunnel entrance; Figure 3 In this context, d represents the distance from the outer edge of the steel arch frame to the tunnel wall; Figure 8 f1 = 0.25(bt) w f2 = e - 0.75b + 0.25t w ,e is the distance between H-beam arch frames, b is the flange width of the H-beam, t wThe thickness of the web of the H-beam is given. A support structure for the busbar opening of a large underground power generation cavern sidewall includes an H-beam bottom beam 2 located at the bottom of the busbar opening and multiple H-beam arch frames 1 fixedly connected to the H-beam bottom beam 2. Multiple anchor bars 3 are evenly distributed on the surfaces of the H-beam bottom beam 2 and the H-beam arch frames 1, and the anchor bars 3 are fixedly connected to the rock wall of the busbar opening. A reinforced concrete slab 5 is installed between the H-beam arch frames 1, and the outer surface of the reinforced concrete slab 5 is provided with wire mesh and sprayed concrete 7. A baffle 8 is provided between the H-beam arch frame 1 adjacent to the downstream wall of the power generation cavern and the rock wall of the busbar opening. Foam board is filled in the gap between the baffle 8 and the rock wall. Filling concrete 6 is provided between the baffle 8 and the H-beam arch frame 1, the reinforced concrete slab 5, and the rock wall of the busbar opening.

[0035] In practical use, the present invention can be quickly installed in place after the busbar is excavated and the initial shotcrete system is supported, using H-shaped steel arch frames and H-shaped steel bottom beams. Compared with the existing concrete lining structure for the opening, it does not require concrete lining formwork, thus maximizing the speed of construction and reducing the difficulty of construction.

[0036] Example 2

[0037] Preferably, based on Embodiment 1, in this embodiment, the H-shaped steel arch frame 1 is further provided with several prestressed anchor cables 4 at positions corresponding to the hole walls of the side wall busbar holes. The prestressed anchor cables 4 are set within one span of the hole opening of the side wall busbar holes. The design tonnage of the prestressed anchor cables 4 is 1000kN to 2000kN, and the pretension load is ≤ 60% of the design tonnage. The length of the prestressed anchor cables 4 is ≥ 15m, the spacing between adjacent prestressed anchor cables 4 is 3.0m to 4.5m, and the prestressed anchor cables 4 applied to the rock walls between adjacent side wall busbar holes are through anchor cables or end anchors are applied to the straight wall of the hole.

[0038] In practical use, the H-shaped steel arch frame 1 of this invention is also equipped with several prestressed anchor cables 4 at positions corresponding to the hole wall of the side wall busbar hole. The prestressed anchor cables 4 are set within one span of the hole opening of the side wall busbar hole. The design tonnage of the prestressed anchor cables 4 is 1000kN to 2000kN, and the pretension load is ≤60% of the design tonnage. By configuring prestressed anchor cables within one span of the busbar hole opening, radial pressure is actively applied to the rock mass, so that the rock wall within one span of the busbar hole opening is under triaxial stress. This arrangement effectively increases the strength of the rock mass. However, existing support methods involve appropriately lengthening mortar anchors at this location, which cannot actively apply pressure and limit the relaxation deformation of the surrounding rock under the vertical pressure from above. Therefore, this invention not only connects the filling concrete more tightly with the surrounding rock, thus improving the structural strength and rigidity, but also effectively limits the deformation of the surrounding rock, reduces the damage to the rock mass near the tunnel entrance caused by the excavation and unloading of the lower part of the power generation tunnel, and provides excellent protection for the safe operation of the rock anchor beam above the busbar tunnel entrance.

[0039] Example 3

[0040] Preferably, based on Embodiment 1 or Embodiment 2, in this embodiment, the distance between the H-shaped steel arch frame 1 and the hole wall of the side wall busbar hole and the top arch rock wall is ≥25cm, and the distance e between adjacent H-shaped steel arch frames 1 is ≤80cm.

[0041] In actual use, the distance between the H-shaped steel arch frame 1 and the hole wall of the side wall busbar hole and the top arch rock wall of the present invention is ≥25cm, and a gap is reserved for filling concrete 6. The distance e between adjacent H-shaped steel arch frames 1 is ≤80cm to ensure the structural strength of the reinforced concrete slab 5.

[0042] Example 4

[0043] Preferably, based on Embodiment 1 or Embodiment 3, in this embodiment, for the top arch, straight wall, and bottom plate of the corresponding side wall busbar hole, the number of anchor bars 3 provided on the surface of the H-shaped steel bottom beam 2 and the H-shaped steel arch frame 1 is ≥3, the spacing between adjacent anchor bars 3 is ≤3.0m, the length of the anchor bar 3 is 2.5m~3.0m, and the rock penetration depth is 2.0m~2.5m.

[0044] In actual use, for the top arch, straight wall, and bottom plate of the corresponding side wall busbar opening, the number of anchor bars 3 on the surface of the H-shaped steel bottom beam 2 and H-shaped steel arch frame 1 is ≥3, which ensures that the H-shaped steel bottom beam 2 or H-shaped steel arch frame 1 is firmly connected to the rock wall of the side wall busbar opening.

[0045] Example 5

[0046] Preferably, based on Embodiment 1 or Embodiment 4, in this embodiment, the anchor bar 3 consists of two intertwined HRB400 steel bars with a diameter of 25mm. One end extends into the anchor bar hole 13 on the rock wall of the side wall busbar tunnel and is fixed by epoxy mortar. The other end is fixedly connected to the H-shaped steel bottom beam 2 or H-shaped steel arch 1 by weld 14.

[0047] In actual use, the anchor bar 3 of the present invention consists of two intertwined HRB400 steel bars with a diameter of 25mm. One end extends into the anchor bar hole 13 on the rock wall of the side wall busbar tunnel and is fixed by epoxy mortar. The other end is fixedly connected to the H-shaped steel bottom beam 2 or H-shaped steel arch 1 by weld 14, ensuring that the H-shaped steel bottom beam 2 or H-shaped steel arch 1 is firmly connected to the rock wall of the side wall busbar tunnel.

[0048] Example 6

[0049] Preferably, based on Embodiment 1 or Embodiment 5, in this embodiment, the reinforced concrete slab 5 is a precast component, internally provided with anchor bars 10, horizontal bars 11, and vertical bars 12. The reinforced concrete slab 5 has a thickness of 5cm, a length of 50cm, and a width of e-0.75b+0.25t. w Where e is the distance between adjacent H-beam arch frames 1, b is the flange width of the H-beam, and t w The web thickness of the H-beam is given. The spacing between the horizontal reinforcing bars 11 and the vertical reinforcing bars 12 is 15cm. The diameter of the horizontal reinforcing bars 11 is ≥22mm and the diameter of the vertical reinforcing bars 12 is ≥16mm.

[0050] In actual use, the reinforced concrete slab 5 of the present invention is a precast component, with internal anchor bars 10, horizontal bars 11 and vertical bars 12. The horizontal bars 11 and vertical bars 12 ensure the structural strength of the reinforced concrete slab 5.

[0051] Example 7

[0052] Preferably, based on Embodiment 1 or Embodiment 6, in this embodiment, the anchor bar 10 is located in the middle of the reinforced concrete slab 5, the number of anchor bars 10 is ≥3, the anchor bar 10 is made of HRB400 steel bar with a diameter of 10mm, and has a U-shaped structure, with the U-shaped open end extending out of the outer surface of the reinforced concrete slab 5 and facing the rock wall of the side wall busbar hole.

[0053] In actual use, the anchor bar 10 of the present invention is located in the middle of the reinforced concrete slab 5. The number of anchor bars 10 is ≥3. It is a U-shaped structure. The U-shaped open end extends out of the outer surface of the reinforced concrete slab 5 and faces the rock wall of the side wall busbar hole. After the gap between the H-shaped steel arch frame 1 and the reinforced concrete slab 5 and the rock wall is filled with filling concrete 6, the U-shaped open end of the anchor bar 10 is fixedly connected to the filling concrete 6, ensuring the connection strength of the reinforced concrete slab 5.

[0054] Example 8

[0055] Preferably, based on Embodiment 1 or Embodiment 7, in this embodiment, a layer of steel mesh is provided on the upper part of the H-shaped steel bottom beam 2, and concrete is provided on the steel mesh. The spacing of the steel mesh is 20cm, the steel bars of the steel mesh are HRB400 type steel bars with a diameter ≥22mm, and the thickness of the concrete on the steel mesh is ≥5cm.

[0056] In actual use, the H-shaped steel bottom beam 2 of the present invention is provided with a layer of steel mesh on the upper part, and concrete is provided on the steel mesh to ensure the structural strength of the H-shaped steel bottom beam 2.

[0057] Example 9

[0058] Preferably, based on Embodiment 1 or Embodiment 8, in this embodiment, a plurality of grouting pipes 9 are provided between the H-shaped steel arch frame 1 and the top arch of the side wall busbar hole. The diameter of the grouting pipes 9 is 30mm to 50mm and the material is PVC.

[0059] In actual use, the present invention uses the grouting pipe 9 to backfill the gaps in the top arch with grout.

[0060] Example 10

[0061] A construction method for a busbar opening interlocking support structure for the sidewall of a large underground power generation cavern, comprising the following steps:

[0062] S1: Before excavating the busbar opening in the side wall, precast reinforced concrete slab 5 in the prefabrication yard at the construction site;

[0063] S2: After excavating the busbar opening in the side wall, first complete the initial shotcrete and anchor system support according to the design drawings, and then install the H-shaped steel arch frame 1 and H-shaped steel bottom beam 2 in the busbar opening in the side wall. The two ends of the H-shaped steel bottom beam 2 should be welded to the H-shaped steel arch frame 1 in the straight wall part, and at the same time, they should be fixed with anchor bars 3. The H-shaped steel bottom beam 2 can be laid against the bottom rock surface of the busbar opening in the side wall. The distance between the outer edge of the H-shaped steel arch frame 1 and the rock wall of the busbar opening in the side wall should be ≥25cm.

[0064] S3: When installing the H-shaped steel arch frame 1 and the H-shaped steel bottom beam 2, holes for prestressed anchor cables 4 can be drilled to install and tension the stress anchor cables 4; the design tonnage of the tensioning stress anchor cables 4 is 1000kN~2000kN, and the pretension load is ≤60% of the design tonnage; the spacing between anchor cables is 3.0m~4.5m;

[0065] S4: Install precast reinforced concrete slabs 5 between H-shaped steel arch frames 1, and smooth the gap between the reinforced concrete slabs 5 and H-shaped steel arch frames 1 with quick resin mortar. At the same time, a baffle 8 should be set between the H-shaped steel arch frame 1 and the rock wall adjacent to the downstream wall of the power generation chamber. The baffle 8 is a steel template. The gap between the baffle 8 and the rock wall can be filled with foam board. A layer of steel mesh should be laid on the H-shaped steel bottom beam 2. Multiple grouting pipes 9 are set between the top arch of the H-shaped steel arch frame 1 and the side wall busbar hole.

[0066] S5: Fill the gaps between the H-shaped steel arch frame 1 and the reinforced concrete slab 5 and the rock wall, and the gaps between the H-shaped steel bottom beams 2 with concrete 6. The height of each filling of concrete 6 for the straight side wall shall be ≤2.0m, the height of each filling of concrete 6 for the top arch shall be ≤1.0m, and the thickness of the filling of concrete 6 for the bottom slab shall be ≥5cm higher than the top surface of the H-shaped steel bottom beam. The filling concrete shall be graded 2 and grade ≥C25. Attach wire mesh to the outside of the reinforced concrete slab 5 and spray concrete 7. The thickness of the sprayed concrete 7 shall be 5cm and the concrete grade shall not be lower than C25.

[0067] S6: Grouting is performed through grouting pipe 9 to backfill the gaps in the top arch, completing the construction of the interlocking support structure.

[0068] This invention fully utilizes the characteristics of H-shaped steel cross-sections and the material strength and rigidity. By erecting H-shaped steel arch frames on the side walls and top arch, installing precast reinforced concrete slabs between adjacent H-shaped steel arch frames, filling the gaps between the H-shaped steel arch frames and the rock wall with concrete, and hanging a layer of steel mesh on the outside of the reinforced concrete slabs, and then spraying 5cm thick concrete, compared with existing steel arch frames + sprayed concrete or erecting formwork and pouring reinforced concrete, this invention not only increases the construction speed and reduces the construction difficulty, but also effectively increases the integrity of the steel arch frames and concrete structure, and improves the compressive strength of the structure.

[0069] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A support structure for the busbar opening of the sidewall of a large underground power generation chamber, characterized in that: Includes an H-shaped steel bottom beam (2) located at the bottom of the side wall busbar tunnel and multiple H-shaped steel arch frames (1) fixedly connected to the H-shaped steel bottom beam (2). Multiple anchor bars (3) are evenly distributed on the surfaces of the H-shaped steel bottom beam (2) and the H-shaped steel arch frames (1). The anchor bars (3) are fixedly connected to the rock wall of the side wall busbar tunnel. A reinforced concrete slab (5) is installed between the H-shaped steel arch frames (1). The outer surface of the reinforced concrete slab (5) is provided with wire mesh sprayed concrete (7). A baffle (8) is provided between the H-shaped steel arch frame (1) adjacent to the downstream wall of the power generation tunnel and the rock wall of the side wall busbar tunnel. The gap between the baffle (8) and the rock wall is filled with foam board. A filling concrete (6) is provided between the baffle (8) and the H-shaped steel arch frame (1), the reinforced concrete slab (5), and the rock wall of the side wall busbar tunnel. 1) Several prestressed anchor cables (4) are also provided at positions corresponding to the hole walls of the side wall busbar holes. The prestressed anchor cables (4) are set within one span of the hole opening of the side wall busbar holes. The design tonnage of the prestressed anchor cables (4) is 1000kN to 2000kN, and the pretension load is ≤ 60% of the design tonnage. The length of the prestressed anchor cables (4) is ≥ 15m, and the row spacing of adjacent prestressed anchor cables (4) is 3.0m to 4.5m. The prestressed anchor cables (4) applied to the rock walls between adjacent side wall busbar holes are through anchor cables or end anchors are applied to the straight wall of the hole. The reinforced concrete slab (5) is a precast component with internal anchor bars (10), horizontal bars (11) and vertical bars (12). The thickness of the reinforced concrete slab (5) is 5cm, the length is 50cm, and the width is Where e is the distance between adjacent H-beam arch frames (1), and b is the flange width of the H-beam. The web thickness of the H-beam is given. The spacing between the horizontal reinforcing bars (11) and the vertical reinforcing bars (12) is 15cm. The diameter of the horizontal reinforcing bars (11) is ≥22mm and the diameter of the vertical reinforcing bars (12) is ≥16mm.

2. The support structure for the busbar opening of the side wall of a large underground power generation chamber according to claim 1, characterized in that: The distance between the H-shaped steel arch frame (1) and the hole wall of the side wall busbar hole and the top arch rock wall is ≥25cm, and the distance e between adjacent H-shaped steel arch frames (1) is ≤80cm.

3. The support structure for the busbar opening of the side wall of a large underground power generation chamber according to claim 1, characterized in that: For the top arch, straight wall, and bottom plate of the corresponding side wall busbar hole, the number of anchor bars (3) on the surface of the H-shaped steel bottom beam (2) and the H-shaped steel arch frame (1) is ≥3, the spacing between adjacent anchor bars (3) is ≤3.0m, the length of the anchor bar (3) is 2.5m~3.0m, and the rock penetration depth is 2.0m~2.5m.

4. The support structure for the busbar opening of the side wall of a large underground power generation chamber according to claim 1, characterized in that: The anchor bar (3) consists of two intertwined HRB400 steel bars with a diameter of 25mm. One end extends into the anchor bar hole (13) on the rock wall of the side wall busbar tunnel and is fixed by epoxy mortar. The other end is fixedly connected to the H-shaped steel bottom beam (2) or H-shaped steel arch frame (1) by weld (14).

5. The support structure for the busbar opening of the side wall of a large underground power generation chamber according to claim 1, characterized in that: The anchor bar (10) is located in the middle of the reinforced concrete slab (5). The number of anchor bars (10) is ≥3. The anchor bar (10) is made of HRB400 steel bar with a diameter of 10mm. It is a U-shaped structure with the U-shaped opening end extending out of the outer surface of the reinforced concrete slab (5) and facing the rock wall of the side wall busbar hole.

6. The support structure for the busbar opening of the side wall of a large underground power generation chamber according to claim 1, characterized in that: The H-shaped steel bottom beam (2) is provided with a layer of steel mesh on the upper part, and concrete is provided on the steel mesh. The spacing of the steel mesh is 20cm, and the steel bars of the steel mesh are HRB400 type steel bars with a diameter ≥22mm. The thickness of the concrete on the steel mesh is ≥5cm.

7. The support structure for the busbar opening of the side wall of a large underground power generation chamber according to claim 1, characterized in that: Multiple grouting pipes (9) are provided between the H-shaped steel arch frame (1) and the top arch of the side wall busbar hole. The diameter of the grouting pipes (9) is 30mm to 50mm and the material is PVC.

8. A construction method for a busbar opening interlocking support structure for the sidewall of a large underground power generation cavern, wherein the construction method is described in any one of claims 1 to 7, characterized in that: Includes the following steps: S1: Before excavating the busbar opening in the side wall, precast reinforced concrete slabs (5) at the prefabrication yard on the construction site. S2: After the excavation of the busbar opening in the side wall, the initial spraying and anchoring system support is completed according to the design drawings. Then, H-shaped steel arch frame (1) and H-shaped steel bottom beam (2) are installed in the busbar opening in the side wall. The two ends of the H-shaped steel bottom beam (2) are welded to the H-shaped steel arch frame (1) in the straight wall part and fixed with anchor bars (3). The H-shaped steel bottom beam (2) is laid against the bottom rock surface of the busbar opening in the side wall. The distance between the outer edge of the H-shaped steel arch frame (1) and the rock wall of the busbar opening in the side wall is ≥25cm. S3: Drill holes for prestressed anchor cables (4) when installing H-shaped steel arch frame (1) and H-shaped steel bottom beam (2), and install and tension the prestressed anchor cables (4); the design tonnage of the tensioned prestressed anchor cables (4) is 1000kN~2000kN, and the pretension load is ≤60% of the design tonnage; the spacing between anchor cables is 3.0m~4.5m; S4: Install precast reinforced concrete slabs (5) between H-shaped steel arch frames (1), and smooth the gap between the reinforced concrete slabs (5) and H-shaped steel arch frames (1) with quick resin mortar. At the same time, a baffle (8) should be set between the H-shaped steel arch frame (1) and the rock wall adjacent to the downstream wall of the power generation chamber. The baffle (8) is a steel template. The gap between the baffle (8) and the rock wall is filled with foam board. A layer of steel mesh should be laid on the bottom beam (2) of the H-shaped steel. Multiple grouting pipes (9) are set between the top arch of the H-shaped steel arch frame (1) and the side wall busbar hole. S5: Fill the gaps between the H-shaped steel arch frame (1) and the reinforced concrete slab (5) and the rock wall, and the gaps between the H-shaped steel bottom beam (2) with concrete (6). The height of each filling of the straight side wall with concrete (6) is ≤2.0m, the height of each filling of the top arch with concrete (6) is ≤1.0m, and the thickness of the filling of the bottom slab with concrete (6) is ≥5cm higher than the top surface of the H-shaped steel bottom beam. The filling concrete is grade 2 and grade ≥C25. Spray concrete (7) is applied to the outside of the reinforced concrete slab (5) with wire mesh. The thickness of the sprayed concrete (7) is 5cm and the concrete grade is not lower than C25. S6: The gaps in the top arch are backfilled and grouted through the grouting pipe (9) to complete the construction of the lock support structure.

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