City gate opening type tunnel supporting structure

Abstract

The utility model provides a city gate opening type tunnel supporting structure, which belongs to the technical field of pavement construction and comprises a primary sprayed concrete layer, a secondary sprayed concrete layer and a supporting layer, the anchor rods are mounted around the excavated structural surface at certain intervals; the steel arch is located on the surface of the primarily-sprayed concrete layer and is formed by vertically fixing profile steel along the surface of the primarily-sprayed concrete layer; the two layers of reinforcing meshes are arranged on the two faces of the steel arch respectively; the re-spraying concrete layer is formed by spraying early-strength and high-strength steel fiber concrete covering the outer reinforcing mesh; and the cross-brace profile steel and the bottom of the steel arch form a horizontal symmetrical support. The transverse supporting structure is additionally arranged at the bottom of the steel arch frame, the inverted arch effect can be achieved, it is guaranteed that the lower portion of a city door opening type section is stable, and the defect that compared with a horseshoe-shaped section, an inverted arch can be arranged is overcome.

Description

Technical Field

[0001] This utility model relates to the field of tunnel construction technology, and in particular to a support structure for a city gate tunnel. Background Technology

[0002] Underground cavern excavation and support is a common construction project in the field of construction engineering. Conventional cavern structures generally have two structural types: horseshoe-shaped and portal-shaped. Among them, the portal-shaped cross-section is widely used in tunnel design due to its beautiful structure and open space advantages.

[0003] In most tunnel projects, the surrounding rock geological conditions are poor in the entrance section or fault zone, making natural tunnel formation difficult and requiring the use of steel arch frames for initial support. When the selected entrance is located on one side of the mountain or the rock lithology, groundwater level, and other conditions on both sides of the tunnel axis are inconsistent, the steel arch frame will always bear uneven lateral pressure from the rock (soil) on both sides before the secondary concrete lining, which can easily cause the arch frame to deform or even overturn, affecting the safety of the tunnel. Utility Model Content

[0004] This utility model provides a tunnel support structure for a city gate type, which solves the defects of underground cavern excavation support in the prior art.

[0005] This utility model provides a tunnel support structure for a city gate-type tunnel, which supports the excavated structural surface formed after tunnel excavation. It includes: an initial shotcrete layer, anchor bolts, steel mesh, a steel arch frame, a secondary shotcrete layer, and cross bracing steel. The initial shotcrete layer is located on the surface of the excavated structural surface and is formed by spraying 3-5 cm thick high-strength steel fiber reinforced concrete onto the excavated contour surface. Anchor bolts are installed at certain intervals around the excavated structural surface to ensure overall stability of the excavated structural surface. The steel arch frame is located on the surface of the initial shotcrete layer and is formed by vertically fixing steel along the surface of the initial shotcrete layer. The steel mesh includes two layers, respectively set on both sides of the steel arch frame; one layer covers the surface of the initial shotcrete layer, and the other layer is located on the bottom surface of the secondary shotcrete layer. The secondary shotcrete layer is formed by spraying high-strength steel fiber reinforced concrete covering the outer layer of steel mesh. The cross bracing steel forms a horizontally symmetrical support with the bottom of the steel arch frame.

[0006] According to the present invention, the support structure for a tunnel with a gate-like opening is provided, wherein the type of the cross bracing steel includes I-beams, H-beams, or channel steel, and its length is adjusted according to the width of the tunnel excavation section.

[0007] According to the present invention, in a tunnel support structure of the city gate type, the connection point between the cross brace steel and the steel arch frame is 5cm away from the bottom support point of the steel arch frame, but does not exceed the tunnel pavement structure limit.

[0008] According to the present invention, in a tunnel support structure of the city gate type, the two ends of the cross bracing steel are connected to the bottom of the steel arch frame by double-sided welding.

[0009] According to the present invention, a tunnel support structure for a city gate type is provided, wherein the initial shotcrete layer, the anchor bolts, the steel mesh, the steel arch frame, and the secondary shotcrete layer constitute the initial support structure.

[0010] According to the present invention, in a tunnel support structure of the city gate type, the horizontal bracing steel is installed before the final setting of the sprayed concrete layer, and the horizontal bracing steel is subjected to force synchronously with the initial support structure.

[0011] According to the present invention, a tunnel support structure of the city gate type is provided, wherein the bottom support point of the city gate type steel arch frame is pre-set with a welding positioning mark, and the end of the cross brace steel is welded after being positioned by the positioning mark.

[0012] According to the present invention, a tunnel support structure of the city gate type is provided, wherein a reinforcing steel plate is provided at the connection point between the cross brace steel and the steel arch frame to improve the shear strength of the connection point.

[0013] According to the present invention, a tunnel support structure of the city gate type is provided, wherein the cross bracing steel is arranged at intervals along the longitudinal direction of the tunnel, with a spacing of 50~80cm.

[0014] According to the present invention, in a tunnel support structure for a city gate-shaped tunnel, the cross-sectional width of the cross bracing steel is not less than 1 / 2 of the cross-sectional width of the steel arch frame for the city gate-shaped tunnel.

[0015] The tunnel support structure for the city gate type provided by this utility model can achieve the effect of an inverted arch by adding a horizontal bracing structure at the bottom of the steel arch frame, ensuring the stability of the lower part of the city gate type cross section and making up for its deficiency compared with the horseshoe type cross section in that it can be equipped with an inverted arch. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the support structure for the city gate tunnel type provided by this utility model.

[0018] Figure label:

[0019] 100. Initial shotcrete layer;

[0020] 200. Anchor bolt;

[0021] 300. Steel mesh;

[0022] 400. Steel arch frame;

[0023] 500. Re-sprayed concrete layer;

[0024] 600, cross bracing steel. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0026] In the description of this utility model, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0027] In the description of this utility model, it should be understood that the directional terms such as "front, back, up, down, left, right", "horizontal, vertical, perpendicular, horizontal" and "top, bottom" indicate the direction or positional relationship, which is usually based on Figure 1 The orientation and position of the tunnel support structure shown in the diagram when it is normally placed are only for the convenience of describing this utility model and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or component referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this utility model. The directional terms "inner" and "outer" refer to the inner and outer contours of each component itself.

[0028] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0029] This utility model provides a support structure for a city gate-type tunnel. See also: Figure 1The support structure is constructed on the excavated structural face after tunnel excavation, and includes: a 100mm initial shotcrete layer, 200mm anchor bolts, 300mm steel mesh, 400mm steel arch frame, a 500mm secondary shotcrete layer, and 600mm cross bracing steel. The 100mm initial shotcrete layer is located on the surface of the excavated structural face; it is formed by spraying 3-5cm thick high-strength steel fiber reinforced concrete onto the excavated contour surface. The 200mm anchor bolts are installed at certain intervals around the excavated structural face to ensure overall structural stability. The 400mm steel arch frame... 0, located on the surface of the initial shotcrete layer 100, is formed by vertically fixing steel sections along the surface of the initial shotcrete layer 100; the steel mesh 300 includes two layers, respectively set on both sides of the steel arch frame 400, one layer covering the surface of the initial shotcrete layer 100 and the other layer located on the bottom surface of the secondary shotcrete layer 500; the secondary shotcrete layer 500 is formed by spraying high-strength steel fiber concrete covering the outer steel mesh 300; the horizontal bracing steel 600 forms a horizontal symmetrical support with the bottom of the steel arch frame 400.

[0030] After each tunnel excavation cycle is completed, initial support measures are implemented sequentially as shown in the diagram, including: a 5cm initial shotcrete layer (100mm), a 4.5m long system anchor bolt (200mm), a Ф8@150*150mm steel mesh (300mm), a 20b archway-shaped steel arch frame (400mm), and a 25cm thick C25 secondary shotcrete layer (500mm). The main support structure is the archway-shaped steel arch frame (400mm). The pre-prepared cross bracing steel (600mm) is transported to the tunnel construction face, aligning its two ends with the bottom support points of the archway-shaped steel arch frame (400mm).

[0031] For example, the cross bracing steel 600 can be of the form of I-beam, H-beam or channel steel, and its length can be adjusted according to the width of the tunnel excavation section.

[0032] For example, the cross bracing steel 600 is arranged at intervals along the longitudinal direction of the tunnel, with a spacing of 1 to 2 times the tunnel excavation span.

[0033] For example, the cross-sectional width of the 600 cross bracing steel is not less than 1 / 2 of the cross-sectional width of the 400 arch steel frame for city gate openings.

[0034] In one embodiment, the connection point between the cross brace 600 and the steel arch frame 400 is 5cm away from the bottom support point of the steel arch frame 400, but does not exceed the tunnel pavement structure limit.

[0035] Use stones or other tools to raise one end of the cross brace steel 600 by about 5cm. After adjusting the other end of the cross brace steel 600 to a horizontal position, weld it to the bottom support point of the city gate arch steel frame 400.

[0036] For example, the two ends of the cross bracing steel 600 are connected to the bottom of the steel arch frame 400 by double-sided welding.

[0037] For example, the bottom support point of the steel arch frame 400 is pre-marked with a welding positioning mark, and the end of the cross brace steel 600 is positioned by the positioning mark and then welded.

[0038] For example, a reinforcing steel plate is provided at the connection point between the cross bracing steel 600 and the steel arch frame 400 to improve the shear strength of the connection point.

[0039] In one embodiment, the initial shotcrete layer 100, anchor bolts 200, steel mesh 300, steel arch frame 400, and secondary shotcrete layer 500 constitute the initial support structure. The cross bracing steel 600 is installed before the secondary shotcrete layer 500 has fully set, and the cross bracing steel 600 is stressed synchronously with the initial support structure.

[0040] In one embodiment, after the cross bracing steel 600 is connected, the excavation process can continue, and the excavated tunnel can remain relatively stable and safe for a certain period of time. After excavating a certain distance, the road surface structure concrete can be poured or gravel can be laid to meet the conditions for vehicle transportation.

[0041] This invention achieves the effect of an inverted arch by adding a horizontal bracing structure to the bottom of the steel arch frame 400, ensuring the stability of the lower part of the portal-shaped cross-section and compensating for its inability to install an inverted arch compared to a horseshoe-shaped cross-section. By adding the horizontal bracing structure to the bottom of the steel arch frame 400, lateral pressure can be transferred to the other side, effectively ensuring the overall stress balance of the portal-shaped steel arch frame 400 in asymmetrical tunnel sections with thin overburden, preventing deformation and instability. In tunnel sections with poor geological conditions and insufficient tunnel foundation bearing capacity, adding the bottom horizontal bracing structure allows the portal-shaped steel arch frame 400 to form a closed whole. After pouring the lining concrete, it forms an integral structure in both directions parallel and perpendicular to the tunnel axis, effectively avoiding quality problems such as cracking of the lining concrete caused by uneven foundation settlement. By adding a horizontal bracing structure at the bottom of the 400mm steel arch frame to effectively constrain the sidewalls of the tunnel's arch-shaped cross-section, deformation that could encroach on the tunnel's construction limits after the initial support is completed and before permanent lining construction begins can be prevented, ensuring the tunnel fulfills its designed functions for transportation and facility layout. Adding a horizontal bracing structure at the bottom of the 400mm steel arch frame effectively ensures the tunnel's safety and stability before permanent lining, allowing permanent lining construction to proceed only after all excavation procedures are completed, thus saving time and construction costs. Furthermore, replacing concrete backfill with a horizontal bracing structure at the bottom of the 400mm steel arch frame effectively overcomes uneven foundation settlement, further reducing construction costs.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.

Claims

1. A tunnel support structure for a city gate type, characterized in that, The support structure is constructed on the excavated structural face formed after the tunnel excavation is completed, including: initial shotcrete layer, anchor bolts, steel mesh, steel arch frame, secondary shotcrete layer and cross bracing steel; The initial shotcrete layer is located on the surface of the excavated structure; it is formed by spraying 3-5cm thick early high-strength steel fiber concrete onto the surface of the excavation outline. Anchor bolts are installed around the excavated structure at certain intervals to ensure the overall stability of the excavated structure under stress. The steel arch frame is located on the surface of the initial shotcrete layer and is constructed by vertically fixing steel sections along the surface of the initial shotcrete layer. The steel mesh consists of two layers, which are respectively set on both sides of the steel arch frame. One layer covers the surface of the initial shotcrete layer, and the other layer is located on the bottom surface of the secondary shotcrete layer. The sprayed concrete layer is formed by spraying high-strength steel fiber concrete that covers the outer steel mesh. The horizontal bracing steel forms a horizontally symmetrical support with the bottom of the steel arch frame.

2. The tunnel support structure of the city gate type according to claim 1, characterized in that, The type of cross bracing steel includes I-beams, H-beams, or channel steel, and its length is adjusted according to the width of the tunnel excavation section.

3. The tunnel support structure of the city gate type according to claim 1, characterized in that, The connection point between the cross brace steel and the steel arch frame is 5cm away from the bottom support point of the steel arch frame, but does not exceed the tunnel pavement structure limit.

4. The tunnel support structure of the city gate type according to claim 3, characterized in that, The two ends of the cross bracing steel are connected to the bottom of the steel arch frame by double-sided welding.

5. The tunnel support structure of the city gate type according to claim 1, characterized in that, The initial shotcrete layer, the anchor bolts, the steel mesh, the steel arch frame, and the subsequent shotcrete layer constitute the initial support structure.

6. The tunnel support structure of the city gate type according to claim 5, characterized in that, The horizontal bracing steel is installed before the final setting of the sprayed concrete layer, and the horizontal bracing steel is subjected to stress synchronously with the initial support structure.

7. The tunnel support structure of the city gate type according to claim 1, characterized in that, The bottom support points of the steel arch frame of the city gate are pre-marked with welding positioning marks, and the ends of the cross bracing steel are welded after being positioned by these positioning marks.

8. The tunnel support structure of the city gate type according to claim 1, characterized in that, The connection point between the cross brace and the steel arch frame is provided with a reinforcing steel plate to improve the shear strength of the connection point.

9. The tunnel support structure of the city gate type according to claim 5, characterized in that, The cross bracing steel sections are arranged at intervals along the longitudinal direction of the tunnel, with a spacing of 50-80cm.

10. The tunnel support structure of the city gate type according to claim 1, characterized in that, The cross-sectional width of the cross bracing steel is not less than 1 / 2 of the cross-sectional width of the arch steel frame for the city gate.

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