A cantilever passive protection net system suitable for tunnel portal

Abstract

The utility model discloses a kind of tunnel portal cantilever passive protection net systems suitable for precipitous terrain, the system innovatively uses the inclined bracing steel column of setting as main bearing component, its lower end is connected with a pressure type shallow buried foundation through hinged base, and upper end is anchored in mountain body through prestressed cable-stayed anchor rod, and it is jointly constituted stable triangle stress system.The structure converts the huge bending moment and pulling force that steel column root bears in traditional system into pressure to shallow buried foundation and the tension of cable-stayed anchor rod, greatly reduces the dependence on long anchor rod on precipitous cliff.The utility model further includes support rope, steel rope net and grating net adapted to the support structure.The structure is clear in stress, and construction is safe and convenient, with high stability, can effectively guarantee the operation safety of precipitous tunnel portal.

Description

Technical Field

[0001] This utility model relates to the field of geotechnical engineering protection technology, specifically to a rockfall cantilever passive protection system suitable for the slope above the tunnel entrance, and is particularly suitable for passive protection nets installed on steep sections of mountain slopes with large slopes (usually greater than 60°). Background Technology

[0002] In the construction of transportation infrastructure in mountainous areas, tunnels are a crucial means of traversing mountain ranges. Tunnel entrances are often located at the lower part of steep slopes with complex geological conditions. To prevent falling rocks from the slope from threatening the tunnel structure and operational safety, passive protective netting is often installed above the entrance. Traditional passive protective netting systems typically use vertically installed steel columns, secured by top and side anchors installed on the top and sides of the columns. This structure works well in gentle slope sections.

[0003] However, in extremely steep sections, this traditional structure reveals the following problems: First, the top and side anchors used to fix the steel columns require high-altitude drilling on near-vertical steep walls, making it difficult to build construction platforms, inconvenient to position machinery, posing a significant safety threat to construction workers, and making it difficult to guarantee drilling accuracy. Second, the surface rock mass of steep slopes is often quite fractured. Under such geological conditions, the anchoring section of the anchors may be located in unstable rock strata, making it difficult to achieve the design anchoring force and posing a risk of long-term failure. Third, traditional vertical steel columns mainly rely on the pull-out force of the anchors to maintain stability. On steep slopes, the stress state of the anchors is complex. Once a critical anchor fails, it can easily cause the steel column to overturn, leading to the failure of the entire protection system and even posing a secondary disaster to the safety of vehicles below.

[0004] Therefore, there is an urgent need for a new type of passive protective net structure that can adapt to steep terrain, avoid the aforementioned construction and safety risks, and ensure the effectiveness and reliability of the protective system. Utility Model Content

[0005] In view of the problems of difficult anchor installation, unstable fixing, and poor safety when installing passive protection nets in steep sections in the existing technology, this utility model aims to provide a tunnel entrance cantilever passive protection net system that is structurally stable, easy to construct, and highly safe.

[0006] To achieve the above technical objectives, the following technical solution is adopted: A cantilevered passive protection net system suitable for tunnel entrances includes a support structure, an anchoring structure, and a protection net assembly. The support structure includes multiple inclined steel columns spaced apart above the tunnel entrance, the inclined steel columns being inclined relative to the slope. The anchoring structure includes a pressure-bearing shallow foundation and prestressed inclined anchor rods. The pressure-bearing shallow foundation is embedded in a stable part of the slope at the lower end of the inclined steel columns, and the lower end of the inclined steel columns is hinged to the pressure-bearing shallow foundation via a hinged base. One end of the prestressed inclined anchor rod is anchored in a stable soil layer behind the upper end of the inclined steel column, and the other end is tensioned and connected to the upper end of the inclined steel column. The protection net assembly is hung on a support frame composed of multiple inclined steel columns and upper and lower support ropes connecting them.

[0007] Furthermore, the angle α between the axis of the diagonal bracing steel column and the horizontal plane is 10° to 30°.

[0008] Furthermore, the hinged base includes a lower hinge plate fixed to the bearing shallow buried foundation and an upper hinge plate fixed to the lower end of the diagonal bracing steel column. The lower hinge plate and the upper hinge plate are connected by a horizontally arranged pin, so that the diagonal bracing steel column can rotate slightly around the pin in a plane perpendicular to the slope.

[0009] Furthermore, the pressure-bearing shallow foundation is a cast-in-place reinforced concrete structure with a base depth of not less than 1.5 meters and a concrete pad layer laid at the bottom; anchor bolts for connecting the hinged base are pre-embedded in the foundation.

[0010] Furthermore, the angle β between the axis of the prestressed inclined anchor rod and the axis of the inclined steel column is 30° to 60°.

[0011] Furthermore, the upper support rope is connected to the top of all the diagonal bracing steel columns to form the main load-bearing longitudinal beam; the lower support rope is connected to the middle and lower part of all the diagonal bracing steel columns to form an auxiliary stabilizing longitudinal beam.

[0012] Furthermore, several adjusting rods are vertically installed between the upper and lower support ropes. The upper end of each adjusting rod is connected to the top of the upper support rope or the diagonal steel column via turnbuckles, and the lower end is connected to the lower support rope. These rods are used to tension and adjust the verticality and flatness of the protective netting.

[0013] Furthermore, the protective net assembly includes a main protective steel rope net on the outer side and a secondary grid net on the inner side; the main protective steel rope net is woven from high-strength steel wire rope into a diamond-shaped mesh and is fixed to the upper and lower support ropes by stitching ropes; the secondary grid net is woven from steel wire into a small mesh structure, and its edges are pressed against the inner side of the main protective steel rope net and fixed by tie wires.

[0014] The working principle of this invention is as follows: When falling rocks impact the protective netting, the load is transferred to the inclined steel columns through the netting and ropes, attempting to cause the steel columns to rotate outwards around their lower hinge points. This rotational tendency is resisted on the one hand by the tensile force of the prestressed inclined anchor rods, and on the other hand, it is transformed into pressure on the bearing-type shallow buried foundation. The hinged base design releases the bending moment at the base of the steel column, allowing the steel column to mainly bear the axial pressure, thus fully utilizing its material strength. Through this mechanism, the enormous impact energy is effectively absorbed and dispersed through structural deformation and the force transmission path.

[0015] The beneficial effects achieved by this utility model are: This utility model provides a cantilevered passive protection net system suitable for tunnel entrances. Compared with the prior art, the core concept lies in changing the stress mode of the supporting structure, transforming it from the traditional "cantilever beam" mode to a "cantilevered inclined truss" mode, which has the following significant advantages: Construction safety and convenience are greatly improved: drilling operations on dangerous steep walls, which are carried out vertically or inclined upwards, are transformed into foundation excavation in relatively gentle areas and drilling of inclined anchor bolts at relatively safe angles, significantly reducing construction difficulty and risk; Enhanced structural stability and reliability: The triangular structure is a geometrically stable form. The diagonal bracing steel columns mainly bear compressive forces, the shallow foundation mainly bears compressive forces, and the diagonal anchor rods mainly bear tensile forces. This fully utilizes the performance advantages of each material, resulting in overall stability superior to traditional structures that rely on anchor rods for pull-out resistance.

[0016] Better adaptability to geological conditions: The requirements for the foundation soil of bearing foundations are generally lower than the requirements for the integrity of the surrounding rock mass of pull-out anchors. As long as the foundation is situated on a stable layer, it can provide reliable support.

[0017] High safety redundancy: Even if a single inclined anchor rod experiences stress loss or partial damage, the entire structural system can still maintain a certain degree of stability and will not collapse instantly, thus ensuring higher safety. Attached Figure Description

[0018] The present invention will now be described in conjunction with the accompanying drawings.

[0019] Figure 1 This is a side view of the present invention.

[0020] Figure 2 This is a schematic elevation view of the overall layout of this utility model.

[0021] Figure 3 This is a schematic diagram of the connection structure of the inclined steel column, hinged base and shallow buried foundation in this utility model.

[0022] In the diagram: 1-Diagonal bracing steel column; 2-Hinged base; 21-Lower hinge plate; 22-Upper hinge plate; 23-Pin shaft; 3-Bearing shallow buried foundation; 31-Concrete pad; 32-Anchor bolt; 4-Prestressed inclined anchor rod; 51-Upper support rope; 52-Lower support rope; 6-Adjusting rod; 7-Main protective steel rope net; 8-Secondary grid net. Detailed Implementation

[0023] The following specific embodiments illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. The described embodiments are merely 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.

[0024] like Figures 1 to 3 As shown, this utility model provides a cantilevered passive protection net system suitable for tunnel entrances, which mainly includes a diagonal steel column 1, a hinged base 2, a pressure-bearing shallow buried foundation 3, a prestressed inclined anchor rod 4, a support rope system, and a protection net assembly. The inclined steel column 1 is the core load-bearing component of the system. It is installed at an angle, and the angle α between its axis and the horizontal plane is preferably 10° to 30°. Its lower end is connected to the bearing shallow foundation 3 through a hinged base 2, and its upper end is pulled backward and upward through a prestressed inclined anchor rod 4. The angle β between the inclined anchor rod 4 and the axis of the steel column is preferably 30° to 60°, thus forming a stable triangular force unit together with the steel column and the foundation.

[0025] The hinged base 2 includes a lower hinge plate 21 fixed on the pressure-bearing shallow buried foundation 3 and an upper hinge plate 22 fixed on the lower end of the inclined steel column 1. The lower hinge plate 21 and the upper hinge plate 22 are connected by a horizontally arranged pin 23, so that the inclined steel column 1 can rotate slightly around the pin 23 in a plane perpendicular to the slope.

[0026] The pressure-bearing shallow foundation 3 is set at the toe of a slope, terrace, or small platform that is easy to excavate or treat. It is a cast-in-place reinforced concrete structure with a foundation depth of not less than 1.5 meters and a concrete pad 31 at the bottom. Anchor bolts 32 for connecting the hinged base 2 are pre-embedded in the foundation.

[0027] The support rope system includes an upper support rope 51 and a lower support rope 52. The upper support rope 51 is connected to the top of all the diagonal steel columns 1 to form the main load-bearing longitudinal beam. The lower support rope 52 is connected to the middle and lower part of all the diagonal steel columns 1 to form an auxiliary stabilizing longitudinal beam. Between the upper support rope 51 and the lower support rope 52, several adjusting rods 6 are also vertically arranged. The upper end of the adjusting rod 6 is connected to the top of the upper support rope 51 or the diagonal steel column 1 through turnbuckles, and the lower end is connected to the lower support rope 52. It is used to tension and adjust the verticality and flatness of the protective netting.

[0028] The protective net assembly is suspended on a support frame consisting of multiple diagonal steel columns 1 and upper and lower support ropes 51 and 52 connected therebetween. It includes a main protective steel rope net 7 on the outer side and a secondary grid net 8 on the inner side. The main protective steel rope net 7 is woven from high-strength steel wire rope into a diamond-shaped mesh and is fixed to the upper and lower support ropes 51 and 52 by stitching ropes. The secondary grid net 8 is woven from steel wire into a small mesh structure, and its edges are pressed against the inner side of the main protective steel rope net 7 and fixed by tie wires.

[0029] The installation and construction process of this utility model is as follows: 1. Measurement and Positioning and Foundation Construction: Based on the design drawings, determine the location of the bearing-type shallow foundation 3 at the lower end of each diagonal steel column 1. Excavate the foundation pit to the stable stratum, pour the concrete cushion layer 31, tie the reinforcing bars, pre-embed anchor bolts 32, and then pour the foundation concrete.

[0030] 2. Install the hinged base and the diagonal bracing steel column: After the foundation concrete reaches its strength, install the lower hinge plate 21 of the hinged base 2 onto the pre-embedded anchor bolts 32 and tighten them. Connect the upper hinge plate 22 and the lower hinge plate 21 at the lower end of the diagonal bracing steel column 1 through the pin 23. At this time, the steel column can rotate freely around the pin 23.

[0031] 3. Construction of the inclined anchor rod: Determine the hole position and angle (β=45°) of the inclined anchor rod 4 behind the upper end of the inclined steel column 1. Then, drill and clean the hole, insert a precision-rolled threaded steel bar as the rod body, and then use a grouting pump to inject cement mortar into the hole to ensure that the grout is full.

[0032] 4. Tensioning and fixing: After the grout strength reaches the design requirements, the inclined anchor rod 4 is tensioned to apply prestress, and its anchor is firmly connected to the top of the inclined steel column 1, so that the entire support structure forms a pre-stressed stable system.

[0033] 5. Install the support rope system: Install the upper support rope 51 connecting the top of each steel column and the lower support rope 52 connecting the middle and lower parts of each steel column in sequence.

[0034] 6. Install the protective netting: First, install the secondary grid netting 8, then lay the main protective steel rope netting 7. Use sewing rope to firmly sew the steel rope netting to the upper and lower support ropes.

[0035] 7. Final adjustment: Adjust the flatness and verticality of the net surface by adjusting the turnbuckle on the suspension rod 6 and tightening the lower support rope 52.

[0036] Other aspects of this utility model that are not detailed herein are all conventional techniques known to those skilled in the art.

[0037] It should be noted that the terms “comprising,” “including,” or any other variations are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0038] The scope of protection of this utility model is not limited to the technical solutions disclosed in the specific embodiments. Any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of this utility model shall fall within the scope of protection of this utility model.

Claims

1. A cantilevered passive protection netting system suitable for tunnel entrances, characterized in that: The system includes a support structure, an anchoring structure, and a protective net assembly. The support structure includes multiple inclined steel columns (1) spaced apart above the tunnel entrance, with the inclined steel columns (1) inclined relative to the slope. The anchoring structure includes a pressure-bearing shallow foundation (3) and a prestressed inclined anchor rod (4). The pressure-bearing shallow foundation (3) is embedded in the stable part of the slope at the lower end of the inclined steel column (1), and the lower end of the inclined steel column (1) is hinged to the pressure-bearing shallow foundation (3) through a hinged base (2). One end of the prestressed inclined anchor rod (4) is anchored in the stable soil layer behind the upper end of the inclined steel column (1), and the other end is tensioned and connected to the upper end of the inclined steel column (1). The protective net assembly is hung on a support frame consisting of multiple inclined steel columns (1) and upper support ropes (51) and lower support ropes (52) connected therebetween.

2. The cantilevered passive protection net system suitable for tunnel entrances according to claim 1, characterized in that: The angle α between the axis of the diagonal bracing steel column (1) and the horizontal plane is 10° to 30°.

3. A cantilevered passive protection net system suitable for tunnel entrances according to claim 1, characterized in that: The hinge base (2) includes a lower hinge plate (21) fixed on the pressure-bearing shallow buried foundation (3) and an upper hinge plate (22) fixed on the lower end of the diagonal bracing steel column (1). The lower hinge plate (21) and the upper hinge plate (22) are connected by a horizontally arranged pin (23), so that the diagonal bracing steel column (1) can rotate slightly around the pin (23) in a plane perpendicular to the slope.

4. A cantilevered passive protection net system suitable for tunnel entrances according to claim 3, characterized in that: The pressure-bearing shallow foundation (3) is a cast-in-place reinforced concrete structure with a base depth of not less than 1.5 meters and a concrete pad layer (31) laid at the bottom; anchor bolts (32) for connecting the hinged base (2) are pre-embedded in the foundation.

5. A cantilevered passive protection net system suitable for tunnel entrances according to claim 4, characterized in that: The angle β between the axis of the prestressed inclined anchor rod (4) and the axis of the inclined steel column (1) is 30° to 60°.

6. A cantilevered passive protection net system suitable for tunnel entrances according to claim 1, characterized in that: The upper support rope (51) is connected to the top of all the diagonal bracing steel columns (1) to form the main load-bearing longitudinal beam; the lower support rope (52) is connected to the middle and lower part of all the diagonal bracing steel columns (1) to form the auxiliary stabilizing longitudinal beam.

7. A cantilevered passive protection net system suitable for tunnel entrances according to claim 6, characterized in that: Between the upper support rope (51) and the lower support rope (52), several adjusting rods (6) are also vertically arranged. The upper end of the adjusting rod (6) is connected to the top of the upper support rope (51) or the diagonal steel column (1) by turnbuckle, and the lower end is connected to the lower support rope (52) for tensioning and adjusting the verticality and flatness of the protective net surface.

8. A cantilevered passive protection net system suitable for tunnel entrances according to claim 1, characterized in that: The protective net assembly includes a main protective steel rope net (7) located on the outer side and a secondary grid net (8) located on the inner side; the main protective steel rope net (7) is woven from high-strength steel wire rope into a diamond-shaped mesh and is fixed to the upper support rope (51) and the lower support rope (52) by sewing rope; the secondary grid net (8) is woven from steel wire into a small mesh structure, and its edge is pressed against the inner side of the main protective steel rope net (7) and fixed by tie wire.

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