Double rigid support small section tunnel collapse support method

Abstract

This invention discloses a method for supporting small-section tunnels in the event of collapse with double rigid support. The structure implementing this support includes cement mortar system anchors, grouting pipes, concrete, pre-drilled holes for pre-drilled small guide pipes, steel arch frames, cement mortar anchor bolts, threaded steel bars, tunnel steel arch frames, shotcrete grout curtains, tunnel face, and reinforcing bars. Due to the use of a nested combination of pre-drilled small guide pipes and reinforcing bars, and the circumferential connection between the nested pre-drilled small guide pipes using threaded steel bars, an arch-shaped protection is formed at the tunnel arch crown, which acts as a load-bearing arch and effectively prevents the intrusion of collapsed rocks into the tunnel cross-section clearance. Below the load-bearing arch, a row of circumferential pre-drilled small guide pipes is installed for grouting, forming a "double rigid support" support combination system together with the load-bearing arch, thus optimizing the reinforcement effect.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering technology, specifically to a method for supporting small-section tunnel collapses with double rigid support. Background Technology

[0002] Current research on tunnel collapse management and support primarily focuses on large-section tunnels, with fewer targeted methods for managing collapses in small-section tunnels. The collapse problem in small-section tunnels differs from that in large-section tunnels. Due to their smaller cross-sectional area, a collapse in a small-section tunnel can result in the complete destruction of all pre-excavation support measures, such as arch collapse, anchor bolt bending and breakage, and large-scale damage to shotcrete. This can lead to the entire tunnel face being buried in the collapsed rubble, posing a serious threat to the lives of construction workers and severely impacting project progress. Compared to larger-section tunnels, small-section tunnel collapses are characterized by rapid development and destruction. Essentially, all previous excavation and support work on the entire section will be rendered useless and must be restarted. Therefore, it is necessary to research effective, efficient, and targeted support methods for collapse-prone sections of small-section tunnels.

[0003] Current collapse support methods mainly include grouting reinforcement, advanced small guide pipes, and pipe roof support. However, in actual construction, these methods still suffer from drawbacks such as low grout injection efficiency, failure to inject grout on schedule, and outflow through grouting holes, resulting in unsatisfactory support effects. Previous studies have also used methods to control the grouting sequence and pressure, but due to the inconsistent distribution of rock fissures and other indicators in tunnels with different surrounding rock conditions, the effective diffusion range of the grout is unknown. Furthermore, the grouting pressure and sequence require repeated trials to achieve relatively good results, which is time-consuming and labor-intensive. In the construction of small-section tunnels, due to the small tunnel cross-section, limited operating space, and fractured surrounding rock when crossing fractured zones, on-site workers are at risk of collapse at any time. It is necessary to carry out construction as quickly as possible while ensuring project quality. Therefore, the above methods are not applicable to small-section tunnels. To address this, a double rigid support method for small-section tunnel collapse support is proposed. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a method for supporting small-section tunnels with double rigid support in case of collapse. Addressing the deficiencies of existing technologies and their inapplicability to the support methods and construction concepts for small-section tunnels, this application effectively solves the problems of poor grouting effect, high support difficulty, and collapse risk during arch erection in small-section tunnels located in collapse areas.

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for supporting small-section tunnel collapses with double rigid support, wherein the structure implementing the support includes cement mortar system anchor bolts, grouting pipe guides, concrete, pre-drilled holes for advanced small guide pipes, steel arch frames, cement mortar anchor bolts, threaded steel bars, tunnel steel arch frames, shotcrete grout-stopping curtains, tunnel face, and reinforcing bars, and the method includes the following steps:

[0008] A1. Initial support;

[0009] A2. Composition of advanced small guide tubes: Advanced small guide tubes formed by the combination and nesting of grouting pipe guide tubes and steel bars are driven into the reserved holes of advanced small guide tubes.

[0010] A3. Complete the first layer of "rigid support" by using threaded steel to circumferentially connect the nested pre-conduit pipes installed in step A2.

[0011] A4. Install grouting pipes;

[0012] A5. Closed working face;

[0013] A6. Support and sealing;

[0014] A7. Complete the second layer of "rigid support" by performing grouting through the grouting pipe in step A4;

[0015] A8. Proceed with the next cycle of excavation.

[0016] Preferably, as described in step A1, after the cross-section excavation is completed, cement mortar system anchors and steel arches are installed inside the tunnel steel arch for conventional initial support.

[0017] Initial support includes steel arch frames, steel mesh, and system anchor bolts;

[0018] The steel arch frame is made of I16 steel, and the steel bars are connected at a spacing of 0.5m, with a row spacing of 0.5×0.5m.

[0019] The steel arch frame is connected to the cement mortar anchor rod by welding. The cement mortar anchor rod is HRB400φ22M20 with L=2.5m.

[0020] The parameters of the cement mortar system anchor rods are HRB400φ22M20, L=3.5m, and they are arranged in a quincunx pattern with a spacing of 50×100cm.

[0021] Preferably, as proposed in step A2, an advanced small guide tube, which is formed by the combination and nesting of the grouting pipe guide tube and the reinforcing bar, is driven into the reserved hole of the advanced small guide tube, wherein the connection method between the grouting pipe guide tube and the reinforcing bar is spot welding, the diameter of the grouting pipe guide tube is φ42, and the diameter of the reinforcing bar is φ22.

[0022] Preferably, as proposed in step A3, the nested advanced small guide tubes installed in step A2 are circumferentially connected by threaded steel bars, and the connection method is welding. This completes the first layer of "rigid support". The diameter of the threaded steel bars is φ16.

[0023] Preferably, as proposed in step A5, shotcrete is applied to the area above the arch line of the tunnel face. The concrete type is C25, the thickness is 18cm, and it is overlapped with a steel mesh of type HPB300φ8 with a mesh size of 20×20cm. After sealing, a layer of shotcrete-stopping curtain will be formed on the surface of the tunnel face.

[0024] Preferably, the initial support that has been implemented is sealed, as proposed in step A6.

[0025] Preferably, as proposed in A7, grouting is performed through the grouting pipe in step A4 to complete the grouting reinforcement as a second layer of "rigid support".

[0026] (III) Beneficial Effects

[0027] Compared with the prior art, the present invention provides a method for supporting small-section tunnel collapses with double rigid support, which has the following beneficial effects:

[0028] 1. Due to the adoption of the pre-embedded small guide pipe + steel bar nested combination, and the use of threaded steel bars for circumferential connection between the nested pre-embedded small guide pipes, an arch-shaped protection is formed at the tunnel arch, which plays the role of load-bearing arch and effectively prevents the intrusion of collapse and falling rocks into the tunnel cross-section clearance.

[0029] 2. A row of circumferential advanced small guide pipes was installed below the load-bearing arch for grouting, forming a "double rigid support" support combination system together with the load-bearing arch, which optimized the reinforcement effect;

[0030] 3. By using shotcrete to spray concrete on the part above the arch line of the tunnel face, a layer of shotcrete-stopping curtain will be formed on the surface of the sealed tunnel face. This prevents the grout from flowing out of the borehole of the advance guide pipe, making more efficient use of the grout and effectively preventing poor reinforcement effect caused by grout overflow and leakage. This saves construction costs and improves construction efficiency. Attached Figure Description

[0031] Figure 1 This is a front view of the collapse support structure of the present invention;

[0032] Figure 2 This is a diagram showing the arrangement of the grout-stopping curtain at the working face of the present invention.

[0033] Figure 3This is a front view of the nested advanced small catheter of the present invention;

[0034] Figure 4 This is a three-dimensional schematic diagram of the nested advanced small catheter of the present invention;

[0035] Figure 5 This is a schematic diagram of the nested advanced small catheter circumferential connection of the present invention;

[0036] Figure 6 This is a flowchart illustrating the steps of the present invention.

[0037] In the diagram: 1. Cement mortar system anchor bolt; 2. Grouting pipe guide; 3. Concrete; 4. Pre-drilled hole for advanced small guide pipe; 5. Steel arch frame; 6. Cement mortar locking anchor bolt; 7. Threaded steel bar; 8. Tunnel steel arch frame; 9. Shotcrete grout-stopping curtain; 10. Working face; 11. Reinforcing steel bar. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] This invention provides a technical solution, such as Figure 1-6 As shown, a method for supporting small-section tunnel collapses with double rigid support is described. The structure implementing this support includes cement mortar system anchors 1, grouting pipes 2, concrete 3, pre-drilled holes for advanced small guide pipes 4, steel arch frame 5, cement mortar anchor bolts 6, threaded steel bars 7, tunnel steel arch frame 8, shotcrete grout-stopping curtain 9, tunnel face 10, and reinforcing bars 11. The method includes the following steps:

[0040] A1. Initial support;

[0041] A2. Composition of the advanced small guide tube: An advanced small guide tube formed by the combination and nesting of the grouting pipe guide tube 2 and the steel bar 11 is driven into the reserved hole 4 of the advanced small guide tube.

[0042] A3. Complete the first layer of "rigid support" by using threaded steel bar 7 to circumferentially connect the nested advanced small guide tubes installed in step A2.

[0043] A4. Implement grouting pipe guide 2;

[0044] A5. Closed working face;

[0045] A6. Support and sealing;

[0046] A7. Complete the second layer of "rigid support" by performing grouting through the grouting pipe 2 in step A4;

[0047] A8. Proceed with the next cycle of excavation.

[0048] Furthermore, as described in step A1, after the cross-section excavation is completed, cement mortar system anchor bolts 1 and steel arch frame 5 are installed inside the tunnel steel arch frame 8 for conventional initial support.

[0049] 5. Initial support including steel arch frame, steel mesh, and system anchor bolts;

[0050] Among them, the steel arch frame 5 is made of I16 steel, and the steel bars are connected at a spacing of 0.5m with a row spacing of 0.5×0.5m.

[0051] The steel arch frame 5 is connected to the cement mortar anchor rod 6 by welding. The cement mortar anchor rod 6 is HRB400φ22M20 with L=2.5m.

[0052] The parameters of anchor rod 1 in the cement mortar system are HRB400φ22M20, L=3.5m, and it is arranged in a quincunx pattern with a spacing of 50×100cm.

[0053] Furthermore, as proposed in step A2, a [material / material] is inserted into the pre-drilled hole 4 of the advanced small catheter. Figure 3 The grouting pipe 2 and the reinforcing bar 11 are nested together to form a pre-embedded small guide tube. The connection between the grouting pipe 2 and the reinforcing bar 11 is spot welded. The diameter of the grouting pipe 2 is φ42, and the diameter of the reinforcing bar 11 is φ22. To better understand the appearance and nesting form of the nested pre-embedded small guide tube, a three-dimensional schematic diagram of the specific nested pre-embedded small guide tube is shown below. Figure 4 As shown.

[0054] Furthermore, as proposed in step A3, the nested pre-conduit pipes installed in step A2 are circumferentially connected using threaded steel bar 7 via welding. This completes the first layer of "rigid support." The diameter of threaded steel bar 7 is φ16. A detailed connection diagram of the load-bearing arch is shown below. Figure 5 As shown.

[0055] Furthermore, perform Figure 1 Grouting pipe guide 2 in the middle,

[0056] Furthermore, as proposed in step A5, sprayed concrete 3 is applied to the portion of the face 10 above the arch line. The concrete 3 is of type C25 and has a thickness of 18cm. It is overlapped with a steel mesh of type HPB300φ8 with a mesh size of 20×20cm. After sealing, a layer of sprayed concrete stop curtain 9 will be formed on the surface of the face 10.

[0057] Furthermore, as proposed in step A6, the initial support that has been implemented is sealed.

[0058] Furthermore, as proposed in A7, grouting is carried out through the grouting pipe 2 in step A4 to complete the grouting reinforcement as a second layer of "rigid support".

[0059] The working principle of this device is as follows:

[0060] Because of the use of a nested combination of advanced small guide pipes and steel bars 11, and the use of threaded steel bars 7 for circumferential connection between the nested advanced small guide pipes, an arch-shaped protection is formed at the top of the tunnel, which plays the role of a load-bearing arch and effectively prevents the intrusion of landslides and falling rocks into the tunnel cross-section clearance.

[0061] A row of circumferentially advanced small guide pipes was installed below the load-bearing arch for grouting, forming a "double rigid support" support combination system together with the load-bearing arch, which optimized the reinforcement effect;

[0062] By using shotcrete 3 to spray concrete 3 on the part above the arch line of the tunnel face 10, a layer of shotcrete-stopping curtain 9 will be formed on the surface of the sealed tunnel face 10. This prevents the grout from flowing out of the borehole of the advance guide pipe, making more efficient use of the grout. It effectively prevents poor reinforcement effect caused by grout overflow and leakage, saves construction costs and improves construction efficiency.

[0063] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method of supporting a small cross-section tunnel collapse with double rigid support, characterized in that: The structure for implementing the support includes a cement mortar system anchor rod (1), a grouting pipe guide pipe (2), concrete (3), an advanced small guide pipe reserved hole (4), a steel arch (5), a cement mortar locking foot anchor rod (6), a threaded steel (7), a tunnel steel arch (8), a sprayed concrete grouting curtain (9), a working face (10), and a steel bar (11), and the method includes the following steps: A1, initial support; A2, composition of an advanced small guide pipe, the advanced small guide pipe formed by the combination and nesting of the grouting pipe guide pipe (2) and the steel bar (11) is punched into the advanced small guide pipe reserved hole (4); A3, complete the first heavy "rigid support", the nested advanced small guide pipe punched in step A2 is connected in a ring direction by the threaded steel (7), and the connection mode is welding, thereby completing the first heavy "rigid support"; A4, implement the grouting pipe guide pipe (2); A5, close the working face; A6, support closure; A7, complete the second heavy "rigid support", grouting is performed through the grouting pipe guide pipe (2) in step A4, and the grouting reinforcement as the second heavy "rigid support" is completed; A8, perform the next cycle of excavation operation.

2. The method for small cross-section tunnel collapse support of double rigid support according to claim 1, characterized in that: According to step A1, after the excavation of the section is completed, the cement mortar system anchor rod (1) and the steel arch (5) are erected in the tunnel steel arch (8) to perform the conventional initial support; The steel arch (5) is I16 type steel, and the steel bars are connected at an interval of 0.5 m with a row spacing of 0.5*0.5 m; The steel arch (5) is connected with the cement mortar locking foot anchor rod (6) in a welding manner, and the cement mortar locking foot anchor rod (6) is HRB400φ22M20, L=2.5 m; The parameters of the cement mortar system anchor rod (1) are HRB400φ22M20, L=3.5 m, and the cement mortar system anchor rod (1) is arranged in a quincunx shape with an interval of 50*100 cm.

3. The method of claim 1, wherein the method is characterized by: The connection mode of the grouting pipe guide pipe (2) and the steel bar (11) is spot welding, the diameter of the grouting pipe guide pipe (2) is φ42, and the diameter of the steel bar (11) is φ22.

4. The method of claim 1, wherein the method is characterized by: The diameter of the threaded steel (7) is φ16.

5. The method for small cross-section tunnel collapse support by double rigid support according to claim 1, characterized in that: According to step A5, the part above the arch line of the working face (10) is sprayed with concrete (3), the model of the concrete (3) is C25, the thickness is 18 cm, and the steel bar mesh with a model of HPB300φ8 and a mesh size of 20*20 cm is overlapped, and the closed working face (10) forms a layer of sprayed concrete grouting curtain (9) on the surface.

6. The method of claim 1, wherein the method further comprises: According to step A6, the initial support is closed.

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