Tunnel advance support structure

Abstract

The utility model provides a kind of tunnel advance support structure, it is related to tunnel engineering technical field, the tunnel advance support structure includes multiple grouting small catheter and multiple grouting middle catheter being arranged along tunnel section ring and front end being inserted into tunnel vault surrounding rock interior by drilling;The outer diameter of the grouting middle catheter is greater than the outer diameter of the grouting small catheter;The grouting middle catheter and the grouting small catheter are staggered along tunnel section ring arrangement.The utility model has alleviated the technical problem that reinforcing arch shell thickness is limited, support spacing is larger, and small catheter front end anchoring section (force layer) length is shorter in the single small catheter tunnel advance support structure of prior art, and it is difficult to build continuous stable bearing arch structure.

Description

Technical Field

[0001] This utility model relates to the field of tunnel engineering technology, and in particular to a tunnel pre-support structure. Background Technology

[0002] Pre-support refers to a technical method of reinforcing the surrounding rock in advance before excavation at the tunnel face. During the construction of pre-support in sections with adverse geological conditions, the surrounding rock mass has well-developed structural planes and bedding planes, poor bonding between structural planes, fractured to extremely fractured rock mass, highly developed joints and fissures, and poor integrity and self-stabilizing ability. The arch is extremely prone to collapse, making pre-support construction crucial.

[0003] Existing tunnel pre-support methods primarily employ small-diameter pipe grouting. This involves drilling holes around the tunnel face, installing small-diameter steel pipes, and then injecting grout. The grout penetrates the surrounding rock fissures, creating a locally reinforced zone to improve the strength and integrity of the surrounding rock. This technique is characterized by simple equipment, flexible operation, and strong adaptability, and has been widely used in various tunnel projects.

[0004] However, due to inherent limitations in the design and construction of single small-diameter pipe support, the resulting reinforced arch shell has limited thickness, large support spacing, and a short anchorage section (bearing layer) at the front end of the small-diameter pipe, resulting in insufficient effective reinforcement range. The strength and stiffness of the resulting pre-supported arch shell structure are both low, making it difficult to construct a continuous and stable load-bearing arch structure. During pre-support construction in adverse geological sections, relying solely on single small-diameter pipe support is insufficient to effectively control surrounding rock deformation. The surrounding rock in front of the tunnel face is still prone to significant displacement and deformation, leading to instability and face collapse, resulting in rework and work stoppages. This poses a high safety risk during construction. Utility Model Content

[0005] The purpose of this utility model is to provide a tunnel pre-support structure to alleviate the technical problems of the existing single small pipe tunnel pre-support structure, such as limited thickness of the reinforced arch shell, large support spacing, and short length of the anchoring section (bearing layer) at the front end of the small pipe, which makes it difficult to construct a continuous and stable load-bearing arch structure.

[0006] To achieve the above objectives, the embodiments of this utility model adopt the following technical solutions: This utility model embodiment provides a tunnel pre-support structure, which includes multiple grouting small guide pipes and multiple grouting medium guide pipes arranged circumferentially along the tunnel cross section and inserted into the surrounding rock of the tunnel arch through boreholes at their front ends; The outer diameter of the grouting conduit is larger than the outer diameter of the grouting small conduit; the grouting conduit and the grouting small conduit are arranged alternately along the tunnel cross section.

[0007] In an optional embodiment, along the radial direction of the tunnel cross section: the drilling position of the grouting conduit in the surrounding rock layer of the tunnel arch is located outside the drilling position of the grouting small conduit in the surrounding rock layer of the tunnel arch.

[0008] In an optional embodiment, the drilling direction of the grouting pipe in the surrounding rock layer of the tunnel arch has an external insertion angle θ1 with the tunnel axis, satisfying: 5°≤θ1≤12°; The drilling direction of the guide pipe in the surrounding rock layer of the tunnel arch during grouting has an external insertion angle θ2 with the tunnel axis, satisfying: 10°≤θ2≤30°.

[0009] In an optional embodiment, the outer diameter d1 of the grouting conduit is 42 mm and the wall thickness t1 is 4 mm; the outer diameter d2 of the grouting conduit is 76 mm and the wall thickness t2 is 6 mm.

[0010] In an optional embodiment, the length L1 of the grouting conduit is 4.5m; and the length L2 of the grouting conduit is 6.0m.

[0011] In an optional embodiment, the borehole diameter corresponding to the grouting small guide pipe is d3, the outer diameter of the grouting small guide pipe is d1, the borehole diameter corresponding to the grouting middle guide pipe is d4, and the outer diameter of the grouting middle guide pipe is d2, satisfying: 20mm≤d3-d1≤30mm, 20mm≤d4-d2≤30mm; Let L3 be the depth of the borehole corresponding to the grouting small guide pipe, L1 be the length of the grouting small guide pipe, L4 be the depth of the borehole corresponding to the grouting middle guide pipe, and L2 be the length of the grouting middle guide pipe, satisfying: 10mm≤L3-L1≤20mm, 10mm≤L4-L2≤20mm.

[0012] In an optional embodiment, the front end of both the grouting conduit and the grouting conduit are conical.

[0013] In an optional embodiment, the upper front end of the grouting conduit and the grouting small conduit are respectively provided with a plurality of grouting holes, and the plurality of grouting holes are arranged in a staggered quincunx pattern along the axial direction and circumferential direction of the corresponding conduit.

[0014] In an optional embodiment, both the grouting small guide tube and the grouting middle guide tube are made of hot-rolled seamless steel pipe.

[0015] In an optional embodiment, the surrounding rock of the tunnel arch is provided with initial support, and the tail ends of the grouting conduit and the grouting small conduit are both on the initial support.

[0016] The embodiments of this utility model can achieve at least the following beneficial effects: The tunnel pre-support structure provided in this embodiment includes multiple grouting small pipes and multiple grouting medium pipes arranged circumferentially along the tunnel cross section and inserted into the surrounding rock of the tunnel arch through boreholes at their front ends; the outer diameter of the grouting medium pipes is larger than the outer diameter of the grouting small pipes; the grouting medium pipes and the grouting small pipes are arranged alternately along the tunnel cross section.

[0017] This utility model embodiment can be widely applied to various types of tunnels, especially in the construction of advanced support for tunnels with large deformation in loose soft rock. During construction, by adopting a combination of grouting guide pipes and grouting small guide pipes for tunnel advanced support, the distance between the guide pipes for advanced support is further reduced, the length of the bearing layer at the front end of the advanced support is increased, and the strength and stiffness of the advanced support arch shell structure are both high. After grouting, the surrounding rock and cement mortar within a certain range form an arch shell structure with a certain strength, which plays the role of bearing arch, improves the stability of the surrounding rock in front of the tunnel face, thereby effectively reducing the displacement problem of the surrounding rock after the excavation of the tunnel face, ensuring the quality of the construction process, reducing the risk of tunnel face instability and collapse during construction, and improving the safety of the construction process.

[0018] In addition, this utility model embodiment also provides several optional implementation methods. The specific implementation method section of this specification will provide a detailed description and explanation of the specific structure and functional effects of these optional implementation methods. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 Elevation view of the construction method of the tunnel pre-support structure provided in this embodiment of the utility model; Figure 2 for Figure 1 AA cross-section diagram.

[0021] Icons: 1- Grouting guide pipe; 2- Grouting small guide pipe; 3- Initial support; 4- Reserved deformation amount; 5- Secondary lining. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments 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. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0024] It should be noted that similar labels and letters in the accompanying drawings indicate similar items. Therefore, once an item is defined in one accompanying drawing, it does not need to be further defined and explained in subsequent accompanying drawings.

[0025] In the description of this utility model, it should be noted that the terms "upper," "lower," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this utility model is in use. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0026] Furthermore, the terms "horizontal" and "vertical" do not imply that the component must be absolutely horizontal or suspended, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0027] In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0028] The following detailed description, in conjunction with the accompanying drawings, outlines some embodiments of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0029] This embodiment provides a tunnel pre-support structure, referring to... Figure 1 and Figure 2 During construction, the surrounding rock layer of the tunnel arch is provided with secondary lining 5, and the outer layer of secondary lining 5 is provided with initial support 3 (usually steel frame). There is a reserved deformation amount 4 between secondary lining 5 and initial support 3.

[0030] The tunnel pre-support structure includes multiple small grouting pipes 2 and multiple medium grouting pipes 1 arranged circumferentially along the tunnel cross section and inserted into the surrounding rock of the tunnel arch through boreholes at their front ends; the outer diameter of the medium grouting pipe 1 is larger than the outer diameter of the small grouting pipes 2; the medium grouting pipes 1 and the small grouting pipes 2 are arranged alternately along the tunnel cross section.

[0031] The construction steps mainly include drilling, installation, and grouting. During drilling, a total station or laser guidance instrument is used to determine the drilling position, with an error ≤5cm. A pneumatic rock drill or down-the-hole drill is used. The drilling speed is controlled during drilling to avoid jamming or hole collapse. Residual material in the hole is cleaned promptly. After drilling, the hole is flushed with high-pressure air or water to ensure no debris blockage. During installation, the front ends of each grouting conduit and each grouting pipe are inserted into the surrounding rock of the tunnel arch through their respective drill holes. Each grouting conduit and each grouting pipe has a grouting hole at its front end. During grouting, grouting material is injected into each grouting conduit and each grouting pipe. The grouting material flows out from the grouting holes at the front ends of each grouting conduit and each grouting pipe and seeps into the surrounding rock fissures, forming a localized reinforced zone to improve the strength and integrity of the surrounding rock. Generally, single-component cement grout is used as the grouting material, with preliminary parameters as follows: water-cement ratio w / c = 0.6–0.8, cement grout / water glass = 1:0.05 (volume ratio), water glass concentration = 35–40°Bé, water glass modulus m = 2.6, and ordinary Portland cement with a strength grade of 42.5. During construction, reasonable grouting parameters should be determined based on on-site tests. When groundwater levels are high, a cement-water glass two-component grout is used, with preliminary parameters as follows: cement grout / water glass = 1:0.8 (volume ratio), and the remaining parameters are the same as for single-component cement grout. Grouting should proceed from bottom to top, from single-component grout to two-component grout, and from thinner to thicker grout. Grouting volume is primarily controlled by pressure, with volume control as a secondary measure. The grouting pressure is 0.5–1 MPa. Grouting can be stopped after the grouting pressure in each hole reaches 1.0 MPa and is maintained for at least 10 minutes.

[0032] This embodiment can be widely applied to various types of tunnels, especially in the construction of advanced support for tunnels with large deformation in loose soft rock. During construction, by adopting a combination of grouting guide pipes and grouting small guide pipes for advanced tunnel support, the distance between the guide pipes for advanced support is further reduced, the length of the bearing layer at the front end of the advanced support is increased, and the strength and stiffness of the advanced support arch structure are both high. After grouting, the surrounding rock and cement mortar within a certain range form an arch structure with a certain strength, which plays the role of a load-bearing arch, improves the stability of the surrounding rock in front of the tunnel face, thereby effectively reducing the displacement of the surrounding rock after the tunnel face is excavated, ensuring the quality of the construction process, reducing the risk of tunnel face instability and collapse during construction, and improving the safety of the construction process.

[0033] Specifically, this structure achieves multiple technological breakthroughs without significantly increasing construction difficulty by arranging the larger-diameter grouting conduit and the smaller-diameter grouting conduit in a staggered pattern along the tunnel cross-section. (1) Enhancing the integrity and structural stiffness of the pre-support arch shell: The large-diameter grouting guide pipe, as the main load-bearing unit, significantly enhances the anchorage depth and bending resistance of the pre-support front end in the surrounding rock; while the small grouting guide pipe fills the gaps between the grouting guide pipes, effectively reducing the spacing between the guide pipes and increasing the support density. Under the synergistic effect of the two, a more continuous and dense "arch shell" structure is formed, which significantly improves the pre-support stiffness and overall stability of the surrounding rock in front of the tunnel face; (2) Expand the effective bearing layer range and enhance the front bearing capacity: As the grouting pipe is inserted deeper and has a larger cross section, the volume of the grouting solidified body formed in the surrounding rock is larger, and it overlaps and permeates with the grouting area of ​​the surrounding small grouting pipe, so that the grouting affected area is connected into one, forming a composite bearing arch with a certain thickness and strength. This structure can bear part of the ground pressure before excavation, which significantly alleviates the stress concentration problem during the period when the secondary lining behind the tunnel face is not closed. (3) Optimize the stress transmission path of the surrounding rock and suppress the development of non-uniform deformation: The design of the circumferential staggered arrangement avoids the weak interface that may be generated by the arrangement of the same specification guide pipes, so that the support structure is more uniformly stressed in the circumferential direction, effectively preventing the occurrence of local shear failure or buckling instability. Especially in soft and broken surrounding rock, it can significantly delay the expansion rate of the plastic zone and control the initial displacement. (4) Improve grouting diffusion efficiency and reinforcement uniformity: The grouting pressure field distribution is different due to the difference in diameter between the grouting conduit and the grouting small conduit. In the same grouting stage, graded penetration can be achieved. The grouting conduit dominates deep fracturing grouting, while the grouting small conduit focuses on shallow filling grouting, thus forming a three-dimensional reinforcement network of "internal and external coordination and deep and shallow combination", which greatly improves the overall mechanical properties of the surrounding rock.

[0034] In summary, this embodiment not only overcomes the shortcomings of traditional single small guide pipe support such as large spacing, low stiffness, and easy hole collapse, but also avoids the problems of high cost and drilling difficulties caused by the use of guide pipes in the whole section. It achieves a good balance between economy and safety, and greatly improves the safety level of tunnel construction in soft surrounding rock.

[0035] Furthermore: In an optional embodiment of this example, along the radial direction of the tunnel cross section: the drilling position of the grouting guide pipe 1 in the surrounding rock layer of the tunnel arch is located outside the drilling position of the grouting small guide pipe 2 in the surrounding rock layer of the tunnel arch.

[0036] In an optional embodiment of this example, the drilling direction of the grouting guide pipe 2 in the surrounding rock layer of the tunnel arch has an external angle θ1 with the tunnel axis (the external angle is a standard technical term used when the guide pipe is used for advance support construction during tunnel advance support, and its design direction can be clearly obtained by those skilled in the art), satisfying: 5°≤θ1≤12°, where θ1 can be any angle between 5°, 10°, 12° or 5°~12°; during grouting, the drilling direction of the guide pipe 1 in the surrounding rock layer of the tunnel arch has an external angle θ2 with the tunnel axis, satisfying: 10°≤θ2≤30°, where θ2 can be any angle between 10°, 20°, 30° or 10°~30°. In this embodiment, the outer insertion angle θ1 of the small guide pipe, satisfying 5°≤θ1≤12°, helps the grouting material to be evenly distributed in the shallow surrounding rock, forming a relatively dense solidified body and improving the overall stability of the surrounding rock in front of the tunnel face. The outer insertion angle θ2 of the medium guide pipe, satisfying 10°≤θ2≤30°, allows the grouting material to penetrate deeper into the surrounding rock, forming a more robust deep solidified body. This design with different outer insertion angles not only improves the grouting effect but also enhances the front-end bearing capacity, forming a more uniform support system in the tunnel arch surrounding rock, effectively resisting the lateral pressure of the surrounding rock, reducing the displacement of the surrounding rock after excavation of the tunnel face, and improving stability during construction.

[0037] In an optional embodiment of this example, the outer diameter d1 of the grouting conduit 2 is 42 mm and the wall thickness t1 is 4 mm; the outer diameter d2 of the grouting conduit 1 is 76 mm and the wall thickness t2 is 6 mm.

[0038] In an optional embodiment of this example, the length L1 of the grouting conduit 2 is 4.5m; and the length L2 of the grouting conduit 1 is 6.0m.

[0039] To ensure smooth insertion of the guide pipe into the borehole and sufficient clearance for grouting, thus avoiding blockage, in an optional embodiment of this example, the borehole diameter corresponding to the grouting guide pipe 2 is d3, the outer diameter of the grouting guide pipe 2 is d1, the borehole diameter corresponding to the grouting conduit 1 is d4, and the outer diameter of the grouting conduit 1 is d2, satisfying: 20mm≤d3-d1≤30mm, 20mm≤d4-d2≤30mm; the borehole depth corresponding to the grouting guide pipe 2 is L3, the length of the grouting guide pipe 2 is L1, the borehole depth corresponding to the grouting conduit 1 is L4, and the length of the grouting conduit 1 is L2, satisfying: 10mm≤L3-L1≤20mm, 10mm≤L4-L2≤20mm.

[0040] In addition, in an optional embodiment of this example, the front end of the grouting small guide tube 2 and the front end of the grouting medium guide tube 1 are both cone-shaped. This structure facilitates the penetration of the front ends of the grouting small guide tube 2 and the grouting medium guide tube 1 into the surrounding rock, reduces resistance, and facilitates installation. At the support position, they can be further tied with binding materials such as steel wires or fixed with clamps to further increase the structural stability.

[0041] In an optional embodiment of this example, the front ends of the grouting conduit 1 and the grouting small conduit 2 are respectively provided with multiple grouting holes. The multiple grouting holes are arranged in a staggered quincunx pattern along the axial direction and circumferential direction of the corresponding conduit. This design allows the grout to spread evenly in all directions when it flows out of the corresponding conduit, thereby improving the grouting effect.

[0042] In an optional embodiment of this example, both the grouting small guide tube 2 and the grouting middle guide tube 1 are made of hot-rolled seamless steel pipe to ensure the strength and durability of the guide tubes.

[0043] In an optional embodiment of this example, the surrounding rock of the tunnel arch is provided with initial support 3, and the tail ends of the grouting guide pipe 1 and the grouting small guide pipe 2 are supported on the initial support 3, thereby enhancing the support effect and further improving the safety and stability of the tunnel's advanced support structure.

[0044] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to mutually. The above embodiments in this specification 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 or all of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of this utility model.

Claims

1. A tunnel pre-support structure, characterized in that, The tunnel pre-support structure includes multiple grouting small guide pipes (2) arranged circumferentially along the tunnel cross section and inserted into the surrounding rock of the tunnel arch through boreholes at the front end, and multiple grouting medium guide pipes (1). The outer diameter of the grouting conduit (1) is larger than the outer diameter of the grouting small conduit (2); the grouting conduit (1) and the grouting small conduit (2) are arranged alternately along the tunnel cross section.

2. The tunnel advance support structure according to claim 1, characterized in that, Along the radial direction of the tunnel cross section: the grouting guide pipe (1) is located at the outer layer of the drilling position of the grouting small guide pipe (2) in the surrounding rock layer of the tunnel arch.

3. The tunnel advance support structure according to claim 1, characterized in that, The grouting pipe (2) has an external insertion angle θ1 with the tunnel axis in the drilling direction of the surrounding rock layer at the tunnel arch, satisfying: 5°≤θ1≤12°; The drilling direction of the guide pipe (1) in the tunnel arch surrounding rock layer has an external insertion angle θ2 with the tunnel axis, satisfying: 10°≤θ2≤30°.

4. The tunnel advance support structure according to claim 1, characterized in that, The outer diameter d1 of the grouting conduit (2) is 42 mm and the wall thickness t1 is 4 mm; the outer diameter d2 of the grouting conduit (1) is 76 mm and the wall thickness t2 is 6 mm.

5. The tunnel advance support structure according to claim 1, characterized in that, The length L1 of the grouting conduit (2) is 4.5m; the length L2 of the grouting conduit (1) is 6.0m.

6. The tunnel advance support structure according to claim 1, characterized in that, With the borehole diameter corresponding to the grouting conduit (2) as d3, the outer diameter of the grouting conduit (2) as d1, the borehole diameter corresponding to the grouting conduit (1) as d4, and the outer diameter of the grouting conduit (1) as d2, the following conditions are met: 20mm≤d3-d1≤30mm, 20mm≤d4-d2≤30mm; Let the depth of the borehole corresponding to the grouting conduit (2) be L3, the length of the grouting conduit (2) be L1, the depth of the borehole corresponding to the grouting conduit (1) be L4, and the length of the grouting conduit (1) be L2, satisfying: 10mm≤L3-L1≤20mm, 10mm≤L4-L2≤20mm.

7. The tunnel advance support structure according to claim 1, characterized in that, The front end of the grouting small conduit (2) and the front end of the grouting medium conduit (1) are both conical.

8. The tunnel advance support structure according to claim 1, characterized in that, The grouting conduit (1) and the grouting small conduit (2) are respectively provided with multiple grouting holes at their front ends. The multiple grouting holes are arranged in a staggered quincunx pattern along the axial direction and circumferential direction of the corresponding conduit.

9. The tunnel advance support structure according to claim 1, characterized in that, Both the grouting small guide tube (2) and the grouting middle guide tube (1) are made of hot-rolled seamless steel pipe.

10. The tunnel advance support structure according to claim 1, characterized in that, The tunnel arch surrounding rock is provided with initial support (3), and the tail ends of the grouting conduit (1) and the grouting small conduit (2) are supported on the initial support (3).

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