Tunnel support structure and support construction method thereof

Abstract

The tunnel supporting structure improves that the supporting structure comprises an anchor net, a primary lining covering the anchor net, an arch frame, anchor rods and a secondary lining, wherein the arch frame is laid along the tunnel axis direction at intervals and is arranged on the surface of the primary lining; the arch frame is spliced by a plurality of arch frame segments arranged on the same radial section of the tunnel; and each arch frame segment comprises a plurality of uniformly arranged asphalt steel pipe grid units. The tunnel supporting structure can keep the surrounding rock tunnel rock mass of the outer surface of the soft surrounding rock tunnel in a stable state, improves the structural firmness and stability of the soft surrounding rock tunnel as a whole, reduces the pressure generated by displacement, shaking and sliding of the surrounding rock tunnel rock mass on the tunnel during use of the soft surrounding rock tunnel, and reduces the erosion damage to the supporting structure, thereby affecting the safe use of the soft surrounding rock tunnel.

Description

Technical Field

[0001] This invention belongs to the field of tunnel support technology, specifically relating to a tunnel support structure and its construction method. Background Technology

[0002] During tunnel construction, weak surrounding rock is frequently encountered. The presence of weak surrounding rock poses a significant safety hazard to tunnel construction, and improper or untimely handling can lead to catastrophic consequences. The instability and failure of soft rock tunnels are essentially due to the effect of ground pressure. The secondary stress redistributed after tunnel excavation interacts with the deformation and strength characteristics of the surrounding rock. When the value of the secondary stress exceeds the plastic limit or strength limit of part of the surrounding rock or causes the surrounding rock to enter a significant rheological state, the surrounding rock will undergo significant deformation, cracking, loosening, and failure, exhibiting obvious ground pressure effects. Therefore, tunnel wall support is necessary.

[0003] Based on the above, it is clear that developing a new support structure for soft rock tunnels, along with appropriate construction methods, is of great significance for ensuring the stability of soft rock tunnels with large deformations. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention provides a tunnel support structure and its construction method, aiming to solve or improve at least one of the above-mentioned technical problems, enabling the surrounding rock mass on the outer surface of the weak surrounding rock tunnel to always remain stable, improving the overall structural strength and stability of the weak surrounding rock tunnel, and reducing the pressure caused by displacement, shaking, and slippage of the surrounding rock mass during the use of the weak surrounding rock tunnel, as well as the erosion damage to the support structure that affects the safe use of the weak surrounding rock tunnel.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A tunnel support structure, characterized in that the support structure comprises: Anchor mesh 1, including steel mesh, is laid along the surface of the surrounding rock of the tunnel; The initial lining 5 is laid along the tunnel axis and covers the anchor mesh 1; Arch frames 4 are laid at intervals along the tunnel axis and are set on the surface of the primary lining 5; the arch frames 4 are spliced ​​together from multiple arch frame segments set on the same radial section of the tunnel; each arch frame segment includes multiple evenly arranged asphalt steel pipe grid units; Anchor bolts are installed at intervals in the arch frame 4 and laid along the tunnel axis and the tunnel radial direction. The anchor bolts penetrate evenly into the surrounding rock of the tunnel through the primary lining 5 and the anchor mesh 1. The secondary lining 7 is laid along the tunnel axis and on the surface of the arch frame 4.

[0006] Preferably, the secondary lining 7 comprises: sprayed concrete with low rebound modulus formed by spraying, sprayed onto the surface of the arch frame 4.

[0007] Preferably, the arch segment includes: The upper rib steel pipe 4-2 includes a first arc-shaped steel pipe that is attached to the primary lining 5; the first arc-shaped steel pipe includes two first arc-shaped steel pipes arranged parallel to each other along the tunnel axis. The lower rib steel pipe 4-3 includes two second arc-shaped steel pipes arranged parallel to each of the first arc-shaped steel pipes along the radial direction of the tunnel; The upper rib steel pipe 4-2 and the lower rib steel pipe 4-3 are connected by the asphalt steel pipe grid unit.

[0008] Preferably, the asphalt steel pipe grating unit includes: U-shaped steel pipe 4-5, the closed end of which is attached to the first arc-shaped steel pipe; the two free ends of the U-shaped steel pipe 4-5 are connected to the same second arc-shaped steel pipe; Vertical connecting pipe 4-4 connects the first arc-shaped steel pipe and the second arc-shaped steel pipe located at the same cross section of the tunnel; the connecting pipe 4-4 includes a first vertical connecting pipe and a second vertical connecting pipe located on both sides of the U-shaped steel pipe 4-5; The transverse connecting pipe 4-9 includes a rod-shaped component; multiple transverse connecting pipes 4-9 are arranged along the tunnel axis, respectively connecting two first arc-shaped steel pipes and connecting two second arc-shaped steel pipes.

[0009] Preferably, a strain sensor 4-6 is provided on the first connecting pipe; and a spout 4-8 is provided on the second connecting pipe for injecting asphalt.

[0010] Preferably, a plurality of pressure relief holes 4-7 are provided on the upper rib steel pipe 4-2.

[0011] Preferably, the anchor bolt includes: anchor bolt 2, grouting anchor bolt 3, and locking anchor bolt 6.

[0012] Preferably, the anchor bolt 2 is set in the elastic zone of the tunnel surrounding rock; the grouting anchor bolt 3 is set in the plastic zone of the tunnel surrounding rock; and the locking anchor bolt 6 is fixed at the arch feet on both sides of the arch frame 4.

[0013] Preferably, the present invention also relates to a tunnel support construction method, wherein the improvement is that the construction method includes the following steps: Step S1: Construct arch frame 4; Step S2: After the tunnel excavation, the anchor mesh 1 is laid under the broken surrounding rock, and the primary lining 5 is formed by spraying concrete. The primary lining 5 covers the area of ​​the anchor mesh 1. Step S3: Install prefabricated arch frames 4 at intervals along the tunnel axis; Step S4: Drill holes at the intervals of the arch frame 4, and at the fixed positions on the arch side and arch top, and insert the anchor rods 2 and grouting anchor rods 3 into the holes; fix the arch frame 4 at the arch feet on both sides with locking anchor rods 6; Step S5: Monitor the strain value of the strain sensor; if the strain value of the strain sensor is less than the preset threshold, proceed to step S6. Step S6: Grout using grouting anchor bolts 3. After grouting, use shotcrete to form the secondary lining 7. Construction is complete.

[0014] Beneficial effects: The arch frame involved in this application comprises multiple evenly arranged asphalt-filled steel pipe grid units. Asphalt is filled into the grid units, ensuring that the steel pipes of the arch frame are uniformly filled with asphalt. When the surrounding rock deforms and exerts pressure, it compresses the arch frame, with the steel pipes and asphalt sharing the pressure. If the pressure is too high, the arch frame deforms, and the internal asphalt is squeezed out through the nozzle, achieving a pressure relief process. Once the pressure relief ends, i.e., when the strain value of the strain sensor is less than a preset threshold, grouting begins to repair the fractured surrounding rock and apply rigid support secondary lining to inhibit further deformation of the surrounding rock. Attached Figure Description

[0015] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Wherein: Figure 1 This is a schematic diagram of the support structure involved in the present invention; Figure 2 This is an elevation view of the arch frame involved in the present invention; Figure 3 This is a front view of the asphalt steel pipe grating unit involved in the present invention; Figure 4 This is a side view of the asphalt steel pipe grating unit involved in the present invention; Among them, 1. Anchor mesh, 2. Anchor bolt, 3. Grouting anchor bolt, 4. Arch frame, 5. Primary lining, 6. Locking foot anchor bolt, 7. Secondary lining, 4-1. Connecting steel plate, 4-2. Upper rib steel pipe, 4-3. Lower rib steel pipe, 4-4. Vertical connecting steel pipe, 4-5. U-shaped steel pipe, 4-6. Strain sensor, 4-7. Pressure relief hole, 4-8. Spout, 4-9. Horizontal connecting pipe, 4-10. Asphalt. Detailed Implementation

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0017] In the description of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. The terms "connected" and "linked" used in this invention should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; they can refer to a direct connection or an indirect connection through intermediate components. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0018] In the description of tunnel engineering, the term "axial" as used in this application refers to the direction of travel of a vehicle in a tunnel; the term "radial" refers to the direction perpendicular to the "axial" direction, and may also refer to the "circumferential" direction of the tunnel.

[0019] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0020] During tunnel construction, weak surrounding rock is frequently encountered. Soft rock generally refers to a type of severe geological condition characterized by weak lithology, susceptibility to rheological phenomena, significant deformation, and unfavorable conditions for the stability of support structures. The presence of weak surrounding rock poses a significant safety hazard to tunnel construction; improper or untimely handling can lead to catastrophic consequences. The instability and failure of soft rock tunnels are essentially due to the effect of ground pressure. The secondary stress redistributed after tunnel excavation interacts with the deformation and strength characteristics of the surrounding rock. When the secondary stress exceeds the plastic or strength limits of some surrounding rock or causes it to enter a significant rheological state, significant deformation, fracturing, loosening, and failure occur, exhibiting a clear ground pressure effect. Therefore, tunnel wall support is necessary.

[0021] Based on the above, it is clear that developing a tunnel support structure that is more suitable for soft rock tunnels, along with appropriate construction methods, is of great significance for ensuring the stability of soft rock tunnels with large deformations.

[0022] To overcome the shortcomings of the prior art, this invention aims to solve or improve at least one of the aforementioned technical problems by providing a novel tunnel support structure and its construction method. This structure is more suitable for soft rock tunnels with high ground stress, averaging 600m deep and reaching a maximum depth of 1200m, where the surrounding rock is primarily metamorphic sandstone. The tunnel support structure described in this application ensures that the surrounding rock mass on the outer surface of the soft rock tunnel remains stable, improving the overall structural integrity and stability of the tunnel. It also reduces the pressure caused by displacement, shaking, and slippage of the surrounding rock mass during tunnel use, as well as the erosion damage to the support structure that could affect the safe operation of the soft rock tunnel.

[0023] like Figure 1 As shown, the present invention relates to a tunnel support structure, wherein the improvement is that the support structure comprises: Anchor mesh 1, including steel mesh, is laid along the surface of the surrounding rock of the tunnel; specifically, anchor mesh 1 can be the steel mesh commonly used in existing engineering operations, laid along the tunnel axis and on the surface of the surrounding rock of the tunnel, which can also be understood as being laid on the surface of the fractured surrounding rock.

[0024] The initial lining 5 covers the anchor mesh 1; specifically, concrete is applied to the anchor mesh 1, and the initial lining is formed after the concrete has solidified.

[0025] The arch frame 4 is laid at intervals along the tunnel axis, with the interval distance set according to actual construction needs; the arch frame 4 is set on the surface of the primary lining 5; the arch frame 4 is spliced ​​together from multiple arch frame segments set on the same radial section of the tunnel; each arch frame segment includes multiple evenly arranged asphalt steel pipe grid units.

[0026] Specifically, the arch frame 4 is installed on the radial section of the tunnel and laid along the tunnel axis at intervals as required for construction. The arch frame 4 is laid on the surface of the primary lining 5. The arch frame 4 is composed of multiple arch frame segments spliced ​​together from the same radial section.

[0027] Preferably, the arch segment includes: The upper rib steel pipe 4-2 includes a first arc-shaped steel pipe that is attached to the primary lining 5; the first arc-shaped steel pipe includes two first arc-shaped steel pipes arranged parallel to each other along the tunnel axis. The lower rib steel pipe 4-3 includes two second arc-shaped steel pipes arranged parallel to each of the first arc-shaped steel pipes along the radial direction of the tunnel; The upper rib steel pipe 4-2 and the lower rib steel pipe 4-3 are connected by the asphalt steel pipe grid unit.

[0028] Specifically, such as Figure 2As shown, the arch frame 4 is assembled from multiple arch frame segments, with adjacent arch frame segments connected by connecting steel plates 4-1. Connecting steel plates 4-1 are provided on the cross-sections at both ends of each arch frame segment. When splicing multiple arch frame segments, simply attach the respective connecting steel plates 4-1 (i.e., two corresponding connecting steel plates 4-1) together and fix them with bolts or welding. The shape of each arch frame segment matches the surface of the tunnel surrounding rock, and at least six arch frame segments are used. Preferably, one arch frame segment is used at the connection between the invert arch (tunnel bottom) and the arch foot (two sides of the tunnel) to reduce stress concentration at the connection between the invert arch and the arch foot.

[0029] Specifically, the arch frame 4 includes upper rib steel pipes 4-2 and lower rib steel pipes 4-3. The upper rib steel pipes 4-2 are two arc-shaped steel pipes arranged parallel to the tunnel axis and attached to the primary lining 5; these are considered as two parallel first arc-shaped steel pipes. The lower rib steel pipes 4-3 are two second arc-shaped steel pipes, each corresponding to one of the first arc-shaped steel pipes along the tunnel radial direction. This can be understood as each second arc-shaped steel pipe being positioned inside the first arc-shaped steel pipe on the same radial section, parallel and concentrically arranged. The axis connecting the four arc-shaped steel pipes on the same section forms a rectangle, with both ends welded to the connecting steel plate 4-1.

[0030] Preferably, the asphalt steel pipe grating unit includes: U-shaped steel pipe 4-5, the closed end of which is attached to the first arc-shaped steel pipe; the two free ends of the U-shaped steel pipe 4-5 are connected to the same second arc-shaped steel pipe; Vertical connecting pipe 4-4 connects the first arc-shaped steel pipe and the second arc-shaped steel pipe located on the same radial section of the tunnel; the vertical connecting pipe 4-4 includes a first vertical connecting pipe and a second vertical connecting pipe located on both sides of the U-shaped steel pipe 4-5; The transverse connecting pipe 4-9 includes a rod-like structure; multiple transverse connecting pipes 4-9 are arranged along the tunnel axis; and two first arc-shaped steel pipes and two second arc-shaped steel pipes are connected.

[0031] Specifically, each arch segment includes multiple evenly arranged asphalt-coated steel pipe grating units. That is, multiple evenly arranged asphalt-coated steel pipe grating units are arranged between the upper rib steel pipe 4-2 and the lower rib steel pipe 4-3. Figure 3As shown, each asphalt steel pipe grating unit includes: vertical connecting steel pipes 4-4 and U-shaped steel pipes 4-5. The open end of the U-shaped steel pipe 4-5 faces downwards, and its two connecting ends connect to the second arc-shaped steel pipe. A U-shaped steel pipe 4-5 is installed on each of the second arc-shaped steel pipes. On both sides of each U-shaped steel pipe 4-5, a vertical connecting steel pipe 4-4 is installed, serving as the first and second vertical connecting pipes. Therefore, each asphalt steel pipe grating unit includes two U-shaped steel pipes 4-5 and four vertical connecting steel pipes 4-4. The vertical connecting steel pipes 4-4 connect the first and second arc-shaped steel pipes, and the length of the vertical connecting steel pipes 4-4 forms the distance between the first and second arc-shaped steel pipes. The height of the U-shaped steel pipe 4-5 must be the same as the length of the vertical connecting steel pipes 4-4. During surrounding rock deformation, the vertical steel pipes and U-shaped steel pipes share the pressure, with the U-shaped steel pipes being the main component for pressure relief during deformation. Therefore, attaching the apex of the U-shaped steel pipe 4-5 to the first arc-shaped steel pipe can make the structure of the arch frame 4 more stable and release more pressure.

[0032] The asphalt steel pipe grid unit also includes multiple transverse connecting pipes 4-9, positioned between two first arc-shaped steel pipes and two second arc-shaped steel pipes arranged parallel to each other along the tunnel axis, for connecting the two first arc-shaped steel pipes and the two second arc-shaped steel pipes. Specifically, the length of the transverse connecting pipes 4-9 can be considered as the width constituting the arch frame 4. The number of transverse connecting pipes 4-9 is not limited, as long as it serves to connect the two axially arranged first arc-shaped steel pipes and two second arc-shaped steel pipes. Preferably, to increase the connection strength of the arch frame section, such as... Figure 4 As shown, the transverse connecting pipes 4-9 can be respectively set at the connection points between each vertical connecting steel pipe 4-4 and the first arc-shaped steel pipe and the second arc-shaped steel pipe. Specifically, the asphalt steel pipe grating unit uses four transverse connecting pipes 4-9 to connect the four vertical connecting steel pipes 4-4 to the eight connection points between them and their corresponding first and second arc-shaped steel pipes. The interior of the transverse connecting pipes 4-9 can be hollow or solid. Hollow connecting pipes are preferred, so that when asphalt flows through the vertical connecting steel pipes 4-4, it will also flow into the transverse connecting pipes 4-9.

[0033] A strain sensor 4-6 is installed on each of the first connecting pipes; a spout 4-8 is installed on each of the second connecting pipes for pouring asphalt. Specifically, a spout 4-8 is welded to one of the vertical connecting steel pipes 4-4 on both sides of the U-shaped steel pipe 4-5, and the opening position of the spout 4-8 is offset from that of the first arc-shaped steel pipe for pouring asphalt; a strain sensor 4-6 is installed on the other vertical connecting steel pipe 4-4.

[0034] Multiple pressure relief holes 4-7 are provided on the upper rib steel pipe 4-2. Specifically, several pressure relief holes 4-7 are opened at the top of the first arc-shaped steel pipe to ensure that when multiple spouts 4-8 are simultaneously injecting asphalt 4-10, the air inside the steel pipe can be discharged through the pressure relief holes 4-7. The purpose of setting pressure relief holes 4-7 is because there is space between the steel pipes. After asphalt is injected, the air in the steel pipe will inevitably be compressed. If pressure relief holes 4-7 are not provided, the asphalt will not flow easily in the steel pipe under the action of air pressure, making it difficult to inject into the steel pipe.

[0035] In this application, the first arc-shaped steel pipe, the second arc-shaped steel pipe, the U-shaped steel pipe 4-5, and the vertical connecting steel pipe 4-4 are all hollow steel pipes. The vertical connecting steel pipe 4-4 must be connected to both the first and second arc-shaped steel pipes to ensure that the asphalt 4-10 can be evenly filled inside the steel pipes of the arch frame 4. The arch frame 4 filled with asphalt 4-10 can be considered an asphalt-steel pipe grating arch frame. Furthermore, the advantage of using asphalt as the filler for the arch frame 4 is that asphalt is an organic cementitious substance, which, depending on the temperature, exists in liquid, semi-solid, or solid states. It has good ductility, adhesion, and anti-corrosion properties, making it suitable as the filler for the arch frame 4 in this application.

[0036] The tunnel support structure involved in this invention also includes: Anchor bolts are installed at intervals between arch frames 4 and laid along the tunnel axis and radial direction; the anchor bolts pass through the primary lining 5 and the anchor mesh 1 and penetrate evenly into the surrounding rock of the tunnel. Specifically, the anchor bolts are installed at the intervals between the arch frames, and are laid simultaneously along the tunnel axis and the tunnel radial direction according to construction requirements. Preferably, the anchor bolts used in this application include: anchor bolt 2, grouting anchor bolt 3, and locking anchor bolt 6.

[0037] The anchor bolt 2 is set in the elastic zone of the tunnel surrounding rock; the grouting anchor bolt 3 is set in the plastic zone of the tunnel surrounding rock; and the locking anchor bolt 6 is fixed at the arch feet on both sides of the arch frame 4.

[0038] Specifically, such as Figure 1 As shown, anchor bolt 2 is longer, and its length must ensure that its anchoring end is located within the elastic zone of the surrounding rock to guarantee its reinforcement effect on the fractured surrounding rock. Grouting anchor bolt 3 is shorter than anchor bolt 2, and its length must ensure that its anchoring end is located within the plastic zone of the surrounding rock to ensure that the grout can fill the cracks in the surrounding rock during grouting, and to repair the fractured surrounding rock and improve its self-supporting capacity.

[0039] Anchor bolts 2 and grouting anchor bolts 3 are fixed within the primary lining. To facilitate subsequent grouting, grouting anchor bolts 3 must extend beyond the surrounding rock, with the extension length corresponding to the height of the arch frame 4. Locking anchor bolts 6 are fixed at the arch feet on both sides of the arch frame 4. Locking anchor bolts are groups of two bolts that intersect at their extended ends in the surrounding rock. At least two groups of locking anchor bolts are installed on each side of the arch frame 4, and one group of locking anchor bolts must be located at the connection between the invert and the arch foot.

[0040] Secondary lining 7 is laid on the surface of the arch frame 4; Preferably, the secondary lining 7 comprises: sprayed low-resilience-modulus shotcrete, sprayed onto the surface of the arch frame 4. Specifically, the secondary support includes a secondary lining 7, which is formed by spraying low-resilience-modulus shotcrete and is tightly adhered to the inner wall of the arch frame 4. This application also relates to a tunnel support construction method, characterized in that the construction method includes the following steps: Step S1: Prefabricate arch frame 4; Specifically, asphalt 4-10 flows from the inlet 4-8 into the first vertical connecting steel pipe. Under gravity, the asphalt 4-10 flows from one end of the first vertical connecting steel pipe into the lower rib steel pipe 4-3, gradually filling the entire U-shaped steel pipe along its shape. It then flows upwards along the second vertical connecting steel pipe into the upper rib steel pipe 4-2. When the asphalt fills to the horizontal position at the connection between the inlet and the vertical steel pipe, the filling speed is slow due to the small size of the inlet and the large space in the upper rib steel pipe 4-3, gradually filling the space. Simultaneously, asphalt flows through the vertical connecting steel pipe 4-4, it also flows into the transverse connecting pipe 4-9, which uses a hollow connecting pipe. After each asphalt steel pipe grid unit is filled with asphalt, the arch frame section is completed.

[0041] Step S2: After the tunnel excavation, the anchor mesh 1 is laid under the broken surrounding rock, and the primary lining 5 is formed by spraying concrete. The primary lining 5 covers the area of ​​the anchor mesh 1. Step S3: After the initial lining 5 is completed, the prefabricated arch frame 4 is erected; specifically, arch frame sections of the same location are erected at intervals along the tunnel axis according to the construction design requirements, and installed in batches according to the number of arch frame sections. Step S4: After the arch frame 4 is constructed, holes are drilled at the intervals between arch frames and at fixed positions on the arch side and arch top. Anchor rods 2 and grouting anchor rods 3 are inserted into the holes. Anchor rods 2 and grouting anchor rods 3 are fixed within the primary lining. To facilitate subsequent grouting, grouting anchor rods 3 need to extend beyond the surrounding rock, with the extension length corresponding to the height of arch frame 4. Locking anchor rods 6 are used to fix the arch frame 4 at both arch feet. Specifically, locking anchor rods 6 use bearing plates and are secured to the arch frame with bolts. At least two sets of locking anchor rods are installed on each side of arch frame 4, and one set of locking anchor rods must be installed at the connection between the invert and the arch foot.

[0042] Step S5: Monitor the strain value of the strain sensor; specifically, after the arch frame 4 is successfully installed, if the pressure is too high, the arch frame 4 will deform, and the asphalt inside will be squeezed out through the nozzle, achieving the pressure relief process. Asphalt is injected into the arch frame 4 at a high temperature, at which point the asphalt is in a liquid state. The steel arch frame is erected after the asphalt solidifies. After solidification, the asphalt is solid and can share the pressure with the steel pipe; however, asphalt has good ductility in its solid state, and if the deformation of the arch frame 4 is too large, the asphalt will be squeezed out through the nozzle.

[0043] When the pressure release ends, i.e., when the strain sensor placed on arch frame 4 detects a strain value less than the preset strain threshold on a certain day, it indicates that the pressure on arch frame 4 is too high, and secondary lining construction of the tunnel surrounding rock is required. The timing of secondary lining construction needs to be considered. After the tunnel is excavated, the free face of the tunnel surrounding rock is approximately under biaxial stress, resulting in significant deformation. Secondary lining is a rigid support and cannot tolerate large deformations. Therefore, the surrounding rock must first be deformed to relieve some of the pressure on arch frame 4 before applying secondary lining; otherwise, the secondary lining is easily damaged and cannot achieve its supporting function.

[0044] Step S6: Grouting is performed using grouting anchors 3. After grouting is completed, secondary lining 7 is formed using shotcrete, and construction is completed.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention shall be within the scope of protection of the pending claims of the present invention.

Claims

1. A tunnel support structure, characterized in that, The support structure includes: Anchor mesh (1), including steel mesh, is laid along the surface of the surrounding rock of the tunnel; The initial lining (5) is laid along the tunnel axis and covered with the anchor mesh (1). Arch frames (4) are laid at intervals along the tunnel axis and set on the surface of the primary lining (5); the arch frames (4) are spliced ​​together from multiple arch frame segments set on the same radial section of the tunnel; each arch frame segment includes multiple uniformly arranged asphalt steel pipe grid units; Anchor bolts are installed at intervals in the arch frame (4) and laid along the tunnel axis and the tunnel radial direction; the anchor bolts penetrate the primary lining (5) and the anchor mesh (1) and extend evenly into the surrounding rock of the tunnel; Secondary lining (7) is laid along the tunnel axis and laid on the surface of the arch frame (4); The arch frame section includes: The upper rib steel pipe (4-2) includes a first arc-shaped steel pipe that is attached to the primary lining (5); the first arc-shaped steel pipe includes two first arc-shaped steel pipes arranged parallel to each other along the tunnel axis; The lower rib steel pipe (4-3) includes two second arc-shaped steel pipes arranged parallel to each of the first arc-shaped steel pipes along the radial direction of the tunnel; The upper rib steel pipe (4-2) and the lower rib steel pipe (4-3) are connected by the asphalt steel pipe grid unit; The asphalt steel pipe grating unit includes: U-shaped steel pipe (4-5), one closed end of which is attached to the first arc-shaped steel pipe; the two free ends of the U-shaped steel pipe (4-5) are connected to the same second arc-shaped steel pipe; A vertical connecting pipe (4-4) connects the first arc-shaped steel pipe and the second arc-shaped steel pipe located at the same cross section of the tunnel; the connecting pipe (4-4) includes a first vertical connecting pipe and a second vertical connecting pipe located on both sides of the U-shaped steel pipe (4-5); The transverse connecting pipe (4-9) includes a rod-shaped member; multiple transverse connecting pipes (4-9) are arranged along the tunnel axis, respectively connecting two first arc-shaped steel pipes and connecting two second arc-shaped steel pipes; A strain sensor (4-6) is installed on the first vertical connecting pipe; a spout (4-8) is installed on the second vertical connecting pipe for injecting asphalt.

2. The tunnel support structure as described in claim 1, characterized in that, The secondary lining (7) includes: sprayed low-resilience-modulus shotcrete, which is sprayed onto the surface of the arch frame (4).

3. The tunnel support structure as described in claim 1, characterized in that, Multiple pressure relief holes (4-7) are provided on the upper rib steel pipe (4-2).

4. The tunnel support structure as described in claim 1, characterized in that, The anchor bolts include: anchor bolt (2), grouting anchor bolt (3), and locking anchor bolt (6).

5. The tunnel support structure as described in claim 4, characterized in that, The anchor rod (2) is set in the elastic zone of the surrounding rock of the tunnel; the grouting anchor rod (3) is set in the plastic zone of the surrounding rock of the tunnel; the locking anchor rod (6) is fixed at the arch feet on both sides of the arch frame (4).

6. A tunnel support construction method for a tunnel support structure as described in any one of claims 1-5, characterized in that, The construction method includes the following steps: Step S1: Construct the arch frame (4); Step S2: After the tunnel excavation, the anchor mesh (1) is laid under the broken surrounding rock, and the primary lining (5) is formed by spraying concrete. The primary lining (5) covers the area of ​​the anchor mesh (1). Step S3: Install the prefabricated arch frame (4) at intervals along the tunnel axis; Step S4: Drill holes at the intervals of the arch frame (4) and at the fixed positions on the arch side and arch top, and insert the anchor rod (2) and the grouting anchor rod (3) into the holes; fix the arch frame (4) at the arch feet on both sides with locking anchor rods (6); Step S5: Monitor the strain value of the strain sensor (4-6); if the strain value of the strain sensor (4-6) is less than a preset threshold, proceed to step S6; Step S6: Grouting is performed using grouting anchors (3). After grouting is completed, the secondary lining (7) is formed using shotcrete, and the construction is completed.

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