Variable angle self-locking enhanced tunnel type anchorage structure and construction method

Abstract

The application belongs to the technical field of bridge engineering, and discloses a variable-angle self-locking reinforced tunnel type anchorage structure and a construction method, which comprises an anchor plug channel arranged in the mountain surrounding rock and a concrete anchor plug arranged in the anchor plug channel; the concrete anchor plug is divided into at least two sections along the longitudinal axis of the anchor plug channel, and comprises a first anchor plug section close to the direction of the hole and a second anchor plug section away from the direction of the hole; the first anchor plug section and the second anchor plug section are both wedge-shaped bodies, the cross-sectional size of the side surface of the first anchor plug section and the second anchor plug section is linearly increased according to a fixed expansion angle, the expansion angle of the first anchor plug section is a first expansion angle β1, the expansion angle of the second anchor plug section is a second expansion angle β2, the first expansion angle β1 is smaller than the second expansion angle β2, and the concrete anchor plug is a variable-angle wedge-shaped structure. The application has the technical effects of maintaining the stability of the hole surrounding rock, reducing the supporting difficulty and construction risk, and improving the ultimate uplift bearing capacity of the anchorage.

Description

Technical Field

[0001] This invention belongs to the field of bridge engineering technology, specifically relating to a variable-angle self-locking reinforced tunnel anchorage structure and its construction method. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Tunnel-type anchorages for suspension bridges are a type of anchorage that utilizes natural rock masses to bear the enormous tension of the main cable. By having the anchorage and the surrounding rock share the tension of the cable, the amount of excavation and concrete used can be reduced. This also means that the bearing capacity of tunnel-type anchorages is closely related to the strength of the rock mass.

[0004] To address the aforementioned technical issues, existing technology discloses a tunnel-type anchorage for suspension bridges, comprising a front anchorage chamber, an anchor plug, a rear anchorage chamber, and a cable saddle. The bottom of the anchor plug adopts a toothed variable cross-section to increase the lateral friction resistance between the anchorage structure and the surrounding rock. The rear anchorage chamber is constructed at the tail end of the anchorage beam. The anchorage beam is anchored to the rock mass through precast pipe piles with frustum-shaped roots and cylindrical pile bodies on both sides. The left and right anchor plugs are connected into a whole through the anchorage beam and the transverse precast pipe piles, increasing the overall integrity of the left and right anchorages.

[0005] Although the above scheme increases the load-bearing capacity of the anchorage structure, it still has the following drawbacks: The tunnel-type anchorage in the above scheme is shaped like a city gate. From the front anchorage to the rear anchorage, the top cross-sectional dimensions of the tunnel-type anchorage increase linearly with a fixed expansion angle. In actual engineering, if the expansion angle of the tunnel-type anchorage is too small, the amount of excavation work can be reduced. However, under the same tensile force, the normal compressive stress generated by the anchor plug on the surrounding rock is relatively small. According to the Mohr-Coulomb criterion, the improvement of the interface shear strength is limited, which is not conducive to the "wedge self-locking" effect. If the expansion angle of the tunnel-type anchorage is too large, the normal stress and pull-out bearing capacity can be increased. However, this will lead to an excessively large excavation cross-section at the front end of the anchor plug (the tunnel entrance section). This will not only increase the project cost but also easily cause the surrounding rock in the tunnel entrance section to loosen and collapse, affecting construction safety. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a variable-angle self-locking reinforced tunnel anchor structure and construction method, which can solve the technical problems in the prior art where the small extension angle of the tunnel anchor results in limited improvement of the interface shear strength, while the large extension angle results in a large excavation cross section and high engineering cost.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In the first aspect, a variable-angle self-locking reinforced tunnel anchorage structure is provided, including an anchor plug channel opened in the surrounding rock of the mountain, and a concrete anchor plug poured in the anchor plug channel; The concrete anchor plug is divided into at least two segments along the longitudinal axis of the anchor plug channel, including a first anchor plug segment near the opening and a second anchor plug segment away from the opening; both the first and second anchor plug segments are wedge-shaped, and the cross-sectional dimensions of the sides of the first and second anchor plug segments increase linearly with a fixed expansion angle. The expansion angle of the first anchor plug segment is the first expansion angle β1, and the expansion angle of the second anchor plug segment is the second expansion angle β2, and the first expansion angle β1 is less than the second expansion angle β2. The concrete anchor plug is a variable angle wedge structure.

[0008] Preferably, the front end face of the first anchor plug section is the front anchor face, and the front anchor face is cast integrally with the rear end of the front anchor chamber; the rear anchor face of the second anchor plug section is the rear anchor face, and the cross-sectional area of ​​the rear anchor face is larger than that of the front anchor face.

[0009] Preferably, the front end of the concrete anchor plug is fixedly connected to the front anchor chamber, and a cable saddle is provided in the front anchor chamber. The main cable strand passes through the front anchor chamber and is dispersed into multiple anchor cables. The multiple anchor cables pass through the concrete anchor plug and are anchored to the rear of the concrete anchor plug.

[0010] Preferably, the concrete anchor plug is equipped with a steel reinforcement skeleton, and the tail ends of multiple anchor cables of the main cable strand are fixed to the steel reinforcement skeleton or the rear anchor surface through an anchoring system.

[0011] Preferably, the first anchor segment and the second anchor segment are connected by a smooth transition section or a stepped surface to avoid stress concentration.

[0012] Preferably, the inner wall surface of the anchor plug channel is a rough surface, and a number of anti-shear grooves are provided on the inner wall surface of the anchor plug channel. The anti-shear grooves are arranged circumferentially along the anchor plug channel to enhance the anti-shear friction of the contact surface.

[0013] Preferably, the first extension angle β1 ranges from 2° to 5° and is used to control the excavation disturbance of the surrounding rock at the tunnel entrance; the second extension angle β2 is greater than the first extension angle β1, ranges from 5° to 15°, and is less than the value calculated by the following formula: ; in, The initial stress of the surrounding rock, For the cohesion of the surrounding rock, The angle of friction of the surrounding rock. It represents the uniaxial saturated compressive strength of the surrounding rock.

[0014] Secondly, a construction method for the aforementioned variable-angle self-locking reinforced tunnel anchorage structure is provided, the specific steps of which include: S1. Excavate the anchor plug channel according to the design requirements, and excavate along the longitudinal axis of the anchor plug channel to form a first channel with a first expansion angle β1 and a second channel with a second expansion angle β2. S2. Treat the inner wall surface of the excavated anchor plug channel; S3. Install the steel reinforcement cage, main cable strands and anchoring system for the concrete anchor plug; S4. The second channel and the first channel are poured in sections from the inside out to form the second anchor plug section and the first anchor plug section, forming a concrete anchor plug body with a variable angle wedge structure.

[0015] Preferably, the anchor plug channel also includes a front anchor chamber section at the front end of the first channel section, and the front anchor chamber is cast after the first anchor plug section is cast.

[0016] Preferably, several shear grooves are made on the inner wall of the excavated anchor plug channel, and the shear grooves are arranged circumferentially along the anchor plug channel.

[0017] Compared with the prior art, the advantages and positive effects of this invention are: This invention reduces the excavation span of the anchor block channel by setting a first anchor block section with a smaller expansion angle at the tunnel entrance (shallow buried section), thus maintaining the stability of the surrounding rock at the tunnel entrance and reducing the difficulty of support and construction risks. A second anchor block section with a larger expansion angle is set in the deeper surrounding rock, taking advantage of the good quality and high ground stress of the deep surrounding rock, combined with the strong wedge effect brought by the large angle, thus improving the ultimate pull-out bearing capacity of the anchor. Compared with a scheme using a large expansion angle throughout the entire length, this invention reduces the amount of ineffective concrete filling and earthwork excavation; compared with a scheme using a small expansion angle throughout the entire length, it shortens the required anchorage length of the anchor block. Attached Figure Description

[0018] The accompanying drawings, which form part of this invention, 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 improper limitation of the invention.

[0019] Figure 1 This is a structural schematic diagram of a variable-angle self-locking reinforced tunnel anchorage structure according to Embodiment 1 or Embodiment 2 of the present invention; In the picture: 1. Surrounding rock; 2. Concrete anchor plug body; 21. First anchor plug section; 22. Second anchor plug section; 3. Main cable strand; 4. Front anchor face; 5. Rear anchor face; 6. Anchoring system. Detailed Implementation

[0020] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0021] The present invention will now be described in detail with reference to the accompanying drawings.

[0022] Example 1 This embodiment discloses a variable-angle self-locking reinforced tunnel anchorage structure, such as Figure 1 As shown, the structure includes an anchor plug channel carved into the surrounding rock 1 of the mountain, and a concrete anchor plug 2 poured into the anchor plug channel. The concrete anchor plug 2 is divided into at least two segments along the longitudinal axis of the anchor plug channel, including a first anchor plug segment 21 near the opening and a second anchor plug segment 22 away from the opening. In this embodiment, both the first anchor plug segment 21 and the second anchor plug segment 22 are wedge-shaped. The cross-sectional dimensions of the sides of both the first anchor plug segment 21 and the second anchor plug segment 22 increase linearly with a fixed expansion angle. The expansion angle of the first anchor plug segment 21 is the first expansion angle β1, and the expansion angle of the second anchor plug segment is the second expansion angle β2. The first expansion angle β1 is smaller than the second expansion angle β2, forming a multi-level wedge structure that gradually expands towards the deeper surrounding rock along the axis of the anchor plug channel. That is, the concrete anchor plug 2 is a variable-angle wedge structure.

[0023] It needs to be explained that the anchor plug channel refers to the space excavated within the surrounding rock 1 to accommodate the concrete anchor plug 2. The concrete anchor plug 2 refers to the concrete entity poured into the anchor plug channel, which is the core load-bearing component of the anchor structure, responsible for transmitting the tension of the main cable to the surrounding rock 1. The spread angle refers to the angle between the side of the wedge and the axis.

[0024] It should be noted that during excavation, the surrounding rock at the tunnel entrance is usually more prone to fracturing and instability, while the internal surrounding rock is relatively more solid. The core reason is related to the stress state of the surrounding rock. The internal surrounding rock is in a state of "triaxial stress equilibrium," with uniform stress and strong stability. However, the rock mass at the tunnel entrance is a "slope / free-falling rock mass," subject only to bidirectional or unidirectional constraints, resulting in significant stress concentration. After excavation, it loses its original support and is prone to loosening and fracturing. If a smaller spread angle is chosen to control the disturbance during tunnel entrance excavation, the high strength characteristics of the deep surrounding rock cannot be effectively utilized, leading to insufficient overall bearing capacity of the anchorage. If a larger spread angle is chosen to enhance the deep bearing capacity, the excavation span of the tunnel entrance section increases significantly, causing the surrounding rock to loosen and requiring additional support measures, thus increasing the construction difficulty and risk.

[0025] Understandably, in this embodiment, the concrete anchor plug 2 is designed as two sections. A first anchor plug section 21 with a smaller expansion angle is used at the tunnel entrance, which reduces the excavation span, helps maintain the stability of the surrounding rock at the tunnel entrance, and reduces support difficulty and construction risk. A second anchor plug section 22 with a larger expansion angle is set deep within the surrounding rock 1. When the concrete anchor plug 2 tends to pull outwards, the second anchor plug section 22 with the larger expansion angle is tightly "locked" in the deep surrounding rock, and the constraint force of the deep surrounding rock on the concrete anchor plug 2 increases sharply, forcing shear... The failure surface not only occurs at the contact surface, but may also force the shear surface to penetrate deep into the surrounding rock, calling on a larger range of rock mass to participate in pull-out resistance and improving the ultimate pull-out bearing capacity of the concrete anchor plug 2. In this embodiment, by setting anchor plug sections with different expansion angles along the axial direction of the anchor plug channel, an optimized stress mode of "small angle entry and large angle locking" is achieved. Compared with the scheme of using a large expansion angle for the whole length, the amount of ineffective concrete filling and earthwork excavation can be reduced. Compared with the scheme of small expansion angle for the whole length, the required anchoring length of the anchor plug can be shortened.

[0026] It is also understandable that when the tension of the main cable is transmitted to the concrete anchor plug 2, the compression effect of the first anchor plug segment on the surrounding rock is relatively small due to its smaller spread angle, thus avoiding excessive stress concentration in the tunnel section with poor surrounding rock conditions. Subsequently, the tension is further transmitted to the second anchor plug segment at a deeper depth. The second anchor plug segment, with its larger spread angle, generates a strong wedge-shaped self-locking effect in the deep surrounding rock and high ground stress environment, efficiently converting the tension into normal compressive stress and tangential shear stress on the surrounding rock, thereby achieving reliable anchoring of the main cable tension. The excavation of the anchor plug channel can be carried out using conventional drill-and-blast methods or mechanical tunneling. The pouring of the concrete anchor plug can be achieved through traditional construction techniques such as on-site formwork and segmented pouring.

[0027] like Figure 1 As shown, the front end face of the first anchor plug section 21 is the front anchor face 4, and the front anchor face 4 is cast integrally with the rear end of the front anchor chamber; the rear anchor face of the second anchor plug section 22 is the rear anchor face 5, and the cross-sectional area of ​​the rear anchor face 5 is larger than the cross-sectional area of ​​the front anchor face 4.

[0028] In this embodiment, the front end face of the first anchor plug section 21 is the front anchor face 4, whose main function is to serve as the initial interface for the anchor structure to receive the tension of the main cable. The front anchor face and the rear end of the front anchor chamber are cast as one piece. This integrated casting structural design aims to achieve structural continuity and mechanical integrity between the front anchor face and the rear end of the front anchor chamber.

[0029] The rear anchor face 5 of the second anchor plug section 22 serves as the end interface for deep anchoring of the concrete anchor plug body and is the anchoring interface at the tail end of the main cable strand. Anchoring holes or anchor plates can be pre-drilled on the rear anchor face 5 to fix the anchor cable. The cross-sectional area of ​​the rear anchor face is larger than that of the front anchor face, reflecting the wedge-shaped structure trend of the concrete anchor plug body 2 gradually increasing from the opening to the depth. The larger cross-sectional area of ​​the rear anchor face helps to provide a larger bearing area for the concrete anchor plug body 2.

[0030] like Figure 1 As shown, the front end of the concrete anchor plug 2 is fixedly connected to the front anchor chamber. A cable saddle is installed in the front anchor chamber. The main cable strand 3 passes through the front anchor chamber and is dispersed into multiple anchor cables by the cable saddle. The multiple anchor cables pass through the concrete anchor plug and are anchored to the rear anchor surface 5 of the concrete anchor plug 2.

[0031] Understandably, the concrete anchor plug 2 is the core load-bearing component of the anchorage structure. Its variable-angle wedge structure forms a self-locking effect with the surrounding rock 1 to resist the tension of the main cable. The front end of the concrete anchor plug 2 is fixedly connected to the front anchor chamber, ensuring that the front anchor chamber and the concrete anchor plug form a structural whole, thereby reliably transmitting the tension of the main cable. The function of the front anchor chamber is to provide a transition and dispersion area for the main cable strands 3 as they enter the concrete anchor plug 2. To effectively disperse the tension of the main cable, a cable saddle is installed in the front anchor chamber. The cable saddle is a device specifically designed to disperse the main cable strands from a concentrated, unified state into multiple independent anchor cables, thereby evenly distributing the enormous tension of the main cable, avoiding stress concentration, and facilitating subsequent anchoring.

[0032] In this embodiment, a steel reinforcement skeleton is provided inside the concrete anchor plug 2, and the tail ends of multiple anchor cables of the main cable strand 3 are fixed to the steel reinforcement skeleton or the rear anchor surface through the anchoring system 6; the anchoring system 6 transmits the tension of the main cable to the concrete anchor plug 2, and converts it into normal compressive stress and tangential shear stress on the surrounding rock 1 through the variable angle wedge structure.

[0033] Understandably, the steel reinforcement cage refers to the internal support structure made of steel bars, which is used to enhance the tensile, shear and bending resistance of the concrete anchor body, ensuring that the concrete can maintain structural integrity when subjected to the huge tensile force of the main cable, and avoiding cracking or damage caused by local stress concentration.

[0034] The anchoring system 6 is a device specifically designed to transfer the tension of the main cable strands to the concrete anchor plug. It typically includes anchors and anchor plates, and its main function is to distribute and transfer the tension of the anchor cable to the concrete anchor plug 2. The anchoring system can fix the tail end of the anchor cable to the reinforcing steel frame, for example, by welding or bolting the anchor plate to the reinforcing steel frame; or it can be directly embedded in the rear anchor surface of the concrete anchor plug.

[0035] It is important to note that in this embodiment, the first anchor segment 21 and the second anchor segment 22 are connected by a smooth transition section or a stepped surface to avoid stress concentration. A smooth transition section refers to the area connecting two structures with different geometries or sizes via a curved or conical surface. Its function is to mitigate the abrupt change in the cross-sectional dimensions between the first anchor segment 21 and the second anchor segment 22, resulting in a more uniform stress distribution and reducing localized stress concentration. A stepped surface refers to the area connecting two structures via multiple or a single step-like cross-sectional change. Compared to a smooth transition section, which is more difficult to control during construction, a stepped surface, while exhibiting abrupt cross-sectional changes, is easier to construct. By changing the number, height, and width of the steps, stress distribution can be effectively controlled, preventing excessive stress concentration at a single cross-section. This allows the entire variable-angle wedge structure to function as a whole, stably converting tensile force into normal compressive stress and tangential shear stress on the surrounding rock, fully utilizing the bearing potential of the deep surrounding rock.

[0036] In this embodiment, the inner wall surface of the anchor plug channel is a rough surface, and the concrete anchor plug and the inner wall surface form an anchor rock contact surface. Furthermore, a number of shear-resistant grooves are provided on the inner wall surface of the anchor plug channel. The shear-resistant grooves are arranged circumferentially along the anchor plug channel to enhance the shear friction resistance of the anchor rock contact surface between the inner wall surface and the concrete anchor plug.

[0037] Understandably, the inner wall of the anchor plug channel is designed to be roughened. After excavation, the inner wall can be manually roughened to increase its surface roughness. Shear grooves are structures created on the inner wall of the anchor plug channel to enhance the shear resistance of the interface. After excavation, circumferential grooves can be formed on the inner wall of the anchor plug channel using mechanical milling or rock drilling equipment. During the pouring of the concrete anchor plug 2, the concrete forms shear keys within the shear grooves, allowing the concrete anchor plug 2 to directly and mechanically engage with the anchor plug channel, thus enhancing the shear bearing capacity of the interface between the concrete anchor plug 2 and the surrounding rock. In this embodiment, the cross-sectional shape of the shear grooves is designed as trapezoidal to increase the embedding effect after concrete pouring.

[0038] It should be noted that in this embodiment, the first extension angle β1 ranges from 2° to 5° and is used to control the excavation disturbance of the surrounding rock at the tunnel entrance; the second extension angle β2 is greater than the first extension angle β1, ranges from 5° to 15°, and is less than the value calculated by the following formula: ; in, The initial stress of the surrounding rock, For the cohesion of the surrounding rock, The angle of friction of the surrounding rock. It represents the uniaxial saturated compressive strength of the surrounding rock.

[0039] Understandably, using a smaller first extension angle β1 helps reduce excavation volume and disturbance to the surrounding rock at the tunnel entrance, thereby maintaining its stability and reducing support difficulty and construction risks. Using a larger second extension angle β2 allows for the utilization of favorable geological conditions and high ground stress in the deep surrounding rock, enhancing the ultimate pull-out bearing capacity of the anchorage through a large-angle wedge effect. In this embodiment, the upper limit of the second extension angle β2 is not a fixed value, but rather depends on the initial stress of the surrounding rock. Cohesion of surrounding rock The angle of friction of the surrounding rock Uniaxial saturated compressive strength of surrounding rock Relatedly, after conducting geological surveys to obtain data on the deep surrounding rock before construction, the maximum allowable value of the second extension angle β2 is calculated to avoid the collapse of the deep surrounding rock due to an excessively large second extension angle β2. This ensures that the second anchor plug section 22 can make full use of the good properties of the surrounding rock, so that the anchor structure can achieve a balance between the bearing capacity and the stability of the surrounding rock as a whole.

[0040] Example 2 This embodiment discloses a construction method for a variable-angle self-locking reinforced tunnel anchorage structure according to Embodiment 1. The specific steps include: S1. According to the design requirements, excavate the anchor plug channel in the surrounding rock 1, and excavate along the longitudinal axis of the anchor plug channel to form a first channel with a first expansion angle β1 and a second channel with a second expansion angle β2. S2. The inner wall surface of the excavated anchor plug channel is treated (roughened). S3, steel reinforcement cage for installing concrete anchor plug 2, main cable strand 3 and anchoring system 6; S4. The second channel and the first channel are poured in sections from the inside out to form the second anchor plug section 22 and the first anchor plug section 21, forming a concrete anchor plug body 2 with a variable angle wedge structure.

[0041] Step S1 involves forming the geometry of the anchor plug channel within the surrounding rock 1 according to the pre-designed variable-angle wedge structure, which forms the basis for the anchorage structure construction. Step S2 involves improving the physical properties of the inner wall of the anchor plug channel to enhance the bonding force between the concrete anchor plug and the surrounding rock, thereby improving the overall stability of the anchorage structure. Step S3 involves placing the core load-bearing components and force transmission system of the anchorage structure in place, and connecting and fixing the tail ends of multiple anchor cables of the main cable strand 3 to the steel reinforcement frame or rear anchor face through the anchoring system 6. Step S4 is crucial for forming the concrete anchor plug structure. By using a segmented, inside-out pouring sequence, the construction quality of the concrete can be effectively controlled, shrinkage cracks can be reduced, and the precise forming of the variable-angle wedge structure can be ensured.

[0042] It is understandable that the anchor plug channel also includes the front anchor chamber section at the front end of the first channel. The front anchor chamber is formed after the first anchor plug section 21 is cast in the first channel. A cable saddle is installed in the front anchor chamber, and multiple anchor cables are fixedly connected to the main cable strands on the cable saddle.

[0043] In this embodiment, in step S2, after roughening the inner wall surface of the excavated anchor plug channel, several anti-shear grooves are opened on the inner wall surface of the excavated anchor plug channel, and the anti-shear grooves are arranged circumferentially along the anchor plug channel.

[0044] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A variable-angle self-locking reinforced tunnel anchorage structure, characterized in that, This includes anchor plug channels opened within the surrounding rock of the mountain, and concrete anchor plugs poured into the anchor plug channels; The concrete anchor plug is divided into at least two segments along the longitudinal axis of the anchor plug channel, including a first anchor plug segment near the opening and a second anchor plug segment away from the opening; both the first and second anchor plug segments are wedge-shaped, and the cross-sectional dimensions of the sides of the first and second anchor plug segments increase linearly with a fixed expansion angle. The expansion angle of the first anchor plug segment is the first expansion angle β1, and the expansion angle of the second anchor plug segment is the second expansion angle β2, and the first expansion angle β1 is less than the second expansion angle β2. The concrete anchor plug is a variable angle wedge structure.

2. The variable-angle self-locking reinforced tunnel anchorage structure as described in claim 1, characterized in that, The front end face of the first anchor plug section is the front anchor face, which is cast integrally with the rear end of the front anchor chamber; the rear anchor face of the second anchor plug section is the rear anchor face, and the cross-sectional area of ​​the rear anchor face is larger than that of the front anchor face.

3. The variable-angle self-locking reinforced tunnel anchorage structure as described in claim 1, characterized in that, The front end of the concrete anchor plug is fixedly connected to the front anchor chamber. A cable saddle is installed in the front anchor chamber. The main cable strand passes through the front anchor chamber and is dispersed into multiple anchor cables. The multiple anchor cables pass through the concrete anchor plug and are anchored to the rear of the concrete anchor plug.

4. The variable-angle self-locking reinforced tunnel anchorage structure as described in claim 3, characterized in that, The concrete anchor plug is equipped with a steel reinforcement skeleton, and the tail ends of multiple anchor cables of the main cable strand are fixed to the steel reinforcement skeleton or the rear anchor surface through an anchoring system.

5. The variable-angle self-locking reinforced tunnel anchorage structure as described in claim 1, characterized in that, The first and second anchor segments are connected by a smooth transition section or stepped surface to avoid stress concentration.

6. The variable-angle self-locking reinforced tunnel anchorage structure as described in claim 1, characterized in that, The inner wall surface of the anchor plug channel is rough, and several anti-shear grooves are provided on the inner wall surface of the anchor plug channel. The anti-shear grooves are arranged circumferentially along the anchor plug channel to enhance the anti-shear friction of the contact surface.

7. The variable-angle self-locking reinforced tunnel anchorage structure as described in claim 1, characterized in that, The first extension angle β1 ranges from 2° to 5° and is used to control the excavation disturbance of the surrounding rock at the tunnel entrance. The second extension angle β2 is greater than the first extension angle β1, ranges from 5° to 15°, and is less than the value calculated by the following formula: ； in, The initial stress of the surrounding rock, For the cohesion of the surrounding rock, The angle of friction of the surrounding rock. It represents the uniaxial saturated compressive strength of the surrounding rock.

8. A construction method for a variable-angle self-locking reinforced tunnel anchorage structure as described in any one of claims 1-7, characterized in that, The specific steps include: S1. Excavate the anchor plug channel according to the design requirements, and excavate along the longitudinal axis of the anchor plug channel to form a first channel with a first expansion angle β1 and a second channel with a second expansion angle β2. S2. Treat the inner wall surface of the excavated anchor plug channel; S3. Install the steel reinforcement cage, main cable strands, and anchoring system of the concrete anchor plug; S4. The second channel and the first channel are poured in sections from the inside out to form the second anchor plug section and the first anchor plug section, forming a concrete anchor plug body with a variable angle wedge structure.

9. The construction method of a variable-angle self-locking reinforced tunnel anchorage structure as described in claim 8, characterized in that, The anchor plug channel also includes a front anchor chamber section at the front end of the first channel section, and the front anchor chamber is cast after the first anchor plug section is cast.

10. The construction method of a variable-angle self-locking reinforced tunnel anchorage structure as described in claim 8, characterized in that, Several shear grooves are made on the inner wall of the excavated anchor plug channel, and the shear grooves are arranged circumferentially along the anchor plug channel.

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