Tunnel face advanced prestressed anchor and construction method

Abstract

The present invention relates to an advanced prestressed anchor rod for a tunnel face and a construction method, comprising an anchor rod body, wherein the anchor rod body is formed by connecting a plurality of rod-shaped components in sequence, and adjacent rod-shaped components are connected via connecting screw sleeves. The bottom of the anchor rod body is bonded to the surrounding rock of the anchor hole via an anchoring agent, and the portion of the top of the rod body exposed to the surrounding rock is provided with an anchor rod tray, and a fastening nut matched with the thread of the anchor rod body is provided on the outside of the anchor rod tray. The anchor rod tray is locked on the surrounding rock of the anchor hole via the fastening nut. The anchor rod can apply a large prestress, and can quickly and effectively provide support resistance at the initial stage of deformation of the surrounding rock of the face. At the same time, as the tunnel face is excavated, the anchor rod body components can be synchronously disassembled, and can fully ensure the supporting effect of the face anchor rod while meeting the needs of tunnel excavation and increasing the reusability of the face anchor rod.

Description

Technical Field

[0001] The invention relates to a tunnel face advanced prestressed anchor rod and a construction method. Background Art

[0002] Tunnels with weak surrounding rocks have low self-bearing capacity and large potential deformation energy. In the early stage of tunnel excavation, the surrounding rock stress is released in large quantities and the deformation rate is fast. Usually, the support structures used in tunnels are mostly passive support. When the surrounding rock deformation increases to a certain extent, they can provide support resistance. Moreover, the support reaction force provided by the support structure increases with the continuous increase of surrounding rock deformation, which is very unfavorable for preventing weak surrounding rocks from entering a relaxed state. Therefore, it is very necessary for the support structure to quickly provide a large support reaction force in the early stage of tunnel deformation.

[0003] The stability of the tunnel face is the premise of safe construction. The face of a hard rock tunnel can be short-term stable after excavation, while a soft rock tunnel requires certain human intervention to achieve a short-term stable state. The instability of the face may be manifested as local loosening and falling of the face surrounding rock, or instability leading to the collapse of the vault. In order to maintain the stability of the face, one of the main support measures for reinforcing the face is to use anchor rods for reinforcement. Prestressed anchor rods can provide a large active support resistance at the initial deformation stage after the face is excavated, which can effectively prevent the face surrounding rock from quickly entering a relaxed state and ensure the short-term stability of the face. The material of the face anchor rod is mainly steel and fiberglass. Steel anchor rods can apply large prestress, but they are difficult to dig out when used. Fiberglass anchor rods have low stiffness, small elongation, and poor plasticity. Although they are easy to dig out, they cannot apply large prestress and are easily broken by the extrusion and shearing of the cracked surrounding rock when used.

[0004] Different from radial anchors in the cavern, face anchors will be continuously removed as tunnel excavation progresses. They are temporary support measures. However, the removed anchors cannot be reused. When a large number of anchors are used, the economic benefits are poor. Summary of the invention

[0005] The present invention proposes an advanced prestressed anchor rod and construction method for a tunnel face, which solves the problem that traditional anchor rods cannot provide active support resistance, avoids the problem that steel face anchor rods are difficult to remove and glass fiber reinforced plastic anchor rods are easily broken due to compression, and makes part of the anchor rod body reusable.

[0006] The solution adopted by the present invention to solve the technical problem is a tunnel face advance prestressed anchor, including an anchor rod body, wherein the anchor rod body is formed by connecting a plurality of rod-shaped components in sequence, and adjacent rod-shaped components are connected via connecting screw sleeves. The bottom of the anchor rod body is bonded to the surrounding rock of the anchor hole via an anchoring agent, and the portion of the top of the rod body exposed to the surrounding rock is provided with an anchor tray. A fastening nut matching the thread of the anchor rod body is provided on the outside of the anchor rod tray, and the anchor rod tray is locked to the surrounding rock of the anchor hole via the fastening nut.

[0007] Furthermore, the rod-shaped component is a hot-rolled ribbed steel bar, and both ends of the rod-shaped component are processed with external threads corresponding to the internal threads on the connecting screw sleeve.

[0008] Furthermore, the rod-shaped component is a precision-rolled threaded steel bar, and an external thread is formed on its outer circumference.

[0009] Furthermore, the connecting screw sleeve is a hollow steel pipe with internal threads, and the inner diameter of the connecting screw is the same as the diameter of the rod-shaped component.

[0010] Furthermore, the anchor rod tray is a metal butterfly tray, and a hole corresponding to the diameter of the rod-shaped component is reserved in the middle of the anchor rod tray.

[0011] A method for constructing an advanced prestressed anchor rod at a tunnel face comprises the following steps:

[0012] (1) The length of the rod-shaped member is determined according to the excavation volume of each tunnel cycle, and the number of rod-shaped members is determined according to the length of the advanced support of the tunnel face;

[0013] (2) Connecting a plurality of rod-shaped components through connecting nuts to form an anchor rod body;

[0014] (3) After drilling a hole at the planned support position on the tunnel face, use the anchor rod to deliver the resin anchor to the bottom of the hole, start the drilling rig to drive the anchor rod to rotate, and push it to the bottom of the hole at a uniform speed;

[0015] (4) After the anchor strength reaches the design requirements, install the anchor tray and tighten the nut in sequence;

[0016] (5) The anchor rod body is tensioned by the tensioning device. After tensioning to the set load, the fastening nut is tightened and the tensioning device is removed;

[0017] (6) When the excavation continues at the face, remove the fastening nuts and anchor trays and carry out blasting or mechanical excavation;

[0018] (7) After excavation is completed, the rod-shaped components and connecting devices extending outside the tunnel face are removed, the tray and fastening nuts are reinstalled on the remaining anchor rod body, and prestress is applied again;

[0019] (8) Repeat steps (6) and (7) until all anchor rods are removed. The removed anchor rods can be straightened using a steel bar straightening machine depending on their deformation and then reused for face support.

[0020] Compared with the prior art, the present invention has the following beneficial effects: simple structure, reasonable design, ability to apply larger prestress, ability to quickly and effectively provide support resistance at the initial stage of deformation of the surrounding rock at the face, and simultaneous ability to synchronously disassemble the anchor rod body components as the tunnel face is excavated, which can fully ensure the effect of the face anchor support while adapting to tunnel excavation requirements and increasing the reusability of the face anchor. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention is further described below in conjunction with the accompanying drawings.

[0022] Figure 1 This is a structural diagram of the anchor in use;

[0023] Figure 2 Schematic diagram of the connection structure of adjacent rod-shaped components.

[0024] In the figure: 1-fastening nut; 2-anchor tray; 3-anchor hole surrounding rock; 4-connecting screw sleeve; 5-rod-shaped component; 6-anchoring agent. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0026] like Figure 1-2 As shown, a tunnel face advance prestressed anchor includes an anchor rod body, which is formed by connecting a plurality of rod-shaped components 5 in sequence, and adjacent rod-shaped components are connected via connecting screw sleeves 4. The bottom of the anchor rod body is bonded to the surrounding rock 3 of the anchor hole via an anchoring agent 6, and the portion of the top of the rod body exposed to the surrounding rock is covered with an anchor tray 2. A fastening nut 1 that matches the thread of the anchor rod body is provided on the outside of the anchor tray, and the anchor tray is locked to the surrounding rock of the anchor hole via the fastening nut.

[0027] In this embodiment, the rod-shaped member is a hot-rolled ribbed steel bar, and both ends of the rod-shaped member are processed with external threads corresponding to the internal threads on the connecting screw sleeve.

[0028] In this embodiment, the rod-shaped member is a precision-rolled threaded steel bar, and an external thread is formed on its outer circumference.

[0029] In this embodiment, the connecting screw sleeve is a hollow steel pipe with internal threads, and the inner diameter of the connecting screw sleeve is the same as the diameter of the rod-shaped component.

[0030] In this embodiment, the anchoring agent is a resin anchoring agent divided by polyester film and packaged in a two-component roll shape.

[0031] In this embodiment, the anchor rod tray is a metal butterfly tray, and a hole corresponding to the diameter of the rod-shaped component is reserved in the middle of the anchor rod tray.

[0032] A method for constructing an advanced prestressed anchor rod at a tunnel face comprises the following steps:

[0033] (1) The length of the rod-shaped member is determined according to the excavation volume of each tunnel cycle, and the number of rod-shaped members is determined according to the length of the advanced support of the tunnel face;

[0034] (2) Connecting a plurality of rod-shaped components through connecting nuts to form an anchor rod body;

[0035] (3) After drilling a hole at the planned support position on the tunnel face, use the anchor rod to deliver the resin anchor to the bottom of the hole, start the drilling rig to drive the anchor rod to rotate, and push it to the bottom of the hole at a uniform speed;

[0036] (4) After the anchor strength reaches the design requirements, install the anchor tray and tighten the nut in sequence;

[0037] (5) The anchor rod body is tensioned by the tensioning device. After tensioning to the set load, the fastening nut is tightened and the tensioning device is removed;

[0038] (6) When the excavation continues at the face, remove the fastening nuts and anchor trays and carry out blasting or mechanical excavation;

[0039] (7) After excavation is completed, the rod-shaped components and connecting devices extending outside the tunnel face are removed, the tray and fastening nuts are reinstalled on the remaining anchor rod body, and prestress is applied again;

[0040] (8) Repeat steps (6) and (7) until all anchor rods are removed. The removed anchor rods can be straightened using a steel bar straightening machine depending on their deformation and then reused for face support.

[0041] If this patent discloses or involves components or structural parts that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (for example, connected by bolts or screws), or as: a non-detachable fixed connection (for example, riveting, welding). Of course, the fixed connection can also be replaced by an integrated structure (for example, manufactured by a casting process) (except when it is obviously impossible to use an integrated forming process).

[0042] In the description of this patent, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing this patent, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this patent.

[0043] The preferred embodiments listed above further illustrate the objectives, technical solutions and advantages of the present invention in detail. It should be understood that the above description is only 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 should be included in the protection scope of the present invention.

Claims

1. A tunnel face advanced prestressed anchor bolt, characterized in that: The anchor rod body comprises a plurality of rod-shaped components connected in sequence, the adjacent rod-shaped components are connected via connecting screw sleeves, the bottom of the anchor rod body is bonded to the surrounding rock of the anchor hole via an anchoring agent, the portion of the top of the rod body exposed to the surrounding rock is covered with an anchor tray, a fastening nut matching the thread of the anchor rod body is arranged on the outside of the anchor tray, and the anchor tray is locked on the surrounding rock of the anchor hole via the fastening nut; The construction method of the advanced prestressed anchor bolt on the tunnel face comprises the following steps: (1) The length of the rod-shaped member is determined according to the tunnel excavation volume per cycle, and the number of rod-shaped members is determined according to the advance support length of the tunnel face; (2) Connecting a plurality of rod-shaped components through connecting nuts to form an anchor rod body; (3) After drilling a hole at the planned support position on the tunnel face, use the anchor rod to deliver the resin anchor to the bottom of the hole, start the drilling rig to drive the anchor rod to rotate, and push it to the bottom of the hole at a uniform speed; (4) After the anchor strength reaches the design requirements, install the anchor tray and tighten the nut in sequence; (5) The anchor rod body is tensioned by the tensioning device. After tensioning to the set load, the fastening nut is tightened and the tensioning device is removed; (6) When the excavation continues at the face, remove the fastening nuts and anchor trays and carry out blasting or mechanical excavation; (7) After excavation is completed, the rod-shaped components and connecting devices extending outside the tunnel face are removed, the tray and fastening nuts are reinstalled on the remaining anchor rod body, and prestress is applied again; (8) Repeat steps (6) and (7) until all anchor rods are removed. The removed anchor rods can be straightened using a steel bar straightening machine depending on their deformation and then reused for face support.

2. The tunnel face advance prestressed anchor bolt according to claim 1, characterized in that: The rod-shaped component is a hot-rolled ribbed steel bar, and both ends of the rod-shaped component are processed with external threads corresponding to the internal threads on the connecting screw sleeve.

3. The tunnel face advance prestressed anchor bolt according to claim 1, characterized in that: The rod-shaped component is a precision-rolled threaded steel bar, and an external thread is formed on its outer circumference.

4. The tunnel face advance prestressed anchor bolt according to claim 1, characterized in that: The connecting screw sleeve is a hollow steel pipe with internal threads, and the inner diameter of the connecting screw is the same as the diameter of the rod-shaped component.

5. The tunnel face advance prestressed anchor bolt according to claim 1, characterized in that: The anchor rod tray is a metal butterfly tray, and a hole corresponding to the diameter of the rod-shaped component is reserved in the middle of the anchor rod tray.

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