Self-sensing intelligent anchor rod

Abstract

The invention discloses a self-sensing intelligent anchor rod which comprises a head part, a sensing area and a tail end, the sensing area is provided with a straight groove and a spiral groove, distributed optical fiber sensors for sensing stress-strain information of surrounding rocks in a monitoring area are arranged in the straight groove and the spiral groove, and the stress-strain and strain-deformation relational expressions of an anchor rod structure are used for sensing the stress-strain information of the surrounding rocks in the monitoring area. And sensing tunnel surrounding rock support deformation information. The device has the advantages that the axial tensile deformation of the anchor rod can be sensed, local torsion and bending deformation information can be obtained to a certain extent, and the working state of a tunnel supporting structure can be sensed more comprehensively.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel engineering, and in particular to a self-sensing intelligent anchor rod. Background Art

[0002] In recent years, domestic tunnel construction technology has developed rapidly, and many technologies have reached the international leading level. With the continuous development of deep underground space in cities in my country, the requirements for tunnel construction technology have gradually increased. The anchor structure plays an important role in tunnel surrounding rock support, providing great help for the stability of the tunnel support structure. At the same time, the failure form of the anchor itself directly reflects the failure form of the surrounding rock, and the stress and deformation state of the anchor itself also indirectly reflects the service state of the tunnel surrounding rock support structure. Therefore, effectively grasping the working state of the anchor structure can reflect the actual working conditions of the tunnel surrounding rock, thereby ensuring the safety of the tunnel project.

[0003] The existing anchor structure cannot feedback its own working status, and the existing monitoring means mostly obtain deformation information through point sensors or linear sensors, which can only obtain the status information of a certain point or a certain part of the anchor. The torsion and bending information of the anchor itself is difficult to obtain, and the working status of the anchor inside the surrounding rock cannot be effectively perceived. The service status of the tunnel support and the deformation status of the tunnel surrounding rock cannot be effectively evaluated. Therefore, it is impossible to make timely adjustments and responses according to the actual status to ensure the safety of the tunnel and prevent accidents. The present invention combines the anchor with a distributed optical fiber sensor, introduces a spiral measuring line, and proposes a new type of self-sensing intelligent anchor based on the principle of OFDR technology. It not only obtains the deformation information along the axial direction of the anchor, but also captures the torsion and bending deformation information, so as to achieve effective perception and comprehensive grasp of the state of the anchor itself, which is the area that needs to be improved in this application. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a self-sensing intelligent anchor rod, which can obtain the working status of the anchor rod itself in real time and perceive the working status of the tunnel support structure more comprehensively.

[0005] In order to solve the above technical problems, the present invention provides a self-sensing intelligent anchor rod, including a head, a sensing area and a tail end. The sensing area is provided with straight grooves and spiral grooves. Distributed optical fiber sensors for sensing various stress and strain information in the surrounding rock in the monitoring area are arranged in the straight grooves and the spiral grooves. Based on the stress-strain and strain-deformation relationship expressions of the anchor rod structure, the deformation information of the tunnel surrounding rock support is sensed.

[0006] The distributed optical fiber sensors in the straight groove sense the axial deformation and bending deformation information of the surrounding rock along the anchor rod, and the distributed optical fiber sensors in the spiral groove sense the torsional deformation and bending deformation information to obtain the deformation law of the tunnel surrounding rock.

[0007] Based on the material mechanics theory, the stress-strain and strain-deformation relationship expressions of the anchor structure of the present invention under the action of axial tension and compression, bending load and torsion load are given as follows:

[0008] (1) When subjected to axial force along the length of the anchor rod, the stress and strain of the optical fiber sensor in the straight groove is expressed as:

[0009]

[0010]

[0011] Where: σ is stress, ε is strain, E is the elastic modulus of the material, and N is the axial force;

[0012] The stress and strain along the direction of the spiral optical fiber sensor can be expressed as:

[0013]

[0014] Where: θ and ε θ are the stress and strain along the direction of the spiral sensor, respectively, N is the axial force, d is the cross-sectional diameter of the anchor rod, v is the Poisson’s ratio of the material, and θ is the angle between the spiral optical fiber and the cross-sectional area of ​​the anchor rod;

[0015] The axial deformation of the anchor rod Δl and the strain of the spiral sensor ε θ The relationship is expressed as:

[0016]

[0017] (2) When torsional deformation occurs under torsional load, the linear sensor cannot capture the deformation information, and only the spiral sensor can obtain the deformation information caused by torsion:

[0018] ① When the rotation direction of the spiral sensor is consistent with the rotation direction of the torsional force, the stress-strain relationship is expressed as:

[0019]

[0020] Where: T is torque;

[0021] The arc θ0 produced by the anchor bolt torsion is expressed as:

[0022]

[0023] Where: G is the shear modulus;

[0024] ② When the rotation direction of the spiral sensor is opposite to the direction of the torsional force applied, the stress-strain relationship is expressed as:

[0025]

[0026] The arc θ0 produced by the torsional deformation of the anchor rod is expressed as:

[0027]

[0028] (3) Subject to bending load M z When deformation occurs, the force deformation of the linear sensor is expressed as:

[0029]

[0030]

[0031] Where: y is the distance from the sensor to the center axis of the anchor;

[0032] The stress and strain of the spiral sensor is expressed as:

[0033]

[0034] The anchor angle change Δθ(x) and deflection Δy(x) are expressed as:

[0035]

[0036] Where: + is the strain of the optical fiber in the tension zone, ε - is the strain of the optical fiber in the compressed area, and D is the distance between the linear optical fiber sensors.

[0037] The straight grooves are arranged along the circumference of the rod body of the anchor rod.

[0038] The tail end is provided with a through hole, and the distributed optical fiber sensor leads out the connecting wire through the through hole and is connected to the optical fiber demodulator.

[0039] The connecting line is directly replaced by a distributed optical fiber sensor, and the length is flexibly selected according to actual conditions, and the reserved length is sufficient for effective connection with the optical fiber demodulator.

[0040] The widths of the straight groove and the spiral groove are set according to the distributed optical fiber sensor.

[0041] The depths of the straight groove and the spiral groove are selected according to the depth difference of the parameters of the distributed optical fiber sensor, so that each distributed optical fiber sensor can sense the mechanical parameters independently.

[0042] The sensing length of the spiral groove along the axial direction of the anchor rod is the same as that of the straight groove, which is convenient for data comparison and theoretical analysis.

[0043] The pitch of the spiral groove is customized according to on-site requirements.

[0044] The distributed optical fiber sensor is a customized special optical fiber sensor to ensure the accuracy of the sensed data.

[0045] The beneficial effects of the present invention are:

[0046] (1) It has a self-sensing function to obtain the working status of the anchor in real time;

[0047] (2) It can not only sense the axial tensile deformation of the anchor rod, but also obtain local torsional and bending deformation information to a certain extent, and more comprehensively perceive the working status of the tunnel support structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0049] Figure 1 It is a structural schematic diagram of a specific embodiment of the present invention;

[0050] Description of the symbols in the figure

[0051] 1—Self-sensing intelligent anchor rod; 2—Straight groove;

[0052] 3—Spiral groove; 4—Through hole;

[0053] 5—Distributed optical fiber sensor; 6—Connecting wire;

[0054] 7—Fiber optic demodulator. DETAILED DESCRIPTION

[0055] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0056] Based on the material mechanics theory, the stress-strain and strain-deformation relationship expressions of the anchor structure of the present invention under the action of axial tension and compression, bending load and torsion load are given as follows:

[0057] (1) When subjected to axial force along the length of the anchor rod, the stress and strain of the optical fiber sensor in the straight groove is expressed as:

[0058]

[0059] Where: σ is stress, ε is strain, E is the elastic modulus of the material, and N is the axial force;

[0060] The stress and strain along the direction of the spiral optical fiber sensor can be expressed as:

[0061]

[0062] Where: θ and εθ are the stress and strain along the direction of the spiral sensor, respectively, N is the axial force, d is the cross-sectional diameter of the anchor rod, v is the Poisson’s ratio of the material, and θ is the angle between the spiral optical fiber and the cross-sectional area of ​​the anchor rod;

[0063] The axial deformation of the anchor rod Δl and the strain of the spiral sensor ε θ The relationship is expressed as:

[0064]

[0065] (2) When torsional deformation occurs under torsional load, the linear sensor cannot capture the deformation information, and only the spiral sensor can obtain the deformation information caused by torsion:

[0066] ① When the rotation direction of the spiral sensor is consistent with the rotation direction of the torsional force, the stress-strain relationship is expressed as:

[0067]

[0068] Where: T is torque;

[0069] The arc θ0 produced by the anchor bolt torsion is expressed as:

[0070]

[0071] Where: G is the shear modulus;

[0072] ② When the rotation direction of the spiral sensor is opposite to the direction of the torsional force applied, the stress-strain relationship is expressed as:

[0073]

[0074] The arc θ0 produced by the torsional deformation of the anchor rod is expressed as:

[0075]

[0076] (3) Subject to bending load M z When deformation occurs, the force deformation of the linear sensor is expressed as:

[0077]

[0078] Where: y is the distance from the sensor to the center axis of the anchor;

[0079] The stress and strain of the spiral sensor is expressed as:

[0080]

[0081] The anchor angle change Δθ(x) and deflection Δy(x) are expressed as:

[0082]

[0083] Where: + is the strain of the optical fiber in the tension zone, ε - is the strain of the optical fiber in the compressed area, and D is the distance between the linear optical fiber sensors.

[0084] like Figure 1 As shown, the present invention provides a self-sensing intelligent anchor rod, including three areas A, B, and C, which are respectively the head, the sensing area and the tail end. The sensing area is provided with a straight groove 2 and a spiral groove 3. The straight groove 2 and the spiral groove 3 are provided with distributed optical fiber sensors 5 for sensing various stress and strain information at the surrounding rock in the monitoring area. Based on the stress-strain and strain-deformation relationship expressions of the anchor rod structure, the deformation information of the tunnel surrounding rock support is sensed.

[0085] The distributed optical fiber sensor 5 in the straight groove 2 senses the axial deformation and bending deformation information of the surrounding rock along the anchor rod, and the distributed optical fiber sensor 5 in the spiral groove 3 senses the torsional deformation and bending deformation information to obtain the deformation law of the tunnel surrounding rock.

[0086] The length of the anchor rod 1 is 3m, and the length of the sensing area is 0.5m to 2.5m. Four straight grooves 2 are arranged along the circumference of the anchor rod in the sensing area and the tail end with a gradient of 90° around the anchor rod, with a width × depth of 5mm × 10mm; a spiral groove 3 is prefabricated in the sensing area, with a width × depth of 5mm × 5mm and a pitch of 40mm, and the straight groove at the tail end is directly used as a through hole 4.

[0087] A dedicated distributed optical fiber sensor 5 coated with polyimide PI with a length of 15 m is selected and encapsulated in the straight groove 2 and the spiral groove 3 using epoxy resin glue. Finally, the remaining distributed optical fiber sensor is led out through the straight groove at the tail end as a connecting line 6.

[0088] Use a fiber fusion splicer to fuse the jumper and the distributed fiber optic sensor 5 to facilitate subsequent connection with the fiber optic demodulator 7, and protect the connecting line 6 and the jumper to prevent damage during the construction process.

[0089] The working principle of the present invention is as follows: the self-sensing intelligent anchor rod 1 is installed into the support structure as the construction progresses. After the on-site construction is completed, the jumper is connected to the optical fiber demodulator 7, and the reference file and test parameters are set and saved. The anchor rod stress and strain parameters are obtained for a long time as needed to achieve effective perception of the working state of the anchor rod and effective evaluation of the deformation state of the surrounding rock support structure.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A self-sensing intelligent anchor, characterized in that: It includes a head, a sensing area and a tail end. The sensing area is provided with straight grooves and spiral grooves. Distributed optical fiber sensors for sensing the stress and strain information of the surrounding rock in the monitoring area are arranged in the straight grooves and spiral grooves. Based on the stress-strain and strain-deformation relationship expressions of the anchor structure, the deformation information of the tunnel surrounding rock support is sensed.

2. The self-sensing intelligent anchor according to claim 1, characterized in that: The distributed optical fiber sensors in the straight groove sense the axial deformation and bending deformation information of the surrounding rock along the anchor rod, and the distributed optical fiber sensors in the spiral groove sense the torsional deformation and bending deformation information to obtain the deformation law of the tunnel surrounding rock.

3. The self-sensing intelligent anchor according to claim 1 or 2, characterized in that: The stress-strain and strain-deformation relationship expressions of the anchor structure are as follows: (1) When subjected to axial force along the length direction of the anchor rod, the stress and strain of the distributed optical fiber sensor in the straight groove is expressed as: Where: σ is stress, ε is strain, E is the elastic modulus of the material, and N is the axial force; The stress and strain along the direction of the spiral optical fiber sensor can be expressed as: Where: θ and ε θ are the stress and strain along the direction of the spiral sensor, respectively, N is the axial force, d is the cross-sectional diameter of the anchor rod, v is the Poisson’s ratio of the material, and θ is the angle between the spiral optical fiber and the cross-sectional area of ​​the anchor rod; The axial deformation of the anchor rod Δl and the strain ε along the direction of the spiral sensor θ The relationship is expressed as: (2) When torsional deformation occurs under the action of torsional load, the spiral sensor obtains the deformation information caused by torsion: ① When the rotation direction of the spiral sensor is consistent with the rotation direction of the torsional force, the stress-strain relationship is expressed as: Where: T is torque; The arc θ0 produced by the anchor bolt torsion is expressed as: Where: G is the shear modulus; ② When the rotation direction of the spiral sensor is opposite to the direction of the torsional force applied, the stress-strain relationship is expressed as: The arc θ0 produced by the torsional deformation of the anchor rod is expressed as: (3) Subject to bending load M z When deformation occurs, the force deformation of the linear sensor is expressed as: Where: y is the distance from the sensor to the center axis of the anchor; The stress and strain of the spiral sensor is expressed as: The anchor angle change Δθ(x) and deflection Δy(x) are expressed as: Where: + is the strain of the optical fiber in the tension zone, ε - is the strain of the optical fiber in the compressed area, and D is the distance between the linear optical fiber sensors.

4. The self-sensing intelligent anchor according to claim 1, characterized in that: The straight grooves are arranged along the circumference of the rod body of the anchor rod.

5. The self-sensing intelligent anchor according to claim 1, characterized in that: The tail end is provided with a through hole, and the distributed optical fiber sensor leads out the connecting wire through the through hole and is connected to the optical fiber demodulator.

6. The self-sensing intelligent anchor according to claim 4, characterized in that: As a part of the distributed optical fiber sensor, the connecting line has a reserved length sufficient for effective connection with the optical fiber demodulator.

7. The self-sensing intelligent anchor according to claim 1, characterized in that: The widths of the straight groove and the spiral groove are set according to the distributed optical fiber sensor.

8. The self-sensing intelligent anchor according to claim 1, characterized in that: The depths of the straight groove and the spiral groove are selected according to the depth difference of the parameters of the distributed optical fiber sensor, so that each distributed optical fiber sensor can sense the mechanical parameters independently.

9. The self-sensing intelligent anchor according to claim 8, characterized in that: The sensing length of the spiral groove along the axial direction of the anchor rod is the same as that of the straight groove, which is convenient for data comparison and theoretical analysis.

10. The self-sensing intelligent anchor according to claim 9, characterized in that: The pitch of the spiral groove is customized according to on-site requirements.

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