CN211080330U - A Fiber Bragg Grating Strain Measurement Model for Geotechnical Expansion Bolts - Google Patents

Abstract

The utility model discloses a fiber grating strain measurement model for a rock-soil expansion anchor rod, which comprises a metal rod, a pressure end, a sleeve, a hollow rod and a fiber grating. The upper end of the sleeve is open and the lower end is closed. The bottom of the pressure end is a disk, and at least three rings are arranged on the top, and each ring is connected with the bottom disk by four pressure columns arranged at equal intervals. The pressure column of the pressure end and the bottom disc part are inserted into the sleeve from the upper end opening, and the bottom disc and the sleeve chassis are fixedly connected through a hollow rod. The metal rod is fixedly connected to the top surface of the bottom disc of the pressure end through the innermost ring at the top of the pressure end. Several fiber gratings are respectively pasted on the metal rod, each pressure column of the pressure end and the hollow rod. When the whole model is embedded in the rock and soil body, the pulling force is directly applied to the top of the metal rod, and the strain of each part of the model can be obtained through the fiber grating of each part, and then the internal force of the expanded anchor model can be obtained by calculation.

Description

A Fiber Bragg Grating Strain Measurement Model for Geotechnical Expansion Bolts

technical field

The utility model relates to the technical field of geotechnical engineering, in particular to a fiber grating strain measurement model used for a rock and soil expansion bolt.

Background technique

Due to the characteristic of the expansion bolt in geotechnical engineering, which is significantly different from the traditional friction type rock bolt, its bearing mechanism is relatively complicated. In order to clearly obtain the determination method and deformation performance of the expansion anchor bolt, the load transfer mechanism and failure mode of the expanded anchor bolt are directly observed by the test method. scientific basis.

Model tests are used in the field of geotechnical engineering, and can be used to study the engineering mechanical properties of geotechnical engineering materials, geotechnical engineering components and geotechnical engineering structures, and solve theoretical and practical problems with a small cost. The model test can strictly control the main parameters of the test object, it is not easy to be restricted and interfered by external conditions, the results are accurate, the test results are consistent and comparable, and it can also highlight the main contradiction of the research object under complex conditions, grasp and discover The internal connection of the experimental phenomenon is compared and verified with the results of the field test.

The body shape of the geotechnical expansion bolt is complex, and there is a hole with an enlarged diameter at the bottom end of the ordinary bolt hole in the geotechnical layer. Because the entire expanded bolt structure is embedded in the rock and soil mass, the deformation and axial force of the rod body are very difficult to obtain. Therefore, due to the limitations of the test methods, the bearing capacity distribution of the expanded body bolt has not been accurately obtained so far, and there is no relevant report.

In order to obtain the distribution state of the bearing capacity of the expanded body bolt and further study its mechanical properties, it is a mechanically reasonable and technically feasible research method to use the method of geometrically scaling down the expanded body bolt to carry out the model test. However, it is difficult to accurately obtain the small amount of strain in a small space by using the traditional strain sensor after the geometric scale of the expanded anchor is reduced.

In recent years, optical fiber sensing technology has attracted extensive attention worldwide and has been rapidly developed, among which the development of fiber grating sensing technology is the most rapid. Compared with traditional mechanical and electronic sensors, fiber grating sensors have the following advantages: 1) small size and light weight, 2) low transmission loss and high bandwidth, 3) immunity to electromagnetic interference, 4) corrosion resistance, 5) long service life , 6) Distributed measurements can be performed using multiplexing techniques. Therefore, the fiber grating strain measurement technology is applied to the rod body strain measurement of the expansion anchor, and a new fiber grating strain measurement model for the geotechnical expansion anchor is used to solve the difficulty of the geotechnical expansion anchor due to the complex shape. Obtaining the distribution of bearing capacity leads to the lack of research on its bearing mechanism.

Utility model content

The utility model provides a fiber grating strain measurement model for the geotechnical expansion bolt in order to overcome the difficulty in obtaining the rod body stress distribution caused by the complex body shape of the existing geotechnical expansion bolt.

To achieve the above object, the technical scheme adopted by the present utility model is as follows:

A fiber grating strain measurement model for rock and soil expansion bolts, including a metal rod, a pressure end, a sleeve, a hollow rod and a fiber grating; the metal rod passes through the central hole of the top ring of the pressure end and fixed at the center of the bottom disc of the pressure end; the pressure column and the bottom disc of the pressure end are inserted into the sleeve from the upper end opening of the sleeve; the top of the hollow rod It is fixedly connected to the bottom disc of the pressure end, and the bottom is fixedly connected to the bottom plate of the sleeve; a plurality of the fiber gratings are respectively pasted on the metal rod, the pressure column of the pressure end and the hollow rod .

Wherein, the metal rod is a metal rod of equal diameter or threaded, and its top end is a free end for connecting with an external loading device; its bottom end passes through the center hole of the innermost ring at the top of the pressure end and is connected with The bottom disc of the pressure end is fixedly connected; at least one fiber grating is pasted on the side surface of the metal rod near the top, and the side surface of the metal rod near the top ring of the pressure end is pasted with At least 1 fiber grating.

Wherein, the pressure end includes three layers, the top layer is provided with at least three concentric non-equal diameter rings, and the bottom layer is provided with a bottom disk, each ring and the bottom disk are arranged at least four equal distances The pressure column is connected, and at least one fiber grating is pasted on each of the pressure columns; a flexible isolation ring is arranged between every two adjacent rings and between the innermost ring and the metal rod so that the adjacent rings are not in direct contact; the outer diameter of the top outermost ring is larger than the outer diameter of the bottom disc.

The sleeve is a cylinder with an open upper end and a closed lower end, the inner diameter of the sleeve is slightly larger than the outer diameter of the bottom disc of the pressure end, and the outer diameter of the sleeve is equal to the top of the pressure end The outer diameter of the outermost disk.

Wherein, the hollow rod is located inside the sleeve and coincides with the axis of symmetry of the sleeve; the top end of the hollow rod is fixedly connected with the bottom end of the bottom disc of the pressure end, and the hollow rod The bottom end of the sleeve is fixedly connected with the top surface of the sleeve chassis; at least one fiber grating is pasted on the hollow rod.

Wherein, the pressure column and the bottom disc of the pressure end are inserted into the sleeve through the upper end opening of the sleeve, and are fixedly connected to the sleeve through the hollow rod; The sum of the length of the pressure column, the thickness of the bottom disc of the pressure end, the length of the hollow rod and the thickness of the bottom plate of the sleeve is slightly larger than the total height of the sleeve.

Wherein, the wires of the fiber grating attached to the pressure column included in the pressure end are led to the inside of the sleeve through a plurality of openings reserved on the bottom disc of the pressure end. The optical fiber gratings pasted on the pressure column and the wires of the optical fiber grating pasted on the hollow rod pass out of the model through the reserved space on the sleeve chassis. The wires of the fiber grating pasted on the metal rod lead out the model at the top of the metal rod.

As shown in FIG. 6 , the principle realized by the present invention is: the bearing capacity of the rock-soil expansion bolt is composed of the side resistance Q _sd of the ordinary anchoring section, the side resistance Q _sD of the expansion anchoring section and the end resistance Q _e . When a pull-out load is applied to the top of the common anchoring section of the expanded-body bolt model buried in the sand foundation model, the top surface of the pressure sensing end will generate end resistance due to the pressure of the sand foundation. The pressure columns are respectively vertically deformed under the action of the foundation reaction force. At this time, the wavelength change value of the fiber Bragg strain sensor on each pressure column obtained by the fiber grating demodulator can obtain the deformation amount of each pressure column, and then pass The average deformation and force value of the pressure ring are obtained from the deformation of the 4 pressure columns on each pressure ring. Finally, the pressure values on the 3 pressure rings are added together to obtain the end resistance value of the expansion bolt under this working condition. Q _e , and by analyzing the pressure values on the three rings divided by the area of the corresponding ring, the distribution of the resistance at the end of the expansion bolt can be obtained.

For the lateral resistance Q _s of the expanded body bolt, firstly when the bolt is subjected to the uplift load, the side wall of the hollow expanded body anchor body of the expanded body bolt model deviates from the pressure sensing end due to the friction of the sand foundation. At this time, the hollow rod inside the hollow expansion anchor body produces tensile strain, and the change value of the wavelength of the FBG sensor on the hollow rod can be obtained by the fiber grating demodulator, and the strain value of the hollow rod can be obtained, and then the hollow rod's strain value can be obtained. The tensile force value is the frictional resistance of the side wall of the hollow expansion anchor body subjected to the sand foundation, that is, the lateral resistance value Q _sD of the anchor bolt expansion body anchoring section.

On the basis of obtaining the end resistance value of the expanded body anchor and the side resistance value of the expanded anchoring section, the total tensile force value Q received by the bolt under this working condition is subtracted from the end resistance value Q _e of the expanded body anchor and the expanded body anchor. The side resistance value Q _{sd of the body anchoring section can be obtained from the side resistance value Q sd of} the common anchoring section of the expanded body bolt.

Therefore, the strain value of the rod body under the condition of the pull-out force of the expanded-body anchor can be obtained through the expanded-body anchor model of the present invention, and then the load distribution on the anchor can be obtained.

Compared with the prior art, the outstanding effect of the present utility model is:

The utility model is suitable for the fiber grating strain measurement model of the geotechnical expansion bolt, and the internal force distribution of the expanded bolt can be obtained directly by measuring the strain value of the fiber grating arranged on the model of the utility model in the model test of the expanded bolt. , which greatly improves the accuracy and stability of the strain measurement of the expanded bolt model, and the measurement elements are not affected by the soil and water conditions in the simulated stratum by the model test. It can realize accurate and repeatable model test of the internal force distribution of the expanded body bolt under the condition of small scale and scale of the expanded body bolt model, which saves the test cost and overcomes the difficulty in obtaining the internal force distribution in the traditional expanded body bolt test. problem. At the same time, the model mechanics concept of the utility model is clear, the model structure is simple, and the model installation and model size replacement are convenient.

The fiber grating strain measurement model for rock-soil expansion bolts of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

Description of drawings

FIG. 1 is a schematic diagram of the overall structure of the fiber grating strain measurement model used for the rock-soil expansion bolt according to the present invention.

FIG. 2 is a schematic diagram of the structural disassembly of the fiber grating strain measurement model used for the rock-soil expansion bolt according to the present invention.

FIG. 3 is a schematic structural diagram of the sensing end of the fiber grating strain measurement model used for the rock-soil expansion bolt according to the present invention.

FIG. 4 is a top view of the sensing end of the fiber grating strain measurement model for the rock-soil expansion bolt of the present invention.

FIG. 5 is an overall appearance diagram of the fiber grating strain measurement model used for the rock-soil expansion bolt according to the present invention.

FIG. 6 is a mechanical principle diagram of the fiber grating strain measurement model used for the rock-soil expansion bolt according to the present invention.

Detailed ways

1-5, a fiber grating strain measurement model for geotechnical expansion bolt, including metal rod 1, pressure end 2, sleeve 4, hollow rod 3 and fiber grating 9; metal rod 1 wears The center hole of the top circular ring of the overpressure end 2 is fixed to the center of the bottom disc 5 of the pressure end 2; the pressure column 7 and the bottom disc 5 of the pressure end 2 are inserted into the sleeve from the upper end opening of the sleeve 4 In 4; the top of the hollow rod 3 is fixedly connected to the bottom disc 5 of the pressure end, and the bottom is fixedly connected to the sleeve chassis 8; a number of fiber gratings 9 are respectively pasted on the metal rod 1 and the pressure column of the pressure end 2 7 on and 3 on the hollow rod.

The metal rod 1 is an equal diameter or threaded metal rod, and its top end is a free end for connecting with an external loading device; its bottom end passes through the central hole of the innermost ring 6 at the top of the pressure end 2 and connects with the pressure end. The bottom disc 5 is fixedly connected; at least one fiber grating 9 is pasted on the side surface of the metal rod 1 near the top, and at least one fiber grating 9 is pasted on the side of the metal rod 1 near the top ring 6 of the pressure end 2 Fiber Bragg Grating 9.

As shown in Figures 3-4, the pressure end 2 includes three layers, the top layer is provided with at least three concentric rings 6 of non-equal diameter, and the bottom layer is provided with a bottom disk 5, each ring 6 and the bottom circle The discs 5 are connected by at least 4 pressure columns 7 arranged at equal intervals, and at least one fiber grating 9 is pasted on each pressure column 7; between every two adjacent rings 6 and the innermost ring 6 A flexible spacer ring 10 is provided between the metal rod 1 so that the adjacent rings 6 are not in direct contact; the outer diameter of the top outermost ring 6 is larger than the outer diameter of the bottom disk 5 .

The sleeve 4 is a cylinder with an open upper end and a closed lower end. The inner diameter of the sleeve is slightly larger than the outer diameter of the bottom disc 5 of the pressure end 2, and the outer diameter of the sleeve 4 is equal to the outer diameter of the outermost disc 6 at the top of the pressure end 2. path.

The hollow rod 3 is located inside the sleeve 4 and coincides with the axis of symmetry of the sleeve 4; the top end of the hollow rod 3 is fixedly connected with the bottom end of the bottom disc 5 of the pressure end 2, and the bottom end of the hollow rod 3 is connected with the sleeve chassis The top surface of 8 is fixedly connected; at least one fiber grating 9 is pasted on the hollow rod 3 .

The pressure column 7 and the bottom disc 5 of the pressure end 2 are inserted into the sleeve 4 through the upper end opening of the sleeve 4, and are fixedly connected to the sleeve 4 through the hollow rod 3; the length of the pressure column 7 of the pressure end 2, the pressure The sum of the thickness of the bottom disc 5 of the end head 2, the length of the hollow rod 3 and the thickness of the chassis 8 of the sleeve 4 is slightly larger than the total height of the sleeve 4. After the entire model is assembled, the pressure end head 2 and the sleeve 4 belong to There are gaps 14 therebetween.

The wires 13 of the fiber grating 9 attached to the pressure column 7 included in the pressure end 2 are led to the inside of the sleeve 4 through several openings 11 reserved on the bottom disc 5 of the pressure end 2 . Both the fiber grating 9 pasted on the pressure column 7 and the wires 13 of the fiber grating 9 pasted on the hollow rod 3 pass through the model through the reserved holes 12 on the chassis 8 of the sleeve 4 . The wire 13 of the fiber grating 9 pasted on the metal rod 1 leads out the model at the top of the metal rod 1 .

The fiber grating strain measurement model of the utility model used for the rock-soil expansion bolt has been verified by repeated tests, and a satisfactory application effect has been achieved.

The above-mentioned embodiments are only to describe the preferred embodiments of the present invention, and do not limit the scope of the present invention. On the premise of not departing from the design spirit of the present invention, those of ordinary skill in the art can understand the technical solutions of the present invention. Various modifications and improvements made shall fall within the protection scope determined by the claims of the present utility model.

Claims (7)

1. The utility model provides a fiber grating strain measurement model for ground expanding stock which characterized in that: comprises a metal rod, a pressure end, a sleeve, a hollow rod and a fiber grating; the metal rod penetrates through a center hole of a circular ring at the top end of the pressure end head and is fixed at the center of a bottom circular disc of the pressure end head; the pressure column and the bottom disc of the pressure end head are inserted into the sleeve from the opening at the upper end of the sleeve; the top of the hollow rod is fixedly connected to a disc at the bottom of the pressure end head, and the bottom of the hollow rod is fixedly connected to the sleeve bottom plate; and the plurality of fiber gratings are respectively adhered to the metal rod, the pressure column of the pressure end head and the hollow rod.

2. The fiber bragg grating strain measurement model for the geotechnical expansion anchor rod according to claim 1, wherein: the metal rod is a metal rod with equal diameter or with threads, and the top end of the metal rod is a free end and is used for being connected with an external loading device; the bottom end of the pressure head penetrates through a central hole of the innermost circular ring at the top of the pressure head and is fixedly connected with a circular disc at the bottom of the pressure head; at least 1 fiber grating is pasted on the side surface of the metal rod close to the top end, and at least 1 fiber grating is pasted on the side surface of the metal rod close to the top ring of the pressure end.

3. The fiber bragg grating strain measurement model for the geotechnical expansion anchor rod according to claim 1, wherein: the pressure end comprises three layers, the top layer of the pressure end is provided with at least 3 concentric non-equal-diameter circular rings, the bottom layer of the pressure end is provided with 1 bottom disc, each circular ring is connected with the bottom disc through at least 4 pressure columns which are arranged at equal intervals, and at least 1 fiber bragg grating is adhered to each pressure column; flexible isolation rings are arranged between every 2 adjacent circular rings and between the innermost circular ring and the metal rod so that the adjacent circular rings are not in direct contact; the outer diameter of the outermost side ring of the top part is larger than that of the bottom disc.

4. The fiber bragg grating strain measurement model for the geotechnical expansion anchor rod according to claim 1, wherein: the sleeve is a cylinder with an opening at the upper end and a closed lower end, the inner diameter of the sleeve is slightly larger than the outer diameter of the bottom disc of the pressure end head, and the outer diameter of the sleeve is equal to the outer diameter of the outermost disc at the top of the pressure end head.

5. The fiber bragg grating strain measurement model for the geotechnical expansion anchor rod according to claim 1, wherein: the hollow rod is positioned inside the sleeve and is superposed with the symmetry axis of the sleeve; the top end of the hollow rod is fixedly connected with the bottom end of the bottom disc of the pressure end, and the bottom end of the hollow rod is fixedly connected with the top surface of the sleeve chassis; at least 1 fiber grating is adhered to the hollow rod.

6. The fiber bragg grating strain measurement model for the geotechnical expansion anchor rod according to claim 1, wherein: the pressure column and the bottom disc of the pressure end head are inserted into the sleeve through the upper end opening of the sleeve and are fixedly connected with the sleeve through the hollow rod; the sum of the length of the pressure column of the pressure end head, the thickness of the bottom disc of the pressure end head, the length of the hollow rod and the thickness of the bottom disc of the sleeve is slightly larger than the total height of the sleeve.

7. The fiber bragg grating strain measurement model for the geotechnical expansion anchor rod according to claim 1, wherein: the pressure end comprises a plurality of holes reserved on the bottom disc of the pressure end, and the guide wire of the optical fiber grating adhered to the pressure column is led to the interior of the sleeve through the holes; the fiber bragg grating pasted on the pressure column and the fiber bragg grating pasted on the hollow rod are both led out of the model through the reserved part on the sleeve chassis; and the fiber grating lead adhered to the metal rod leads out of the model from the top end of the metal rod.

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