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CN-116222850-B - Fiber bragg grating soil pressure sensor and monitoring system

CN116222850BCN 116222850 BCN116222850 BCN 116222850BCN-116222850-B

Abstract

The invention relates to a fiber grating soil pressure sensor and a monitoring system, which comprises a shell, a top cover, a spring plate combination, a measuring fiber and an optical cable, wherein the shell comprises a shell, the spring plate combination is fixed in an inner cavity of the shell, a grating is arranged in the middle of the measuring fiber, two ends of the measuring fiber are respectively and fixedly connected with the spring plate combination, the top cover comprises a cover plate and a force transmission block, the cover plate is fixed at the top of the shell and is used for sealing the inner cavity of the shell, the force transmission block is used for contacting with the spring plate combination to transmit pressure, when the pressure is transmitted, the spring plate combination transmits tensile forces in different directions to two ends of the measuring fiber, the optical cable is internally wrapped with a transmission fiber, the transmission fiber and a fiber core of the measuring fiber are welded into a whole, and after the shell, the top cover, the spring plate combination, the measuring fiber and the optical cable are assembled, outer heat preservation coatings with the thickness of not less than 2mm are sprayed on the outer surfaces of the shell and the top cover. The technical scheme effectively avoids the influence of temperature on the measurement result, and has high measurement accuracy.

Inventors

  • Song guangdong
  • Zhu Shengen
  • ZHANG JINQUAN
  • HU BINXIN
  • ZHU FENG
  • ZHANG HUA

Assignees

  • 山东省科学院激光研究所

Dates

Publication Date
20260508
Application Date
20230420

Claims (8)

  1. 1. The fiber bragg grating soil pressure sensor is characterized by comprising a shell (2), a top cover (4), an elastic sheet combination (5), a measuring fiber (6) and an optical cable (8), The shell (2) comprises a shell (201) with a bottom and no top, and an optical cable via hole (206) is arranged on the side surface of the shell (201); the elastic sheet combination (5) is fixedly connected with the shell (2) and is arranged in the inner cavity of the shell (201); A grating (601) with the length Lg is arranged in the middle of the measuring optical fiber (6) along the length direction, and two ends of the measuring optical fiber (6) are fixedly connected with the elastic sheet combination (5) respectively; The top cover (4) comprises a cover plate (401) and a force transmission block (402), wherein the cover plate (401) is fixed on the top of the shell (201) through a screw and is used for sealing an inner cavity of the shell (201), the force transmission block (402) is used for being in contact with the elastic sheet combination (5) to transmit pressure, the position of the force transmission block (402) corresponds to the middle position of the grating (601), and when the force transmission block (402) transmits pressure to the elastic sheet combination (5), the elastic sheet combination (5) transmits tensile forces in different directions to two ends of the measuring optical fiber (6) respectively; The inside of the optical cable (8) is wrapped with a transmission optical fiber (7), the transmission optical fiber (7) and the fiber core of the measurement optical fiber (6) are welded into a whole, the outer end of the optical cable (8) is arranged outside the shell (201) through an optical cable through hole (206), and the optical cable (8) is fixedly connected with the optical cable through hole (206) through a connector (9); After the outer shell (2), the top cover (4), the elastic sheet combination (5), the measuring optical fiber (6) and the optical cable (8) are assembled, outer heat-insulating coatings (1) with the thickness not less than 2mm are sprayed on the outer surfaces of the outer shell (2) and the top cover (4); The bottom surface in the inner cavity of the shell (201) is fixedly provided with a supporting block A (202) and a supporting block B (204), the distance between the opposite surfaces of the supporting block A (202) and the supporting block B (204) is Lb, and the distance between the opposite surfaces of the supporting block A and the supporting block B is La; The elastic sheet combination (5) comprises an elastic sheet (501) and a pair of optical fiber fixing blocks (502), wherein the length of the elastic sheet (501) is LA, the distance between the opposite surfaces of the pair of optical fiber fixing blocks (502) is LC, the distance between the opposite surfaces of the pair of optical fiber fixing blocks (502) is LB, LA=La, LB < LB, LC > Lg, the two optical fiber fixing blocks (502) are respectively and fixedly connected with two ends of a measuring optical fiber (6) in one-to-one correspondence, the two ends of the elastic sheet (501) are respectively and fixedly connected with a supporting block A (202) and a supporting block B (204) through screws, an optical fiber through hole (205) is formed in the supporting block B (204), and the optical fiber through hole (205) is used for enabling an optical cable (8) to pass through; The joint between the cover plate (401) and the shell (201) is sealed by coating sealant, the joint between the connector (9) and the optical cable via hole (206) is also sealed by coating sealant, and the inner cavity of the shell (201) is sealed.
  2. 2. The fiber grating soil pressure sensor according to claim 1, wherein the bottom surface and the side surface in the inner cavity of the shell (201) are both sprayed with an inner heat preservation coating (3) which is not less than 1 mm.
  3. 3. The fiber bragg grating soil pressure sensor according to claim 2, wherein the outer heat preservation coating (1) and the inner heat preservation coating (3) are made of nano heat preservation materials.
  4. 4. The fiber bragg grating soil pressure sensor according to claim 1, wherein the supporting block A (202) and the supporting block B (204) are respectively provided with a V-shaped groove (503), and two ends of the measuring fiber (6) are arranged in the corresponding V-shaped grooves (503) and are adhered and fixed with the V-shaped grooves (503).
  5. 5. The fiber bragg grating soil pressure sensor according to claim 1, wherein the housing (2) is made of steel, the Brinell hardness is not less than 200N/mm 2 , and the cover plate (401) is made of beryllium bronze or spring steel.
  6. 6. A fiber bragg grating soil pressure monitoring system is characterized by comprising a plurality of fiber bragg grating soil pressure sensors according to any one of claims 1-5, wherein an optical cable (8) in the fiber bragg grating soil pressure sensors is connected with a fiber bragg grating demodulator (11), the fiber bragg grating demodulator (11) is connected with a switch (12), and the switch (12) is connected with a server (13).
  7. 7. The fiber bragg grating soil pressure monitoring system according to claim 6, wherein the installation method comprises the following steps: the method comprises the following steps: s1, foundation leveling Selecting an installation position W of the fiber grating soil pressure sensor, and leveling a foundation at the position; S2, laying cushion layer Paving soil or fine sand with the thickness of T1 on a foundation at the installation position W, wherein the particle diameters of the soil and the fine sand are not more than 10mm, and then compacting and leveling; S3, placing heat-insulating nano aerogel felt Preparing an opening cube by using the heat-insulating nano aerogel felt, reserving a through hole T on the side surface of the opening cube for enabling an optical cable (8) to pass through, and placing the opening cube on a cushion layer; S4, installing the sensor and backfilling Paving soil or fine sand in the opening cube to a thickness of T2, tamping, placing a fiber bragg grating soil pressure sensor on the soil or fine sand in the opening cube, leading out an optical cable (8) from a through hole T on the side surface of the opening cube, sealing a gap between the optical cable (8) and the through hole T by using sealant, continuously paving the soil or fine sand in the opening cube, tamping, covering a cover made of the heat-insulating nano aerogel felt at the opening of the opening cube after the paved soil or fine sand reaches the opening of the opening cube, completely sealing the cover and the opening of the opening cube by using sealant, and backfilling the soil or fine sand until construction parameter requirements are met.
  8. 8. The fiber bragg grating soil pressure monitoring system according to claim 7 is characterized in that in the step S2, T1 is 150 mm-200 mm, and in the step S4, T2 is 20 mm-30 mm.

Description

Fiber bragg grating soil pressure sensor and monitoring system Technical Field The invention belongs to the technical field of soil pressure monitoring, and particularly relates to a fiber bragg grating soil pressure sensor and a fiber bragg grating soil pressure monitoring system comprising the same. Background The soil pressure monitoring technology is widely applied at home and abroad, the technical means is mature, and the static state of the soil pressure monitoring technology can be obtained through the soil pressure sensor on different medium contact surfaces (interfaces) or in soil. Current soil pressure sensors include electronic types and fiber bragg gratings. The electronic soil pressure sensor is mainly divided into a resistance strain gauge type and a vibrating wire type, and the installation mode comprises a horizontal mode, a vertical mode or an inclined mode at any angle. The electronic sensor has the following defects that (1) the electronic sensor needs to be powered, if the electronic sensor is used for a long time, errors such as zero drift and the like appear, the electronic sensor can be possibly interfered by environment electromagnetic interference, and the accuracy of measured data is greatly reduced after a long-time superposition process due to small errors, so that the soil pressure monitoring effect is influenced. (2) The electronic soil pressure sensor is easily affected by the ambient temperature, and the reliability of the monitoring result is affected by the fact that the electronic soil pressure sensor can still monitor obvious numerical changes by only changing the ambient temperature under the condition of no pressure effect through testing. In recent years, the gradual maturation of the optical fiber sensing technology provides a new approach for monitoring the soil pressure, and the optical fiber sensing technology has the advantages of no power supply, high sensitivity, electromagnetic interference resistance and the like, and is rapidly developed in the field of monitoring the state of the rock and soil body. The fiber grating type soil pressure sensor has been widely applied, in order to solve the influence caused by temperature, a temperature measuring grating which is not subjected to acting force is generally added to carry out temperature compensation, but the temperature is increased or reduced due to the nonlinearity of the temperature compensation coefficient, the inconsistency of the compensation coefficient is caused, and the measurement error caused by temperature change still cannot be solved. In order to achieve high-sensitivity and high-precision measurement of soil pressure and reduce or even avoid the influence of ambient temperature, development of a novel soil pressure sensor is needed. Disclosure of Invention The invention aims to solve the technical problem of overcoming the defects of the prior art and providing a fiber bragg grating soil pressure sensor and a fiber bragg grating soil pressure monitoring system comprising the same. The technical scheme of the invention is as follows: an optical fiber grating soil pressure sensor comprises a shell, a top cover, a spring plate combination, a measuring optical fiber and an optical cable, The shell comprises a shell body with a bottom and no top, and an optical cable via hole is formed in the side surface of the shell body; the spring plate combination is fixedly connected with the shell and is arranged in the inner cavity of the shell; the middle part of the measuring optical fiber along the length direction is provided with a grating with the length Lg, and the two ends of the measuring optical fiber are respectively and fixedly connected with the elastic sheet combination; The top cover comprises a cover plate and a force transmission block, wherein the cover plate is fixed at the top of the shell through a screw and is used for sealing an inner cavity of the shell; the transmission optical fiber is wrapped in the optical cable, the transmission optical fiber and the fiber core of the measurement optical fiber are welded into a whole, the outer end of the optical cable is arranged outside the shell through the optical cable via hole, and the optical cable is fixedly connected with the optical cable via hole through the connector; After the shell, the top cover, the spring piece combination, the measuring optical fiber and the optical cable are assembled, outer heat preservation coatings with the thickness not less than 2mm are sprayed on the outer surfaces of the shell and the top cover. Further, the bottom surface and the side surfaces in the inner cavity of the shell are both sprayed with an inner heat-insulating coating which is not less than 1 mm. Further, the materials of the outer heat preservation coating and the inner heat preservation coating are nano heat preservation materials. Further, a supporting block A and a supporting block B are fixedly arranged on the bottom surface in the inner