Distributed strain sensing optical cable suitable for being directly buried and installed in rock-soil body

Abstract

The invention relates to a distributed strain sensing optical cable suitable for rock-soil body direct burial installation, the distributed strain sensing optical cable comprises a strain sensing optical unit, a first protection unit and a second protection unit, the strain sensing optical unit comprises a sensing optical fiber, a tightening sleeve and a spiral armor tube, a plurality of continuous bonding points are arranged between the tightening sleeve and the spiral armor tube, and the first protection unit is connected with the second protection unit. The sensing optical fiber is provided with a sensing grating at a part between two adjacent bonding points, the first protection unit is sleeved outside the spiral armor tube, and the second protection unit is sleeved outside the first protection unit; when strain is generated outside the optical cable, the strain drives the sensing optical fiber to be transmitted to the optical gratings from outside to inside through the spiral armored tube, so that the optical cable has the strain measurement capability, the detection range of the plurality of optical gratings is large, the spiral armored tube has relatively high anti-pressure capability, and meanwhile, the strain measurement sensitivity can be improved; the first protection unit and the second protection unit can effectively protect the strain sensing optical unit, so that the optical cable has good mechanical strength.

Description

Technical Field

[0001] The invention relates to the technical field of distributed strain sensing, and in particular to a distributed strain sensing optical cable suitable for direct burial installation in rock and soil bodies. Background Art

[0002] Monitoring the deformation and slippage of rock and soil masses not only helps to improve the safety and reliability of projects, but is also an important means of preventing earthquake disasters and protecting the ecological environment. It is of great significance in engineering, safety and environmental management.

[0003] Most existing rock and soil monitoring uses single-point sensors, which require strong professionalism in installation and maintenance, and are difficult to carry out under certain geological conditions. At the same time, the detection range of single-point sensors is small, and the value of the rock and soil data they can provide is limited. In the application process of rock and soil health detection, the strain sensor cable itself needs to have a certain mechanical strength to protect the sensor cable from damage during installation and long-term use. However, increasing the mechanical strength of the cable will reduce the sensitivity of rock and soil strain measurement. Summary of the invention

[0004] In view of this, it is necessary to provide a distributed strain sensing optical cable suitable for direct burial installation in rock and soil, so as to solve the problems of limited detection range of existing single-point sensors and difficulty in ensuring that the strain sensor optical cable has both good mechanical strength and high sensitivity.

[0005] The present invention provides a distributed strain sensing optical cable suitable for direct burial installation in rock and soil bodies, comprising a strain sensing optical unit, a first protection unit and a second protection unit. The strain sensing optical unit comprises a sensing optical fiber, a tight sleeve and a spiral armor tube which are sequentially sleeved from the inside to the outside. A plurality of bonding points arranged along the length direction of the sensing optical fiber are provided between the tight sleeve and the spiral armor tube. A grating is formed on the sensing optical fiber at a position between two adjacent bonding points. The first protection unit is sleeved outside the spiral armor tube, and the second protection unit is sleeved outside the first protection unit.

[0006] Furthermore, the plurality of bonding points are arranged at equal distances along the length direction of the sensing optical fiber.

[0007] Furthermore, the tightening sleeve and the spiral armor tube are bonded together.

[0008] Furthermore, the first protection unit includes a first protective sleeve sleeved on the spiral armor tube.

[0009] Furthermore, the first protection unit further includes a first reinforcement member, and the first reinforcement member is axially disposed through the first protective sleeve.

[0010] Furthermore, the first reinforcement member is a phosphating steel wire, and the number of the first reinforcement members is two, and the two first reinforcement members are arranged in parallel and opposite to each other on both sides of the sensing optical fiber.

[0011] Furthermore, the second protection unit includes a second protective cover sleeved on the first protection unit.

[0012] Furthermore, the second protection unit further includes a second reinforcement member, and the second reinforcement member is arranged axially through the second protective sleeve.

[0013] Furthermore, the second reinforcement member is a phosphating steel wire, and the number of the second reinforcement members is two, and the two second reinforcement members are arranged in parallel and opposite to each other on both sides of the sensing optical fiber.

[0014] Furthermore, the second protection unit further includes a longitudinal steel belt, which is arranged between the first protection unit and the second protective cover, and the outer wall and the inner wall of the longitudinal steel belt are both formed with embossing.

[0015] Compared with the prior art, the tight bundle tube layer provides protection for the sensing optical fiber. When strain occurs in any two adjacent bonding points, the strain is transmitted from the outside to the inside through the spiral armor tube driving the sensing optical fiber to the grating, so that the optical cable has the ability to measure strain. Multiple gratings can be arranged at different positions according to actual needs, and the detection range is large. The above-mentioned spiral armor tube has strong compressive resistance. At the same time, due to its spiral structure, it can be stretched and can be restored within a certain deformation range. Both positive strain and negative strain can be measured. On the above basis, the first protection unit and the second protection unit can effectively protect the strain sensing optical unit, so that the optical cable has good mechanical strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of the overall structure of a distributed strain sensing optical cable suitable for direct burial installation in rock and soil provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0017] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0018] like Figure 1As shown, the present invention provides a distributed strain sensing optical cable suitable for direct burial installation in rock and soil, comprising a strain sensing optical unit 100, a first protection unit 200 and a second protection unit 300. The strain sensing optical unit 100 comprises a sensing optical fiber 110, a tight sleeve 120 and a spiral armor tube 130 which are sequentially sleeved from the inside to the outside. There are multiple bonding points arranged along the length direction of the sensing optical fiber 110 between the tight sleeve 120 and the spiral armor tube 130. The sensing optical fiber 110 has gratings at the parts between two adjacent bonding points. The first protection unit 200 is sleeved outside the spiral armor tube 130, and the second protection unit 300 is sleeved outside the first protection unit 200.

[0019] During implementation, the tight bundle tube layer provides protection for the sensing optical fiber 110. When strain occurs in any two adjacent bonding points, the spiral armor tube 130 drives the sensing optical fiber 110 to be transmitted to the grating, so that the optical cable has the ability to measure strain. Multiple gratings can be arranged at different positions according to actual needs, and the detection range is large. The spiral armor tube 130 has strong compressive resistance. At the same time, due to its spiral structure, it can be stretched and restored within a certain deformation range, which can greatly improve the sensitivity of strain measurement. On the basis of the above, the first protection unit 200 and the second protection unit 300 can effectively protect the strain sensing optical unit 100, so that the optical cable has good mechanical strength.

[0020] The strain sensing optical unit 100 in this embodiment includes a sensing optical fiber 110, a tightening sleeve 120 and a spiral armor tube 130 which are sequentially arranged from the inside to the outside. There are multiple bonding points arranged along the length direction of the sensing optical fiber 110 between the tightening sleeve 120 and the spiral armor tube 130, and the sensing optical fiber 110 is formed with a grating at the position between two adjacent bonding points.

[0021] Among them, the sensing optical fiber 110 will generate strain when subjected to external force. Through distributed optical fiber demodulation technology, its measurement range is 3% strain, and its geometric dimension diameter can be selected as 150~250μm, so that the deformation and slip of the rock and soil body can be distributedly measured according to the feedback of the above strain.

[0022] The diameter of the tightening sleeve 120 can be selected to be 0.7-1.5 mm, and the material can be selected from PVC, hytrel, PA, etc.

[0023] The spiral armor tube 130 can be made of high-quality stainless steel material, which has strong compressive resistance. At the same time, due to its spiral structure, it can be stretched and can be restored within a certain deformation range. The size of the spiral armor tube 130 is generally 1.2~5.0mm.

[0024] It can be understood that multiple bonding points are arranged at equal distances along the length direction of the sensing optical fiber 110, and the tight sleeve 120 is bonded to the spiral armor tube 130. Specifically, the spiral armor tube 130 and the tight sleeve are fixed with a high-strength adhesive 340 at intervals L, and there is a grating between the two fixed points. When strain occurs within any interval L, the spiral armor tube 130 drives the sensing optical fiber 110 to be transmitted to the grating, so that the optical cable has the ability to measure strain. Compared with other structures, the structure of the spiral armor tube 130 can greatly improve the sensitivity of strain measurement.

[0025] The first protection unit 200 in this embodiment includes a first protective sleeve 210 sleeved on the spiral armor tube 130. The first protective sleeve 210 is made of high-density polyethylene material, which is acid-resistant, alkali-resistant, and organic solvent-resistant, and has high surface hardness and tensile strength.

[0026] To further improve the mechanical strength of the optical cable, in one embodiment, the first protection unit 200 further includes a first reinforcement member 220, which is axially disposed through the first protective sleeve 210. The first reinforcement member 220 is a phosphating steel wire, and the number of the first reinforcement members 220 is two, which are parallel and oppositely disposed on both sides of the sensing optical fiber 110, and are the main guarantee of the tensile strength of the optical cable.

[0027] The second protection unit 300 in this embodiment includes a second protection cover 310 sleeved on the first protection unit 200. The second protection cover 310 is made of high-density polyethylene material, which is acid-resistant, alkali-resistant, and organic solvent-resistant, and has high surface hardness and tensile strength.

[0028] To further improve the mechanical strength of the optical cable, in one embodiment, the second protective unit 300 also includes a second reinforcement member 320, which is axially inserted through the second protective cover 310, wherein the second reinforcement member 320 is a phosphating steel wire, and the number of the second reinforcement members 320 is two, and the two second reinforcement members 320 are parallel and relatively arranged on both sides of the sensing optical fiber 110, which is the main guarantee for the tensile strength of the optical cable.

[0029] The second protection unit 300 in this embodiment further includes a longitudinal steel belt 330, which is disposed between the first protection unit 200 and the second protective cover 310, and the outer wall and the inner wall of the longitudinal steel belt 330 are both formed with embossing. By providing the longitudinal steel belt 330, not only the tensile strength and compressive strength of the optical cable can be further improved, but also, since the longitudinal steel belt 330 is embossed during the production of the optical cable, the relative slip between the first protective cover 210 and the second protective cover 310 can be reduced.

[0030] The first protective cover 210 and the longitudinal steel belt 330 can be connected by a hot-melt adhesive 340. Specifically, during the production of the optical cable, the adhesive 340 is heated at a high temperature to a molten flow state at a temperature above 200°C, and has a high bonding strength after being cooled and solidified.

[0031] The first protective cover 210 and the second protective cover 310 are firmly connected together. On the one hand, the optical cable is provided with mechanical strength that meets the requirements of direct burial application; on the other hand, the strain is transferred from the outside to the inside to the strain sensing unit through structural design and the addition of high-strength adhesive 340.

[0032] Compared with the prior art: the tight bundle tube layer provides protection for the sensing optical fiber 110. When strain occurs in any two adjacent bonding points, the spiral armor tube 130 drives the sensing optical fiber 110 to be transmitted to the grating, so that the optical cable has the ability to measure strain. Multiple gratings can be arranged at different positions according to actual needs, and the detection range is large. The spiral armor tube 130 has strong compressive resistance. At the same time, due to its spiral structure, it can be stretched and compressed, and can be restored within a certain deformation range. Both positive strain and negative strain can be measured. On the above basis, the first protection unit 200 and the second protection unit 300 can effectively protect the strain sensing optical unit 100, so that the optical cable has good mechanical strength.

[0033] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A distributed strain sensing optical cable suitable for direct burial installation in rock and soil, characterized in that: include: A strain sensing optical unit, comprising a sensing optical fiber, a tight sleeve and a spiral armor tube which are sequentially sleeved from the inside to the outside, wherein a plurality of bonding points arranged along the length direction of the sensing optical fiber are provided between the tight sleeve and the spiral armor tube, and the sensing optical fiber has a grating at a position between two adjacent bonding points; A first protection unit, which is sleeved outside the spiral armor tube; The second protection unit is sleeved outside the first protection unit.

2. The distributed strain sensing optical cable suitable for direct burial installation in rock and soil according to claim 1, characterized in that: The plurality of bonding points are arranged at equal distances along the length direction of the sensing optical fiber.

3. The distributed strain sensing optical cable suitable for direct burial installation in rock and soil according to claim 1, characterized in that: The tightening sleeve and the spiral armor tube are bonded together.

4. The distributed strain sensing optical cable suitable for direct burial installation in rock and soil according to claim 1, characterized in that: The first protection unit includes a first protective sleeve sleeved on the spiral armor tube.

5. The distributed strain sensing optical cable suitable for direct burial installation in rock and soil according to claim 4, characterized in that: The first protection unit further includes a first reinforcement member, and the first reinforcement member is axially disposed through the first protective sleeve.

6. The distributed strain sensing optical cable suitable for direct burial installation in rock and soil according to claim 5, characterized in that: The first reinforcement member is a phosphating steel wire, and there are two first reinforcement members, which are arranged in parallel and opposite to each other on both sides of the sensing optical fiber.

7. The distributed strain sensing optical cable suitable for direct burial installation in rock and soil according to claim 1, characterized in that: The second protection unit includes a second protective cover sleeved on the first protection unit.

8. The distributed strain sensing optical cable suitable for direct burial installation in rock and soil according to claim 7, characterized in that: The second protection unit further includes a second reinforcement member, and the second reinforcement member is axially disposed through the second protective sleeve.

9. The distributed strain sensing optical cable suitable for direct burial installation in rock and soil according to claim 8, characterized in that: The second reinforcement member is a phosphating steel wire, and there are two second reinforcement members, which are arranged in parallel and opposite to each other on both sides of the sensing optical fiber.

10. The distributed strain sensing optical cable suitable for direct burial installation in rock and soil according to claim 9, characterized in that: The second protection unit further includes a longitudinal steel belt, which is arranged between the first protection unit and the second protection cover, and the outer wall and the inner wall of the longitudinal steel belt are both formed with embossing.

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