Strain optical cable surface laying structure for tunnel environment and construction method

Abstract

The invention relates to a strain optical cable surface laying structure for a tunnel environment and a construction method, and belongs to the technical field of optical fiber monitoring. Comprising a plurality of laying units, the laying units are fixed to a concrete layer, and stress adjustable devices are arranged at key joints; strain optical cables are arranged in the laying unit and the stress adjustable device respectively, and the end parts of the adjacent strain optical cables are connected through welding; any laying unit comprises a lower plugging glue layer, a lower adhesive layer is arranged on the lower plugging glue layer, an upper adhesive layer is arranged above the lower adhesive layer, a strain optical cable is arranged between the lower adhesive layer and the upper adhesive layer to form an interlayer strain optical cable, and the interlayer strain optical cable is fixed on a concrete layer through a fixing unit. The optical cable fixing device is convenient, fast, time-saving and labor-saving, the construction cost is reduced, and the construction efficiency is improved; the dependent variable of the target node can be adjusted in batches, and accurate positioning and dependent variable calibration are realized.

Description

Technical Field

[0001] The invention relates to a surface laying structure and construction method of a strain optical cable used in a tunnel environment, and belongs to the technical field of optical fiber monitoring. Background Art

[0002] Due to its suitability for continuous monitoring over long lengths, fiber-optic distributed strain monitoring technology has been widely used in structural health monitoring. This technology, based on Brillouin optical time-domain reflectometry, injects short pulses of light and continuous probe light into the fiber at either end. By measuring the frequency changes of stimulated Brillouin scattered light in the fiber, strain information can be obtained at each point along the fiber's axis. Distributed strain monitoring technology exploits the Brillouin scattering effect of light in the fiber, allowing monitoring points along the entire length of the fiber to monitor structural strain information at corresponding locations. The structural stress is calculated based on relevant information such as the structural elastic modulus. For long-distance structural safety monitoring, distributed strain monitoring based on fiber-optic sensing technology is more economical and cost-effective for the same density of monitoring cross-section points.

[0003] Distributed strain monitoring technology data is divided into three dimensions (time, test distance, and strain value). Compared with traditional point-based two-dimensional data analysis and processing (time and strain value), data processing is more difficult. However, because the data is detailed and has a higher data density, it is conducive to the correlation data analysis of the entire line structure of continuous long-length projects, and can more intuitively reflect the overall structural safety and health status of the project.

[0004] However, due to the harsh construction environment, this type of project has always been a challenge. Currently, the mainstream installation method for distributed strain optical cables in water diversion tunnels is to manually groove the tunnel sidewalls and then seal and bury them with cement. This method requires equipment and specialized tools such as diesel generators, groove pumps, groovers, and impact drills, as well as the transportation of large quantities of cement and waterproofing paint. This is time-consuming and labor-intensive. Furthermore, in the closed tunnel environment, the continuous noise and dust pollution during groove cutting are severe, and the diesel generators produce large amounts of toxic and hazardous exhaust gases, all of which seriously damage worker health. After grooved and buried, the optical cables are fixed at various locations along the line and cannot be moved manually. Each location must be manually disturbed, and each positioning point must be scanned and tested along the entire line, compared to the initial baseline curve, to achieve a rough positioning. This method is time-consuming and labor-intensive, and cannot quantitatively adjust the strain. Due to limited on-site space, long distances, difficulties obtaining water and electricity, and certain limitations on continuous working time, this construction method has numerous drawbacks, resulting in significant volatility in optical cable strain monitoring data, high construction costs, and low efficiency, seriously impacting the overall project effectiveness. Considering both actual customer needs and structural safety, the existing trenching and burying construction method urgently needs improvement. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a surface laying structure and construction method of strain optical cables for use in tunnel environments in response to the above-mentioned existing technologies, which can facilitate and quickly lay strain optical cables, save time and effort, reduce construction costs, and improve construction efficiency; stress-adjustable devices are set at key nodes, which can adjust the strain of target nodes in batches, achieve precise positioning and strain calibration, and only require two full-line scans to accurately locate each key point in batches.

[0006] The technical solution adopted by the present invention to solve the above-mentioned problems is: a surface laying structure for strained optical cables for use in tunnel environments, comprising a plurality of laying units, each of which is fixed to a concrete layer, and stress-adjustable devices are respectively provided at key nodes of the test route in the tunnel; strained optical cables are respectively provided in the laying units and the stress-adjustable devices, and adjacent ends of the strained optical cables are connected by fusion splicing; Each of the laying units comprises a lower sealing adhesive layer, a lower adhesive layer is provided on the lower sealing adhesive layer, an upper adhesive layer is provided above the lower adhesive layer, a strain optical cable is laid between the lower adhesive layer and the upper adhesive layer to form a sandwich strain optical cable, the sandwich strain optical cable is fixed to the concrete layer by a fixing unit, and the upper sealing adhesive layer is coated on the sandwich strain optical cable and the fixing unit; The stress-adjustable device includes a split screw, which is horizontally mounted on a fixed bracket, the strain optical cable is passed through the split screw, and two conical clips are sleeved on the strain optical cable, the conical clips are inserted at both ends of the split screw, and fastening nuts are respectively provided on the outer sides of the conical clips, the fastening nuts are threadedly connected to the split screw, and when the fastening nut is rotated, the fastening nut abuts against the conical clip and pushes the conical clip; the fastening nut abuts against the conical clip and pushes the conical clip to move; two adjusting nuts are screwed on the split screw, the adjusting nuts are arranged on both sides of the fixed bracket and the adjusting nut is arranged on the inner side of the fastening nut, and the two adjusting nuts are rotated to adjust the relative position of the split screw on the fixed bracket, thereby adjusting the strain of the strain optical cable at that location.

[0007] The fixing units respectively include a plurality of riding clamps, and the plurality of riding clamps are evenly distributed along the length direction of the sandwich strain optical cable; the riding clamps are fixed to the concrete layer by nails.

[0008] The distance between adjacent riding cards is 1-2m.

[0009] The split screw includes an upper screw body and a lower screw body. An upper storage groove is opened at the bottom center of the upper screw body, and a lower storage groove is opened at the top center of the lower screw body. The upper screw body and the lower screw body are relatively combined, so that the upper storage groove and the lower storage groove constitute a strain optical cable storage groove.

[0010] Scales are respectively provided on both sides of the split screw.

[0011] A surface installation method for a strain gauge optical cable used in a tunnel environment, the installation method comprising the following steps: Step 1: Clean the surface of the tunnel to be constructed according to the test route in the tunnel, pre-treat the concrete layer, and form a concrete layer; Step 2: Select appropriate waterproof coating and check the coating model, specifications and appearance before construction; Step 3: Dip an appropriate amount of waterproof coating and apply it evenly on the pre-treated concrete layer to form a lower sealing layer; Step 4: After the lower plugging adhesive layer is completely cured, a strong double-sided tape is affixed to the surface of the lower plugging adhesive layer to form a lower adhesive layer; a stress adjustable device installation position is reserved at a key node of the test route, and the reserved stress adjustable device installation position is not affixed with a strong double-sided tape; Step 5: Lay the strain optical cable along the surface of the lower adhesive layer, and stick strong double-sided tape on the surface of the strain optical cable to form an upper adhesive layer. The upper adhesive layer and the lower adhesive layer wrap the strain optical cable in the middle to form a sandwich strain optical cable; Step 6: Fix the sandwich strain optical cable to the concrete layer through the fixing unit; Step 7: Install the stress-adjustable device at the stress-adjustable device installation position, and set the strain optical cable in the stress-adjustable device; fix both ends of the suspended section of the strain optical cable at this location to the concrete layer through fixing units; Step 8: Apply multiple coats of waterproof coating evenly to form an upper sealing adhesive layer, seal and protect the fixed unit and interlayer strain optical cable as a whole, and complete the surface laying of the entire tunnel strain optical cable.

[0012] The width of the cleaning in step 1 is 10-15 cm, and the uneven or damaged surface of the tunnel is pre-treated by applying repair or adding lining materials.

[0013] The waterproof coating in step 2 is a coating containing polyurethane and polyurea components.

[0014] The key nodes of the test route include tunnel stake points, starting points, end points, turning points and strain cable fusion points.

[0015] In the step five, the upper adhesive layer is pressed by a pressure roller so that the upper adhesive layer is tightly adhered to the strain optical cable.

[0016] The adjacent strain optical cable fusion joints are respectively provided with surplus cable racks, and the reserved strain optical cables are wound on the surplus cable racks.

[0017] Compared with the prior art, the advantages of the present invention are: a surface laying structure and construction method of strain optical cable for tunnel environment, 1. Convenient and fast. There is no need to groove, drill and seal the tunnel with cement. There is no need to equip special equipment such as generators, impact drills and slotting machines. Only tools such as nail guns and brushes are needed. No electricity, water or gas supply is required. Protective equipment is required during operation (the nail gun operation is noisy and earplugs are required). It saves time and effort, reduces construction costs and improves construction efficiency.

[0018] 2. Stress adjustable devices are installed at the key nodes of the test route in the tunnel, which can adjust the strain of the target nodes in batches, conveniently achieving the purpose of accurate positioning and strain calibration. Only two full-line scans are required (the first full-line benchmark scan is performed after installation, and the second comparative scan is performed after batch adjustment) to accurately locate each key point in batches. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of a surface-mounted structure for a strained optical cable used in a tunnel environment according to an embodiment of the present invention; Figure 2 The exploded diagram of the stress-adjustable device; Figure 3 is a schematic diagram of a stress-adjustable device; Figure 4 This is a schematic diagram of the ring wiring of the strain optical cable in the tunnel; In the figure, 1 is a concrete layer, 2 is a lower sealing rubber layer, 3 is a lower adhesive layer, 4 is a strain optical cable, 5 is an upper adhesive layer, 6 is a saddle card, 7 is an upper sealing rubber layer, 8 is an adjusting nut, 9 is a split screw, 10 is a fixing bracket, 11 is a tapered clip, 12 is a fastening nut, and 13 is a ruler. DETAILED DESCRIPTION

[0020] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0021] In this embodiment, a strain optical cable surface laying structure for use in a tunnel environment includes a plurality of laying units, which are fixed to a concrete layer 1; strain optical cables 4 are respectively provided in the laying units, and the ends of adjacent strain optical cables 4 are connected by fusion splicing. When the tunnel structure is affected by external forces and undergoes deformation, cracking, and other changes, the optical fibers in the strain optical cables 4 in the laying units are simultaneously driven to undergo stretching, compression, and other changes, thereby causing the frequency of stimulated Brillouin scattered light to change accordingly. By analyzing the frequency change value, the strain data at each location is converted, thereby achieving the purpose of monitoring the changes in the tunnel structure. Figure 4As shown, the test route in a tunnel generally consists of circumferential and longitudinal lines and is usually not a straight line. After installation, the length must be located and recorded for subsequent operation and maintenance. To achieve this, stress-adjustable devices are installed at key nodes in the test route, including tunnel marker points, starting points, end points, turning points, and strain cable splice points. Each stress-adjustable device houses a strain cable 4, which is quantitatively stretched. By comparing the strain data before and after stretching, the line length can be precisely located and the strain amount calibrated.

[0022] like Figure 1 As shown, any laying unit includes a lower sealing rubber layer 2, a lower adhesive layer 3 is provided on the lower sealing rubber layer 2, an upper adhesive layer 5 is provided above the lower adhesive layer 3, a strain optical cable 4 is laid between the lower adhesive layer 3 and the upper adhesive layer 5 to form a sandwich strain optical cable, and the sandwich strain optical cable is fixed to the concrete layer 1 through a fixing unit, and an upper sealing rubber layer 7 is provided on both the sandwich strain optical cable and the fixing unit.

[0023] The fixing unit includes multiple saddle clips 6, evenly spaced along the length of the interlayer strain-resistant optical cable, with spacing of 1-2 meters between adjacent saddle clips 6. Nail guns are used to secure the saddle clips to the concrete layer 1. Nail guns are noisy during operation, so wear earplugs when operating.

[0024] like Figure 2 、 3 As shown, the stress-adjustable device includes a split screw 9, which is horizontally mounted on a fixed bracket 10, through which the strain cable is passed. Two conical clips 11 are sleeved on the strain cable 4 and inserted at both ends of the split screw 9. Fastening nuts 12 are provided on the outer sides of the conical clips 11 and are threadedly connected to the split screw 9. Turning the fastening nut 12 causes the fastening nut 12 to abut against the conical clip 11 and push the clip forward, facilitating adjustment of the clamping force on the strain cable and securing the strain cable within the split screw. Two adjusting nuts 8 are screwed onto the split screw. The adjusting nuts 8 are arranged on both sides of the fixed bracket and on the inner side of the fastening nut 12. When the two adjusting nuts are rotated simultaneously in the same direction, the relative position of the split screw on the fixed bracket is adjusted. The split screw drives the strained optical cable at that location to stretch in the opposite direction of the movement of the nut, causing the optical fiber in the strained optical cable to produce strain changes, thereby adjusting the strain amount of the strained optical cable at that location.

[0025] The split screw 9 includes an upper screw body and a lower screw body. An upper storage groove that runs through the front and back is opened at the center of the bottom of the upper screw body, and a lower storage groove that runs through the front and back is opened at the center of the top of the lower screw body. The upper screw body and the lower screw body are relatively combined, so that the upper storage groove and the lower storage groove constitute a strain optical cable storage groove, and the strain optical cable is arranged in the strain storage groove.

[0026] Horizontally positioned scales 13 are installed on either side of the split screw 9, allowing the strain adjustment to be precisely set using these two scales. After initial strain values ​​are set for all key nodes, a full-line scan is performed using a Brillouin strain temperature analyzer (BOFDA). The data curve is saved as a baseline, and then the strain at each key node is uniformly adjusted according to the established strain adjustment value, followed by a second full-line scan. By comparing the strain monitoring curves from the two tests, key nodes along the entire optical cable can be quickly and accurately located and their initial strain values ​​calibrated.

[0027] Taking into account the need for strain optical cables to be tightly integrated with the surface of the structure to be monitored, but the tunnel is in a humid environment all year round and is subject to water impact erosion, it is necessary to use waterproof, corrosion-resistant, and long-term stable performance materials for construction. The fixing method of this application is a combination of gun nails and saddle cards. This fixing method does not require water supply, power supply, and special construction equipment, which reduces labor intensity, is convenient and quick to lay, and has stable and reliable construction quality. In addition, the lower sealing adhesive layer solves the problem of sanding, cracking, and water seepage in the concrete layer. The outer sealing layer isolates the influence of external moisture on the internal upper adhesive layer, strain optical cable, and lower adhesive layer, thereby extending the service life of the overall structure.

[0028] A surface installation method for strain relief optical cables for use in tunnel environments comprises the following steps: Step 1: Clean the tunnel surface to be constructed, following the test route in the tunnel. Clean a 10-15cm width to form a concrete layer. If the test route surface is uneven or damaged, pre-treat it by applying patching material or adding cushioning material.

[0029] Step 2: Select suitable waterproof coating (special waterproof coating containing polyurethane, polyurea and other components can be selected as required). Check the coating model, specifications and appearance before construction. If multi-component coating is used, each component must be mixed in advance according to the required proportions.

[0030] Step 3: Use a brush to apply an appropriate amount of waterproof coating evenly to the pre-treated concrete layer. Apply the waterproof coating twice, 12 hours after the first coat. Allow the second coat to fully cure 24 hours after the second coat, forming a lower sealant layer. This lower sealant layer prevents sanding, cracking, and water seepage from the concrete layer, creating a smooth surface for the next construction step.

[0031] Step 4: After the lower sealing adhesive layer is completely cured, apply strong double-sided tape to the surface of the lower sealing adhesive layer to form a lower adhesive layer. Reserve a 2m-long section of space for the stress-adjustable device at key nodes along the test route. Do not apply strong double-sided tape to the reserved stress-adjustable device installation area (i.e., no lower adhesive layer).

[0032] Step 5: Lay the strain-sensitive optical cable along the surface of the lower adhesive layer. Apply strong double-sided tape wider than the lower adhesive layer to the surface of the strain-sensitive optical cable to form an upper adhesive layer. The upper and lower adhesive layers wrap the strain-sensitive optical cable in the middle, forming a sandwich strain-sensitive optical cable. Use a pressure roller to press the gap between the upper adhesive layer and the strain-sensitive optical cable to ensure a tight bond, thus forming a sandwich strain-sensitive optical cable.

[0033] Step 6: Use nails and saddle clips to permanently fix the sandwich strain relief cable to the concrete layer at intervals of 1 to 2 meters.

[0034] Step 7: Install the strain gauge at the strain gauge mounting location. The strain gauge cable is threaded through the strain gauge. The two ends of the suspended section of the strain gauge cable are secured to the concrete layer using saddle clips and rivets. The strain gauge adjusts the strain gauge cable's tension in a fixed manner. Set the adjustment nut to a uniform scale position according to design requirements.

[0035] Step 8: Apply two coats of waterproof coating evenly on the outermost layer according to the method in step 3 to form an upper sealing glue layer, and seal and protect the fixed unit and the interlayer strain optical cable as a whole, thus completing the surface laying work of the entire tunnel strain optical cable.

[0036] A tunnel is typically several to several dozen kilometers long, and a reel of strain relief cable can be 2-3 kilometers long. Several reels of strain relief cable must be spliced ​​together to monitor the entire tunnel. At the splice points, a spare cable rack should be used to reserve strain relief cable for maintenance and securely tied.

[0037] This application is convenient and quick. There is no need to groove, drill holes, or seal the tunnel with cement. There is no need for special equipment such as generators, impact drills, and groovers. Only tools such as nail guns and brushes are needed. No electricity, water, or gas is required. Protective equipment is required during operation (the nail gun operation is noisy and earplugs are required).

[0038] A stress-adjustable device is set at the key nodes of the test route in the tunnel of this application, which can adjust the strain of the target nodes in batches, conveniently achieving the purpose of precise positioning and strain calibration. Only two full-line scans are required (the first full-line benchmark scan is performed after installation, and the second comparative scan is performed after batch adjustment) to accurately locate each key point in batches.

[0039] This application significantly reduces the total amount of materials used, primarily common materials, eliminating the need for specialized customization and procurement. This approach is relatively inexpensive, safe, environmentally friendly, and offers stable performance that meets long-term use requirements. Calculations show that this method, compared to existing trenching methods, has no adverse effects on the tunnel surface, improves construction efficiency by 2-3 times, and reduces construction costs to approximately one-third of the original method.

[0040] In addition to the above embodiments, the present invention also includes other implementation methods. Any technical solutions formed by equivalent transformation or equivalent replacement should fall within the scope of protection of the claims of the present invention.

Claims

1. A strain gauge optical cable surface laying structure for use in a tunnel environment, characterized by: The method comprises a plurality of laying units, wherein the plurality of laying units are fixed to a concrete layer, and stress-adjustable devices are respectively provided at key nodes of the test route in the tunnel; strain optical cables are respectively provided in the laying units and the stress-adjustable devices, and adjacent ends of the strain optical cables are connected by fusion splicing; Each of the laying units comprises a lower sealing adhesive layer, a lower adhesive layer is provided on the lower sealing adhesive layer, an upper adhesive layer is provided above the lower adhesive layer, a strain optical cable is laid between the lower adhesive layer and the upper adhesive layer to form a sandwich strain optical cable, the sandwich strain optical cable is fixed to the concrete layer by a fixing unit, and the upper sealing adhesive layer is coated on the sandwich strain optical cable and the fixing unit; The stress-adjustable device includes a split screw, which is horizontally mounted on a fixed bracket, the strain optical cable is passed through the split screw, and two conical clips are sleeved on the strain optical cable, the conical clips are inserted at both ends of the split screw, and fastening nuts are respectively provided on the outer sides of the conical clips, the fastening nuts are threadedly connected to the split screw, and the fastening nuts are rotated so that the fastening nuts abut against the conical clips and push the conical clips; the fastening nuts abut against the conical clips and push the conical clips to move; two adjusting nuts are screwed on the split screw, the adjusting nuts are arranged on both sides of the fixed bracket and the adjusting nuts are arranged on the inner side of the fastening nuts, and the two adjusting nuts are rotated to adjust the relative position of the split screw on the fixed bracket, thereby adjusting the strain of the strain optical cable at that location; Scales are respectively provided on both sides of the split screw.

2. The surface-mounted structure for strain-sensitive optical cables used in tunnel environments according to claim 1, characterized in that: The fixing units respectively include a plurality of riding clamps, and the plurality of riding clamps are evenly distributed along the length direction of the sandwich strain optical cable; the riding clamps are fixed to the concrete layer by nails.

3. The surface-mounted structure for strain-sensitive optical cables used in tunnel environments according to claim 2, characterized in that: The distance between adjacent riding cards is 1-2m.

4. The surface-mounted structure for strain-sensitive optical cables used in tunnel environments according to claim 1, characterized in that: The split screw includes an upper screw body and a lower screw body. An upper storage groove is opened at the bottom center of the upper screw body, and a lower storage groove is opened at the top center of the lower screw body. The upper screw body and the lower screw body are relatively combined, so that the upper storage groove and the lower storage groove constitute a strain optical cable storage groove.

5. A method for surface installation of a strain gauge optical cable for use in a tunnel environment according to any one of claims 1 to 4, characterized in that: The installation method comprises the following steps: Step 1: Clean the surface of the tunnel to be constructed according to the test route in the tunnel, pre-treat the concrete layer, and form a concrete layer; Step 2: Select appropriate waterproof coating and check the coating model, specifications and appearance before construction; Step 3: Dip an appropriate amount of waterproof coating and apply it evenly on the pre-treated concrete layer to form a lower sealing layer; Step 4: After the lower plugging adhesive layer is completely cured, a strong double-sided tape is affixed to the surface of the lower plugging adhesive layer to form a lower adhesive layer; a stress adjustable device installation position is reserved at a key node of the test route, and the reserved stress adjustable device installation position is not affixed with a strong double-sided tape; Step 5: Lay the strain optical cable along the surface of the lower adhesive layer, and stick strong double-sided tape on the surface of the strain optical cable to form an upper adhesive layer. The upper adhesive layer and the lower adhesive layer wrap the strain optical cable in the middle to form a sandwich strain optical cable; Step 6: Fix the sandwich strain optical cable to the concrete layer through the fixing unit; Step 7: Install the stress-adjustable device at the stress-adjustable device installation position, and set the strain optical cable in the stress-adjustable device; The two ends of the suspended section of the strain optical cable are fixed to the concrete layer through fixing units respectively; Step 8: Apply multiple coats of waterproof coating evenly to form an upper sealing adhesive layer, seal and protect the fixed unit and interlayer strain optical cable as a whole, and complete the surface laying of the entire tunnel strain optical cable.

6. The surface installation method of a strain gauge optical cable for use in a tunnel environment according to claim 5, characterized in that: The width of the cleaning in step 1 is 10-15 cm, and the uneven or damaged surface of the tunnel is pre-treated by applying repair or adding lining materials.

7. The surface installation method of a strain gauge optical cable for use in a tunnel environment according to claim 5, characterized in that: The waterproof coating in step 2 is a coating containing polyurethane and polyurea components.

8. The surface installation method of a strain gauge optical cable for use in a tunnel environment according to claim 5, characterized in that: The key nodes of the test route include tunnel stake points, starting points, end points, turning points and strain cable fusion points.

9. The surface installation method of a strain gauge optical cable for use in a tunnel environment according to claim 5, characterized in that: In the step five, the upper adhesive layer is pressed by a pressure roller so that the upper adhesive layer is tightly adhered to the strain optical cable.

10. The surface installation method of a strain gauge optical cable for use in a tunnel environment according to claim 5, characterized in that: The adjacent strain optical cable fusion joints are respectively provided with surplus cable racks, and the reserved strain optical cables are wound on the surplus cable racks.

Images