Method for laying distributed monitoring optical cable for tunnel primary support

Abstract

The application provides a tunnel primary support distributed monitoring optical cable laying method, which sequentially comprises the steps of tunnel support structure erection, optical cable bobbin placement, optical cable initial wiring, shotcrete and optical cable circulation wiring. The optical cable placed on the optical cable bobbin passes through the support structure to form a monitoring section, a free section and a turning section, and the monitoring section is bound on the support structure. An auxiliary sleeve is sleeved on the free section. A protective sleeve is sleeved on the turning section; with the excavation of the next tunnel section, the turning section is pulled forward, a new auxiliary sleeve is sleeved on the free section at the new support structure, the previous protective sleeve is removed and then sleeved on the newly formed turning section, and the wiring structure erection and shotcrete steps are repeated. The tunnel primary support distributed monitoring optical cable laying method provided by the application can realize the laying of the distributed optical cable in the tunnel primary support process, effectively improve the survival rate of the distributed optical cable laid in the primary support, and has high practicability.

Description

Technical Field

[0001] This invention belongs to the field of tunnel monitoring technology, specifically relating to a method for laying distributed monitoring optical cables for tunnel initial support. Background Technology

[0002] Initial support (primary support) is a safety protection measure during tunnel excavation and serves as the permanent load-bearing structure of the tunnel. It not only controls the appropriate release and deformation of surrounding rock stress but also provides strong protection for the tunnel's structural and construction safety. Therefore, to understand and monitor the stress state and deformation of the tunnel's initial support structure, traditional point sensors, such as resistance and vibrating wire strain gauges, stress gauges, thermometers, and distributed monitoring optical cables, are commonly used to monitor the stress, strain, and temperature of the tunnel's initial support structure, providing crucial information for tunnel construction safety monitoring and early warning. Among these, distributed optical fiber sensing technology offers advantages such as distributed measurement, long lifespan, resistance to electromagnetic interference, fast dynamic response, high sensitivity and testing accuracy, strong durability, and the ability to achieve long-distance, full-domain distributed monitoring, making it particularly suitable for real-time monitoring of long tunnel structures throughout their entire lifespan.

[0003] In existing technologies, the initial support section of drill-and-blast tunnels involves complex procedures and harsh environments. Blasting and muck removal processes are performed alternately in short intervals, making the deployment of distributed monitoring optical cables inconvenient. Furthermore, the cables need to be gradually advanced as the tunnel is excavated, requiring the cable reel to remain at the tunnel face. During the excavation of later tunnel sections, the cables to be deployed are highly susceptible to damage. Therefore, distributed optical cable deployment is primarily used for secondary lining monitoring, with few successful applications in initial support structures. Summary of the Invention

[0004] This invention provides a method for deploying distributed monitoring optical cables for tunnel initial support, aiming to solve the problem of poor practicality of existing monitoring optical cable deployment methods during tunnel construction.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: to provide a method for deploying distributed monitoring optical cables for tunnel initial support, comprising the following steps:

[0006] The tunnel support structure is constructed by continuously installing multiple steel arch frames in the excavated tunnel, and installing steel mesh around the outer edge formed by each steel arch frame; the steel arch frames and the steel mesh form a support structure.

[0007] Place the optical cable reel in the tunnel after the initial support construction is completed;

[0008] For initial fiber optic cable routing, the fiber optic cable is pulled out from the spool and its end is fixed in the tunnel where the initial support construction has been completed. Then, the fiber optic cable is pulled through the support structure from behind the reinforcing mesh, forming a monitoring section, a free section, and a turning section. The monitoring section is then tied to the reinforcing mesh. An auxiliary sleeve is installed and fitted onto the free section. A protective sleeve is installed at the end of the support structure near the tunnel face and fitted onto the turning section.

[0009] Shotcrete: Shotcrete is applied to the support structure.

[0010] The optical cable is laid in a loop. As the next section of the tunnel is excavated, the tunnel support structure construction steps are repeated. The protective sleeve is removed, and the optical cable in the free section and the optical cable spool is pulled through the turning section, so that the optical cable passes through the newly constructed support structure to form a new monitoring section, free section and turning section. Then the newly formed monitoring section is tied to the steel mesh, the new auxiliary sleeve is put on the newly formed free section, and the removed protective sleeve is put on the newly formed turning section. Then the shotcrete step is repeated.

[0011] In one possible implementation, each of the auxiliary sleeves is provided with a first elongated notch that extends through the lumen of the auxiliary sleeve.

[0012] In one possible implementation, the auxiliary sleeve is made of PVC.

[0013] In one possible implementation, each of the auxiliary sleeves is fitted onto the optical cable and then connected to the steel mesh. After each auxiliary sleeve is fitted onto the optical cable, the first long notch is sealed with tape. Adjacent auxiliary sleeves are connected by a connector with an opening.

[0014] In one possible implementation, the protective sleeve is a U-shaped tube, and the U-shaped tube has a second elongated notch that penetrates the cavity of the U-shaped tube, the second elongated notch being located on the concave side of the U-shaped tube.

[0015] In one possible implementation, the U-shaped tube is made of rubber.

[0016] In one possible implementation, after the protective sleeve is installed on the optical cable, one end of the protective sleeve is fitted onto the corresponding end of the auxiliary sleeve.

[0017] In one possible implementation, both ends of the protective sleeve are tied and fixed to the reinforcing mesh.

[0018] In one possible implementation, the initial wiring step of the optical cable also employs guide tubes, with two guide tubes arranged side by side, one end of each guide tube extending into the back of the steel mesh.

[0019] In the initial wiring step of the optical cable, the end of the optical cable is inserted into the back of the steel mesh through one of the guide tubes, and then exits through the other guide tube after the direction is reversed.

[0020] In one possible implementation, the guide tube is made of rubber.

[0021] In this implementation, steel mesh is installed on each steel arch, and the monitoring section of the optical cable is fixed to the steel mesh. The steel mesh sensitively senses changes in the tunnel, and the deformation of the steel mesh ensures that the optical cable can monitor stress, strain, and temperature changes in the area of ​​the steel mesh. Because the steel mesh has a large sensing range, the monitoring range of the optical cable is improved. Through the initial and cyclic laying steps of the optical cable, the optical cable in the auxiliary sleeve can be flexibly pulled to keep the cable spool away from the tunnel face. At the same time, protective sleeves are set on the turning section to prevent the optical cable from being damaged by blasting during the subsequent tunnel excavation. This effectively protects the optical cable, improves the survival rate of distributed optical cables in the initial support, and is highly practical. Attached Figure Description

[0022] Figure 1 A schematic diagram of the process structure of the distributed monitoring optical cable deployment method for tunnel initial support provided in an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the deployment structure involved in the method for deploying distributed monitoring optical cables for tunnel initial support provided in an embodiment of the present invention.

[0024] Figure 3 A schematic diagram of the auxiliary sleeve structure (with connector) for the method of laying distributed monitoring optical cables for tunnel initial support provided in an embodiment of the present invention;

[0025] Figure 4 A schematic diagram of the U-shaped tube structure for the distributed monitoring optical cable laying method for tunnel initial support provided in an embodiment of the present invention;

[0026] Figure 5 A detailed flowchart of the method for deploying distributed monitoring optical cables for tunnel initial support provided in this embodiment of the invention;

[0027] Explanation of reference numerals in the attached figures:

[0028] 10. Steel arch frame; 20. Steel mesh; 30. Optical cable spool; 31. Optical cable; 40. Auxiliary sleeve; 41. First long notch; 42. Joint; 50. Protective sleeve; 51. Second long notch; 52. Iron wire; 60. Guide tube. Detailed Implementation

[0029] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0030] Please refer to the following: Figure 1 , Figure 2 and Figure 5 The method for deploying distributed monitoring optical cables for tunnel initial support provided by the present invention will now be described. The method for deploying distributed monitoring optical cables for tunnel initial support includes the following steps:

[0031] S100: Tunnel support structure construction, in which multiple steel arch frames 10 are continuously installed in the excavated tunnel, and steel mesh 20 is installed around the outer edge formed by each steel arch frame 10. Each steel arch frame 10 and the steel mesh 20 form a support structure.

[0032] S200: Place the optical cable reel, and set the optical cable reel 31 in the tunnel after the initial support construction is completed.

[0033] S300: Initial fiber optic cable routing: Pull out the fiber optic cable 31 from the fiber optic cable reel 31, fixing the end of the fiber optic cable 31 in the tunnel where the initial support construction has been completed. Then, pull the fiber optic cable 31 through the support structure from the back of the reinforcing mesh 20, forming a monitoring section, a free section, and a turning section. Tie the monitoring section to the reinforcing mesh 20. Then, install an auxiliary sleeve 40 on the back of the reinforcing mesh 20, fitting it onto the free section. Install a protective sleeve 50 at the end of the support structure near the tunnel face, fitting it onto the turning section.

[0034] S400: Shotcrete, spraying concrete onto the support structure.

[0035] S500: Fiber optic cable loop cabling. As the next section of the tunnel is excavated, the tunnel support structure construction steps are repeated. The protective sleeve 50 is removed, and the fiber optic cable 31 in the free section and fiber optic cable reel 30 is pulled through the turning section, allowing the fiber optic cable 31 to pass through the newly constructed support structure, forming a new monitoring section, free section, and turning section. The monitoring section formed on the newly constructed support structure is then tied to the steel mesh 20, and the new auxiliary sleeve 40 is fitted onto the newly formed free section. The previously removed protective sleeve 50 is then fitted onto the newly formed turning section. The shotcrete process is then repeated.

[0036] The method for deploying distributed monitoring optical cables for tunnel initial support provided in this embodiment can be found in [reference needed]. Figure 5 The working principle is as follows:

[0037] After the tunnel support structure construction and fiber optic cable reel placement steps are completed, the initial wiring of fiber optic cable 31 is performed. At this point, the end of fiber optic cable 31 on the fiber optic cable reel 30 is pulled out and fixed in the tunnel where the initial support construction has been completed. Then, by pulling the fiber optic cable 31, it passes through the support structure from behind the reinforcing mesh 20. Due to the fixed end, fiber optic cable 31 forms a U-shaped structure on the back of the reinforcing mesh 20, consisting of a monitoring section, a free section, and a turning section. The free section and monitoring section are arranged side-by-side, with the free section directly connected to the fiber optic cable 31 wound on the fiber optic cable reel 30. The turning section is located close to the tunnel face. The monitoring section is then tied to the reinforcing mesh 20, and an auxiliary sleeve 40 is fitted onto the free section. A protective sleeve 50 is fitted onto the turning section of fiber optic cable 31. Shotcrete is then applied.

[0038] After the initial steps described above are completed, the next section of the tunnel is excavated, and the tunnel support structure construction steps are repeated after the excavation of the next section is finished. The protective sleeve 50 is removed, and the optical cable 31 is pulled through the turning section. At this time, the optical cable spool 30 is laid out, and the optical cable 31 will be pulled out from the auxiliary sleeve 40 in the previous section of the tunnel. The optical cable 31 is then guided through the newly constructed support structure, forming a U-shaped monitoring section, free section, and turning section at the new support structure. The newly formed monitoring section is then tied to the steel mesh 20 in the new support structure. The new auxiliary sleeve 40 is then fitted onto the newly formed free section, and the previously removed protective sleeve 50 is then fitted onto the newly formed turning section. The shotcrete process is then repeated.

[0039] The subsequent segmented construction of the tunnel involved repeating the optical cable loop laying steps, ensuring that optical cable 31 was laid throughout the entire area requiring monitoring.

[0040] For ease of understanding, regarding the back side of the steel mesh 20, that is, between the steel mesh and the tunnel wall.

[0041] During the intermittent advancement of optical cable 31, the cable maintains a U-shaped structure, with its free and monitoring sections continuously increasing in length, while the position of the turning sections constantly changes. The tunnel excavation process can be summarized as drilling, blasting, and muck removal; see [link to relevant documentation]. Figure 5 .

[0042] The distributed monitoring optical cable deployment method for tunnel initial support provided in this embodiment, compared with the prior art, involves installing steel mesh 20 on each steel arch frame 10 and fixing the monitoring section of the optical cable 31 to the steel mesh 20. The steel mesh 20 sensitively senses changes in the tunnel, and the deformation of the steel mesh 20 ensures that the optical cable 31 can monitor stress, strain, and temperature changes in the area of ​​the steel mesh 20. Because the range sensed by the steel mesh 20 is large, the monitoring range of the optical cable 31 is improved. In addition, through the initial optical cable laying steps and the optical cable cyclic laying steps, the optical cable 31 in the auxiliary sleeve 40 can be flexibly pulled to keep the optical cable spool 30 away from the tunnel face. At the same time, the protective sleeve 50 is set on the turning section to avoid damage to the optical cable 31 due to blasting during the subsequent tunnel excavation. This effectively protects the optical cable 31, improves the survival rate of the optical cable 31 in the initial support stage, and has strong practicality.

[0043] It should be noted that the deployment of distributed optical cables 31 is only for the geological conditions requiring monitoring. Therefore, this applies to tunnels where the initial support construction has been completed, i.e., tunnel sections where the initial support construction has been completed and monitoring is not required. Of course, as another implementation method, if monitoring is required for the entire tunnel, the optical cable reel 30 can be fixed at the tunnel entrance. The location of the optical cable reel 30 can be arranged according to the actual construction situation, and will not be elaborated here.

[0044] In some embodiments, the auxiliary sleeve 40 may be adopted as follows: Figure 3 The structure shown. See also Figure 3 Each auxiliary sleeve 40 has a first elongated notch 41 that penetrates the cavity of the auxiliary sleeve 40. The first elongated notch 41 must be set along the length of the auxiliary sleeve to ensure that the auxiliary sleeve 40 can be fitted onto the optical cable 31. The auxiliary sleeve 40 can provide a transmission channel for the optical cable, so that the free section of the optical cable 31 can be freely pulled out in the auxiliary sleeve 40 after the shotcrete step.

[0045] In this embodiment, a preferred implementation is that the auxiliary sleeve 40 is arranged along the length of the tunnel.

[0046] In some embodiments, the auxiliary sleeve 40 may be adopted as follows: Figure 3 The structure shown. See also Figure 3 The auxiliary sleeve 40 is made of PVC material, that is, the auxiliary sleeve 40 is a PVC pipe, which is inexpensive and easy to manufacture.

[0047] In some embodiments, the auxiliary sleeve 40 may be adopted as follows: Figure 2 The structure shown. See also Figure 2Each auxiliary sleeve 40 is fitted onto the optical cable 31 and then connected to the reinforcing mesh 20. After each auxiliary sleeve 40 is fitted onto the optical cable 31, the first long strip notch 41 is sealed with tape. Adjacent auxiliary sleeves 40 are connected via a connector 42 with an opening. Sealing the first long strip notch 41 with tape prevents mortar from entering the cavity of the auxiliary sleeve 40 during the shotcrete process, thus ensuring the free pulling of the optical cable 31. This sealing method is also simple to operate and inexpensive.

[0048] In this embodiment, the connection between the auxiliary sleeve 40 and the steel mesh 20 can be made using cable ties or wire.

[0049] In this embodiment, the proposed connector 42 with an opening is a cylindrical structure, with two auxiliary sleeves 40 inserted at its two ends, and the opening on the connector 42 ensures that it fits snugly onto the auxiliary sleeves 40. To ensure the connection stability of the connector 42, cable ties, wire, or clamps can be used to tighten the connector 42 and securely fit it onto the end of the auxiliary sleeve 40. Preferably, the opening of the connector 42 is offset from the first elongated notch 41.

[0050] In some embodiments, the protective sleeve 50 may be adopted as follows: Figure 4 The structure shown. See also Figure 4 The protective sleeve 50 is a U-shaped tube, and the U-shaped tube has a second long notch 51 that penetrates the cavity of the U-shaped tube. The second long notch 51 is located on the concave side of the U-shaped tube.

[0051] The U-shaped tube structure ensures compatibility with the turning section, and the second long notch 51 ensures that it can be fitted onto the turning section of the optical cable 31. At the same time, the second long notch 51 is located on the concave side of the U-shaped tube, which ensures that it is far away from the working face, thereby ensuring effective protection for the optical cable 31.

[0052] In this embodiment, regarding the concave side of the U-shaped tube, please refer to... Figure 4 Its U-shaped tube itself forms a concave side and a convex side. The concave side can ensure that the second long strip opening 51 is far away from the tunnel face, avoiding the impact of blasting during the next section of tunnel excavation.

[0053] In addition, in this embodiment, the second long strip opening 51 can be sealed with tape.

[0054] In some embodiments, the U-shaped tube described above can be adopted as follows: Figure 4 The structure shown. See also Figure 4 The U-shaped tube is made of rubber, which is highly flexible and has a cushioning effect. It can also better adapt to the shape of the optical cable 31 turning section, ensuring effective protection for the optical cable 31.

[0055] In some embodiments, the protective sleeve 50 may be adopted as follows: Figure 2 The structure shown. See also Figure 2 After the protective sleeve 50 is installed on the optical cable, one end of the protective sleeve 50 is fitted onto the end of the corresponding auxiliary sleeve 40. This structure prevents mortar from entering the auxiliary sleeve 40 or U-shaped pipe during the shotcrete process, and it is simple in structure, easy to operate, and highly practical.

[0056] In some embodiments, both ends of the protective sleeve 50 are tied and fixed to the steel mesh 20. This structure can ensure the fixation of the protective sleeve 50, thereby ensuring the protection of the optical cable 31 by the protective sleeve 50, and is highly practical.

[0057] Regarding the fixing of both ends of the protective sleeve 50, after one end of the protective sleeve 50 is fitted onto the auxiliary sleeve 40, a wire 52 can be used to tighten the protective sleeve 50 onto the auxiliary sleeve 40, and then the wire 52 can be tied to the reinforcing mesh 20. The other end of the protective sleeve 50 can be directly tied to the reinforcing mesh 20 with a wire.

[0058] In some embodiments, the initial wiring step of the optical cable 31 described above can be adopted as follows: Figure 2 and Figure 5 The structure shown. See also Figure 2 and Figure 5 In the initial wiring step of optical cable 31, guide tubes 60 are also used. There are two guide tubes 60, which are arranged side by side. One end of each guide tube 60 extends into the back of the steel mesh 20.

[0059] In the initial fiber optic cable routing step, the end of the fiber optic cable 31 is inserted into the back of the steel mesh 20 through one of the guide tubes 60, and then exits through the other guide tube after reversing direction.

[0060] The two guide tubes 60 ensure that the optical cable 31 led from the optical cable spool 30 can pass through the support structure in the tunnel section where the initial support has been completed. The optical cable spool 30 needs to be placed inside the steel mesh 20. At this time, the optical cable 31 needs to pass through the steel mesh 20. Therefore, the guide tubes 60 can protect the optical cable 31 at the end of the support structure and prevent the optical cable 31 from being damaged by the concrete during the shotcrete step.

[0061] It should be noted that during the initial fiber optic cable cabling process, the end of the fiber optic cable can first be inserted through one of the guide tubes 60 to the steel arch frame 10 closest to the working face (forming a free section), then reversed (forming a turning section), and subsequently exited through the other guide tube 60 (forming a monitoring section). A certain length of fiber optic cable 31 should be reserved when exiting the guide tube 60 to facilitate the fiber optic cable 31 exiting from the secondary lining and connecting to the distributed fiber optic cable 31 demodulator.

[0062] It should also be noted that the guide tube 60 can be tied to the steel mesh 20 with cable ties or wire. Moreover, the guide tube 60 corresponding to the auxiliary sleeve 40 needs to be connected to the auxiliary sleeve 40 with tape after the auxiliary sleeve 40 is installed, so as to prevent mortar from entering during the shotcrete step.

[0063] In this embodiment, the optical cable 31 and the steel mesh 20 are fixed by gradually binding them towards the working face from the guide tube 60. During the binding process, a prestress needs to be provided to the optical cable 31. Cable ties can be used to bind the optical cable 31.

[0064] In some embodiments, the guide tube 60 may be adopted as follows: Figure 2 The structure shown. See also Figure 2 The guide tube 60 is made of rubber, which can protect the optical cable 31 and is easy to shape and guide the optical cable 31 so that the optical cable 31 can pass through the steel mesh 20 and enter between the steel mesh 20 and the inner wall of the tunnel.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for deploying distributed monitoring optical cables for tunnel initial support, characterized in that, Includes the following steps: The tunnel support structure is constructed by continuously installing multiple steel arch frames in the excavated tunnel, and installing steel mesh around the outer edge formed by each steel arch frame; the steel arch frames and the steel mesh form a support structure. Place the optical cable reel in the tunnel after the initial support construction is completed; For the initial fiber optic cable laying, the fiber optic cable is pulled out from the fiber optic cable spool and the end of the fiber optic cable is fixed in the tunnel where the initial support construction has been completed. The optical cable is then pulled and passes through the support structure from the back of the steel mesh, forming a monitoring section, a free section, and a turning section. The monitoring section is then tied to the steel mesh. An auxiliary sleeve is installed and fitted onto the free section. A protective sleeve is installed at one end of the support structure near the working face and fitted onto the turning section. Shotcrete: Shotcrete is applied to the support structure. The optical cable is laid in a loop. As the next section of the tunnel is excavated, the tunnel support structure construction steps are repeated. The protective sleeve is removed, and the optical cable in the free section and the optical cable spool is pulled through the turning section, so that the optical cable passes through the newly constructed support structure to form a new monitoring section, free section, and turning section. Then, the newly formed monitoring section is tied to the steel mesh, the new auxiliary sleeve is placed on the newly formed free section, and the removed protective sleeve is placed on the newly formed turning section. Finally, shotcrete is applied. Each of the auxiliary sleeves is provided with a first elongated notch that extends through the lumen of the auxiliary sleeve; Each of the auxiliary sleeves is fitted onto the optical cable and then connected to the steel mesh. After each auxiliary sleeve is fitted onto the optical cable, the first long notch is sealed with tape. Adjacent auxiliary sleeves are connected by a connector with an opening. The protective sleeve is a U-shaped tube, and the U-shaped tube has a second elongated notch that penetrates the cavity of the U-shaped tube. The second elongated notch is located on the concave side of the U-shaped tube. The initial wiring of the optical cable also uses guide tubes. There are two guide tubes, which are arranged side by side. One end of each guide tube extends into the back of the steel mesh. The optical cable end can first be inserted through one of the guide tubes to the steel arch closest to the working face to form a free section, then the direction is reversed to form a turning section, and then it is inserted through another guide tube to form a monitoring section.

2. The method for laying distributed monitoring optical cables for tunnel initial support as described in claim 1, characterized in that, The auxiliary sleeve is made of PVC.

3. The method for laying distributed monitoring optical cables for tunnel initial support as described in claim 1, characterized in that, The U-shaped tube is made of rubber.

4. The method for laying distributed monitoring optical cables for tunnel initial support as described in claim 1, characterized in that, After the protective sleeve is installed on the optical cable, one end of the protective sleeve is fitted onto the corresponding end of the auxiliary sleeve.

5. The method for laying distributed monitoring optical cables for tunnel initial support as described in claim 4, characterized in that, Both ends of the protective sleeve are tied and fixed to the steel mesh.

6. The method for laying distributed monitoring optical cables for tunnel initial support as described in claim 1, characterized in that, The guide tube is made of rubber.

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