Excavation slope deformation monitoring system and construction method based on optical fiber strain sensing

Abstract

The present application relates to the field of water conservancy and hydropower technology, and provides an excavation slope deformation monitoring system and construction method based on optical fiber strain sensing. The system comprises a strain sensing optical cable, a protective tube, and an optical fiber strain demodulation device. A borehole extending horizontally from the original slope surface into the slope is provided at a position corresponding to the elevation of the slope and the bridleway. The protective tube is disposed in the borehole. The strain sensing optical cable comprises an optical cable connector, a measuring optical cable, and a transmission optical cable. One end of the measuring optical cable extends to the hole mouth, and the other end extends to the bottom of the hole and is connected to one end of the transmission optical cable. The transmission optical cable is disposed in the protective tube, and the other end extends to the hole mouth. The borehole is filled with grout outside the protective tube. The measuring optical cable is tensioned and disposed in the grout. The transmission optical cable is composed of multiple sections, and each section of the transmission optical cable is connected end to end by an optical cable connector. The optical cable connector is used to connect to the optical fiber strain demodulation device. This system achieves full-process deformation monitoring of the excavation slope, providing more realistic and effective measured data support for guiding the dynamic design and construction of the slope.

Description

Technical Field

[0001] The present invention relates to the technical field of water conservancy and hydropower, and in particular to an excavation slope deformation monitoring system and a construction method based on optical fiber strain sensing. Background Art

[0002] Slopes formed by artificial excavation include those along hydraulic structures, roads, and excavation sites. The stability of these slopes is directly related to the success of construction and subsequent operational safety. Slope deformation often begins with the unloading effect of excavation on the surface rock and soil, and gradually evolves and develops under the combined influence of natural factors (such as climate change and vegetation changes) and human factors (such as construction disturbances and support measures).

[0003] Slope instability is a continuous and gradual process. When slope excavation and unloading occur, the original equilibrium within the rock mass is disrupted, leading to a redistribution of stress within the rock mass. Weak areas yield and deform, and microcracks begin to appear in areas of stress concentration. With increasing unloading and over time, these cracks gradually expand and connect, ultimately leading to macroscopic damage in the rock mass, such as collapse or sliding. Therefore, monitoring slope conditions throughout the entire process is crucial for disaster prevention and mitigation.

[0004] In order to effectively deal with the stability problems caused by the development of slope deformation, it is necessary to implement slope deformation monitoring, understand the development and changes of slope deformation, and use it to guide the excavation and support design of the slope, thereby avoiding waste caused by oversaturated support or collapse of the excavated slope due to insufficient support. There are two main traditional slope deformation monitoring methods: one is to drill holes and bury multi-point displacement meters, inclinometers and other instruments for deep deformation monitoring after the slope excavation is completed; the other is to use total stations, levels, GNSS, InSAR and other equipment for surface deformation monitoring. Both of these traditional monitoring methods require the burying of measuring points after the slope is formed, and can only measure the deformation increment after the measuring point is installed. It is impossible to obtain the deformation of the slope during the excavation process and the early stage of excavation, and it is impossible to monitor the deformation of the entire excavation process of the slope.

[0005] Therefore, a new monitoring technology or method is needed to solve the deficiency of traditional monitoring methods in obtaining deformation data of the entire process. Summary of the Invention

[0006] In view of this, the embodiments of the present application provide an excavation slope deformation monitoring system and construction method based on optical fiber strain sensing, which solves the technical problem that existing monitoring technologies cannot obtain slope excavation process and pre-excavation deformation data.

[0007] A first aspect of an embodiment of the present application provides an excavation slope deformation monitoring system based on optical fiber strain sensing, comprising a strain sensing optical cable, a protective tube and an optical fiber strain demodulation device. A borehole extending horizontally from the original slope surface to the inside of the slope is provided at a position corresponding to the elevation of the slope and the horse trail. The protective tube is arranged in the borehole. The strain sensing optical cable comprises an optical cable connector, a measuring optical cable and a transmission optical cable. One end of the measuring optical cable extends to the hole mouth, and the other end extends to the bottom of the hole and is connected to one end of the transmission optical cable. The transmission optical cable is arranged in the protective tube, and the other end extends to the hole mouth. The borehole is filled with grouting outside the protective tube. The measuring optical cable is tensioned in the grouting. The transmission optical cable is divided into multiple sections, and each section of the transmission optical cable is connected end to end through an optical cable connector. The optical cable connector is used to connect the optical fiber strain demodulation device.

[0008] A second aspect of an embodiment of the present application provides a construction method of an excavation slope deformation monitoring system based on optical fiber strain sensing, comprising:

[0009] Before excavating the slope, according to the graded excavation design of the slope, horizontal holes corresponding to the elevation of the bridleway are drilled on the original slope surface;

[0010] Pass the transmission optical cable through the plug and connect it to the measuring optical cable through the optical cable connector, connect the plug to the nth section standard section, and place the measuring optical cable outside the protective tube and the transmission optical cable inside the protective tube;

[0011] Connect the end to end of each standard section, connect the end to end of each transmission optical cable inside each preset excavation line through an optical cable connector, and install an optical cable pulling box at the connection point. Set up a redundant section for each transmission optical cable;

[0012] Push the strain sensing optical cable and the protective tube into the borehole until the plug contacts the bottom of the hole, pre-tension the measuring optical cable, and backfill the borehole with grout outside the protective tube.

[0013] The first aspect of the embodiment of the present application provides an excavation slope deformation monitoring system based on optical fiber strain sensing, which uses a strain sensing optical cable as a sensing element and buries it in the slope rock and soil through grouting to achieve synchronous stretching or compression with the slope deformation. The transmission optical cable and the protective tube are connected to the optical fiber strain demodulation device to ensure that the sensing optical fiber has the measurement and reading conditions before excavation, and to achieve the calculation of the initial deformation measurement value during the construction period. By setting the transmission optical cable into multiple sections, and connecting each section of the transmission optical cable end to end through an optical cable connector, the optical fiber strain demodulation device can be connected through the optical cable connector after each level of excavation blasting to ensure that the sensing optical fiber always has the measurement and reading conditions during and after excavation, thereby achieving full-process deformation monitoring of the excavation slope, thereby providing more real and effective measured data support for guiding the dynamic design and construction of the slope.

[0014] It can be understood that the beneficial effects of the second aspect mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0016] Figure 1 This is a structural diagram of an excavation slope deformation monitoring system based on optical fiber strain sensing provided by an embodiment of the present application;

[0017] Figure 2 It is a schematic diagram of the internal structure of the drilling hole of this application;

[0018] Figure 3 It is a structural diagram of the protection tube of this application;

[0019] Figure 4 This is a schematic diagram of the structure of the optical cable pulling box of the present application;

[0020] Figure 5 It is a structural schematic diagram of the traction rod of this application.

[0021] In the figure: 1-strain sensing optical cable, 11-measuring optical cable, 12-transmission optical cable, 121-redundant section, 13-optical cable connector, 14-optical cable traction box, 141-box cover, 142-box body, 143-optical cable connector fixing groove, 144-optical cable fixing groove, 145-fixing screw, 2-protective tube, 21-standard section, 22-plug, 221-arc-shaped cavity, 3-slope, 31-original slope surface, 32-preset excavation line, 33-drilling hole, 34-grouting, 4-traction rod, 41-magnet. DETAILED DESCRIPTION

[0022] In the following description, specific details such as specific system structures and techniques are provided for purposes of illustration rather than limitation to facilitate a thorough understanding of the embodiments of the present application. However, it will be apparent to those skilled in the art that the present application may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid obscuring the description of the present application with unnecessary detail.

[0023] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or collections thereof.

[0024] References to "one embodiment" or "some embodiments" in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more but not all embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof all mean "including but not limited to," unless otherwise specifically emphasized.

[0025] like Figure 1 As shown, the excavation slope deformation monitoring system based on optical fiber strain sensing provided by the embodiment of the present application includes a strain sensing optical cable 1, a protective tube 2 and an optical fiber strain demodulation device. A borehole 33 extending horizontally from the original slope surface 31 to the inside of the slope is provided at a position corresponding to the elevation of the slope 3 and the horse trail. The protective tube 2 is arranged in the borehole 33. The strain sensing optical cable 1 includes an optical cable connector 13, a measuring optical cable 11 and a transmission optical cable 12. One end of the measuring optical cable 11 extends to the hole mouth, and the other end extends to the bottom of the hole and is connected to one end of the transmission optical cable 12. The transmission optical cable 12 is arranged in the protective tube 2, and the other end extends to the hole mouth. The borehole 33 is filled with grouting 34 outside the protective tube 2. The measuring optical cable 11 is tensioned in the grouting 34. The transmission optical cable 12 is divided into multiple sections, and each section of the transmission optical cable 12 is connected end to end through an optical cable connector 13. The optical cable connector 13 is used to connect to the optical fiber strain demodulation device.

[0026] In application, the portable fiber optic strain interrogator is a fiber optic strain measurement and reading device equipped with a switch, data transmission connector, indicator light, optical cable connector, display screen and portable protective box. It is easy to carry, has its own battery power supply, supports local data export, can be operated by touch screen, and is plug and play.

[0027] In practice, this monitoring system is designed to provide a reliable method for monitoring the stability of excavated slopes during and after construction. By deploying strain-sensing optical cables 1 into pre-drilled holes and ensuring their synchronization with the slope's movement, real-time monitoring of internal slope stress and displacement is achieved, a crucial step in ensuring project safety. This effectively addresses the challenges of traditional slope monitoring technologies, such as delayed measurement start times, susceptibility to construction interference, and discontinuous monitoring cycles. It provides strong technical support for guiding slope excavation construction, optimizing slope support schemes, and conducting slope stability assessments.

[0028] In one embodiment, the measuring optical cable 11 is a weak grating optical cable, the transmission optical cable 12 is a single-mode optical cable, and the transmission optical cable 12 is divided into n sections. Each section of the transmission optical cable 12 is connected end to end at the inner side of each preset excavation line 32 through an optical cable connector 13;

[0029] Here, n-1 is the number of preset excavation lines 32, and n is an integer greater than 1.

[0030] In applications, weak grating cables are sensing cables fabricated using ultra-weak fiber Bragg grating (WFBG) technology. Thousands of sensing units are engraved on a single optical fiber as needed. Time-division / wavelength-division multiplexing (TD / WDM) greatly increases the number of sensing units and spatial resolution, enabling dense, point-based, high-strain sensing. By summing the strain at each point along the cable, the deformation along the cable's length can be determined.

[0031] In application, single-mode optical cable is an ordinary single-mode optical cable used for the access and output of optical signals in weak grating optical cables. Single-mode optical cable only supports one propagation mode, which can not only reduce signal propagation loss, but also alleviate dispersion problems, thereby maintaining signal integrity and transmission quality.

[0032] In practice, fiber optic cable connector 13 is an FC (ferrule connector) used to interconnect segmented optical cables, including connections between weak-bandwidth fiber optic cables and standard single-mode fiber optic cables, as well as between segments of standard single-mode fiber optic cables. FC fiber optic connectors offer advantages such as high reliability, high stability, strong vibration resistance, wide applicability, and easy maintenance, making them well suited to the complex construction environments found at slope excavation sites. FC fiber optic connectors are pre-fabricated in a laboratory setting, effectively preventing the ingress of dust and other impurities, improving optical signal transmission quality. Manual connection is possible at the construction site, facilitating operation and implementation by construction personnel.

[0033] In one embodiment, the protective tube 2 includes n standard sections 21 connected end to end along the direction of the drill hole 33 and a plug 22. The n standard sections 21 are threadedly connected to each other, the plug 22 is set at the bottom of the drill hole 33, and the plug 22 is threadedly connected to the end of the nth standard section 21. One end of the transmission optical cable 12 extends from the end of the first standard section 21 facing the hole opening and is used to connect to the optical fiber strain demodulation device. The other end passes through the plug 22 and is connected to the other end of the measuring optical cable 11.

[0034] In use, the protective tube 2 provides physical protection within the drilled hole 33, protecting the strain sensing cable from external influences or damage. By utilizing multiple standard sections 21 and a plug 22 to construct the protective tube, the structural integrity is enhanced while also facilitating installation and maintenance. The threaded connection design provides a tighter connection between the components and simplifies assembly. Furthermore, this design allows the length of the protective tube 2 to be flexibly adjusted to accommodate drilled holes 33 of varying depths.

[0035] In practice, the standard section can be made of polyvinyl chloride (PVC), with threaded ends at both ends, connecting end to end. Its inner diameter is related to the turning radius of the common single-mode optical cable used for signal transmission within the tube, typically no less than 60mm, and uses a standard section splicing design. The plug is used to seal the standard section at the end (i.e., the nth section of the standard section). It is made of the same material as the standard section and is connected to the standard section at the end using a threaded design.

[0036] In one embodiment, a curved cavity 221 is provided in the plug 22 and passes through the end surface of the plug 22 . The transmission optical cable 12 passes through the curved cavity 221 and is connected to the other end of the measurement optical cable 11 at the end surface of the plug 22 through the optical cable connector 13 .

[0037] In use, arc-shaped cavity 221 is semicircular, allowing the weak-grating optical cable to connect to the FC cable connector on the plug. This allows the optical cable to pass from outside the protective tube through a fiber optic loop to the standard single-mode optical cable inside. The radius of this arc-shaped loop is no less than 10 times the outer diameter of the outer sheath of a standard single-mode optical cable, ensuring a smooth turning radius and minimizing optical loss. The provision of arc-shaped cavity 221 not only provides a smooth passage for the optical cable, reducing the risk of friction and wear, but also simplifies the cable connection process. This design facilitates installation and improves system durability, as the optical cable can pass smoothly through plug 22 without excessive pressure.

[0038] In one embodiment, each section of the transmission cable 12 within the standard section 21 is equipped with a redundant section 121. This redundant section 121 is configured to extend the corresponding section of the transmission cable 12 to the borehole opening. If the front end of the transmission cable 12 becomes damaged during excavation, the redundant section 121 can be deployed to allow the connector at the end of the transmission cable 12 to extend out of the borehole and continue to connect to the optical fiber strain detuning device.

[0039] In one embodiment, an optical cable traction box 14 is provided on the inner side of each excavation line 32 in the protective tube 2. The optical cable traction box 14 is provided with an optical cable joint fixing groove 143 in the middle and optical cable fixing grooves 144 at both ends. The transmission optical cable 12 passes through the optical cable traction box 14 and is fixed by the optical cable fixing groove 144. The optical cable connector 13 of the upper section of the transmission optical cable 12 is connected to the optical cable connector 13 of the lower section of the transmission optical cable 12 and are fixed by the corresponding optical cable joint fixing grooves 143 respectively.

[0040] In use, the cable traction box 14 consists of two parts: a cover 141 and a body 142. Inside, there are cable connector fixing grooves 143 and 144. During use, the cable connector 13 and the transmission cable 12 are secured in these grooves 143 and 144, respectively. The upper and lower parts of the cable traction box 14 are then sealed with fixing screws 145. The cable traction box 14 is pre-installed at the FC cable connector to protect it and serve as a magnetic traction device.

[0041] In one embodiment, a traction rod 4 is further included, and the traction rod 4 is configured to extend into the protection tube 2 and pull the optical cable traction box 14 out of the protection tube 2 .

[0042] In use, a magnet 41 is provided at the end of the traction rod 4 for attracting the optical cable traction box 14 , thereby pulling the optical cable traction box 14 out of the protective tube.

[0043] The construction method of the excavation slope deformation monitoring system based on optical fiber strain sensing provided in the embodiment of the present application includes:

[0044] Step S1: Before excavating the slope, according to the graded excavation design of the slope, drill holes horizontally on the original slope surface corresponding to the elevation of the bridleway.

[0045] In practice, before excavating the slope, according to the graded excavation design, a horizontal hole is drilled on the original slope surface at the same elevation as the bridleway. The hole diameter should be no less than twice the outer diameter of the protective tube, and the hole depth should be sufficient to avoid the impact of excavation unloading. Geological factors such as weathering, potential sliding surfaces, and groundwater should also be considered to ensure that the deformation of the hole bottom caused by slope excavation is sufficiently small so that the rock at the hole bottom can be regarded as a fixed point. After drilling, the hole is cleaned.

[0046] In practice, the present embodiment requires installation at a depth that is unaffected by excavation unloading. Geological factors such as the degree of slope weathering, the impact range of blasting, potential slip surfaces, and groundwater are also considered to ensure that the deformation at the bottom of the hole caused by slope excavation is sufficiently small so that the rock at the bottom of the hole can be considered a fixed point. Furthermore, the drilled hole is backfilled with cement mortar, which protects the sensing cable after solidification. Therefore, compared to traditional slope deformation monitoring technology, each slope blasting and excavation during construction will not have a substantial impact on the strain sensing cable, nor will it interrupt continuous observation of slope deformation.

[0047] Step S2: Pass the transmission optical cable through the plug and connect it to the measuring optical cable through the optical cable connector. Connect the plug to the nth standard section, and place the measuring optical cable outside the protective tube and the transmission optical cable inside the protective tube.

[0048] During application, prepare weak-beam grating cables, standard single-mode cables, and protective tubes according to the drilling depth. To ensure accuracy, the weak-beam grating cables should be continuous within the measurement range and slightly longer than the hole depth. Standard single-mode cables should be connected in multiple stages, with a total length greater than 1.2 times the drilling depth. The total length of the protective tube should also be slightly longer than the drilling depth. The weak-beam grating cables, standard single-mode cables, and FC cable connectors on the plugs should be prepared in advance in a laboratory environment.

[0049] Step S3: Connect the standard sections end to end, connect each section of transmission optical cable end to end inside each preset excavation line through an optical cable connector, set an optical cable pulling box at the connection point, and set a redundant section for each section of transmission optical cable.

[0050] In application, the standard sections are connected end to end to form a protective tube with a total length slightly greater than the drilled hole depth. The weak-band grating optical cable outside the protective tube is pre-tensioned and secured to a certain degree; the ordinary single-mode optical cable inside the protective tube is loosely placed. Based on the excavation design, FC cable connectors and pulling boxes are installed approximately 50 cm inside each graded excavation line, with a certain amount of redundant length reserved next to the connectors.

[0051] Step S4: Push the strain sensing optical cable and the protective tube into the borehole until the plug contacts the bottom of the hole, pre-tension the measuring optical cable, and backfill the borehole outside the protective tube with grouting.

[0052] During application, the optical cable and protective tube assembly is slowly pushed into the borehole until it reaches the designed bottom depth. The borehole is then backfilled with cement mortar. During grouting, the protective tube opening is temporarily sealed until the borehole is completely filled. After the grouting has naturally settled, the grout is then added to the hole opening. After the cement mortar has solidified, the protective tube opening is opened, and the FC cable connector is connected to a portable fiber Bragg grating interrogator for pre-excavation testing and debugging.

[0053] In one embodiment, after grouting backfilling the drill hole and the outside of the protective tube, the method further includes:

[0054] Connect the optical cable connector to the optical fiber strain demodulation device for testing and debugging;

[0055] After the test and debugging are normal, the bottom of the drill hole is used as the reference point to calculate the initial deformation value during the construction period;

[0056] After the i-th blasting excavation of the slope, the i-th optical cable traction box is pulled out of the borehole using a traction rod, the optical cable traction box is removed, and the optical cable connector is connected to the optical fiber strain demodulation device to perform deformation measurement and calculation;

[0057] Wherein, i=1,2,…,n, and n is an integer greater than 1.

[0058] In application, after testing and debugging, if everything is normal, the bottom of the hole is used as a fixed point, and each measuring point from the hole mouth to the bottom of the hole (with a spacing of 0.5m or 1m) uses the fixed point of the hole bottom as the reference point to calculate the initial measurement value of the deformation during the construction period; after obtaining the initial measurement value, the deformation during the construction period is monitored according to the slope excavation and monitoring plan.

[0059] After the first blasting excavation of the slope, the optical cables outside the first-stage excavation line are removed by blasting. The magnetic attraction of the traction rod then magnetically draws the first traction box out of the protective tube. The traction box is then removed, and the FC cable connector is connected to a portable fiber Bragg grating interrogator to measure and calculate deformation from the bottom of the hole to the hole mouth. This process is repeated after each subsequent stage of excavation, with deformation measurement and calculations performed until the final designed excavation line is reached. This process can then be incorporated into an automated monitoring system to continuously monitor the slope's stability during operation.

[0060] In one embodiment, by statistically analyzing and arranging deformation measurements after each excavation, the total deformation amount and deformation process data caused by slope excavation can be obtained, thereby better supporting slope support design and ensuring slope safety.

[0061] In application, deformation observation has high spatial resolution. By pre-buried strain sensing optical cables, continuous strain measurement along the drilling direction can be achieved. By summing the strain from the fixed point at the bottom of the hole to each measuring point, the deformation of each point relative to the bottom of the hole can be obtained. Compared with traditional instruments such as multi-point displacement meters and borehole inclinometers, this method can obtain the deformation of any point in the borehole and can more accurately observe the deformation distribution gradient from the outside to the inside of the slope. The deformation calculation method is as follows:

[0062] When an incident light wave enters the fiber Bragg grating (FBG), the Bragg wavelength and effective refractive index , grating period The relationship is as follows:

[0063]

[0064] The coupled wavelength Considered as temperature T and strain function, ignoring the higher-order terms, the drift of the fiber Bragg grating wavelength as follows:

[0065]

[0066] By measuring the change of the FBG central wavelength, the change of external physical quantities (such as strain, temperature, etc.) can be measured. The formula for measuring the axial strain of the fiber Bragg grating is: , from the above formula, we can see that and There is a linear relationship, and the offset of the Bragg wavelength is detected by the optical fiber strain demodulation device , the measured value can be calculated changes.

[0067] When the cable gauge length L is known, according to and deformation The relationship equation , and further calculate the deformation of the measuring range .

[0068] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. An excavation slope deformation monitoring system based on optical fiber strain sensing, characterized in that: The invention comprises a strain sensing optical cable (1), a protective tube (2) and an optical fiber strain demodulation device. A borehole (33) extending horizontally from an original slope surface (31) into the slope is provided at a position corresponding to the elevation of the bridleway (3). The protective tube (2) is arranged in the borehole (33). The strain sensing optical cable (1) comprises an optical cable connector (13), a measuring optical cable (11) and a transmission optical cable (12). One end of the measuring optical cable (11) extends to the hole mouth, and the other end extends to the hole bottom and is connected to the transmission optical cable (12). 12), the transmission optical cable (12) is arranged in the protection tube (2), and the other end extends to the hole mouth, the borehole (33) is filled with grouting (34) outside the protection tube (2), the measuring optical cable (11) is tensioned and arranged in the grouting (34), the transmission optical cable (12) is divided into multiple sections, and each section of the transmission optical cable (12) is connected end to end through an optical cable connector (13), and the optical cable connector (13) is used to connect the optical fiber strain demodulation device.

2. The excavation slope deformation monitoring system based on optical fiber strain sensing according to claim 1, characterized in that: The measuring optical cable (11) is a weak grating optical cable, the transmission optical cable (12) is a single-mode optical cable, the transmission optical cable (12) is divided into n sections, and each section of the transmission optical cable (12) is connected end to end on the inner side of each preset excavation line (32) through an optical cable connector (13); Wherein, n-1 is the number of preset excavation lines (32), and n is an integer greater than 1.

3. The excavation slope deformation monitoring system based on optical fiber strain sensing according to claim 2, characterized in that: The protective tube (2) comprises n sections of standard sections (21) and a plug (22) connected end to end along the direction of the borehole (33), wherein the n sections of the standard sections (21) are threadedly connected to each other, the plug (22) is arranged at the bottom of the borehole (33), and the plug (22) is threadedly connected to the end of the nth section of the standard section (21), one end of the transmission optical cable (12) extends out from the end of the first section of the standard section (21) toward the hole opening and is used to be connected to the optical fiber strain demodulation device, and the other end passes through the plug (22) and is connected to the other end of the measuring optical cable (11).

4. The excavation slope deformation monitoring system based on optical fiber strain sensing according to claim 2, characterized in that: An optical cable traction box (14) is provided on the inner side of each excavation line (32) in the protective tube (2). The optical cable traction box (14) is provided with an optical cable joint fixing groove (143) in the middle and optical cable fixing grooves (144) at both ends. The transmission optical cable (12) passes through the optical cable traction box (14) and is fixed by the optical cable fixing groove (144). The optical cable joint (13) of the upper section of the transmission optical cable (12) and the optical cable joint (13) of the lower section of the transmission optical cable (12) are connected to each other and are fixed by corresponding optical cable joint fixing grooves (143).

5. The excavation slope deformation monitoring system based on optical fiber strain sensing according to claim 3, characterized in that: Each section of the transmission optical cable (12) in the standard section (21) is provided with a redundant section (121), and the redundant section (121) is configured to enable the corresponding section of the transmission optical cable (12) to extend to the orifice after being unfolded.

6. The excavation slope deformation monitoring system based on optical fiber strain sensing according to claim 3, characterized in that: An arc-shaped cavity (221) penetrating the end face of the plug (22) is provided in the plug (22); the transmission optical cable (12) passes through the arc-shaped cavity (221) and is connected to the other end of the measurement optical cable (11) at the end face of the plug (22) via the optical cable connector (13).

7. The excavation slope deformation monitoring system based on optical fiber strain sensing according to claim 4, characterized in that: It also includes a traction rod (4), which is configured to extend into the protective tube (2) and pull the optical cable traction box (14) out of the protective tube (2).

8. A construction method of an excavation slope deformation monitoring system based on optical fiber strain sensing according to any one of claims 1 to 7, characterized in that: include: Before excavating the slope, according to the graded excavation design of the slope, horizontal holes corresponding to the elevation of the bridleway are drilled on the original slope surface; Pass the transmission optical cable through the plug and connect it to the measuring optical cable through the optical cable connector, connect the plug to the nth section standard section, and place the measuring optical cable outside the protective tube and the transmission optical cable inside the protective tube; Connect the end to end of each standard section, connect the end to end of each transmission optical cable inside each preset excavation line through an optical cable connector, and install an optical cable pulling box at the connection point. Set up a redundant section for each transmission optical cable; Push the strain sensing optical cable and the protective tube into the borehole until the plug contacts the bottom of the hole, pre-tension the measuring optical cable, and backfill the borehole with grout outside the protective tube.

9. The construction method according to claim 8, wherein: The drill hole is backfilled with grout outside the protective tube, including: sealing the orifice of the protective tube; Performing grouting backfill in the borehole; After the slurry solidifies, the seal on the opening of the protection tube is released.

10. The construction method according to claim 8, wherein: After grouting backfilling the borehole and the outside of the protection tube, the method further includes: Connecting the optical cable connector to an optical fiber strain demodulation device for testing and debugging; After the test and debugging are normal, the bottom of the drill hole is used as the reference point to calculate the initial deformation value during the construction period; After the i-th blasting excavation of the slope, the i-th optical cable traction box is towed out of the borehole using a traction rod, the optical cable traction box is removed, and the optical cable connector is connected to the optical fiber strain demodulation device to perform deformation measurement and calculation; Wherein, i=1,2,…,n, and n is an integer greater than 1.

Images