A method for monitoring a slope step by step by combining optical fiber and NPR anchor cable

Abstract

The present application relates to the technical field of landslide monitoring, in particular to a kind of optical fiber and NPR anchor cable combined slope step type monitoring method.The method comprises: optical fiber sensor is fixed on NPR anchor cable according to preset mode, forms anchor cable optical fiber sensor;After numbering grouping, anchor cable optical fiber sensor is fixed in slope;The newton force corresponding to each anchor cable optical fiber sensor is obtained, the newton force corresponding to each anchor cable optical fiber sensor is obtained based on fitting;According to the newton force variation curve corresponding to each anchor cable optical fiber sensor, the early warning level is judged, and the judgment duration is determined according to the early warning level;In judgment duration, the strain value corresponding to each anchor cable optical fiber sensor at each time is obtained;According to the strain value corresponding to each anchor cable optical fiber sensor at each time in each group of anchor cable optical fiber sensor, the position of most likely landslide is determined.The present application can accurately warn slope landslide, and determine the position of most likely landslide of slope.

Description

Technical Field

[0001] This invention relates to the field of landslide monitoring technology, specifically to a stepped slope monitoring method combining optical fiber and NPR anchor cable. Background Technology

[0002] Landslides are often the leading geological disaster, and the construction of slope engineering is affected by human factors and the natural geological environment. How to accurately grasp the instability and deformation process and state information of landslides, and establish a more accurate, reliable and intuitive slope stability evaluation and monitoring system has received widespread attention.

[0003] The generation of Newtonian forces at the most likely landslide locations is a necessary and sufficient condition for landslide disasters, and the changes in these forces characterize the actual movement of the landslide. However, Newtonian forces cannot be directly measured throughout the entire landslide process; therefore, methods must be employed to transform them into readily observable data. NPR anchor cables possess exceptional mechanical properties such as high constant resistance, large deformation, energy absorption, and impact resistance, making them a suitable and durable support structure for slopes. By monitoring changes in the axial force of the anchor cables, Newtonian forces can be converted into visible data for early warning.

[0004] Although distributed fiber optic sensing technology has improved the shortcomings of traditional slope monitoring instruments such as poor durability, low survival rate and complicated deployment, the mechanical properties of slopes are relatively complex and optical fibers are easily damaged. It is often difficult to achieve continuous monitoring and early warning by using fiber optic sensors alone to monitor the slope. It cannot fully capture the dynamic deformation of landslides and cannot determine the location of possible landslides on the slope. Summary of the Invention

[0005] To address the challenges of using only fiber optic sensors for slope monitoring, which often fails to provide continuous monitoring and early warning, comprehensively captures dynamic landslide deformation, and pinpoints potential landslide locations, this invention aims to provide a stepped slope monitoring method combining fiber optics and NPR anchor cables. The specific technical solution adopted is as follows:

[0006] One embodiment of the present invention provides a stepped slope monitoring method combining optical fiber and NPR anchor cable, the method comprising:

[0007] The fiber optic sensor is fixed to the NPR anchor cable in a preset manner to form an anchor cable fiber optic sensor.

[0008] The anchor cable fiber optic sensors are numbered and grouped, and the numbered and grouped anchor cable fiber optic sensors are fixed in the slope.

[0009] The Newton force corresponding to each anchor cable fiber optic sensor is obtained by using a stress sensor, and the Newton force variation curve corresponding to each anchor cable fiber optic sensor is obtained by fitting based on the Newton force.

[0010] The warning level is determined based on the Newton force change curve corresponding to each anchor cable fiber optic sensor, and the judgment duration is determined based on the warning level.

[0011] Within the judgment time period, obtain the strain value corresponding to each anchor cable fiber optic sensor at each moment;

[0012] The location most likely to be a landslide is determined based on the strain value of each anchor fiber optic sensor in each group at each moment.

[0013] Preferably, the fiber optic sensor is fixed to the NPR anchor cable in a preset manner to form an anchor cable fiber optic sensor, comprising:

[0014] The NPR anchor cable includes internal reinforcing bars. The fiber optic sensor is uniformly wound around the surface of the internal reinforcing bars of the NPR anchor cable and fixed. The fiber optic sensor fixed to the surface of the internal reinforcing bars of the NPR anchor cable is encapsulated to form an anchor cable fiber optic sensor.

[0015] Preferably, the anchor cable fiber optic sensors are numbered and grouped, and the numbered and grouped anchor cable fiber optic sensors are fixed in the slope, including:

[0016] The anchor bolt fiber optic sensors are numbered sequentially; the numbered anchor cable fiber optic sensors are grouped according to their position and depth embedded in the soil of the slope, with the anchor cable fiber optic sensors in the same group embedded in the soil of the slope to the same depth.

[0017] Preferably, the method of obtaining the Newton force corresponding to each anchor cable fiber optic sensor using a stress sensor includes:

[0018] Stress sensors are installed on the upper end face of each anchor fiber sensor to measure the axial force of the NPR anchor in the anchor fiber sensor, which is used as the Newton force corresponding to each anchor fiber sensor.

[0019] Preferably, the warning level is determined based on the Newton force change curve corresponding to each anchor cable fiber optic sensor, and the judgment duration is determined based on the warning level, including:

[0020] The warning levels are divided into two categories based on the change in Newtonian force. The first warning level is triggered when the slope of the Newtonian force change curve is greater than 0 or the increment of Newtonian force reaches 20-50 kN. The second warning level is triggered when the slope of the Newtonian force change curve reaches the inflection point between greater than and less than 0 or the increment of Newtonian force reaches 50-100 kN. The slope and increment of the Newtonian force change curve corresponding to each anchor cable fiber optic sensor are acquired. If the Newtonian force change curve corresponding to any anchor cable fiber optic sensor meets the criteria for the first warning level, the moment when the first warning level is reached is recorded as the start time of the judgment. When the criteria for the second warning level are met, the moment when the second warning level is reached is recorded as the end time of the judgment. The duration between the start time and the end time of the judgment is the judgment duration.

[0021] Preferably, obtaining the strain value corresponding to each anchor cable fiber optic sensor at each moment includes:

[0022] The strain of each anchor cable fiber optic sensor at each moment is measured using BOTDR technology to obtain the corresponding strain value of each anchor cable fiber optic sensor at each moment.

[0023] Preferably, the location most likely to experience a landslide is determined based on the strain value of each anchor fiber optic sensor in each group of anchor fiber optic sensors at each moment, including:

[0024] The strain acceleration of the same fiber optic sensor at each time point is obtained by using the strain acceleration of the same fiber optic sensor at each time point; the strain jerk of the same fiber optic sensor at each time point is obtained by using the strain acceleration of the same fiber optic sensor at each time point; the average strain jerk of the same fiber optic sensor at the same time point in each group of fiber optic sensors is obtained by averaging the strain jerk of the same fiber optic sensor at each time point.

[0025] Based on the jerk of the average strain value at each moment corresponding to each group of anchor fiber optic sensors, a first curve corresponding to each group of anchor fiber optic sensors is obtained; the groups of anchor fiber optic sensors corresponding to the two uppermost first curves are obtained and denoted as the first abnormal group and the second abnormal group; the depth range of possible landslide depth is determined according to the depth corresponding to the anchor fiber optic sensors in the first abnormal group and the second abnormal group.

[0026] The strain values ​​of each anchor fiber optic sensor in the first and second anomaly groups at each time moment are fitted to obtain the second curve corresponding to each anchor fiber optic sensor; the position of the anchor fiber optic sensor corresponding to the uppermost second curve is obtained, which is the position where the landslide is most likely to occur.

[0027] The embodiments of this invention have at least the following beneficial effects: This invention combines fiber optic sensors and NPR anchors, utilizing the high sensitivity of the fiber optic cable and the ability of the NPR anchor to reflect changes in Newtonian force. This combination effectively improves the accuracy of slope landslide monitoring. Furthermore, by embedding the fiber optic sensor and NPR anchor into the slope, the NPR anchor can be used to fix the slope, and both the fiber optic sensor and the NPR anchor can be anchored together in the soil, enabling three-dimensional monitoring of the slope and increasing monitoring accuracy. This application also utilizes stress sensors to monitor the fiber transmission of each anchor. The system senses the corresponding Newtonian force and then fits it to obtain a Newtonian force variation curve. Based on this curve, the warning level is determined, and the judgment duration is used to determine the start and end times of monitoring using the strain values ​​of the anchor cable fiber optic sensor. This allows for more accurate slope monitoring while reducing computational load. Finally, based on the warning level determined by the Newtonian force, the average strain value of each set of anchor cable fiber optic sensors at each moment is analyzed. This not only enables landslide warnings but also identifies the most likely location of a landslide on the slope, providing more information about landslide occurrences and improving monitoring effectiveness. Attached Figure Description

[0028] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A flowchart illustrating a method for slope stepped monitoring combining optical fiber and NPR anchor cable, provided in an embodiment of the present invention;

[0030] Figure 2 A simplified schematic diagram of the fiber optic sensor and anchor cable combination in a slope stepped monitoring method combining fiber optic and NPR anchor cables provided in an embodiment of the present invention;

[0031] Figure 3 An anchor cable fiber optic sensor monitoring diagram for a slope stepped monitoring method combining fiber optic cable and NPR anchor cable provided in an embodiment of the present invention;

[0032] Figure 4 This is a fiber optic surface laying diagram for a slope stepped monitoring method combining optical fiber and NPR anchor cable, provided in an embodiment of the present invention. Detailed Implementation

[0033] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a slope stepped monitoring method combining optical fiber and NPR anchor cables proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0035] The following description, in conjunction with the accompanying drawings, details the specific scheme of the slope stepped monitoring method combining optical fiber and NPR anchor cable provided by this invention.

[0036] Example:

[0037] The main application scenario of this invention is as follows: landslides are one of the most serious geological disasters. Once a landslide occurs, it will threaten people's lives and property. Therefore, it is necessary to monitor the slope and locate the possible landslide locations so as to deal with them more accurately. This invention is mainly used for slope monitoring and early warning to prevent the harm caused by geological disasters.

[0038] Please see Figure 1 The diagram illustrates a method flowchart for a stepped slope monitoring method combining optical fiber and NPR anchor cable, provided by an embodiment of the present invention. The method includes the following steps:

[0039] Step S1: Fix the fiber optic sensor on the NPR anchor cable according to a preset method to form an anchor cable fiber optic sensor; number and group the anchor cable fiber optic sensors, and fix the numbered and grouped anchor cable fiber optic sensors in the slope.

[0040] Optical fibers possess advantages such as excellent anti-interference capabilities, ease of implantation, and high accuracy. Therefore, this application combines optical fiber sensors and NPR anchor cables for monitoring slope landslides. The internal support structure of the slope, besides controlling deformation and reinforcing the design, also plays a certain early warning role. Currently, no method has been found to combine optical fibers and support materials to achieve early warning of impending landslides. This invention provides a method for capturing the dynamic response of slopes using both Newtonian force monitoring and optical fiber sensor monitoring, aiming to achieve more comprehensive and accurate monitoring.

[0041] First, the fiber optic sensor and NPR anchor cable need to be combined. The NPR anchor cable includes internal steel reinforcement, a constant resistance sleeve, and gaskets. During the fabrication of the NPR anchor cable, the fiber optic sensor needs to be fixed to it. Specifically, the corresponding fiber optic sensor is evenly wound around the surface of the internal steel reinforcement of the NPR anchor cable and then fixed in place. Figure 2 As shown, the fiber optic sensor and NPR anchor cable are integrated into one unit. When integrated, the fiber optic sensor is only wrapped around a portion of the NPR anchor cable, not the entire cable. Due to the fragility of the fiber optic cable, it is necessary to take sufficient measures to protect the fiber optic sensor when combining the two. The fiber optic sensor, which is fixed to the surface of the internal steel reinforcement of the NPR anchor cable, is encapsulated using encapsulation technology to strictly protect it and prevent the fiber optic cable from breaking first during construction or when a landslide occurs on the slope, thus affecting the timing of the early warning.

[0042] It should be noted that when fixing the fiber optic sensor to the surface of the internal reinforcing steel of the NPR anchor cable, the fixing method can be adjusted by the implementer according to the actual situation. In this invention, a spiral winding method is used, which can increase the contact surface of the fiber optic sensor, increase its sensitivity, and make the monitoring results more accurate.

[0043] For the encapsulation of the fiber optic sensor fixed to the surface of the internal reinforcing steel of the NPR anchor cable, this embodiment of the invention adopts an encapsulation method by adding a coating layer and a sheath to the outer layer. During encapsulation, the strength of the sheath needs to be considered. Generally, higher sheath strength will worsen the deformation compatibility between the fiber optic cable and the soil, resulting in larger measurement errors and reduced sensitivity of the fiber optic sensor. In actual engineering, the choice of fiber optic protection measure needs to be determined based on the slope soil properties and through indoor tests. Different encapsulation techniques should be adopted to protect the fiber optic sensor according to different working conditions. Thus, the fiber optic sensor and the NPR anchor cable can be integrated into one unit as an anchor cable fiber optic sensor.

[0044] Once the anchor cable fiber optic sensors are obtained, they need to be deployed within the slope. Then, the anchor cable fiber optic sensors are numbered sequentially. In this embodiment, 12 anchor cable fiber optic sensors are used as an example, numbered 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12. These 12 anchor cable fiber optic sensors are embedded into the slope at different depths and positions. The anchor cable fiber optic sensors are grouped according to their position and depth within the soil of the slope.

[0045] The anchor cable fiber optic sensors in the same group are embedded to the same depth in the soil of the slope, and the positions of each group are as follows: Figure 4As shown, in the first group of anchor fiber optic sensors numbered 1, 4, 9, and 12, the ends of the fiber optic sensors are fixed to the bottom end of the anchor cable; in the second group of anchor fiber optic sensors numbered 5 and 8, the ends of the fiber optic sensors are fixed 1m from the bottom end of the anchor cable; in the third group of anchor fiber optic sensors numbered 6 and 7, the ends of the fiber optic sensors are fixed 2m from the bottom end of the anchor cable; in the fourth group of anchor fiber optic sensors numbered 2 and 10, the ends of the fiber optic sensors are fixed 3m from the bottom end of the anchor cable; and in the fifth group of anchor fiber optic sensors numbered 3 and 11, the ends of the fiber optic sensors are fixed 4m from the bottom end of the anchor cable. The state of the anchor fiber optic sensors in the soil is as follows. Figure 3 As shown. The bottom end of the anchor cable represents the lowest point of the NPR anchor cable embedded in the soil. For example, if the NPR anchor cable is embedded 10 meters into the soil, and the ends of the fiber optic sensors on the first group of anchor cables numbered 1, 4, 9, and 12 are fixed at the bottom end of the anchor cable, then the depth of the fiber optic sensors embedded in the soil for the first group of anchor cables is 10 meters. If the ends of the fiber optic sensors on the second group of anchor cables numbered 5 and 8 are fixed 1 meter from the bottom end of the anchor cable, then the depth of the fiber optic sensors embedded in the soil for the second group of anchor cables is 9 meters.

[0046] It should be noted that, except for the first set of anchor cable fiber optic sensors, the depth of the NPR anchor cables differs from that of the anchor cable fiber optic sensors in other areas. The part where the fiber optic sensor is combined with the NPR anchor cable is the anchor cable fiber optic sensor itself. This fixes the anchor cable fiber optic sensor within the slope, facilitating three-dimensional monitoring of the slope and resulting in more accurate monitoring results.

[0047] Step S2: Use stress sensors to obtain the Newton force corresponding to each anchor cable fiber optic sensor, and perform fitting based on the Newton force to obtain the Newton force change curve corresponding to each anchor cable fiber optic sensor; determine the warning level based on the Newton force change curve corresponding to each anchor cable fiber optic sensor, and determine the judgment duration based on the warning level.

[0048] Before using fiber optic sensors for further monitoring, it is necessary to use Newtonian force monitoring to determine the current state of the slope in order to provide early warning.

[0049] After embedding the anchor cable fiber optic sensor into the soil of the slope, a stress sensor needs to be installed to detect changes in Newtonian force. The stress sensor is installed on the upper end face of each anchor cable fiber optic sensor, as shown in the diagram. Figure 3 As shown, the axial force of the NPR anchor cable in the anchor cable fiber optic sensor is measured and used as the Newton force corresponding to each anchor cable fiber optic sensor. The Newton force corresponding to each anchor cable fiber optic sensor is further fitted to obtain the Newton force variation curve corresponding to each anchor cable fiber optic sensor. It should be noted that the Newton force corresponding to each anchor cable fiber optic sensor is collected according to a preset sampling frequency.

[0050] Landslides, from their gestation to their eventual collapse, are a complex nonlinear process. The change in Newtonian force undergoes a gradual deformation stage, abrupt change stage, and a destructive movement stage. Therefore, the slope of the Newtonian force curve and the increment of Newtonian force are used as criteria to determine the warning level of the slope. Specifically, based on the change in Newtonian force, the warning level is divided into two levels. The first warning level is reached when the slope of the Newtonian force curve is greater than 0 or the increment of Newtonian force reaches 20-50 kN. The second warning level is reached when the slope of the Newtonian force curve reaches the inflection point between being greater than and less than 0, or when the increment of Newtonian force reaches 50-100 kN. A slope greater than 0 indicates a risk of landslide, requiring close monitoring.

[0051] Record the slope and increment of the Newton force curve. Obtain the slope and increment of the Newton force curve corresponding to each anchor cable fiber optic sensor. If the Newton force curve of any anchor cable fiber optic sensor meets the judgment condition of the first warning level, record the moment when the first warning level is reached as the judgment start time. When the judgment condition of the second warning level is met, record the moment when the second warning level is reached as the judgment end time. The time length between the judgment start time and the judgment end time is the judgment duration. It should be noted that the slope of the Newton force curve is calculated from the Newton force at two adjacent moments, and its increment is also calculated from the Newton force at two adjacent moments.

[0052] Thus, the slope condition is first analyzed using Newton's force, which is a preliminary warning, and then the anchor cable fiber optic sensor is used for detailed judgment.

[0053] Step S3: Obtain the strain value corresponding to each anchor fiber optic sensor at each moment within the judgment time; determine the location most likely to be a landslide based on the strain value corresponding to each anchor fiber optic sensor at each moment in each group of anchor fiber optic sensors.

[0054] In step S2, when the slope meets the first warning condition, more detailed monitoring is required using anchor cable fiber optic sensors. Specifically, at the start of the judgment, the strain of each anchor cable fiber optic sensor is measured at each moment using BOTDR technology until the end of the judgment. That is, within the judgment period, the strain of each anchor cable fiber optic sensor is measured at each moment using BOTDR technology to obtain the strain value corresponding to each anchor cable fiber optic sensor at each moment. Then, the strain values ​​corresponding to each anchor cable fiber optic sensor at each moment are analyzed.

[0055] The strain value corresponding to each anchor cable fiber optic sensor at each moment is denoted as S.t,i Let represent the strain value corresponding to the i-th anchor fiber optic sensor at time t; the strain velocity corresponding to the same anchor fiber optic sensor at each time is obtained based on the strain values ​​corresponding to the anchor fiber optic sensors at every two adjacent times, expressed by the formula:

[0056]

[0057] Among them, V t,i S represents the strain velocity corresponding to the fiber optic sensor of the i-th anchor cable at time t; t-1,i This represents the strain value corresponding to the i-th anchor cable fiber optic sensor at time t-1;

[0058] Furthermore, the strain value acceleration corresponding to the same anchor cable fiber optic sensor at each moment is:

[0059]

[0060] Among them, A t,i V represents the strain value and acceleration corresponding to the fiber optic sensor of the i-th anchor cable at time t; t-1,i This represents the strain velocity corresponding to the i-th anchor cable fiber optic sensor at time t-1.

[0061] The jerk of the strain value corresponding to the same fiber optic sensor for each anchor cable at each of two adjacent time points is obtained by using the acceleration of the strain value corresponding to the fiber optic sensor for that anchor cable at each time point, and is expressed by the formula:

[0062]

[0063] Among them, J t,i A represents the jerk of the strain value corresponding to the fiber optic sensor of the i-th anchor cable at time t; t-1,i This represents the strain value and acceleration corresponding to the i-th anchor cable fiber optic sensor at time t-1.

[0064] Furthermore, the average strain variability at each moment is obtained by averaging the strain variability of all anchor fiber optic sensors in each group at the same time. This represents the jerkiness of the average strain value at time t in a set of anchor cable fiber optic sensors.

[0065] Based on the variability of the average strain value at each moment corresponding to each group of anchor cable fiber optic sensors, a first curve corresponding to each group of anchor cable fiber optic sensors is obtained. In this embodiment of the invention, there are a total of 5 first curves. All the first curves are placed in the same coordinate system, and the groups of anchor cable fiber optic sensors corresponding to the two uppermost first curves are obtained, which are denoted as the first abnormal group and the second abnormal group. According to the depth corresponding to the anchor cable fiber optic sensors in the first abnormal group and the second abnormal group, the possible depth range of the landslide is determined. For example, if the first abnormal group and the second abnormal group are the first group of anchor cable fiber optic sensors and the second group of anchor cable fiber optic sensors, the depth range is 1-2m from the bottom end of the anchor cable.

[0066] Having determined the potential depth range of the slope, a more precise determination of the most likely landslide location is needed. This is achieved by fitting the strain values ​​of each anchor cable fiber optic sensor in the first and second anomaly groups at each moment, obtaining a second curve for each sensor in both groups. By placing all these second curves in the same coordinate system, the position of the anchor cable fiber optic sensor corresponding to the uppermost curve is identified as the most likely landslide location. Thus, the most likely landslide location can be determined.

[0067] When a landslide occurs, the Newtonian force suddenly drops. This means that timely landslide warnings can be issued by monitoring the abrupt change in Newtonian force. A Newtonian force monitoring system can continuously monitor the magnitude of the Newtonian force and provide initial warnings based on the measured values. While Newtonian force monitoring can provide timely initial warnings, it cannot pinpoint the exact location of a potential landslide based on changes in Newtonian force. Fiber optic cables can accurately detect the location of abnormal strain. The monitoring data from the fiber optic cable is the strain along the fiber optic cable, which, after data processing, can be reflected in the strain of the slope. When the Newtonian force reaches the first warning level, timely data analysis of the fiber optic sensors on the anchor cables can identify potential landslide points or surfaces. Timely measures at these points can minimize the risk of a landslide. To more accurately locate the sliding surface, a staggered fixing method using stepped fiber optic cables wound around NPR anchor cables is employed. The distance between the fiber optic sensors on each row of NPR anchor cables and the bottom end of the anchor cable varies. The location of the sliding surface is determined between the fiber optic sensors on the two anchor cables with the most significant numerical responses to the first curve.

[0068] Furthermore, based on the embodiments of the present invention, optical fibers can be distributed and laid on the surface of the slope. Further detection can be performed based on the optical fibers laid on the slope surface to monitor the strain of the slope surface. The intersection of the longitudinal displacement monitoring fiber and the lateral displacement monitoring fiber of the optical fiber sensor laid on the slope surface coincides with the anchoring position of the anchor cable. Figure 4As shown, by deploying optical fibers on the surface of the soil and rock mass, ensuring they conform to the deformation of the soil and rock mass, the deformation of the surface soil and rock mass on the slope can be monitored, enabling the monitoring of longitudinal and lateral strain on the slope surface. When the surface soil and rock mass slides, it will cause the sensing optical fiber to slide as well, resulting in axial strain due to tension in the sensing optical fiber. The strain of the optical fiber is measured using BOTDR technology, and more detailed early warnings are provided based on the measurement results.

[0069] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, the above description focuses on specific embodiments of this specification. Additionally, the processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired results. In some embodiments, multitasking and parallel processing are possible or may be advantageous.

[0070] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0071] 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, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A stepped slope monitoring method combining optical fiber and NPR anchor cable, characterized in that, The method includes: The fiber optic sensor is fixed to the NPR anchor cable in a preset manner to form an anchor cable fiber optic sensor. The anchor bolt fiber optic sensors are numbered sequentially. The numbered anchor cable fiber optic sensors are grouped according to their position and depth embedded in the soil of the slope. The numbered and grouped anchor cable fiber optic sensors are then fixed in the slope in three rows from top to bottom, with four horizontal intervals in each row. The sensors are grouped according to their position and depth embedded in the soil of the slope, including: the fiber optic sensor ends of the first group (1, 4, 9, 12) are fixed to the bottom end of the anchor cable; the fiber optic sensor ends of the second group (5, 8) are fixed 1 meter away from the bottom end of the anchor cable; the fiber optic sensor ends of the third group (6, 7) are fixed 2 meters away from the bottom end of the anchor cable; the fiber optic sensor ends of the fourth group (2, 10) are fixed 3 meters away from the bottom end of the anchor cable; and the fiber optic sensor ends of the fifth group (3, 11) are fixed 4 meters away from the bottom end of the anchor cable. The bottom end of the anchor cable is the lowest point of the part of the anchor cable embedded in the soil. The Newton force corresponding to each anchor cable fiber optic sensor is obtained by using a stress sensor, and the Newton force variation curve corresponding to each anchor cable fiber optic sensor is obtained by fitting based on the Newton force. The warning level is determined based on the Newton force change curve corresponding to each anchor cable fiber optic sensor, and the judgment duration is determined based on the warning level. Within the judgment time period, obtain the strain value corresponding to each anchor cable fiber optic sensor at each moment; The location most likely to be a landslide is determined based on the strain value of each anchor fiber optic sensor in each group at each moment.

2. The slope stepped monitoring method combining optical fiber and NPR anchor cable according to claim 1, characterized in that, The process of fixing the fiber optic sensor onto the NPR anchor cable in a preset manner to form an anchor cable fiber optic sensor includes: The NPR anchor cable includes internal reinforcing bars. The fiber optic sensor is uniformly wound around the surface of the internal reinforcing bars of the NPR anchor cable and fixed. The fiber optic sensor fixed to the surface of the internal reinforcing bars of the NPR anchor cable is encapsulated to form an anchor cable fiber optic sensor.

3. The slope stepped monitoring method combining optical fiber and NPR anchor cable according to claim 1, characterized in that, The method of obtaining the Newton force corresponding to each anchor cable fiber optic sensor using a stress sensor includes: Stress sensors are installed on the upper end face of each anchor fiber sensor to measure the axial force of the NPR anchor in the anchor fiber sensor, which is used as the Newton force corresponding to each anchor fiber sensor.

4. The slope stepped monitoring method combining optical fiber and NPR anchor cable according to claim 1, characterized in that, The step of determining the warning level based on the Newton force change curve corresponding to each anchor cable fiber optic sensor, and determining the judgment duration based on the warning level, includes: The warning levels are divided into two categories based on the change in Newtonian force. The first warning level is triggered when the slope of the Newtonian force change curve is greater than 0 or the increment of Newtonian force reaches 20-50 kN. The second warning level is triggered when the slope of the Newtonian force change curve reaches the inflection point between greater than and less than 0 or the increment of Newtonian force reaches 50-100 kN. The slope and increment of the Newtonian force change curve corresponding to each anchor cable fiber optic sensor are acquired. If the Newtonian force change curve corresponding to any anchor cable fiber optic sensor meets the criteria for the first warning level, the moment when the first warning level is reached is recorded as the start time of the judgment. When the criteria for the second warning level are met, the moment when the second warning level is reached is recorded as the end time of the judgment. The duration between the start time and the end time of the judgment is the judgment duration.

5. The slope stepped monitoring method combining optical fiber and NPR anchor cable according to claim 1, characterized in that, The acquisition of the strain values ​​corresponding to each anchor cable fiber optic sensor at each moment includes: The strain of each anchor cable fiber optic sensor at each moment is measured using BOTDR technology to obtain the corresponding strain value of each anchor cable fiber optic sensor at each moment.

6. The slope stepped monitoring method combining optical fiber and NPR anchor cable according to claim 1, characterized in that, The process of determining the most likely location of a landslide based on the strain value of each anchor fiber optic sensor in each group of anchor fiber optic sensors at each moment includes: The strain acceleration of the same fiber optic sensor at each time point is obtained by using the strain acceleration of the same fiber optic sensor at each time point; the strain jerk of the same fiber optic sensor at each time point is obtained by using the strain acceleration of the same fiber optic sensor at each time point; the average strain jerk of the same fiber optic sensor at the same time point in each group of fiber optic sensors is obtained by averaging the strain jerk of the same fiber optic sensor at each time point. Based on the jerk of the average strain value at each moment corresponding to each group of anchor fiber optic sensors, a first curve corresponding to each group of anchor fiber optic sensors is obtained; the groups of anchor fiber optic sensors corresponding to the two uppermost first curves are obtained and denoted as the first abnormal group and the second abnormal group; the depth range of possible landslide depth is determined according to the depth corresponding to the anchor fiber optic sensors in the first abnormal group and the second abnormal group. The strain values ​​of each anchor fiber optic sensor in the first and second anomaly groups at each time moment are fitted to obtain the second curve corresponding to each anchor fiber optic sensor; the position of the anchor fiber optic sensor corresponding to the uppermost second curve is obtained, which is the position where the landslide is most likely to occur.

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