A catch type roof falling distribution type optical fiber monitoring sensor and roof damage degree calculation method

Abstract

The present application relates to a kind of card teeth type roof caving distribution type optical fiber monitoring sensor and roof damage degree calculation method, belong to geotechnical engineering safety monitoring technical field.The present application is along the longitudinal direction of roadway, and card teeth type roof caving distribution type optical fiber monitoring sensor is fixedly arranged on the roof rock matrix in monitoring area by fixed buckle;Distributed optical fiber light intensity signal is acquired, and the position of distributed optical fiber monitoring area is calibrated by the way of bending and changing light intensity;The light intensity signal of the calibrated distributed optical fiber monitoring area is converted into the strain information of each position on optical fiber by analysis demodulator;According to the strain variation curve evolution trend on distributed optical fiber, with the typical optical fiber monitoring response mode when different types of roof damage is fitted analysis, the roof deformation damage type is judged;According to the damage type of judgment, roof deformation damage schematic diagram is drawn, and according to the calculation formula under different damage mode, the roof damage degree is calculated.

Description

Technical Field

[0001] This invention relates to a toothed roof collapse distributed optical fiber monitoring sensor and a method for calculating the degree of roof damage, belonging to the field of geotechnical engineering safety monitoring technology. Background Technology

[0002] With the vigorous development of infrastructure construction, an increasing number of underground projects, such as underground tunnels, underground mines, and underground chambers, have been completed or are under construction. Excavating usable space within underground rock masses presents the most common type of disaster: roof collapse or slump. Roof collapses are generally caused by excessively exposed rock layers or overly fragmented rock masses, often resulting in large-scale, overall collapses. However, in underground spaces with poor support conditions, isolated rock fragments may also destabilize and fall, resulting in localized collapses. Whether large-scale or localized, roof collapses can easily endanger the safety of workers and machinery. Therefore, developing effective monitoring sensors and methods for calculating the degree of roof damage is of paramount importance for early warning and prevention of roof collapse accidents.

[0003] For underground excavated spaces such as mine roadways, mining areas, tunnels, and chambers, the exposed area often extends over a vast area ranging from several kilometers to tens of kilometers. Roof stability is not uniform throughout, and collapses can occur in unpredictable areas. Currently, common methods for monitoring roof collapse include: roof delamination meters, anchor stress gauges, microseismic monitoring, ultrasonic monitoring, and conductivity monitoring. Among these, delamination meters and anchor stress gauges are point-based monitoring methods, only able to monitor the displacement and stress changes at a specific point on the roof. When monitoring sensors are not properly arranged, collapse zones are easily missed, failing to effectively monitor the overall stability of the roof. Ultrasonic, conductivity, and microseismic monitoring methods are all indirect physical quantity monitoring; due to the complex lithology of the rock strata, they cannot directly reflect the actual response state of the roof, resulting in unstable monitoring effects and unreliable results.

[0004] Distributed fiber optic sensing technology is suitable for large-scale monitoring. Commonly used distributed fiber optic sensing technologies include: optical time-domain reflectometry and frequency-domain reflectometry (R / B-OTDR / OFDR) based on fiber Raman scattering or Brillouin scattering, polarized optical time-domain reflectometry (P-OTDR) based on fiber Rayleigh scattering, long-distance optical interferometry, and quasi-distributed fiber Bragg grating multiplexing technology.

[0005] Currently, there are few attempts to apply distributed optical fiber sensors to roof collapse monitoring. In most cases, they are buried in boreholes in the roof, which cannot achieve large-scale monitoring. In the rare cases where optical fibers are laid longitudinally along the roadway, they are often fixed with concrete spraying. On the one hand, this is not economical in terms of deployment cost. On the other hand, this commonly used double-clad distributed optical fiber is prone to detachment from the fiber core, which will lead to distorted monitoring results.

[0006] There are various forms of roof deformation / collapse. For block-shaped roof structures, tensile failure, shear slip failure, or a combination of tensile and slip failure may occur. For layered roof structures, flexural settlement deformation failure may occur. Although distributed optical fiber monitoring methods have been partially applied to roof deformation / collapse monitoring, the monitoring results have large errors, and the degree of roof damage cannot be directly analyzed and calculated based on the response results of roof deformation monitoring using distributed optical fibers. Summary of the Invention

[0007] This invention addresses the problem of large monitoring error and the inability to directly analyze and calculate the degree of damage to the roof in distributed optical fiber monitoring. It proposes a toothed distributed optical fiber monitoring sensor for roof fall and a method for calculating the degree of roof damage. This invention solves the problem of monitoring result distortion caused by the detachment of the fiber core from the outer cladding, and directly analyzes and calculates the degree of roof damage based on the response results of roof deformation monitored by distributed optical fiber.

[0008] A toothed roof fall distributed optical fiber monitoring sensor includes an optical fiber core 1, a tight sheath layer 2, and a loose sheath layer 4. The tight sheath layer 2 is fitted on the optical fiber core 1, and the outer surface of the optical fiber core 1 is uniformly provided with annular teeth 3. The loose sheath layer 4 is fitted on the annular teeth 3.

[0009] The tight cladding layer 2 is fixedly bonded to the outside of the optical fiber core 1 with a super strong adhesive, so that the tight cladding layer 2 and the optical fiber core 1 will not detach when subjected to huge shear force.

[0010] Preferred high-strength adhesives include: acrylic-modified epoxy resin adhesives, nano-reinforced epoxy resin adhesives, and two-component epoxy resin adhesives;

[0011] Unlike traditional smooth tight-fitting layers, the outer surface of tight-fitting layer 2 has a serrated structure, which is the annular retaining tooth 3.

[0012] The loose sleeve layer 4 is made of a flexible material, such as a soft rubber tube. The loose sleeve layer 4 is loosely nested with the annular retaining tooth 3, and the tight sleeve layer 2 and the loose sleeve layer 4 can slip off.

[0013] The method for calculating the degree of roof damage based on a toothed roof collapse distributed optical fiber monitoring sensor includes the following specific steps:

[0014] S1. Along the longitudinal direction of the roadway, the tooth-type roof collapse distributed optical fiber monitoring sensor is fixedly installed on the roof rock matrix in the monitoring area by a fixing buckle. The fixing buckle 5 includes an annular groove that matches the annular tooth 3 and an expansion screw 10. The annular tooth 3 is engaged with the annular groove of the fixing buckle 5.

[0015] When deploying distributed optical fiber monitoring sensors, drive the expansion screws 10 of the fixing buckle 5 into the roof rock matrix in the monitoring area, cut open the loose sleeve layer 4 at the fixing point of the distributed optical fiber monitoring sensor to expose the annular locking teeth 3, and then insert the annular locking teeth 3 into the annular groove of the fixing buckle 5.

[0016] S2. Acquire the distributed optical fiber intensity signal and determine the location of the distributed optical fiber monitoring area by changing the light intensity through bending;

[0017] S3. The light intensity signal of the calibrated distributed optical fiber monitoring area is converted into strain information at various locations on the optical fiber by analyzing the demodulator;

[0018] S4. Determine the type of deformation and failure of the top plate based on the evolution trend of the strain change curve on the distributed optical fiber;

[0019] S5. Based on the determined failure type, draw a schematic diagram of roof deformation and failure, and calculate the degree of roof failure according to the calculation formulas for different failure modes.

[0020] Step S4. Method for determining the type of roof deformation and failure: The strain change data along the entire length of the monitored optical fiber is fitted and analyzed with the typical optical fiber monitoring response modes for five types of roof failure. The type with the highest fitting coefficient is taken as the type of roof deformation and failure. Specifically,

[0021] Typical fiber optic monitoring response modes for five types of roof failure are as follows:

[0022] If the distributed optical fiber between adjacent fixed clips P1 and P2 undergoes uniform tensile deformation, while the distributed optical fiber outside fixed clips P1 and P2 remains undeformed, then the failure type of the top plate is tension failure, meaning that a tension crack appears in the middle of the top plate rock layer and the crack opening becomes larger and larger.

[0023] If the distributed optical fiber undergoes a sudden tensile deformation at a certain point between the adjacent fixed clips P1 and P2, and the deformation of other segments of the distributed optical fiber between fixed clips P1 and P2 is small, and the distributed optical fiber on the outer side of fixed clips P1 and P2 does not deform, then the failure type of the top plate is shear failure, that is, a shear crack appears in the middle of the top plate rock layer and the displacement of the rock mass on both sides of the crack increases.

[0024] The distributed optical fiber between adjacent fixed clips P1 and P2 exhibits three different forms of deformation: α, β, and γ. The α segment shows small deformation, the β segment shows a sudden increase in deformation, and the γ segment shows micro-deformation, with the deformation amount being less than that of the α segment. The distributed optical fiber on the outer side of fixed clips P1 and P2 remains undeformed. Therefore, the failure type of the roof is a tension-shear mixed failure type, that is, a crack appears in the middle of the roof rock layer, the crack opening increases, and the rock mass on both sides shifts. The α deformation is the deformation of the distributed optical fiber at the front of the sliding rock mass, the β deformation is the deformation of the distributed optical fiber at the corner of the rock mass, and the γ deformation is the deformation of the distributed optical fiber at the rear of the sliding rock mass.

[0025] The distributed optical fiber between adjacent fixed clips P1 and P2 exhibits five different forms of deformation: α, β, γ, δ, and ε. The deformation of segments α, γ, and ε is constant. The deformation of segment γ is less than that of segment α and less than that of segment ε. The deformation of segments β and δ suddenly increases. The distributed optical fiber on the outer side of fixed clips P1 and P2 is not deformed. Therefore, the failure type of the roof is a boulder fall, that is, a piece of rock in the roof strata slides down and falls.

[0026] If the distributed optical fiber between adjacent fixed clips P1 and P2 exhibits continuous arc-shaped tensile deformation, while the distributed optical fiber outside fixed clips P1 and P2 remains undeformed, then the failure type of the roof is bending failure, meaning that the entire roof rock layer undergoes subsidence and bending deformation.

[0027] The term "micro-deformation" refers to a deformation amount that does not exceed 0.1% of the length of the distributed optical fiber segment.

[0028] The term "small deformation" refers to a deformation amount of 0.1% to 0.5% of the length of the distributed optical fiber segment.

[0029] The term "large deformation" refers to a deformation exceeding 0.5% of the length of the distributed optical fiber segment.

[0030] The sudden increase in deformation refers to a deformation rate exceeding (0.5%) / cm along the fiber length;

[0031] The method for calculating the degree of damage to the top plate in step S5 is as follows:

[0032] For the tensile fracture failure mode of the roadway roof strata (such as...) Figure 5 The crack width Δx of the tension crack in the rock strata between the fixed clips P1 and P2 and the displacement Δy of the rock block can be calculated using the following formula:

[0033]

[0034] Wherein, P1P2 is the length of the optical fiber between clips P1 and P2 before deformation, and P′1P′2 is the length of the optical fiber between clips P1 and P2 after deformation.

[0035] For the fault failure mode of the roadway roof strata (such as...) Figure 6 The crack width Δx of the tension crack in the rock strata between the fixed clips P1 and P2 and the displacement Δy of the rock block can be calculated using the following formula:

[0036] or Where P1P2 is the length of the optical fiber between clips P1 and P2 before deformation, P′1P′2 is the length of the optical fiber between clips P1 and P2 after deformation, and ε max γ represents the maximum value of the local deformation of the optical fiber caused by the rock block slip angle, and γ is the deformation coefficient, which can be obtained from experimental testing.

[0037] For the mixed failure mode of tension and faulting of the roof strata in the roadway (such as...) Figure 7 The crack width Δx of the tension crack in the rock strata between the fixed clips P1 and P2 and the displacement Δy of the rock block can be calculated using the following formula:

[0038] or Where P1P2 is the length of the optical fiber between clips P1 and P2 before deformation, P′1P′2 is the length of the optical fiber between clips P1 and P2 after deformation, and ε max γ represents the maximum value of the local deformation of the optical fiber caused by the rock block slip angle, and γ is the deformation coefficient, which can be obtained from experimental testing.

[0039] For the failure mode of isolated rocks falling from the roof strata of the tunnel (such as...) Figure 8 The crack width Δx of the tension crack in the rock strata between the fixed clips P1 and P2 and the displacement Δy of the rock block can be calculated using the following formula:

[0040] or Where P1P2 is the length of the optical fiber between clips P1 and P2 before deformation, P′1P′2 is the length of the optical fiber between clips P1 and P2 after deformation, and ε max γ represents the maximum value of the local deformation of the optical fiber caused by the rock block slip angle, and γ is the deformation coefficient, which can be obtained from experimental testing.

[0041] For the bending and settlement failure mode of the roadway roof strata (such as...) Figure 9 The lateral range Δx of the rock strata's subsidence deformation and the maximum subsidence displacement Δy can be calculated using the following formulas:

[0042]

[0043] Wherein, P1P2 is the length of the optical fiber between clips P1 and P2 before deformation, and P′1P′2 is the length of the optical fiber between clips P1 and P2 after deformation.

[0044] The beneficial effects of this invention are:

[0045] (1) The present invention uses a toothed top plate to fix the distributed optical fiber monitoring sensor in the monitoring area by fixing buckles. Due to the presence of the teeth, the distributed optical fiber can withstand huge tensile force in the longitudinal direction, effectively avoiding the phenomenon of the fiber core and cladding slipping off under the action of large tensile force on the optical fiber, thus ensuring the monitoring accuracy of the distributed optical fiber sensor.

[0046] (2) The deployment method of the distributed optical fiber of the present invention abandons the traditional concrete spraying fixing method, which can save costs; the operation process is more convenient and effectively improves the deployment efficiency; and when the monitoring task is over, the buckle can be opened to recover the distributed optical fiber sensor without damage, which is conducive to the reuse of the sensor.

[0047] (3) The method of the present invention can directly and accurately determine the type of roof deformation and failure based on the evolution trend of the strain change curve on the distributed optical fiber, and analyze and calculate the degree of damage to the roof, which is conducive to the early warning and prevention of roof collapse disasters. Attached Figure Description

[0048] Figure 1 This is a toothed distributed fiber optic deformation sensor; a is the front view, b is the side view, and c is the perspective view.

[0049] Figure 2 Assembly diagram of a toothed distributed fiber optic deformation sensor and a fixing buckle;

[0050] Figure 3 This is a schematic diagram of the fixed buckle structure;

[0051] Figure 4 A schematic diagram of the distributed optical fiber layout for monitoring roof deformation in a tunnel.

[0052] Figure 5 The failure mode is tensile fracture of the roof strata of the tunnel.

[0053] Figure 6 The failure mode is characterized by the displacement of the roof strata in the tunnel.

[0054] Figure 7 The failure mode is a mixture of tensile and faulting failure of the roof strata of the tunnel.

[0055] Figure 8 The failure mode is characterized by isolated boulders falling from the roof strata of the tunnel.

[0056] Figure 9 The failure mode is characterized by bending settlement deformation of the roof strata in the tunnel.

[0057] In the diagram: 1-Fiber optic core, 2-Tight sheath layer, 3-Annular locking teeth, 4-Loose sheath layer, 5-Fixing buckle, 6-Roof rock layer of the tunnel, 7-Roof rock layer of the tunnel, 8-Locking tooth type distributed fiber optic sensor, 9-Surface, 10-Expansion screw. Detailed Implementation

[0058] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0059] Example 1: A toothed roof collapse distributed fiber optic monitoring sensor (see...) Figure 1 The fiber core 1, tight cladding 2, and loose cladding 4 are included. Tight cladding 2 is fitted onto fiber core 1. Annular retaining teeth 3 are evenly distributed on the outer surface of fiber core 1. Loose cladding 4 is fitted onto the annular retaining teeth 3. Tight cladding 2 is fixedly bonded to the outside of fiber core 1 with a super-strong adhesive, so that even when subjected to huge shear forces, tight cladding 2 and fiber core 1 will not detach.

[0060] Super strong adhesives include: acrylic modified epoxy resin, nano-reinforced epoxy resin adhesive, two-component epoxy resin adhesive, etc.

[0061] Unlike traditional smooth tight-fitting layers, the outer surface of tight-fitting layer 2 has a serrated structure, which is the annular retaining tooth 3.

[0062] The loose sleeve layer 4 is made of a flexible material, such as a soft rubber tube. The loose sleeve layer 4 is loosely nested with the annular retaining tooth 3, and the tight sleeve layer 2 and the loose sleeve layer 4 can slip off.

[0063] The method for calculating the degree of roof damage based on a toothed roof collapse distributed optical fiber monitoring sensor is as follows:

[0064] S1. Along the longitudinal direction of the roadway, the toothed roof collapse distributed fiber optic monitoring sensor is fixedly installed on the roof rock matrix within the monitoring area using fixing clips (see...). Figure 4 The fixing buckle 5 includes an annular groove that matches the annular teeth 3 and an expansion screw 10 (see...). Figure 3 The annular tooth 3 engages with the annular groove of the fixing buckle 5 (see...). Figure 2 Because the smooth surface of the fiber core cladding is prone to slippage when the optical fiber is subjected to large tensile forces, the toothed fixing method can greatly avoid this slippage and ensure monitoring accuracy.

[0065] When deploying distributed optical fiber monitoring sensors, drive the expansion screws 10 of the fixing buckle 5 into the roof rock matrix in the monitoring area, cut open the loose sleeve layer 4 at the fixing point of the distributed optical fiber monitoring sensor to expose the annular locking teeth 3, and then insert the annular locking teeth 3 into the annular groove of the fixing buckle 5.

[0066] The toothed distributed fiber optic sensor 8 is fixed to the bottom of each rock block in the top stratum 6 using a fixing clip 5 (see...). Figure 4 The roof strata of the tunnel may have already developed cracks or are about to develop cracks. Under the action of in-situ stress, the roof strata are in a stable equilibrium state. In order to effectively monitor the deformation response of each roof rock, it is necessary to set up fixed points on each rock block as much as possible. Even if some rock blocks are missed, that is, if no fixed points are set up on their surfaces, due to the full-length monitoring advantage of distributed optical fibers, when the rock blocks slide / fall, they will still come into contact with the distributed optical fibers and cause optical fiber response, and the falling position and sliding displacement of the rock blocks can be analyzed in reverse.

[0067] The specific deployment steps are as follows:

[0068] 1) Select the monitoring area based on the actual roof stability conditions on site;

[0069] 2) Statistically measure the length and width of the monitoring area, as well as the number of major rock blocks;

[0070] 3) Based on the length, width, and number of main rock blocks of the monitoring area, prepare sufficiently long toothed distributed optical fibers 8 and a sufficient number of fixing clips 5, and determine the installation position of the fixing clips 5 according to the width of the monitoring area and the number of rock blocks; when the width of the monitoring area is greater than the maximum rock block size, two or more rows of optical fibers can be laid.

[0071] 4) Drill holes at the locations on the top plate where the fixing clips 5 need to be installed, and insert plastic expansion shells into the holes to facilitate the installation of the fixing clips 5 in the next step.

[0072] 5) Align the expansion screw 10 of the fixing buckle 5 with the drill hole, and tighten the expansion screw 10 to fix the fixing buckle 5 to the top rock.

[0073] 6) Using the matching wire strippers or knife, strip the outermost layer of the toothed distributed optical fiber 8, i.e., the loose sheath layer 4, at the position aligned with the fixing buckle 5, so that the tight sheath layer 2 is exposed. Pry open the fixing buckle 5 and insert the exposed part of the tight sheath layer 2 of the distributed optical fiber into the slot of the fixing buckle.

[0074] 7) After inserting all the distributed optical fibers into the fixing clips 5, reserve a certain length of distributed optical fiber to connect to the distributed optical fiber demodulation analyzer to complete the sensor deployment.

[0075] S2. Acquire the distributed optical fiber intensity signal and determine the location of the distributed optical fiber monitoring area by changing the light intensity through bending;

[0076] S3. The light intensity signal of the calibrated distributed optical fiber monitoring area is converted into strain information at various locations on the optical fiber by analyzing the demodulator;

[0077] S4. Determine the type of roof deformation and failure based on the evolution trend of strain change curves on distributed optical fibers: Perform fitting analysis between the strain change data of the monitored optical fiber along the entire length and the typical optical fiber monitoring response modes for five types of roof failure, and take the one with the highest fitting coefficient as the type of roof deformation and failure.

[0078] Specifically, the typical fiber optic monitoring response modes for the five types of roof failure are as follows:

[0079] If the distributed optical fiber between adjacent fixed clips P1 and P2 undergoes uniform tensile deformation, while the distributed optical fiber outside fixed clips P1 and P2 remains undeformed, then the failure type of the top plate is tension failure, meaning that a tension crack appears in the middle of the top plate rock layer and the crack opening becomes larger and larger.

[0080] If the distributed optical fiber undergoes a sudden tensile deformation at a certain point between the adjacent fixed clips P1 and P2, and the deformation of other segments of the distributed optical fiber between fixed clips P1 and P2 is small, and the distributed optical fiber on the outer side of fixed clips P1 and P2 does not deform, then the failure type of the top plate is shear failure, that is, a shear crack appears in the middle of the top plate rock layer and the displacement of the rock mass on both sides of the crack increases.

[0081] The distributed optical fiber between adjacent fixed clips P1 and P2 exhibits three different forms of deformation: α, β, and γ. The α segment shows small deformation, the β segment shows a sudden increase in deformation, and the γ segment shows micro-deformation, with the deformation amount being less than that of the α segment. The distributed optical fiber on the outer side of fixed clips P1 and P2 remains undeformed. Therefore, the failure type of the roof is a tension-shear mixed failure type, that is, a crack appears in the middle of the roof rock layer, the crack opening increases, and the rock mass on both sides shifts. The α deformation is the deformation of the distributed optical fiber at the front of the sliding rock mass, the β deformation is the deformation of the distributed optical fiber at the corner of the rock mass, and the γ deformation is the deformation of the distributed optical fiber at the rear of the sliding rock mass.

[0082] The distributed optical fiber between adjacent fixed clips P1 and P2 exhibits five different forms of deformation: α, β, γ, δ, and ε. The deformation of segments α, γ, and ε is constant. The deformation of segment γ is less than that of segment α and less than that of segment ε. The deformation of segments β and δ suddenly increases. The distributed optical fiber on the outer side of fixed clips P1 and P2 is not deformed. Therefore, the failure type of the roof is a boulder fall, that is, a piece of rock in the roof strata slides down and falls.

[0083] If the distributed optical fiber between adjacent fixed clips P1 and P2 exhibits continuous arc-shaped tensile deformation, while the distributed optical fiber outside fixed clips P1 and P2 remains undeformed, then the failure type of the roof is bending failure, meaning that the entire roof rock layer undergoes subsidence and bending deformation.

[0084] S5. Based on the determined failure type, draw a schematic diagram of roof deformation and failure, and calculate the degree of roof failure according to the calculation formulas for different failure modes.

[0085] This invention directly determines the type of roof deformation and failure by observing the evolution trend of strain change curves on distributed optical fibers. Specifically, it analyzes the deformation / failure type and degree of the roof by examining the different response modes of distributed optical fiber monitoring results under different failure types. This solves the problem of unclear roof failure response in traditionally deployed distributed optical fibers.

[0086] Example 2: A method for calculating the degree of roof damage based on the distributed optical fiber monitoring sensor for roof collapse based on the toothed roof collapse method in Example 1. The specific steps are as follows:

[0087] The method for calculating the degree of roof damage based on a toothed roof collapse distributed optical fiber monitoring sensor is as follows:

[0088] S1. Along the longitudinal direction of the roadway, the toothed roof collapse distributed fiber optic monitoring sensor is fixedly installed on the roof rock matrix within the monitoring area using fixing clips (see...). Figure 4 The fixing buckle 5 includes an annular groove that matches the annular teeth 3 and an expansion screw 10 (see...). Figure 3 The annular tooth 3 engages with the annular groove of the fixing buckle 5 (see...). Figure 2 Because the smooth surface of the fiber core cladding is prone to slippage when the optical fiber is subjected to large tensile forces, the toothed fixing method can greatly avoid this slippage and ensure monitoring accuracy.

[0089] The toothed distributed fiber optic sensor 8 is fixed to the bottom of each rock block in the top stratum 6 using a fixing clip 5 (see...). Figure 4The roof strata of the tunnel may have already developed cracks or are about to develop cracks. Under the action of in-situ stress, the roof strata are in a stable equilibrium state. In order to effectively monitor the deformation response of each roof rock, it is necessary to set up fixed points on each rock block as much as possible. Even if some rock blocks are missed, that is, if no fixed points are set up on their surfaces, due to the full-length monitoring advantage of distributed optical fibers, when the rock blocks slide / fall, they will still come into contact with the distributed optical fibers and cause the optical fibers to respond, and the falling position and sliding displacement of the rock blocks can be analyzed in reverse.

[0090] S2. Acquire the distributed optical fiber intensity signal and determine the location of the distributed optical fiber monitoring area by changing the light intensity through bending;

[0091] S3. The light intensity signal of the calibrated distributed optical fiber monitoring area is converted into strain information at various locations on the optical fiber by analyzing the demodulator;

[0092] S4. Determine the type of roof deformation and failure based on the evolution trend of strain change curves on distributed optical fibers: Perform fitting analysis between the strain change data of the monitored optical fiber along the entire length and the typical optical fiber monitoring response modes for five types of roof failure, and take the one with the highest fitting coefficient as the type of roof deformation and failure.

[0093] Specifically, the typical fiber optic monitoring response modes for the five types of roof failure are as follows:

[0094] like Figure 5 As shown, when a tensile crack appears in the middle of the top stratum and the crack opening increases, the failure type of the top stratum is tensile failure. Because the fixing clips 5 on both sides of the crack isolate the deformation of other segments of the distributed optical fiber, the distributed optical fiber between adjacent fixing clips P1 and P2 undergoes uniform tensile deformation, while the distributed optical fiber outside fixing clips P1 and P2 remains undeformed. Figure 5 The deformation value of segment OA is almost zero, segment AB (distributed optical fiber between fixed clips P1 and P2) shows obvious uniform tensile deformation, and segment BC has a deformation value of almost zero. Conversely, based on the evolution trend of the strain change curve along the entire length of the distributed optical fiber, the failure type of the top plate is determined to be tension failure, that is, a tension crack appears in the middle of the top plate rock layer and the crack opening is getting larger and larger.

[0095] like Figure 6As shown, due to the severe compression of the distributed optical fiber by the edges of the sliding rock mass, a significant abrupt tensile deformation occurs in the distributed optical fiber at a certain point. The deformation of other segments between the two fixing clips 5 is slightly smaller, while the deformation of segments outside the fixing clips is almost zero. Therefore, the distributed optical fiber undergoes abrupt tensile deformation at a certain point between adjacent fixing clips P1 and P2. The deformation of other segments of the distributed optical fiber between fixing clips P1 and P2 is small, while the distributed optical fiber outside fixing clips P1 and P2 remains undeformed. Figure 6 The deformation value of segment OA is almost zero, the deformation value of segment AB is small, the deformation value of segment BC suddenly increases, the deformation value of segment CD is small, and the deformation value of segment DE is almost zero. Conversely, based on the evolution trend of the strain change curve along the entire length of the distributed optical fiber, it is determined that the failure type of the top plate is shear failure, that is, a shear crack appears in the middle of the top plate rock layer and the displacement of the rock mass on both sides of the crack becomes larger and larger.

[0096] like Figure 7 As shown, when a crack appears in the middle of the top stratum, and the crack opening increases while significant displacement occurs on both sides of the rock mass, the failure type of the top stratum is a tension-shear mixed failure. The tension of the rock mass will cause the distributed optical fibers at the crack tip to stretch, and the edges of the sliding rock mass will simultaneously and violently compress the distributed optical fibers, causing a significant abrupt tensile deformation at a certain point. The distributed optical fibers between adjacent fixed clips P1 and P2 exhibit three different forms of deformation: α, β, and γ. The α segment shows small deformation, the β segment shows a sudden increase in deformation, and the γ segment shows slight deformation, with the deformation amount of the γ segment being less than that of the α segment. The distributed optical fibers on the outer sides of fixed clips P1 and P2 remain undeformed. Figure 7 The deformation value of segment OA is almost zero, the deformation value of segment AB increases, the deformation value of segment BC suddenly jumps, the deformation value of segment CD is smaller than that of segment AB, and the deformation of segment DE is almost zero. Conversely, based on the evolution trend of the strain change curve along the entire length of the distributed optical fiber, it is determined that the failure type of the top plate is a tension-shear mixed failure type, that is, a crack appears in the middle of the top plate rock layer, the crack opening becomes larger and larger and the rock mass on both sides moves. α deformation is the deformation of the distributed optical fiber in the front section of the sliding rock mass, β deformation is the deformation of the distributed optical fiber at the edge of the rock mass, and γ deformation is the deformation of the distributed optical fiber at the rear end of the sliding rock mass.

[0097] like Figure 8As shown, when a rock in the top stratum without a fixed clip 5 slides down, the failure type of the top stratum is a boulder fall. Because the two sides of the sliding rock mass will severely compress the distributed optical fiber, the distributed optical fiber will experience significant abrupt tensile deformation at two points. The distributed optical fiber between these two points undergoes uniform tensile deformation. Between adjacent fixed clips P1 and P2, the distributed optical fiber exhibits five different deformation segments: α, β, γ, δ, and ε. The deformations of segments α, γ, and ε are constant. The deformation of segment γ is less than that of segment α, and the deformation of segment γ is less than that of segment ε. The deformations of segments β and δ suddenly increase. The distributed optical fiber outside fixed clips P1 and P2 remains undeformed. Figure 8 The deformation value of segment OA is almost zero, segment AB has a large deformation, segment BC has a sudden increase in deformation, segment CD has a small and constant deformation value, segment DE has a sudden increase in deformation, segment EF has a large deformation, and segment FG has an almost zero deformation value. Conversely, based on the evolution trend of the strain change curve along the entire length of the distributed optical fiber, the failure type of the top plate is determined to be the boulder fall type, that is, a piece of rock in the top plate rock layer slides down and falls.

[0098] like Figure 9 As shown, when the roof strata undergo overall subsidence and bending deformation, the failure type of the roof is bending failure. Since the subsidence deformation of the strata is continuous in the longitudinal direction, the distributed optical fibers in the subsided section will also undergo continuous and progressive tensile deformation. The distributed optical fibers between adjacent fixed clips P1 and P2 exhibit arc-shaped continuous tensile deformation, while the distributed optical fibers outside fixed clips P1 and P2 remain undeformed. Figure 8 The deformation values ​​in segments OA and CD are almost zero, the deformation curve in segment AB shows a continuous arc-shaped rise, and the deformation curve in segment BC shows a continuous arc-shaped fall. Conversely, based on the evolution trend of the strain change curve along the entire length of the distributed optical fiber, the failure type of the top plate is determined to be bending failure, that is, the entire top plate rock layer undergoes subsidence and bending deformation.

[0099] S5. Based on the determined failure type, draw a schematic diagram of roof deformation and failure; calculate the degree of roof failure according to the calculation formulas for different failure modes.

[0100] The calculation method for the degree of damage to the roof slab is as follows:

[0101] For the tensile fracture failure mode of the roadway roof strata (such as...) Figure 5 The crack width Δx of the tension crack in the rock strata between the fixed clips P1 and P2 and the displacement Δy of the rock block can be calculated using the following formula:

[0102]

[0103] Wherein, P1P2 is the length of the optical fiber between clips P1 and P2 before deformation, and P′1P′2 is the length of the optical fiber between clips P1 and P2 after deformation.

[0104] For the fault failure mode of the roadway roof strata (such as...) Figure 6 The crack width Δx of the tension crack in the rock strata between the fixed clips P1 and P2 and the displacement Δy of the rock block can be calculated using the following formula:

[0105] or

[0106] Where P1P2 is the length of the optical fiber between clips P1 and P2 before deformation, P′1P′2 is the length of the optical fiber between clips P1 and P2 after deformation, and ε max γ represents the maximum value of the local deformation of the optical fiber caused by the rock block slip angle, and γ is the deformation coefficient, which can be obtained from experimental testing.

[0107] For the mixed failure mode of tension and faulting of the roof strata in the roadway (such as...) Figure 7 The crack width Δx of the tension crack in the rock strata between the fixed clips P1 and P2 and the displacement Δy of the rock block can be calculated using the following formula:

[0108] or Where P1P2 is the length of the optical fiber between clips P1 and P2 before deformation, P′1P′2 is the length of the optical fiber between clips P1 and P2 after deformation, and ε max γ represents the maximum value of the local deformation of the optical fiber caused by the rock block slip angle, and γ is the deformation coefficient, which can be obtained from experimental testing.

[0109] For the failure mode of isolated rocks falling from the roof strata of the tunnel (such as...) Figure 8 The crack width Δx of the tension crack in the rock strata between the fixed clips P1 and P2 and the displacement Δy of the rock block can be calculated using the following formula:

[0110] or Where P1P2 is the length of the optical fiber between clips P1 and P2 before deformation, P′1P′2 is the length of the optical fiber between clips P1 and P2 after deformation, and ε max γ represents the maximum value of the local deformation of the optical fiber caused by the rock block slip angle, and γ is the deformation coefficient, which can be obtained from experimental testing.

[0111] For the bending and settlement failure mode of the roadway roof strata (such as...) Figure 9 The lateral range Δx of the rock strata's subsidence deformation and the maximum subsidence displacement Δy can be calculated using the following formulas:

[0112]

[0113] Wherein, P1P2 is the length of the optical fiber between clips P1 and P2 before deformation, and P′1P′2 is the length of the optical fiber between clips P1 and P2 after deformation.

[0114] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for calculating the roof failure degree based on the toothed roof caving distribution type optical fiber monitoring sensor, characterized in that, The toothed top plate fall distributed optical fiber monitoring sensor includes an optical fiber core (1), a tight-closing layer (2) and a loose-closing layer (4). The tight-closing layer (2) is fitted on the optical fiber core (1). The outer surface of the optical fiber core (1) is uniformly provided with annular teeth (3). The loose-closing layer (4) is fitted on the annular teeth (3). The method for calculating the degree of damage to the roof slab includes the following specific steps: S1. Along the longitudinal direction of the roadway, the tooth-shaped roof collapse distributed fiber optic monitoring sensor is fixedly installed on the roof rock matrix in the monitoring area by a fixing buckle. The fixing buckle includes an annular groove that matches the annular tooth and an expansion screw. The annular tooth engages with the annular groove of the fixing buckle. S2. Acquire the distributed optical fiber intensity signal and determine the location of the distributed optical fiber monitoring area by changing the light intensity through bending; S3. The light intensity signal of the calibrated distributed optical fiber monitoring area is converted into strain information at various locations on the optical fiber by analyzing the demodulator; S4. Determine the type of deformation and failure of the top plate based on the evolution trend of the strain change curve on the distributed optical fiber; the method for determining the type of deformation and failure of the top plate is as follows: If the distributed optical fiber between adjacent fixed clips P1 and P2 undergoes uniform tensile deformation, while the distributed optical fiber outside fixed clips P1 and P2 remains undeformed, then the failure type of the top plate is tension failure, meaning that a tension crack appears in the middle of the top plate rock layer and the crack opening becomes larger and larger. If the distributed optical fiber undergoes a sudden tensile deformation at a certain point between the adjacent fixed clips P1 and P2, and the deformation of other segments of the distributed optical fiber between fixed clips P1 and P2 is small, and the distributed optical fiber on the outer side of fixed clips P1 and P2 does not deform, then the failure type of the top plate is shear failure, that is, a shear crack appears in the middle of the top plate rock layer and the displacement of the rock mass on both sides of the crack increases. The distributed optical fiber between adjacent fixed clips P1 and P2 exhibits three different forms of deformation: α, β, and γ. The α segment shows small deformation, the β segment shows a sudden increase in deformation, and the γ segment shows micro-deformation, with the deformation amount being less than that of the α segment. The distributed optical fiber on the outer side of fixed clips P1 and P2 remains undeformed. Therefore, the failure type of the roof is a tension-shear mixed failure type, that is, a crack appears in the middle of the roof rock layer, the crack opening increases, and the rock mass on both sides shifts. The α deformation is the deformation of the distributed optical fiber at the front of the sliding rock mass, the β deformation is the deformation of the distributed optical fiber at the corner of the rock mass, and the γ deformation is the deformation of the distributed optical fiber at the rear of the sliding rock mass. The distributed optical fiber between adjacent fixed clips P1 and P2 exhibits five different forms of deformation: α, β, γ, δ, and ε. The deformation of segments α, γ, and ε is constant. The deformation of segment γ is less than that of segment α and less than that of segment ε. The deformation of segments β and δ suddenly increases. The distributed optical fiber on the outer side of fixed clips P1 and P2 is not deformed. Therefore, the failure type of the roof is a boulder fall, that is, a piece of rock in the roof strata slides down and falls. If the distributed optical fiber between adjacent fixed clips P1 and P2 exhibits continuous arc-shaped tensile deformation, and the distributed optical fiber outside fixed clips P1 and P2 does not deform, then the failure type of the top plate is bending failure, that is, the entire top plate rock layer undergoes subsidence and bending deformation. S5. Based on the determined failure type, draw a schematic diagram of roof deformation and failure, and calculate the degree of roof failure according to the calculation formulas for different failure modes.

2. The method for calculating the degree of roof damage based on a toothed roof collapse distributed optical fiber monitoring sensor according to claim 1, characterized in that: Step S5. Calculation method for the degree of damage to the roof slab: For the tensile fracture failure mode of the roadway roof strata, the crack width of the tensile crack in the strata between fixed clamps P1 and P2 is... and rock block displacement Calculate according to the following formula: ； in, The length of the optical fiber before deformation between clips P1 and P2. The length of the optical fiber after deformation between clips P1 and P2; For the fault failure mode of the roof strata in the roadway, the crack width of the tensile crack in the strata between fixed clamps P1 and P2 is... and rock block displacement Calculate according to the following formula: ,or ; in, The length of the optical fiber before deformation between clips P1 and P2. The length of the fiber optic cable after deformation between clips P1 and P2. This represents the maximum value of the local deformation of the optical fiber caused by the rock block slip angle. The deformation coefficient is obtained from experimental testing. For the mixed failure mode of tension and displacement of the roof strata in the roadway, the crack width of the tension crack in the strata between fixed clamps P1 and P2 is... and rock block displacement Calculate according to the following formula: ,or ; in, The length of the optical fiber before deformation between clips P1 and P2. The length of the fiber optic cable after deformation between clips P1 and P2. This represents the maximum value of the local deformation of the optical fiber caused by the rock block slip angle. The deformation coefficient is obtained from experimental testing. For the failure mode of isolated rockfall in the roof strata of the tunnel, the width of the tension crack in the rock strata between fixed clamps P1 and P2 is... and rock block displacement Calculate according to the following formula: ,or ; in, The length of the optical fiber before deformation between clips P1 and P2. The length of the fiber optic cable after deformation between clips P1 and P2. This represents the maximum value of the local deformation of the optical fiber caused by the rock block slip angle. The deformation coefficient is obtained from experimental testing. For the bending settlement failure mode of the roadway roof strata, the lateral range of the strata undergoing subsidence deformation and the maximum subsidence displacement of rock strata Calculate according to the following formula: ； in, The length of the optical fiber before deformation between clips P1 and P2. The length of the optical fiber after deformation between clips P1 and P2.

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