CN110987039A - Method for testing damage depth of coal seam roof and floor after working face extraction - Google Patents
Method for testing damage depth of coal seam roof and floor after working face extraction Download PDFInfo
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- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35306—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement
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Abstract
The invention discloses a method for testing the damage depth of a coal seam roof and floor after stoping of a working face, which belongs to the technical field of safe stoping of the working face and comprises the following steps: s1: drilling construction; s2: the carrier tube is connected with the optical cable; s3: lowering the optical cable; s4: drilling and grouting; s5: protecting an optical fiber lead; s6: collecting data; s7: and (6) data processing. In the step S1, when the drilling position is selected, if the air passage is selected, the drilling is performed on the side of the coal pillar reserved near the previous working face, and in the step S1, the drilling construction parameters for the floor include a hole diameter of 91mm, a hole depth of 55m, and a drilling angle range of 30 ° to 60 °. According to the method, the damage depth of the bottom plate is measured by adopting the fixed point grating optical cable, so that the accuracy and the continuity of measurement can be improved, the problem that data cannot be measured after a working face is pushed due to the damage of a single optical fiber is solved, and the method is simple to operate, high in stability, accurate in measured data and worthy of popularization and application.
Description
Technical Field
The invention relates to the technical field of safe stoping of a working face, in particular to a method for testing the damage depth of a coal seam roof and a coal seam floor after stoping of the working face.
Background
With the development of mining technology and technology, coal mine production safety and high benefit are in the same line and are still concerned by people. With the advance of the working face, phenomena such as top plate fracture sinking and bottom bulging can occur. If the water-bearing layer is arranged above or below the coal seam and the damage range is large, the fracture can possibly conduct the water-bearing layer, and if a dredging measure is not made in time, water inrush accidents are possibly caused; when the coal seam group is mined, the upper coal seam and the lower coal seam are close to each other, after the upper coal seam is mined, the stress environment of the lower coal seam can be changed due to stress concentration of coal pillars reserved in the upper coal seam, and cracks penetrate through the top plate of the lower coal seam, so that the supporting difficulty is caused, and the safety production is threatened;
at present, a large number of experts and scholars at home and abroad carry out a great deal of research on the damage rule of the top plate and the bottom plate of the working face, and damage influence factors are obtained through means such as theoretical derivation, numerical value and experimental simulation and field actual measurement, wherein the damage range of the top plate and the bottom plate is the most important influence factor. The damage range of the top plate and the bottom plate in front of the working face can be proved by means of microseismic monitoring, drilling water injection, radon gas detection, borehole peeking, direct current method and the like. Zhang Ping Song et al used to lay distributed optical fibers and lay multiple collection substations in stoping roadways to monitor in real time and study the law of floor damage.
Although the method can measure the damage depth of the bottom plate, the means for measuring the damage depth of the bottom plate of the goaf are few, and even if the method can measure the damage depth of the bottom plate of the goaf, the method has certain limitation, and when a drill hole is drilled to penetrate through a crack and easily collapse, a camera is stained with dust and water, the drill hole is not clear enough, and the maximum damage depth cannot be accurately measured; compared with the ground in a coal mine, the underground coal mine has the advantages that conditions are complex, the geothermal energy is large in some areas, the stress is high, secondary stress disturbance exists after coal seam mining, surrounding rock deformation of a roadway is large, distributed optical fibers are prone to inaccurate measurement due to large temperature difference change in a complex stress environment, even damage is caused due to rock stratum fracture and movement, and the whole damage process of a top bottom plate cannot be measured continuously and accurately. Therefore, the method for testing the damage depth of the coal seam roof and floor after the working face is stoped is provided.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: how to solve the problem that the distributed optical fiber is easy to damage and the damage process can not be measured continuously, and provides a method for testing the damage depth of the coal seam roof and floor after the stoping of a working face.
The invention solves the technical problems through the following technical scheme, and the invention comprises the following steps:
s1: drilling construction
The construction is carried out by constructors according to actual geological conditions and technical requirements on site, the hole diameter is 91mm and the hole depth is 55m for a bottom plate, the drilling angle range can be selected within 30-60 degrees, the development height of three zones of a top plate is larger, the hole depth of the top plate is 150m, the hole diameter is 91mm, the drilling angle is 90 degrees, in order to ensure the accuracy of observation data and the smoothness of installation, hole cleaning and hole sweeping are carried out on the drilled hole, hole probing is carried out if necessary, and after the drilled hole is drilled, the next step is carried out in time to prevent hole collapse.
S2: PVC pipe and optical cable connection
Two ends of the fiber bragg grating string are respectively connected with two bundles of 150m (the top plate is 250m) communication optical fiber cables in series at the bottom, the communication optical fiber cables are respectively connected with a single-mode common jumper, the connection position is wrapped and protected by a thin hose, and the outside is wrapped and protected by a thin steel pipe; then test through the model for FBG-A03 demodulation appearance, verify whether the perfect connection of optic fibre and data are normal, fix 2m fixed point grating optical cable on the PVC pipe through the ribbon, adopt optical fiber splicer and butt fusion protection suit, it is firm to fix the armor optical cable and the PVC pipe that bottom fixed point grating optical cable connects with the sticky tape, do hole bottom optical cable and lead wire protection work, simultaneously at the bottom installation of PVC pipe form the toper guide head, and put down simultaneously grouting pipe ties up on the PVC pipe.
S3: optical cable lowering
Placing the PVC pipe with the optical cable fixed well into the drill hole, manually controlling the PVC pipe, and lowering the optical cable along the drill hole direction; when the optical cable is placed downwards, the fixed point grating optical cable is pre-stretched by about 2nm, the retraction amount of the optical cable can be measured after pre-stretching, if the optical cable is not stretched, the stretching amount can only be measured, then the sensing optical cable is bound and fixed at intervals of 1m, the position of the optical fiber welding position is encrypted, bound and fixed, and the fixed point grating is arranged on one side; and sequentially lowering the rest fixed point grating optical cables along with the lowering of the PVC pipe.
S4: drilling and grouting
After the optical cable is lowered, the hole can be sealed by adopting cement grouting with a water cement ratio of 1:1, so that cement paste reaches a viscous fluid state, continuous grouting is required during grouting to prevent the cement from solidifying, namely, the whole hole is fully sealed by one-time grouting, grouting is carried out by adopting a back grouting method, and a grouting pipe is left in the drilled hole after grouting.
S5: optical fiber lead protection
And (4) leading the orifice lead to a safety position in front of the drill hole by using an armored lead, marking, protecting the lead and cleaning the site. The armored optical cable is mainly different from a common optical fiber cable in that stainless steel braided wires are arranged in the outer protective sleeve, so that the armored optical cable can effectively resist pressure and torsion.
S6: collecting data
After the transfer is accomplished, use portable FBG demodulation appearance collection to transfer back data, show on the demodulation appearance can the normal use after, with measuring interface connection to monitoring station, then connect the pipe network, with data transmission to ground dispatch room.
S7: data processing
And processing the data according to a relation among strain, temperature and central wavelength, wherein the relation is as follows:
ΔλB＝αεε+αTΔT
wherein, αεFor fiber grating strain sensitivity coefficient, αTThe temperature sensitivity coefficient of the fiber grating, delta T is the temperature variation value, epsilon is the strain, lambdaBIs the center wavelength;
and obtaining a strain trend graph after processing, judging the elastic range and the plastic range according to the strain trend graph, then finding out a corresponding fixed point grating, and judging the damage vertical distance according to the distance between the fixed point grating and the orifice.
Furthermore, in step S1, when the drilling position is selected, if the air way is selected, the hydraulic support of the advance support is as close as possible to the side of the coal pillar reserved on the previous working face, so as to prevent the optical cable from being damaged by the hydraulic support of the advance support passing through the opening.
Furthermore, each optical cable of a fixed point grating optical cable packaged by the common optical fiber grating is connected with 8 maximum optical fiber grating points in series, the length of each fixed point grating optical cable is 16m, and the number of the fixed point grating optical cables and the number of the return leads required to be lowered in drilling are determined according to the actual design interval requirement and the drilling depth.
Furthermore, in step S2, it is determined that n fixed point grating optical cables need to be lowered for drilling, the fixed point grating optical cables are sequentially installed from bottom to top, and the fixed point gratings are installed on one side as much as possible, so as to ensure the consistency of the measurement direction and the accuracy of data; every fixed point grating optical cable all can connect two measurement interfaces, if somewhere in the middle of a certain optical cable damages, can adopt single line measuring mode, can not lead to whole optical cable to be unable to use because of somewhere optical cable damages. Even if two measuring interfaces of a single loop lead are damaged, n-1 loop leads can be normally measured, and the stability and the safety of the whole measuring system are greatly improved.
Furthermore, each loop lead is numbered sequentially from top to bottom, and the fixed point grating is also numbered sequentially from top to bottom.
Furthermore, before drilling, depth prediction is carried out on the coal seam floor damage depth by using a formula as a basis for selecting the drilling length, wherein the prediction formula is as follows:
h＝0.0085H+0.1665α+0.1079L-4.3579
where H is the height of the mined coal seam, L is the face length, and α is the coal seam inclination.
Further, in the step S7, the center wavelength λBIs calculated asB＝2neffΛ, wherein neffIs the effective index of refraction and Λ is the grating pitch.
Compared with the prior art, the invention has the following advantages: according to the method for testing the damage depth of the coal seam roof and the coal seam floor after the stoping of the working face, the damage depth of the floor is measured by adopting the fixed-point grating optical cable, the accuracy and the continuity of measurement can be improved, the problem that data cannot be measured after the working face is pushed due to the damage of a single optical fiber is solved, and the method is simple to operate, high in stability, accurate in measured data and worthy of popularization and use.
Drawings
FIG. 1 is a schematic diagram of the arrangement of the internal equipment of the borehole according to one embodiment of the present invention;
FIG. 2 is a schematic diagram of the positions of a coal seam, an air lane, a belt lane and a gob according to an embodiment of the present invention;
FIG. 3 is a schematic cross-sectional view taken along line A-A' of FIG. 2;
fig. 4 is a strain trend graph of the measurement data processing result in the second embodiment of the present invention.
In the figure: 1. drilling; 2. a loop lead; 3. PVC pipes; 4. 2m fixed point grating optical cable; 5. a grouting pipe; 6. and (6) binding the belt.
Detailed Description
The following examples are given for the detailed implementation and specific operation of the present invention, but the scope of the present invention is not limited to the following examples.
Example one
As shown in fig. 1 to 3, the present embodiment provides a technical solution: a method for testing the damage depth of a coal seam roof and a coal seam floor after working face extraction comprises the following steps:
s1: drilling construction
The construction is carried out by constructors according to actual geological conditions and technical requirements on site, the hole diameter is 91mm and the hole depth is 55m for a bottom plate, the drilling angle range can be selected within 30-60 degrees, the development height of three zones of a top plate is larger, the hole depth of the top plate is 150m, the hole diameter is 91mm, the drilling angle is 90 degrees, in order to ensure the accuracy of observation data and the smoothness of installation, hole washing and hole sweeping are carried out on a drill hole 1, hole probing is carried out if necessary, and after the drill hole 1 is drilled, the next step is carried out in time to prevent hole collapse.
S2: PVC tube (carrier tube) connected with optical cable
Two ends of the fiber bragg grating string are respectively connected with two bundles of 150m communication optical fiber cables in series at the bottom (a 150 m-specific bottom plate is adopted, and two bundles of 250m communication optical fiber cables are adopted for a top plate), the communication optical fiber cables are respectively connected with a single-mode common jumper, the connection position is protected by a thin hose, and the outside is protected by a thin steel pipe; then test through the model for FBG-A03 demodulation appearance, verify whether the perfect connection of optic fibre and data are normal, fix 2m fixed point grating optical cable 4 on PVC pipe 3 through ribbon 6, adopt optical fiber splicer and butt fusion protection suit, it is firm to fix bottom optical cable and PVC pipe 3 with the sticky tape, do the hole bottom optical cable and lead wire protection work, simultaneously at the installation of PVC pipe 3 bottom form the toper guide head, and put slip casting pipe 5 down when tying up on PVC pipe 3.
S3: optical cable lowering
Placing the PVC pipe 3 with the optical cable fixed well into the drill hole 1, manually controlling the PVC pipe 3, and lowering the optical cable along the direction of the drill hole 1; when the optical cable is placed downwards, the fixed point grating optical cable is pre-stretched by about 2nm, the retraction amount of the optical cable can be measured after pre-stretching, only the stretching amount can be measured without stretching, then the sensing optical cable is bound and fixed at intervals of 1m, the position of the optical fiber welding position is bound and fixed in an encrypted manner, and the fixed point grating is arranged on one side; and sequentially lowering the rest fixed point grating optical cables along with the lowering of the PVC pipe 3.
S4: drilling and grouting
After the optical cable is lowered, the hole sealing of the drill hole 1 can be realized by adopting cement grouting, the water cement ratio is 1:1, so that cement paste reaches a viscous fluid state, continuous grouting is needed during grouting to prevent the cement from solidifying, namely, the whole hole is fully sealed by one-time grouting, the grouting adopts a back grouting method, and the grouting pipe 5 is left in the drill hole 1 after the grouting.
S5: optical fiber lead protection
And (3) leading the orifice lead to a safety position in front of the drill hole 1 by using an armored lead, marking, protecting the orifice lead, preventing workers from doing other work and damaging the lead, and cleaning the site. The armored optical cable is mainly different from a common optical fiber cable in that stainless steel braided wires are arranged in the outer protective sleeve, so that the armored optical cable can effectively resist pressure and torsion.
S6: collecting data
After the transfer is accomplished, use portable FBG demodulation appearance collection to transfer back data, show on the demodulation appearance can the normal use after, with measuring interface connection to monitoring station, then connect the pipe network, with data transmission to ground dispatch room.
S7: data processing
And processing the data according to a relation among strain, temperature and central wavelength, wherein the relation is as follows:
ΔλB＝αεε+αTΔT
wherein, αεFor fiber grating strain sensitivity coefficient, αTThe temperature sensitivity coefficient of the fiber grating, delta T is the temperature variation value, epsilon is the strain, lambdaBIs the center wavelength; FBG (fiber Bragg Grating) not only can accurately measure the micro-deformation of the material, but also is not influenced by electromagnetic induction noise, has high measurement stress precision, is applied to a mining roadway, finds that the temperature change of the bottom plate and the top plate is extremely small according to the actual measurement on the site, and ignores the influence of the temperature change on the optical fiber during data processing;
and obtaining a strain trend graph after processing, judging the elastic range and the plastic range according to the strain trend graph, then finding out a corresponding fixed point grating, and judging the damage vertical distance according to the distance between the fixed point grating and the orifice.
In step S1, when the drilling position is selected, if the air way is selected, the hydraulic support of the advance support is as close as possible to the side of the coal pillar reserved on the previous working face, so as to prevent the optical cable from being damaged by the hydraulic support of the advance support passing through the hole.
In step S2, it is determined that n fixed point grating optical cables need to be lowered for drilling the hole 1, the fixed point grating optical cables are sequentially installed from bottom to top, and the fixed point gratings are installed on one side as much as possible, so as to ensure the consistency of the measurement direction and the accuracy of data; each fixed point grating optical cable is connected with two measuring interfaces, if a certain position in the middle of one optical cable is damaged, a single-line measuring mode can be adopted, and the whole optical cable cannot be used due to the damage of the certain optical cable; even if two measurement interfaces of a single loop lead 2 are damaged, n-1 loop leads 2 can be normally measured, and the stability and the safety of the whole measurement system are greatly improved.
Each loop lead wire 2 is numbered sequentially from top to bottom, and the fixed point grating is also numbered sequentially from top to bottom.
Before drilling 1, depth prediction is carried out on the coal seam floor damage depth by using a formula as a basis for selecting the drilling length, wherein the prediction formula is as follows:
h＝0.0085H+0.1665α+0.1079L-4.3579
where H is the height of the mined coal seam, L is the face length, and α is the coal seam inclination.
In the step S7, the center wavelength λBIs calculated asB＝2neffΛ, wherein neffIs the effective index of refraction and Λ is the grating pitch.
It should be noted that each string of optical cables of the fixed-point grating optical cable packaged by the common fiber grating is connected with 8 fiber grating points at maximum in series, the length of each fixed-point grating optical cable is 16m, and the number of the fixed-point grating optical cables and the number of the loop leads 2 which need to be lowered in the drill hole 1 are determined according to the actual design space requirement and the depth of the drill hole 1. As shown in fig. 1, three loop leads 2 are provided, each loop lead 2 corresponds to a measurable length of 16m, when the lowest end is installed, a fixed point grating optical cable is fixed by using an adhesive tape, after 8 fixed point gratings are installed, the loop leads 2 are fixed together, the density of a ribbon 6 can be properly increased, and the fixed point grating optical cable is ensured to be well contacted with a PVC pipe 3 and is not loosened; the second and third 16m loop leads 2 are installed by analogy, two measurement interfaces are arranged at two ends of an outer opening of each loop lead 2 and are divided into two groups, one group is commonly used, one group is standby and is connected to a monitoring station, and if a certain position of a fixed point grating of each loop lead 2 is damaged, the standby measurement interface can be adopted. If two interfaces of one loop lead 2 in the three loop leads 2 are damaged, the other two loop leads 2 can also be measured normally, and therefore the purpose of measuring discontinuous large deformation is achieved. In order to guarantee the optical cable survival rate, fixed point grating optical cable bottom adopts 5mm armor lead wire to be the synchronous extraction drill way of U type return circuit mode, and wherein the diameter phi of PVC pipe 3 is 50mm, installs the toper head of leading in 3 bottoms of PVC pipe simultaneously. Finally, the drill hole 1 is backfilled by adopting a grouting mode, as shown in figure 1. In order to facilitate the situation that the rear part of the goaf can be continuously monitored after the working face is pushed, the fiber bragg grating outgoing line is lengthened (the specific length can be determined according to the advance influence distance of the working face), and the fiber bragg grating outgoing line is led to a measuring station out of a safe position and is connected to the ground through an underground pipe network, so that real-time data monitoring is realized.
Example two
Taking keemun ore as an example: the influence of temperature on the optical fiber is firstly researched on the ground, and the strain sensitivity coefficient of the optical fiber grating is measured. Firstly, depth prediction is carried out on the damage depth of the bottom plate according to a formula, wherein the formula is as follows:
h＝0.0085H+0.1665α+0.1079L-4.3579
where H is the height of the mined coal seam, L is the face length, and α is the coal seam inclination.
The maximum mining depth of a certain working face of Kendong mine is 563.4m, the inclination angle is 7.1-13.8 degrees, the length of the working face is 166.5m, and the theoretical bottom plate destruction depth is 20.58m by substituting the formula.
The drilling depression angle is 60 degrees, the vertical depth is 30m, the corresponding hole length is 35m, the drilling length is 40m, the optical fiber adopts two groups (16) of fixed point gratings, the length of the hole is 40m, the outer part of the optical fiber is 160m, the two groups of optical fiber needs four lead wire armored cables, and the length of the optical fiber is 800 m.
The specific test method comprises the following steps:
(1) drilling construction: the construction is carried out by constructors according to actual geological conditions and technical requirements on site, aiming at that the aperture of a bottom plate is generally 91mm, the hole depth is 40m, the drilling angle is selected to be 60 degrees, (the development height of a top plate three zone is larger, the hole depth of the top plate is generally 150m), and considering the influence of advanced bearing pressure, an orifice is selected to be 120m away from a working surface; in order to ensure the accuracy of observation data and the smoothness of installation, the hole is washed and swept for the drilled hole, and the hole is explored if necessary; after drilling, the next step is carried out in time to prevent hole collapse.
(2) The PVC pipe is connected with the optical cable: two ends of the fiber bragg grating string are respectively connected with two bundles of 160m communication optical cables (the top plate is 250m) in series at the bottom, the communication optical fiber cables are respectively connected with a single-mode common jumper wire, the connection position is protected by a thin hose, and the outside is protected by a thin steel pipe. Then, testing by using a demodulator with the model of FBG-A03 to verify whether the optical fiber is perfectly connected and whether the data is normal; fixing the 2m fixed-point grating optical cable on a PVC pipe through a binding belt, adopting an optical fiber fusion splicer and a fusion protection sleeve, firmly fixing the bottom optical cable and the PVC pipe by using an adhesive tape, and performing hole bottom optical cable and lead protection work to prevent damage; and meanwhile, a conical guide head is formed at the bottom of the PVC pipe, and the grouting pipe is bound on the PVC pipe and is simultaneously placed downwards.
(3) Lowering the optical cable: and (4) placing the PVC pipe with the fixed optical cable into the drilled hole, artificially controlling the PVC pipe, and placing the optical cable along the drilling direction. When the optical cable is placed downwards, the fixed-point grating optical cable is pre-stretched by about 2nm and is bound by a binding belt and an adhesive tape in time; then binding and fixing the sensing optical cables at intervals of 1m, carrying out encryption binding and fixing on the position with the optical fiber welding position, and installing the fixed point grating on one side; and sequentially lowering the rest fixed point grating optical cables along with the lowering of the PVC pipe. The fixed point grating numbering sequence is from top to bottom, and the initial central wavelength of the optical fiber and the installation central wavelength after 2nm stretching are recorded in time.
(4) Grouting and hole sealing: after the optical cable is lowered, the hole can be sealed by adopting cement grouting with a water cement ratio of 1:1, so that cement paste reaches a viscous fluid state, continuous and uninterrupted grouting is needed during grouting to prevent the cement from solidifying, namely, the whole hole is fully sealed by one-time grouting, grouting is carried out by adopting a back grouting method, and a grouting pipe is left in the drilled hole after grouting; and after grouting is finished, sealing holes with yellow mud in time, wherein the sealing hole depth is 0.2m, so that the optical fibers are prevented from being damaged in the later bedding process.
(5) Protecting an optical fiber lead: and (4) leading the orifice lead to a safety position in front of the drill hole by using an armored lead, marking, protecting the lead and cleaning the site.
(6) Collecting and transferring data: after the transfer is accomplished, use portable FBG demodulation appearance collection to transfer back data, show can normal use after, with interface connection to monitoring station, then connect the pipe network, with data transmission to ground dispatch room.
(7) Data processing: and calculating to obtain the strain of the measured structure by utilizing the linear relation between the strain and the wavelength offset of the grating. The laboratory carries out temperature (20-80 ℃) to research the wavelength drift of the optical fiber, and the experiment shows that the strain sensitivity coefficient of the optical fiber grating is 0.01; according to the actual measurement of the temperature of the area, the gradient value of the temperature of the area is averagely 3 ℃/hundred meters, so that the temperature change does not exceed 2 ℃, the influence of the temperature change on the optical fiber is not considered, and the formula is simplified as follows:
ε＝K·(λ2-λ1)
wherein epsilon is strain, and the unit is mu epsilon; lambda [ alpha ]2Measuring the central wavelength of the fixed-point fiber bragg grating for the later period; lambda [ alpha ]1The central wavelength of the fiber bragg grating is initially fixed after installation; k is the optical fiber characteristic parameter, and the numerical value is 845.
As shown in FIG. 4, the X-axis is borehole length in m and the Y-axis is strain in μ ε.
(8) And (4) analyzing results: and (4) performing data processing according to the formula in the step (7), and as a result, as shown in fig. 4, performing synchronous coordinated deformation on the optical fiber and the surrounding rock after grouting, wherein the front and back data characteristics are represented as positive and negative transitions within a range of 24-26m away from the orifice according to a strain trend graph, namely, the transition of compressive strain and tensile strain is represented as the expression of elastic-plastic deformation of the rock body, and the elastic range and the plastic range are alternated here, the corresponding position sag is 20.87m, and the maximum failure depth can be obtained by combining the theory and is 20.87 m.
In summary, the methods for testing the damage depth of the coal seam roof and the bottom plate after the stoping of the working face in the two embodiments can improve the accuracy and the continuity of the measurement by adopting the fixed-point grating optical cable to measure the damage depth of the bottom plate, and solve the problem that data cannot be measured after the working face is pushed due to the damage of a single optical fiber.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (10)
1. A method for testing the damage depth of a coal seam roof and a coal seam floor after working face extraction is characterized by comprising the following steps:
s1: drilling construction
Drilling according to actual geological conditions and technical requirements on site, adopting an inclined drilling mode for a bottom plate and a vertical drilling mode for a top plate, washing and sweeping the drilled holes after the drilling construction is finished, and selecting whether to continue to perform hole probing on the drilled holes according to needs;
s2: connection of carrier tube to optical cable
Connecting two ends of the fiber bragg grating string with two bundles of communication optical fiber cables in series at the bottom respectively, connecting a single-mode common jumper wire to the communication optical fiber cables respectively, testing to verify whether the optical fibers are normally connected and whether data are normal, fixing the fixed-point fiber bragg grating cables on a carrier tube, binding a grouting tube on the carrier tube, and simultaneously putting the grouting tube into a drill hole;
s3: optical cable lowering
Placing a carrier tube with a fixed-point grating optical cable into a drilled hole, controlling the carrier tube to lower the fixed-point grating optical cable along the direction of the drilled hole, pre-stretching the fixed-point grating optical cable during lowering, binding and fixing the sensing optical cable at equal intervals, binding and fixing the positions of optical fiber fusion joints in an encrypted manner, arranging the fixed-point gratings at the same side, and sequentially lowering the rest fixed-point grating optical cables along with the lowering of the carrier tube;
s4: drilling and grouting
After the optical cable is lowered, hole sealing treatment is carried out on the drilled hole by cement grouting, continuous grouting is needed during grouting, grouting is carried out by adopting a slurry return method, and a grouting pipe is left in the drilled hole after grouting;
s5: optical fiber lead protection
Guiding the orifice lead to a safety position in front of the drill hole by using an armored lead, making marking and lead protection, and cleaning the site;
s6: collecting data
After the transfer is finished, collecting data after the transfer, connecting the measuring interface to a monitoring station, then connecting a pipe network, and transmitting the data to a ground dispatching room;
s7: data processing
And processing the data according to a relation among strain, temperature and central wavelength, wherein the relation is as follows:
ΔλB＝αεε+αTΔT
wherein, αεFor fiber grating strain sensitivity coefficient, αTThe temperature sensitivity coefficient of the fiber grating, delta T is the temperature variation value, epsilon is the strain, lambdaBIs the center wavelength;
and obtaining a strain trend graph after processing, judging the elastic range and the plastic range according to the strain trend graph, then finding out a corresponding fixed point grating, and judging the damage vertical distance according to the distance between the fixed point grating and the orifice.
2. The method for testing the damage depth of the coal seam roof and floor after the working face is stoped according to claim 1, which is characterized in that: before drilling, depth prediction is carried out on the damage depth of the coal seam floor by using a formula as a basis for selecting the drilling length, wherein the formula is as follows:
h＝0.0085H+0.1665α+0.1079L-4.3579
where H is the height of the mined coal seam, L is the face length, and α is the coal seam inclination.
3. The method for testing the damage depth of the coal seam roof and floor after the working face is stoped according to claim 1, which is characterized in that: in step S1, when the drilling position is selected, if the air passage is selected, the coal pillar side left on the previous face is drilled.
4. The method for testing the damage depth of the coal seam roof and floor after the working face is stoped according to claim 1, which is characterized in that: in the step S1, the drilling construction parameters for the bottom plate include an aperture of 91mm, a depth of hole of 55m, and a drilling angle range of 30 ° to 60 °, and the drilling construction parameters for the top plate include an aperture of 91mm, a depth of hole of 150m, and a drilling angle of 90 °.
5. The method for testing the damage depth of the coal seam roof and floor after the working face is stoped according to claim 1, which is characterized in that: in step S2, the connection between the single-mode ordinary jumper and the optical fiber cable is protected by wrapping with a thin hose, and then protected by wrapping with a thin steel tube.
6. The method for testing the damage depth of the coal seam roof and floor after the working face is stoped according to claim 1, which is characterized in that: in step S2, after the fixed-point grating optical cable is fixed on the carrier tube, an optical fiber fusion splicer and a fusion protection sleeve are used, and the armored optical cable connected to the bottom fixed-point grating optical cable is fixed to the carrier tube by using an adhesive tape.
7. The method for testing the damage depth of the coal seam roof and floor after the working face is stoped according to claim 1, which is characterized in that: in the step S2, the number of the fixed-point grating optical cables and the number of the loop leads required to be lowered in drilling are determined according to the actual design space requirement and the drilling depth, both ends of each loop lead are respectively provided with a measuring interface, and the carrier tube is a PVC tube.
8. The method for testing the damage depth of the coal seam roof and floor after the working face is stoped according to claim 7, which is characterized in that: each loop lead wire is numbered sequentially from top to bottom, and the fixed point grating is also numbered sequentially from top to bottom.
9. The method for testing the damage depth of the coal seam roof and floor after the working face is stoped according to claim 1, which is characterized in that: in the step S4, the drilling and sealing treatment adopts cement grouting with a water cement ratio of 1:1, so that the cement paste reaches a viscous fluid state, and the whole hole is fully sealed at one time.
10. The method for testing the damage depth of the coal seam roof and floor after the working face is stoped according to claim 1, which is characterized in that: in the step S7, the center wavelength λBIs calculated asB＝2neffΛ, wherein neffIs the effective index of refraction and Λ is the grating pitch.
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| CN114000919A (en) * | 2021-10-26 | 2022-02-01 | 中国矿业大学 | Method for determining reasonable distance of advance reinforcing support of working face stoping roadway |
| CN114858128A (en) * | 2022-04-22 | 2022-08-05 | 中煤科工生态环境科技有限公司 | Monitoring design method and device for overburden rock three-zone residual settlement in mining subsidence area |
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| WO2024093629A1 (en) * | 2023-06-13 | 2024-05-10 | 中国地质调查局南京地质调查中心(华东地质科技创新中心) | Optical fiber layout device and method for borehole measurement |
| CN116929237A (en) * | 2023-07-17 | 2023-10-24 | 安徽理工大学 | Application and use method of optical fiber in coal mine roof three-zone monitoring |
| CN116929237B (en) * | 2023-07-17 | 2024-04-12 | 安徽理工大学 | Application and use method of optical fiber in coal mine roof three-zone monitoring |
| CN117449902A (en) * | 2023-09-18 | 2024-01-26 | 中国矿业大学 | Stope roof overlying strata deformation damage height monitoring method |
| CN117449903A (en) * | 2023-09-18 | 2024-01-26 | 中国矿业大学 | Stope bottom plate damage depth monitoring method |
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