CN117030131A - Underground mine water seepage monitoring method based on fiber bragg grating sensor - Google Patents
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Abstract
The application discloses an underground mine water seepage monitoring method based on a fiber bragg grating sensor, which comprises the following steps of: (1) Horizontally drilling holes in a water seepage easily-generated section of an underground mine, horizontally burying fiber bragg grating sensors in the holes, sealing the openings of the holes by adopting waterproof foam, and connecting the fiber bragg grating sensors with an oscilloscope system positioned outside the holes through cables; (2) In a period of time, the coating layer selects specific metal ions through chelation reaction, so that the concentration of the specific metal ions in the fiber grating section is continuously increased, the refractive index of the fiber grating section is changed, and the change of the concentration of the metal ions in the drilled hole is deduced through the change of the refractive index measured by the fiber grating sensor; (3) And calculating the permeation rate of the permeation water by combining the content of metal ions in the water quality water sample monitoring report. The application aims to monitor the water seepage phenomenon of the underground mine for a long time by monitoring the key position of the water seepage phenomenon of the underground mine.
Description
Technical Field
The application relates to the technical field of metal mine water seepage monitoring, in particular to an underground mine water seepage monitoring method based on a fiber bragg grating sensor.
Background
In recent years, with the continuous growth of population and the rapid development of industry, the national demand for metal ores having underground reserves is increasing, and exploitation of underground metal mines is also an important economic activity. However, the problems and challenges faced by underground metal mining are also becoming more and more complex and severe, and due to the complexity of the formation construction, the parameters of interest within the mine need to be monitored in order to ensure safe production of the metal mine during construction.
The mechanical property of surrounding rock and the path of groundwater runoff are easy to change when excavation is carried out in the mine, so that surrounding groundwater is gathered and accumulated in a mining area of the mine, and the problems of large deformation and water seepage are easy to occur. In the construction process of engineering projects, various mutation phenomena (such as cracking, dislocation and the like) occur in the internal structures of mines due to the change of natural conditions (such as underground water, materials, stratum, freeze thawing and the like), so that surrounding rock underground water or surface water directly or indirectly enters the walls of the holes of the mines in a seepage or gushing mode to form seepage diseases, erode the internal structures of the mines and influence the normal construction exploitation of the underground mine projects and the use of equipment in the holes. The water seepage problem of the underground mine is monitored, the most main monitoring parameters are the water seepage problem in the mine, the water seepage problem mainly comprises parameters such as water seepage quantity and seepage rate, and whether the seepage prevention treatment on the internal structure of the mine is needed is judged through the result analysis of the parameters.
At present, a method for monitoring the water seepage problem in the mine mainly adopts a method for monitoring a seepage sensor, holes are drilled at the position where water seepage is easy to occur, the seepage sensor is arranged in the holes, and if the water seepage phenomenon is detected, the water seepage amount is analyzed to judge whether an anti-seepage measure is needed to be adopted at the position. On one hand, the method simply adopts the means of manual monitoring and on-site investigation, which can lead to large workload, low efficiency and large interference by human factors, and can lead to great consumption of manpower and material resources; on the other hand, the seepage sensor is used for monitoring the seepage phenomenon in the mine cavity, in the area with a small seepage field, the seepage sensor has no obvious reading, the seepage phenomenon occurs due to slow erosion of underground water, once the seepage phenomenon occurs, the seepage phenomenon has a rapid spreading trend, and potential safety hazards can be left due to insufficient precision when the traditional seepage sensor is used. Therefore, a new monitoring technology is considered to realize the monitoring of the water seepage problem of the underground mine.
Disclosure of Invention
In order to overcome the defects of the prior art, the application aims to provide the underground mine water seepage monitoring method based on the fiber bragg grating sensor, which has the advantages of accurate measurement data, convenient operation and low manufacturing cost, and aims to monitor the key position of the underground mine water seepage phenomenon for a long time so as to monitor the underground mine water seepage phenomenon; meanwhile, the fiber bragg grating sensor is convenient to install, has little influence on the underground mine structure, and meets the safety requirement in the underground mine, so that the intelligent and informationized treatment on the underground mine water seepage problem is realized.
In order to achieve the above object, the present application adopts the following technical measures: an underground mine water seepage monitoring method based on a fiber bragg grating sensor comprises the following steps:
(1) Drilling holes in a water seepage easily-occurring section of an underground mine along the horizontal direction, horizontally burying fiber bragg grating sensors in the holes, sealing the openings of the holes by adopting waterproof foam, and connecting the fiber bragg grating sensors with an oscilloscope system positioned outside the holes through cables, wherein the oscilloscope system is used for displaying signals received by the fiber bragg grating sensors;
the fiber bragg grating sensor comprises a fiber bragg grating, wherein an inclined fiber bragg grating is arranged on the fiber bragg grating along the horizontal direction of the fiber bragg grating to form a fiber bragg grating zone; the periphery of the optical fiber core wound with the optical fiber Bragg grating is coated with an optical fiber cladding layer, and the periphery of the optical fiber cladding layer is coated with a coating layer;
(2) In a period of time, the coating layer selects specific metal ions through chelation reaction, so that the concentration of the specific metal ions in the fiber grating section of the inclined fiber Bragg grating is continuously increased, the refractive index of the fiber grating area is changed, and the change of the concentration of the metal ions in the drilled hole is deduced through the change of the refractive index measured by the fiber grating sensor;
(3) And calculating the permeation rate of the permeation water by combining the content of metal ions in the water quality water sample monitoring report.
Optionally, deriving the change in concentration of the metal ions in the borehole from the change in refractive index measured by the fiber bragg grating sensor in step (2) comprises:
(a) The incident light wave is incident into the fiber bragg grating area, then the emergent light wave enters the oscilloscope system, the oscillogram received by the fiber bragg grating at the moment is displayed through the oscilloscope system, and the central wavelength of the resonance loss peak is collected and recorded;
(b) In a solution with measurable concentration of metal ions in penetrating water in a metal mine, according to the Lorentz electron theory, electromagnetic field theory, lambert's law, definition of light intensity and beer's law, the corresponding relation between the concentration c and the refractive index n is expressed as:
wherein, gamma is the damping coefficient, omega 0 And ω is the natural frequency of the electron and the incident light frequency, α is a constant, e and m are the charge number and mass of the electron, μ 0 Is the dielectric constant of the medium and,n is the refractive index of the solution;
further analysis of equation (1) shows that when ω 0 When ω is unchanged, at a fixed wavelength, the correspondence between the concentration c and the refractive index n is approximately c=an+b, and a linear relationship is formed;
(c) Injecting water into the drill hole embedded with the fiber bragg grating sensor, recording the central wavelength of the resonance loss peak displayed by the oscilloscope system at the moment, and recording as lambda 1 The refractive index of the liquid at this time is n 1 ；
After a period of time, the center wavelength of the resonance loss peak is recorded as lambda 2 Record lambda 2 And lambda is 1 Data differential processing is carried out to obtain the drift amount of the center wavelength of the resonance loss peak, which is recorded as delta lambda m ；
Wherein Deltalambda m Indicating the shift amount of the resonance loss peak center wavelength, U ∞ Represents the incident light power lambda m Represents the center wavelength, Λ represents the fiber grating period, a represents the fiber cladding radius, n 1 Indicating the initial liquid refractive index, n 2 Indicating the refractive index of the cladding of the optical fiber, n 3 Indicating the refractive index of the liquid after the change;
(d) The drift delta lambda of the resonance loss peak center wavelength is obtained by carrying out data differential processing on the resonance loss peak center wavelength recorded twice m The shift delta lambda of the resonance loss peak center wavelength is calculated m Substituting into formula (2) to obtain the refractive index n of the liquid in the borehole 3 And (3) obtaining the metal ion concentration (mol/mL) in the fiber grating area wrapped by the coating layer at the moment according to the linear relation between the concentration and the refractive index obtained in the step (b), performing product treatment on the metal ion concentration (mol/mL) and the drilling capacity (mL), and dividing the product treatment by the time interval h of two measurements to obtain the change rate (mol/h) of the metal ion concentration.
Optionally, in step (3), the calculating the permeation rate of the permeation water according to the content of the metal ions in the water sample monitoring report includes: different metal ions have different molar masses (mg/mol), and the product of the different molar masses and the rate of change of the concentration of the metal ions (mol/h) can be expressed as (mg/h);
in a hydrogeological survey report before engineering construction, the content (mg/mL) of specific metal ions is obtained through water sample detection, the content (mg/mL) of specific metal ions is divided from the change rate (mg/h) of the concentration of specific metal ions, and then reciprocal treatment is carried out to obtain the permeation rate (mL/h) of permeated water.
Further, the time interval of the two recordings is controlled to be 12-36 h.
Further, the specific metal ion is an iron ion, and sulfosalicylic acid and the iron ion are selected for chelation reaction.
Furthermore, chitosan is selected as a raw material for manufacturing a coating layer, and a coating layer of chitosan with sulfosalicylic acid is coated on a sensing area of the fiber grating.
Preferably, the inclined fiber bragg grating is equidistantly spirally carved on the fiber core.
Compared with the prior art, the application has at least the following beneficial effects:
1. the traditional seepage sensor is used for measuring the seepage condition in the underground mine, on one hand, in the long-term use process, particularly in mine engineering, the seepage sensor is easy to be blocked, and the monitoring result is influenced; on the other hand, in the area with smaller seepage field, the seepage sensor cannot accurately read seepage flow, and the monitoring data has errors. When the fiber grating sensor is used for monitoring the water seepage condition of an underground mine, the fiber grating sensor is free from blockage and can be used for a long time, and the fiber grating sensor is more sensitive to the condition change of external light, so that the fiber grating sensor has the advantages of high durability, stable performance, high sensitivity and the like, and the result obtained by measuring the fiber grating sensor is more accurate than the result obtained by measuring the fiber grating sensor by using the seepage sensor.
2. For complex groundwater seepage in an underground mine, the seepage speed, the seepage path and the like are not single unchanged. The fiber bragg grating sensor provided with the inclined fiber bragg grating is more sensitive to wavelength deviation, so that the fiber bragg grating sensor is used for measuring the change of the refractive index of the underground water solution, the concentration change of metal ions can be deduced, the mine underground water seepage flow and the seepage speed are measured by the indirect method, and the quantitative and comprehensive seepage parameters of a certain key part of the underground mine can be rapidly and conveniently given.
3. The specific metal ions are selected by adopting a common chelating method in chemistry. Each metal ion has a corresponding chelating agent, and the chelating agent can perform corresponding chelation reaction with the metal ion to obtain chelate with special color. The specific metal ions can be selected by utilizing the chelation of the chelating agent to the specific metal ions. The method is mature and reliable, and can effectively ensure the linear relation between the concentration change of the solution and the seepage flow.
Drawings
In order to more clearly illustrate the embodiments of the application or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the application, and that other drawings can be obtained from these drawings without inventive faculty for a person skilled in the art.
FIG. 1 is a schematic diagram of the function of a fiber grating sensor according to the present application;
FIG. 2 is a schematic diagram of a fiber grating sensor according to the present application;
fig. 3 is a schematic layout diagram of a fiber bragg grating sensor provided by the application.
Reference numerals: 1-an optical fiber core; 2-optical fiber cladding; 3-coating film layer; 4-tilting the fiber bragg grating; 5-incident light waves; 6-emergent light waves; 7-oscilloscope system.
Detailed description of the preferred embodiments
In order that those skilled in the art will better understand the present application, a technical solution in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments. The components of the embodiments of the present application generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the application, as presented in the figures, is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present application without making any inventive effort, shall fall within the scope of the present application.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.
In the description of the present application, it should also be noted that, in this document, terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "transverse", "longitudinal", and the like indicate an azimuth or a positional relationship based on that shown in the drawings. These terms are only used to better describe the present application and its embodiments and are not intended to limit the scope of the indicated devices, elements or components to the particular orientations or to configure and operate in the particular orientations and therefore should not be construed as limiting the present application. The specific meaning of the above terms in the present application will be understood in specific cases by those of ordinary skill in the art.
Some embodiments of the present application are described in detail below with reference to the accompanying drawings. The following embodiments and features of the embodiments may be combined with each other without conflict.
As shown in fig. 1, in the schematic diagram of the function of the fiber grating sensor provided by the application, the change of the environment around the fiber grating sensor causes the corresponding change of the grating modulation matching phase, the corresponding change of the transmission light intensity spectrum causes the change of the refractive index, and the change of the concentration (water, air and photo-coal medium) of the external environment can be calculated according to the change rate. The medium for finishing one-time variation fluctuation, the modulation signal and the judgment of the variation rate mainly comprise three parts, namely an excitation light source (laser), a fiber grating sensor and an oscilloscope system. The excitation light source generated by the laser enters the optical fiber, enters the optical fiber grating sensor through optical fiber conduction, the optical fiber grating sensor is placed in an environment to be measured (liquid), the optical signal modulated by the optical fiber grating sensor is transmitted to the oscilloscope system through the optical fiber, when the concentration of surrounding substances (such as iron ion concentration) changes, the refractive index in the environment correspondingly changes, so that the change of the transmission spectrum intensity can be caused, and the change of the refractive index of the surrounding environment can be accurately reflected by combining a proper calibration technology. From the schematic diagram, the method for deducing the concentration change of the metal ions by measuring the change of the refractive index has feasibility.
As shown in fig. 2, the structure diagram of the fiber grating sensor provided by the application is shown, the fiber grating sensor comprises a fiber core 1, and an inclined fiber bragg grating 4 is arranged on the fiber core 1 to form a fiber grating area for detecting the incident light frequency of equal frequency; the periphery of the optical fiber core 1 wound with the optical fiber Bragg grating 4 is coated with the optical fiber cladding 2, and the periphery of the optical fiber cladding 2 is coated with the coating layer 4. The front section of the light inlet end of the fiber bragg grating sensor is provided with a laser which can generate an excitation light source with stable incident light power, an incident light wave 5 with stable power is incident into a fiber bragg grating area, and after passing through the inclined fiber bragg grating 4, an emergent light wave 6 enters an oscilloscope system 7, and the oscilloscope system 7 has an oscilloscope, and the central wavelength of a resonance loss peak is displayed. Specifically, the inclined fiber bragg grating 4 is spirally carved on the fiber core 1 at equal intervals, and the fiber cladding 2 plays a role in protecting the fiber core 1. The coating layer 3 can select specific metal ions through chelation reaction, taking iron ions as an example, the refractive index of the coating layer 3 is changed by an iron ion related chelating reactant generated by the chelation reaction, and the continuous accumulation of iron ion related chelates can finally cause the change of the resonance loss peak wavelength of emergent light. It should be emphasized that the coating is only one means of chemically modifying the cladding of the fiber, and its primary function is to alter the fiberThe core is used for restraining the light field, so that the input light reacts with the external environment, and the purpose of detecting the refractive index change is achieved. The continuous accumulation of the iron ion related chelating reactant in the coating layer 3 can lead the iron ion concentration in the fiber grating section of the inclined fiber Bragg grating 4 to be continuously increased, so the external refractive index can be changed, when the refractive index of the external environment is changed, the drift amount of the resonance loss peak center wavelength can directly pass through the change value delta lambda of the resonance loss peak center wavelength on the oscilloscope m Expressed by the formula:
wherein Deltalambda m Indicating the shift amount of the resonance loss peak center wavelength, U ∞ Represents the incident light power lambda m Represents the center wavelength, Λ represents the period of the tilted fiber Bragg grating, a represents the fiber cladding radius, n 1 Indicating the initial liquid refractive index, n 2 Indicating the refractive index of the cladding of the optical fiber, n 3 Indicating the refractive index of the liquid after the change.
Therefore, the refractive index of the liquid in the fiber grating area wrapped by the coating layer 3 at the moment can be obtained according to the drift amount of the resonance loss peak center wavelength, the metal ion concentration (mol/mL) in the fiber grating area wrapped by the coating layer 3 at the moment can be obtained according to the linear relation between the concentration and the refractive index obtained by the test before the monitoring operation is carried out, the product processing is carried out on the metal ion concentration (mol/mL) and the capacity (mL) of the drilled hole, and the change rate (mol/h) of the metal ion concentration can be obtained by dividing the measured time interval h. Since different metal ions have their specific molar masses (mg/mol), the product of the rate of change of the metal ion concentration (mol/h) can be expressed as (mg/h), i.e. the weight of metal ions (mg) collected per hour (h). Taking iron ions as an example, in a hydrogeological investigation report before engineering construction, the content (mg/mL) of the iron ions can be obtained through water sample detection, and the permeation rate (mL/h) of the permeated water can be obtained through reciprocal treatment after the content (mg/mL) of the iron ions is divided from the change rate (mg/h) of the concentration of the iron ions.
Example 1
An underground mine water seepage monitoring method based on a fiber bragg grating sensor, as shown in fig. 3, comprises the following steps:
(1) Drilling holes in a section, which is displayed in an underground mine investigation report and is prone to occurrence of groundwater, of a horizontal direction, horizontally burying an optical fiber grating sensor in the drilled holes, sealing the openings of the drilled holes by waterproof foam, connecting the optical fiber grating sensor with an oscilloscope system positioned outside the drilled holes through cables, displaying signals received by the optical fiber grating sensor by the oscilloscope system, and horizontally burying the optical fiber grating sensor so as to avoid the influence of penetrating water under the action of gravity, thus leading to larger monitoring data;
in the embodiment, taking iron ion detection as an example, sulfosalicylic acid is selected to carry out chelation reaction on the iron ion, and sulfosalicylic acid and the iron ion carry out chelation reaction to obtain a dark red chelate so as to achieve the detection purpose. The film coating layer is used for modifying the optical fiber sensing structure by selecting a gel film coating method, and the ion identification capability of the chelation reaction can directionally select iron ions, so that the capability is combined with the optical fiber grating sensing structure.
The embodiment provides a preparation method of a coating layer, which comprises the following steps: the chitosan has good stability and safety, so the chitosan is selected as a raw material for manufacturing a coating layer, the coating treatment is carried out on the sensing area of the fiber bragg grating, and the sensor can realize concentration detection on iron ions by utilizing a chelation reaction. The principle is that a chitosan coating layer with a chelating agent is coated on a sensing area of the fiber grating, after chelation reaction with iron ions, the refractive index of the chitosan coating layer is changed, and the continuous accumulation of the iron ion related chelation reactants can continuously increase the concentration of the iron ions in the coating layer, so that the resonance loss peak center wavelength of emergent light is influenced. In order to avoid the influence of falling off in the detection process caused by easy dissolution of chitosan in water, chitosan dissolved in sulfosalicylic acid is selected, and the concentration is regulated, so that the viscosity of chitosan solution is optimal, and a uniform film is formed on the surface of an optical fiber.
After the film is prepared, the embodiment proposes to adopt a baking method, firstly, a sufficient amount of film layer material is put on a glass slide, then the optical fiber core 1 of the optical fiber, the inclined optical fiber Bragg grating 4 and the optical fiber cladding 2 made of the polypropylene are completely immersed in the material, finally, the whole optical fiber cladding is put in a drying box, after the solution is completely dried, the solution is taken out, the redundant material beside the optical fiber is removed, and a thin and uniform film is obtained on the optical fiber, and the uniform film covered on the optical fiber sensing part is a film coating layer.
The seepage water of the underground metal mine is caused by the change of natural conditions and the like, and the change of the internal structure of the mine, so that the surrounding rock groundwater or surface water directly or indirectly enters the mine hole wall in a seepage or gushing mode to cause seepage diseases. The main components of the underground mine leakage water are the underground water existing in the construction section, the surface downward leakage water and the like, so that the leakage water of the underground mine contains metal ions of corresponding metal ores. In the report of the hydrogeology of the underground metal mine, the content of the relevant metal element can be obtained after the water quality analysis, if the fiber bragg grating sensor can be used for obtaining the change of the concentration of the metal ion through conversion by detecting the change of the refractive index, the change rate of the concentration of the metal ion can reflect the rate of water permeation.
The inclined fiber bragg grating 4 has a higher refractive index sensitivity, and after an incident light wave 5 with stable power generated by a laser enters the fiber core 1, if the density of an external environment solution of the section of the inclined fiber bragg grating 4 changes, the refractive index change caused by the change is reflected from the monitoring data of the inclined fiber bragg grating 4. The fiber grating region is an inclined fiber bragg grating 4 arranged in the horizontal direction of the fiber core, and the inclined fiber bragg gratings 4 are spirally arranged in the fiber grating region at equal intervals so as to detect the incident light frequency of equal frequency.
(2) The film coating layer 3 can select specific metal ions through chelation reaction within a period of time, so that the concentration of the metal ions in the fiber grating section of the inclined fiber Bragg grating 4 is continuously increased, the refractive index of the fiber grating area is changed, and the change of the refractive index is measured through the fiber grating sensor to deduce the concentration change of the metal ions in the fiber grating area wrapped by the film coating layer; the method comprises the following steps:
(a) The incident light wave is incident into the fiber grating area, and then the emergent light wave enters an oscilloscope system, and the oscilloscope system has the functions of displaying a waveform chart received by the fiber grating at the moment, and collecting and recording the center wavelength of a resonance loss peak;
(b) In an ideal case, the refractive index is fixed in the case of a relatively stable liquid concentration. The corresponding refractive index changes in the case of a change in the liquid concentration. In a solution with measurable concentration of metal ions in penetrating water in a metal mine, according to the lorentz electron theory, electromagnetic field theory, lambert law, definition of light intensity and beer's law, the corresponding relation between the concentration c and the refractive index n can be expressed as:
wherein, gamma is the damping coefficient, omega 0 And ω is the natural frequency of the electron and the incident light frequency, α is a constant, e and m are the charge number and mass of the electron, μ 0 Is the dielectric constant of the medium, n is the refractive index of the solution.
Further analysis of the above equation shows that when ω 0 When ω is unchanged, the correspondence between the concentration c and the refractive index n may be approximated as c=an+b in a linear relationship at a fixed wavelength.
Therefore, in the present application, the change in concentration can be reflected by detecting the change in refractive index based on the linear relationship between concentration and refractive index.
Taking one embodiment of the application as an example, sulfosalicylic acid is selected as a raw material to prepare a coating layer, the sulfosalicylic acid can carry out chelation reaction with iron ions, and the coating layer can carry out detection selection on the iron ions. It should be emphasized that for the detection of different metal ions, different coating layers need to be prepared, and the raw materials for preparing the coating layers are chemical substances capable of performing chelation reaction with the metal ions.
Before the monitoring work starts, the penetrating water containing iron ions in the metal mine is sampled, and refractive index experiments are carried out at different concentrations to determine the linear relation between the concentration and the refractive index in the penetrating water of the metal mine.
(c) Drilling a hole in a section to be measured according to the site situation of an underground mine, injecting water into the hole, recording the central wavelength of a resonance loss peak displayed by an oscilloscope at the moment, and recording as lambda 1 The refractive index of the liquid at this time is n 1 Is a known quantity; recording the central wavelength of resonance loss peak after a period of time, and recording as lambda 2 It should be emphasized that the time interval between the two recordings is not too long or too short, the error is easily increased due to too long time period, the variation is not obvious enough due to too short time period, and the control is preferably performed at 12h-36h, in this embodiment, 24h is taken as an example. Record lambda 2 And lambda is 1 The data difference processing is carried out to obtain the drift amount of the center wavelength of the resonance loss peak, which is recorded as delta lambda m 。
The coating layer 3 has a directional selection function, and the continuous accumulation of the iron ion related chelating reactant after the chelation reaction with the coating layer 3 in the coating layer 3 can lead the iron ion concentration in the fiber grating section of the inclined fiber Bragg grating 4 to be continuously increased, so the refractive index of the fiber grating region can be changed, and when the refractive index of the fiber grating region is changed, the refractive index of the fiber grating region is changed from n 1 Raised to n 3 When the shift amount of the resonance loss peak center wavelength can be expressed as:
wherein Deltalambda m Indicating the shift amount of the resonance loss peak center wavelength, U ∞ Represents the incident light power lambda m Represents the center wavelength, Λ represents the fiber grating period, a represents the fiber cladding radius, n 1 Indicating the initial liquid refractive index, n 2 Indicating the refractive index of the cladding of the optical fiber, n 3 Indicating the refractive index of the liquid after the change.
In the above formula, the refractive index n of the liquid after the change is removed 3 The remainder being known amounts.
(d) Resonance loss through two recordingsPeak consumption center wavelength lambda 1 And lambda is 2 The drift delta lambda of the center wavelength of the resonance loss peak can be obtained by performing data differential processing m The shift delta lambda of the resonance loss peak center wavelength is calculated m Substituting the liquid into the formula (2) to obtain the liquid refractive index n of the fiber grating region wrapped by the coating layer 3 3 According to the linear relation between the concentration and the refractive index obtained by the test before the monitoring work is carried out, the metal ion concentration (mol/mL) in the fiber grating area wrapped by the coating layer 3 at the moment can be obtained, the product processing is carried out on the metal ion concentration (mol/mL) and the drilling capacity (mL), and the change rate (mol/h) of the metal ion concentration can be obtained by dividing the product processing by the time interval h of two measurements.
(3) Calculating the permeation rate of permeation water by combining the content of metal ions in a water sample monitoring report; the method comprises the following steps: the different metal ions have different molar masses (mg/mol), so the product of the different metal ion concentrations (mol/h) and the product of the different metal ion concentrations (mol/h) can be expressed as (mg/h). Taking iron ions as an example, in a hydrogeological investigation report before engineering construction, the content (mg/mL) of the iron ions can be obtained through water sample detection, and the permeation rate (mL/h) of the permeated water can be obtained through reciprocal treatment after the content (mg/mL) of the iron ions is divided from the change rate (mg/h) of the concentration of the iron ions. After the rate is obtained, a field professional technician analyzes the data to determine whether the section needs to be subjected to anti-seepage treatment.
It is emphasized that the volume of the borehole (mL) during the calculation is the volume occupied by the removal of the waterproof foam sealed at the borehole opening, since the use of waterproof foam is required to seal the hole at the borehole opening.
The above description is only of the preferred embodiments of the present application and is not intended to limit the present application, but various modifications and variations can be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (7)
1. The underground mine water seepage monitoring method based on the fiber bragg grating sensor is characterized by comprising the following steps of:
(1) Drilling holes in a water seepage easily-occurring section of an underground mine along the horizontal direction, horizontally burying fiber bragg grating sensors in the holes, sealing the openings of the holes by adopting waterproof foam, and connecting the fiber bragg grating sensors with an oscilloscope system positioned outside the holes through cables, wherein the oscilloscope system is used for displaying signals received by the fiber bragg grating sensors;
the fiber bragg grating sensor comprises a fiber bragg grating, wherein an inclined fiber bragg grating is arranged on the fiber bragg grating along the horizontal direction of the fiber bragg grating to form a fiber bragg grating zone; the periphery of the optical fiber core wound with the optical fiber Bragg grating is coated with an optical fiber cladding layer, and the periphery of the optical fiber cladding layer is coated with a coating layer;
(2) In a period of time, the coating layer selects specific metal ions through chelation reaction, so that the concentration of the specific metal ions in the fiber grating section of the inclined fiber Bragg grating is continuously increased, the refractive index of the fiber grating area is changed, and the change of the concentration of the metal ions in the drilled hole is deduced through the change of the refractive index measured by the fiber grating sensor;
(3) And calculating the permeation rate of the permeation water by combining the content of metal ions in the water quality water sample monitoring report.
2. The method for monitoring water seepage in an underground mine based on a fiber bragg grating sensor according to claim 1, wherein the deriving the change of the concentration of the metal ions in the borehole from the change of the refractive index measured by the fiber bragg grating sensor in the step (2) comprises:
(a) The incident light wave is incident into the fiber bragg grating area, then the emergent light wave enters the oscilloscope system, the oscillogram received by the fiber bragg grating at the moment is displayed through the oscilloscope system, and the central wavelength of the resonance loss peak is collected and recorded;
(b) In a solution with measurable concentration of metal ions in penetrating water in a metal mine, according to the Lorentz electron theory, electromagnetic field theory, lambert's law, definition of light intensity and beer's law, the corresponding relation between the concentration c and the refractive index n is expressed as:
wherein, gamma is the damping coefficient, omega 0 And ω is the natural frequency of the electron and the incident light frequency, α is a constant, e and m are the charge number and mass of the electron, μ 0 Is the dielectric constant of the medium, n is the refractive index of the solution;
further analysis of equation (1) shows that when ω 0 When ω is unchanged, at a fixed wavelength, the correspondence between the concentration c and the refractive index n is approximately c=an+b, and a linear relationship is formed;
(c) Injecting water into the drill hole embedded with the fiber bragg grating sensor, recording the central wavelength of the resonance loss peak displayed by the oscilloscope system at the moment, and recording as lambda 1 The refractive index of the liquid at this time is n 1 ；
After a period of time, the center wavelength of the resonance loss peak is recorded as lambda 2 Record lambda 2 And lambda is 1 Data differential processing is carried out to obtain the drift amount of the center wavelength of the resonance loss peak, which is recorded as delta lambda m ；
Wherein Deltalambda m Indicating the shift amount of the resonance loss peak center wavelength, U ∞ Represents the incident light power lambda m Represents the center wavelength, Λ represents the fiber grating period, a represents the fiber cladding radius, n 1 Indicating the initial liquid refractive index, n 2 Indicating the refractive index of the cladding of the optical fiber, n 3 Indicating the refractive index of the liquid after the change;
(d) The drift delta lambda of the resonance loss peak center wavelength is obtained by carrying out data differential processing on the resonance loss peak center wavelength recorded twice m The shift delta lambda of the resonance loss peak center wavelength is calculated m Substituting into formula (2) to obtain the refractive index n of the liquid in the borehole 3 The concentration obtained according to step (b)And obtaining the linear relation between the degree and the refractive index, obtaining the concentration of metal ions in the fiber grating area wrapped by the coating layer at the moment, performing product processing on the concentration of the metal ions and the capacity of the drilled hole, and dividing the product processing by the time interval h of two measurements to obtain the change rate of the concentration of the metal ions.
3. The method for monitoring underground mine water seepage based on the fiber bragg grating sensor according to claim 1, wherein the calculating the permeation rate of the seepage water by combining the content of metal ions in the water sample monitoring report in the step (3) comprises the following steps: different metal ions have different molar masses, and the product of the molar masses and the change rate of the concentration of the metal ions can be expressed as the weight of the metal ions collected per hour;
in the hydrogeological survey report before engineering construction, the content of specific metal ions is obtained through water sample detection, the content of specific metal ions is divided by the change rate of the concentration of the specific metal ions, and then the reciprocal treatment is carried out to obtain the permeation rate of the permeated water.
4. A method for monitoring water seepage in an underground mine based on a fiber bragg grating sensor according to claim 3, wherein the time interval between the two recordings is controlled to be 12-36 h.
5. The method for monitoring underground mine water seepage based on the fiber bragg grating sensor according to claim 2, wherein the specific metal ion is an iron ion, and sulfosalicylic acid and the iron ion are selected for chelation reaction.
6. The underground mine water seepage monitoring method based on the fiber bragg grating sensor according to claim 5, wherein chitosan is selected as a raw material for manufacturing a coating layer, and a chitosan coating layer with sulfosalicylic acid is coated on a sensing area of the fiber bragg grating.
7. The fiber bragg grating sensor-based underground mine water seepage monitoring method according to claim 1, wherein the inclined fiber bragg gratings are spirally carved on the fiber cores at equal intervals.
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