CN113916794A - Soil water content monitoring device and method based on ultra-weak fiber bragg grating sensing technology - Google Patents
Soil water content monitoring device and method based on ultra-weak fiber bragg grating sensing technology Download PDFInfo
- Publication number
- CN113916794A CN113916794A CN202111202903.4A CN202111202903A CN113916794A CN 113916794 A CN113916794 A CN 113916794A CN 202111202903 A CN202111202903 A CN 202111202903A CN 113916794 A CN113916794 A CN 113916794A
- Authority
- CN
- China
- Prior art keywords
- ultra
- soil
- fiber grating
- weak fiber
- water content
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/30—Assessment of water resources
Landscapes
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Pit Excavations, Shoring, Fill Or Stabilisation Of Slopes (AREA)
- Testing Or Calibration Of Command Recording Devices (AREA)
Abstract
A soil water content monitoring device and method based on an ultra-weak fiber grating sensing technology relate to the technical field of slope soil state monitoring. The invention aims to solve the problem that the water content of the surface layer and the deep layer of a soil body cannot be monitored in a distributed manner in real time in the slope safety protection monitoring. The water vapor outside the shell of each monitoring unit can permeate into the shell of each monitoring unit, the separation base divides the cavity inside the shell into an upper soil containing cavity and a lower temperature compensation cavity which are not communicated with each other, one end of the ultra-weak fiber grating is connected with the fiber grating demodulator, the other end of the ultra-weak fiber grating sequentially penetrates through the shells of the N monitoring units from top to bottom, the ultra-weak fiber grating is fixedly connected with each separation base and the top and the bottom of each shell, the upper computer collects the wavelength of the ultra-weak fiber grating in each monitoring unit obtained by the fiber grating demodulator in the measured time period, and the water content of the soil inside the upper soil containing cavity in each monitoring unit in the measured time period is respectively calculated by utilizing the wavelength.
Description
Technical Field
The invention belongs to the technical field of monitoring of the soil state of a side slope, and particularly relates to a monitoring technology of the water content of the soil of the side slope.
Background
Landslide hazard is a natural disaster, and mainly refers to a disaster caused by the fact that rock mass or soil mass loses the original balance state under the action of gravity and slides down along a whole or a local slope along a potential weak structural plane. When landslide disasters occur in roads, railways, villages and other places with frequent human activities, the landslide disasters can cause damage to infrastructures and houses on a light basis, and a great amount of casualties on a heavy basis. Research has shown that rainfall is one of the main causes of landslide disasters. The effect of rainfall to the landslide is a dynamic process, and rainwater infiltration soil body can increase the water content of soil body, increase soil body unit weight, causes the soil body to soften, and then leads to soil body shear strength to reduce. Therefore, the distributed real-time monitoring of the water content of the slope soil body is carried out, and the method has important significance for mastering the stable state of the slope soil body.
Most of the existing methods for monitoring the water content of the soil body of the side slope are methods for monitoring the water content of the soil body on the surface of the side slope, and the methods for monitoring the water content of the soil body in the deep layer of the side slope are few. Although several existing methods for monitoring the water content of the deep soil body of the side slope can monitor the water content of the deep soil body, the calibration process of a sensor is complex, the single acquisition time of data is long, and the real-time monitoring on the water content of the deep soil body cannot be realized.
Disclosure of Invention
The invention provides a soil water content monitoring device and method based on an ultra-weak fiber grating sensing technology, aiming at solving the problem that the water content of the surface layer and the deep layer of a soil body cannot be monitored in a distributed manner in real time in the slope safety protection monitoring.
The soil water content monitoring device based on the ultra-weak fiber bragg grating sensing technology comprises N monitoring units, an ultra-weak fiber bragg grating 4, a fiber bragg grating demodulator 6 and an upper computer, wherein N is a positive integer greater than or equal to 1,
each monitoring unit includes: the water vapor outside the shell 1 can permeate into the shell 1, the separation base 5 is positioned inside the shell 1 and divides the cavity inside the shell 1 into an upper soil containing cavity 2 and a lower temperature compensation cavity 3 which are not communicated with each other, the separation base 5 can move up and down inside the shell 1, the upper soil containing cavity 2 is used for containing dry soil,
one end of the ultra-weak fiber grating 4 is connected with the wavelength signal input end of the fiber grating demodulator 6, the other end of the ultra-weak fiber grating 4 sequentially penetrates through the shells 1 of the N monitoring units from top to bottom, so that the N monitoring units are connected in series, the ultra-weak fiber grating 4 is fixedly connected with each separation base 5 and the top and the bottom of the shell 1,
the upper computer is used for collecting the wavelength of the ultra-weak fiber bragg grating 4 in each monitoring unit obtained by the fiber bragg grating demodulator 6 in the measured time period, and the water content of the soil in the upper soil accommodating cavity 2 in each monitoring unit in the measured time period is calculated respectively by utilizing the wavelength of the ultra-weak fiber bragg grating 4 in each monitoring unit.
Furthermore, the part of the ultra-weak fiber grating 4 located in the upper soil accommodating cavity 2 is used for collecting the wavelength value of the ultra-weak fiber grating 4 under the influence of the soil weight, and the part of the ultra-weak fiber grating 4 located in the lower temperature compensation cavity 3 is used for collecting the wavelength value of the ultra-weak fiber grating 4 under the influence of the soil temperature.
Further, the water content omega of the soil inside the upper soil containing cavity 2 in the measured time period in one monitoring unit is calculated according to the following formula:
wherein λ and Δ λ are respectively the initial wavelength value and the wavelength variation value of the ultra-weak fiber grating 4 in the upper soil accommodating cavity 2 in the measured time period, λTAnd Δ λTRespectively the initial wavelength value and the wavelength variation value of the ultra-weak fiber grating 4 in the lower temperature compensation cavity 3 in the measured time period, E is the elastic modulus of the ultra-weak fiber grating 4, A is the sectional area of the ultra-weak fiber grating 4, and P is the sectional area of the ultra-weak fiber grating 4eIs the effective elastic-optical coefficient of the ultra-weak fiber grating 4, m is the mass of the dry soil in the upper soil accommodating cavity 2, and g is a gravity constant.
A soil water content monitoring method based on an ultra-weak fiber grating sensing technology is realized based on a soil water content monitoring device, and the soil water content monitoring device comprises: n monitoring units and an ultra-weak fiber grating 4, wherein N is a positive integer greater than or equal to 1,
each monitoring unit includes: the water vapor outside the shell 1 can permeate into the shell 1, the separation base 5 is positioned inside the shell 1 and divides the cavity inside the shell 1 into an upper soil containing cavity 2 and a lower temperature compensation cavity 3 which are not communicated with each other, the separation base 5 can move up and down inside the shell 1, the upper soil containing cavity 2 is used for containing dry soil,
the ultra-weak fiber grating 4 sequentially penetrates through the shells 1 of the N monitoring units from top to bottom, so that the N monitoring units are connected in series, the ultra-weak fiber grating 4 is fixedly connected with each separation base 5 and the top and the bottom of the shell 1,
the soil water content monitoring method comprises the following steps:
n monitoring units connected in series are placed in the soil of a tested area along the vertical direction, the wavelength of the ultra-weak fiber grating 4 in each monitoring unit in the tested time period is collected by a fiber grating demodulator 6,
and respectively calculating the water content of the soil in the upper soil accommodating cavity 2 in each monitoring unit in the measured time period by using the wavelength of the ultra-weak fiber bragg grating 4 in each monitoring unit.
Further, the water content omega of the soil inside the upper soil containing cavity 2 in the measured time period in one monitoring unit is calculated according to the following formula:
wherein λ and Δ λ are respectively the initial wavelength value and the wavelength variation value of the ultra-weak fiber grating 4 in the upper soil accommodating cavity 2 in the measured time period, λTAnd Δ λTRespectively the initial wavelength value and the wavelength variation value of the ultra-weak fiber grating 4 in the lower temperature compensation cavity 3 in the measured time period, E is the elastic modulus of the ultra-weak fiber grating 4, A is the sectional area of the ultra-weak fiber grating 4, and P is the sectional area of the ultra-weak fiber grating 4eIs the effective elastic-optical coefficient of the ultra-weak fiber grating 4, m is the mass of the dry soil in the upper soil accommodating cavity 2, and g is a gravity constant.
Further, the method for obtaining the formula for calculating the water content omega of the soil comprises the following steps:
establishing a relation among delta lambda, strain delta epsilon of the ultra-weak fiber grating 4 in the measured time period and the variation delta T of the temperature in the lower temperature compensation cavity 3 in the measured time period:
wherein alpha is the expansion coefficient of the ultra-weak fiber grating 4, zeta is the thermo-optic coefficient of the ultra-weak fiber grating 4,
the expressions Δ ∈ and Δ T are respectively:
wherein, the Delta m is the variation of the quality of the dry soil in the upper soil accommodating cavity 2 in the measured time period,
substituting the expressions of Δ ε and Δ T into formula one to obtain the relationship between Δ m and Δ λ:
the relationship between the water content of the soil, ω, and Δ λ, is:
the soil water content monitoring device and method based on the ultra-weak fiber bragg grating sensing technology can monitor the surface layer water content and the deep layer water content of the side slope soil body, can realize distributed monitoring on the water content of the side slope soil body, are flexible in sensor arrangement mode, and are suitable for side slopes with obvious influence of rainfall on stability. The monitoring device can be calibrated and packaged in a laboratory, and can be directly installed on site, so that the installation and the layout are simple; the soil water content monitoring data can be displayed in real time through software, and the real-time monitoring performance is good. And the ultra-weak fiber bragg grating is packaged, the change of the soil mass quality caused by the change of the water content of the soil mass is measured in real time, the real-time water content of the soil mass is calculated, and the monitoring method is simple and practical.
Drawings
Fig. 1 is a schematic structural diagram of a soil water content monitoring device based on an ultra-weak fiber grating sensing technology.
Fig. 2 is a schematic diagram of the arrangement of the soil water content monitoring device in a certain slope region.
Fig. 3 is a monitored soil moisture profile for a slope.
Detailed Description
In recent years, the ultra-weak fiber grating sensing technology has the capability of multiplexing on a large number of optical fibers, has the same monitoring precision as that of a common grating, is concerned by scholars at home and abroad, and has a good monitoring effect in many projects needing large-range long-distance monitoring. The central wavelength of the ultra-weak fiber grating is influenced by strain and temperature, and the strain change value and the temperature change value have a linear relation with the wavelength change value of the ultra-weak fiber grating, so that the strain and the temperature can be monitored. By specially packaging the ultra-weak fiber grating, various physical quantities can be monitored, such as moisture field monitoring, gas field monitoring, chemical field monitoring and the like. In addition, the ultra-weak fiber grating has low cost and is suitable for large-range and long-distance monitoring. Therefore, based on the characteristic that the soil mass quality changes when the water content of the soil mass with a certain mass changes, the invention monitors the water content of the soil mass in real time by monitoring the change of the ultra-weak fiber bragg grating wavelength value caused by the change of the soil mass quality, thereby effectively acquiring the change condition of the water content of the soil mass on the whole or local surface layer and the deep layer of the side slope and providing effective monitoring data for the evaluation of the stability of the side slope. The specific implementation method is as follows.
The first embodiment is as follows: specifically describing the embodiment with reference to fig. 1, the soil water content monitoring device based on the ultra-weak fiber grating sensing technology in the embodiment includes N monitoring units, an ultra-weak fiber grating 4, a fiber grating demodulator 6 and an upper computer, where N is a positive integer greater than or equal to 1.
Each monitoring unit includes: a housing 1 and a partition base 5. Separate base 5 and be located 1 inside of shell and separate into the upper soil that each other does not communicate with the inside cavity of shell and hold chamber 2 and lower floor's temperature compensation chamber 3, separate base 5 and can reciprocate in 1 inside of shell, and upper soil holds chamber 2 and is used for the dry soil of splendid attire. The dry soil is in-situ soil of the dried tested area. The casing 1 allows moisture on the outside thereof to permeate into dry soil inside the upper soil accommodating chamber 2.
The part of the ultra-weak fiber grating 4, which is positioned in the upper soil accommodating cavity 2, is used for collecting the wavelength value of the ultra-weak fiber grating 4 under the influence of the soil weight; the part of the ultra-weak fiber grating 4, which is positioned in the lower temperature compensation cavity 3, is used for collecting the wavelength value of the ultra-weak fiber grating 4 under the influence of soil temperature.
The one end of super weak fiber grating 4 links to each other with the wavelength signal input of fiber grating demodulator 6, and the other end of super weak fiber grating 4 is from last to running through N monitor cell's shell 1 down in proper order for N monitor cell establishes ties, and super weak fiber grating 4 passes through fixing device 7 respectively with every top and the bottom fixed connection of separating base 5, shell 1.
Because the ultra-weak fiber grating 4 has the advantage of massive multiplexing on one optical fiber, 20000 monitoring units can be multiplexed generally, 10000 monitoring units can be connected in series on one ultra-weak fiber grating 4. In practical application, a plurality of monitoring units can be connected in series at required intervals of minimum 10cm to form a soil water content monitoring string, hereinafter referred to as a monitoring string for short, so as to meet the distributed monitoring requirements of the water content of the surface layer and the deep layer of the slope. And a plurality of monitoring strings are uniformly distributed in one area, so that distributed monitoring of one area can be realized.
The upper computer is used for collecting the wavelength of the ultra-weak fiber grating 4 in each monitoring unit obtained by the fiber grating demodulator 6 in the measured time period, and the wavelength specifically comprises: the initial wavelength value lambda and the wavelength change value delta lambda of the ultra-weak fiber grating 4 in the upper soil accommodating cavity 2 in the measured time period, and the ultra-weak fiber grating 4 in the lower temperature compensation cavity 3 in the measured time periodInitial wavelength value lambdaTAnd a wavelength variation value Delta lambdaT。
The upper computer is also used for respectively calculating the water content omega of the soil in the upper soil accommodating cavity 2 in each monitoring unit in the measured time period by utilizing the wavelength of the ultra-weak fiber bragg grating 4 in each monitoring unit according to the following formula:
wherein E is the elastic modulus of the ultra-weak fiber grating 4, A is the sectional area of the ultra-weak fiber grating 4, PeIs the effective elastic-optical coefficient of the ultra-weak fiber grating 4, m is the mass of the dry soil in the upper soil accommodating cavity 2, and g is a gravity constant.
In this embodiment, when water vapor permeates into the upper soil through the shell 1 and holds in the cavity 2 during dry soil, the upper soil holds the quality of soil in the cavity 2 and will increase, and then the base 5 moves down is separated in the oppression. Because the ultra-weak fiber grating 4 is fixedly connected with each separation base 5 and the top and the bottom of the shell 1 respectively, when the separation base 5 moves downwards, the length of the ultra-weak fiber grating 4 in the upper soil accommodating cavity 2 is lengthened, so that the wavelength is changed. Meanwhile, if temperature changes occur, the ultra-weak fiber grating 4 in the lower temperature compensation cavity 3 also changes the wavelength due to the temperature changes.
In the embodiment, the ultra-weak fiber bragg grating is packaged into a device suitable for distributed real-time monitoring of the water content of the slope soil, hereinafter referred to as a monitoring device for short, and the distributed real-time monitoring of the water content of the surface layer and the deep layer of the slope soil is realized by connecting a plurality of monitoring devices in series. When the water content of the soil body is not changed, the wavelength value of the ultra-weak fiber grating is kept unchanged; when the water content of the soil body changes, the wavelength value of the ultra-weak fiber grating changes correspondingly. The ultra-weak fiber grating demodulator demodulates the wavelength change value of the ultra-weak fiber grating, and the distributed real-time monitoring of the soil water content is realized according to the relation between the soil water content and the wavelength change value of the ultra-weak fiber grating.
The second embodiment is as follows: in the soil water content monitoring method based on the ultra-weak fiber grating sensing technology according to the embodiment, first, the soil water content monitoring method is implemented based on a soil water content monitoring device, and the soil water content monitoring device includes: n monitoring units and an ultra-weak fiber grating 4, wherein N is a positive integer greater than or equal to 1.
Each monitoring unit includes: a housing 1 and a partition base 5. Separate base 5 and be located 1 inside of shell and separate into the upper soil that each other does not communicate with the inside cavity of shell and hold chamber 2 and lower floor's temperature compensation chamber 3, separate base 5 and can reciprocate in 1 inside of shell, and upper soil holds chamber 2 and is used for the dry soil of splendid attire. The dry soil is in-situ soil of the dried tested area. The casing 1 allows moisture on the outside thereof to permeate into dry soil inside the upper soil accommodating chamber 2.
The part of the ultra-weak fiber grating 4, which is positioned in the upper soil accommodating cavity 2, is used for collecting the wavelength value of the ultra-weak fiber grating 4 under the influence of the soil weight; the part of the ultra-weak fiber grating 4, which is positioned in the lower temperature compensation cavity 3, is used for collecting the wavelength value of the ultra-weak fiber grating 4 under the influence of soil temperature.
The ultra-weak fiber grating 4 sequentially penetrates through the shells 1 of the N monitoring units from top to bottom, the N monitoring units are connected in series, and the ultra-weak fiber grating 4 is fixedly connected with the top and the bottom of each separation base 5 and each shell 1 through the fixing device 7.
Because the ultra-weak fiber grating 4 has the advantage of massive multiplexing on one optical fiber, 20000 monitoring units can be multiplexed generally, 10000 monitoring units can be connected in series on one ultra-weak fiber grating 4. In practical application, a plurality of monitoring units can be connected in series with the minimum spacing of 10cm according to requirements to form a soil water content monitoring string, hereinafter referred to as a monitoring string for short, so as to meet the distributed monitoring requirements of the water content of the surface layer and the deep layer of the slope. And a plurality of monitoring strings are uniformly distributed in one area, so that distributed monitoring of one area can be realized.
The soil water content monitoring method comprises the following steps:
n monitoring units connected in series are placed in soil of a detected area along the vertical direction, the mass of dry soil in the upper soil containing cavity 2 is set to be m, and the length of the ultra-weak fiber bragg grating 4 in the upper soil containing cavity 2 is set to be l. When the soil water content in the upper soil accommodating cavity 2 changes, the length variation of the ultra-weak fiber grating 4 in the upper soil accommodating cavity 2 in the measured time period is delta l, the soil variation is delta m, and the strain delta epsilon of the ultra-weak fiber grating 4 in the measured time period is as follows:
wherein, E is the elastic modulus of the ultra-weak fiber grating 4, A is the sectional area of the ultra-weak fiber grating 4, and g is the gravity constant.
The fiber grating demodulator 6 is used for collecting the wavelength of the ultra-weak fiber grating 4 in each monitoring unit in the measured time period, namely the initial wavelength value lambda and the wavelength change value delta lambda of the ultra-weak fiber grating 4 in the upper soil accommodating cavity 2 in the measured time period and the initial wavelength value lambda of the ultra-weak fiber grating 4 in the lower temperature compensation cavity 3 in the measured time period are obtainedTAnd a wavelength variation value Delta lambdaT。
Then Δ λ, Δ ∈ and the amount of change Δ T in the temperature in the lower temperature compensation chamber 3 during the measured period are given by the following relations:
wherein, alpha is the expansion coefficient of the ultra-weak fiber grating 4, zeta is the thermo-optic coefficient of the ultra-weak fiber grating 4, PeIs the effective elastic-optical coefficient of the ultra-weak fiber grating 4.
Wherein, the expression of delta T is as follows:
substituting the expressions of Δ ε and Δ T into formula one to obtain the relationship between Δ m and Δ λ:
and due to
Then there is a relationship between the water content of the soil, ω, and Δ λ, as:
in practical application, as shown in fig. 2, a soil water content monitoring string calibrated in a laboratory is implanted into a slope 9 needing soil water content monitoring in a mechanical drilling manner, and the implanted hole is backfilled after the monitoring string 8 is implanted. The monitoring strings are connected through optical fiber jumpers. And finally, the optical fiber jumper 10 is connected to an ultra-weak fiber grating demodulator. The data of each monitoring string can be demodulated through the ultra-weak fiber grating demodulator, so that the aim of monitoring the water content of the soil on the slope in real time is fulfilled.
FIG. 3 is a graph of monitoring data for a slope application. Four different monitoring strings are selected, 4 monitoring units are selected from each monitoring string, and the monitoring units with the same number in the different monitoring strings are located on the same plane. Point a is the soil moisture content of four different monitoring units located in the first monitoring string; point B is the soil water content of four different monitoring units located in the second monitoring string; point C is the soil water content of four different monitoring units located in the third monitoring string; point D is the soil moisture content of four different monitoring units located in the fourth monitoring string. The water content of the soil at different positions of the slope body can be obtained from the figure 3.
Claims (10)
1. The soil water content monitoring device based on the ultra-weak fiber grating sensing technology is characterized by comprising N monitoring units, an ultra-weak fiber grating (4), a fiber grating demodulator (6) and an upper computer, wherein N is a positive integer greater than or equal to 1,
each monitoring unit includes: the soil-water separator comprises a shell (1) and a separation base (5), wherein water vapor outside the shell (1) can permeate into the shell (1), the separation base (5) is positioned inside the shell (1) and divides a cavity inside the shell (1) into an upper soil containing cavity (2) and a lower temperature compensation cavity (3) which are not communicated with each other, the separation base (5) can move up and down inside the shell (1), the upper soil containing cavity (2) is used for containing dry soil,
one end of the ultra-weak fiber grating (4) is connected with the wavelength signal input end of the fiber grating demodulator (6), the other end of the ultra-weak fiber grating (4) sequentially penetrates through the shells (1) of the N monitoring units from top to bottom, so that the N monitoring units are connected in series, the ultra-weak fiber grating (4) is fixedly connected with each separation base (5) and the top and the bottom of each shell (1),
the upper computer is used for collecting the wavelength of the ultra-weak fiber bragg grating (4) in each monitoring unit obtained by the fiber bragg grating demodulator (6) in the measured time period, and the water content of the soil in the upper soil accommodating cavity (2) in each monitoring unit in the measured time period is respectively calculated by utilizing the wavelength of the ultra-weak fiber bragg grating (4) in each monitoring unit.
2. The soil water content monitoring device based on the ultra-weak fiber grating sensing technology as claimed in claim 1, wherein the ultra-weak fiber grating (4) is located in the upper soil accommodating cavity (2) for collecting the wavelength value of the ultra-weak fiber grating (4) under the influence of soil weight,
the part of the ultra-weak fiber grating (4) positioned in the lower temperature compensation cavity (3) is used for collecting the wavelength value of the ultra-weak fiber grating (4) under the influence of soil temperature.
3. The soil water content monitoring device based on the ultra-weak fiber bragg grating sensing technology as claimed in claim 1 or 2, wherein the water content ω of the soil inside the upper soil containing cavity (2) in the measured time period in one monitoring unit is calculated according to the following formula:
wherein, lambda and delta lambda are respectively the ultra-weak fiber bragg grating (4) positioned in the upper soil accommodating cavity (2) when being measuredInitial wavelength value and wavelength variation value of interval, lambdaTAnd Δ λTRespectively is the initial wavelength value and the wavelength change value of the ultra-weak fiber grating (4) in the lower temperature compensation cavity (3) in the measured time period, E is the elastic modulus of the ultra-weak fiber grating (4), A is the sectional area of the ultra-weak fiber grating (4), P is the sectional area of the ultra-weak fiber gratingeIs the effective elastic-optical coefficient of the ultra-weak fiber grating (4), m is the mass of the dry soil in the upper soil accommodating cavity (2), and g is a gravity constant.
4. The soil water content monitoring device based on the ultra-weak fiber grating sensing technology as claimed in claim 1, wherein the minimum distance between two adjacent monitoring units on the same ultra-weak fiber grating (4) is 10 cm.
5. The soil water content monitoring method based on the ultra-weak fiber bragg grating sensing technology is characterized in that the method is realized based on a soil water content monitoring device, and the soil water content monitoring device comprises: n monitoring units and an ultra-weak fiber grating (4), wherein N is a positive integer greater than or equal to 1,
each monitoring unit includes: the soil-water separator comprises a shell (1) and a separation base (5), wherein water vapor outside the shell (1) can permeate into the shell (1), the separation base (5) is positioned inside the shell (1) and divides a cavity inside the shell (1) into an upper soil containing cavity (2) and a lower temperature compensation cavity (3) which are not communicated with each other, the separation base (5) can move up and down inside the shell (1), the upper soil containing cavity (2) is used for containing dry soil,
the ultra-weak fiber grating (4) sequentially penetrates through the shells (1) of the N monitoring units from top to bottom so that the N monitoring units are connected in series, the ultra-weak fiber grating (4) is fixedly connected with each separation base (5) and the top and the bottom of each shell (1),
the soil water content monitoring method comprises the following steps:
n monitoring units connected in series are placed in the soil of a tested area along the vertical direction, the wavelength of the ultra-weak fiber grating (4) in each monitoring unit in the tested time period is collected by a fiber grating demodulator (6),
and respectively calculating the water content of the soil in the upper soil accommodating cavity (2) in each monitoring unit in the measured time period by using the wavelength of the ultra-weak fiber bragg grating (4) in each monitoring unit.
6. The soil water content monitoring method based on the ultra-weak fiber grating sensing technology according to claim 5, wherein the part of the ultra-weak fiber grating (4) located in the upper soil accommodating cavity (2) is used for collecting the wavelength value of the ultra-weak fiber grating (4) under the influence of soil weight,
the part of the ultra-weak fiber grating (4) positioned in the lower temperature compensation cavity (3) is used for collecting the wavelength value of the ultra-weak fiber grating (4) under the influence of soil temperature.
7. The soil water content monitoring method based on the ultra-weak fiber bragg grating sensing technology as claimed in claim 5 or 6, wherein the water content omega of the soil inside the upper soil containing cavity (2) in the measured time period in one monitoring unit is calculated according to the following formula:
wherein, lambda and delta lambda are respectively the initial wavelength value and the wavelength variation value of the ultra-weak fiber grating (4) in the upper soil accommodating cavity (2) in the measured time period, and lambdaTAnd Δ λTThe initial wavelength value and the wavelength change value of the ultra-weak fiber grating (4) in the lower temperature compensation cavity (3) in the measured time period are respectively, E is the elastic modulus of the ultra-weak fiber grating (4), A is the sectional area of the ultra-weak fiber grating (4), Pe is the effective elastic-optical coefficient of the ultra-weak fiber grating (4), m is the mass of the dry soil in the upper soil accommodating cavity (2), and g is a gravity constant.
8. The soil water content monitoring method based on the ultra-weak fiber grating sensing technology as claimed in claim 7, wherein the obtaining method of the calculation formula of the water content ω of the soil is as follows:
establishing a relation among delta lambda, strain delta epsilon of the ultra-weak fiber grating (4) in the measured time period and the variation delta T of the temperature in the lower temperature compensation cavity (3) in the measured time period:
wherein alpha is the expansion coefficient of the ultra-weak fiber grating (4), zeta is the thermo-optic coefficient of the ultra-weak fiber grating (4),
the expressions Δ ∈ and Δ T are respectively:
wherein, the delta m is the variation of the quality of the dry soil in the upper soil accommodating cavity (2) in the measured time period,
substituting the expressions of Δ ε and Δ T into formula one to obtain the relationship between Δ m and Δ λ:
the relationship between the water content of the soil, ω, and Δ λ, is:
9. the soil water content monitoring method based on the ultra-weak fiber grating sensing technology as claimed in claim 8, wherein the expression of Δ ∈ is obtained by:
since Δ ε is Δ l/l, then
Wherein, l is the length of the ultra-weak fiber grating (4) in the upper soil accommodating cavity (2), and delta l is the length variation of the ultra-weak fiber grating (4) in the upper soil accommodating cavity (2) in the measured time period.
10. The soil water content monitoring method based on the ultra-weak fiber grating sensing technology as claimed in claim 5, wherein the minimum distance between two adjacent monitoring units on the same ultra-weak fiber grating (4) is 10 cm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111202903.4A CN113916794B (en) | 2021-10-15 | 2021-10-15 | Soil water content monitoring device and method based on ultra-weak fiber bragg grating sensing technology |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111202903.4A CN113916794B (en) | 2021-10-15 | 2021-10-15 | Soil water content monitoring device and method based on ultra-weak fiber bragg grating sensing technology |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN113916794A true CN113916794A (en) | 2022-01-11 |
| CN113916794B CN113916794B (en) | 2023-07-25 |
Family
ID=79240791
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111202903.4A Active CN113916794B (en) | 2021-10-15 | 2021-10-15 | Soil water content monitoring device and method based on ultra-weak fiber bragg grating sensing technology |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN113916794B (en) |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108279211A (en) * | 2018-03-25 | 2018-07-13 | 南京大学 | A kind of quasi-distributed system, sensing device and method measuring soil moisture content |
| CN208171842U (en) * | 2018-06-06 | 2018-11-30 | 南昌工程学院 | A kind of soil moisture content test device |
| CN109828097A (en) * | 2019-01-09 | 2019-05-31 | 湖南大学 | A kind of soil water meauring device and method based on fiber bragg grating |
| CN110646035A (en) * | 2019-10-25 | 2020-01-03 | 中国地质调查局水文地质环境地质调查中心 | Multi-parameter landslide monitoring device and method based on weak grating |
| CN112461151A (en) * | 2020-11-20 | 2021-03-09 | 中国地质调查局水文地质环境地质调查中心 | Deep deformation monitoring device and method based on weak grating |
| CN112903138A (en) * | 2021-01-19 | 2021-06-04 | 汕头大学 | Sensor detection system |
| CN113406007A (en) * | 2021-06-16 | 2021-09-17 | 南京大学 | Soil moisture content intelligent monitoring system based on heat pulse identical weak fiber grating array and in-situ calibration method |
-
2021
- 2021-10-15 CN CN202111202903.4A patent/CN113916794B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108279211A (en) * | 2018-03-25 | 2018-07-13 | 南京大学 | A kind of quasi-distributed system, sensing device and method measuring soil moisture content |
| CN208171842U (en) * | 2018-06-06 | 2018-11-30 | 南昌工程学院 | A kind of soil moisture content test device |
| CN109828097A (en) * | 2019-01-09 | 2019-05-31 | 湖南大学 | A kind of soil water meauring device and method based on fiber bragg grating |
| CN110646035A (en) * | 2019-10-25 | 2020-01-03 | 中国地质调查局水文地质环境地质调查中心 | Multi-parameter landslide monitoring device and method based on weak grating |
| CN112461151A (en) * | 2020-11-20 | 2021-03-09 | 中国地质调查局水文地质环境地质调查中心 | Deep deformation monitoring device and method based on weak grating |
| CN112903138A (en) * | 2021-01-19 | 2021-06-04 | 汕头大学 | Sensor detection system |
| CN113406007A (en) * | 2021-06-16 | 2021-09-17 | 南京大学 | Soil moisture content intelligent monitoring system based on heat pulse identical weak fiber grating array and in-situ calibration method |
Also Published As
| Publication number | Publication date |
|---|---|
| CN113916794B (en) | 2023-07-25 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Zhu et al. | Investigation of the evolutionary process of a reinforced model slope using a fiber-optic monitoring network | |
| CN100487386C (en) | Multi-parameter detector based on composite optical fiber device | |
| CN105442437B (en) | The shock insulation rubber bearing that a kind of working parameters can be monitored and be recognized | |
| Huang et al. | Stability monitoring of rainfall-induced deep landslides through pore pressure profile measurements | |
| CN102829728A (en) | Comprehensive monitoring system for side slope and landslip | |
| CN104199086A (en) | Single-component fiber-optic geophone, three-component fiber-optic microseismic geophone comprising same and three-component fiber-optic microseismic detection array also comprising same | |
| Teja et al. | Land Slide detection and monitoring system using wireless sensor networks (WSN) | |
| CN106018755B (en) | A kind of experimental system of large size ground fissure physical model | |
| CN103727980A (en) | Optical fiber sensing system for monitoring slope landslide condition in real time | |
| CN106996841B (en) | Drilling type optical fiber three-dimensional ground stress observation device with self-consistent function | |
| CN103091197A (en) | Weighing steam infiltration meter | |
| CN114017121B (en) | Rock burst real-time monitoring system and early warning method based on strain field | |
| EP0760989B1 (en) | Snow pack stability monitor | |
| Liu et al. | Analysis of Tianchi volcano activity in Changbai mountain, NE China | |
| CN106441226A (en) | Inclination testing device based on compound interferometer structure | |
| CN201028977Y (en) | Multi-parameter detecting instrument based on compound optical fiber device | |
| CN105155597B (en) | A kind of monitoring of underground structure and regulating system and its construction method | |
| CN106705902B (en) | A kind of system and method for monitoring filling band stability | |
| CN113916794A (en) | Soil water content monitoring device and method based on ultra-weak fiber bragg grating sensing technology | |
| CN113932767B (en) | Electric power comprehensive pipe rack settlement monitoring device and method based on temperature compensation | |
| Wang et al. | Research on the surface subsidence monitoring technology based on fiber Bragg grating sensing | |
| JP4628188B2 (en) | Landslide detection device | |
| CN106643630A (en) | System and method of monitoring stability during gob-side entry retaining filling body stoping period | |
| CN102926808B (en) | Underground coal dressing chamber bottom plate online monitoring device and method based on fiber bragg grating sensing | |
| CN109100307A (en) | For monitoring the experimental provision and system of simulation oil reservoir rock deformation |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |