CN113916794B - 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
- CN113916794B CN113916794B CN202111202903.4A CN202111202903A CN113916794B CN 113916794 B CN113916794 B CN 113916794B CN 202111202903 A CN202111202903 A CN 202111202903A CN 113916794 B CN113916794 B CN 113916794B
- Authority
- CN
- China
- Prior art keywords
- ultra
- soil
- weak fiber
- fiber grating
- monitoring
- 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.)
- Active
Links
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 bragg grating sensing technology relate to the technical field of monitoring of side slope soil body states. The invention aims to solve the problem that the water content of the soil surface layer and the deep layer cannot be monitored in a distributed and real-time manner in slope safety protection monitoring. According to the invention, water vapor outside the shell of each monitoring unit can permeate into the shell, the inner cavity of the shell is divided into an upper soil accommodating cavity and a lower temperature compensating cavity which are not communicated with each other by the separation base, 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 N monitoring units from top to bottom, the ultra-weak fiber grating is fixedly connected with the separation base and the top and bottom of the shell, the upper computer collects the wavelength of the ultra-weak fiber grating in each monitoring unit obtained by the fiber grating demodulator in a measured time period, and the water content of soil in the upper soil accommodating cavity in each monitoring unit in the measured time period is calculated by utilizing the wavelength.
Description
Technical Field
The invention belongs to the technical field of slope soil state monitoring, and particularly relates to a slope soil water content monitoring technology.
Background
Landslide hazard is a natural disaster, and mainly refers to a disaster caused by that rock mass or soil body loses an original balance state under the action of gravity and slides down the whole or part of a potential weak structural surface. When landslide disasters occur in areas with frequent activities of human beings such as highways, railways, villages and the like, the landslide disasters cause damage to infrastructure and houses, and the landslide disasters cause massive casualties. There have been studies showing that rainfall is one of the main causes of landslide hazard occurrence. The effect of rainfall on landslide is a dynamic process, and rainwater permeates into the soil body, so that the water content of the soil body can be increased, the volume weight of the soil body is increased, the soil body is softened, and the shear strength of the soil body is reduced. Therefore, the distributed real-time monitoring of the water content of the soil body of the side slope is performed, and the method has important significance for grasping the stable state of the soil body of the side slope.
The existing methods for monitoring the water content of the soil body of the side slope are mostly methods for monitoring the water content of the soil body of the surface of the side slope, and few methods for monitoring the water content of the deep soil body of the side slope exist. The existing monitoring methods for the water content of the deep soil body of the side slope can monitor the water content of the deep soil body, but the sensor calibration process is complex, the single data acquisition time is long, and the water content of the deep soil body cannot be monitored in real time.
Disclosure of Invention
The invention aims to solve the problem that the water content of the soil surface layer and the deep layer cannot be monitored in a distributed and real-time manner in slope safety protection monitoring, and provides a soil water content monitoring device and method based on an ultra-weak fiber bragg grating sensing technology.
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 comprises: the water vapor outside the shell 1 can permeate into the shell 1, the separation base 5 is positioned inside the shell 1 and separates the inner cavity of the shell 1 into an upper soil accommodating cavity 2 and a lower temperature compensating 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 accommodating cavity 2 is used for accommodating 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 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 calculating the water content 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.
Further, 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, and the part of the ultra-weak fiber grating 4 located in the lower temperature compensating cavity 3 is used for collecting the wavelength value of the ultra-weak fiber grating 4 under the influence of soil temperature.
Further, the water content ω of the soil inside the upper soil containing chamber 2 during 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 accommodation cavity 2 in the measured time period, lambda T And Deltalambda T Respectively an initial wavelength value and a wavelength variation value of the ultra-weak fiber grating 4 in the lower temperature compensation cavity 3 in a measured time period, 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 P is the total length of the ultra-weak fiber grating 4 e And m is the mass of the dry soil in the upper soil containing cavity 2 and g is a gravity constant.
The method is realized based on a soil water content monitoring device, and the soil water content monitoring device comprises the following steps: n monitoring units and an ultra-weak fiber grating 4, N is a positive integer greater than or equal to 1,
each monitoring unit comprises: the water vapor outside the shell 1 can permeate into the shell 1, the separation base 5 is positioned inside the shell 1 and separates the inner cavity of the shell 1 into an upper soil accommodating cavity 2 and a lower temperature compensating 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 accommodating cavity 2 is used for accommodating 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 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 detected area along the vertical direction, the wavelength of the ultra-weak fiber bragg grating 4 in each monitoring unit in the detected time period is acquired by using the fiber bragg 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 grating 4 in each monitoring unit.
Further, the water content ω of the soil inside the upper soil containing chamber 2 during 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 accommodation cavity 2 in the measured time period, lambda T And Deltalambda T Respectively an initial wavelength value and a wavelength variation value of the ultra-weak fiber grating 4 in the lower temperature compensation cavity 3 in a measured time period, 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 P is the total length of the ultra-weak fiber grating 4 e And m is the mass of the dry soil in the upper soil containing cavity 2 and g is a gravity constant.
Further, the method for obtaining the water content omega calculation formula of the soil comprises the following steps:
establishing a relational expression of delta lambda, the 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, ζ is the thermo-optic coefficient of the ultra-weak fiber grating 4,
the expressions Δε and ΔT are respectively:
wherein Deltam is the variation of the quality of the dry soil in the upper soil containing cavity 2 in the measured time period,
then substituting both the expressions of Δε and ΔT into equation one, the relationship between Δm and Δλ is obtained:
the relationship between the moisture content ω and Δλ of the soil is:
the device and the method for monitoring the water content of the soil based on the ultra-weak fiber bragg grating sensing technology can monitor the water content of the surface layer and the deep layer of the soil body of the side slope, can realize the distributed monitoring of the water content of the soil body of the side slope, are flexible in sensor layout mode, and are suitable for the side slope with obvious influence of precipitation on stability. The monitoring device can be calibrated and packaged in a laboratory, and is directly installed on site, so that the installation and layout are simple; the soil water content monitoring data can be displayed in real time through software, and has good monitoring instantaneity. And the ultra-weak fiber grating is packaged, so that the change of the soil mass 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 moisture content monitoring device based on an ultra-weak fiber grating sensing technology.
Fig. 2 is a schematic view of a soil moisture content monitoring device deployed in a slope area.
Fig. 3 is a graph showing a monitored moisture content distribution of soil on a slope.
Detailed Description
In recent years, the ultra-weak fiber bragg grating sensing technology has the same monitoring precision as that of a common optical grating due to the capability of multiplexing a large amount of optical fibers, is focused by students at home and abroad, and has good monitoring effect in many projects needing to be monitored in a large range and long distance. Because the central wavelength of the ultra-weak fiber grating is affected 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, the optical fiber grating can monitor the strain and the temperature. By carrying out specific encapsulation on the ultra-weak fiber grating, monitoring on various physical quantities, such as moisture field monitoring, gas field monitoring, chemical field monitoring and the like, can be realized. In addition, the ultra-weak fiber bragg grating has lower cost and is suitable for large-range and long-distance monitoring. Therefore, the invention monitors the soil moisture content in real time by monitoring the change of the ultra-weak fiber grating wavelength value caused by the soil mass change based on the characteristic that the soil mass is changed when the soil moisture content with certain mass is changed, thereby effectively acquiring the change condition of the soil moisture content of the whole or partial surface layer and the deep soil of the slope and providing effective monitoring data for slope stability evaluation. The specific implementation method is as follows.
The first embodiment is as follows: referring to fig. 1, a concrete description is given of the present embodiment, and the soil moisture content monitoring device based on the ultra-weak fiber bragg grating sensing technology according to the present embodiment includes N monitoring units, an ultra-weak fiber bragg grating 4, a fiber bragg grating demodulator 6, and an upper computer, where N is a positive integer greater than or equal to 1.
Each monitoring unit comprises: a housing 1 and a partition base 5. The separation base 5 is located inside the shell 1 and separates the inner cavity of the shell 1 into an upper soil accommodating cavity 2 and a lower temperature compensating cavity 3 which are not communicated with each other, the separation base 5 can move up and down inside the shell 1, and the upper soil accommodating cavity 2 is used for accommodating dry soil. The dry soil is in-situ soil of the area to be measured after drying. The casing 1 allows moisture outside thereof to penetrate into the dry soil inside the upper soil containing 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 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 the soil temperature.
One end of the ultra-weak fiber grating 4 is connected with the wavelength signal input end of the fiber grating demodulator 6, and 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, and the ultra-weak fiber grating 4 is fixedly connected with the top and the bottom of each separation base 5 and the shell 1 through the fixing device 7.
Since the ultra-weak fiber grating 4 has the advantage of multiplexing a large number of optical fibers, typically 20000 optical fibers can be multiplexed, 10000 monitoring units can be connected in series to one ultra-weak fiber grating 4. In practical application, a plurality of monitoring units can be connected in series according to the minimum interval of the requirement of 10cm to form a soil water content monitoring string, which is hereinafter referred to as a monitoring string, so as to meet the distributed monitoring requirement of the water content of the surface layer of the slope body and the deep soil. And a plurality of monitoring strings are uniformly distributed in one area, so that the distributed monitoring of one area can be realized.
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 wavelength specifically comprises: the initial wavelength value lambda and the wavelength variation value delta lambda of the ultra-weak fiber grating 4 in the upper soil accommodation 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 T And a wavelength variation value Deltalambda T 。
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 grating 4 in each monitoring unit according to the following steps:
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 P e And m is the mass of the dry soil in the upper soil containing cavity 2 and g is a gravity constant.
In this embodiment, when moisture in the soil permeates into the dry soil in the upper soil containing chamber 2 through the casing 1, the mass of the soil in the upper soil containing chamber 2 increases, and the partition base 5 is pressed to move downward. Because the ultra-weak fiber gratings 4 are fixedly connected with the top and the bottom of each partition base 5 and the housing 1, respectively, when the partition base 5 moves downwards, the length of the ultra-weak fiber gratings 4 in the upper soil containing cavity 2 is lengthened, so that the wavelength is changed. Meanwhile, if the temperature changes, the wavelength of the ultra-weak fiber grating 4 in the lower temperature compensation cavity 3 also changes due to the temperature changes.
In the embodiment, the ultra-weak fiber bragg grating is packaged into a device suitable for slope soil water content distributed and real-time monitoring, which is hereinafter referred to as a monitoring device, and the water contents of the surface layer and the deep layer of the slope soil body are monitored in a distributed and real-time manner by connecting a plurality of monitoring devices in series. When the water content of the soil body is unchanged, 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 correspondingly changes. Demodulating the wavelength variation value of the ultra-weak fiber grating by an ultra-weak fiber grating demodulator, and realizing the distributed and real-time monitoring of the soil water content according to the relationship between the soil water content and the wavelength variation value of the ultra-weak fiber grating.
The second embodiment is as follows: the method for monitoring the soil moisture content based on the ultra-weak fiber bragg grating sensing technology according to the embodiment is implemented based on a soil moisture content monitoring device, wherein the soil moisture 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 comprises: a housing 1 and a partition base 5. The separation base 5 is located inside the shell 1 and separates the inner cavity of the shell 1 into an upper soil accommodating cavity 2 and a lower temperature compensating cavity 3 which are not communicated with each other, the separation base 5 can move up and down inside the shell 1, and the upper soil accommodating cavity 2 is used for accommodating dry soil. The dry soil is in-situ soil of the area to be measured after drying. The casing 1 allows moisture outside thereof to penetrate into the dry soil inside the upper soil containing 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 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 the soil temperature.
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, and the ultra-weak fiber grating 4 is fixedly connected with the top and the bottom of each separation base 5 and the shell 1 through the fixing device 7.
Since the ultra-weak fiber grating 4 has the advantage of multiplexing a large number of optical fibers, typically 20000 optical fibers can be multiplexed, 10000 monitoring units can be connected in series to one ultra-weak fiber grating 4. In practical application, a plurality of monitoring units can be connected in series according to the minimum 10cm of the required interval distance to form a soil water content monitoring string, which is hereinafter referred to as a monitoring string, so as to meet the distributed monitoring requirements of the water content of the surface layer of the slope body and the deep soil. And a plurality of monitoring strings are uniformly distributed in one area, so that the 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 measured area along the vertical direction, the mass of dry soil in the upper soil accommodating cavity 2 is set to be m, and the length of the ultra-weak fiber grating 4 in the upper soil accommodating cavity 2 is set to be l. When the water content of the soil in the upper soil containing cavity 2 changes, the length change of the ultra-weak fiber grating 4 in the upper soil containing cavity 2 in the measured time period is Δl, the soil change is Δm, and the strain Δε of the ultra-weak fiber grating 4 in the measured time period is:
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 gravitational 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 of the ultra-weak fiber grating 4 in the upper soil containing cavity 2 in the measured time period are obtainedThe variation value delta lambda 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 T And a wavelength variation value Deltalambda T 。
The relationship between Δλ, Δε and the amount of change Δt in the temperature in the lower temperature compensation chamber 3 during the measured time period is:
wherein alpha is the expansion coefficient of the ultra-weak fiber grating 4, ζ is the thermo-optic coefficient of the ultra-weak fiber grating 4, and P e Is the effective elasto-optical coefficient of the ultra-weak fiber grating 4.
Wherein, Δt expression is:
then substituting both the expressions of Δε and ΔT into equation one, the relationship between Δm and Δλ is obtained:
and due to
Then there is a relationship between the moisture content ω and Δλ of the soil:
in practical application, as shown in fig. 2, the soil water content monitoring string calibrated in the laboratory is implanted into a side slope body 9 needing to be subjected to soil water content monitoring in a mechanical drilling mode, and after the monitoring string 8 is implanted, backfilling treatment is carried out on the implantation hole. The monitoring strings are connected through optical fiber jumpers. Finally, the optical fiber jumper 10 is connected into 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 purpose of monitoring the water content of the slope soil in real time is achieved.
Fig. 3 is a diagram of monitoring data for an application on a slope. Four different monitoring strings are selected, each monitoring string is provided with 4 monitoring units, and monitoring units with the same number in 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 moisture content of four different monitoring units located in the second monitoring string; point C is the soil moisture 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 can be obtained by the method shown in the figure 3.
Claims (8)
1. The soil water content monitoring device based on the ultra-weak fiber bragg grating sensing technology is characterized by comprising 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 comprises: the water vapor outside the shell (1) can permeate into the shell (1), the separation base (5) is positioned inside the shell (1) and separates the inner cavity of the shell (1) into an upper soil accommodating cavity (2) and a lower temperature compensating 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 accommodating cavity (2) is used for accommodating 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 respectively calculating the water content of 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;
the water content omega of the soil in 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, lambda T And Deltalambda T Respectively an initial wavelength value and a wavelength variation value of the ultra-weak fiber grating (4) in the lower temperature compensation cavity (3) in a measured time period, 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 P is the optical fiber grating e And m is the mass of the dry soil in the upper soil accommodating cavity (2) and g is a gravity constant.
2. The soil moisture content monitoring device based on the ultra-weak fiber bragg grating sensing technology according to claim 1, wherein the part of the ultra-weak fiber bragg grating (4) positioned in the upper soil accommodating cavity (2) is used for collecting the wavelength value of the ultra-weak fiber bragg grating (4) under the influence of the 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 the soil temperature.
3. The soil moisture content monitoring device based on the ultra-weak fiber bragg grating sensing technology according to claim 1, wherein the minimum distance between two adjacent monitoring units on the same ultra-weak fiber bragg grating (4) is 10cm.
4. The method for monitoring the soil water content based on the ultra-weak fiber bragg grating sensing technology is characterized by being realized based on a soil water content monitoring device, and the soil water content monitoring device comprises the following steps: 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 comprises: the water vapor outside the shell (1) can permeate into the shell (1), the separation base (5) is positioned inside the shell (1) and separates the inner cavity of the shell (1) into an upper soil accommodating cavity (2) and a lower temperature compensating 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 accommodating cavity (2) is used for accommodating 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 soil of a detected area along the vertical direction, the wavelength of the ultra-weak fiber grating (4) in each monitoring unit in the detected time period is collected by a fiber grating demodulator (6),
respectively calculating the water content of soil in an upper soil accommodating cavity (2) in each monitoring unit in a measured time period by utilizing the wavelength of the ultra-weak fiber grating (4) in each monitoring unit;
the water content omega of the soil in 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, lambda T And Deltalambda T Respectively an initial wavelength value and a wavelength variation value of the ultra-weak fiber grating (4) in the lower temperature compensation cavity (3) in a measured time period, 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 P is the optical fiber grating e And m is the mass of the dry soil in the upper soil accommodating cavity (2) and g is a gravity constant.
5. The method for monitoring the water content of soil based on the ultra-weak fiber bragg grating sensing technology as claimed in claim 4, wherein the part of the ultra-weak fiber bragg grating (4) positioned in the upper soil accommodating cavity (2) is used for collecting the wavelength value of the ultra-weak fiber bragg grating (4) under the influence of the 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 the soil temperature.
6. The method for monitoring the water content of soil based on the ultra-weak fiber bragg grating sensing technology as claimed in claim 4, wherein the method for obtaining the water content omega calculation formula of the soil is as follows:
establishing a relational expression of delta lambda, the 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 Δε and ΔT are respectively:
wherein Deltam is the variation of the quality of the dry soil in the upper soil accommodating cavity (2) in the measured time period,
then substituting both the expressions of Δε and ΔT into equation one, the relationship between Δm and Δλ is obtained:
the relationship between the moisture content ω and Δλ of the soil is:
7. the method for monitoring the water content of soil based on the ultra-weak fiber bragg grating sensing technology as claimed in claim 6, wherein the expression of delta epsilon is obtained by:
since Δε=Δl/l, there is
Wherein l is the length of the ultra-weak fiber grating (4) in the upper soil accommodating cavity (2), and Deltal is the length variation of the ultra-weak fiber grating (4) in the upper soil accommodating cavity (2) in the measured time period.
8. The method for monitoring the water content of soil based on the ultra-weak fiber bragg grating sensing technology according to claim 4, wherein the minimum distance between two adjacent monitoring units on the same ultra-weak fiber bragg grating (4) is 10cm.
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 CN113916794A (en) | 2022-01-11 |
| CN113916794B true 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 |
|---|---|
| CN113916794A (en) | 2022-01-11 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Zhu et al. | FBG-based monitoring of geohazards: current status and trends | |
| Van Camp et al. | Geophysics from terrestrial time‐variable gravity measurements | |
| Zhu et al. | Investigation of the evolutionary process of a reinforced model slope using a fiber-optic monitoring network | |
| Huang et al. | Stability monitoring of rainfall-induced deep landslides through pore pressure profile measurements | |
| CN106018755B (en) | A kind of experimental system of large size ground fissure physical model | |
| Teja et al. | Land Slide detection and monitoring system using wireless sensor networks (WSN) | |
| CN103091197A (en) | Weighing steam infiltration meter | |
| CN104614242A (en) | Excavation and surrounding rock stress and strain monitoring model testing device for rock-soil chamber under complicated conditions, and method thereof | |
| CN104655036B (en) | Deformation quasi-distributed optical fiber sensing system in geo- textile technique body | |
| Liu et al. | Analysis of Tianchi volcano activity in Changbai mountain, NE China | |
| CN105783863A (en) | Foundation settlement measuring system and foundation settlement measuring method based on optical fiber sensing technology | |
| CN106996841B (en) | Drilling type optical fiber three-dimensional ground stress observation device with self-consistent function | |
| Ni et al. | Temperature-independent fiber Bragg grating tilt sensor | |
| CN106441226A (en) | Inclination testing device based on compound interferometer structure | |
| CN113916794B (en) | Soil water content monitoring device and method based on ultra-weak fiber bragg grating sensing technology | |
| CN106705902B (en) | A kind of system and method for monitoring filling band stability | |
| Guo et al. | Fiber Bragg grating sensor-based monitoring strategy for slope deformation in centrifugal model test | |
| CN105155597B (en) | A kind of monitoring of underground structure and regulating system and its construction method | |
| Wang et al. | Research on the surface subsidence monitoring technology based on fiber Bragg grating sensing | |
| CN102508300B (en) | Earthquake underground fluid inspection well and system and method used earthquake underground fluid inspection well to detect seismic precursor abnormal information | |
| CN104992533A (en) | Water-gas pressure sensor monitoring warning and forecasting system | |
| CN106643630A (en) | System and method of monitoring stability during gob-side entry retaining filling body stoping period | |
| Knudsen et al. | Permanently installed high-resolution fiber optic 3C/4D seismic sensor systems for in-well imaging and monitoring applications | |
| Abdoun et al. | Advanced sensing for real-time monitoring of geotechnical systems | |
| CN113776450B (en) | Ground deformation monitoring system and monitoring method based on optical fiber technology |
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 |