Ground settlement monitoring device with spirally wound distributed optical fiber

Abstract

The present invention discloses a foundation settlement monitoring device and method for using a spirally wound distributed optical fiber. The device comprises a cylindrical elastic foundation support and a counterweight located within a stable stratum; the upper end of the counterweight includes a connection surface connected to the lower end surface of the cylindrical elastic support; an optical cable spirally wound around the cylindrical surface of the cylindrical elastic support; the upper end of the optical cable extends from the foundation soil and is connected to a testing unit; the optical cable includes a strain sensing optical fiber; the strain sensing optical fiber and the elastic sheath of the optical cable are fixed together by bonding; the testing unit acquires an optical signal flowing through the optical cable, converts the optical signal into a digital signal, and transmits it to a data processing unit; the data processing unit calculates the soil settlement value at each location within the range of the optical cable spirally wound around the cylindrical elastic support based on the difference between two digital signals acquired from the testing unit. The present invention addresses the shortcoming of a distributed optical fiber having an excessively small ultimate tensile strain, which results in an excessively small measurable range.

Description

Technical Field

[0001] The present invention relates to the technical field of foundation settlement monitoring, and in particular to a foundation settlement monitoring device with a spirally wound distributed optical fiber. Background Art

[0002] In road construction, many factors can cause subgrade settlement, including vehicle load, construction quality, and climate. These factors can lead to differential subgrade settlement, which can in turn cause road cracking and other problems, reducing driving comfort and safety. Therefore, effective monitoring methods should be implemented to track and monitor subgrade settlement over the long term, assess its status, and guide road maintenance and repair, which is of great engineering significance.

[0003] At present, the commonly used methods for road foundation settlement monitoring include the settlement plate method, leveling method, and electromagnetic layered settlement meter method. This makes it impossible to comprehensively and effectively characterize the settlement distribution within the full depth range of the foundation. At the same time, there are problems such as low automation level, large on-site workload, and low monitoring accuracy.

[0004] Although distributed optical fibers have been used in this field to solve the problem of foundation settlement monitoring, by monitoring the change in the frequency of Brillouin scattered light in the distributed optical fiber, the strain distribution of the entire optical fiber and the deformation distribution can be obtained, thereby realizing full-depth automated monitoring of foundation settlement.

[0005] Compared with traditional monitoring methods, the use of distributed optical fiber for foundation settlement monitoring has the advantages of high sensitivity, long distance, corrosion resistance, anti-electromagnetic interference, small size, light weight, and easy network integration, which can realize continuous intelligent monitoring.

[0006] However, in the prior art, the application of distributed optical fibers to monitor soil settlement mainly adopts a vertical direct burial method, that is, after vertically drilling a hole on the soil surface, the optical fiber is directly buried vertically in the soil.

[0007] Although the above method can obtain the settlement distribution within the depth range of the soil, it is limited by the ultimate tensile strain of the optical fiber (the ultimate tensile strain of the optical fiber is 0.03), and its measurable range is very limited. It is only suitable for measuring the settlement of soils with small deformation. For situations with large settlement deformation, such as road foundations, this method cannot meet the needs of engineering applications.

[0008] Therefore, how to solve the defect that the measurable range of distributed optical fiber is very limited due to the small ultimate tensile strain and is only suitable for soil settlement measurement with small deformation has become a technical problem that technicians in this field urgently need to solve. Summary of the Invention

[0009] In view of the above-mentioned defects of the prior art, the present invention provides a foundation settlement monitoring device with a spirally wound distributed optical fiber, the purpose of which is to solve the defect that the measurable range is very limited due to the small ultimate tensile strain of the distributed optical fiber, and it is only suitable for soil settlement measurement with small deformation.

[0010] To achieve the above-mentioned object, the present invention discloses a foundation settlement monitoring device with a spirally wound distributed optical fiber, comprising a cylindrical elastic support vertically arranged in the foundation soil, and a counterweight arranged at the lower end of the cylindrical elastic support and located in a stable bottom layer below the foundation soil;

[0011] The upper end of the counterweight includes a connecting surface that is larger than the lower end surface of the cylindrical elastic support and is tightly connected to the lower end surface of the cylindrical elastic support;

[0012] The cylindrical surface of the cylindrical elastic support is spirally wound with an optical cable;

[0013] The optical cable is fixed to the cylindrical surface of the cylindrical elastic support, and the upper end thereof extends from the foundation soil and is connected to the test unit;

[0014] The optical cable includes a strain sensing optical fiber;

[0015] The strain sensing optical fiber and the elastic sheath of the optical cable are fixed together by bonding;

[0016] The testing unit acquires the optical signal flowing through the optical cable, and converts the optical signal into a digital signal and transmits it to the data processing unit;

[0017] The data processing unit calculates the soil settlement value of the foundation soil at each position within the range of the optical cable spirally wound around the cylindrical elastic support based on the difference between the digital signals obtained twice from the testing unit.

[0018] Preferably, the optical cable further includes a temperature sensing optical fiber;

[0019] The temperature sensing optical fiber is provided with a plastic sleeve that can slide relatively along the axis;

[0020] The plastic sleeve and the elastic sheath are fixed into one piece by bonding.

[0021] Preferably, the bolt rise angle of the spirally wound optical cable is 30 degrees to 80 degrees.

[0022] Preferably, the cylindrical surface of the cylindrical elastic support is provided with a spiral groove corresponding to the spirally wound optical cable and matching the optical cable;

[0023] The spiral groove matching the optical cable means that the optical cable can be embedded and fixed in the spiral groove.

[0024] Preferably, the outer diameter of the cylindrical elastic support is 5 cm to 15 cm, and is made of rubber or silicone;

[0025] The elastic sheath is made of PE material.

[0026] Preferably, the test unit is an optical fiber demodulation device, which is used to demodulate the optical signal obtained from the optical cable, that is, the optical fiber frequency value, and convert the optical signal into the digital signal.

[0027] Preferably, the data processing unit is an analysis terminal of a computer, which uses the digital signal obtained from the testing unit to calculate the soil settlement value of the foundation soil at each position within the range of the optical cable spirally wrapped around the cylindrical elastic support.

[0028] The present invention also provides a method for using a foundation settlement monitoring device with a helically wound distributed optical fiber. The data processing unit calculates the settlement S at a certain depth within the range of the optical cable helically wound around a cylindrical elastic support in the foundation soil based on the difference between the digital signals obtained from the testing unit twice. The calculation formula is as follows:

[0029]

[0030] Wherein, L is the length of the optical cable spirally wound on the cylindrical elastic support;

[0031] C is the spatial resolution parameter used by the test unit when collecting data;

[0032] θ is the bolt lift angle of the helically wound optical cable;

[0033] k is the strain proportionality coefficient of the strain sensing optical fiber in the optical cable;

[0034] V is the Poisson's ratio of the cylindrical elastic support;

[0035] v ε0i is the frequency value of the strain sensing optical fiber in the previous two digital signals obtained from the test unit;

[0036] v t0i The frequency value of the temperature sensing optical fiber in the previous two digital signals obtained from the test unit;

[0037] v εi is the frequency value of the strain sensing optical fiber in the latter of two digital signals obtained from the test unit;

[0038] v tiThe frequency value of the temperature sensing optical fiber of the second digital signal obtained from the test unit twice;

[0039] ε f0i The optical cable strain of the previous digital signal obtained from the test unit twice;

[0040] ε fi The optical cable strain of the latter of the two digital signals obtained from the test unit;

[0041] ε s0i is the vertical strain of the cylindrical elastic support in the previous digital signal obtained from the testing unit twice;

[0042] ε si The vertical strain of the cylindrical elastic support obtained in the latter of two digital signals obtained from the test unit;

[0043] y is the vertical distance relative to the bottom end of the cylindrical elastic support.

[0044] Preferably, the maximum range S of the monitoring device max The calculation formula is as follows:

[0045]

[0046] Wherein, H is the total length of the cylindrical elastic support.

[0047] Preferably, each time the test unit needs to collect the optical signal of the optical cable, the optical cable is connected to the test unit, and at other times, the optical cable is disconnected from the test unit.

[0048] Beneficial effects of the present invention:

[0049] The present invention solves the defect that the measurable range of distributed optical fibers is very limited due to the extremely small ultimate tensile strain, and is only suitable for settlement measurement of soils with small deformations. It expands the application scope of distributed optical fibers in foundation settlement monitoring and can also improve monitoring accuracy and monitoring depth.

[0050] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A structural diagram of an embodiment of the present invention is shown.

[0052] Figure 2 A schematic structural diagram showing a cross section of an optical cable in one embodiment of the present invention is shown.

[0053] Figure 3A schematic diagram illustrating a state of collecting optical signals according to an embodiment of the present invention is shown.

[0054] Figure 4 A schematic diagram illustrating calculation of the settlement S at different depths y using the deepest endpoint of a cylindrical elastic support as the coordinate origin in one embodiment of the present invention. DETAILED DESCRIPTION

[0055] Example

[0056] like Figures 1 to 3 As shown, the foundation settlement monitoring device with a spirally wound distributed optical fiber includes a cylindrical elastic support 1 vertically arranged in the foundation soil 11, and a counterweight 3 arranged at the lower end of the cylindrical elastic support 1 and located in the stable stratum 12 below the foundation soil 11;

[0057] The upper end of the counterweight 3 includes a connection surface that is larger than the lower end surface of the cylindrical elastic support 1 and is tightly connected to the lower end surface of the cylindrical elastic support 1;

[0058] The cylindrical surface of the cylindrical elastic support 1 is spirally wound with an optical cable 2;

[0059] The optical cable 2 is fixed to the cylindrical surface of the cylindrical elastic support 1, and the upper end thereof extends from the foundation soil 11 and is connected to the test unit 4;

[0060] The optical cable 2 includes a strain sensing optical fiber 7;

[0061] The strain sensing optical fiber 7 and the elastic sheath 10 of the optical cable 2 are fixed together by bonding;

[0062] The testing unit 4 obtains the optical signal flowing through the optical cable 2, and converts the optical signal into a digital signal and transmits it to the data processing unit 5;

[0063] The data processing unit 5 calculates the soil settlement value at each position of the foundation soil 11 within the range of the optical cable 2 spirally wound around the cylindrical elastic support 1 based on the difference between the digital signals obtained twice from the testing unit 4 .

[0064] The present invention fixes the optical cable 2 containing the strain sensing optical fiber 7 on the cylindrical surface of the cylindrical elastic support 1 in a spirally wound manner, so that the strain sensing optical fiber 7 only collects a part of the vertical settlement deformation of the foundation soil 1. At the same time, the length of the strain sensing optical fiber 7 per unit space is increased by the spiral winding method, thereby solving the defect that the measurable range of the distributed optical fiber is very limited due to the extremely small ultimate tensile strain, and is only suitable for measuring the settlement of soil with small deformation.

[0065] In practical applications, the counterweight 3 has a pre-stretching effect on the cylindrical elastic support 1 and can ensure the verticality of the foundation settlement sensor.

[0066] In practical applications, the counterweight 3 can be made of materials such as steel, cement concrete, etc.

[0067] In some embodiments, the optical cable 2 further includes a temperature sensing optical fiber 8;

[0068] The temperature sensing optical fiber 8 is provided with a plastic sleeve 9 that can slide relatively along the axis;

[0069] The plastic sleeve 9 and the elastic sheath 10 are fixed together by bonding.

[0070] In practical applications, the temperature sensing optical fiber 8 is arranged in the plastic sleeve 9 and can move freely without constraint to measure temperature. The temperature measured by the temperature sensing optical fiber 8 is used by the data processing unit 5 to eliminate the deviation caused by temperature changes when performing calculations, thereby realizing temperature self-compensation.

[0071] In some embodiments, the bolt lead angle 6 of the helically wound optical cable 2 is 30 degrees to 80 degrees.

[0072] In some embodiments, the cylindrical surface of the cylindrical elastic support 1 is provided with a spiral groove corresponding to the spirally wound optical cable 2 and matching the optical cable 2;

[0073] The spiral groove matching the optical cable 2 means that the optical cable 2 can be embedded and fixed in the spiral groove.

[0074] In practical applications, the spiral groove is not only used to fix the optical cable 2, but also can enhance the deformation coordination ability between the cylindrical elastic support 1 and the soil, thereby improving measurement accuracy.

[0075] In some embodiments, the outer diameter of the cylindrical elastic support 1 is 5 cm to 15 cm and is made of rubber or silicone;

[0076] The elastic sheath 10 is made of PE material.

[0077] In some embodiments, the testing unit 4 is an optical fiber demodulation device, which is used to demodulate the optical signal obtained from the optical cable 2, that is, the optical fiber frequency value, and convert the optical signal into a digital signal.

[0078] In some embodiments, the data processing unit 5 is an analysis terminal of a computer, which uses the digital signal obtained from the testing unit 4 to calculate the soil settlement value at each position of the foundation soil 11 within the range of the optical cable 2 spirally wrapped around the cylindrical elastic support 1.

[0079] The present invention also provides a method for using a foundation settlement monitoring device with a helically wound distributed optical fiber. The data processing unit 5 calculates the settlement S at a certain depth within the range of the optical cable 2 helically wound around the cylindrical elastic support 1 in the foundation soil 11 based on the difference between the digital signals obtained from the testing unit 4 twice. The calculation formula is as follows:

[0080]

[0081]

[0082] Wherein, L is the length of the optical cable 2 spirally wound on the cylindrical elastic support 1;

[0083] C is the spatial resolution parameter used by test unit 4 when collecting data;

[0084] θ is the bolt lead angle 6 of the spirally wound optical cable 2;

[0085] k is the strain proportionality coefficient of the strain sensing optical fiber 7 in the optical cable 2;

[0086] V is the Poisson's ratio of the cylindrical elastic support 1;

[0087] v ε0i is the frequency value of the strain sensing optical fiber 7 in the previous two digital signals obtained from the test unit 4;

[0088] v t0i is the frequency value of the temperature sensing optical fiber 8 in the previous two digital signals obtained from the test unit 4;

[0089] v εi is the frequency value of the strain sensing optical fiber 7 in the second digital signal obtained from the testing unit 4;

[0090] v ti The frequency value of the temperature sensing optical fiber 8 in the second digital signal obtained from the test unit 4;

[0091] ε f0i The strain of the optical cable 2 in the previous digital signal obtained from the test unit 4 for each of the two times;

[0092] ε fi The strain of the optical cable 2 is the latter of two digital signals obtained from the test unit 4;

[0093] ε s0i is the vertical strain of the cylindrical elastic support 1 in the previous digital signal obtained from the testing unit 4 twice;

[0094] ε si is the vertical strain of the cylindrical elastic support 1 in the latter of two digital signals obtained from the testing unit 4;

[0095] y is the vertical distance relative to the bottom end of the cylindrical elastic support 1.

[0096] like Figure 4 As shown, in actual application, the deepest end point of the cylindrical elastic support 1 is taken as the coordinate origin, that is, the depth there is 0, and the settlement S at different y-value positions in the vertical direction is calculated;

[0097] For example, the signal measured at the deepest part of the cylindrical elastic support 1 is the first value, which is recorded as i=1. The values measured upwards are recorded as i=2, 3, 4, etc., and the corresponding values are obtained. ε0i 、v t0i 、v εi 、v ti , ε f0i , ε fi , ε s0i and ε si , and then calculate the settlement S at different y-value positions.

[0098] In some embodiments, the maximum range S of the monitoring device max The calculation formula is as follows:

[0099]

[0100] Wherein, H is the total length of the cylindrical elastic support 1 .

[0101] In some embodiments, each time the test unit 4 needs to collect the optical signal of the optical cable 2 , the optical cable 2 is connected to the test unit 4 , and the optical cable 2 is disconnected from the test unit 4 at other times.

[0102] In actual application, when foundation settlement occurs or the time period for re-detection of settlement is reached, the optical signal is collected by connecting the optical cable 2 to the test unit 4; then the test unit 4 converts the optical signal into a digital signal and transmits it to the data processing unit 5.

[0103] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A foundation settlement monitoring device with a spirally wound distributed optical fiber; characterized in that: It comprises a cylindrical elastic support (1) vertically arranged in foundation soil (11), and a counterweight (3) arranged at the lower end of the cylindrical elastic support (1) and located in a stable stratum (12) below the foundation soil (11); The upper end of the counterweight (3) includes a connection surface that is larger than the lower end surface of the cylindrical elastic support (1) and is tightly connected to the lower end surface of the cylindrical elastic support (1); The cylindrical surface of the cylindrical elastic support (1) is spirally wound with an optical cable (2); The optical cable (2) is fixed to the cylindrical surface of the cylindrical elastic support (1), and the upper end thereof extends from the foundation soil (11) and is connected to the test unit (4); The optical cable (2) includes a strain sensing optical fiber (7); The strain sensing optical fiber (7) and the elastic sheath (10) of the optical cable (2) are fixed integrally by bonding; The testing unit (4) acquires the optical signal flowing through the optical cable (2), converts the optical signal into a digital signal and transmits it to the data processing unit (5); The data processing unit (5) calculates the soil settlement value of each position of the foundation soil (11) within the range of the optical cable (2) spirally wound around the cylindrical elastic support (1) based on the difference between the digital signals obtained from the testing unit (4) twice; The data processing unit (5) calculates the settlement S at a certain depth within the range of the optical cable (2) spirally wound around the cylindrical elastic support (1) in the foundation soil (11) based on the difference between the digital signals obtained from the testing unit (4) twice. The calculation formula is as follows: Wherein, L is the length of the optical cable (2) spirally wound on the cylindrical elastic support (1); C is the spatial resolution parameter used by the test unit (4) when collecting data; θ is the bolt lift angle (6) of the helically wound optical cable (2); k is the strain proportionality coefficient of the strain sensing optical fiber (7) in the optical cable (2); V is the Poisson's ratio of the cylindrical elastic support (1); v ε0i is the frequency value of the strain sensing optical fiber (7) in the previous digital signal obtained from the test unit (4) twice; v t0i The frequency value of the temperature sensing optical fiber (8) in the digital signal obtained from the test unit (4) twice before; v εi is the frequency value of the strain sensing optical fiber (7) in the latter of the two digital signals obtained from the test unit (4); v ti The frequency value of the temperature sensing optical fiber (8) in the latter of two digital signals obtained from the test unit (4); ε f0i The strain of the optical cable (2) between two digital signals obtained from the test unit (4); ε fi The strain of the optical cable (2) is the latter of two digital signals obtained from the test unit (4); ε s0i is the vertical strain of the cylindrical elastic support (1) in the previous digital signal obtained from the testing unit (4) twice; ε si The vertical strain of the cylindrical elastic support (1) in the latter of two digital signals obtained from the test unit (4); y is the vertical distance relative to the bottom end of the cylindrical elastic support (1); The maximum measuring range S of the monitoring device max The calculation formula is as follows: Wherein, H is the total length of the cylindrical elastic support (1).

2. The ground settlement monitoring device of spirally wound distributed optical fiber according to claim 1, characterized in that: The optical cable (2) further includes a temperature sensing optical fiber (8); The temperature sensing optical fiber (8) is provided with a plastic sleeve (9) capable of relative sliding along the axis; The plastic sleeve (9) and the elastic sheath (10) are fixed as one body by bonding.

3. The ground settlement monitoring device of spirally wound distributed optical fiber according to claim 1, characterized in that: The bolt rise angle (6) of the spirally wound optical cable (2) is 30 degrees to 80 degrees.

4. The ground settlement monitoring device of spirally wound distributed optical fiber according to claim 1, characterized in that: The cylindrical surface of the cylindrical elastic support (1) is provided with a spiral groove corresponding to the spirally wound optical cable (2) and matching the optical cable (2); The spiral groove matching the optical cable (2) means that the optical cable (2) can be embedded and fixed in the spiral groove.

5. The ground settlement monitoring device of spirally wound distributed optical fiber according to claim 1, characterized in that: The cylindrical elastic support (1) has an outer diameter of 5 cm to 15 cm and is made of rubber or silicone; The elastic sheath (10) is made of PE material.

6. The ground settlement monitoring device of spirally wound distributed optical fiber according to claim 1, characterized in that: The test unit (4) is an optical fiber demodulation device, which is used to demodulate the optical signal obtained from the optical cable (2), that is, the optical fiber frequency value, and convert the optical signal into the digital signal.

7. The ground settlement monitoring device of spirally wound distributed optical fiber according to claim 1, characterized in that: The data processing unit (5) is an analysis terminal of a computer, and uses the digital signal obtained from the test unit (4) to calculate the soil settlement value of each position of the foundation soil (11) within the range of the optical cable (2) spirally wound around the cylindrical elastic support (1).

8. The ground settlement monitoring device of spirally wound distributed optical fiber according to claim 1, characterized in that: Each time the test unit (4) needs to collect the optical signal of the optical cable (2), the optical cable (2) is connected to the test unit (4); at other times, the optical cable (2) is disconnected from the test unit (4).

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