Method for applying a metal strip multipoint displacement sensor in a subgrade settlement model test

Abstract

This invention discloses a method for applying a metal strip multi-point displacement sensor in a roadbed settlement model test, comprising the following steps: Step 1: Soil compaction test: The purpose of determining the optimal moisture content and maximum dry density in the soil compaction test is to detect parameters such as roadbed compaction degree and strength, which plays a very important role in improving the quality of roadbed construction. In this invention, when the roadbed soil undergoes settlement deformation, it causes a change in the fiber Bragg grating of the metal strip multi-point displacement sensor. The demodulator analyzes the drift of the reflected light wavelength of the fiber Bragg grating, and the settlement displacement at multiple points of the sensor can be calculated simultaneously. This solves the problem of objectively and accurately measuring the internal soil settlement deformation in roadbed settlement model tests.

Description

Technical Field

[0001] This invention relates to the field of sensing and data transmission technology, and more specifically to a method for applying a metal strip multi-point displacement sensor in a roadbed settlement model test. Background Technology

[0002] Before the construction of buildings and geotechnical structures, the foundation already contains self-weight stress caused by the soil's own weight. The loads of buildings and geotechnical structures are transferred to the foundation through the bottom surface of the foundation or embankment, changing the original stress state of the natural soil layers. Under the action of additional triaxial stress components, vertical, lateral, and shear deformations occur in the foundation, leading to vertical and lateral displacements at various points. The vertical deformation of the foundation surface is called foundation settlement. In highway and railway engineering, uneven subgrade settlement is a common problem, affecting the service life and driving quality of road projects and causing traffic safety hazards. Due to my country's vast geographical distribution and the different properties of subgrade soil in different road projects, the factors affecting subgrade settlement deformation vary. Conducting model tests is an efficient and reliable scientific research method, helping to better reflect the evolution of subgrade settlement problems and solve key technical problems encountered in engineering.

[0003] In subgrade settlement model tests, the selected sensing technology and sensors directly affect the accuracy and reliability of the test results. Because the internal soil deformation during subgrade settlement cannot be objectively and accurately measured, a new technical solution is needed to address this issue. Summary of the Invention

[0004] The purpose of this invention is to provide a method for using a metal strip multi-point displacement sensor in roadbed settlement model tests, which solves the problem that it is difficult to objectively and accurately measure the internal soil settlement deformation in roadbed settlement model tests.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for using a metal strip multi-point displacement sensor in a roadbed settlement model test, comprising the following steps:

[0006] Step 1: Soil compaction test: The purpose of determining the optimal moisture content and maximum dry density in the soil compaction test is to detect parameters such as the compaction degree and strength of the subgrade, which plays a very important role in improving the construction quality of the subgrade.

[0007] Step 2: Old roadbed filling: The soil is mixed to the optimal moisture content by sprinkling water and stirring at the same time. After the soil has been left to stand for 24 hours, it is filled in layers in a model box, with each layer being 3cm thick and the compaction degree controlled at about 95%.

[0008] Step 3: Step excavation: Excavate the old roadbed soil in steps according to the pre-designed dimensions. Each step is 12.5cm high and 20cm wide.

[0009] Step 4: Filling the new subgrade soil: Fill the new subgrade soil in layers according to the method of filling the old subgrade soil. During the test, the difference in the compaction degree of the new and old subgrade soils is reflected by strictly controlling the difference in compaction degree. The compaction degree of the new subgrade soil is controlled at about 80%.

[0010] Step 5: Install geogrid and metal strip multi-point displacement sensor: Before filling the new roadbed, lay geogrid and install metal strip multi-point displacement sensor at the steps of each layer of fill. The metal strip multi-point displacement sensor is used to measure the settlement and deformation of the soil in the model test.

[0011] Step 6: Loading Scheme: Place a steel bearing plate with dimensions of 16cm*30cm*1cm on top of the newly filled roadbed soil. The loading system consists of jacks and reaction frames. The force applied by the jacks acts on the rigid bearing plate through the I-beam reaction frame. Each loading level is 16kN, and a total of 20 load levels are applied. A dial gauge records the settlement data of the bearing plate in real time.

[0012] Step 7: Experimental Data Monitoring: Connect the jumpers on the upper and lower metal strip multi-point displacement sensors to the fiber Bragg grating demodulator. The sensor has a total of 10 measurement points, that is, 5 measurement points are arranged on each side of the metal strip surface at the designed positions, corresponding to 10 data points in the computer data acquisition system. Check whether each wavelength is normal. After everything is ready, start monitoring and then start loading.

[0013] Step 8: Data Processing: After the experiment, the data from each measuring point were organized. A total of 20 sets of experiments were conducted. When the load stabilized after each loading stage, the fiber wavelength remained relatively stable. At this time, it was assumed that the soil strain also remained in a stable state. The strain at each measuring point under the stable state after each loading stage was recorded, and the displacement was calculated. Thus, the settlement change curve from the step wall to the slope edge could be plotted.

[0014] In a preferred embodiment of the present invention, the manufacturing step of the metal strip multi-point displacement sensor in step 5 includes the following steps:

[0015] Step 1: Material preparation: The materials include: a metal strip, fixing glue, 10 fiber Bragg gratings of different wavelengths, fiber optic cleaver, fiber optic fusion splicer, marker pen, wire stripper, measuring ruler, sheath and patch cord;

[0016] Step 2: The production steps are as follows:

[0017] S1: Mark the positions of the fiber Bragg grating measurement points on the metal strip with a marker according to the pre-set positions.

[0018] S2: Use wire strippers to strip the fiber coating, measure the required cutting position with a ruler, cut with a fiber optic cleaver, and then use a fiber optic fusion splicer to fuse the two cut flat surfaces. At this point, the two measuring points have been connected in series, and other measuring points are connected in series in the same way.

[0019] S3: Select one side of the metal strip, attach the completed optical fiber to the center of the metal strip, one person fixes the position of the optical fiber, and another person applies the fixing glue. After completion, allow it to air dry for a certain period of time.

[0020] S4: Cover the bare wire portion without adhesive with a sheath and connect the jumper wire.

[0021] S5: Select the other side of the metal strip and repeat steps S3 and S4 above.

[0022] In a preferred embodiment of the present invention, the metal strip in step 1 has a thickness of 0.04 cm and a width of 3 cm.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] The metal strip multi-point displacement sensor used in this invention employs fiber Bragg grating sensing technology, which uses light waves as the carrier and optical fibers as the transmission medium. It senses the changes in parameters of the measured medium by detecting the shift in the center wavelength caused by changes in the period and refractive index of the fiber Bragg grating. When the external soil settles and deforms, it will cause changes in the fiber Bragg grating itself. The demodulator analyzes the drift of the reflected light wavelength of the fiber Bragg grating, thereby obtaining the subgrade settlement deformation. This solves the problem that it is difficult to objectively and accurately measure the internal soil settlement deformation in subgrade settlement model tests. Attached Figure Description

[0025] Figure 1 This is a side view of the experimental model of the present invention;

[0026] Figure 2 This is a top view schematic diagram of the sensor measuring point location arrangement according to the present invention;

[0027] Figure 3 This is a side view schematic diagram of the sensor of the present invention;

[0028] Figure 4 This is a diagram showing the settlement and displacement of the roadbed soil measured by the sensor of this invention. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Please see Figure 1-3 This invention provides a technical solution: a method for using a metal strip multi-point displacement sensor in a roadbed settlement model test, comprising the following steps:

[0031] Step 1: Soil compaction test: The purpose of determining the optimal moisture content and maximum dry density in the soil compaction test is to detect parameters such as the compaction degree and strength of the subgrade, which plays a very important role in improving the construction quality of the subgrade.

[0032] Step 2: Old roadbed filling: The soil is mixed to the optimal moisture content by sprinkling water and stirring at the same time. After the soil has been left to stand for 24 hours, it is filled in layers in a model box, with each layer being 3cm thick and the compaction degree controlled at about 95%.

[0033] Step 3: Step excavation: Excavate the old roadbed soil in steps according to the pre-designed dimensions. Each step is 12.5cm high and 20cm wide.

[0034] Step 4: Filling the new subgrade soil: Fill the new subgrade soil in layers according to the method of filling the old subgrade soil. During the test, the difference in the compaction degree of the new and old subgrade soils is reflected by strictly controlling the difference in compaction degree. The compaction degree of the new subgrade soil is controlled at about 80%.

[0035] Step 5: Install geogrid and metal strip multi-point displacement sensor: Before filling the new roadbed, lay geogrid and install metal strip multi-point displacement sensor at the steps of each layer of fill. The metal strip multi-point displacement sensor is used to measure the settlement and deformation of the soil in the model test.

[0036] Step 6: Loading Scheme: Place a steel bearing plate with dimensions of 16cm*30cm*1cm on top of the newly filled roadbed soil. The loading system consists of jacks and reaction frames. The force applied by the jacks acts on the rigid bearing plate through the I-beam reaction frame. Each loading level is 16kN, and a total of 20 load levels are applied. A dial gauge records the settlement data of the bearing plate in real time.

[0037] Step 7: Experimental Data Monitoring: Connect the metal strip multi-point displacement sensor to the fiber Bragg grating demodulator via a jumper cable. The sensor has a total of 10 measuring points, with 5 measuring points arranged on each side of the metal strip surface at the designed locations. These correspond to 10 data points in the computer's data acquisition system. Check that each wavelength is normal. Once everything is ready, start monitoring and loading.

[0038] Step 8: Data Processing: After the experiment, the data from each measuring point were organized. A total of 20 sets of experiments were conducted. When the load stabilized after each loading stage, the fiber wavelength remained relatively stable. At this time, it was assumed that the soil deformation also remained in a stable state. The fiber Bragg grating wavelength in the sensor at each measuring point under the stable state after each loading stage was recorded. After conversion, the displacement was obtained, and thus the settlement change curve from the step wall to the slope edge could be plotted.

[0039] This paper describes a fiber Bragg grating (FBG) sensing technology that utilizes a metal strip multi-point displacement sensor with light waves as the carrier and optical fiber as the transmission medium. It senses changes in the parameters of the measured medium by detecting the shift in the center wavelength caused by changes in the FBG's period and refractive index. When the metal strip multi-point displacement sensor deforms, it causes a change in the FBG itself. The demodulator analyzes the drift of the reflected light wavelength from the FBG, and the displacement at multiple points on the sensor can be calculated simultaneously. This technology solves the problem of objectively and accurately measuring the internal soil settlement deformation in roadbed settlement model tests.

[0040] In a further improvement, the fabrication step of the metal strip multi-point displacement sensor in step 5 includes the following steps:

[0041] Step 1: Material preparation: The materials include: 1 metal strip, fixing glue, ten fiber Bragg gratings of different wavelengths, fiber optic cleaver, fiber optic fusion splicer, marker pen, wire stripper, measuring ruler, sheath and patch cord.

[0042] Step 2: The production steps are as follows:

[0043] S1: Mark the positions of the fiber Bragg grating measurement points on the metal strip with a marker according to the pre-set positions.

[0044] S2: Use wire strippers to strip the fiber coating, measure the required cutting position with a ruler, cut with a fiber optic cleaver, and then use a fiber optic fusion splicer to fuse the two cut flat surfaces. At this point, the two measuring points have been connected in series, and other measuring points are connected in series in the same way.

[0045] S3: Select one side of the metal strip, attach the completed optical fiber to the center of the metal strip, one person fixes the position of the optical fiber, and another person applies the fixing glue. After completion, allow it to air dry for a certain period of time.

[0046] S4: Cover the bare wire portion without adhesive with a sheath and connect the jumper wire.

[0047] S5: Select the other side of the metal strip and repeat steps S3 and S4 above.

[0048] In a further improvement, the thickness of the metal strip in step 1 is 0.04 cm and the width is 3 cm.

[0049] This invention employs a metal strip multi-point displacement sensor, utilizing fiber Bragg grating (FBG) sensing technology with light waves as the carrier and optical fiber as the transmission medium. Sensing is achieved by detecting changes in the parameters of the measured medium through the shift in the center wavelength caused by changes in the FBG's period and refractive index. When the metal strip multi-point displacement sensor deforms, it causes a change in the FBG itself. The demodulator analyzes the drift of the reflected light wavelength from the FBG, and the displacement at multiple points on the sensor can be calculated simultaneously. This solves the problem of objectively and accurately measuring the internal soil settlement deformation in roadbed settlement model tests.

[0050] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for using a metal strip multipoint displacement sensor in a subgrade settlement model test, characterized in that: The method for applying the metal strip type multi-point displacement sensor in the subgrade settlement model test comprises the following steps. Step 1: soil compaction test: the purpose of obtaining the optimum water content and the maximum dry density in the soil compaction test is to detect the compaction degree and strength of the subgrade, which plays a very important role in improving the construction quality of the subgrade; Step 2: old subgrade filling: the soil is adjusted to the optimum water content by the method of spraying water while stirring, and after the soil is allowed to stand for 24 hours, the soil is filled and compacted in the model box in layers, with a thickness of 3 cm for each layer, and the compaction degree is controlled at 95%; Step 3: step excavation: the old subgrade soil is excavated according to the size designed in advance, with a height of 12.5 cm and a width of 20 cm for each layer; Step 4: filling of new subgrade soil: the new subgrade soil is filled in layers according to the method of filling the old subgrade soil, and the difference in the compaction degree of the new and old subgrade soil is reflected by strictly controlling the difference in the compaction degree of the new and old subgrade soil during the test, and the compaction degree of the new subgrade soil is controlled at 80%; Step 5: laying of geogrid and metal strip type multi-point displacement sensor: the geogrid and the metal strip type multi-point displacement sensor are laid at the steps of each layer of filling soil before the new subgrade is filled, and the metal strip type multi-point displacement sensor is used to measure the settlement deformation of the soil body of different layers in the model test; The manufacturing steps of the metal strip type multi-point displacement sensor comprise the following steps. Step 51: material preparation: the manufacturing materials comprise a metal strip, fixing glue, 10 optical fibers with different wavelengths, an optical fiber cutting machine, an optical fiber fusion splicer, a marker pen, wire strippers, a measuring scale, a sheath and a jumper wire; Step 52: the manufacturing steps are as follows: S1: according to the position of the optical fiber Bragg grating measuring point on the metal strip designed in advance, the position is marked on the metal strip with a marker pen; S2: the optical fiber coating layer is stripped with the wire strippers, the required cutting position is measured with the measuring scale, the optical fiber cutting machine is used for cutting, and the optical fiber fusion splicer is used for fusing the two cut flat sections, at this time, the two measuring points have been connected in series, and the other measuring points are also connected in series in this way; S3: one side of the metal strip is selected, the completed optical fiber is pasted to the middle position of the metal strip, one person fixes the position of the optical fiber, and the other person applies the fixing glue, and the completed product is dried for a certain period of time; S4: the bare wire part not applied with the glue is sheathed with the sheath and connected with the jumper wire; S5: the other side of the metal strip is selected, and the above steps S3 and S4 are repeated; Step 6: loading scheme: a steel bearing plate with a size of 16 cm*30 cm*1 cm is placed on the upper part of the new subgrade soil, and the loading system is composed of a jack and a counterforce frame, the force applied by the jack is applied to the rigid bearing plate through the I-shaped steel counterforce frame, the size of each level of loading is 16 kN, a total of 20 levels of load are applied, and the dial gauge records the settlement data of the bearing plate in real time; Step 7: experimental data monitoring: after the metal strip type multi-point displacement sensors in each layer are connected with the jumper wire and connected to the optical fiber Bragg grating demodulator, it is checked whether each wavelength is normal, after everything is ready, the monitoring is started, and the loading can be started. Step 8: data processing: after the end of the test, the data of each measuring point is arranged, and the experiment is carried out for 20 groups. After each level of loading, the wavelength of the optical fiber remains relatively stable, and at this time, it is determined that the soil strain also remains in a stable state. The strain of each measuring point after each level of loading is recorded, and the displacement is obtained after conversion, so that the settlement change curve from the step wall to the slope edge in this direction can be drawn.

2. The method for using the metal strip multipoint displacement sensor in the roadbed settlement model test according to claim 1, characterized in that: The thickness of the metal strip in step 51 is 0.04 cm, and the width is 3 cm.

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