CN107727483B - Penetration shearing device and method for foundation in-situ test based on fiber bragg grating - Google Patents
Penetration shearing device and method for foundation in-situ test based on fiber bragg grating Download PDFInfo
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- 239000000835 fiber Substances 0.000 title claims abstract description 108
- 238000012360 testing method Methods 0.000 title claims abstract description 50
- 238000010008 shearing Methods 0.000 title claims abstract description 43
- 230000035515 penetration Effects 0.000 title claims abstract description 28
- 238000011065 in-situ storage Methods 0.000 title claims abstract description 26
- 238000000034 method Methods 0.000 title claims abstract description 26
- 239000000523 sample Substances 0.000 claims abstract description 96
- 239000002689 soil Substances 0.000 claims abstract description 40
- 238000005553 drilling Methods 0.000 claims abstract description 24
- 230000000149 penetrating effect Effects 0.000 claims abstract description 5
- 239000002184 metal Substances 0.000 claims description 36
- 230000008054 signal transmission Effects 0.000 claims description 23
- 239000013307 optical fiber Substances 0.000 claims description 20
- 239000012528 membrane Substances 0.000 claims description 18
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- 239000003822 epoxy resin Substances 0.000 claims description 4
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- 238000012544 monitoring process Methods 0.000 abstract description 6
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- 238000005452 bending Methods 0.000 description 3
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- 230000035945 sensitivity Effects 0.000 description 3
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/24—Investigating strength properties of solid materials by application of mechanical stress by applying steady shearing forces
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Abstract
The invention relates to a penetration shearing device and a penetration shearing method for foundation in-situ test based on fiber gratings. Comprises a multifunctional probe, a rotary drilling device, a fiber bragg grating wireless demodulator, a case shell and a base. The multifunctional probe comprises a Y-shaped plate head and a cone tip measuring head, and the cone tip measuring head is arranged at the bottom end of the Y-shaped plate head; the rotary drilling device comprises a probe rod, a chuck, a stepping motor, a pressing-in host, a mounting platform and a fixing device; the probe rod penetrates through the whole rotary drilling device from bottom to top, sequentially penetrates through the chuck, the stepping motor, the mounting platform and the pressing-in host machine, and the bottom is connected with the multifunctional probe; the in-situ test method comprises the following steps: clearing a field and positioning; penetrating; shearing; sequentially pressing down the multifunctional probe into soil layers with different depths, and repeating the steps; and (5) pulling out the multifunctional probe to finish the test. The invention has the advantages of high accuracy, good stability, good waterproofness, strong electromagnetic interference resistance, multi-parameter monitoring, automatic real-time monitoring and the like.
Description
Technical field:
the invention relates to the field of optical fiber sensing and foundation in-situ testing, in particular to a penetration shearing device and method for foundation in-situ testing based on an optical fiber grating.
The background technology is as follows:
soil body is used as a naturally-generated three-phase medium, and generally has the characteristics of high water content, large pore ratio, high compressibility, low shear strength and the like, and has great harm in engineering construction, so that the problems of foundation damage, slope instability and the like are often caused. Therefore, the rapid and effective determination of the physical and mechanical properties of the foundation soil mass is an important subject in geotechnical engineering. At present, common in-situ foundation testing methods comprise a flat plate load test, a cross plate shearing test, a static cone penetration test and the like.
In general, the flat plate load test is an in-situ test method for determining the bearing capacity of the foundation most directly and relatively accurately, but the method is high in cost, time-consuming and labor-consuming, and limits the application of the method in engineering. The cross plate shearing test is mostly manually operated, and the manual error is large. In recent years, the electric measuring type cross plate shearing test and the static sounding test are perfect in theory, have the advantages of rapidness, economy, labor saving and the like, but the two methods can only measure a single physical quantity, the measuring precision of the strain gauge is limited, electromagnetic interference can be possibly caused in the field test process, the strain gauge is easy to generate short circuit in a humid environment, and the method is not suitable for testing the soil body of the water-rich stratum.
The optical fiber sensor has been rapidly developed in recent years due to the advantages of high sensitivity, good stability, corrosion resistance, electromagnetic interference resistance, quasi-distributed type, and the like. The fiber Bragg grating (fiberBragg grating, abbreviated as fiber Bragg grating) is a mature fiber sensing technology at present, is widely applied to various fields of geological engineering, geotechnical engineering, hydraulic engineering and the like, and provides a powerful tool for the innovation of a foundation in-situ test method. The sensing principle of the fiber grating is that when broadband incident light enters the fiber, the fiber grating reflects light with specific wavelength, and the center wavelength lambda of the reflected light B And the strain delta epsilon and the temperature delta TThe following relationship:
wherein: k (K) ε K is the strain sensing sensitivity coefficient T As a temperature sensing sensitivity coefficient, deltalambda B Is the amount of change in the center wavelength. For a general fiber grating sensor, K ε ≈0.78×10 -6 με -1 ，K T ≈6.67×10 -6 ℃ -1 . The central wavelength of the fiber bragg grating is extremely sensitive to temperature and strain, so the fiber bragg grating strain sensor and the temperature sensor have high precision. Meanwhile, fiber gratings with different center wavelengths can be used in series to form a quasi-distributed sensing sequence, so that automatic acquisition of strain or temperature data along the fiber is realized.
Disclosure of Invention
Aiming at the defects of the existing foundation in-situ test technology, the invention aims to provide a penetration shearing device and a penetration shearing method for foundation in-situ test based on an optical fiber grating. Compared with the traditional method, the method has the advantages of high accuracy, good stability, good waterproofness, strong electromagnetic interference resistance, multi-parameter monitoring, automatic real-time monitoring and the like, can simultaneously acquire cone tip resistance, soil shear strength and probe temperature, and realizes the functions of automatic acquisition, remote transmission and the like of monitoring data through the fiber bragg grating wireless demodulator.
The invention adopts the following technical scheme: the penetration shearing device comprises a multifunctional probe, a rotary drilling device, a fiber grating wireless demodulator, a chassis shell and a base, wherein the multifunctional probe penetrates through the base to penetrate into soil of the foundation, the other end of the rotary drilling device is connected with the fiber grating wireless demodulator through a signal transmission fiber, the chassis shell is arranged outside the rotary drilling device, and the chassis shell is connected with the base; the multifunctional probe comprises a Y-shaped plate head and a cone tip measuring head, and the cone tip measuring head is arranged at the bottom end of the Y-shaped plate head; the rotary drilling device comprises a probe rod, a chuck, a stepping motor, a mounting platform, a pressing-in host and a fixing device, wherein the probe rod penetrates through the whole rotary drilling device from bottom to top, sequentially penetrates through the chuck, the stepping motor, the mounting platform and the pressing-in host, and the bottom of the probe rod is connected with a multifunctional probe; the rotary drilling device is arranged on the inner wall of the case shell through a fixing device; the lower part of the base is provided with a roller and a support.
The Y-shaped plate head consists of three triangular metal side plates with included angles of 120 degrees, each metal side plate is provided with a side plate fiber grating strain sensor, and the side plate fiber grating strain sensors are connected in series through signal transmission fibers.
The side plate of the Y-shaped plate head is carved with a slot, the side plate fiber grating strain sensor is tightly adhered in the middle of the slot, and the surface is covered with a layer of epoxy resin.
The cone tip measuring head is sequentially provided with a cone tip, a force transmission column, an elastic metal diaphragm, a cone tip fiber bragg grating strain sensor and a fiber bragg grating temperature sensor from bottom to top; the cone-tip fiber bragg grating strain sensor is tightly attached to the elastic metal diaphragm and is connected with the fiber bragg grating temperature sensor in series through the signal transmission fiber.
The elastic metal membrane is a round thin plate with the same thickness and fixed on the periphery.
The detecting rod is single or a plurality of detecting rods connected in series, the side edge of the detecting rod is provided with a thin seam, and the signal transmission optical fiber is just allowed to pass through the thin seam and is placed in the hollow part of the detecting rod.
The method for using the penetration shearing device for foundation in-situ test based on the fiber bragg grating comprises the following steps:
1) Clearing and seating: cleaning and leveling a field to be measured, fixing a device base above a foundation to be measured, and connecting a signal transmission optical fiber to a fiber grating wireless demodulator;
2) Penetrating: the main machine is pressed in to provide thrust, the multifunctional probe is vertically penetrated into the depth of the foundation to be tested, and the cone tip resistance and the temperature change of the multifunctional probe are measured;
3) Shearing: the probe rod is clamped by a chuck and stands for a plurality of minutes, the multifunctional probe slowly rotates in a soil layer at a preset shearing rate under the action of a stepping motor until surrounding soil is completely sheared, and the shearing strength of foundation soil is measured;
4) And (3) re-penetrating: after one test is completed, standing for a plurality of minutes, pressing down the multifunctional probe to each depth to be tested, and repeating the operations of the step 2 and the step 3;
5) And (5) taking out: after the test is finished, the probe rod is slowly pulled out of the soil, the multifunctional probe is cleaned, all data in the test are collected and recorded in real time by the fiber grating wireless demodulator and stored locally and/or uploaded to the cloud sensor for measurement, and the data are used for temperature compensation of the fiber grating strain sensor.
The cone tip resistance of the multifunctional probe in the step (2) is deduced through a theoretical formula:in p s Resistance of the cone tip; epsilon is tangential strain of the elastic metal membrane and is measured by a conical tip fiber bragg grating strain sensor attached to the elastic metal membrane; E. h and v are respectively the elastic modulus, thickness and poisson ratio of the elastic metal membrane.
The foundation soil shear strength in the step (3) is deduced through a theoretical formula:wherein: τ f The shear strength of foundation soil is obtained, and E is the elastic modulus of the Y-shaped plate head side plate; alpha is the ratio of the axial strain to the radial strain of the side plate during shearing, and is determined by a calibration test; epsilon 1 、ε 2 、ε 3 Radial strain on each side plate of the Y-shaped plate head is measured by a side plate fiber bragg grating strain sensor attached to the side plate; r, H are the radius and height of the Y-shaped plate head, respectively.
Advantageous effects
1. Compared with the traditional electrical measuring cross plate shearing instrument and static cone penetration test, the invention has the advantages of high accuracy, good stability, good waterproofness and strong electromagnetic interference resistance, and can not generate short circuit due to moisture caused by aging of the instrument or poor tightness, etc., thus being suitable for in-situ test of the soil body of the water-rich stratum.
2. The invention can obtain a plurality of physical quantities, including cone tip resistance, shear strength and probe temperature, and three groups of monitoring data can be compared with each other and verified, thus having important significance for correctly evaluating the physical and mechanical properties of soil and the engineering geological conditions on site.
3. Compared with the traditional cross plate shearing instrument, the Y-shaped plate head is adopted, so that the Y-shaped plate head is easier to penetrate into soil, and disturbance to in-situ soil in the testing process is reduced.
4. The automatic acquisition, remote transmission, real-time display and the like of the reading of the fiber bragg grating sensor are realized through the fiber bragg grating wireless demodulator.
Drawings
FIG. 1 is a schematic diagram of a fiber grating-based penetration shear device for in situ foundation testing according to a preferred embodiment of the present invention.
Wherein: 1. the device comprises a multifunctional probe, a rotary drilling device, a fiber bragg grating wireless demodulator, a case shell, a base, a 6.Y-shaped plate head, a 7-cone tip probe, an 8-probe rod, a 9-chuck, a 10-stepping motor, an 11-mounting platform, a 12-press-in host, a 13-fixing device, a 14-roller, a 16-side plate, a 17-fiber bragg grating strain sensor and an 18-signal transmission optical fiber.
FIG. 2 is a schematic view of a multi-functional probe according to a preferred embodiment of the present invention, including a Y-shaped plate head and a cone tip probe.
Wherein: 6.Y the shape of a Chinese character 'ji' is formed by a plate head, 7 a cone tip measuring head, 16 a side plate, 17-1 a side plate fiber bragg grating strain sensor, 17-2 a cone tip fiber bragg grating strain sensor, 18 a signal transmission fiber, 19 a cone tip, 20 a force transmission column, 21 an elastic metal diaphragm and 22 a fiber bragg grating temperature sensor.
FIG. 3 is a schematic view of the stress situation of the Y-shaped plate head side plate in the invention during shearing. Wherein τ f The shear strength of foundation soil is that F is the soil pressure born by the side plates, and 2 theta is the vertex angle of the conical shear surface.
FIG. 4 is a graph of test results including tip drag-depth, shear-strength-depth, temperature-depth curves, according to a preferred embodiment of the present invention.
Detailed Description
The technical scheme of the present invention will be described in more detail with reference to the accompanying drawings and preferred embodiments.
A penetration shearing device based on fiber bragg grating for foundation in-situ test comprises a multifunctional probe, a rotary drilling device, a fiber bragg grating wireless demodulator, a chassis shell and a base. The multifunctional probe comprises a Y-shaped plate head and a cone tip measuring head, and the cone tip measuring head is arranged at the bottom end of the Y-shaped plate head; the rotary drilling device comprises a probe rod, a chuck, a stepping motor, a mounting platform, a pressing-in host machine and a fixing device; the probe rod penetrates through the whole rotary drilling device from bottom to top, sequentially penetrates through the chuck, the stepping motor, the mounting platform and the pressing-in host machine, and the bottom is connected with the multifunctional probe; the rotary drilling device is arranged on the inner wall of the case shell through a fixing device; the multifunctional probe penetrates through the middle of the base and penetrates into the soil body of the foundation.
Preferably, the Y-shaped plate head consists of three triangular metal side plates with included angles of 120 degrees, each metal side plate is provided with a fiber grating strain sensor, and the three fiber grating strain sensors are connected in series through signal transmission fibers.
Preferably, the side plate of the Y-shaped plate head is carved with a slot, the fiber bragg grating strain sensor is tightly adhered in the middle of the slot, and the surface is covered with a layer of epoxy resin.
Preferably, the cone tip measuring head comprises a cone tip, a force transmission column, an elastic metal diaphragm, a fiber bragg grating strain sensor and a fiber bragg grating temperature sensor; the fiber grating strain sensor is clung to the elastic metal diaphragm and connected in series with the fiber grating temperature sensor.
Preferably, the elastic metal membrane is a round thin plate with the same thickness and fixed on the periphery, and is connected with the conical tip through a force transmission column; when the taper tip is subjected to resistance, the elastic metal membrane is bent and deformed to drive the fiber bragg grating strain sensor to generate strain.
Preferably, the top of the probe rod can be connected with more probe rods through threads so as to increase the penetration depth, and a thin slit is formed on the side edge of each probe rod, so that the signal transmission optical fiber is just allowed to pass through the thin slit and is placed in the hollow part of the probe rod.
Preferably, one end of the signal transmission fiber is connected with all fiber grating strain sensors and temperature sensors in series, and the other end of the signal transmission fiber penetrates through the probe rod and extends out of the case shell to be connected with the fiber grating wireless demodulator.
Further, the application method of the penetration shearing device for foundation in-situ test based on the fiber bragg grating comprises the following steps:
the first step is cleaning and positioning: and cleaning and leveling the field to be measured, fixing the device base above the foundation to be measured, and connecting the signal transmission optical fiber to the fiber bragg grating wireless demodulator.
Step two, penetrating: the main machine is pressed in to provide thrust, the multifunctional probe is vertically penetrated into the depth of the foundation to be tested, and the cone tip resistance and the temperature change of the multifunctional probe are measured.
The third step is shearing: the probe rod is clamped by a chuck and stands for a few minutes, the multifunctional probe slowly rotates in a soil layer at a preset shearing rate under the action of a stepping motor until surrounding soil is completely sheared, and the shearing strength of foundation soil is measured.
Step four, re-penetrating: after one test is completed, standing is performed for a plurality of minutes, the multifunctional probe is pressed down to each depth to be tested, and the operations of the step 2 and the step 3 are repeated.
And step five, taking out: after the test is completed, the probe rod is slowly pulled out of the soil, and the multifunctional probe is cleaned.
Preferably, the temperature of the multifunctional probe in the second step is measured by a fiber bragg grating temperature sensor in the cone tip probe, and is used for temperature compensation of a fiber bragg grating strain sensor.
Preferably, the cone tip resistance of the multifunctional probe in the second step is derived from a theoretical formula:
in p s Resistance of the cone tip; epsilon is tangential strain of the elastic metal membrane and is measured by an optical fiber grating strain sensor attached to the elastic metal membrane; E. h and v are respectively the elastic modulus, thickness and poisson ratio of the elastic metal membrane.
Preferably, the foundation soil shear strength in the third step is deduced through a theoretical formula:
wherein: τ f The shear strength of foundation soil; e is the elastic modulus of the Y-shaped plate head side plate; alpha is the ratio of the axial strain to the radial strain of the side plate during shearing, and is determined by a calibration test; epsilon 1 、ε 2 、ε 3 Radial strain on each side plate of the Y-shaped plate head is measured by a fiber bragg grating strain sensor attached to the side plate; r, H are the radius and height of the Y-shaped plate head, respectively.
Preferably, the temperature and strain data in the second, third and fourth steps are collected, recorded and stored locally by using a fiber bragg grating wireless demodulator in real time and/or uploaded to a cloud.
Examples
As shown in fig. 1 and fig. 2, the penetration shearing device for foundation in-situ test based on the fiber bragg grating comprises a multifunctional probe 1, a rotary drilling device 2, a fiber bragg grating wireless demodulator 3, a chassis shell 4 and a base 5. The multifunctional probe 1 comprises a Y-shaped plate head 6 and a cone tip measuring head 7, wherein the cone tip measuring head 7 is arranged at the bottom end of the Y-shaped plate head 6; the rotary drilling device 2 comprises a probe rod 8, a chuck 9, a stepping motor 10, a mounting platform 11, a pressing-in host 12 and a fixing device 13; the probe rod 8 penetrates through the whole rotary drilling device 2 from bottom to top, sequentially penetrates through the chuck 9, the stepping motor 10, the mounting platform 11 and the pressing-in host 12, and the bottom is connected with the multifunctional probe 1; the rotary drilling device 2 is arranged on the inner wall of the chassis shell 4 through a fixing device 13; the upper part of the base 5 is provided with a chassis shell 4, the lower part is provided with rollers 14 and a support, and the multifunctional probe 1 penetrates through the middle of the base 5 and penetrates into the soil body of the foundation.
In this embodiment, the Y-shaped plate head 6 is composed of three triangular metal side plates 16 with included angles of 120 ° and each other, the side plates 16 are made of stainless steel with a linear elastic stress-strain relationship, the dimension thickness d×height h×radius r=0.1 cm×10cm×5cm, each metal side plate 16 is engraved with a slot, a side plate fiber bragg grating strain sensor 17-1 is tightly adhered in the middle of the slot, the surface of the sensor is covered with a layer of epoxy resin, and the three side plate fiber bragg grating strain sensors 17-1 are mutually connected in series through the signal transmission optical fibers 18.
In this embodiment, the cone tip probe 7 includes a cone tip 19, a force transmission column 20, an elastic metal diaphragm 21, a cone tip fiber bragg grating strain sensor 17-2, and a fiber bragg grating temperature sensor 22. The taper-tip fiber grating strain sensor 17-2 is tightly attached to the elastic metal diaphragm 21 and is connected in series with the fiber grating temperature sensor 22. The elastic metal membrane 21 is a circular thin plate with a constant cross section and fixed on the periphery, and is connected with the conical tip 19 through the force transmission column 20, and when the conical tip 19 is subjected to resistance, the elastic metal membrane 21 is bent and deformed, so that the fiber bragg grating strain sensor 17-2 attached on the elastic metal membrane is driven to generate strain.
In this embodiment, the probe rod 8 is a single probe rod or a plurality of probe rods 8 connected in series by threads or other fasteners to increase penetration depth, and a slit is formed on the side of the probe rod 8 to allow the signal transmission optical fiber 18 to pass through the slit and be placed in the hollow portion of the probe rod 8. The signal transmission optical fiber 18 adopts a single-mode single-core tightly-packed optical fiber with the diameter of 0.9mm, one end of the signal transmission optical fiber 18 is connected with all the fiber bragg grating strain sensors 17 in series with the signal transmission optical fiber 18, and the other end of the signal transmission optical fiber passes through the hollow part of the probe rod 8 and extends out of the chassis shell 4 to be connected with the fiber bragg grating wireless demodulator 3.
The application method of the foundation in-situ testing device based on the fiber bragg grating provided by the embodiment comprises the following steps:
1) Clearing and seating: the field to be measured is cleaned and leveled, the device base 5 is fixed above the foundation to be measured, the base 5 level is adjusted, the signal transmission optical fiber 18 is connected to the fiber bragg grating wireless demodulator 3, the optical fiber signals are debugged, and the normal operation of all sensors is ensured.
2) Penetrating: the pressing-in main machine 12 provides a pushing force to vertically penetrate the multifunctional probe 1 to the depth of the foundation to be tested at a speed of about 20 mm/s. During penetration, the tip gauge head 7 measures tip resistance and temperature variation of the probe.
3) Shearing: the probe rod 8 is clamped by a chuck 9, and is kept stand for 2-5 minutes, and the Y-shaped plate head 6 slowly rotates in a soil layer at a shearing rate of 1 DEG/10 s under the action of a stepping motor 10 until the Y-shaped plate head 6 completely shears the surrounding soil body. The fiber bragg grating strain sensor 17-1 on the side plate 16 of the Y-shaped plate head 6 can measure the radial strain of the side plate 16 in the shearing process.
4) And (3) re-penetrating: after the test is completed, the multifunctional probe 1 is kept stand for a plurality of minutes, pressed down to each depth to be tested, and the operations of the second step and the third step are repeated. The temperature and strain data are acquired, recorded and uploaded to the cloud end in real time by using demodulation equipment and a computer, and are rapidly transmitted to clients such as a mobile phone, a computer and the like.
5) And (5) taking out: after the test is completed, the probe rod 8 is slowly pulled out of the soil, and the multifunctional probe 1 is cleaned so that the next test can be continued to be used.
In this embodiment, the temperature change of the multifunctional probe 1 is measured by the fiber bragg grating temperature sensor 22 in the cone tip probe 7, and in the process of penetration, the temperature of the probe is increased because of friction, in order to eliminate the influence of the temperature on the result of the fiber bragg grating strain sensor 17, the cone tip probe 7 at the tip of the probe is provided with the fiber bragg grating temperature sensor 22 for temperature compensation, and meanwhile, the resistance received during penetration can be calculated according to the change of the probe temperature.
In this embodiment, the relationship between the cone tip resistance of the multifunctional probe 1 and the tangential strain of the center of the elastic metal membrane is as follows:in p s Resistance of the cone tip; epsilon is tangential strain of the center of the elastic metal diaphragm 21 and is measured by a fiber bragg grating strain sensor 17-2 attached to the center; E. h and v are the elastic modulus, thickness and poisson's ratio of the elastic metal membrane 21, respectively.
This embodimentIn the method, the shear strength value of foundation soil is obtained by deriving the radial strain of the side plate 16 of the Y-shaped plate head 6 through a theoretical formula. The principle is that according to the bending moment M on the side plate 16 of the Y-shaped plate head 6 Board board Moment of resistance M to the axis, which should be equal to the shear force on the tapered side Side of the vehicle And the shearing resistance of the upper end face is opposite to the resistant moment M of the axle center End of the device The shear strength of foundation soil (fig. 3) is calculated by summing, namely: m is M Board board ＝M Side of the vehicle +M End of the device Wherein the resisting moment of the conical side surface isThe resisting moment of the end face is->The Y-shaped plate head 6 has three side plates 16 with bending moment of M 1 、M 2 、M 3 Wherein->M 2 、M 3 By analogy, total bending moment->Thus, the foundation soil has a shear strength of +.>Wherein: τ f The shear strength of foundation soil is obtained, and E is the elastic modulus of the side plate 16 of the Y-shaped plate head 6; alpha is the ratio of the axial strain to the radial strain of the side plate 16 during shearing, and is determined by a calibration test; epsilon 1 、ε 2 、ε 3 Radial strain on each side plate 16 of the Y-shaped plate head 6 respectively; r, H are the radius and height of the Y-shaped board head 6, respectively.
It should be noted that, in addition to the above embodiments, other embodiments of the present invention are also possible. All technical schemes formed by adopting equivalent replacement, equivalent transformation and modification fall within the protection scope of the patent claims of the invention.
Claims (7)
1. The method for using the penetration shearing device for foundation in-situ test based on the fiber bragg grating is characterized by comprising the following steps:
1) Clearing and seating: cleaning and leveling a field to be measured, fixing a device base above a foundation to be measured, and connecting a signal transmission optical fiber to a fiber grating wireless demodulator;
2) Penetrating: the main machine is pressed in to provide thrust, the multifunctional probe is vertically penetrated into the depth of the foundation to be tested, and the cone tip resistance and the temperature change of the multifunctional probe are measured; the cone tip resistance of the multifunctional probe is deduced through a theoretical formula:in p s Resistance of the cone tip; epsilon is tangential strain of the elastic metal membrane and is measured by a conical tip fiber bragg grating strain sensor attached to the elastic metal membrane; E. h and v are respectively the elastic modulus, thickness and poisson ratio of the elastic metal membrane;
3) Shearing: the probe rod is clamped by a chuck and stands for a plurality of minutes, the multifunctional probe slowly rotates in a soil layer at a preset shearing rate under the action of a stepping motor until surrounding soil is completely sheared, and the shearing strength of foundation soil is measured; the foundation soil shear strength is deduced through a theoretical formula:wherein: τ f The shear strength of foundation soil is obtained, and E is the elastic modulus of the Y-shaped plate head side plate; alpha is the ratio of the axial strain to the radial strain of the side plate during shearing, and is determined by a calibration test; epsilon 1 、ε 2 、ε 3 Radial strain on each side plate of the Y-shaped plate head is measured by a side plate fiber bragg grating strain sensor attached to the side plate; r, H the radius and the height of the Y-shaped plate head are respectively;
4) And (3) re-penetrating: after one test is completed, standing for a plurality of minutes, pressing down the multifunctional probe to each depth to be tested, and repeating the operations of the step 2 and the step 3;
5) And (5) taking out: after the test is finished, the probe rod is slowly pulled out of the soil, the multifunctional probe is cleaned, and all data in the test are collected, recorded and stored locally by the fiber grating wireless demodulator in real time and/or uploaded to the cloud;
the penetration shearing device based on the fiber bragg grating for the foundation in-situ test comprises a multifunctional probe, a rotary drilling device, a fiber bragg grating wireless demodulator, a chassis shell and a base, wherein the multifunctional probe penetrates through the base and penetrates into the foundation soil body, the other end of the penetration shearing device is connected with the rotary drilling device and then is connected with the fiber bragg grating wireless demodulator through a signal transmission fiber, the chassis shell is arranged outside the rotary drilling device, and the chassis shell is connected with the base; the multifunctional probe comprises a Y-shaped plate head and a cone tip measuring head, and the cone tip measuring head is arranged at the bottom end of the Y-shaped plate head; the rotary drilling device comprises a probe rod, a chuck, a stepping motor, a mounting platform, a pressing-in host and a fixing device, wherein the probe rod penetrates through the whole rotary drilling device from bottom to top, sequentially penetrates through the chuck, the stepping motor, the mounting platform and the pressing-in host, and the bottom of the probe rod is connected with a multifunctional probe; the rotary drilling device is arranged on the inner wall of the case shell through a fixing device; the lower part of the base is provided with a roller and a support.
2. The method for using the penetration shearing apparatus for foundation in-situ test based on the fiber bragg grating according to claim 1, wherein the Y-shaped plate head consists of three triangular metal side plates with included angles of 120 degrees, each metal side plate is provided with a side plate fiber bragg grating strain sensor, and the side plate fiber bragg grating strain sensors are mutually connected in series through signal transmission fibers.
3. The method for using the penetration shearing device for foundation in-situ test based on the fiber bragg grating as claimed in claim 1, wherein the side plate of the Y-shaped plate head is carved with a slot, the side plate fiber bragg grating strain sensor is tightly adhered in the middle of the slot, and the surface is covered with a layer of epoxy resin.
4. The method for using the penetration shearing device for foundation in-situ test based on the fiber bragg grating according to claim 1, wherein the cone tip measuring head is sequentially provided with a cone tip, a force transmission column, an elastic metal diaphragm, a cone tip fiber bragg grating strain sensor and a fiber bragg grating temperature sensor from bottom to top; the cone-tip fiber bragg grating strain sensor is tightly attached to the elastic metal diaphragm and is connected with the fiber bragg grating temperature sensor in series through the signal transmission fiber.
5. The method of using a fiber grating-based penetration shear device for foundation in-situ testing according to claim 4, wherein the elastic metal membrane is a round thin plate with constant thickness and fixed around.
6. The method of using a fiber grating based penetration shearing apparatus for foundation in-situ test according to claim 1, wherein the probe rod is single or multiple in series, and the side of the probe rod is provided with a slit, and the signal transmission fiber is just allowed to pass through the slit and is placed in the hollow part of the probe rod.
7. The method of claim 1, wherein the temperature of the multifunctional probe in step (2) is measured by a fiber bragg grating temperature sensor in the cone tip probe and used as a temperature compensation for a fiber bragg grating strain sensor.
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