CN112649287B - External excitation test device, test system and method for measuring soil shear wave velocity in large triaxial test - Google Patents
External excitation test device, test system and method for measuring soil shear wave velocity in large triaxial test Download PDFInfo
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- CN112649287B CN112649287B CN202110059555.3A CN202110059555A CN112649287B CN 112649287 B CN112649287 B CN 112649287B CN 202110059555 A CN202110059555 A CN 202110059555A CN 112649287 B CN112649287 B CN 112649287B
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- 238000012360 testing method Methods 0.000 title claims abstract description 86
- 239000002689 soil Substances 0.000 title claims abstract description 59
- 230000005284 excitation Effects 0.000 title claims abstract description 37
- 238000000034 method Methods 0.000 title claims abstract description 17
- 230000001133 acceleration Effects 0.000 claims abstract description 23
- 238000010998 test method Methods 0.000 claims description 7
- 230000000694 effects Effects 0.000 claims description 3
- 239000003822 epoxy resin Substances 0.000 claims description 3
- 238000009434 installation Methods 0.000 claims description 3
- 229920000647 polyepoxide Polymers 0.000 claims description 3
- 230000000149 penetrating effect Effects 0.000 claims description 2
- 238000012544 monitoring process Methods 0.000 abstract 1
- 239000000463 material Substances 0.000 description 5
- 238000005452 bending Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 238000005422 blasting Methods 0.000 description 2
- 239000004576 sand Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000004927 clay Substances 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000011545 laboratory measurement Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000010008 shearing Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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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
- G01N3/02—Details
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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
- G01N3/02—Details
- G01N3/06—Special adaptations of indicating or recording means
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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
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- Immunology (AREA)
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- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
- Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)
- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
Abstract
An external excitation test device, a test system and a method for measuring soil shear wave velocity in a large triaxial test. The external excitation device comprises four piezoelectric stacks, four inertia blocks and a vibration unit; the end part of the inertia block is respectively connected with the end face of the piezoelectric stack and is fixed with the fixing unit through threads; the vibration unit includes a middle cylinder fixing unit and four torsion units uniformly disposed along the outer circumference thereof. The fixed unit in the test system is connected with a loading shaft of the triaxial tester, and two acceleration sensors are arranged on the side surface of the sample; the signal generating device generates voltage pulses to act on the piezoelectric stack, the vibration unit generates torsional vibration under the longitudinal vibration action of the piezoelectric stack, the torsional vibration is transmitted through the sample, the sensor collects vibration signals transmitted to different positions of the sample and converts the vibration signals into electric signals, and the shear wave speed of the soil body is calculated through the time difference of the collected electric signals. The invention has simple and reasonable structure, simple assembly and convenient operation, and has good popularization value in the field of geotechnical engineering and structural health monitoring.
Description
Technical Field
The invention relates to a triaxial test device and a triaxial test method for soil mechanics, in particular to an external excitation test device, a test system and a test method for measuring shear wave velocity of coarse-grained soil in a large triaxial test.
Background
The shear wave velocity of the soil body is one of key mechanical parameters in the elastic strain range of the soil body, and has important significance in the aspects of dividing stratum and field soil types, judging liquefaction of sand and soil, earthquake subsidence and settlement of soil base, analyzing earthquake reaction, calculating rock-soil kinetic parameters and the like.
Laboratory measurements of shear wave velocity of soil mass typically employ resonant column and bending element methods. The resonance column test is high in price, the calculation process is complex, and the size of the sample is limited. The bending element method has clear principle and simple method, and can be simultaneously installed in various geotechnical test instruments. However, the resonant column method and the bending element method are used for small-sized samples, and are widely used in sand and sand-clay mixtures. As typical coarse-grained soil, the gravel material and the blasting material have the advantages of good compactibility, high shear strength, strong water permeability and the like, are widely applied to engineering construction, and the shearing wave speed test of the gravel material and the blasting material is difficult to realize in a large triaxial test by the existing wave speed test technology. Therefore, a simple and convenient indoor test device and method for testing the shear wave velocity of coarse-grained soil are needed.
Disclosure of Invention
Aiming at the problems existing in the prior art, the invention provides the soil shear wave speed external excitation test device and the soil shear wave speed external excitation test method which can be used for a large triaxial tester and are reasonable in structure, simple to assemble and convenient to operate.
The invention solves the problems in the prior art by adopting the technical scheme that:
An external excitation test device for measuring shear wave velocity of soil in a large triaxial test comprises four piezoelectric stacks 1, four inertia blocks 2 and a vibration unit 3.
The piezoelectric stack 1 has a bulk structure.
The inertial block 2 is of a cylindrical structure, one end of the inertial block is fixed on one end face of the piezoelectric stack 1, and the outer surface of the other end of the inertial block is provided with threads.
The vibration unit 3 comprises a fixing unit 4 with a middle cylinder structure and four torsion units 5 uniformly arranged along the circumference of the cylinder, wherein the torsion units 5 are of plate-shaped structures. The fixing unit 4 is of a hollow cylinder structure, threads are arranged in the fixing unit, a penetrating threaded hole is formed in the middle of the torsion unit 5, one end, provided with the threads, of the inertia block 2 is fixed through the threads, and the piezoelectric stack 1, the inertia block 2 and the vibration unit 3 are connected into a whole. The fixing unit 4 of the vibration unit 3 is in threaded connection with a loading shaft (external threads) of the large triaxial tester. The structure design ensures that the excitation device is positioned outside the sample, can be theoretically used for triaxial testers with various sizes, and avoids the problems that the piezoelectric stack 1 is directly contacted with the test soil sample 7 and cables of the piezoelectric stack are required to be led out from a pressure chamber of the triaxial tester.
Further, the inertial mass 2 is fixed to the piezoelectric stack 1 by epoxy resin.
A test system for measuring soil shear wave velocity in a large triaxial test is shown in fig. 4, and comprises an external excitation test device, two acceleration sensors 6, a signal generator 9, a power amplifier 10, a charge amplifier 11 and an oscilloscope 12.
The signal generator 9 is connected with the power amplifier 10, and the piezoelectric stack 1 in the external excitation test device is connected with the power amplifier 10. The signal generator 9 is used for generating a voltage pulse as an excitation signal, and the voltage pulse is used for generating longitudinal vibration of the piezoelectric stack 1 after passing through the power amplifier 10. The two acceleration sensors 6 are arranged on the surface of the test soil sample 7 at intervals and are respectively connected with the charge amplifier 11, the charge amplifier 11 is connected with the oscilloscope 12, and the test soil sample 7 is arranged in the triaxial tester.
Under the simultaneous action of the four piezoelectric stacks 1, the vibration unit 3 generates torsional vibration and propagates through the test soil sample 7, the acceleration sensor 6 collects vibration signals at different heights Cheng Cedian of the test soil sample 7 and converts the vibration signals into electric signals, and the electric signals are displayed and stored on the oscilloscope 12 at the same time after passing through the charge amplifier 11 to provide data for calculating the propagation time of the shear wave.
Further, the two acceleration sensors 6 are respectively installed at different heights of the side surface of the sample along the vertical direction.
Further, the test soil sample 7 is a cylindrical large triaxial sample prepared according to a preset density.
An external excitation test method for measuring shear wave velocity of coarse-grained soil in a large triaxial test comprises the following steps:
S1, system installation: preparing coarse-grained soil samples in a large triaxial tester 8, and respectively installing two acceleration sensors 6 at different heights on the side surfaces of the samples along the vertical direction; fixing an external excitation test device on a loading shaft of a triaxial tester through threads, and solidifying under isotropic confining pressure;
S2, determining the propagation time of the shear wave: the starting signal generator 9 generates voltage pulses as excitation signals, the voltage pulses are input into the four piezoelectric stacks 1 at the same time after passing through the power amplifier 10, the four piezoelectric stacks 1 generate longitudinal vibration at the same time due to the inverse piezoelectric effect, the vibration unit 3 generates torsional vibration under the action of the inertia force of the piezoelectric stacks 1, and the torsional vibration is transmitted through the sample 7; the oscillograph 12 is used for reading vibration data acquired by an acceleration sensor on a sample, and a characteristic point method or a cross correlation method is adopted to calculate and obtain the propagation time delta t of the shear wave;
s3, calculating shear wave speed: the shear wave velocity of the test soil sample is L/Deltat, wherein L is the vertical distance between two acceleration sensors.
The invention has the beneficial effects that: the test device has simple structure, avoids disturbance caused by embedding the bending element into the test soil sample, and solves the problem that the piezoelectric material is easy to damage in the process of sample preparation compaction and high-stress condition loading of a large-scale triaxial test. In addition, the device is directly fixed outside the sample, so that the trouble that the cable of the piezoelectric stack needs to be led out of the pressure chamber is avoided, and meanwhile, the problems that the cable is likely to be aged and damaged under the action of high confining pressure for a long time are also avoided. Meanwhile, the external excitation device can be installed on triaxial testers with different sizes, has strong portability, and is greatly convenient for experimental study on the small-strain dynamic characteristic scaling effect of soil.
Drawings
Fig. 1 is a schematic view of the overall structure of an external excitation device according to the present invention.
Fig. 2 is a schematic diagram of the structure of the piezoelectric stack and the inertial mass in the external excitation device of the present invention.
Fig. 3 is a schematic structural view of a vibration unit in the external excitation device of the present invention.
FIG. 4 is a schematic diagram of the connection structure of the test system of the present invention.
Fig. 5 is a typical test waveform diagram.
In the figure: the device comprises a piezoelectric stack 1, an inertial block 2, a vibration unit 3, a fixing unit 4, a torsion unit 5, an acceleration sensor 6, a test soil sample 7, a triaxial tester 8, a signal generator 9, a power amplifier 10, a charge amplifier 11 and an oscilloscope 12.
Detailed Description
The invention is described below with reference to the drawings and the detailed description:
FIG. 1 is a schematic view showing the overall structure of an external excitation test apparatus for measuring shear wave velocity of coarse-grained soil according to the invention. The external excitation test device for measuring the shear wave velocity of coarse-grained soil in the large triaxial test sequentially comprises a piezoelectric stack 1, an inertial block 2 and a vibration unit 3; as shown in fig. 2, one end of the piezoelectric stack 1 and one end of the inertial mass 2 are fixed into a whole through epoxy resin, and the outer surface of the other end of the inertial mass 2 is provided with threads; as shown in fig. 3, the vibration unit 3 is divided into a fixing unit 4 and a torsion unit 5, wherein threads are arranged in the fixing unit 4, a threaded hole is formed in the surface of the torsion unit 5, and the torsion unit is fixed with one end of the inertia block 2, which is provided with the threads, so that the piezoelectric stack 1, the inertia block 2 and the vibration unit 3 are connected into a whole; as shown in fig. 4, the whole of the piezoelectric stack 1, the inertial mass 2, and the vibration unit 3 is connected to a loading shaft (external screw) of the triaxial tester 8. The structure design ensures that the excitation device is positioned outside the sample, can be theoretically used for triaxial testers with various sizes, and avoids the trouble that the piezoelectric stack 1 is directly contacted with the test soil sample 7 and the cable of the piezoelectric stack needs to be led out from the pressure chamber of the triaxial tester.
The test system for measuring the shear wave velocity of coarse-grained soil in the large triaxial test is shown in fig. 4, and comprises an external excitation test device, an acceleration sensor 6, a signal generator 9, a power amplifier 10, a charge amplifier 11 and an oscilloscope 12 shown in fig. 1-3; the signal generator 9 is connected with the power amplifier 10, and the piezoelectric stack 1 in the external excitation test device is connected with the power amplifier 10; the two acceleration sensors 6 are respectively connected with a charge amplifier 11, and the charge amplifier 11 is connected with an oscilloscope 12. The signal generator 9 is used for generating a voltage pulse as an excitation signal, and the voltage pulse is used for generating longitudinal vibration of the piezoelectric stack 1 after passing through the power amplifier 10. Under the simultaneous action of the four piezoelectric stacks, the vibration unit generates torsional vibration and propagates through the test soil sample, and the acceleration sensor 6 is used for collecting vibration signals at different heights Cheng Cedian of the test soil sample 7 and converting the vibration signals into electric signals, and the electric signals are simultaneously displayed and stored on the oscilloscope 12 after passing through the charge amplifier 11 to provide data for calculating the propagation time of the shear wave.
The test method of the test system for measuring the shear wave velocity of coarse-grained soil in the large triaxial test comprises the following steps:
S1, system installation: test soil sample 7 was prepared according to the conventional test method in geotechnical test protocol (SL 237-1999). The lower part of a vibration unit 3 in an external excitation test device is connected with an axial loading shaft of a triaxial tester 8, and two acceleration sensors 6 in the external excitation test system are respectively fixed at different heights of rubber films on the side surface of a test soil sample 7 along the vertical direction; and consolidated under an isotropic confining pressure.
S2, determining the propagation time of the shear wave: the starting signal generator 9 generates voltage pulse as excitation signal, the piezoelectric stack 1 simultaneously generates longitudinal vibration after passing through the power amplifier 10, the vibration unit 3 generates torsional vibration under the action of inertia force, the vibration propagates through the test soil sample 7 in the form of torsional wave, the acceleration sensors 6 at different heights on the side surface of the test soil sample 7 collect vibration signals and convert the vibration signals into electric signals, and the electric signals are simultaneously displayed and stored on the oscilloscope 12 after passing through the charge amplifier 11; the oscillograph 12 is used for reading vibration data acquired by the acceleration sensor 6, and a characteristic point method or a cross correlation method is adopted for calculating the propagation time delta t of the shear wave;
S3, calculating shear wave speed: the shear wave velocity of the test soil sample 8 is L/Δt, where L is the vertical distance of the two acceleration sensors 6.
The above is a further detailed description of the invention in connection with specific preferred embodiments, and it is not to be construed as limiting the practice of the invention to these descriptions. It will be apparent to those skilled in the art that several simple deductions or substitutions may be made without departing from the spirit of the invention, and these should be considered to be within the scope of the invention.
Claims (5)
1. The external excitation test device for measuring the shear wave velocity of the soil body in the large triaxial test is characterized by comprising four piezoelectric stacks (1), four inertia blocks (2) and a vibration unit (3);
The piezoelectric stack (1) is of a block structure;
the inertial block (2) is of a cylindrical structure, one end of the inertial block is fixed on one end face of the piezoelectric stack (1), and the outer surface of the other end of the inertial block is provided with threads;
The vibration unit (3) comprises a fixing unit (4) with a middle cylinder structure and four torsion units (5) which are uniformly arranged along the circumferential direction of the outer periphery of the cylinder, wherein the torsion units (5) are of a plate-shaped structure; the fixing unit (4) is of a hollow cylinder structure, threads are arranged in the fixing unit, a penetrating threaded hole is formed in the middle of the torsion unit (5), and the fixing unit is fixed with one end of the inertia block (2) with threads through threads, so that the piezoelectric stack (1), the inertia block (2) and the vibration unit (3) are connected into a whole; the fixing unit (4) of the vibration unit (3) is connected with the loading shaft of the large triaxial tester through threads.
2. The external excitation test device for measuring the shear wave velocity of soil in a large triaxial test according to claim 1, characterized in that the inertial mass (2) is fixed with the piezoelectric stack (1) as a whole by epoxy resin.
3. A test system for measuring the soil shear wave speed by adopting the external excitation test device for measuring the soil shear wave speed in the large triaxial test according to claim 1 or2, which is characterized by comprising the external excitation test device, two acceleration sensors (6), a signal generator (9), a power amplifier (10), a charge amplifier (11) and an oscilloscope (12);
The signal generator (9) is connected with the power amplifier (10), and the piezoelectric stack (1) in the external excitation test device is connected with the power amplifier (10); the signal generator (9) is used for generating voltage pulses as excitation signals, and the piezoelectric stack (1) generates longitudinal vibration after passing through the power amplifier (10); the two acceleration sensors (6) are arranged on the surface of the test soil sample (7) at intervals and are respectively connected with the charge amplifier (11), the charge amplifier (11) is connected with the oscilloscope (12), and the test soil sample (7) is arranged in the large triaxial tester (8);
The fixed unit (4) of the vibration unit (3) is connected with the loading shaft of the large triaxial tester through threads; under the simultaneous action of the four piezoelectric stacks (1), the vibration unit (3) generates torsional vibration and propagates through the test soil sample (7), the acceleration sensor (6) collects vibration signals at different heights Cheng Cedian of the test soil sample (7) and converts the vibration signals into electric signals, and the electric signals are displayed and stored on the oscilloscope (12) at the same time after passing through the charge amplifier (11) to provide data for calculating the propagation time of the shear wave.
4. A test system for measuring shear wave velocity of soil mass in a large triaxial test according to claim 3, characterized in that the two acceleration sensors (6) are respectively installed at different heights of the side surface of the test specimen in the vertical direction.
5. An external excitation test method for measuring the shear wave velocity of coarse-grained soil in a large triaxial test using the test system for measuring the shear wave velocity of soil according to claim 3 or 4, comprising the steps of:
S1, system installation: preparing a coarse-grained soil test soil sample (7) in a large triaxial tester (8), and respectively installing two acceleration sensors (6) at different heights on the side surface of the test soil sample (7) along the vertical direction; fixing an external excitation test device on a loading shaft of a triaxial tester through threads, and solidifying under isotropic confining pressure;
S2, determining the propagation time of the shear wave: the starting signal generator (9) generates voltage pulses as excitation signals, the voltage pulses are input into the four piezoelectric stacks (1) at the same time after passing through the power amplifier (10), the four piezoelectric stacks (1) generate longitudinal vibration at the same time due to the inverse piezoelectric effect, and the vibration unit (3) generates torsional vibration under the action of the inertia force of the piezoelectric stacks (1) and propagates through the test soil sample (7); reading vibration data acquired by an acceleration sensor on a sample through an oscilloscope (12), and calculating to obtain propagation time delta t of the shear wave by adopting a characteristic point method or a cross-correlation method;
s3, calculating shear wave speed: the shear wave velocity of the test soil sample is L/Deltat, wherein L is the vertical distance between two acceleration sensors.
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| CN108663265A (en) * | 2018-07-12 | 2018-10-16 | 大连理工大学 | Measure combined type torsion shear apparatus, the system and method for soil body shear wave velocity |
| CN214309853U (en) * | 2021-01-18 | 2021-09-28 | 大连理工大学 | External excitation test device and test system for measuring soil shear wave velocity in large-scale triaxial test |
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| WO2003095949A1 (en) * | 2002-05-08 | 2003-11-20 | Endress + Hauser Flowtec Ag | Torsional oscillation damper for a vibrating measuring transformer |
| US6813960B1 (en) * | 2002-08-19 | 2004-11-09 | Southwest Research Institute | Asymmetrical column assembly for high-cycle fatigue test machines |
| JP4177281B2 (en) * | 2004-03-29 | 2008-11-05 | 関西電力株式会社 | Measuring apparatus and measuring method |
| JP2006047229A (en) * | 2004-08-06 | 2006-02-16 | River Eletec Kk | Surface acoustic wave device sensor |
| US7681450B2 (en) * | 2005-12-09 | 2010-03-23 | Baker Hughes Incorporated | Casing resonant radial flexural modes in cement bond evaluation |
| EP2316018B1 (en) * | 2008-04-10 | 2017-10-18 | Brookhaven Science Associates LLC. | Nondestructive testing apparatus and method |
| CN101476970B (en) * | 2009-01-14 | 2010-09-29 | 大连理工大学 | A base excitation device for MEMS dynamic characteristic test |
| CN102621025A (en) * | 2012-03-12 | 2012-08-01 | 山东科技大学 | Thin film bulk acoustic resonance biochemical sensor with annular electrodes |
| DE102014103299B4 (en) * | 2014-03-12 | 2021-07-22 | Spektra Schwingungstechnik Und Akustik Gmbh Dresden | Vibration exciter with load compensation |
| CN105388219B (en) * | 2015-10-26 | 2017-12-22 | 东南大学 | Test the piezoelectric ring excitation apparatus and laboratory testing rig of bulk material shear wave velocity |
| CN108445077B (en) * | 2018-01-29 | 2022-10-14 | 天津大学 | Optical elasticity test method |
| CN208350200U (en) * | 2018-03-21 | 2019-01-08 | 大连理工大学 | A kind of experimental rig and system measuring coarse-grained soil shear wave velocity |
| CN108398180B (en) * | 2018-03-21 | 2023-04-18 | 大连理工大学 | Test device, system and test method for measuring shear wave velocity of coarse-grained soil |
| CN112054717B (en) * | 2020-09-09 | 2021-09-24 | 中南大学 | Piezoelectric energy harvesting device and application and method on floating plate track |
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| CN108663265A (en) * | 2018-07-12 | 2018-10-16 | 大连理工大学 | Measure combined type torsion shear apparatus, the system and method for soil body shear wave velocity |
| CN214309853U (en) * | 2021-01-18 | 2021-09-28 | 大连理工大学 | External excitation test device and test system for measuring soil shear wave velocity in large-scale triaxial test |
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