CN215004642U - Coarse-grained soil shear wave velocity testing device and testing system excited by external vibration source - Google Patents
Coarse-grained soil shear wave velocity testing device and testing system excited by external vibration source Download PDFInfo
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Abstract
A coarse-grained soil shear wave velocity testing device and a testing system based on external vibration source excitation. The external excitation device comprises a sliding unit, a fixing unit, a torsion unit, a limiting block, a hydraulic rod, a push-pull type electromagnet and two laser ranging sensors; the sliding unit and the push-pull electromagnet as well as the fixed unit and the hydraulic rod are respectively fixed through threads; the two laser ranging sensors monitor the working state of the external excitation device and adjust the height of the hydraulic rod in real time. A torsion unit in the test system is connected with a loading shaft of a triaxial test instrument, and two acceleration sensors are arranged on the side surface of a test sample; the push-pull type electromagnet is electrified and then impacts on the torsion unit, the torsion unit generates torsional vibration and transmits the torsional vibration 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 electric signals. The utility model discloses can avoid exciting arrangement in being in the inside high-pressure environment of triaxial apparatus, simple structure is reasonable, convenient operation, has good spreading value in geotechnical engineering and structural health monitoring field.
Description
Technical Field
The utility model relates to a soil mechanics triaxial test device and test method, especially a test device, test system and method that measure coarse-grained soil shear wave velocity's outside vibration source arouses among large-scale triaxial test.
Background
The soil shear wave velocity is one of key mechanical parameters for describing the online elastic strain range of the soil, and has important significance in the aspects of dividing stratum and field soil types, judging the liquefaction of sandy soil, calculating rock-soil dynamic parameters and the like.
At present, a laboratory generally adopts two methods, namely a resonance column method and a bending element method, to carry out shear wave velocity test. The resonance column is high in test cost, the calculation process is complicated, and the biggest problem is that the size of a sample is limited and the test requirement of a large-size sample cannot be met. The bending element method has clear principle and simple method, can be installed in various geotechnical test instruments, but is easy to damage under the action of compaction work when preparing samples. And the resonant column method and the bending element method are mostly used for small-size samples and are widely applied to tests of sandy soil, loess and clay. As typical coarse-grained soil, the gravel material and the blasting material have the advantages of good compactibility, high shear strength and the like, and are widely applied to engineering construction, while the existing wave velocity testing technology is difficult to realize shear wave velocity testing of the gravel material and the blasting material in a large-scale triaxial test. Therefore, a simple and convenient indoor test device and method for testing the shear wave velocity of coarse-grained soil are needed.
SUMMERY OF THE UTILITY MODEL
The problem that exists to prior art, the utility model provides a soil body shear wave speed external excitation test device and method that can be used to large-scale triaxial test appearance rational in infrastructure, assembly are simple, convenient operation.
The utility model provides a technical scheme that prior art problem adopted:
a coarse-grained soil shear wave velocity testing device excited by an external vibration source comprises a push-pull electromagnet 1, a sliding unit 2, a fixing unit 3, a limiting block 5 and a hydraulic rod 8.
The push-pull electromagnet 1 is of a block structure with a bulge; after the power is applied, the protruding portion of the tip portion is released, and an instantaneous impact force is generated.
The sliding unit 2 is of a block structure, and an I-shaped groove structure is arranged below the sliding unit. The upper end of the sliding unit 2 is fixed with the push-pull electromagnet 1 through a threaded hole arranged on the bottom surface, the lower I-shaped groove structure is matched and connected with the I-shaped guide rail of the fixing unit 3, and the sliding unit can freely slide on the guide rail under the condition of no external limitation.
The limiting block 5 is of a block structure and is arranged on one side of the track of the fixing unit 3, and a gasket is arranged at a gap between the limiting block and the I-shaped guide rail to limit the movement of the sliding unit 2 on the fixing unit 3 in the working process of the push-pull electromagnet 1.
The fixing unit 3 comprises an I-shaped guide rail and a columnar structure at the lower end of the guide rail, wherein the columnar structure is provided with two penetrating threaded holes and is fixed with one end, provided with threads, of the bottom of the I-shaped guide rail of the fixing unit 3 through a bolt, and then the fixing unit 3 is connected into a whole.
The hydraulic rod 8 is a telescopic rod, and particularly is of a telescopic columnar structure; the top of the fixing unit is welded at the bottom of the fixing unit 3 and combined into a whole. The hydraulic rod 8 is connected with the hydraulic servo controller 7, and the lifting of the fixing unit 3 can be realized by changing the length of the hydraulic servo controller 7, so that the purpose of adjusting the elevation position of the push-pull type electromagnet 1 is achieved.
A test system for testing the shear wave velocity of coarse-grained soil excited by an external vibration source comprises an external excitation test device, a torsion unit 4, two laser ranging sensors 6, a hydraulic servo controller 7, two acceleration sensors 9, a charge amplifier 12 and an oscilloscope 13.
The torsion unit 4 is formed by combining two plate-shaped structures, and symmetrical semicircular grooves are formed in the opposite sides of the two plate-shaped structures and are used for being sleeved on the loading shaft; one plate-shaped structure is provided with a cantilever, a horizontal threaded blind hole is formed in the plate-shaped structure, a horizontal threaded through hole is formed in the other plate-shaped structure, and the two plate-shaped structures are fixed on a loading shaft of the large triaxial tester through bolts. After the push-pull electromagnet 1 is electrified, the protrusion at the front end of the push-pull electromagnet 1 collides with the cantilever end in the torsion unit 4, and due to the meshing effect between the torsion unit 4 and the loading shaft, the cantilever end can generate the torsion excitation effect on the loading shaft after being hit. Traditional excitation device often is located inside the triaxial test appearance, and excitation device must be in high pressure, in the environment under water, the utility model discloses a structural design makes excitation device be located the triaxial test appearance outside, has avoided excitation device to be in high pressure, in the environment under water, has avoided the cable conductor to need follow the emergence of the condition of drawing forth in the triaxial test appearance pressure chamber when excitation device is located the triaxial test appearance inside simultaneously.
The laser ranging sensor 6 comprises a longitudinal laser ranging sensor and a transverse laser ranging sensor, the two are respectively connected to the upper surface of the large triaxial tester 11 and the side wall of the push-pull electromagnet 1 close to one side of the loading shaft through bolts, wherein the longitudinal laser ranging sensor is arranged at the position of a plumb bob under the torsion unit 4, the test soil sample 10 can deform in the test process to further cause the elevation change of the loading shaft, so that the longitudinal laser ranging sensor can acquire the distance from the longitudinal laser ranging sensor to the bottom surface of the torsion unit 4 in real time, and the hydraulic servo controller 7 is used for controlling the hydraulic rod 8 to move, further the elevation of the push-pull electromagnet 1 is adjusted, and the push-pull electromagnet 1 and the torsion unit 4 are always at the same horizontal height. Because of hitting the different can exert an influence on the result of distance, horizontal laser rangefinder sensor and stopper 5 collaborative work, and then the high accuracy is adjusted the distance of hitting of plug-type electro-magnet 1, still can make horizontal laser rangefinder sensor monitor among the test process the position of slip unit 2, guarantees to hit the effect of hitting.
The two acceleration sensors 9 are arranged on the surface of the test soil sample 10 at intervals and are respectively connected with the charge amplifier 12, the charge amplifier 12 is connected with the oscilloscope 13, and the test soil sample 10 is arranged in the large triaxial tester 11.
The external excitation test device is connected with the upper surface of the large triaxial test instrument 11 through the hydraulic rod 8 in a welding mode, the horizontal distance from the circle center of the hydraulic rod 8 to the circle center of the loading shaft in the external excitation test device is guaranteed to be slightly smaller than the length of the cantilever end, so that larger torque can be generated when the external excitation test device bears the same impact force, and the situation that the torsion unit 4 cannot be knocked by the push-pull electromagnet 1 with too large distance can be avoided. The end part of the protrusion of the push-pull electromagnet 1 strikes the torsion unit 4 after being electrified, so that torque is generated on a loading shaft of a triaxial tester, the torsion unit 4 generates torsional vibration and transmits the torsional vibration through the test soil sample 10, the acceleration sensor 9 collects vibration signals at different elevation measuring points of the test soil sample 10 and converts the vibration signals into electric signals, and the electric signals are simultaneously displayed and stored on the oscilloscope 13 after passing through the charge amplifier 12 to provide data for the calculation of the propagation time of shear waves. Further, the two acceleration sensors 9 are respectively installed at different elevations on the side surface of the sample along the vertical direction.
Further, the test soil sample 10 is a cylindrical large triaxial sample prepared according to a preset density.
An external excitation test method for measuring the shear wave velocity of coarse-grained soil in a large triaxial test comprises the following steps:
s1, system installation: preparing a coarse-grained soil test soil sample 10 in a large triaxial tester 12, and respectively installing two acceleration sensors 9 at different elevations on the side surface of the test soil sample 10 along the vertical direction; adjusting the striking distance of an external excitation test device by using a transverse laser ranging sensor, solidifying under equidirectional confining pressure, and adjusting the elevation of the solidified push-pull electromagnet 1 by using a hydraulic servo controller 7 according to the real-time data of the longitudinal laser ranging sensor;
s2, determining the propagation time of the shear wave: after the external excitation test device is adjusted, the push-pull electromagnet 1 is electrified, after the push-pull electromagnet 1 strikes the torsion unit 4, the torsion unit 4 generates torsional vibration under the action of inertia force, and the torsional vibration is transmitted through the test soil sample 10; reading vibration data acquired by an acceleration sensor on a sample through an oscilloscope 13, and calculating by adopting a characteristic point method or a cross-correlation method to obtain the propagation time delta t of the shear wave;
s3, shear wave velocity calculation: the shear wave speed of the test soil sample is L/delta t, wherein L is the vertical distance between the two acceleration sensors.
The beneficial effects of the utility model reside in that: the utility model discloses a test device structural style is simple, and the soil body disturbance that arouses when having avoided crooked unit embedding test soil sample utilizes plug-type electro-magnet to strike and replaces traditional piezoelectric material to arouse, enables that the magnitude of voltage that obtains on the oscilloscope is bigger, arouses the effect better. In addition, the device is directly fixed outside the sample, so that the trouble that a cable of the excitation device needs to be led out from the pressure chamber is avoided, and the problems of possible aging, easy damage and the like of the cable under the action of high confining pressure for a long time are also avoided. Meanwhile, the external excitation device can be arranged on triaxial test instruments with different sizes, has strong transportability and greatly facilitates the experimental research on the soil body small-strain dynamic characteristic scale effect.
Drawings
Fig. 1 is a schematic view of the overall structure of the external excitation device of the present invention.
Fig. 2 is a schematic view of the connection structure between the external excitation device and the triaxial apparatus according to the present invention.
Fig. 3 is a schematic diagram of a connection structure of the testing system of the present invention.
Fig. 4 is a diagram of a typical test waveform.
In the figure: the device comprises a push-pull electromagnet 1, a sliding unit 2, a fixing unit 3, a torsion unit 4, a limiting block 5, a laser ranging sensor 6, a hydraulic servo controller 7, a hydraulic rod 8, an acceleration sensor 9, a soil sample 10, a large triaxial tester 11, a charge amplifier 12 and an oscilloscope 13.
Detailed Description
The present invention is described below with reference to the accompanying drawings and the embodiments:
fig. 1 is a schematic view of the overall structure of the external excitation device of the present invention. The external excitation test device for measuring the shear wave velocity of coarse-grained soil in a large triaxial test sequentially comprises a push-pull electromagnet 1, a sliding unit 2, a fixing unit 3, a limiting block 5 and a hydraulic rod 8; as shown in fig. 2, the torsion unit 4 is composed of a columnar structure with a cantilever and two threaded blind holes and a columnar structure without a cantilever and with two threaded through holes, and the two are fixed on a loading shaft of a large triaxial tester by bolts, and then the two parts of the torsion unit 4 are connected into a whole by the two bolts and are tightly connected with a transmission shaft of the triaxial tester. Due to the structural design, the excitation device is positioned outside the sample, the size of the torsion unit 4 can be theoretically changed and then the torsion unit can be used for triaxial testers of various sizes, and the problems that the excitation device is directly contacted with the test soil sample 10 and a cable of the excitation device needs to be led out from a pressure chamber of the triaxial tester are avoided.
A coarse-grained soil shear wave velocity test system excited by an external vibration source, as shown in fig. 3, comprising an external excitation test device shown in fig. 1-3, an acceleration sensor 9, a charge amplifier 12 and an oscilloscope 13; the two acceleration sensors 9 are respectively connected with a charge amplifier 12, and the charge amplifier 12 is connected with an oscilloscope 13. The push-pull electromagnet 1 in the external excitation test device generates pulses as excitation signals after being electrified, strikes the torsion unit 4 and enables the loading shaft of the large triaxial apparatus 11 to generate torsional vibration. Under the action of the pulse of the push-pull electromagnet 1, the generated torsional vibration is transmitted through the test soil sample, the acceleration sensor 9 is used for collecting vibration signals at different elevation measuring points of the test soil sample 10 and converting the vibration signals into electric signals, and the electric signals are simultaneously displayed and stored on the oscilloscope 13 after passing through the charge amplifier 12 so as to provide data for the calculation of the transmission 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 samples 10 were prepared according to the general test method of soil engineering test protocol (SL 237-1999). Two acceleration sensors 9 in an external excitation test system are respectively fixed at different elevations of rubber membranes on the side surface of a test soil sample 10 along the vertical direction; and adjusting the striking distance of the external excitation test device by using a transverse laser ranging sensor, solidifying under equidirectional confining pressure, and adjusting the elevation of the solidified push-pull electromagnet 1 by using a hydraulic servo controller 7 according to the real-time data of the longitudinal laser ranging sensor.
S2, determining the propagation time of the shear wave: after the external excitation test device is adjusted, the push-pull electromagnet 1 is electrified, after the push-pull electromagnet 1 strikes the torsion unit 4, the torsion unit 4 generates torsional vibration under the action of inertia force, and the torsional vibration is transmitted through the test soil sample 10; the acceleration sensors 9 at different elevations on the side surface of the test soil sample 10 acquire 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; reading vibration data acquired by the acceleration sensor 9 through an oscilloscope 12, and calculating by adopting a characteristic point method or a cross-correlation method to obtain the propagation time delta t of the shear wave;
s3, shear wave velocity calculation: the shear wave speed of the test soil sample 10 is L/delta t, wherein L is the vertical distance between the two acceleration sensors 9.
The foregoing is a more detailed description of the present invention, taken in conjunction with the specific preferred embodiments thereof, and it is not intended that the invention be limited to the specific embodiments shown and described. To the utility model belongs to the technical field of ordinary technical personnel, do not deviate from the utility model discloses under the prerequisite of design, can also make a plurality of simple deductions or replacement, all should regard as belonging to the utility model discloses a protection scope.
Claims (5)
1. A coarse-grained soil shear wave velocity testing device excited by an external vibration source is characterized by comprising a push-pull electromagnet (1), a sliding unit (2), a fixing unit (3), a limiting block (5) and a hydraulic rod (8);
the push-pull electromagnet (1) is of a block structure with a bulge, and after the push-pull electromagnet is electrified, the bulge at the front end part of the push-pull electromagnet is released to generate instant impact force;
the sliding unit (2) is of a block structure, and an I-shaped groove structure is arranged below the sliding unit; the top surface of the sliding unit is fixedly connected with the bottom surface of the push-pull electromagnet (1), and an I-shaped groove structure of the sliding unit (2) is matched and connected with an I-shaped guide rail of the fixed unit (3) and can freely slide on the guide rail;
the limiting block (5) is of a block structure, is arranged on one side of the track of the fixed unit (3) and is used for limiting the movement of the sliding unit (2) on the fixed unit (3) in the working process of the push-pull electromagnet (1);
the fixing unit (3) comprises an I-shaped guide rail and a plate-shaped structure at the lower end of the guide rail, wherein the plate-shaped structure is provided with two penetrating threaded holes and is used for being fixed with the bottom of the I-shaped guide rail through bolts to connect the fixing unit (3) into a whole;
the hydraulic rod (8) is a telescopic rod, and the top of the hydraulic rod is welded at the bottom of the fixing unit (3); the hydraulic rod (8) is connected with the hydraulic servo controller (7), and the lifting of the fixing unit (3) can be realized by changing the length of the hydraulic servo controller (7), so that the purpose of adjusting the elevation position of the push-pull electromagnet (1) is achieved.
2. The device for testing the shear wave velocity of the coarse-grained soil excited by the external vibration source according to claim 1, wherein a gasket is arranged at a gap between the limiting block (5) and the I-shaped guide rail of the fixing unit (3).
3. A test system assembled by a coarse-grained soil shear wave velocity test device excited by an external vibration source is characterized by comprising the coarse-grained soil shear wave velocity test device excited by the external vibration source according to claim 1, a torsion unit (4), two laser ranging sensors (6), a hydraulic servo controller (7), two acceleration sensors (9), a charge amplifier (12) and an oscilloscope (13);
the torsion unit (4) is formed by combining two plate-shaped structures, and symmetrical semicircular grooves are formed in the opposite sides of the two plate-shaped structures and are used for being sleeved on the loading shaft; one of the plate-shaped structures is provided with a cantilever, the two plate-shaped structures are fixed on a loading shaft of the large triaxial tester through bolts, and after the two plate-shaped structures are installed, the cantilever is positioned above the fixing unit (3) and is positioned on the same horizontal plane with a convex part at the front end part of the push-pull electromagnet (1);
the laser ranging sensor (6) comprises a longitudinal laser ranging sensor and a transverse laser ranging sensor which are fixed on the upper surface of the large triaxial tester (11) and the side wall of one side, close to the loading shaft, of the push-pull electromagnet (1), wherein the longitudinal laser ranging sensor is arranged at the position of a plumb bob right below a cantilever of the torsion unit (4); the transverse laser ranging sensor and the limiting block (5) work cooperatively, so that the hitting distance of the push-pull type electromagnet (1) is adjusted at high precision, and the transverse laser ranging sensor can monitor the position of the sliding unit (2) in the test process, so that the hitting effect is ensured;
the two acceleration sensors (9) are arranged on the surface of the test soil sample (10) at intervals and are respectively connected with the charge amplifier (12), the charge amplifier (12) is connected with the oscilloscope (13), and the test soil sample (10) is arranged in the large triaxial tester (11);
the coarse-grained soil shear wave velocity testing device excited by the external vibration source is arranged on the upper surface of the large triaxial tester (11) through a hydraulic rod (8); the horizontal distance from the circle center of the hydraulic rod (8) to the circle center of the loading shaft is less than the length of the cantilever end;
after the push-pull electromagnet (1) is electrified, the protrusion at the front end of the push-pull electromagnet is released to pop out and collide with the cantilever end in the torsion unit (4), and the cantilever end generates torsion excitation on the loading shaft after being struck; the torsion unit (4) generates torsion vibration and transmits the torsion vibration through the test soil sample (10), the acceleration sensor (9) collects vibration signals at different height measuring points of the test soil sample (10) and converts the vibration signals into electric signals, and the electric signals are simultaneously displayed and stored on the oscilloscope (13) after passing through the charge amplifier (12) so as to provide data for the calculation of the transmission time of the shear wave.
4. Testing system according to claim 3, characterized in that the two acceleration sensors (9) are mounted at different elevations on the side of the test specimen in the vertical direction.
5. The testing system according to claim 3, characterized in that the test soil sample (10) is a cylindrical large triaxial sample prepared according to a predetermined density.
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| CN113029755A (en) * | 2021-03-29 | 2021-06-25 | 大连理工大学 | Coarse-grained soil shear wave velocity testing device, testing system and method based on external vibration source excitation |
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