CN113075027B - Test device and method for measuring dynamic elastic modulus of soil body model - Google Patents
Test device and method for measuring dynamic elastic modulus of soil body model Download PDFInfo
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Abstract
The invention discloses a test device and a method for measuring dynamic elastic modulus of a soil mass model. Placing the compacted soil model in an explosion model box, detonating the explosive, and recording the change data of the transverse wave velocity and the longitudinal wave velocity of the explosion wave; and obtaining the dynamic elastic modulus of the soil body model by reverse thrust. According to the test device and method for measuring the dynamic elastic modulus of the soil mass model, the dynamic shear modulus and the dynamic elastic modulus of the soil mass dynamic elastic modulus are measured simultaneously by the method of measuring the wave velocity by explosion under the centrifugal condition and reversely pushing the deformation modulus of the soil mass model, the deformation modulus value reversely pushed by the technical method is higher in accuracy, the established relation between the modulus and the hammering number is convenient for model test research, and technical support can be better provided for engineering design parameters.
Description
Technical Field
The invention belongs to the technical field of civil engineering, and relates to a test device and a method for measuring dynamic elastic modulus of a soil mass model.
Background
The dynamic elastic modulus is an important parameter of soil dynamic characteristics, is a necessary dynamic parameter in soil layer and foundation seismic reaction analysis, and is an essential parameter in seismic small-region analysis. Therefore, the method for measuring the dynamic elastic modulus of the soil body, in particular to the method for accurately measuring the dynamic elastic modulus of the soil body, is very critical. At present, methods for measuring the dynamic elastic modulus of soil bodies comprise a field test method and an indoor test method. The field test method has high requirements on test fields and environmental conditions, and has the defects of time and labor waste, harsh test conditions, high cost and the like.
The indoor test method includes a static method and a dynamic method. The static method has simple requirements on measuring equipment, and the laboratory is more common in measuring the elasticity modulus of the soil body. However, the static method is a method having destructive properties to the sample and does not have the opportunity to repeat the test. The static method generally adopts an indoor triaxial apparatus to carry out a triaxial compression test or an unconfined compressor to carry out a uniaxial compression test, has the advantages of large loading, slow loading speed, easy creep deformation, low elastic modulus of a measured soil body, high relative error rate and capability of reaching 5 percent of relative error rate. The dynamic method is used for testing the elastic modulus, the size and weight range of the tested sample are wider than those of the static method, and the dynamic method has no destructive property on the tested sample and belongs to nondestructive testing. The dynamic method generally adopts an ultrasonic method, obtains longitudinal and transverse propagation speeds by measuring the propagation time of ultrasonic waves in a sample and the length of the sample, and obtains the value of the dynamic elastic modulus of the soil body. The stress value generated in the soil sample is only about 0.001Mpa, and the elastic modulus is measured on a stress-strain curve when the stress is close to zero. And the soil sample after the determination is complete and lossless, and the determination can be repeatedly carried out on the same soil sample. However, although the dynamic method has high measurement accuracy, it is generally used for measuring the dynamic elastic modulus of materials such as metals and ceramics, and the measured modulus value is relatively close to reality because the state of a sample body of these materials is not greatly different from that of an actual body. The indoor method is not generally used for measuring the dynamic elastic modulus of the foundation soil, and when the foundation measurement area is large, the difference between the self-weight stress loss after the foundation soil is sampled and the actual foundation state is overlarge, so that the self-weight stress loss caused by the soil sample scaling can be caused, the stress state of the soil sample is not consistent with the actual foundation stress state, and the problem of the reduction of the accuracy of the measurement value of the dynamic elastic modulus of the soil is caused.
Therefore, in order to solve the problem of the soil dynamic elastic modulus test by the indoor test method, it is necessary to provide a novel method capable of accurately measuring the dynamic elastic modulus of the soil model under indoor conditions, so as to solve the problem of the self-weight stress loss caused by the soil sample scale reduction in the indoor test method, and thus improve the measurement accuracy of the soil dynamic elastic modulus.
Disclosure of Invention
In order to achieve the aim, the invention provides a test device and a method for measuring the dynamic elastic modulus of a soil mass model, which are a method for reversely pushing the deformation modulus of the soil mass model by the explosion wave velocity under the centrifugal condition, and the dynamic shear modulus and the dynamic elastic modulus of the soil mass are simultaneously measured by utilizing the transverse and longitudinal waves generated during explosion; the method solves the problems of dead weight stress loss caused by soil sample scale reduction in an indoor testing method and the problem that a laboratory soil model dynamic modulus value measuring method in the prior art is insufficient.
The technical scheme adopted by the invention is that the test device for measuring the dynamic elastic modulus of the soil body model comprises a geotechnical centrifuge, wherein the geotechnical centrifuge is used for providing high-speed rotation for a test and comprises a rotating arm, the center position of the rotating arm is fixed on a rotating table, the rotating table drives the rotating arm to rotate, a measurement and control system is arranged at the center of the rotating arm, two ends of the rotating arm are respectively provided with a weight box and a centrifuge case which are oppositely arranged, the weight boxes are used for carrying out weight balancing on the centrifuge case with the same mass, and an explosion model case is arranged in the centrifuge case and is used for providing an explosion space;
the explosion model box is a circular cylinder, the inner wall of the explosion model box is provided with a polystyrene plate, the thickness of the polystyrene plate is 3 cm-10 cm, the inner bottom of the explosion model box is provided with a sand layer, the thickness of the sand layer is 20 cm-50 cm, the top center position of the sand layer is provided with an explosive which is used as an explosion source, an initiator inside the explosive is in signal connection with a measurement and control system, the top edge of the sand layer is provided with a soil body model, one side of the soil body model far away from the explosive is fixedly attached to the inner wall of the explosion model box, a circle taking the distance between the explosive and the soil body model as a radius is provided with a wave speed tester, the distance between the wave speed tester and the soil body model is equal to the distance between the explosive and the soil body model, the wave speed tester is in signal connection with a control computer, the control computer is arranged in the signal receiving range of a centrifugal chamber, one side of the inner top of the explosion model box is provided with an optical measurement system, the optical measurement system comprises a camera and an illuminating lamp, the directions of the camera and the illuminating lamp are aligned to the soil body model, and the measurement and control system and the optical measurement system are in signal connection with the control computer.
Furthermore, the circular cylinder is made of steel, the inner diameter is 900mm, and the inner height is 900 mm.
Furthermore, the camera and the illuminating lamp are fixed into a whole, the camera and the illuminating lamp are connected with the wireless transmitter through the converter together in a wired mode, the converter converts digital signals into analog signals to send shot videos to the wireless transmitter, the wireless transmitter is connected with the wireless receiver in a signal mode, the wireless receiver is connected with the video acquisition card in a wired mode, the video acquisition card converts video data received by the wireless receiver into digital data which can be distinguished by the control computer, the video acquisition card is connected with the control computer in a wired mode, and videos in the explosion process are displayed on a display of the control computer.
Another object of the present invention is to provide a method for measuring dynamic elastic modulus of a soil model by using the above test apparatus, which comprises the following steps:
the method comprises the following steps: preparing a soil model, compacting the soil model filled into the model compacting barrel in a layered manner by using a compacting instrument by using a model compacting barrel to obtain a compacted soil model;
step two: taking the compacted model compaction barrel in the step one out of the compaction device, taking the compacted soil model out of the model compaction barrel, calculating the density rho of the compacted soil model, placing the compacted soil model on a sand layer arranged at the inner bottom of an explosion model box, arranging an explosive as an explosion source at the center of the top of the sand layer, measuring the distance between the explosive and the soil model, arranging a wave velocity tester on a circle with the explosive as the center and the distance between the explosive and the soil model as the radius, wherein the distance between the wave velocity tester and the soil model is equal to the distance between the explosive and the soil model, installing an optical measurement system at one side of the inner top of the explosion model box, aligning a camera of the optical measurement system and an illuminating lamp with the soil model, completing the assembly of the explosion box, and transferring the assembled explosion model box into a centrifuge box of a geotechnical centrifuge, installing a weight box at the other end of the rotating arm of the geotechnical centrifuge to finish the assembly of the test device for measuring the dynamic elastic modulus of the soil mass model;
step three: starting the geotechnical centrifuge, starting the wave velocity tester after the geotechnical centrifuge reaches the acceleration of 20g, detonating the explosive through the measurement and control system after the wave velocity tester stably works, recording the change data of the transverse wave velocity and the longitudinal wave velocity in the process of transferring the explosive waves from the explosion center of the explosive to the placement position of the soil mass model by the wave velocity tester, taking the independent variable as time, shooting the video of the soil mass model in the explosion process through a camera of the optical measurement system, and transmitting the collected video in the explosion process to the control computer through the wireless transmitter and the wireless receiver;
step four: according to the transverse wave propagation speed a in the Hooke medium infinite bodyTWith the density p of the compacted soil model, from
The dynamic shear modulus G of the reverse-thrust soil body model is based on the longitudinal wave propagation wave velocity a in the Hooke medium infinite bodyLWith the density p of the compacted soil model, from
Reversely pushing a Lame elastic constant lambda of the soil mass model, obtaining a dynamic elastic constant v of the soil mass model by lambda being 2G v/(1-2 v), and reversely pushing by E being 2G (1+ v) to obtain a dynamic elastic modulus E of the soil mass model;
step five: and repeating the steps one to four for a plurality of times to obtain a plurality of groups of parallel test groups, averaging the dynamic elastic modulus E of the test data obtained by the plurality of groups of parallel test groups to be used as the final dynamic modulus value of the soil body model, then drawing a relational graph by taking the compaction times of the soil body model as the abscissa and the dynamic deformation modulus value of the corresponding soil body model as the ordinate, and carrying out curve fitting to obtain a corresponding relational curve between the compaction times and the dynamic deformation modulus value.
Further, in the first step, preparing a soil model, compacting the soil model filled into the model compaction barrel in a layered manner by using a compaction instrument by using the model compaction barrel to obtain the compacted soil model, which specifically comprises the following steps:
selecting a test soil body, adding water into the test soil body to enable the water content of the test soil body to reach the range of the optimal water content of +/-2%, then filling the test soil body with the water content of +/-2% into a plastic bag for material sealing, wherein the material sealing time is not less than 24 hours for later use; taking out the test soil body after the material is sealed, filling the test soil body in a model compaction cylinder in a layering manner, wherein the height of each filling layer is one third of the height of the inner cylinder of the model compaction cylinder, finally, carrying out light pressing leveling on the surface to ensure that the soil body model is just filled in the model compaction cylinder, placing the model compaction cylinder filled in the soil body model into a compaction instrument, starting the compaction instrument, compacting the soil body model in the model compaction cylinder according to the preset weight quality and the drop height by the compaction instrument, compacting the soil body model in the model compaction cylinder for 10 times, 20 times, 30 times, 40 times, 50 times, 60 times, 70 times, 80 times and 90 times, and completing compaction;
wherein, the test soil body comprises any one of red clay, silt or sandy soil.
Furthermore, the model compaction cylinder is a circular cylinder with an inner diameter of 152mm and an inner height of 120 mm.
Further, the weight mass was 4.5kg, and the height was 450 mm.
Further, in the second step, the density ρ of the compacted soil model is obtained, specifically: and measuring the height of the compacted soil model, solving the volume of the compacted soil model due to the known inner diameter of the compacting barrel, and then weighing the mass of the soil model to obtain the density rho of the compacted soil model.
Further, before the second step, a debugging test needs to be performed on the explosion model box, and the specific process is as follows: taking out the soil body model, keeping the positions of other devices unchanged, starting a wave velocity tester, detonating the explosive through a measurement and control system after the wave velocity tester works stably, and testing the wave intensity when the explosive waves generated by detonating the explosive are transmitted to the position of the soil body model by the wave velocity tester; and the debugging test is repeated twice, so that the transverse waves and the longitudinal waves of the explosive waves generated by the explosives in the soil body model are captured by the wave velocity tester.
The invention has the beneficial effects that: according to the method for reversely pushing the deformation modulus of the soil body model by the wave velocity measured by explosion under the centrifugal condition, the dynamic shear modulus G and the dynamic elastic modulus E of the dynamic elastic modulus of the soil body are simultaneously measured by utilizing transverse and longitudinal waves generated during explosion, the deformation modulus value reversely pushed by the wave velocity measured by the centrifugal explosion provided by the technical method is higher in accuracy, the established relation between the modulus and the hammering number is convenient for model test research, technical support can be better provided for engineering design parameters, and in a centrifugal test, the test operation integrating degree of an explosion device and a centrifugal device is higher; the method solves the problem of dead weight stress loss caused by soil mass sample scale reduction in an indoor testing method, thereby improving the measurement accuracy of the dynamic elastic modulus of the soil mass and simultaneously solving the problem of insufficient measuring method of the dynamic modulus value of a laboratory soil mass model in the prior art.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a main view of a geotechnical centrifuge in accordance with an embodiment of the present invention;
FIG. 2 is a schematic illustration of an geotechnical centrifuge explosion test in accordance with an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of an explosion model box according to an embodiment of the invention;
FIG. 4 is a schematic diagram of the arrangement positions of a soil model, an explosive and a wave velocity tester according to an embodiment of the invention;
FIG. 5 is a schematic diagram of the relationship between components of a photometric system according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a method for determining dynamic elastic modulus of a soil model according to an embodiment of the present invention;
the method comprises the following steps of 1-soil body model, 2-explosive, 3-explosion model box, 4-measurement and control system, 5-optical measurement system, 6-polystyrene board, 7-sand layer, 8-geotechnical centrifuge, 9-wave velocity tester, 10-control computer, 8-1 rotating arm, 8-2 rotating table, 8-3 weight box, 8-4 centrifuge case, 5-1 camera, 5-2 illuminating lamp, 5-3 wireless transmitter, 5-4 wireless receiver and 5-5 video acquisition card.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The application provides a test device for measuring dynamic elastic modulus of a soil body model, as shown in fig. 1-4, the test device comprises a geotechnical centrifuge 8, the geotechnical centrifuge is used for providing high-speed rotation for tests, the maximal centrifugal acceleration can be provided to be 100g, the geotechnical centrifuge 8 comprises a rotating arm 8-1, the center of the rotating arm 8-1 is fixed on a rotating table 8-2, and the rotating table 8-2 drives the rotating arm 8-1 to rotate. The center of the rotating arm 8-1 is provided with a measurement and control system 4. The two ends of the rotating arm 8-1 are respectively provided with a weight box 8-3 and a centrifuge case 8-4 which are oppositely arranged, the weight box 8-3 is used for carrying out weight balancing on the centrifuge case 8-4 with the same mass, and an explosion model case 3 is placed in the centrifuge case 8-4 and is used for providing an explosion space;
the explosion model box 3 is a round cylinder body, the round cylinder body is preferably made of steel, the inner diameter of the round cylinder body is preferably 900mm, the inner height of the round cylinder body is preferably 900mm, the mass of the explosion model box 3 is preferably 375kg, the inner wall of the explosion model box 3 is provided with a layer of polystyrene plate 6, the purpose of the polystyrene plate 6 is to absorb explosion reflection waves, the thickness of the polystyrene plate 6 is 3 cm-10 cm, preferably 5cm, the inner bottom of the explosion model box 3 is provided with a sand layer 7, the purpose of the sand layer 7 is to prevent the explosive 2 from directly contacting the polystyrene plate 6 and play a certain role of absorbing the explosion reflection waves, the thickness of the sand layer 7 is 20 cm-50 cm, preferably 30cm, the top center of the sand layer 7 is provided with the explosive 2 serving as an explosion source, an exploder inside the explosive 2 is in signal connection with the measurement and control system 4, the measurement and control system 4 is arranged at the center of the rotating arm 8-1, for controlling the detonation of the explosive 2, a soil body model 1 is arranged on the top edge of the sand layer 7, one side of the soil body model 1, which is far away from the explosive 2, is fixedly attached to the inner wall of an explosion model box 3, the distance between the explosive 2 and the soil body model 1 is preferably 400mm, a wave velocity tester 9 is arranged on a circle with the distance between the explosive 2 and the soil body model 1 as a radius, the distance between the wave velocity tester 9 and the soil body model 1 is equal to the distance between the explosive 2 and the soil body model 1, the wave velocity tester 9 is in signal connection with a control computer 10, the control computer 10 is arranged in a range capable of well receiving signals of a centrifugal chamber, a light measurement system 5 is arranged on one side of the inner top of the explosion model box 3, as shown in fig. 5, the light measurement system 5 comprises a camera 5-1, the camera 5-1 and an illuminating lamp 5-2 are integrated, and the illuminating lamp 5-2 is fixed to provide enough light intensity for the camera 5-1 in the shooting process, the camera 5-1 and the illuminating lamp 5-2 are connected with the wireless transmitter 5-3 through a converter in a wired mode, the converter converts digital signals into analog signals and is used for sending shot videos to the wireless transmitter 5-3, the wireless transmitter 5-3 is in signal connection with the wireless receiver 5-4, the wireless receiver 5-4 is in wired connection with the video acquisition card 5-5, the video acquisition card 5-5 converts video data received by the wireless receiver 5-4 into digital data which can be distinguished by the control computer 10, the video acquisition card 5-5 is in wired connection with the control computer 10, and videos in the explosion process are displayed on a display of the control computer 10. The orientation of the camera 5-1 and the illuminating lamp 5-2 is aligned with the soil body model 1, and the measurement and control system 4 and the optical measurement system 5 are in signal connection with the control computer 10.
And the measurement and control system 4 is arranged at the center of the rotating arm 8-1 and is in wired connection with the control computer 10, and the measurement and control system 4 adopts special measurement and control system software and is used for detonation control, synchronous acquisition, storage, analysis, callback and the like of transient signals.
The application provides a method for measuring dynamic elastic modulus of a soil body model by adopting the test device, which specifically comprises the following steps:
the method comprises the following steps: preparing a soil model 1, compacting the soil model 1 filled into the model compacting barrel in a layered mode by using a compaction instrument by using a model compacting barrel to obtain a compacted soil model 1, wherein the concrete process is as follows:
selecting a test soil body, adding water into the test soil body to enable the water content of the test soil body to reach the range of the optimal water content of +/-2%, then filling the test soil body with the water content of +/-2% into a plastic bag for material sealing, wherein the material sealing time is not less than 24h for standby application, and the material sealing method can ensure the uniform humidity of the test soil body; taking out the test soil body after the blank filling, filling the test soil body into a model compaction cylinder in a layering way by using a small shovel, wherein the model compaction cylinder is preferably a circular cylinder body, the inner diameter is preferably 152mm, the inner height is preferably 120mm, the height of each filling layer is one third of the inner cylinder height of the model compaction cylinder, finally, the surface is leveled by lightly pressing to ensure that the soil body model 1 is just filled into the model compaction cylinder, the model compaction cylinder filled into the soil body model 1 is placed into a compaction instrument, starting the compaction device, compacting by the compaction device according to the preset weight mass and height, wherein the weight mass is preferably 4.5kg, the height is preferably 450mm, and (3) compacting the soil body model 1 in the model compacting barrel, wherein nine compacting tests are performed for 10 times, 20 times, 30 times, 40 times, 50 times, 60 times, 70 times, 80 times and 90 times to complete compacting, and nine tests are performed to ensure that different times are available and not repeated.
Wherein, the test soil body comprises any one of red clay, silt or sandy soil.
Step two: taking out the compacted model compaction barrel in the step one from the compaction device, then taking out the compacted soil model 1 from the model compaction barrel, measuring the height of the compacted soil model 1 by adopting a graduated scale, and obtaining the volume of the compacted soil model 1 because the inner diameter of the compaction barrel is known. The mass of the soil model 1 is weighed by an electronic scale, and the density rho of the compacted soil model 1 is obtained. Placing the compacted soil model 1 on a sand layer 7 arranged at the inner bottom of an explosion model box 3, arranging an explosive 2 at the top center position of the sand layer 7 to be used as an explosion source, adopting a common 8# electric detonator as the explosive 2, measuring the distance between the explosive 2 and the soil model 1 by using a tape measure, arranging a wave velocity tester 9 on a circle taking the explosive 2 as the center and the distance between the explosive 2 and the soil model 1 as the radius, enabling the distance between the wave velocity tester 9 and the soil model 1 to be equal to the distance between the explosive 2 and the soil model 1, installing an optical measurement system 5 at one side of the inner top of the explosion model box 3, aligning a camera 5-1 and an illuminating lamp 5-2 of the optical measurement system 5 with the soil model 1 to finish the assembly of the explosion model box 3, transferring the assembled explosion model box 3 into a centrifugal case 8-4 of a geotechnical centrifuge 8, installing a counterweight box 8-3 at the other end of a rotating arm 8-1 of the geotechnical centrifuge 8, and finishing the assembly of the test device for measuring the dynamic elastic modulus of the soil body model.
Step three: starting the geotechnical centrifuge 8, after the geotechnical centrifuge 8 reaches the acceleration of 20g, starting the wave velocity tester 9, after the wave velocity tester 9 works stably, detonating the explosive 2 through the measurement and control system 4, recording the change data of the transverse wave velocity and the longitudinal wave velocity in the process that the explosive wave is transmitted to the placing position of the soil mass model 1 from the explosion center of the explosive 2 by the wave velocity tester 9, wherein the independent variable is time, shooting the video of the soil mass model 1 in the explosion process through the camera 5-1 of the optical measurement system 5, transmitting the collected video in the explosion process to the control computer 10 through the wireless transmitter 5-3 and the wireless receiver 5-4, transmitting the video in the explosion process to the control computer 10 for observing and ensuring that when the geotechnical centrifuge rotates at high speed, the test in the centrifuge case 8-4 is normally carried out, and the setting position of the equipment is not changed, the test was effective.
Step four: according to the transverse wave propagation speed a in the Hooke medium infinite bodyTWith the velocity a of the longitudinal wave propagationLThe relation formula (1) can obtain the dynamic shear modulus of the soil mass model 1 by reverse deductionG. Formula (2) for the dynamic elastic constant ν and the dynamic elastic modulus E. The transverse wave velocity a of the explosive wave collected by the wave velocity tester 9 when the explosive wave passes through the soil body model 1TVelocity of sum longitudinal wave aLThe velocity a of the transverse waveTVelocity of sum longitudinal wave aLThe numerical values are respectively substituted into the formula (2), and the dynamic shear modulus G, the dynamic elastic constant ν and the dynamic elastic modulus E of the soil body model 1 can be obtained through calculation. The equations (1) (2) are as follows:
in the formula: rho is the density of the soil model 1; lambda is a Lame elastic constant, lambda is 2G v/(1-2 v), and v is a dynamic elastic constant; g is the dynamic shear modulus; and E is the dynamic elastic modulus.
Step five: repeating the first step and the fourth step for a plurality of times to obtain a plurality of groups of parallel test groups, adopting two groups of parallel test groups, averaging the test data dynamic elastic modulus E obtained by the plurality of groups of parallel test groups to be used as a final dynamic modulus value of the soil mass model 1, then drawing a relational graph by taking the compaction times of the soil mass model 1 as an abscissa and the corresponding dynamic deformation modulus value of the soil mass model 1 as an ordinate, and performing curve fitting to obtain a corresponding relational curve between the compaction times and the dynamic deformation modulus value, wherein the relational curve has a complicated meaning to relevant test operations of foundation models of other soil of the same type, and the corresponding dynamic deformation modulus value of the soil mass can be calculated by substituting the compaction times into the relational curve obtained by the test.
Before the second step, debugging test needs to be carried out on the explosion model box 3, and the specific process is as follows: taking out the soil body model 1, keeping the positions of other devices unchanged, starting the wave velocity tester 9, detonating the explosive 2 through the measurement and control system 4 after the wave velocity tester 9 works stably, and testing the wave intensity of the explosive wave generated by detonating the explosive 2 when the explosive wave is transmitted to the soil body model 1 by the wave velocity tester 9; the debugging test is repeated twice, so that the transverse wave and the longitudinal wave of the explosive wave generated by the explosive 2 in the soil body model 1 can be captured by the wave velocity tester 9, and the wave intensity and the small difference of the two waves are regarded as being qualified within the range of +/-5%. Otherwise, the amount of the explosive 2 is adjusted until the test conditions are met.
It is noted that, in the present application, relational terms such as first, second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
All the embodiments in the present specification are described in a related manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.
Claims (9)
1. A test device for measuring dynamic elastic modulus of a soil mass model is characterized by comprising a geotechnical centrifuge (8), for testing to provide high speed rotation, the geotechnical centrifuge (8) comprises a rotating arm (8-1), the center of the rotating arm (8-1) is fixed on the rotating platform (8-2), the rotating platform (8-2) drives the rotating arm (8-1) to rotate, the center of the rotating arm (8-1) is provided with a measurement and control system (4), two ends of the rotating arm (8-1) are respectively provided with a weight box (8-3) and a centrifuge case (8-4) which are oppositely arranged, the weight box (8-3) is used for carrying out weight balancing on the centrifuge case (8-4) with the same mass, an explosion model box (3) is arranged in the centrifuge case (8-4) and is used for providing an explosion space;
the explosion model box (3) is a circular cylinder, the inner wall of the explosion model box (3) is provided with a layer of polystyrene plate (6), the thickness of the polystyrene plate (6) is 3-10 cm, the inner bottom of the explosion model box (3) is provided with a layer of sand layer (7), the thickness of the sand layer (7) is 20-50 cm, the top center position of the sand layer (7) is provided with an explosive (2) which is used as an explosion source, an explosion initiator inside the explosive (2) is in signal connection with a measurement and control system (4), the top edge of the sand layer (7) is provided with a soil body model (1), one side of the soil body model (1) far away from the explosive (2) is fixedly attached to the inner wall of the explosion model box (3), a wave velocity tester (9) is arranged on a circle taking the distance between the explosive (2) and the soil body model (1) as a radius, and the distance between the wave velocity tester (9) and the soil body model (1), the distance between the explosive (2) and the soil model (1) is equal, the wave velocity tester (9) is in signal connection with the control computer (10), the control computer (10) is arranged in a signal receiving range of the centrifugal chamber, one side of the inner top of the explosion model box (3) is provided with the optical measurement system (5), the optical measurement system (5) comprises a camera (5-1) and an illuminating lamp (5-2), the directions of the camera (5-1) and the illuminating lamp (5-2) are aligned to the soil model (1), and the measurement and control system (4) and the optical measurement system (5) are in signal connection with the control computer (10).
2. The test device for testing the dynamic elastic modulus of the soil mass model as claimed in claim 1, wherein the circular cylinder is made of steel, the inner diameter is 900mm, and the inner height is 900 mm.
3. The testing device for testing the dynamic elastic modulus of the soil mass model according to claim 1, wherein the camera (5-1) and the illuminating lamp (5-2) are fixed into a whole, the camera (5-1) and the illuminating lamp (5-2) are connected with the wireless transmitter (5-3) through a converter in a wired mode, the converter converts digital signals into analog signals to send shot videos to the wireless transmitter (5-3), the wireless transmitter (5-3) is connected with the wireless receiver (5-4) in a signal mode, the wireless receiver (5-4) is connected with the video acquisition card (5-5) in a wired mode, the video acquisition card (5-5) converts video data received by the wireless receiver (5-4) into digital data which can be distinguished by the control computer (10), the video acquisition card (5-5) is connected with the control computer (10) by wire, and displays the video in the explosion process on the display of the control computer (10).
4. A method for measuring dynamic elastic modulus of a soil model by using the test device as claimed in any one of claims 1 to 3, which is characterized by comprising the following steps:
the method comprises the following steps: preparing a soil body model (1), compacting the soil body model (1) filled into the model compacting barrel in a layered mode by using a compaction instrument by using a model compacting barrel to obtain a compacted soil body model (1);
step two: taking the compacted model compaction barrel in the step one out of the compaction device, taking the compacted soil model (1) out of the model compaction barrel, calculating the density rho of the compacted soil model (1), placing the compacted soil model (1) on a sand layer (7) arranged at the inner bottom of an explosion model box (3), arranging an explosive (2) at the center of the top of the sand layer (7) to be used as an explosion source, measuring the distance between the explosive (2) and the soil model (1), taking the explosive (2) as the center, arranging a wave velocity tester (9) on a circle taking the distance between the explosive (2) and the soil model (1) as the radius, setting the distance between the wave velocity tester (9) and the soil model (1) as well as the distance between the explosive (2) and the soil model (1), and installing an optical measurement system (5) at one side of the inner top of the explosion model box (3), aligning a camera (5-1) of a light measurement system (5) and an illuminating lamp (5-2) to a soil mass model (1) to complete the assembly of an explosion model box (3), transferring the assembled explosion model box (3) into a centrifuge case (8-4) of a geotechnical centrifuge (8), installing a weight box (8-3) at the other end of a rotating arm (8-1) of the geotechnical centrifuge (8), and completing the assembly of a test device for measuring the dynamic elastic modulus of the soil mass model;
step three: starting a geotechnical centrifuge (8), after the geotechnical centrifuge (8) reaches an acceleration of 20g, starting a wave velocity tester (9), detonating the explosive (2) through a measurement and control system (4) after the wave velocity tester (9) works stably, recording the change data of the transverse and longitudinal wave velocities in the process that the explosive waves are transmitted to the placing position of the soil body model (1) from the explosion center of the explosive (2) by the wave velocity tester (9), wherein the independent variable is time, shooting the video of the soil body model (1) in the explosion process through a camera (5-1) of a light measurement system (5), and transmitting the collected video in the explosion process to a control computer (10) through a wireless transmitter (5-3) and a wireless receiver (5-4);
step four: according to the transverse wave propagation speed a in the Hooke medium infinite bodyTWith the density rho of the compacted soil model (1) from
The dynamic shear modulus G of the reverse-thrust soil body model (1) is based on the wave velocity a of longitudinal wave propagation in the Hooke medium infinite bodyLWith the density rho of the compacted soil model (1) from
The dynamic elastic constant v of the soil mass model (1) is obtained by reversely pushing the Lame elastic constant lambda of the soil mass model (1), and the dynamic elastic constant v of the soil mass model (1) is obtained by reversely pushing E (2G (1+ v));
step five: and repeating the steps one to four for a plurality of times to obtain a plurality of groups of parallel test groups, averaging the dynamic elastic modulus E of the test data obtained by the plurality of groups of parallel test groups to be used as the final dynamic modulus value of the soil body model (1), then drawing a relational graph by taking the compaction times of the soil body model (1) as the abscissa and the dynamic deformation modulus value of the corresponding soil body model (1) as the ordinate, and carrying out curve fitting to obtain a corresponding relational curve between the compaction times and the dynamic deformation modulus value.
5. The method for determining the dynamic elastic modulus of the soil mass model according to claim 4, wherein in the first step, the soil mass model (1) is prepared, the soil mass model (1) is compacted by using a compaction machine by using a compaction cylinder, and the soil mass model (1) filled into the compaction cylinder in a layered manner is compacted to obtain the compacted soil mass model (1), specifically:
selecting a test soil body, adding water into the test soil body to enable the water content of the test soil body to reach the range of the optimal water content of +/-2%, then filling the test soil body with the water content of +/-2% into a plastic bag for material sealing, wherein the material sealing time is not less than 24 hours for later use; taking out the test soil after the material is sealed, filling the test soil in a model compaction cylinder in a layered mode, wherein the height of each filling layer is one third of the height of the inner cylinder of the model compaction cylinder, finally, carrying out light pressing leveling on the surface to ensure that the soil model (1) is just filled in the model compaction cylinder, placing the model compaction cylinder filled in the soil model (1) in a compaction instrument, starting the compaction instrument, compacting the soil model (1) in the model compaction cylinder according to the preset weight quality and the drop height, compacting the soil model (1) in the model compaction cylinder, wherein the compaction times are nine compaction tests of 10 times, 20 times, 30 times, 40 times, 50 times, 60 times, 70 times, 80 times and 90 times, and completing compaction;
wherein, the test soil body comprises any one of red clay, silt or sandy soil.
6. The method of claim 5 wherein the model compaction cylinder is a circular cylinder with an inner diameter of 152mm and an inner height of 120 mm.
7. The method of claim 5, wherein the weight has a mass of 4.5kg and a drop height of 450 mm.
8. The method for determining the dynamic elastic modulus of the soil mass model according to claim 4, wherein in the second step, the density p of the compacted soil mass model (1) is determined by: and measuring the height of the compacted soil model (1), solving the volume of the compacted soil model (1) due to the known inner diameter of the compacting barrel, and then weighing the mass of the soil model (1) to obtain the density rho of the compacted soil model (1).
9. The method for determining the dynamic elastic modulus of a soil mass model according to claim 4, wherein the debugging test of the explosion model box (3) is required before the step two, and the specific process is as follows: taking out the soil body model (1), keeping the positions of other devices unchanged, starting the wave velocity tester (9), detonating the explosive (2) through the measurement and control system (4) after the wave velocity tester (9) works stably, and testing the wave intensity when the explosive waves generated by detonating the explosive (2) are transmitted to the position of the soil body model (1) by the wave velocity tester (9); the debugging test is repeated twice, and the transverse wave and the longitudinal wave of the explosive wave generated by the explosive (2) twice in the soil body model (1) are all captured by the wave velocity tester (9).
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