CN113075027B - Test device and method for measuring dynamic elastic modulus of soil body model - Google Patents

Abstract

The invention discloses a test device and method for measuring the dynamic elastic modulus of a soil model. The test device includes a geotechnical centrifuge and an explosion model box. The inner bottom of the explosion model box is provided with explosives, a soil model, a wave velocity tester, and an optical tester. system. Place the compacted soil model in the explosion model box, detonate the explosives, record the change data of the blast wave transverse and longitudinal wave velocity, and obtain the dynamic elastic modulus of the soil model by reverse deduction. The invention is a test device and method for measuring the dynamic elastic modulus of a soil body model. The dynamic shear modulus of the soil body dynamic elastic modulus is realized by the method of measuring the deformation modulus of the soil body model in the centrifugal condition by measuring the explosion wave velocity. Simultaneous measurement of dynamic elastic modulus and deformation modulus value derived from this technical method is more accurate. The relationship between the established modulus and the number of hammer blows is convenient for model test research, and can better provide engineering design parameters. Technical Support.

Description

A test device and method for measuring dynamic elastic modulus of soil model

technical field

The invention belongs to the technical field of civil engineering, and relates to a test device and method for measuring the dynamic elastic modulus of a soil model.

Background technique

As an important parameter of soil dynamic characteristics, dynamic elastic modulus is an essential dynamic parameter in the analysis of the seismic response of soil layers and foundations, as well as an essential parameter in the analysis of seismic subdivisions. Therefore, the method of measuring the dynamic elastic modulus of soil, especially the method of accurately measuring the dynamic elastic modulus of soil is very critical. At present, the methods for determining the dynamic elastic modulus of soil include field test method and indoor test method. Among them, the on-site test method has higher requirements on the test site and environmental conditions, and has defects such as time-consuming and labor-intensive, harsh test conditions and high cost.

Indoor test methods include static method and dynamic method. The static method has simple requirements for measuring equipment, and it is more common to measure the elastic modulus of soil in the laboratory. However, the static method is a method that has destructive properties to the sample and does not have the opportunity to repeat the test. The static method generally uses an indoor triaxial instrument for triaxial compression test or an unconfined compression instrument for uniaxial compression test. The static method has large loading and slow loading speed, which is prone to creep and causes the measured soil elastic modulus to be low. , the resulting relative error is relatively high, which can reach a relative error rate of 5%. The dynamic method is used to test the elastic modulus, and the size and weight of the tested samples are wider than those of the static method. The dynamic method generally adopts the ultrasonic method. By measuring the propagation time of the ultrasonic wave in the sample and the length of the sample, the longitudinal and lateral propagation velocities are obtained, and the value of the dynamic elastic modulus of the soil is obtained. The dynamic method is loaded instantaneously and at a high frequency. The stress on the soil sample is very small with periodic changes, and the strain does not need to be measured, which eliminates the problems of the static method. The stress value generated in the soil sample is only about 0.001Mpa, which is equivalent to the elastic modulus measured when the stress is close to zero on the stress-strain curve. Moreover, the soil sample is intact after the measurement, and the measurement can be repeated on the same soil sample. However, although the measurement accuracy of the dynamic method is very high, it is generally used to determine the dynamic elastic modulus of materials such as metals and ceramics. value is closer to reality. The indoor method is generally not used to measure the dynamic elastic modulus of the foundation soil, because when the measurement area of the foundation is large, the loss of the self-weight stress of the foundation soil after sampling will cause the difference from the actual foundation state to be too large, which will cause the soil sample to be scaled down. Due to the loss of self-weight stress, the stress state of the soil sample is inconsistent with the actual foundation stress state, resulting in the problem that the accuracy of the measurement value of the soil dynamic elastic modulus decreases.

Therefore, in view of the problems of the above-mentioned indoor testing methods in the measurement of soil dynamic elastic modulus, it is necessary to provide a new method that can accurately measure the dynamic elastic modulus of soil models under indoor conditions. The problem of self-weight stress loss caused by the downsizing of the bulk sample can improve the measurement accuracy of soil dynamic elastic modulus.

SUMMARY OF THE INVENTION

In order to achieve the above purpose, the present invention provides a test device and method for measuring the dynamic elastic modulus of a soil model. The method of measuring the deformation modulus of a soil model by measuring the velocity of the explosion under centrifugal conditions uses the transverse and longitudinal waves generated during the explosion, The simultaneous measurement of dynamic shear modulus and dynamic elastic modulus of soil dynamic elastic modulus is realized. The deformation modulus value derived from centrifugal explosion wave velocity test provided by this technical method is more accurate, and the established modulus and The relationship between the number of hammer blows is convenient for model test research, which can better provide technical support for engineering design parameters, and in the centrifugal test, the explosive device and the centrifugal device have a high degree of fit for the test operation; this application solves the problem of indoor testing The problem of self-weight stress loss caused by the scaling of soil samples and the problem of insufficient measurement methods for the dynamic modulus value of laboratory soil models in the prior art.

The technical scheme adopted by the present invention is that a test device for measuring the dynamic elastic modulus of a soil model includes a geotechnical centrifuge for providing high-speed rotation for testing, and the geotechnical centrifuge includes a rotating arm, and the center position of the rotating arm is fixed on a turntable, The turntable drives the rotating arm to rotate, a measurement and control system is set at the center of the rotating arm, and the opposite ends of the rotating arm are respectively provided with a counterweight box and a centrifugal case. Model boxes to provide room for explosions;

The explosion model box is a circular cylinder, the inner wall of the explosion model box is provided with a layer of polystyrene board, the thickness of the polystyrene board is 3cm-10cm, and a layer of sand is arranged on the inner bottom of the explosion model box, and the thickness of the sand layer is 20cm～50cm, an explosive is set at the top center of the sand layer, which is used as an explosion source. The detonator inside the explosive is connected to the signal of the measurement and control system. A soil model is set on the top edge of the sand layer, and the soil model is far from the explosive. It is fitted and fixed with the inner wall of the explosion model box. A wave velocity tester is set on a circle with the distance between the explosive and the soil model as the radius, and the distance between the wave velocity tester and the soil model is the same as the distance between the explosive and the soil model. Equivalent, the wave speed tester is connected with the control computer signal, the control computer is set in the signal receiving range of the centrifugal chamber, and a photometric system is provided on the inner top side of the explosion model box, and the photometric system includes a camera and a light, a camera and a light. The orientation is aligned with the soil model, and the measurement and control system and the optical measurement system are connected with the control computer signal.

Further, the circular cylinder is made of steel, with an inner diameter of 900 mm and an inner height of 900 mm.

Further, the camera and the lighting are fixed as a whole, and the camera and the lighting are wired together with the wireless transmitter through the converter. The converter converts the digital signal into an analog signal and sends the captured video to the wireless transmitter. The receiver signal is connected, the wireless receiver is wired with the video capture card, the video capture card converts the video data received by the wireless receiver into digital data that can be identified by the control computer, and the video capture card is wired with the control computer. A video of the explosion is shown above.

Another object of the present invention is to provide a method for measuring the dynamic elastic modulus of a soil model by the above-mentioned test device, comprising the following steps:

Step 1: prepare a soil model, use a model compaction cylinder, and use a compactor to compact the soil model filled in layers into the model compaction cylinder to obtain a compacted soil model;

Step 2: Take out the compacted model compaction cylinder from the compactor in step 1, then take out the compacted soil model from the model compaction cylinder, and obtain the density ρ of the compacted soil model , and then place the compacted soil model on the sand layer set at the inner bottom of the explosion model box. The top center of the sand layer is provided with explosives, which are used as explosion sources to measure the distance between the explosive and the soil model. A wave velocity tester is set on a circle with the explosive as the center and the distance between the explosive and the soil model as the radius, and the distance between the wave velocity tester and the soil model is equal to the distance between the explosive and the soil model. A photometric system is installed on the inner top side of the photometric system. The camera and lighting of the photometric system are aimed at the soil model to complete the assembly of the explosion model box. Transfer the assembled explosion model box to the centrifugal box of the geotechnical centrifuge. A counterweight box is installed at the other end of the rotating arm of the centrifuge to complete the assembly of the test device for measuring the dynamic elastic modulus of the soil model;

Step 3: Start the geotechnical centrifuge. After the geotechnical centrifuge reaches an acceleration of 20g, start the wave speed tester. After the wave speed tester works stably, detonate the explosive through the measurement and control system. The wave speed tester records the explosion wave from the explosive center of the explosive. The change data of the transverse and longitudinal wave velocity in the process of placing the body model at the position, the independent variable is time, and the video of the soil model during the explosion is captured by the camera of the optical measurement system, and the collected explosion data is collected by the wireless transmitter and wireless receiver. The video in the process is transmitted to the control computer;

反推土体模型的动态剪切模量G，根据Hooke介质无限体中纵波传播波速a_L与经击实的土体模型的密度ρ，由

反推土体模型的拉梅弹性常数λ，由λ＝2Gν/(1-2ν)求得土体模型的动态弹性常数ν，由E＝2G(1+ν)反推得到土体模型的动态弹性模量E；Step 4: According to the shear wave propagation velocity a _T in the infinite body of Hooke medium and the density ρ of the compacted soil model, by

The dynamic shear modulus G of the reverse thrust soil model, according to the longitudinal wave propagation velocity a _L in the Hooke medium infinite body and the density ρ of the compacted soil model, is given by

The Lame elastic constant λ of the inversely pushed soil model, the dynamic elastic constant ν of the soil model can be obtained from λ=2Gν/(1-2ν), and the dynamic elastic constant ν of the soil model can be obtained from E=2G(1+ν). elastic modulus E;

Step 5: Repeat steps 1 to 4 several times to obtain several groups of parallel test groups, and take the average value of the dynamic elastic modulus E of the test data obtained from several groups of parallel test groups as the dynamic modulus value of the final soil model. Then, take the number of compaction of the soil model as the abscissa, and the value of the dynamic deformation modulus of the corresponding soil model as the ordinate to draw a relationship diagram, and perform curve fitting to obtain the relationship between the number of compactions and the value of the dynamic deformation modulus. Correspondence curve.

Further, in step 1, a soil model is prepared, a model compaction cylinder is used, and a compactor is used to compact the soil model filled in layers into the model compaction cylinder to obtain a compacted soil model. for:

Select the test soil body, add water to the test soil body, make the moisture content of the test soil body reach the range of the optimum moisture content ± 2%, and then pack the test soil body with the moisture content within the range of the optimum moisture content ± 2%. Put it into a plastic bag for stuffing, the stuffing time is not less than 24h, and it is ready for use; after taking out the stuffing, the test soil is filled into the model compaction cylinder in layers, and the height of each filling layer is the model compaction cylinder. Finally, lightly press and level the surface to make the soil model just fill the model compaction cylinder, and place the model compaction cylinder filled into the soil model into the compactor. Start the compactor, and the compactor performs compaction according to the preset weight and drop height, and compacts the soil model in the model compaction cylinder. The number of compactions is 10 times, 20 times, and 30 times. , 40 times, 50 times, 60 times, 70 times, 80 times, 90 times to complete the compaction;

Wherein, the test soil includes any one of red clay, silt or sand.

Further, the model compaction cylinder is a circular cylinder with an inner diameter of 152mm and an inner height of 120mm.

Further, the weight of the weight is 4.5kg, and the drop height is 450mm.

Further, in step 2, the density ρ of the compacted soil model is obtained, specifically: measuring the height of the compacted soil model, since the inner diameter of the compacted cylinder is known, the compacted soil is obtained. The volume of the body model is calculated, and then the mass of the soil model is obtained, and the density ρ of the compacted soil model is obtained.

Further, before step 2, the explosion model box needs to be debugged and tested. The specific process is: take out the soil model, keep the positions of other devices unchanged, start the wave speed tester, and after the wave speed tester works stably, pass the measurement and control system. The explosive is detonated, and the wave velocity tester tests the wave intensity of the explosive wave generated by the detonated explosive when it is transmitted to the location of the soil model; repeat the debugging test twice to ensure that the two explosive waves generated by the explosive have both transverse and longitudinal waves in the soil model. Captured by a wave velocity tester.

The beneficial effects of the present invention are as follows: the present application realizes the dynamic shear modulus G of the dynamic elastic modulus of the soil by using the transverse and longitudinal waves generated during the explosion by measuring the deformation modulus of the soil model by the explosion wave velocity under centrifugal conditions. Simultaneous measurement of the dynamic elastic modulus E and the centrifugal explosion wave velocity test provided by this technical method is more accurate. It provides better technical support for engineering design parameters, and in the centrifugal test, the explosive device and the centrifugal device have a high degree of fit; this application solves the problem of the self-weight stress loss caused by the scale of the soil sample in the indoor test method. Therefore, the measurement accuracy of the dynamic elastic modulus of the soil body is improved, and the problem of insufficient measurement methods of the dynamic modulus value of the laboratory soil model in the prior art is solved at the same time.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative efforts.

1 is a front view of a geotechnical centrifuge according to an embodiment of the present invention;

2 is a schematic diagram of an explosion test of a geotechnical centrifuge according to an embodiment of the present invention;

3 is a schematic structural diagram of an explosion model box according to an embodiment of the present invention;

4 is a schematic diagram of the setting positions of the soil model, explosive, and wave velocity tester according to an embodiment of the present invention;

5 is a schematic diagram of the relationship between the components of the optical measuring system according to the embodiment of the present invention;

6 is a schematic diagram of a method for measuring the dynamic elastic modulus of a soil model according to an embodiment of the present invention;

1- Soil model, 2- Explosives, 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 arm, 8-2 turntable, 8-3 counterweight box, 8-4 centrifugal case, 5-1 camera, 5-2 lighting, 5-3 wireless transmitter, 5-4 Wireless receiver, 5-5 video capture card.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The application provides a test device for measuring the dynamic elastic modulus of a soil model, as shown in Figures 1 to 4, including a geotechnical centrifuge 8, which is used to provide high-speed rotation for testing, and can provide a maximum centrifugal acceleration of 100g. 8 includes a rotating arm 8-1, the center position of the rotating arm 8-1 is fixed on the turntable 8-2, and the turntable 8-2 drives the rotating arm 8-1 to rotate. A measurement and control system 4 is arranged at the center of the rotating arm 8-1. The two ends of the rotating arm 8-1 are respectively provided with a counterweight box 8-3 and a centrifugal box 8-4 arranged oppositely. 4. An explosion model box 3 is placed in it to provide an explosion space;

The explosion model box 3 is a circular cylinder, the circular cylinder is preferably made of steel, the inner diameter of the circular cylinder is preferably 900mm, the inner height is preferably 900mm, the mass of the explosion model box 3 is preferably 375kg, and the explosion model box 3 is preferably 375kg. The inner wall is provided with a layer of polystyrene board 6. The purpose of the polystyrene board 6 is to absorb the reflected wave of the explosion. The thickness of the polystyrene board 6 is 3cm to 10cm, preferably 5cm. The inner bottom of the explosion model box 3 is provided with a layer Sand layer 7, the purpose of setting the sand layer 7 is to prevent the explosive 2 from being in direct contact with the polystyrene plate 6, and at the same time, it also plays a role in absorbing the reflected wave of the explosion. The thickness of the sand layer 7 is 20cm to 50cm, preferably 30cm, and the sand The top center position of the layer 7 is provided with an explosive 2, which is used as an explosion source. The detonator inside the explosive 2 is connected with a signal to the measurement and control system 4, and the measurement and control system 4 is arranged at the center of the rotating arm 8-1 for controlling the explosive 2. The top edge of the sand layer 7 is provided with a soil model 1, the side of the soil model 1 away from the explosive 2 is fitted and fixed with the inner wall of the explosion model box 3, and the distance between the explosive 2 and the soil model 1 is preferably 400mm, a wave speed tester 9 is set on a circle with the distance between the explosive 2 and the soil model 1 as the radius, and the distance between the wave speed tester 9 and the soil model 1 is equal to the distance between the explosive 2 and the soil model 1 , the wave speed tester 9 is signal-connected with the control computer 10, the control computer 10 is arranged in the range where the centrifugal chamber signal can be well received, and a photometric system 5 is provided on the inner top side of the explosion model box 3, as shown in FIG. The measuring system 5 includes a camera 5-1, the camera 5-1 and the lighting lamp 5-2 are fixed as a whole, the lighting lamp 5-2 provides the camera 5-1 with sufficient light intensity for the shooting process, and the camera 5-1 and the lighting lamp 5 -2 is wired to the wireless transmitter 5-3 through the converter, and the converter converts the digital signal into an analog signal, which is used to send the captured video to the wireless transmitter 5-3, and the wireless transmitter 5-3 is connected to the wireless receiver The wireless receiver 5-4 is connected to the video capture card 5-5 by wire, and the video capture card 5-5 converts the video data received by the wireless receiver 5-4 into digital data that can be identified by the control computer 10. , the video capture card 5-5 is wired with the control computer 10 to display the video during the explosion on the display of the control computer 10. The orientation of the camera 5-1 and the lighting lamp 5-2 is aligned with the soil model 1, and the measurement and control system 4 and the optical measurement system 5 are connected with the control computer 10 by signals.

The measurement and control system 4 is arranged at the center of the rotating arm 8-1, and is wired to the control computer 10. The measurement and control system 4 adopts special measurement and control system software for detonation control, synchronous acquisition, storage, analysis and callback of transient signals.

The application provides a method for measuring the dynamic elastic modulus of a soil model by using the above-mentioned test device, which specifically includes the following steps:

Step 1: Prepare a soil model 1, use a model compaction cylinder, and use a compactor to compact the soil model 1 filled in layers into the model compaction cylinder to obtain a compacted soil model 1. The specific process as described below:

Select the test soil body, add water to the test soil body, make the moisture content of the test soil body reach the range of the optimum moisture content ± 2%, and then pack the test soil body with the moisture content within the range of the optimum moisture content ± 2%. Put it into a plastic bag for stuffing, the stuffing time is not less than 24h, and it is ready for use. This stuffing method can ensure that the humidity of the test soil is uniform; the test soil after taking out the stuffing is filled into the model layer by layer with a small shovel. The compaction cylinder, the model compaction cylinder is preferably a circular cylinder, the inner diameter is preferably 152mm, the inner height is preferably 120mm, and the height of each filling layer is one third of the height of the inner cylinder of the model compaction cylinder, Finally, lightly press and level the surface, so that the soil model 1 just fills the model compaction cylinder, place the model compaction cylinder filled in the soil model 1 into the compactor, start the compactor, and the compactor The compaction is carried out according to the preset weight and drop height. The weight of the weight is preferably 4.5kg, and the drop height is preferably 450mm. The soil model 1 in the model compaction cylinder is compacted, and the number of compactions is 10 times, 20 times, 30 times, 40 times, 50 times, 60 times, 70 times, 80 times, 90 times, nine sets of compaction tests, complete the compaction, and carry out nine sets of the test to ensure that there are different times and no repetitions .

Wherein, the test soil includes any one of red clay, silt or sand.

Step 2: Take out the compacted model compaction cylinder from the compactor in step 1, then take out the compacted soil model 1 from the model compaction cylinder, and use a scale to measure the compacted soil model The height of 1, since the inner diameter of the compaction cylinder is known, the volume of the compacted soil model 1 is obtained. The mass of the soil model 1 is weighed by an electronic scale, and the density ρ of the compacted soil model 1 is obtained. The compacted soil model 1 is then placed on the sand layer 7 provided at the inner bottom of the explosion model box 3. The top center of the sand layer 7 is provided with an explosive 2, which is used as an explosion source. Detonator, use a tape measure to measure the distance between the explosive 2 and the soil model 1, set the wave speed tester 9 on the circle with the explosive 2 as the center and the distance between the explosive 2 and the soil model 1 as the radius, and the wave speed tester 9. The distance from the soil model 1 is equal to the distance between the explosive 2 and the soil model 1. A photometric system 5 is installed on the inner top side of the explosion model box 3. The camera 5-1 of the photometric system 5 and the lighting lamp 5- 2. Align the soil model 1, complete the assembly of the explosion model box 3, transfer the assembled explosion model box 3 to the centrifugal box 8-4 of the geocentrifuge A counterweight box 8-3 is installed at one end to complete the assembly of the test device for measuring the dynamic elastic modulus of the soil model.

Step 3: Start the geotechnical centrifuge 8. After the geotechnical centrifuge 8 reaches an acceleration of 20g, start the wave speed tester 9. After the wave speed tester 9 works stably, detonate the explosive 2 through the measurement and control system 4. The wave speed tester 9 records the explosion wave from The change data of transverse and longitudinal wave velocity in the process of transferring the explosion center of explosive 2 to the placement position of soil model 1, the independent variable is time, and the camera 5-1 of the optical measurement system 5 shoots the soil model 1 during the explosion process. Video, the collected video of the explosion process is transmitted to the control computer 10 through the wireless transmitter 5-3 and the wireless receiver 5-4, and the purpose of transmitting the video of the explosion process to the control computer 10 is to observe and ensure the high-speed rotation of the centrifuge When the test in the centrifugal box 8-4 is carried out normally, the setting position of the equipment has not changed, and the test is valid.

Step 4: According to the relationship between the shear wave propagation velocity a _T and the longitudinal wave propagation wave velocity a _L in the infinite body of Hooke medium, the dynamic shear modulus G, dynamic elastic constant ν and dynamic elasticity of the solution soil model 1 can be obtained by inverse inference (1). Equation (2) for the modulus E. The shear wave velocity a _T and the longitudinal wave velocity a _L of the explosion wave when passing through the soil model 1 collected by the wave velocity tester 9, the values of the shear wave velocity a _T and the longitudinal wave velocity a _L are respectively substituted into formula (2), and the calculation can be done The dynamic shear modulus G, dynamic elastic constant ν and dynamic elastic modulus E of soil model 1 are obtained. Formulas (1) (2) are as follows:

Where: ρ is the density of soil model 1; λ is the Lame elastic constant, λ=2Gν/(1-2ν), ν is the dynamic elastic constant; G is the dynamic shear modulus; E is the dynamic elastic modulus.

Step 5: Repeat steps 1 to 4 several times to obtain several groups of parallel test groups. The specific embodiment of the present application adopts two groups of parallel test groups, and the dynamic elastic modulus E of the test data obtained by several groups of parallel test groups is averaged, As the final dynamic modulus value of soil model 1, then, taking the compaction times of soil model 1 as the abscissa, and the corresponding dynamic deformation modulus value of soil model 1 as the ordinate, draw a relationship diagram, and perform curve simulation. The corresponding relationship curve between the number of compactions and the value of the dynamic deformation modulus is obtained. The relationship curve has the meaning of simplifying the related test operations of other foundation models of the same type of soil. Only through the number of compactions, By substituting the relationship curve obtained from the above test, the corresponding soil dynamic deformation modulus value can be calculated.

Before step 2, the explosion model box 3 needs to be debugged and tested. The specific process is: take out the soil model 1, keep the positions of other devices unchanged, start the wave speed tester 9, and after the wave speed tester 9 works stably, pass the measurement and control system 4 The explosive 2 is detonated, and the wave velocity tester 9 tests the magnitude of the explosive wave when the explosive wave generated by the detonated explosive 2 is transmitted to the soil model 1; repeat the debugging test twice to ensure that the two explosion waves generated by the explosive 2 are in the soil. The transverse and longitudinal waves in the model 1 can be captured by the wave velocity tester 9, and the difference between the two wave strengths within the range of ±5% is regarded as qualified. Otherwise, adjust the usage amount of explosive 2 until the test conditions are met.

It should be noted that in this application, relational terms such as first, second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply these entities or operations There is no such actual relationship or order between them. Moreover, the terms "comprising", "comprising" or any other variation thereof are intended to encompass a non-exclusive inclusion such that a process, method, article or device that includes a list of elements includes not only those elements, but also includes not explicitly listed or other elements inherent to such a process, method, article or apparatus. Without further limitation, an element qualified by the phrase "comprising a..." does not preclude the presence of additional identical elements in a process, method, article or apparatus that includes the element.

Each embodiment in this specification is described in a related manner, and the same and similar parts between the various embodiments may be referred to each other, and each embodiment focuses on the differences from other embodiments.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in 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 body_TWith 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 body_LWith 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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