A test device and test process for observing particle movement during sand liquefaction

Abstract

The present invention discloses an experimental device and an experimental process for observing the movement of particles in the sand liquefaction process, including a seismic isolation bracket, a model box slidably connected to the top of the seismic isolation bracket, a servo system installed on one side of the model box along the sliding direction, an acceleration sensor installed on the other side, a plurality of laser transmitters are arranged in front of the acceleration sensor, the laser transmitter is coaxially installed with the servo system, a camera is arranged in a direction perpendicular to the sliding direction, the camera is placed directly behind the light plane, an image correction point is also installed on the side of the model box, and a light intensity monitor is installed on the inner wall of the model box. The present invention uses a high-speed camera to intuitively record the reaction of the sand in the test, can accurately locate the position of the particles, describe the movement of the particles in the test process, and by iteratively processing the image, can determine the position of the particles at each moment, which is convenient for studying the movement process and results of the particles in the sand dynamic load liquefaction process.

Description

Technical Field

[0001] The invention relates to a test device and a test process for particle flow, and in particular to a test device and a test process for observing particle movement in a sand liquefaction process. Background Art

[0002] Sand liquefaction is a sudden geological disaster caused by earthquake activity. Once it occurs, it will pose a great threat to the safety of the city. Shallow sand layers are widely distributed in the Yangtze River Delta region. Under the influence of earthquake activity, earthquake liquefaction, a typical disaster phenomenon, is prone to occur, which poses a great hidden danger to urban safety. It is of great significance to study sand liquefaction.

[0003] At present, the research on sand liquefaction characteristics mainly adopts dynamic triaxial test, which can directly obtain state parameters such as soil stress and pore water pressure, and thus indirectly observe the liquefaction process of soil through resistivity. However, there is no direct and specific method for the migration and movement state of sand particles during liquefaction.

[0004] Prior to this invention, patent number: 201810667497.0 used transparent soil to simulate underwater caisson construction and observe soil displacement; patent number: 202121441087.8 used transparent soil to study the influence of underground retaining wall structure on groundwater seepage. It can be seen from the above related equipment that the existing transparent soil equipment is mainly used to study the static problems of soil displacement field and seepage, and cannot simulate the mechanical properties of soil under vibration conditions. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a test device and test process for studying the particle flow in the sand liquefaction process which has a simple structure, is easy to operate and convenient to observe, so as to facilitate the observation of the liquefaction reaction process of the sand and the movement process of the sand particles.

[0006] Technical solution: The present invention includes a seismic isolation bracket, the top of which is slidably connected to a model box, a servo system is installed on one side of the model box along its sliding direction, and an acceleration sensor is installed on the other side, a plurality of laser transmitters are arranged in front of the acceleration sensor, the laser transmitter is coaxially installed with the servo system, a camera is arranged in a direction perpendicular to the sliding direction, the camera is placed directly behind the light plane, image correction points are also installed on the side of the model box, and a light intensity monitor is installed on the inner wall of the model box.

[0007] The servo system comprises a hydraulic system, and the hydraulic system is connected to the shear column through a nut rod.

[0008] The laser transmitter irradiates the sample in the vibration direction provided by the hydraulic system, and can form light planes of different colors in the model box and the sand.

[0009] The light intensity monitor is capable of monitoring the light intensity at different heights of each light plane.

[0010] The picture correction point performs correction processing on the picture and then performs iterative processing.

[0011] The iterative processing is described using the i-th vertical section of the light plane, and specifically includes the following steps:

[0012] Step 1: Partition the light planes of different parts and number them from top to bottom. i Planes, numbered from top to bottom are a i1 , a i2 , a i3 , a i4 , a i5 , a i6 , a i7 , a i8 , a i9 , the same numbering method is used for planes b and c;

[0013] Step 2: For image A, we can first get a i6 、a i7 、a i8 with a i9 For the B image, we can first get a i1 、a i2 、a i3 with a i4 The situation at height is taken as the initial condition;

[0014] Step 3: Establish a multivariate linear equation based on the a, b, c plane partitions:

[0015] For image A, we have:

[0016] a i1 +b i1 +c i1 =x i1

[0017]

[0018]

[0019] a i4 +b i6 =x i4

[0020] a i5 +b i7 =x i5

[0021] For B-pictures:

[0022] a i9 +b i7 +c i3 =y i1

[0023]

[0024]

[0025] a i6 +b i2 =y i4

[0026] a i5 +b i1 =y i5

[0027] In the formula, a ij ——Light intensity of the jth subarea of ​​light plane a on the i-th vertical section (j=1-9); b ij ——Light intensity of the jth subarea of ​​light plane b on the ith vertical section (j=1-7); c ij ——Light intensity of the jth subarea of ​​light plane c on the i-th vertical section (j=1-3); x ij ——The light intensity of the jth subarea of ​​the image captured by camera A on the i-th vertical section (j=1-5); y ij ——The light intensity of the jth subarea of ​​the image captured by camera B on the i-th vertical section (j=1-5);

[0028] In the above 10 equations, the known quantity is a i1 、a i2 、a i3 、a i4 、a i6 、a i7 、a i8 、a i9 、x ij ,y ij ; The unknown quantity is a i5 、b i1 、b i2 、b i3 、b i4 、b i5 、b i6 、b i7 、c i1 、c i2 、c i3 ;

[0029] Step 4: For the entire plane, the following equations can be added, which are the total light intensity of the corresponding light plane corresponding to each unknown quantity and corresponding height:

[0030]

[0031]

[0032]

[0033] In the formula, a i5 (i=1~n)——light intensity of the 5th subarea of ​​light plane a on the ith vertical section; b ij (i=1~n)——light intensity of the jth subarea of ​​the light plane b on the i-th vertical section; c ij (i=1~n)——light intensity of the jth subarea of ​​light plane c on the ith vertical section; a5——total light intensity of the 5th subarea of ​​light plane a monitored by the light intensity monitor; b j ——The total light intensity of the jth subarea of ​​the light plane b monitored by the light intensity monitor (j=1-7); c j ——The total light intensity of the jth subarea of ​​the light plane c monitored by the light intensity monitor (j=1-3);

[0034] When the light intensity of each partition is to be determined, the number of vertical sections n that satisfy the light plane is less than the unknown number of partitions on a single section.

[0035] The seismic isolation bracket comprises a workbench, a rigid plate is slidably connected to the top of the workbench, a plurality of dampers are connected between the rigid plate and the workbench, a track is arranged on the rigid plate, and a model box is slidably connected to the track.

[0036] An experimental process for studying particle flow during sand liquefaction comprises the following steps:

[0037] Step 1: Assemble the seismic isolation bracket;

[0038] Step 2, preparing transparent sand;

[0039] Step 3, fix the model box containing the sample on the track, and connect the servo system to the model box;

[0040] Step 4: Place the laser transmitter on the axis of the nut rod, turn on the laser transmitter and calibrate it so that the laser and the nut rod are on the same axis;

[0041] Step 5: Place the camera directly behind the light plane and install the acceleration sensor;

[0042] Step 6: Before the test begins, turn on the camera recorder, accelerometer and light intensity monitor for debugging, and prepare to record the test data and sample conditions;

[0043] Step 7: During the test, detailed load information is input into the hydraulic system through a computer program, and the changes of the light plane in the transparent sand are recorded by a camera throughout the process;

[0044] Step 8. After the test, the recorded images should be processed by software to reproduce the particle movement during the sand liquefaction process.

[0045] Beneficial effects: The present invention uses a high-speed camera to intuitively record the reaction of sand in the test, can accurately locate the position of particles, describe the movement of particles in the test process, and through iterative processing of images, can determine the position of particles at each moment, which is convenient for studying the movement process and results of particles in the dynamic load liquefaction process of sand; the adopted seismic isolation bracket can reduce the vibration impact on the work surface and the ground, and correspondingly reduce the jitter impact during the shooting process of the high-speed camera, and the work surface and the rigid plate have redundant damper connection holes, which can increase or decrease the damper according to the size of the applied dynamic load to provide appropriate damping for the seismic isolation bracket, and an acceleration sensor is set in the transparent model box for the test to accurately receive the dynamic load applied to the sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 The overall structure of the present invention is shown in FIG. Figure 1 ;

[0047] Figure 2 The overall structure of the present invention is shown in FIG. Figure 2 ;

[0048] Figure 3 is the light intensity distribution on the i-th vertical section of the present invention. DETAILED DESCRIPTION

[0049] The present invention will be further described below in conjunction with the accompanying drawings.

[0050] like Figure 1 and Figure 2As shown, the present invention includes a seismic isolation bracket, and a model box 6 is slidably connected to the top of the seismic isolation bracket. The model box 6 adopts a transparent box body, and sand is placed in it. A hydraulic system 8 is installed on one side of the model box 6 along its sliding direction, and an acceleration sensor 12 is installed on the other side. The acceleration sensor 12 can record the acceleration of the whole process, and can correctly receive the acceleration received by the transparent model box, which has a positive effect on the correct analysis of the test phenomenon. The hydraulic system 8 is connected to the shear column 9 through the nut rod 7. A plurality of laser emitters 10 of different colors are arranged in front of the acceleration sensor 12. The laser emitter 10 is coaxially installed with the nut rod 7. A camera 11 is arranged in a direction perpendicular to the sliding direction. The camera 11 is placed directly behind the light plane. A picture correction point 13 is also installed on the side of the model box 6 close to the camera 11. The picture recorded by the camera 11 can be corrected by the picture correction point 13. A dynamic load is applied to the model box 6 through the hydraulic system 8, so that the transparent model box moves together with the saturated transparent sand in it.

[0051] Multiple laser emitters 10 of different colors emit lasers to form multiple light planes in the transparent sand. The laser emitters 10 irradiate the sample in the vibration direction provided by the hydraulic system 8, and can form stable and observable light planes of different colors in the transparent model box and the transparent sand. The camera 11 can panoramically record the bright spot images of different light planes of the transparent sand under the action of dynamic load, and after processing, the particle flow process can be described in the software. A light intensity monitor 14 is also installed on the inner wall of the model box 6. The light intensity monitor 14 monitors the light intensity at different heights of each light plane, and the test results are recorded by the camera 11, the acceleration sensor 12 and the light intensity monitor 14. The image is corrected by the image correction point 13 and then iteratively processed. During the test, the dynamic response of transparent sand under dynamic load is studied, and the camera 11 is used to collect images of the whole process. The captured pictures are corrected by software through the picture correction point 13. By iteratively processing the pictures, the positions of particles at each moment can be determined, which is convenient for studying the movement process and results of particles in the process of liquefaction of sand under dynamic load. It has real-time and visibility, is convenient for indoor tests, and the test factors are easy to control.

[0052] The seismic isolation bracket includes a workbench 1, a rigid plate 4 is slidably connected to the top of the workbench 1, a plurality of dampers 2 are connected between the rigid plate 4 and the workbench 1, a track 5 is provided on the rigid plate 4, and a model box 6 is slidably connected to the track 5. The seismic isolation bracket can reduce the vibration impact on the workbench and the ground during the test, and correspondingly reduce the jitter during the high-speed camera shooting process, and reduce the difficulty of image correction. In addition, there are redundant damper connection holes between the workbench and the rigid plate, and the dampers (at least 4) can be added or reduced according to the size of the applied dynamic load to provide appropriate damping for the seismic isolation bracket.

[0053] The present invention uses the captured images and the data obtained by the light intensity monitor 14 to perform an iterative solution to obtain a particle bright spot diagram on a light plane of different colors. According to the brightness of the particles, the position of the particles at a certain moment can be determined. By tracking the brightness of the particles at different moments, the particle flow change process during the vibration process can be observed. The process of plane separation iteration of the particle bright spot is as follows: To facilitate the explanation of the iterative process, the i-th vertical section of the light plane is temporarily taken for explanation, as shown in FIG. Figure 3 As shown in the figure, the light planes of different parts are divided into zones and numbered from top to bottom according to each light plane. For example, for a i Planes, numbered from top to bottom are a i1 , a i2 , a i3 , a i4 , a i5 , a i6 , a i7 , a i8 , a i9 , the same numbering method is used for planes b and c. First, for image A, we can first get a i6 、a i7 、a i8 with a i9 In the case of height, for the B image, we can first get a i1 、a i2 、a i3 with a i4 The situation at height is taken as the initial condition.

[0054] Establish a multivariate linear equation based on the a, b, and c plane partitions.

[0055] For image A, we have:

[0056] a i1 +b i1 +c i1 =x i1

[0057]

[0058]

[0059] a i4 +b i6 =x i4

[0060] a i5 +b i7 =x i5

[0061] For B pictures, there are:

[0062] a i9 +b i7 +c i3 =y i1

[0063]

[0064]

[0065] a i6 +b i2 =y i4

[0066] a i5 +b i1 =y i5

[0067] In the formula, a ij ——Light intensity of the jth subarea of ​​light plane a on the ith vertical section (j=1-9);

[0068] b ij ——Light intensity of the jth subarea of ​​light plane b on the ith vertical section (j=1-7);

[0069] c ij ——Light intensity of the jth subarea of ​​the light plane c on the ith vertical section (j=1-3);

[0070] x ij ——The light intensity of the jth subarea of ​​the image captured by camera A on the i-th vertical section (j=1-5);

[0071] y ij ——The light intensity of the jth subarea of ​​the image captured by camera B on the i-th vertical section (j=1-5);

[0072] In the above 10 equations, the known quantity is a i1 、a i2 、a i3 、a i4 、a i6 、a i7 、a i8 、a i9 、x ij ,y ij ; The unknown quantity is a i5 、b i1 、b i2 、b i3 、b i4 、b i5 、b i6 、b i7 、c i1 、c i2 、ci3 There are 11 in total.

[0073] There are 10 equations above, but there are 11 unknowns, which cannot be solved for the time being. Therefore, the data collected by the light intensity monitor 14 is needed. For the entire plane, 11 useful equations can be added, which are the total light intensity of the corresponding light plane corresponding to each unknown quantity and corresponding height:

[0074]

[0075]

[0076]

[0077] In the formula, a i5 (i=1~n)——light intensity of the 5th subarea of ​​light plane a on the ith vertical section;

[0078] b ij (i=1~n)——light intensity of the jth subarea of ​​light plane b on the i-th vertical section;

[0079] c ij (i=1~n)——light intensity of the jth subarea of ​​light plane c on the i-th vertical section;

[0080] a5——the total light intensity of the fifth subarea of ​​light plane a monitored by the light intensity monitor;

[0081] b j ——The total light intensity of the jth subarea of ​​the light plane b monitored by the light intensity monitor (j=1-7);

[0082] c j ——The total light intensity of the jth subarea of ​​the light plane c monitored by the light intensity monitor (j=1-3);

[0083] In this way, there are 10n+11 equations and 11n unknowns for the system. If the equations are to be solved, 10n+11>11n must be satisfied, that is, n<11.

[0084] From the above analysis, it can be seen that when determining the light intensity of each partition, the number of vertical sections n of the light plane must be less than the number of unknown partitions on a single section, so that the light intensity of the unknown partition can be solved.

[0085] The test process of the present invention comprises the following steps:

[0086] Step 1: Connect the damper 2 and the rigid plate 4 welded with the model box track on the workbench 1 with screws;

[0087] Step 2, prepare transparent sandy soil: wash and dry the fused quartz sand used for the test to remove impurities and moisture; mix No. 15 white mineral oil and n-dodecane at a volume ratio of approximately 7:1, and adjust to a refractive index of 1.459; pour a sufficient amount of the mixed liquid into the model box, and use the underwater sand rain method to place the fused quartz sand into the liquid; use a glass rod to slowly stir the transparent soil to minimize the bubbles in it, but not completely eliminate them; use the layered compaction method to make the transparent soil reach a medium density, and configure it layer by layer; let the transparent soil stand, and add pressure weights to consolidate it for a period of time;

[0088] Step 3: Fix the transparent model box containing the prepared specimen on the model box track and ensure that the transparent model box can be easily moved along the track direction. Connect the shear column to the transparent model box through the nut rod of the hydraulic system, and check that the nut rod and the model box track are on the same axis in the vertical plane;

[0089] Step 4: Place the laser transmitter on the axis of the nut rod, turn on the laser transmitter for calibration, so that the laser and the nut rod are on the same axis and the light plane can be clearly observed from the front and top surfaces in the transparent sand;

[0090] Step 5: Place the camera directly behind the light plane and install the acceleration sensor;

[0091] Step 6: Before the test begins, turn on the camera recorder, accelerometer and light intensity monitor for debugging, and prepare to record the test data and sample conditions;

[0092] Step 7: During the test, detailed load information is input into the hydraulic system through a computer program, and the changes of the light plane in the transparent sand are recorded by a camera throughout the process;

[0093] Step 8. After the test, the recorded images should be processed by software to reproduce the particle movement during the sand liquefaction process.

Claims

1. A test device for observing particle movement during sand liquefaction, characterized in that: The invention comprises a seismic isolation bracket, wherein a model box (6) is slidably connected to the top of the seismic isolation bracket, a servo system is installed on one side of the model box along the sliding direction, and an acceleration sensor (12) is installed on the other side, a plurality of laser transmitters (10) are arranged in front of the acceleration sensor (12), the laser transmitter (10) is coaxially installed with the servo system, a camera (11) is arranged in a direction perpendicular to the sliding direction, and the camera is placed directly behind the light plane, an image correction point (13) is also installed on the side of the model box, and a light intensity monitor (14) is installed on the inner wall of the model box, the image correction point (13) performs correction processing on the image and then performs iterative processing, and the iterative processing process is described with the i-th vertical section of the light plane, and specifically comprises the following steps: Step 1: Partition the light planes of different parts and number them from top to bottom. i Planes, numbered from top to bottom are a i1 , a i2 , a i3 , a i4 , a i5 , a i6 , a i7 , a i8 , a i9 , the same numbering method is used for planes b and c; Step 2: For image A, first get a i6 、a i7 、a i8 with a i9 In the case of height, for the B image, first get a i1 、a i2 、a i3 with a i4 The situation at height is taken as the initial condition; Step 3: Establish a multivariate linear equation based on the a, b, c plane partitions: For image A, we have: a i1 +b i1 +c i1 =x i1 a i4 +b i6 =x i4 a i5 +b i7 =x i5 For B-pictures: a i9 +b i7 +c i3 =y i1 to i6 +b i2 =and i4 to i5 +b i1 =and i5 In the formula, a ij ——Light intensity of the jth subarea of ​​light plane a on the i-th vertical section, j = 1 to 9; b ij ——Light intensity of the jth subarea of ​​light plane b on the i-th vertical section, j = 1 to 7; c ij ——Light intensity of the jth subarea of ​​light plane c on the i-th vertical section, j = 1 to 3; x ij ——The light intensity of the jth subarea of ​​the image captured by camera A on the i-th vertical section, j = 1 to 5; y ij ——The light intensity of the jth subarea of ​​the image captured by camera B on the i-th vertical section, j = 1 to 5; In the above 10 equations, the known quantity is a i1 、a i2 、a i3 、a i4 、a i6 、a i7 、a i8 、a i9 、x ij ,y ij ; The unknown quantity is a i5 、b i1 、b i2 、b i3 、b i4 、b i5 、b i6 、b i7 、c i1 、c i2 、c i3 ; Step 4: For the entire plane, the following equations can be added, which are the total light intensity of the corresponding light plane corresponding to each unknown quantity and corresponding height: In the formula, a i5 , i = 1 ~ n, - the light intensity of the 5th subarea of ​​the light plane a on the ith vertical section; b ij， i = 1 to n, —— the light intensity of the jth subarea of ​​the light plane b on the ith vertical section; c ij , i = 1 ~ n, - the light intensity of the jth subarea of ​​the light plane c on the ith vertical section; a5 - the total light intensity of the 5th subarea of ​​the light plane a monitored by the light intensity monitor; b j ——The total light intensity of the jth subarea of ​​the light plane b monitored by the light intensity monitor, j = 1 to 7; c j ——The total light intensity of the jth subarea of ​​the light plane c monitored by the light intensity monitor, j = 1 to 3; When the light intensity of each partition is to be determined, the number n of vertical sections that satisfy the light plane is less than the unknown number of partitions on a single section.

2. The test device for observing particle movement during sand liquefaction according to claim 1, characterized in that: The servo system comprises a hydraulic system (8), and the hydraulic system is connected to a shear column (9) via a nut rod (7).

3. The test device for observing particle movement during sand liquefaction according to claim 1, characterized in that: The laser emitter (10) irradiates the sample in the vibration direction provided by the hydraulic system (8), and can form light planes of different colors in the model box and the sand.

4. The test device for observing particle movement during sand liquefaction according to claim 1, characterized in that: The light intensity monitor (14) is capable of monitoring the light intensity at different heights of each light plane.

5. The test device for observing particle movement during sand liquefaction according to claim 1, characterized in that: The seismic isolation bracket comprises a workbench (1), a rigid plate (4) is slidably connected to the top of the workbench, a plurality of dampers (2) are connected between the rigid plate and the workbench, a track (5) is provided on the rigid plate, and a model box (6) is slidably connected to the track.

6. The test process of the test device for observing particle movement during sand liquefaction according to any one of claims 1 to 5 is characterized in that: The following steps are involved: Step 1: Assemble the seismic isolation bracket; Step 2: preparing transparent sand; Step 3: fix the model box containing the sample on the track, and connect the servo system to the model box; Step 4: Place the laser transmitter on the axis of the nut rod, turn on the laser transmitter and calibrate it so that the laser and the nut rod are on the same axis; Step 5: Place the camera directly behind the light plane and install the acceleration sensor; Step 6: Before the test begins, turn on the camera recorder, accelerometer and light intensity monitor for debugging, and prepare to record the test data and sample conditions; Step 7: During the test, detailed load information is input into the hydraulic system through a computer program, and the changes of the light plane in the transparent sand are recorded by a camera throughout the process; Step 8. After the test, the recorded images should be processed by software to reproduce the particle movement during the sand liquefaction process.

Images