CN104596869A - Test method of four-dimensional dynamic quantitative analysis during soil shear failure - Google Patents

Abstract

The invention discloses a test method for four-dimensional dynamic quantitative analysis of soil shear failure. Firstly, based on two-dimensional optical testing technology, the two-dimensional plane dynamic change characteristics based on the time dimension during the soil shear process are obtained; the time interval set , based on the rotary table scanning technology, X-ray detectors are used to conduct Micro-CT tests on soil samples to obtain the static characteristics of the soil in three-dimensional space; to establish a light hole transmission registration model, and to integrate the two-dimensional optical data and the three-dimensional Micro-CT data into space Registration: According to the dynamic changes of the same marker points in the 2D optical data and the 3D Micro-CT data, the 2D plane change data is connected with the Micro-CT 3D space data through the spatial registration relationship to obtain the 3D soil space based on the time dimension Dynamic change characteristics, realize four-dimensional dynamic quantitative analysis test in the process of soil shear failure.

Description

Test Method for 4D Dynamic Quantitative Analysis of Soil Shear Failure

technical field

The invention relates to a test method for four-dimensional dynamic quantitative analysis of soil shear failure, which belongs to the technical field of indoor testing of civil engineering.

Background technique

The shear failure mechanism of soil has always been a hot topic of research by scholars at home and abroad. Many test methods for soil microstructure have been developed and introduced in my country, such as: mercury intrusion method, magnetic susceptibility method, scanning electron microscope analysis method (SEM), computer The development and introduction of these test methods, such as tomography analysis (CT) and microstructure optical test system (MOTS), provide a way for in-depth study of the shear failure mechanism of soil. However, there are deficiencies in the existing various soil microstructure test methods, and it is impossible to realize the four-dimensional dynamic quantitative test analysis. The development of the four-dimensional dynamic quantitative analysis test method will undoubtedly make the study of the soil failure mechanism a step further.

Although predecessors have carried out fruitful research on optical testing and CT testing, and achieved a lot of results, both methods are still insufficient due to the limitations of testing instruments, testing techniques and other factors:

(1) In terms of optical testing, the Microstructure Optical Testing System (MOTS) has great advantages in continuous tracking and quantitative observation of the microstructure of geotechnical materials. However, optical observation can only provide information on the part covered by light, so this method provides two-dimensional plane observation data (soil samples are semi-cylindrical), and fails to obtain soil three-dimensional fine structure information. It is obviously more advantageous to describe.

(2) In terms of CT testing, traditional CT testing machines (mostly borrowed from medical CT machines) have been gradually replaced by high-performance Micro-CT machines in obtaining three-dimensional information of the microstructure of soil materials. Even so, the current Micro-CT machine only scans the soil in a special state (such as before the test starts and after the test ends), and this test method still cannot continuously test the real change of the microstructure of rock and soil materials under load. (The same is true for other test methods, such as SEM method, etc.), so it is impossible to consider the actual displacement change information of micro-particles and pores of rock and soil materials from time to time. In fact, the deformation and failure of rock and soil materials under load is a process in which the primary structure is gradually destroyed and the secondary structure is gradually formed. The law of change under the stress state must have its limitations, and it can only stay in qualitative and logical analysis.

Contents of the invention

The technical problem to be solved by the present invention is to provide a test method for four-dimensional dynamic quantitative analysis of soil shear failure, which is based on two-dimensional optical testing technology and Micro-CT three-dimensional testing technology, and is a A test method for dynamic quantitative analysis of four dimensions (three dimensions in space and time dimension) in the process.

The present invention adopts the following technical solutions to solve the above-mentioned technical problems

The invention provides a test method for four-dimensional dynamic quantitative analysis of soil shear failure, comprising the following specific steps:

Step 1. During the soil loading and shearing process, based on the two-dimensional optical testing technology, the time-based two-dimensional plane dynamic change characteristics of the soil are obtained;

Step 2. During the loading and shearing process of the soil, the loading is suspended according to the set time interval, and based on the rotary table scanning technology, the X-ray detector is used to perform the Micro-CT test on the soil to obtain the three-dimensional static characteristics of the soil;

Step 3: Immediately after the Micro-CT test, continue to load, and continue to carry out two-dimensional optical test synchronously to obtain the two-dimensional dynamic change characteristics of the soil based on the time dimension;

Step 4, according to steps 1 to 3, alternately conduct two-dimensional optical testing and Micro-CT testing until the soil shear failure;

Step 5, establish a light hole transmission registration model, and perform spatial registration on the obtained two-dimensional plane dynamic change features based on the time dimension and the three-dimensional space static features, and according to the dynamic changes of the same marker points between the two, the time-dimension-based The two-dimensional plane dynamic change features of the two-dimensional plane are connected with the three-dimensional space static features through the spatial registration relationship, so that the two-dimensional plane dynamic change features based on the time dimension are integrated with the three-dimensional space static features, and the three-dimensional space dynamic change features of the soil based on the time dimension are obtained. In this way, the four-dimensional dynamic quantitative analysis test in the process of soil shear failure can be realized.

As a further optimization scheme of the present invention, in step 1, based on the two-dimensional optical testing technology, the dynamic change characteristics of the two-dimensional plane based on the time dimension during the soil shearing process are obtained, specifically: using a long-distance microscope CCD optical camera with high magnification , equipped with a high-resolution digital image acquisition system, synchronously and continuously taking pictures during the shearing process of the soil, so as to obtain the dynamic change characteristics of the two-dimensional plane based on the time dimension.

As a further optimization solution of the present invention, the magnification of the above-mentioned high-magnification long-distance microscope CCD optical camera head is 20-500 times.

As a further optimization scheme of the present invention, the X-ray detector in step 2 is a C7942CA-02 CMOS-based flat panel detector from Hamamatsu, Japan.

As a further optimization scheme of the present invention, the transfer table scanning technology in step 2 is specifically: use an electronically controlled rotary table to complete the rotation function, and use x-dimensional, y-dimensional, and z-dimensional electronically controlled translation tables to realize the three-dimensional spatial position of the scanned soil. Adjustment.

Compared with the prior art by adopting the above technical scheme, the present invention has the following technical effects: the present invention is based on two-dimensional optical testing technology and Micro-CT three-dimensional testing technology, and the acquired two-dimensional optical data based on time dimension (time dimension, space Two-dimensional) and Micro-CT three-dimensional data (spatial three-dimensional) for spatial registration, docking, and fusion to obtain the three-dimensional dynamic change characteristics of soil based on the time dimension, and realize the four-dimensional (spatial three-dimensional, time-dimensional ) dynamic quantitative analysis test.

Description of drawings

Fig. 1 is a flow chart of the method of the present invention.

Fig. 2 is a top view of the four-dimensional dynamic testing device of the present invention.

Among them: 1-Micro-CT ray source; 2-semi-cylindrical soil sample; 3-central rotary control platform; 4-x-dimensional controller; 5-y-dimensional controller; 6-X-ray; 7-Y-ray flat panel detector ; 8-CCD camera; 9-protective lead plate; 10-CCD plane.

Fig. 3 is a schematic diagram of the joint coordinate system of the two-dimensional optical test and the joint coordinate system of the Micro-CT three-dimensional test.

Detailed ways

Below in conjunction with accompanying drawing, technical scheme of the present invention is described in further detail:

FIG. 1 is a flow chart of the method of the present invention, which has been described in detail in the content of the invention above, and will not be repeated here.

The technical scheme of the present invention is further elaborated below in conjunction with specific embodiment:

First, as shown in Figure 2, the test device was constructed and a semi-cylindrical soil sample was prepared.

Secondly, in the process of loading and shearing, based on the two-dimensional optical testing technology, the dynamic change characteristics of the two-dimensional plane based on the time dimension during the soil shearing process are obtained.

Thirdly, during the soil loading and shearing process, according to the set time, such as time t ₁ , the loading is suspended, and the Micro-CT is started immediately. Based on the rotary table scanning technology, the X-ray detector is used to perform Micro-CT rotary scanning of the soil sample test;

Again, continue loading immediately after the Micro-CT scans the soil sample in rotation (record the time consumption as t _c1 ), and perform optical observations synchronously during the loading process. After loading to the set time t ₂ , stop loading, and then continue Micro-CT test, so repeated until the end of the test;

Thirdly, construct the optical hole transmission registration model, establish the joint coordinate system of the two-dimensional optical test coordinate system and the three-dimensional Micro-CT test, and perform spatial registration based on the dynamic change characteristics of the two-dimensional plane based on the time dimension and the obtained three-dimensional space static features , that is, in the process of data processing, according to the dynamic changes of the same marker points in the 2D optical image and the 3D Micro-CT data, the optical measurement changes are corresponding to the 3D Micro-CT data through the spatial registration relationship, so as to realize the optical data (spatial 2D dimensional, time dimensional) and Micro-CT data (spatial 3D) fusion to realize the 4D dynamic quantitative analysis test in the process of soil shear failure.

The constructed light hole transmission registration model and the spatial registration process are as follows:

(1) The coordinate system of the two-dimensional optical test and the joint coordinate system of the Micro-CT three-dimensional test are shown in Figure 3. Among them, the coordinate system of the two-dimensional optical test is M-xyz, the coordinate system of the Micro-CT three-dimensional test is O-xyz, and the two share the y-axis;

(2) Construct a light hole transmission registration model to model the optical CCD camera, as shown in Figure 3. In this model, the CCD lens is equivalent to the optical center M, the plane where the CCD is located is called the image plane EFGH, and the center of the image plane EFGH intersects the y-axis at point N, and the plane where the soil sample is located when the focus is clear is called the focal plane ABCD;

(3) For a registration point P on the soil sample surface, its spatial position can be determined by Micro-CT data, that is, the Micro-CT coordinate value of its spatial position is known, expressed as (x _CT , y _CT , z _CT ), the visible light transmitted from this point is mapped to the P' point of the CCD through the optical center of the lens, and the point P corresponds to the point P' one by one;

(4) Since the optical/Micro-CT fusion system is installed on the same standard optical platform, the three translations and three rotations describing the relationship between the two coordinate systems (M-xyz, O-xyz) can be Omit two translations and three rotations, and only consider the translation about the y-axis;

(5) The coordinate value of the Micro-CT coordinate origin O in the optical coordinate system is (c _x , _cy , c _z ), then the three-dimensional coordinates of the registration point P in the optical coordinate system are ${[x_t,{\mathrm{the\; y}}_t,z_t]}^T=\left[\begin{array}{cccc}1& 0& 0& c_x\\ 0& 1& 0& c_{\mathrm{the\; y}}\\ 0& 0& 1& c_z\end{array}\right]\left[\begin{array}{c}{x}_{\mathrm{CT}}\\ {\mathrm{the\; y}}_{\mathrm{CT}}\\ z_{\mathrm{CT}}\\ 1\end{array}\right];$

(6) The point P and the point P' are symmetrical about the optical center M, record is l ₁ , is l ₂ , then the coordinates of P' are: ${[x_t^{,},{\mathrm{the\; y}}_t^{,},z_t^{,}]}^T=-\frac{l_1}{l_2}\left[\begin{array}{cccc}1& 0& 0& c_x\\ 0& 1& 0& c_{\mathrm{the\; y}}\\ 0& 0& 1& c_z\end{array}\right]\left[\begin{array}{c}{x}_{\mathrm{CT}}\\ {\mathrm{the\; y}}_{\mathrm{CT}}\\ z_{\mathrm{CT}}\\ 1\end{array}\right];$

(7) For the optical coordinate system M-xyz, the coordinates of the registration point P are (x _M , y _M , z _M ), and for several registration points, construct an error function: $\mathrm{\Φ}=\frac{1}{\mathrm{no}}\underset{i=1}{\overset{\mathrm{no}}{\mathrm{\Σ}}}[{({x_m}^{\left(i\right)}-{x_t^{,}}^{\left(i\right)})}^2+{({{\mathrm{the\; y}}_m}^{\left(i\right)}-{{\mathrm{the\; y}}_t^{,}}^{\left(i\right)})}^2+{({z_m}^{\left(i\right)}-{z_t^{,}}^{\left(i\right)})}^2],$ Wherein, i=1...n is the number of registration points.

(8) Use an optimization or search method to find (c _x , _cy , c _z ) that minimizes the error function Φ.

Finally, through the Micro-CT test, the three-dimensional coordinates of a point inside the soil can be obtained as: (x _CT , y _CT , z _CT ), and the three-dimensional coordinates of the optical coordinate system obtained through registration are: ${[x_t,{\mathrm{the\; y}}_t,z_t]}^T=\left[\begin{array}{cccc}1& 0& 0& c_x\\ 0& 1& 0& c_{\mathrm{the\; y}}\\ 0& 0& 1& c_z\end{array}\right]\left[\begin{array}{c}{x}_{\mathrm{CT}}\\ {\mathrm{the\; y}}_{\mathrm{CT}}\\ z_{\mathrm{CT}}\\ 1\end{array}\right];$ Adding the time factor of the optical test, the displacement field of the soil shear four-dimensional test is expressed as: ${[x_t,{\mathrm{the\; y}}_t,z_t,t]}^T=\left[\begin{array}{cccc}1& 0& 0& c_x\\ 0& 1& 0& c_{\mathrm{the\; y}}\\ 0& 0& 1& c_z\\ 0& 0& 0& t\end{array}\right]\left[\begin{array}{c}{x}_{\mathrm{CT}}\\ {\mathrm{the\; y}}_{\mathrm{CT}}\\ z_{\mathrm{CT}}\\ 1\end{array}\right].$

The above is only a specific implementation mode in the present invention, but the scope of protection of the present invention is not limited thereto. Anyone familiar with the technology can understand the conceivable transformation or replacement within the technical scope disclosed in the present invention. All should be covered within the scope of the present invention, therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (5)

1. The test method of four-dimensional dynamic quantitative analysis of soil shear failure is characterized in that, comprising the following specific steps: Step 1. During the soil loading and shearing process, based on the two-dimensional optical testing technology, the time-based two-dimensional plane dynamic change characteristics of the soil are obtained; Step 2. During the loading and shearing process of the soil, the loading is suspended according to the set time interval, and based on the rotary table scanning technology, the X-ray detector is used to perform the Micro-CT test on the soil to obtain the three-dimensional static characteristics of the soil; Step 3: Immediately after the Micro-CT test, continue to load, and continue to carry out two-dimensional optical test synchronously to obtain the two-dimensional dynamic change characteristics of the soil based on the time dimension; Step 4, according to steps 1 to 3, alternately conduct two-dimensional optical testing and Micro-CT testing until the soil shear failure; Step 5: Establish a light hole transmission registration model, and perform spatial registration on the obtained two-dimensional plane dynamic change features based on the time dimension and the three-dimensional space static features. The two-dimensional plane dynamic change features of the two-dimensional plane are connected with the three-dimensional space static features through the spatial registration relationship, so that the two-dimensional plane dynamic change features based on the time dimension and the three-dimensional space static features are fused, and the three-dimensional space dynamic change features of the soil based on the time dimension are obtained. In this way, the four-dimensional dynamic quantitative analysis test in the process of soil shear failure can be realized. 2. the test method of four-dimensional dynamic quantitative analysis of soil shear damage according to claim 1, is characterized in that, in step 1, based on two-dimensional optical testing technology, obtains the two-dimensional plane based on time dimension in the process of soil mass shearing The characteristics of dynamic changes, specifically: using a high-magnification long-distance microscope CCD optical camera, coupled with a high-resolution digital image acquisition system, synchronously and continuously taking photos during the soil shearing process, so as to obtain a two-dimensional image based on the time dimension Plane dynamic change feature. 3. the test method of four-dimensional dynamic quantitative analysis of soil shear failure according to claim 2, characterized in that the magnification of the long-distance microscope CCD optical camera with high magnification is 20 to 500 times. 4. the test method of four-dimensional dynamic quantitative analysis of soil shear failure according to claim 1, is characterized in that, in step 2, X-ray detector is the CMOS-based flat panel detector of C7942CA-02 of Hamamatsu, Japan. 5. The test method for four-dimensional dynamic quantitative analysis of soil shear failure according to claim 1, characterized in that, the step 2 transfer table scanning technology is specifically: use an electronically controlled rotary table to complete the rotation function, and use the x dimension, y Dimensional and z-dimension electronically controlled translation platforms realize the adjustment of the three-dimensional spatial position of the scanned soil.