| It is difficult to obtain the gradual change of the surface morphology of rock discontinuities during direct shear test.In order to solve the problems that it is difficult to fabricate the rock structure interview samples with the same surface morphology characteristics with high accuracy and that the shear process of the structure surface morphology can not be obtained during the test process.In this paper,the transparent structure interview samples with high similarity to the original rock morphology are made by using three-dimensional laser scanner and three-dimensional printing technology,based on this,a visualized test method for the whole process of structural plane shearing is put forward.The main achievements of this paper are as follows:(1)The point cloud data on the surface of the structural plane are obtained by using a three-dimensional laser scanner without touching the rock surface,and then the virtual three-dimensional model is generated by software and printed in three-dimensional.Through the analysis of the existing research,the uniaxial compression tests of printing materials at room temperature and low temperature were carried out.Combined with the purpose of this test,it was shown that the transparent photosensitive resin(veroclear)samples modified by cryogenic brittleness basically met the test requirements.Finally,the 3D comparison test between the original rock structure plane and the printed structure plane is carried out by the best fitting method,which proves the accuracy and reliability of the fabrication method.(2)Due to the arrangement of the experimental device and other reasons,the camera must form a certain angle with the orientation of the structural plane,and refraction will inevitably occur when shooting.In order to minimize the influence of refraction,the edge lengths of structural planes of normal tilted and penetrating tilted images at different angles are measured and analyzed.The refraction model of transparent sample is established according to the principle of dual-media photography and underwater imaging.The relationship between the corresponding edge length of the structural plane of the normal tilted image and the tilted image is obtained.Finally,considering the various influencing factors,the optimal shooting angle is selected.(3)A visual monitoring method is designed to study the structural changes of the whole process.According to the idea of differential and image scale conversion,a method of tracing and restoring the changing area of structural plane is proposed.According to the tracing and restoring method,the shearing area of structural plane at a certain time is located on the original structural plane image.Based on the statistical measurement of irregular area of rock structural plane and the quantitative processing of image,an accurate description method of structural plane change during the wholetest process is proposed.(4)The whole process visualization method is used to carry out shear test and a simple analysis is made to verify the feasibility of the visualization test method.Through tracing and restoring images at different times,it is found that the points on the structural plane are not more easily destroyed,but relatively higher points on the surface of the structural plane and are easily destroyed in the direction of shearing in the positive direction.Accumulative shear area variation of structural plane under different displacements,It is found that the expansion of shear area of structural plane mainly concentrates on the stage of gradual decrease of post-peak shear stress,and it can clearly know the location of structural plane failure and the specific extent of failure in different areas under different displacements. |
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