Research On Deformation Characteristics Of Triaxial Soil Samples Based On Image Measurement

Geotechnical triaxial test is an important method to test the strength and stressstrain characteristics of soil.Due to the influence of end constraint and end contact problems,conventional geotechnical triaxial test cannot accurately reflect the actual stress and strain characteristics of soil samples.In this paper,the image-based 3D reconstruction technology is applied to the geotechnical triaxial test.The non-contact3 D measurement of the deformation of the triaxial soil sample is carried out through the image-based 3D reconstruction technology,and a new method is sought for the accurate measurement of soil sample deformation.Measurement methods.The specific research results are as follows:(1)The basic principles of image-based 3D reconstruction technology are discussed.When image measurement technology is applied to geotechnical triaxial tests,the refraction effect caused by air,plexiglass pressure chamber,and water will cause image measurement errors.Combining the common refraction correction methods,a three-dimensional refraction model based on ray tracing is established to correct the refraction error,and the deformation information of the soil sample is extracted by eliminating the three-dimensional model of the soil sample after refraction.(2)Through the accuracy verification test in the air and the simulation test of the triaxial test,the measurement accuracy of the image measurement technology in the triaxial test is discussed,and the factors affecting the measurement accuracy are discussed.The test results show that: the measurement accuracy of image measurement technology in the air is 0.02 mm;the use of a three-dimensional refraction model based on ray tracing can effectively reduce the image measurement error caused by refraction.The corrected average error of the axial measurement is 0.144 mm.The average error of the direction measurement is 0.140 mm;it basically meets the requirements of the three-axis test;the camera imaging error and the three-dimensional refraction correction error are the main factors that cause the measurement error.The measurement accuracy of the image measurement technology in the geotechnical triaxial test is greatly improved through measures such as camera correction,supplementary light processing,and optimization of the three-dimensional refraction correction model.(3)In the unconsolidated and undrained triaxial shear test,the conventional measurement method and the image measurement method are used to measure the axial and radial deformation of the soil sample.The analysis and comparison of the two measurement methods show that: conventional measurement The overall deformation measured by the method does not reflect the actual deformation of the soil sample well.With the help of image-based 3D reconstruction technology,a three-dimensional model of the soil sample is constructed,and the deformation information of the soil sample is extracted to more truly reflect the uneven deformation of the soil sample.Such more realistic stress-strain characteristics.(4)The shear failure process of the triaxial soil sample is tracked through the image measurement three-dimensional reconstruction technology.The test results show that the shear failure of the soil sample develops and evolves from the local strain of the soil sample,and finally forms a certain direction and width through the soil.Such uneven deformation zone.The image measurement technology is used to measure the local deformation of the soil sample,which overcomes the local deformation measurement of the soil sample that is difficult to achieve in the conventional triaxial test,and provides a new measurement method for the localization study of the soil sample.