The Error Correction And Data Processing Of Digital Image Processing Method Based On The Tri-axial Test

Tri-axial test plays an important role in soil mechanics and geotechnical engineering. As one of the most important instrument for soil test, tri-axial apparatus has been playing an essential role in the development of soil mechanics. However, there are many limitations and shortages in specimen deformation measurement in tri-axial test. With application of digital image processing technique, some of these limitations and shortages can be overcome and lead to a new, more reasonable and more effective method in specimen deformation measurement.Compared with the traditional method, the digital image processing method has many advantages in measuring the deformation of soil specimen in tri-axial test, such as higher accuracy, non-contact measuring process; it can also record the images of soil specimen in deformation which can be used to re-analysis after test.This paper analysis the resources of measurement error and focus on camera distortion and the measurement error caused by environment and so on. Correct the camera distortion with two different methods and compare them. Also lead-in the edge recognition technology in the corner point recognition's measurement system to work out the center of the cylindrical sample which changes as time go.It also analysis the cylindrical sample imaging characteristics and gives the idea to solve the surface deformation field that is:first, it introduces a pixel equivalent to the processing, then calculates circle deformation or horizontal deformation, and analysis the relationship of circle deformation or horizontal deformation and dial deformation, thus calculate dial deformation.Because the arc length of specimen does not change with the cameral location, the paper successfully make mosaic of two images independent photographed by single cameras. And also discuss the situation of corner point missing and the images deflection then mend the missing cornet point and rotate the image it achieves the full surface deformation field of specimen.At the same time this paper introduces the digital imaging processing technique and the data-process soft which are developed by geotechnical and environmental mechanics laboratory of Dalian University of Technology.