Photogrammetric technique applied to triaxial test can realize the non-contact measurement of soil sample deformation,however the measurement accuracy of the method is susceptible to the refraction influence of different media.To solve the problem,firstly,the photogrammetric method is verified to have high measurement accuracy without the influence of refraction by measuring the distance of the plane artificial coding points and the axial and radial lengths of the rigid cylinders in air;but the light will be affected by the refraction of different mediums,such as the air,the organic glass cover and water in the pressure chamber,which results in a large measurement error.In order to eliminate the effect of refraction,the three-dimensional refraction error correction model is applied to the triaxial test of saturated mixed soil,and the test results are analyzed for accuracy from axial and radial directions.The test results show that:1)the effect of refraction amplification on the axial measurement accuracy of triaxial soil samples is very small and negligible,but the effect on the radial measurement is larger,which needs to be corrected by the refraction error;2)after the error correction,the absolute and relative errors of the radial measurements of triaxial soil samples are 0.120 mm and 0.59%,respectively,indicating that the refraction error correction model can improve the accuracy of triaxial photogrammetry.
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