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Abstract A new technique for quantitative analysis of the orientation distribution of soil grains from SEM images，slope-aspect technique，was described in this paper. The pixels at the edge of the particles of SEM were abstracted by the method of slope analysis. Because the aspect values of the pixels at the edge of the particles are orthogonal to the orientation of the particles，the orientation characteristics of a SEM image of soil samples can be obtained by quantitatively analyzing the aspect of the pixels at the edge of the particles in SEM. Some quantitative analysis techniques，including rosette diagrams，index of anisotropy and main orientation angle were also used. Through some examples，the slope-aspect technique is proved to be an efficient technique in examining orientation patterns of clay or sand soil microstructure，and it can provide more reasonable rosette histogram，index of anisotropy and main orientation angle. It also shows that the results in low slop classes can not present the orientation characteristics of whole sample because of noise and algorithmic error. But aspect values of pixels with higher slope class on the boundaries of particles can well present the orientation pattern of soil samples.
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Received: 20 March 2009
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