The compaction degree is one of the main control items for quality acceptance of filling engineering,the research shows that higher compaction degree has a significant effect on improving the mechanical properties of loess. In order to comprehensively and systematically analyze the influence of compaction on the shear properties of loess and better reveal the internal reasons for the improvement of the shear strength of loess by high pressure compaction,the shear properties and micro-structures of compacted loess in the Beiyuan area of Linxia City,Gansu Province were studied by means of triaxial shear test and scanning electron microscopy test based on four different compaction degrees. It is found that the stress-strain relation of the compacted loess satisfies hyperbolic form,and higher compaction degree has a significant effect on improving the shear strength and shear modulus of loess; Higher compaction improves the shear resistance of loess by changing the contact form between soil particles,which transforms gradually from edge contact and bracket to surface contact with the increase of compactness;Higher compaction improves the shear resistance by changing the characteristics and morphological distribution of soil pore size,showing a gradual increase of pore scale of micro and small pores with the increase of compaction,while the content of medium,large and extra large pores decreases,and the pore shape becomes relatively smooth.
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