EFFECT OF COMPACTION CONDITION ON STRENGTH, PERMEABILITY AND SHEAR MODULUS OF SANDY SILT AS EMBANKMENT MATERIAL

Abstract

 In order to reveal change in mechanical characteristics of soil due to difference of compaction condition, a series of laboratory tests on sandy silt which was used as embankment material are performed. In those tests, shear strength, shear modulus and coefficient of permeability are measured under the various compaction conditions. Firstly, it is shown that shear strength of the specimen prepared at the optimum water content is higher than these of drier and wetter condition at the lower confining pressure. On the other hand, it is found that vertical permeability and shear modulus of the specimens depend on the degree of compaction and water content at compaction. At the same compaction energy, the permeability and the shear modulus show the minimum and maximum values at the wetter situation. Those experimental facts are reflected to the change in the soil fabric of specimen due to the compaction. In order to reveal the correlations among the shear strength, shear modulus and permeability coefficient prepared at the various compaction conditions are graphically-illustrated. Those explain that (1) increase of the permeability coefficient makes the strength reduction, (2) the shear strength increase in almost directly proportion to the shear modulus of compacted specimen. In this study, it is attempted to express the patterns for fabrics of compacted soil. At the compaction under drier condition, the finer particles generally stand up and coarse particles lay horizontally. By contrast, under wetter condition, the finer particles lay horizontally and coarse particles almost stand up. Those may explain reasonably the effects of condition of compaction on the mechanical properties.