Anisotropic properties of compacted silty clay
Laboratory permeability tests using a flexible-wall permeameter were performed to determine the effect of compaction energy on the anisotropic ratio of the silty clay, which was obtained from the Athens wetland construction site in Athens, Ohio. Five different compaction energy levels from 9,900 to 25,000 lb-ft/ft ^3were used in this study. Using an impact compaction, vertically and horizontally compacted samples with a diameter of 2.8 in. (71.1 mm) were measured. The permeability test was constant head with saturation under back pressure and hydraulic gradient of 20. Five sets of unconfined compression tests were also conducted to determine the stress-strain relationship of the soil. Both directional samples with a 2.0-in. (51 mm) diameter were measured. It was observed from the permeability tests that both vertical and horizontal permeabilities were greatly influenced by a change in compaction energy. Vertical permeability decreased from 1.35×10 -5cm/s to 1.2×10 -7cm/s, whereas the horizontal permeability also decreased from 1.32×10 -4cm/s to 4.33×10 -7cm/s, about a 300-fold decrease as the compaction energy increased from 9,900 to 25,000 lb-ft/ft ^3. Anisotropic ratio of the soil tended to be decreased with an increase in compaction energy. The range of the ratio was from 9.74 for the compaction energy of 9,900 lb-ft/ft ^3to 3.64 for 25,000 lb-ft/ft ^3. This anisotropy may be resulted from the effect of the flow pattern at the interface between layers and the particle orientation theory. In the unconfined compression tests, vertical samples showed a larger ultimate shear strength and a flatter stress-strain curve at the low stress compared to horizontal samples. As the compaction energy increased, the ultimate shear strength of vertical samples increased from 25.87 kPa to 43.37 kPa, and horizontal samples increased from 25 kPa to 40.48 kPa. Also, higher modulus of elasticity, E, of the horizontal samples was 1 to 1.8 times higher than vertical samples.
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:anisotropic ratio hydraulic gradient silty clay
Date of Publication:01/01/1996