Hydraulic anisotropy behavior of compacted soil

Analysis of water flow in unsaturated soils is very important in many geotechnical applications. Many seepage analyses commonly assume soils are isotropic in order to simplify the numerical analyses. However, the hydraulic anisotropy behavior of a soil in the field can be a significant factor in affecting water flow within soil layer during rainfall. Previous research has not studied comprehensively the hydraulic anisotropy behavior of unsaturated soil. In this study, laboratory experiments were carried out on horizontal-layering (HL) and vertical-layering (VL) compacted soil specimens. The scope of the study included determination of soilwater characteristic curve using Tempe cell and determination of saturated permeability using conventional triaxial cell. The results indicated that hydraulic anisotropy can be associated with the ratio of the equalization time during SWCC tests between HL and VL specimens. The soil specimen compacted at wet of optimum has a higher hydraulic anisotropy as compared to that compacted at dry of optimum. In addition, the soil with a higher percentage of fine particles has a lower hydraulic anisotropy as compared to that with a lower percentage of fine particles.