Anisotropic features of natural Teguline clay

Abstract

In general, due to their geological formation by deposition, natural stiff clays exhibit anisotropic thermo-hydro-mechanical behaviour. This behaviour is important to be considered in geological and geo-environmental engineering. In this study, natural stiff Teguline clay was extracted at different depths and the thermal conductivity, compressibility and hydraulic conductivity were determined on samples along various orientations with respect to the bedding plane. Significant thermal and hydraulic conductivity anisotropies were evidenced with higher values along the bedding plane, indicating that both heat and water transfers preferentially occurred along the direction parallel to the bedding plane. Moreover, the compression index in the horizontal direction were found lower than in the vertical direction, while opposite phenomenon was observed for the yield stress. The degrees of thermal conductivity anisotropy ηΤ, compression index anisotropy ηCc1, yield stress anisotropy ησ'y and hydraulic conductivity anisotropy ηk1 were found comparable, indicating that bedding is a good indicator of the inherent thermo-hydro-mechanical anisotropy for natural stiff clays. Upon loading in oedometer after the yield stress, the inherent anisotropy changed: for the vertical sample (loading direction normal to the bedding plane), loading led to more and more anisotropy, while for the horizontal sample (loading direction parallel to the bedding plane), the inherent anisotropy disappeared first; then, the induced anisotropy was developed. These findings provided useful information for analyzing the thermo-hydro-mechanical anisotropy of natural soils in geotechnical and geo-environmental engineering.