Investigation on Unsaturated Hydraulic Conductivity with Nuclear Magnetic Resonance Technology and Instantaneous Profile Method

Resumo

Determination of the transient water content distribution in porous materials with both swiftness and accuracy during the unsaturated permeability tests seems somewhat difficult. The traditional water content measurement methods using relatively large probes generally, which exhibit inconvenience and inefficiency to some extent, do unavoidably some destructive exercises on the specimens. In this paper, the saturation (water content) distribution in a white Portland cement specimen that had a dry density of 1.35 g/cm³ was measured swiftly and non-destructively by employing the nuclear magnetic resonance (NMR) technology. Unsaturated hydraulic conductivities of the white Portland cement specimen corresponding to different suctions were obtained using the instantaneous profile (IP) method. It appears from the obtained results that under a dry density of 1.35 g/cm³, the unsaturated hydraulic conductivity of the white Portland cement varies between 10⁻¹¹ and 10⁻⁷ m/s; with the decreasing suction, the hydraulic conductivity increases mildly and sharply, respectively, in the high and modest suction ranges, and stalls in the low suction range; and it enjoys both efficiency and preciousness to measure the water content distribution in the specimen with the NMR technology.