2017 Volume 73 Issue 1 Pages 39-44
It has been reported that tsunami deposits generated by the Great East Japan Earthquake are causing soil contamination. Unsaturated seepage flow in contaminated soil can cause groundwater contamination. Unsaturated hydraulic conductivity is an important indicator that can be used to predict groundwater contamination. This paper proposes an in-situ unsaturated permeability test method. The proposed method makes it possible to estimate the unsaturation characteristic parameters and saturated hydraulic conductivity in the van Genuchten equation through simple measurements. In the proposed test method, the volumetric water content of the soil is measured by infiltrating water from the ground surface, and the water pressure can be changed arbitrarily. Since the water pressure can be set at up to 100 kPa, efficient testing of low-permeability ground is possible. By increasing water pressure incrementally, unsaturation characteristic parameters can be estimated with higher accuracy. These parameters can also be estimated easily by measuring the initial suction and volumetric water content of the soil because parameter n in the van Genuchten equation represents the curvature of the unsaturated characteristic curve and parameter α represents a point of inflection of the curve. Measurement by this test method, however, is difficult if the volumetric water content of the soil being measured is close to that of saturated soil.