Field-Scale Unsaturated Hydraulic Properties of Compacted and Uncompacted Earthen Covers

Abstract

Unsaturated hydraulic properties influence the field hydrology of engineered earthen covers. Field measured hydraulic properties of soils are recommended because they closely represent the field structure of the soil. This paper presents unsaturated hydraulic properties of two field scale test sections, composed of compacted vs. uncompacted clay. The unsaturated hydraulic properties were estimated using continuous measurements of water contents and matric suctions. The water contents and matric suctions were measured by sensors installed in the field test sections. The unsaturated hydraulic conductivities were estimated using the instantaneous profile method. The water content versus suction relationships for the two test sections showed significant differences at low suctions and the relationships were similar at higher suctions. The only difference between the test sections was the compaction state. The compacted clay test section had higher dry unit weight than the uncompacted clay test section. The uncompacted clay had greater volume of interclod voids (macropores). The differences in water content versus suction relationships at low suction could be because of macropores which empty out first and fill up last under unsaturated condition. At higher suctions, the relationships were similar because the flow is controlled by the micropores which existed in both test sections.