Part of a research program aimed at studying the advance of the wetting front and the development of swell during flow through a compacted, active clay is described. The study included tests on compacted soil columns tested both under laboratory conditions and under an increased acceleration field in a centrifuge. Special instrumentation was employed, including gamma ray scanning, high-speed photography, and moisture transducers. Test results indicate differences in the wetting process for soil compacted wet and dry of plastic limit. In the latter case, a sharp wetting front was observed, whose rate of advance was unaffected by the high suction in the soil. In the columns compacted wet of plastic limit, the wetting front was less sharp, and its advance was significantly affected by soil suction. In all cases, the coefficient of permeability dropped continuously following wetting. These observations led to a model for the process of flow through swelling soil in which flow advances through the large, inter-aggregate pores of the soil. As the aggregates become wet, theyswell, the pores close, and permeability decreases. This paper appears in transportation research record no. 1277, Modern geotechnical methods: instrumentation and vibratory hammers 1990.
Abstract