The effect of wall lubricants and column confinement on the infiltration behaviour of a swelling soil in the laboratory

Abstract

The effect of wall lubrication in reducing the frictional drag between soil particles and the retaining wall of a column during infiltration into a swelling soil was studied for five lubricants, polybutene oil (RP7), fluorocarbon telomer (F.E.T.), silicone mold release, silicone rubber liners, and a block polymer surfactant. Only silicone rubber liners resulted in a significantly higher infiltration capacity. However, this result could be attributed to imperfect adherence of the liner to the wall of the column which allowed some lateral swelling of the soil during infiltration, rather than to a reduction in interaction between the walls and the swelling soil. By contrast, the use of expanding thin-walled cylindrical rubber sleeving for infiltration columns greatly increased the infiltration capacity of the swelling soil above that observed in the rigid tubes. The effect of column diameter on infiltration into the expanding columns was similar to that observed in rigid columns. The relevance of these findings to the design of laboratory infiltration experiments attempting to reproduce field behaviour of swelling soils is discussed.