Summary

Laboratory experiments are described in which soil and groundwater regimes approximating those of hot arid areas have been modelled. The motions of saline groundwater and the solution and precipitation of phases such as halite, gypsum and calcite in the capillary fringe have been studied. The non-woven permeable fabrics ‘Terram’ and ‘Filtram’ have been placed in the soil beds and it is shown that fabrics such as ‘Filtram’ are capable of preventing both the capillary rise of moisture and the downward penetration of water infiltrating from above. The lower surface of the fabric may act as a locus for mineral precipitation but crystalline phases have not been found growing into the pores of the fabric. The work is relevant to both horticultural and engineering applications of the fabrics and the first experiments have been followed by larger scale experiments, which are not yet complete, in which further details of the behaviour of permeable membranes in unsaturated soils are being studied, including their ability to protect building materials.

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