Microscopic changes in soil aggregates during permeablity tests.

Abstract

A method is described for examining soil material with the microscope during permeability tests and for recording the changes in the soil structure by macrophotographs. The permeability changes of a pack of calcium-saturated aggregates subjected to a sequence of permeating solutions is explained almost solely on the basis of soil swelling. An explanation of the cause of the three phases of permeability commonly observed in permeability tests on soils is given. No significant degree of microerosion was observed during permeation of the soil pack, in spite of the fact that a high percentage of the aggregates used was unstable in water. When solutions containing only sodium chloride were used, the aggregates swelled and finally merged with each other in a complete collapse of structure.